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* [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
@ 2023-08-28  8:04 Alessandro Carminati (Red Hat)
  2023-08-29 14:51 ` Francis Laniel
                   ` (4 more replies)
  0 siblings, 5 replies; 16+ messages in thread
From: Alessandro Carminati (Red Hat) @ 2023-08-28  8:04 UTC (permalink / raw)
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Masahiro Yamada, Luis Chamberlain,
	Nathan Chancellor, Nick Desaulniers, Nicolas Schier,
	Alexander Lobakin, Nick Alcock, Kris Van Hees, Eugene Loh,
	Francis Laniel, Viktor Malik, Alessandro Carminati, linux-kbuild,
	linux-kernel, linux-trace-kernel, live-patching

From: Alessandro Carminati <alessandro.carminati@gmail.com>

It is not uncommon for drivers or modules related to similar peripherals
to have symbols with the exact same name.
While this is not a problem for the kernel's binary itself, it becomes an
issue when attempting to trace or probe specific functions using
infrastructure like ftrace or kprobe.

The tracing subsystem relies on the `nm -n vmlinux` output, which provides
symbol information from the kernel's ELF binary. However, when multiple
symbols share the same name, the standard nm output does not differentiate
between them. This can lead to confusion and difficulty when trying to
probe the intended symbol.

 ~ # cat /proc/kallsyms | grep " name_show"
 ffffffff8c4f76d0 t name_show
 ffffffff8c9cccb0 t name_show
 ffffffff8cb0ac20 t name_show
 ffffffff8cc728c0 t name_show
 ffffffff8ce0efd0 t name_show
 ffffffff8ce126c0 t name_show
 ffffffff8ce1dd20 t name_show
 ffffffff8ce24e70 t name_show
 ffffffff8d1104c0 t name_show
 ffffffff8d1fe480 t name_show

**kas_alias** addresses this challenge by extending the symbol names with
unique suffixes during the kernel build process.
The newly created aliases for these duplicated symbols are unique names
that can be fed to the ftracefs interface. By doing so, it enables
previously unreachable symbols to be probed.

 ~ # cat /proc/kallsyms | grep " name_show"
 ffffffff974f76d0 t name_show
 ffffffff974f76d0 t name_show__alias__6340
 ffffffff979cccb0 t name_show
 ffffffff979cccb0 t name_show__alias__6341
 ffffffff97b0ac20 t name_show
 ffffffff97b0ac20 t name_show__alias__6342
 ffffffff97c728c0 t name_show
 ffffffff97c728c0 t name_show__alias__6343
 ffffffff97e0efd0 t name_show
 ffffffff97e0efd0 t name_show__alias__6344
 ffffffff97e126c0 t name_show
 ffffffff97e126c0 t name_show__alias__6345
 ffffffff97e1dd20 t name_show
 ffffffff97e1dd20 t name_show__alias__6346
 ffffffff97e24e70 t name_show
 ffffffff97e24e70 t name_show__alias__6347
 ffffffff981104c0 t name_show
 ffffffff981104c0 t name_show__alias__6348
 ffffffff981fe480 t name_show
 ffffffff981fe480 t name_show__alias__6349
 ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
 > >/sys/kernel/tracing/kprobe_events
 ~ # cat /sys/kernel/tracing/kprobe_events
 p:kprobes/evnt1 name_show__alias__6349

Changes from v1:
- Integrated changes requested by Masami to exclude symbols with prefixes
  "_cfi" and "_pfx".
- Introduced a small framework to handle patterns that need to be excluded
  from the alias production.
- Excluded other symbols using the framework.
- Introduced the ability to discriminate between text and data symbols.
- Added two new config symbols in this version: CONFIG_KALLSYMS_ALIAS_DATA,
  which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
  excludes all filters and provides an alias for each duplicated symbol.

https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gmail.com/

Changes from v2:
- Alias tags are created by querying DWARF information from the vmlinux.
- The filename + line number is normalized and appended to the original name.
- The tag begins with '@' to indicate the symbol source.
- Not a change, but worth mentioning, since the alias is added to the existing
  list, the old duplicated name is preserved, and the livepatch way of dealing
  with duplicates is maintained.
- Acknowledging the existence of scenarios where inlined functions declared in
  header files may result in multiple copies due to compiler behavior, though
   it is not actionable as it does not pose an operational issue.
- Highlighting a single exception where the same name refers to different
  functions: the case of "compat_binfmt_elf.c," which directly includes
  "binfmt_elf.c" producing identical function copies in two separate
  modules.

sample from new v3

 ~ # cat /proc/kallsyms | grep gic_mask_irq
 ffffd0b03c04dae4 t gic_mask_irq
 ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
 ffffd0b03c050960 t gic_mask_irq
 ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
 ~ #

https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gmail.com/

Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
---
 init/Kconfig                        |  36 ++++
 scripts/Makefile                    |   4 +
 scripts/kas_alias/Makefile          |   4 +
 scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
 scripts/kas_alias/a2l.h             |  32 ++++
 scripts/kas_alias/duplicates_list.c |  70 ++++++++
 scripts/kas_alias/duplicates_list.h |  15 ++
 scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
 scripts/kas_alias/item_list.h       |  26 +++
 scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
 scripts/link-vmlinux.sh             |  11 +-
 11 files changed, 910 insertions(+), 3 deletions(-)
 create mode 100644 scripts/kas_alias/Makefile
 create mode 100644 scripts/kas_alias/a2l.c
 create mode 100644 scripts/kas_alias/a2l.h
 create mode 100644 scripts/kas_alias/duplicates_list.c
 create mode 100644 scripts/kas_alias/duplicates_list.h
 create mode 100644 scripts/kas_alias/item_list.c
 create mode 100644 scripts/kas_alias/item_list.h
 create mode 100644 scripts/kas_alias/kas_alias.c

diff --git a/init/Kconfig b/init/Kconfig
index f7f65af4ee12..bc69fcd9cbc8 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1737,6 +1737,42 @@ config KALLSYMS_BASE_RELATIVE
 	  time constants, and no relocation pass is required at runtime to fix
 	  up the entries based on the runtime load address of the kernel.
 
+config KALLSYMS_ALIAS
+	bool "Produces alias for duplicated symbols" if EXPERT
+	depends on KALLSYMS && (DEBUG_INFO_DWARF4 || DEBUG_INFO_DWARF5)
+	help
+	  It is not uncommon for drivers or modules related to similar
+	  peripherals to have symbols with the exact same name.
+	  While this is not a problem for the kernel's binary itself, it
+	  becomes an issue when attempting to trace or probe specific
+	  functions using infrastructure like ftrace or kprobe.
+
+	  This option addresses this challenge by extending the symbol names
+	  with unique suffixes during the kernel build process.
+	  The newly created aliases for these duplicated symbols are unique
+	  names that can be fed to the ftrace sysfs interface. By doing so, it
+	  enables previously unreachable symbols to be probed.
+
+config CONFIG_KALLSYMS_ALIAS_DATA
+	bool "Produces alias also for data"
+	depends on KALLSYMS_ALIAS
+	help
+	  Sometimes it can be useful to refer to data. In live patch scenarios,
+	  you may find yourself needing to use symbols that are shared with
+	  other functions. Since symbols face the same issue as functions, this
+	  option allows you to create aliases for data as well.
+
+config CONFIG_KALLSYMS_ALIAS_DATA_ALL
+	bool "Removes all filter when producing data alias"
+	depends on CONFIG_KALLSYMS_ALIAS_DATA
+	help
+	  When selecting data aliases, not all symbols are included in the set
+	  This is because many symbols are unlikely to be used. If you choose
+	  to have an alias for all data symbols, be aware that it will
+	  significantly increase the size.
+
+	  If unsure, say N.
+
 # end of the "standard kernel features (expert users)" menu
 
 # syscall, maps, verifier
diff --git a/scripts/Makefile b/scripts/Makefile
index 32b6ba722728..65fafe17cfe5 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -49,3 +49,7 @@ subdir-$(CONFIG_SECURITY_SELINUX) += selinux
 
 # Let clean descend into subdirs
 subdir-	+= basic dtc gdb kconfig mod
+
+# KALLSyms alias
+subdir-$(CONFIG_KALLSYMS_ALIAS) += kas_alias
+
diff --git a/scripts/kas_alias/Makefile b/scripts/kas_alias/Makefile
new file mode 100644
index 000000000000..e1fde69232b4
--- /dev/null
+++ b/scripts/kas_alias/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+hostprogs-always-$(CONFIG_KALLSYMS_ALIAS)    += kas_alias
+
+kas_alias-objs        := duplicates_list.o item_list.o kas_alias.o a2l.o
diff --git a/scripts/kas_alias/a2l.c b/scripts/kas_alias/a2l.c
new file mode 100644
index 000000000000..a9692ac30180
--- /dev/null
+++ b/scripts/kas_alias/a2l.c
@@ -0,0 +1,268 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <string.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "a2l.h"
+
+int addr2line_pid = -1;
+int a2l_in[2];
+int a2l_out[2];
+char line[MAX_BUF];
+char vmlinux_path[MAX_BUF];
+char addr2line_cmd[MAX_CMD_LEN];
+FILE *a2l_stdin, *a2l_stdout;
+
+static char *normalize_path(const char *input_path, char *output_path)
+{
+	char *prev_token = NULL;
+	char *delimiter = "/";
+	char inbuf[MAX_BUF];
+	char *token;
+	char *pos;
+
+	memset(inbuf, 0, MAX_BUF);
+	*output_path = '\0';
+	strncpy(inbuf, input_path, MAX_BUF);
+	if (!input_path || !output_path || strlen(input_path) == 0)
+		return NULL;
+
+	token = strtok(inbuf, delimiter);
+	while (token) {
+		if (strcmp(token, "..") == 0 && prev_token) {
+			pos = strrchr(output_path, '/');
+			if (pos)
+				*pos = '\0';
+
+		} else if (strcmp(token, ".") != 0) {
+			strcat(output_path, "/");
+			strcat(output_path, token);
+		}
+
+		prev_token = token;
+		token = strtok(NULL, delimiter);
+	}
+
+	return output_path;
+}
+
+static void path_of(const char *full_path, char *path)
+{
+	const char *last_slash = strrchr(full_path, '/');
+	size_t path_length;
+	char cwd[MAX_BUF];
+
+	if (!last_slash) {
+		if (getcwd(cwd, sizeof(cwd)))
+			strcpy(path, cwd);
+		else
+			strcpy(path, ".");
+	} else {
+		path_length = last_slash - full_path;
+		strncpy(path, full_path, path_length);
+		path[path_length] = '\0';
+	}
+}
+
+static bool file_exists(const char *file_path)
+{
+	FILE *file;
+
+	file = fopen(file_path, "r");
+	if (file) {
+		fclose(file);
+		return true;
+	}
+	return false;
+}
+
+int addr2line_init(const char *cmd, const char *vmlinux)
+{
+	if ((!file_exists(cmd)) || (!file_exists(vmlinux))) {
+		printf("file not found\n");
+		return 0;
+		}
+
+	path_of(vmlinux, vmlinux_path);
+	if (pipe(a2l_in) == -1) {
+		printf("Failed to create pipe\n");
+		return 0;
+	}
+
+	if (pipe(a2l_out) == -1) {
+		printf("Failed to create pipe\n");
+		return 0;
+	}
+
+	addr2line_pid = fork();
+	if (addr2line_pid == -1) {
+		printf("Failed to fork process\n");
+		close(a2l_in[P_READ]);
+		close(a2l_in[P_WRITE]);
+		close(a2l_out[P_READ]);
+		close(a2l_out[P_WRITE]);
+		return 0;
+	}
+
+	if (addr2line_pid == 0) {
+		dup2(a2l_in[P_READ], 0);
+		dup2(a2l_out[P_WRITE], 1);
+		close(a2l_in[P_WRITE]);
+		close(a2l_out[P_READ]);
+
+		execlp(cmd, cmd, ADDR2LINE_ARGS, vmlinux, NULL);
+
+		printf("Failed to execute addr2line command\n");
+		exit(1);
+	} else {
+		close(a2l_in[P_READ]);
+		close(a2l_out[P_WRITE]);
+	}
+
+	a2l_stdin = fdopen(a2l_in[P_WRITE], "w");
+	if (!a2l_stdin) {
+		printf("Failed to open pipe a2l_in\n");
+		return 0;
+	}
+
+	a2l_stdout = fdopen(a2l_out[P_READ], "r");
+	if (!a2l_stdout) {
+		printf("Failed to open pipe a2l_out\n");
+		fclose(a2l_stdin);
+		return 0;
+	}
+
+	return 1;
+}
+
+const char *remove_subdir(const char *home, const char *f_path)
+{
+	int i = 0;
+
+	while (*(home + i) == *(f_path + i))
+		i++;
+
+	return (strlen(home) != i) ? NULL : f_path + i;
+}
+
+char *addr2line_get_lines(uint64_t address)
+{
+	char buf[MAX_BUF];
+
+	fprintf(a2l_stdin, "%08lx\n", address);
+	fflush(a2l_stdin);
+
+	if (!fgets(line, sizeof(line), a2l_stdout)) {
+		printf("Failed to read lines from addr2line\n");
+		return NULL;
+	}
+
+	if (!fgets(line, sizeof(line), a2l_stdout)) {
+		printf("Failed to read lines from addr2line\n");
+		return NULL;
+	}
+
+	line[strcspn(line, "\n")] = '\0';
+	strncpy(buf, line, MAX_BUF);
+	return normalize_path(buf, line);
+}
+
+int addr2line_cleanup(void)
+{
+	int status;
+
+	if (addr2line_pid != -1) {
+		kill(addr2line_pid, SIGKILL);
+		waitpid(addr2line_pid, &status, 0);
+		fclose(a2l_stdin);
+		fclose(a2l_stdout);
+		addr2line_pid = -1;
+	}
+
+	return 1;
+}
+
+static char *find_executable(const char *command)
+{
+	char *path_env = getenv("PATH");
+	char *executable_path;
+	char *path_copy;
+	char *path;
+	int n;
+
+	if (!path_env)
+		return NULL;
+
+	path_copy = strdup(path_env);
+	if (!path_copy)
+		return NULL;
+
+	path = strtok(path_copy, ":");
+	while (path) {
+		n = snprintf(0, 0, "%s/%s", path, command);
+		executable_path = (char *)malloc(n + 1);
+		snprintf(executable_path, n + 1, "%s/%s", path, command);
+		if (access(executable_path, X_OK) == 0) {
+			free(path_copy);
+			return executable_path;
+		}
+
+	path = strtok(NULL, ":");
+	free(executable_path);
+	executable_path = NULL;
+	}
+
+	free(path_copy);
+	if (executable_path)
+		free(executable_path);
+	return NULL;
+}
+
+const char *get_addr2line(int mode)
+{
+	char *buf = "";
+
+	switch (mode) {
+	case A2L_CROSS:
+		buf = getenv("CROSS_COMPILE");
+		memcpy(addr2line_cmd, buf, strlen(buf));
+	case A2L_DEFAULT:
+		memcpy(addr2line_cmd + strlen(buf), ADDR2LINE, strlen(ADDR2LINE));
+		buf = find_executable(addr2line_cmd);
+		if (buf) {
+			memcpy(addr2line_cmd, buf, strlen(buf));
+			free(buf);
+		}
+		return addr2line_cmd;
+	case A2L_LLVM:
+	default:
+		return NULL;
+	}
+}
+
+char *get_vmlinux(char *input)
+{
+	const char *match_string1 = ".syms";
+	const char *match_string2 = ".tmp_vmlinux.kallsyms";
+	char *result = NULL;
+	char *match_pos;
+
+	match_pos = strstr(input, match_string1);
+	if (!match_pos)
+		return NULL;
+
+	match_pos = strstr(input, match_string2);
+	if (!match_pos)
+		return NULL;
+
+	result = strdup(input);
+	match_pos = strstr(result, match_string1);
+	*match_pos = '\0';
+	return result;
+}
diff --git a/scripts/kas_alias/a2l.h b/scripts/kas_alias/a2l.h
new file mode 100644
index 000000000000..ca6419229dde
--- /dev/null
+++ b/scripts/kas_alias/a2l.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef A2L_H
+#define A2L_H
+#include <stdint.h>
+
+#define ADDR2LINE "addr2line"
+#define ADDR2LINE_ARGS "-fe"
+//#define VMLINUX "vmlinux"
+#define MAX_BUF 4096
+#define MAX_CMD_LEN 256
+#define P_READ 0
+#define P_WRITE 1
+#define A2L_DEFAULT 1
+#define A2L_CROSS 2
+#define A2L_LLVM 3
+#define A2L_MAKE_VALUE 2
+
+extern int addr2line_pid;
+extern int a2l_in[2];
+extern int a2l_out[2];
+extern char line[MAX_BUF];
+extern char vmlinux_path[MAX_BUF];
+extern char addr2line_cmd[MAX_CMD_LEN];
+
+int addr2line_init(const char *cmd, const char *vmlinux);
+char *addr2line_get_lines(uint64_t address);
+int addr2line_cleanup(void);
+const char *remove_subdir(const char *home, const char *f_path);
+const char *get_addr2line(int mode);
+char *get_vmlinux(char *input);
+
+#endif
diff --git a/scripts/kas_alias/duplicates_list.c b/scripts/kas_alias/duplicates_list.c
new file mode 100644
index 000000000000..e7a3d2917937
--- /dev/null
+++ b/scripts/kas_alias/duplicates_list.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+#include "item_list.h"
+#include "duplicates_list.h"
+
+struct duplicate_item *find_duplicates(struct item *list)
+{
+	struct duplicate_item *current_duplicate = NULL;
+	struct duplicate_item *duplicates = NULL;
+	struct duplicate_item *new_duplicate;
+	struct item *current_item = list;
+	bool prev_was_duplicate = false;
+	struct item *prev_item = NULL;
+
+	while (current_item) {
+		if ((prev_item && (strcmp(current_item->symb_name, prev_item->symb_name) == 0)) ||
+		    prev_was_duplicate) {
+			if (!duplicates) {
+				duplicates = malloc(sizeof(struct duplicate_item));
+				if (!duplicates)
+					return NULL;
+
+				duplicates->original_item = prev_item;
+				duplicates->next = NULL;
+				current_duplicate = duplicates;
+			} else {
+				new_duplicate = malloc(sizeof(struct duplicate_item));
+				if (!new_duplicate) {
+					free_duplicates(&duplicates);
+					return NULL;
+				}
+
+				new_duplicate->original_item = prev_item;
+				new_duplicate->next = NULL;
+				current_duplicate->next = new_duplicate;
+				current_duplicate = new_duplicate;
+
+				if ((strcmp(current_item->symb_name, prev_item->symb_name) != 0) &&
+				    (prev_was_duplicate))
+					prev_was_duplicate = false;
+				else
+					prev_was_duplicate = true;
+			}
+		}
+
+		prev_item = current_item;
+		current_item = current_item->next;
+	}
+
+	return duplicates;
+}
+
+void free_duplicates(struct duplicate_item **duplicates)
+{
+	struct duplicate_item *duplicates_iterator = *duplicates;
+	struct duplicate_item *app;
+
+	while (duplicates_iterator) {
+		app = duplicates_iterator;
+		duplicates_iterator = duplicates_iterator->next;
+		free(app);
+	}
+
+	*duplicates = NULL;
+}
diff --git a/scripts/kas_alias/duplicates_list.h b/scripts/kas_alias/duplicates_list.h
new file mode 100644
index 000000000000..76aa73e584bc
--- /dev/null
+++ b/scripts/kas_alias/duplicates_list.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef DUPLICATES_LIST_H
+#define DUPLICATES_LIST_H
+
+#include "item_list.h"
+
+struct duplicate_item {
+	struct item *original_item;
+	struct duplicate_item *next;
+};
+
+struct duplicate_item *find_duplicates(struct item *list);
+void free_duplicates(struct duplicate_item **duplicates);
+
+#endif
diff --git a/scripts/kas_alias/item_list.c b/scripts/kas_alias/item_list.c
new file mode 100644
index 000000000000..48f2e525592a
--- /dev/null
+++ b/scripts/kas_alias/item_list.c
@@ -0,0 +1,230 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdbool.h>
+#include <assert.h>
+#include "item_list.h"
+
+#define CHECK_ORDER_BY_ADDRESS(sort_by, current, temp, op) \
+	((sort_by) == BY_ADDRESS && (current)->addr op (temp)->addr)
+#define CHECK_ORDER_BY_NAME(sort_by, current, temp, op) \
+	((sort_by) == BY_NAME && strcmp((current)->symb_name, (temp)->symb_name) op 0)
+
+struct item *list_index[96] = {0};
+
+void build_index(struct item *list)
+{
+	char current_first_letter = ' ';
+	struct item *current = list;
+
+	while (current) {
+		if (current->symb_name[0] != current_first_letter) {
+			current_first_letter = current->symb_name[0];
+			list_index[current_first_letter - 32] = current;
+		}
+		current = current->next;
+	}
+}
+
+struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr)
+{
+	struct item *new_item;
+	struct item *current;
+
+	new_item = malloc(sizeof(struct item));
+	if (!new_item)
+		return NULL;
+
+	strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
+	new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
+	new_item->addr = addr;
+	new_item->stype = stype;
+	new_item->next = NULL;
+
+	if (!(*list)) {
+		*list = new_item;
+	} else {
+		current = *list;
+		while (current->next)
+			current = current->next;
+
+		current->next = new_item;
+	}
+	return new_item;
+}
+
+void sort_list(struct item **list, int sort_by)
+{
+	struct item *current = *list;
+	struct item *sorted = NULL;
+	struct item *next_item;
+	struct item *temp;
+
+	if (!(*list) || !((*list)->next))
+		return;
+
+	while (current) {
+		next_item = current->next;
+		if (!sorted ||
+		    (CHECK_ORDER_BY_ADDRESS(sort_by, current, sorted, <) ||
+		    CHECK_ORDER_BY_NAME(sort_by, current, sorted, >=))) {
+			current->next = sorted;
+			sorted = current;
+		} else {
+			temp = sorted;
+			while (temp->next &&
+			       (CHECK_ORDER_BY_ADDRESS(sort_by, current, temp->next, >=) ||
+			       CHECK_ORDER_BY_NAME(sort_by, current, temp->next, >=)))
+				temp = temp->next;
+
+			current->next = temp->next;
+			temp->next = current;
+		}
+		current = next_item;
+	}
+
+	*list = sorted;
+}
+
+struct item *merge(struct item *left, struct item *right, int sort_by)
+{
+	struct item *current = NULL;
+	struct item *result = NULL;
+
+	if (!left)
+		return right;
+	if (!right)
+		return left;
+
+	if (sort_by == BY_NAME) {
+		if (strcmp(left->symb_name, right->symb_name) <= 0) {
+			result = left;
+			left = left->next;
+		} else {
+			result = right;
+			right = right->next;
+		}
+	} else {
+		if (sort_by == BY_ADDRESS) {
+			if (left->addr <= right->addr) {
+				result = left;
+				left = left->next;
+			} else {
+				result = right;
+				right = right->next;
+			}
+		}
+	}
+
+	current = result;
+
+	while (left && right) {
+		if (sort_by == BY_NAME) {
+			if (strcmp(left->symb_name, right->symb_name) <= 0) {
+				current->next = left;
+				left = left->next;
+			} else {
+				current->next = right;
+				right = right->next;
+			}
+		} else {
+			if (sort_by == BY_ADDRESS) {
+				if (left->addr <= right->addr) {
+					current->next = left;
+					left = left->next;
+				} else {
+					current->next = right;
+					right = right->next;
+				}
+			}
+		}
+
+		current = current->next;
+	}
+
+	if (left) {
+		current->next = left;
+	} else {
+		if (right)
+			current->next = right;
+	}
+
+	return result;
+}
+
+struct item *merge_sort(struct item *head, int sort_by)
+{
+	struct item *right;
+	struct item *slow;
+	struct item *fast;
+	struct item *left;
+
+	if (!head || !head->next)
+		return head;
+
+	slow = head;
+	fast = head->next;
+
+	while (fast && fast->next) {
+		slow = slow->next;
+		fast = fast->next->next;
+	}
+
+	left = head;
+	right = slow->next;
+	slow->next = NULL;
+
+	left = merge_sort(left, sort_by);
+	right = merge_sort(right, sort_by);
+
+	return merge(left, right, sort_by);
+}
+
+void sort_list_m(struct item **head, int sort_by)
+{
+	if (!(*head) || !((*head)->next))
+		return;
+
+	*head = merge_sort(*head, sort_by);
+}
+
+int insert_after(struct item *list, const uint64_t search_addr,
+		 const char *name, uint64_t addr, char stype)
+{
+	struct item *new_item;
+	struct item *current;
+	int ret = 0;
+
+	current = (list_index[name[0] - 32]) ? list_index[name[0] - 32] : list;
+	while (current) {
+		if (current->addr == search_addr) {
+			new_item = malloc(sizeof(struct item));
+			if (!new_item)
+				return ret;
+			strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
+			new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
+			new_item->addr = addr;
+			new_item->stype = stype;
+			new_item->next = current->next;
+			current->next = new_item;
+			ret = 1;
+			break;
+		}
+		current = current->next;
+	}
+	return ret;
+}
+
+void free_items(struct item **head)
+{
+	struct item *app, *item_iterator = *head;
+
+	while (item_iterator) {
+		app = item_iterator;
+		item_iterator = item_iterator->next;
+		free(app);
+	}
+	*head = NULL;
+}
diff --git a/scripts/kas_alias/item_list.h b/scripts/kas_alias/item_list.h
new file mode 100644
index 000000000000..b4891cb088ee
--- /dev/null
+++ b/scripts/kas_alias/item_list.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef ITEM_LIST_H
+#define ITEM_LIST_H
+#include <stdint.h>
+
+#define MAX_NAME_SIZE 256
+#define BY_ADDRESS 1
+#define BY_NAME 2
+
+struct item {
+	char		symb_name[MAX_NAME_SIZE];
+	uint64_t	addr;
+	char		stype;
+	struct item	*next;
+};
+
+void build_index(struct item *list);
+struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr);
+void sort_list(struct item **list, int sort_by);
+struct item *merge(struct item *left, struct item *right, int sort_by);
+struct item *merge_sort(struct item *head, int sort_by);
+void sort_list_m(struct item **head, int sort_by);
+int insert_after(struct item *list, const uint64_t search_addr,
+		 const char *name, uint64_t addr, char stype);
+void free_items(struct item **head);
+#endif
diff --git a/scripts/kas_alias/kas_alias.c b/scripts/kas_alias/kas_alias.c
new file mode 100644
index 000000000000..532aeb39f851
--- /dev/null
+++ b/scripts/kas_alias/kas_alias.c
@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdbool.h>
+#include <stdarg.h>
+#include <regex.h>
+
+#include "item_list.h"
+#include "duplicates_list.h"
+#include "a2l.h"
+
+#define SYMB_IS_TEXT(s) ((((s)->stype) == 't') ||  (((s)->stype) == 'T'))
+#define SYMB_IS_DATA(s) ((((s)->stype) == 'b') ||  (((s)->stype) == 'B') || \
+			 (((s)->stype) == 'd') ||  (((s)->stype) == 'D') || \
+			 (((s)->stype) == 'r') ||  (((s)->stype) == 'R'))
+#ifdef CONFIG_KALLSYMS_ALIAS_DATA
+#define SYMB_NEEDS_ALIAS(s) (SYMB_IS_TEXT(s) || SYMB_IS_DATA(s))
+#else
+#define SYMB_NEEDS_ALIAS(s) SYMB_IS_TEXT(s)
+#endif
+#define FNOMATCH 0
+#define FMATCH 1
+#define EREGEX 2
+
+const char *ignore_regex[] = {
+	"^__cfi_.*$",				// __cfi_ preamble
+#ifndef CONFIG_KALLSYMS_ALIAS_DATA_ALL
+	"^_*TRACE_SYSTEM.*$",
+	"^__already_done\\.[0-9]+$",		// Call a function once data
+	"^___tp_str\\.[0-9]+$",
+	"^___done\\.[0-9]+$",
+	"^__print_once\\.[0-9]+$",
+	"^_rs\\.[0-9]+$",
+	"^__compound_literal\\.[0-9]+$",
+	"^___once_key\\.[0-9]+$",
+	"^__func__\\.[0-9]+$",
+	"^__msg\\.[0-9]+$",
+	"^CSWTCH\\.[0-9]+$",
+	"^__flags\\.[0-9]+$",
+	"^__wkey.*$",
+	"^__mkey.*$",
+	"^__key.*$",
+#endif
+	"^__pfx_.*$"				// NOP-padding
+};
+
+int suffix_serial;
+
+static inline void verbose_msg(bool verbose, const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	if (verbose)
+		printf(fmt, args);
+
+	va_end(args);
+}
+
+static void create_suffix(const char *name, char *output_suffix)
+{
+	sprintf(output_suffix, "%s__alias__%d", name, suffix_serial++);
+}
+
+static void create_file_suffix(const char *name, uint64_t address, char *output_suffix, char *cwd)
+{
+	const char *f_path;
+	char *buf;
+	int i = 0;
+
+	buf = addr2line_get_lines(address);
+	f_path = remove_subdir(cwd, buf);
+	if (f_path) {
+		sprintf(output_suffix, "%s@%s", name, f_path);
+		while (*(output_suffix + i) != '\0') {
+			switch (*(output_suffix + i)) {
+			case '/':
+			case ':':
+			case '.':
+				*(output_suffix + i) = '_';
+				break;
+			default:
+			}
+		i++;
+		}
+	} else {
+		create_suffix(name, output_suffix);
+	}
+}
+
+static int filter_symbols(char *symbol, const char **ignore_list, int regex_no)
+{
+	regex_t regex;
+	int res, i;
+
+	for (i = 0; i < regex_no; i++) {
+		res = regcomp(&regex, ignore_list[i], REG_EXTENDED);
+		if (res)
+			return -EREGEX;
+
+		res = regexec(&regex, symbol, 0, NULL, 0);
+		regfree(&regex);
+		switch (res) {
+		case 0:
+			return FMATCH;
+		case REG_NOMATCH:
+			break;
+		default:
+			return -EREGEX;
+		}
+	}
+
+	return FNOMATCH;
+}
+
+int main(int argc, char *argv[])
+{
+	char t, sym_name[MAX_NAME_SIZE], new_name[MAX_NAME_SIZE + 15];
+	struct duplicate_item  *duplicate_iterator;
+	struct duplicate_item *duplicate;
+	struct item *head = {NULL};
+	bool need_2_process = true;
+	struct item *last = {NULL};
+	struct item  *current;
+	int verbose_mode = 0;
+	uint64_t address;
+	FILE *fp;
+	int res;
+
+	if (argc < 2 || argc > 3) {
+		printf("Usage: %s <nmfile> [-verbose]\n", argv[0]);
+		return 1;
+	}
+
+	if (argc == 3 && strcmp(argv[2], "-verbose") == 0)
+		verbose_mode = 1;
+
+	verbose_msg(verbose_mode, "Scanning nm data(%s)\n", argv[1]);
+
+	fp = fopen(argv[1], "r");
+	if (!fp) {
+		printf("Can't open input file.\n");
+		return 1;
+	}
+
+	if (!addr2line_init(get_addr2line(A2L_DEFAULT), get_vmlinux(argv[1])))
+		return 1;
+
+	while (fscanf(fp, "%lx %c %99s\n", &address, &t, sym_name) == 3) {
+		if (strstr(sym_name, "@_")) {
+			if (verbose_mode && need_2_process)
+				printf("Already processed\n");
+			need_2_process = false;
+			}
+		last = add_item(&last, sym_name, t, address);
+		if (!last) {
+			printf("Error in allocate memory\n");
+			free_items(&head);
+			return 1;
+		}
+
+		if (!head)
+			head = last;
+	}
+
+	fclose(fp);
+
+	if (need_2_process) {
+		verbose_msg(verbose_mode, "Sorting nm data\n");
+		sort_list_m(&head, BY_NAME);
+		verbose_msg(verbose_mode, "Scanning nm data for duplicates\n");
+		duplicate = find_duplicates(head);
+		if (!duplicate) {
+			printf("Error in duplicates list\n");
+			return 1;
+		}
+
+		verbose_msg(verbose_mode, "Applying suffixes\n");
+		build_index(head);
+		duplicate_iterator = duplicate;
+		while (duplicate_iterator) {
+			res = filter_symbols(duplicate_iterator->original_item->symb_name,
+					     ignore_regex, sizeof(ignore_regex) /
+					     sizeof(ignore_regex[0]));
+			if (res != FMATCH &&
+			    SYMB_NEEDS_ALIAS(duplicate_iterator->original_item)) {
+				if (res < 0)
+					return 1;
+
+				create_file_suffix(duplicate_iterator->original_item->symb_name,
+						   duplicate_iterator->original_item->addr,
+						   new_name, vmlinux_path);
+				if (!insert_after(head, duplicate_iterator->original_item->addr,
+						  new_name, duplicate_iterator->original_item->addr,
+						  duplicate_iterator->original_item->stype))
+					return 1;
+			}
+
+			duplicate_iterator = duplicate_iterator->next;
+		}
+
+		sort_list_m(&head, BY_ADDRESS);
+	}
+	current = head;
+	while (current) {
+		printf("%08lx %c %s\n", current->addr, current->stype, current->symb_name);
+		current = current->next;
+	}
+
+	free_items(&head);
+	free_duplicates(&duplicate);
+	addr2line_cleanup();
+	return 0;
+}
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index a432b171be82..cacf60b597ce 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -89,8 +89,9 @@ vmlinux_link()
 
 	ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
 
-	# The kallsyms linking does not need debug symbols included.
-	if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
+	# The kallsyms linking does not need debug symbols included, unless the KALLSYMS_ALIAS.
+	if [ ! is_enabled CONFIG_KALLSYMS_ALIAS ] && \
+	    [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
 		ldflags="${ldflags} ${wl}--strip-debug"
 	fi
 
@@ -161,7 +162,11 @@ kallsyms()
 	fi
 
 	info KSYMS ${2}
-	scripts/kallsyms ${kallsymopt} ${1} > ${2}
+	if is_enabled CONFIG_KALLSYMS_ALIAS; then
+		ALIAS=".alias"
+		scripts/kas_alias/kas_alias ${1} >${1}${ALIAS}
+		fi
+	scripts/kallsyms ${kallsymopt} ${1}${ALIAS} > ${2}
 }
 
 # Perform one step in kallsyms generation, including temporary linking of
-- 
2.34.1


^ permalink raw reply related	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-08-28  8:04 [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms Alessandro Carminati (Red Hat)
@ 2023-08-29 14:51 ` Francis Laniel
  2023-09-02  7:26   ` Alessandro Carminati
  2023-08-30  6:00 ` Masami Hiramatsu
                   ` (3 subsequent siblings)
  4 siblings, 1 reply; 16+ messages in thread
From: Francis Laniel @ 2023-08-29 14:51 UTC (permalink / raw)
  To: Alessandro Carminati (Red Hat)
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Masahiro Yamada, Luis Chamberlain,
	Nathan Chancellor, Nick Desaulniers, Nicolas Schier,
	Alexander Lobakin, Nick Alcock, Kris Van Hees, Eugene Loh,
	Viktor Malik, Alessandro Carminati, linux-kbuild, linux-kernel,
	linux-trace-kernel, live-patching

Hi.

Le lundi 28 août 2023, 10:04:23 CEST Alessandro Carminati (Red Hat) a écrit :
> From: Alessandro Carminati <alessandro.carminati@gmail.com>
> 
> It is not uncommon for drivers or modules related to similar peripherals
> to have symbols with the exact same name.
> While this is not a problem for the kernel's binary itself, it becomes an
> issue when attempting to trace or probe specific functions using
> infrastructure like ftrace or kprobe.

Thank you for the patch!
I tested it and it works fine:
root@vm-amd64:~# grep -m 6 ' name_show' /proc/kallsyms 
ffffffff81108330 t name_show
ffffffff81108330 t name_show@_kernel_irq_irqdesc_c_264
ffffffff816d2dd0 t name_show
ffffffff816d2dd0 t name_show@_drivers_pnp_card_c_186
ffffffff81814990 t name_show
ffffffff81814990 t name_show@_drivers_gpu_drm_i915_gt_sysfs_engines_c_26

On the paper, it combines well with my other patch forbidding tracing non 
unique symbols.
I will nonetheless need to try yours on top of mine and I will let you know 
the result, even though everything should go well.

Regarding the code itself, from my review your implementation is good.
I was just wondering if we cannot avoid the first sort BY_NAME by modifying 
find_duplicates() and the returned structured, but the index you are using 
later should reduce the loopthrough time and compensate the first sort.
I have some specific comments but they are mainly nits:

> The tracing subsystem relies on the `nm -n vmlinux` output, which provides
> symbol information from the kernel's ELF binary. However, when multiple
> symbols share the same name, the standard nm output does not differentiate
> between them. This can lead to confusion and difficulty when trying to
> probe the intended symbol.
> 
>  ~ # cat /proc/kallsyms | grep " name_show"
>  ffffffff8c4f76d0 t name_show
>  ffffffff8c9cccb0 t name_show
>  ffffffff8cb0ac20 t name_show
>  ffffffff8cc728c0 t name_show
>  ffffffff8ce0efd0 t name_show
>  ffffffff8ce126c0 t name_show
>  ffffffff8ce1dd20 t name_show
>  ffffffff8ce24e70 t name_show
>  ffffffff8d1104c0 t name_show
>  ffffffff8d1fe480 t name_show
> 
> **kas_alias** addresses this challenge by extending the symbol names with
> unique suffixes during the kernel build process.
> The newly created aliases for these duplicated symbols are unique names
> that can be fed to the ftracefs interface. By doing so, it enables
> previously unreachable symbols to be probed.
> 
>  ~ # cat /proc/kallsyms | grep " name_show"
>  ffffffff974f76d0 t name_show
>  ffffffff974f76d0 t name_show__alias__6340

This output is outdated.
This is not a big problem but it would be better with the updated one as the 
"@_file_line" is better.

>  ffffffff979cccb0 t name_show
>  ffffffff979cccb0 t name_show__alias__6341
>  ffffffff97b0ac20 t name_show
>  ffffffff97b0ac20 t name_show__alias__6342
>  ffffffff97c728c0 t name_show
>  ffffffff97c728c0 t name_show__alias__6343
>  ffffffff97e0efd0 t name_show
>  ffffffff97e0efd0 t name_show__alias__6344
>  ffffffff97e126c0 t name_show
>  ffffffff97e126c0 t name_show__alias__6345
>  ffffffff97e1dd20 t name_show
>  ffffffff97e1dd20 t name_show__alias__6346
>  ffffffff97e24e70 t name_show
>  ffffffff97e24e70 t name_show__alias__6347
>  ffffffff981104c0 t name_show
>  ffffffff981104c0 t name_show__alias__6348
>  ffffffff981fe480 t name_show
>  ffffffff981fe480 t name_show__alias__6349
>  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
> 
>  > >/sys/kernel/tracing/kprobe_events
> 
>  ~ # cat /sys/kernel/tracing/kprobe_events
>  p:kprobes/evnt1 name_show__alias__6349
> 
> Changes from v1:
> - Integrated changes requested by Masami to exclude symbols with prefixes
>   "_cfi" and "_pfx".
> - Introduced a small framework to handle patterns that need to be excluded
>   from the alias production.
> - Excluded other symbols using the framework.
> - Introduced the ability to discriminate between text and data symbols.
> - Added two new config symbols in this version: CONFIG_KALLSYMS_ALIAS_DATA,
>   which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
>   excludes all filters and provides an alias for each duplicated symbol.
> 
> https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gm
> ail.com/
> 
> Changes from v2:
> - Alias tags are created by querying DWARF information from the vmlinux.
> - The filename + line number is normalized and appended to the original
> name. - The tag begins with '@' to indicate the symbol source.
> - Not a change, but worth mentioning, since the alias is added to the
> existing list, the old duplicated name is preserved, and the livepatch way
> of dealing with duplicates is maintained.
> - Acknowledging the existence of scenarios where inlined functions declared
> in header files may result in multiple copies due to compiler behavior,
> though it is not actionable as it does not pose an operational issue.
> - Highlighting a single exception where the same name refers to different
>   functions: the case of "compat_binfmt_elf.c," which directly includes
>   "binfmt_elf.c" producing identical function copies in two separate
>   modules.
> 
> sample from new v3
> 
>  ~ # cat /proc/kallsyms | grep gic_mask_irq
>  ffffd0b03c04dae4 t gic_mask_irq
>  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
>  ffffd0b03c050960 t gic_mask_irq
>  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
>  ~ #
> 
> https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gm
> ail.com/
> 
> Signed-off-by: Alessandro Carminati (Red Hat)
> <alessandro.carminati@gmail.com> ---
>  init/Kconfig                        |  36 ++++
>  scripts/Makefile                    |   4 +
>  scripts/kas_alias/Makefile          |   4 +
>  scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
>  scripts/kas_alias/a2l.h             |  32 ++++
>  scripts/kas_alias/duplicates_list.c |  70 ++++++++
>  scripts/kas_alias/duplicates_list.h |  15 ++
>  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
>  scripts/kas_alias/item_list.h       |  26 +++
>  scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
>  scripts/link-vmlinux.sh             |  11 +-
>  11 files changed, 910 insertions(+), 3 deletions(-)
>  create mode 100644 scripts/kas_alias/Makefile
>  create mode 100644 scripts/kas_alias/a2l.c
>  create mode 100644 scripts/kas_alias/a2l.h
>  create mode 100644 scripts/kas_alias/duplicates_list.c
>  create mode 100644 scripts/kas_alias/duplicates_list.h
>  create mode 100644 scripts/kas_alias/item_list.c
>  create mode 100644 scripts/kas_alias/item_list.h
>  create mode 100644 scripts/kas_alias/kas_alias.c
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index f7f65af4ee12..bc69fcd9cbc8 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1737,6 +1737,42 @@ config KALLSYMS_BASE_RELATIVE
>  	  time constants, and no relocation pass is required at runtime to fix
>  	  up the entries based on the runtime load address of the kernel.
> 
> +config KALLSYMS_ALIAS
> +	bool "Produces alias for duplicated symbols" if EXPERT
> +	depends on KALLSYMS && (DEBUG_INFO_DWARF4 || DEBUG_INFO_DWARF5)
> +	help
> +	  It is not uncommon for drivers or modules related to similar
> +	  peripherals to have symbols with the exact same name.
> +	  While this is not a problem for the kernel's binary itself, it
> +	  becomes an issue when attempting to trace or probe specific
> +	  functions using infrastructure like ftrace or kprobe.
> +
> +	  This option addresses this challenge by extending the symbol names
> +	  with unique suffixes during the kernel build process.
> +	  The newly created aliases for these duplicated symbols are unique
> +	  names that can be fed to the ftrace sysfs interface. By doing so, it
> +	  enables previously unreachable symbols to be probed.
> +
> +config CONFIG_KALLSYMS_ALIAS_DATA
> +	bool "Produces alias also for data"
> +	depends on KALLSYMS_ALIAS
> +	help
> +	  Sometimes it can be useful to refer to data. In live patch 
scenarios,
> +	  you may find yourself needing to use symbols that are shared with
> +	  other functions. Since symbols face the same issue as functions, 
this
> +	  option allows you to create aliases for data as well.
> +
> +config CONFIG_KALLSYMS_ALIAS_DATA_ALL
> +	bool "Removes all filter when producing data alias"
> +	depends on CONFIG_KALLSYMS_ALIAS_DATA
> +	help
> +	  When selecting data aliases, not all symbols are included in the set
> +	  This is because many symbols are unlikely to be used. If you choose
> +	  to have an alias for all data symbols, be aware that it will
> +	  significantly increase the size.
> +
> +	  If unsure, say N.
> +
>  # end of the "standard kernel features (expert users)" menu
> 
>  # syscall, maps, verifier
> diff --git a/scripts/Makefile b/scripts/Makefile
> index 32b6ba722728..65fafe17cfe5 100644
> --- a/scripts/Makefile
> +++ b/scripts/Makefile
> @@ -49,3 +49,7 @@ subdir-$(CONFIG_SECURITY_SELINUX) += selinux
> 
>  # Let clean descend into subdirs
>  subdir-	+= basic dtc gdb kconfig mod
> +
> +# KALLSyms alias
> +subdir-$(CONFIG_KALLSYMS_ALIAS) += kas_alias
> +
> diff --git a/scripts/kas_alias/Makefile b/scripts/kas_alias/Makefile
> new file mode 100644
> index 000000000000..e1fde69232b4
> --- /dev/null
> +++ b/scripts/kas_alias/Makefile
> @@ -0,0 +1,4 @@
> +# SPDX-License-Identifier: GPL-2.0
> +hostprogs-always-$(CONFIG_KALLSYMS_ALIAS)    += kas_alias
> +
> +kas_alias-objs        := duplicates_list.o item_list.o kas_alias.o a2l.o
> diff --git a/scripts/kas_alias/a2l.c b/scripts/kas_alias/a2l.c
> new file mode 100644
> index 000000000000..a9692ac30180
> --- /dev/null
> +++ b/scripts/kas_alias/a2l.c
> @@ -0,0 +1,268 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <sys/types.h>
> +#include <sys/wait.h>
> +#include <string.h>
> +#include <stdint.h>
> +#include <stdbool.h>
> +
> +#include "a2l.h"
> +
> +int addr2line_pid = -1;
> +int a2l_in[2];
> +int a2l_out[2];
> +char line[MAX_BUF];
> +char vmlinux_path[MAX_BUF];
> +char addr2line_cmd[MAX_CMD_LEN];
> +FILE *a2l_stdin, *a2l_stdout;
> +
> +static char *normalize_path(const char *input_path, char *output_path)
> +{
> +	char *prev_token = NULL;
> +	char *delimiter = "/";
> +	char inbuf[MAX_BUF];

Rather than using memset below you can initialize it like this above:
char inbuf[MAX_BUF] = {0};

> +	char *token;
> +	char *pos;
> +
> +	memset(inbuf, 0, MAX_BUF);
> +	*output_path = '\0';
> +	strncpy(inbuf, input_path, MAX_BUF);
> +	if (!input_path || !output_path || strlen(input_path) == 0)
> +		return NULL;
> +
> +	token = strtok(inbuf, delimiter);
> +	while (token) {
> +		if (strcmp(token, "..") == 0 && prev_token) {
> +			pos = strrchr(output_path, '/');

> +			if (pos)
> +				*pos = '\0';
> +
> +		} else if (strcmp(token, ".") != 0) {
> +			strcat(output_path, "/");
> +			strcat(output_path, token);
> +		}
> +
> +		prev_token = token;
> +		token = strtok(NULL, delimiter);
> +	}
> +
> +	return output_path;
> +}
> +
> +static void path_of(const char *full_path, char *path)
> +{
> +	const char *last_slash = strrchr(full_path, '/');
> +	size_t path_length;
> +	char cwd[MAX_BUF];
> +
> +	if (!last_slash) {
> +		if (getcwd(cwd, sizeof(cwd)))
> +			strcpy(path, cwd);
> +		else
> +			strcpy(path, ".");
> +	} else {
> +		path_length = last_slash - full_path;
> +		strncpy(path, full_path, path_length);
> +		path[path_length] = '\0';
> +	}
> +}
> +
> +static bool file_exists(const char *file_path)
> +{
> +	FILE *file;
> +
> +	file = fopen(file_path, "r");
> +	if (file) {
> +		fclose(file);
> +		return true;
> +	}
> +	return false;
> +}
> +
> +int addr2line_init(const char *cmd, const char *vmlinux)
> +{
> +	if ((!file_exists(cmd)) || (!file_exists(vmlinux))) {
> +		printf("file not found\n");
> +		return 0;
> +		}
> +
> +	path_of(vmlinux, vmlinux_path);
> +	if (pipe(a2l_in) == -1) {
> +		printf("Failed to create pipe\n");
> +		return 0;
> +	}
> +
> +	if (pipe(a2l_out) == -1) {
> +		printf("Failed to create pipe\n");
> +		return 0;
> +	}
> +
> +	addr2line_pid = fork();
> +	if (addr2line_pid == -1) {
> +		printf("Failed to fork process\n");
> +		close(a2l_in[P_READ]);
> +		close(a2l_in[P_WRITE]);
> +		close(a2l_out[P_READ]);
> +		close(a2l_out[P_WRITE]);
> +		return 0;
> +	}
> +
> +	if (addr2line_pid == 0) {
> +		dup2(a2l_in[P_READ], 0);
> +		dup2(a2l_out[P_WRITE], 1);
> +		close(a2l_in[P_WRITE]);
> +		close(a2l_out[P_READ]);
> +
> +		execlp(cmd, cmd, ADDR2LINE_ARGS, vmlinux, NULL);
> +
> +		printf("Failed to execute addr2line command\n");
> +		exit(1);
> +	} else {
> +		close(a2l_in[P_READ]);
> +		close(a2l_out[P_WRITE]);
> +	}
> +
> +	a2l_stdin = fdopen(a2l_in[P_WRITE], "w");
> +	if (!a2l_stdin) {
> +		printf("Failed to open pipe a2l_in\n");
> +		return 0;
> +	}
> +
> +	a2l_stdout = fdopen(a2l_out[P_READ], "r");
> +	if (!a2l_stdout) {
> +		printf("Failed to open pipe a2l_out\n");
> +		fclose(a2l_stdin);
> +		return 0;
> +	}
> +
> +	return 1;
> +}
> +
> +const char *remove_subdir(const char *home, const char *f_path)
> +{
> +	int i = 0;
> +
> +	while (*(home + i) == *(f_path + i))

Using home[i] and f_path[i] should do the trick too.

> +		i++;
> +
> +	return (strlen(home) != i) ? NULL : f_path + i;
> +}
> +
> +char *addr2line_get_lines(uint64_t address)
> +{
> +	char buf[MAX_BUF];
> +
> +	fprintf(a2l_stdin, "%08lx\n", address);
> +	fflush(a2l_stdin);
> +
> +	if (!fgets(line, sizeof(line), a2l_stdout)) {
> +		printf("Failed to read lines from addr2line\n");
> +		return NULL;
> +	}
> +
> +	if (!fgets(line, sizeof(line), a2l_stdout)) {
> +		printf("Failed to read lines from addr2line\n");
> +		return NULL;
> +	}
> +	line[strcspn(line, "\n")] = '\0';
> +	strncpy(buf, line, MAX_BUF);
> +	return normalize_path(buf, line);
> +}
> +
> +int addr2line_cleanup(void)
> +{
> +	int status;
> +
> +	if (addr2line_pid != -1) {
> +		kill(addr2line_pid, SIGKILL);
> +		waitpid(addr2line_pid, &status, 0);
> +		fclose(a2l_stdin);
> +		fclose(a2l_stdout);
> +		addr2line_pid = -1;
> +	}
> +
> +	return 1;
> +}
> +
> +static char *find_executable(const char *command)

Nice function, I would rather have tried to execve() the command.

> +{
> +	char *path_env = getenv("PATH");
> +	char *executable_path;
> +	char *path_copy;
> +	char *path;
> +	int n;
> +
> +	if (!path_env)
> +		return NULL;
> +
> +	path_copy = strdup(path_env);
> +	if (!path_copy)
> +		return NULL;
> +
> +	path = strtok(path_copy, ":");
> +	while (path) {
> +		n = snprintf(0, 0, "%s/%s", path, command);
> +		executable_path = (char *)malloc(n + 1);
> +		snprintf(executable_path, n + 1, "%s/%s", path, command);
> +		if (access(executable_path, X_OK) == 0) {
> +			free(path_copy);
> +			return executable_path;
> +		}
> +
> +	path = strtok(NULL, ":");
> +	free(executable_path);
> +	executable_path = NULL;

> +	}
> +
> +	free(path_copy);
> +	if (executable_path)
> +		free(executable_path);

If you arrive here, executable_path should be NULL, right?

> +	return NULL;
> +}
> +
> +const char *get_addr2line(int mode)
> +{
> +	char *buf = "";
> +
> +	switch (mode) {
> +	case A2L_CROSS:
> +		buf = getenv("CROSS_COMPILE");
> +		memcpy(addr2line_cmd, buf, strlen(buf));
> +	case A2L_DEFAULT:
> +		memcpy(addr2line_cmd + strlen(buf), ADDR2LINE, 
strlen(ADDR2LINE));
> +		buf = find_executable(addr2line_cmd);
> +		if (buf) {
> +			memcpy(addr2line_cmd, buf, strlen(buf));
> +			free(buf);
> +		}
> +		return addr2line_cmd;
> +	case A2L_LLVM:
> +	default:
> +		return NULL;
> +	}
> +}
> +
> +char *get_vmlinux(char *input)
> +{
> +	const char *match_string1 = ".syms";
> +	const char *match_string2 = ".tmp_vmlinux.kallsyms";
> +	char *result = NULL;
> +	char *match_pos;
> +
> +	match_pos = strstr(input, match_string1);
> +	if (!match_pos)
> +		return NULL;
> +
> +	match_pos = strstr(input, match_string2);
> +	if (!match_pos)
> +		return NULL;
> +
> +	result = strdup(input);
> +	match_pos = strstr(result, match_string1);
> +	*match_pos = '\0';
> +	return result;
> +}
> diff --git a/scripts/kas_alias/a2l.h b/scripts/kas_alias/a2l.h
> new file mode 100644
> index 000000000000..ca6419229dde
> --- /dev/null
> +++ b/scripts/kas_alias/a2l.h
> @@ -0,0 +1,32 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef A2L_H
> +#define A2L_H
> +#include <stdint.h>
> +
> +#define ADDR2LINE "addr2line"
> +#define ADDR2LINE_ARGS "-fe"
> +//#define VMLINUX "vmlinux"
> +#define MAX_BUF 4096
> +#define MAX_CMD_LEN 256
> +#define P_READ 0
> +#define P_WRITE 1
> +#define A2L_DEFAULT 1
> +#define A2L_CROSS 2
> +#define A2L_LLVM 3
> +#define A2L_MAKE_VALUE 2
> +
> +extern int addr2line_pid;
> +extern int a2l_in[2];
> +extern int a2l_out[2];
> +extern char line[MAX_BUF];
> +extern char vmlinux_path[MAX_BUF];
> +extern char addr2line_cmd[MAX_CMD_LEN];
> +
> +int addr2line_init(const char *cmd, const char *vmlinux);
> +char *addr2line_get_lines(uint64_t address);
> +int addr2line_cleanup(void);
> +const char *remove_subdir(const char *home, const char *f_path);
> +const char *get_addr2line(int mode);
> +char *get_vmlinux(char *input);
> +
> +#endif
> diff --git a/scripts/kas_alias/duplicates_list.c
> b/scripts/kas_alias/duplicates_list.c new file mode 100644
> index 000000000000..e7a3d2917937
> --- /dev/null
> +++ b/scripts/kas_alias/duplicates_list.c
> @@ -0,0 +1,70 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <stdint.h>
> +#include <stdio.h>
> +#include <string.h>
> +#include <stdlib.h>
> +#include <stdbool.h>
> +
> +#include "item_list.h"
> +#include "duplicates_list.h"
> +
> +struct duplicate_item *find_duplicates(struct item *list)
> +{
> +	struct duplicate_item *current_duplicate = NULL;
> +	struct duplicate_item *duplicates = NULL;
> +	struct duplicate_item *new_duplicate;
> +	struct item *current_item = list;
> +	bool prev_was_duplicate = false;
> +	struct item *prev_item = NULL;
> +
> +	while (current_item) {
> +		if ((prev_item && (strcmp(current_item->symb_name, prev_item-
>symb_name)
> == 0)) || +		    prev_was_duplicate) {
> +			if (!duplicates) {
> +				duplicates = malloc(sizeof(struct 
duplicate_item));
> +				if (!duplicates)
> +					return NULL;
> +
> +				duplicates->original_item = prev_item;
> +				duplicates->next = NULL;
> +				current_duplicate = duplicates;
> +			} else {
> +				new_duplicate = malloc(sizeof(struct 
duplicate_item));
> +				if (!new_duplicate) {
> +					free_duplicates(&duplicates);
> +					return NULL;
> +				}
> +
> +				new_duplicate->original_item = prev_item;
> +				new_duplicate->next = NULL;
> +				current_duplicate->next = new_duplicate;
> +				current_duplicate = new_duplicate;
> +
> +				if ((strcmp(current_item->symb_name, prev_item-
>symb_name) != 0) &&
> +				    (prev_was_duplicate))
> +					prev_was_duplicate = false;
> +				else
> +					prev_was_duplicate = true;

You can remove the branch and set prev_was_duplicate to:
prev_was_duplicate = strcmp(current_item->symb_name, prev_item->symb_name) != 
0 && prev_was_duplicate;

> +			}
> +		}
> +
> +		prev_item = current_item;
> +		current_item = current_item->next;
> +	}
> +
> +	return duplicates;
> +}
> +
> +void free_duplicates(struct duplicate_item **duplicates)
> +{
> +	struct duplicate_item *duplicates_iterator = *duplicates;
> +	struct duplicate_item *app;
> +
> +	while (duplicates_iterator) {
> +		app = duplicates_iterator;
> +		duplicates_iterator = duplicates_iterator->next;
> +		free(app);
> +	}
> +
> +	*duplicates = NULL;
> +}
> diff --git a/scripts/kas_alias/duplicates_list.h
> b/scripts/kas_alias/duplicates_list.h new file mode 100644
> index 000000000000..76aa73e584bc
> --- /dev/null
> +++ b/scripts/kas_alias/duplicates_list.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef DUPLICATES_LIST_H
> +#define DUPLICATES_LIST_H
> +
> +#include "item_list.h"
> +
> +struct duplicate_item {
> +	struct item *original_item;
> +	struct duplicate_item *next;
> +};
> +
> +struct duplicate_item *find_duplicates(struct item *list);
> +void free_duplicates(struct duplicate_item **duplicates);
> +
> +#endif
> diff --git a/scripts/kas_alias/item_list.c b/scripts/kas_alias/item_list.c
> new file mode 100644
> index 000000000000..48f2e525592a
> --- /dev/null
> +++ b/scripts/kas_alias/item_list.c
> @@ -0,0 +1,230 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <stdint.h>
> +#include <string.h>
> +#include <stdbool.h>
> +#include <assert.h>
> +#include "item_list.h"
> +
> +#define CHECK_ORDER_BY_ADDRESS(sort_by, current, temp, op) \
> +	((sort_by) == BY_ADDRESS && (current)->addr op (temp)->addr)
> +#define CHECK_ORDER_BY_NAME(sort_by, current, temp, op) \
> +	((sort_by) == BY_NAME && strcmp((current)->symb_name, (temp)-
>symb_name)
> op 0) +
> +struct item *list_index[96] = {0};
> +
> +void build_index(struct item *list)
> +{
> +	char current_first_letter = ' ';
> +	struct item *current = list;
> +
> +	while (current) {
> +		if (current->symb_name[0] != current_first_letter) {
> +			current_first_letter = current->symb_name[0];
> +			list_index[current_first_letter - 32] = current;

> +		}
> +		current = current->next;
> +	}
> +}
> +
> +struct item *add_item(struct item **list, const char *name, char stype,
> uint64_t addr) +{
> +	struct item *new_item;
> +	struct item *current;
> +
> +	new_item = malloc(sizeof(struct item));
> +	if (!new_item)
> +		return NULL;
> +
> +	strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> +	new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> +	new_item->addr = addr;
> +	new_item->stype = stype;
> +	new_item->next = NULL;
> +
> +	if (!(*list)) {
> +		*list = new_item;
> +	} else {
> +		current = *list;
> +		while (current->next)
> +			current = current->next;
> +
> +		current->next = new_item;
> +	}
> +	return new_item;
> +}
> +
> +void sort_list(struct item **list, int sort_by)
> +{
> +	struct item *current = *list;
> +	struct item *sorted = NULL;
> +	struct item *next_item;
> +	struct item *temp;
> +
> +	if (!(*list) || !((*list)->next))
> +		return;
> +
> +	while (current) {
> +		next_item = current->next;
> +		if (!sorted ||
> +		    (CHECK_ORDER_BY_ADDRESS(sort_by, current, sorted, <) ||
> +		    CHECK_ORDER_BY_NAME(sort_by, current, sorted, >=))) {
> +			current->next = sorted;
> +			sorted = current;
> +		} else {
> +			temp = sorted;
> +			while (temp->next &&
> +			       (CHECK_ORDER_BY_ADDRESS(sort_by, current, temp-
>next, >=) ||
> +			       CHECK_ORDER_BY_NAME(sort_by, current, temp->next, 
>=)))
> +				temp = temp->next;
> +
> +			current->next = temp->next;
> +			temp->next = current;
> +		}
> +		current = next_item;
> +	}
> +
> +	*list = sorted;
> +}
> +
> +struct item *merge(struct item *left, struct item *right, int sort_by)

> +{
> +	struct item *current = NULL;
> +	struct item *result = NULL;
> +
> +	if (!left)
> +		return right;
> +	if (!right)
> +		return left;
> +
> +	if (sort_by == BY_NAME) {
> +		if (strcmp(left->symb_name, right->symb_name) <= 0) {
> +			result = left;
> +			left = left->next;
> +		} else {
> +			result = right;
> +			right = right->next;
> +		}
> +	} else {
> +		if (sort_by == BY_ADDRESS) {
> +			if (left->addr <= right->addr) {
> +				result = left;
> +				left = left->next;
> +			} else {
> +				result = right;
> +				right = right->next;
> +			}
> +		}
> +	}
> +
> +	current = result;
> +
> +	while (left && right) {
> +		if (sort_by == BY_NAME) {
> +			if (strcmp(left->symb_name, right->symb_name) <= 0) {
> +				current->next = left;
> +				left = left->next;
> +			} else {
> +				current->next = right;
> +				right = right->next;
> +			}
> +		} else {
> +			if (sort_by == BY_ADDRESS) {
> +				if (left->addr <= right->addr) {
> +					current->next = left;
> +					left = left->next;
> +				} else {
> +					current->next = right;
> +					right = right->next;
> +				}
> +			}
> +		}
> +
> +		current = current->next;
> +	}
> +
> +	if (left) {
> +		current->next = left;
> +	} else {
> +		if (right)

> +			current->next = right;
> +	}
> +
> +	return result;
> +}
> +
> +struct item *merge_sort(struct item *head, int sort_by)
> +{
> +	struct item *right;
> +	struct item *slow;
> +	struct item *fast;
> +	struct item *left;
> +
> +	if (!head || !head->next)
> +		return head;
> +
> +	slow = head;
> +	fast = head->next;
> +
> +	while (fast && fast->next) {
> +		slow = slow->next;
> +		fast = fast->next->next;
> +	}
> +
> +	left = head;
> +	right = slow->next;
> +	slow->next = NULL;
> +
> +	left = merge_sort(left, sort_by);
> +	right = merge_sort(right, sort_by);
> +
> +	return merge(left, right, sort_by);
> +}
> +
> +void sort_list_m(struct item **head, int sort_by)
> +{
> +	if (!(*head) || !((*head)->next))
> +		return;
> +
> +	*head = merge_sort(*head, sort_by);
> +}
> +
> +int insert_after(struct item *list, const uint64_t search_addr,
> +		 const char *name, uint64_t addr, char stype)
> +{
> +	struct item *new_item;
> +	struct item *current;
> +	int ret = 0;
> +
> +	current = (list_index[name[0] - 32]) ? list_index[name[0] - 32] : 
list;
> +	while (current) {
> +		if (current->addr == search_addr) {
> +			new_item = malloc(sizeof(struct item));
> +			if (!new_item)
> +				return ret;
> +			strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> +			new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> +			new_item->addr = addr;
> +			new_item->stype = stype;
> +			new_item->next = current->next;
> +			current->next = new_item;
> +			ret = 1;
> +			break;

> +		}
> +		current = current->next;
> +	}
> +	return ret;
> +}
> +
> +void free_items(struct item **head)
> +{
> +	struct item *app, *item_iterator = *head;
> +
> +	while (item_iterator) {
> +		app = item_iterator;
> +		item_iterator = item_iterator->next;
> +		free(app);
> +	}
> +	*head = NULL;
> +}
> diff --git a/scripts/kas_alias/item_list.h b/scripts/kas_alias/item_list.h
> new file mode 100644
> index 000000000000..b4891cb088ee
> --- /dev/null
> +++ b/scripts/kas_alias/item_list.h
> @@ -0,0 +1,26 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef ITEM_LIST_H
> +#define ITEM_LIST_H
> +#include <stdint.h>
> +
> +#define MAX_NAME_SIZE 256
> +#define BY_ADDRESS 1
> +#define BY_NAME 2
> +
> +struct item {
> +	char		symb_name[MAX_NAME_SIZE];
> +	uint64_t	addr;
> +	char		stype;
> +	struct item	*next;
> +};
> +
> +void build_index(struct item *list);
> +struct item *add_item(struct item **list, const char *name, char stype,
> uint64_t addr); +void sort_list(struct item **list, int sort_by);
> +struct item *merge(struct item *left, struct item *right, int sort_by);
> +struct item *merge_sort(struct item *head, int sort_by);
> +void sort_list_m(struct item **head, int sort_by);
> +int insert_after(struct item *list, const uint64_t search_addr,
> +		 const char *name, uint64_t addr, char stype);
> +void free_items(struct item **head);
> +#endif
> diff --git a/scripts/kas_alias/kas_alias.c b/scripts/kas_alias/kas_alias.c
> new file mode 100644
> index 000000000000..532aeb39f851
> --- /dev/null
> +++ b/scripts/kas_alias/kas_alias.c
> @@ -0,0 +1,217 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <stdint.h>
> +#include <unistd.h>
> +#include <string.h>
> +#include <stdbool.h>
> +#include <stdarg.h>
> +#include <regex.h>
> +
> +#include "item_list.h"
> +#include "duplicates_list.h"
> +#include "a2l.h"
> +
> +#define SYMB_IS_TEXT(s) ((((s)->stype) == 't') ||  (((s)->stype) == 'T'))
> +#define SYMB_IS_DATA(s) ((((s)->stype) == 'b') ||  (((s)->stype) == 'B') ||
> \ +			 (((s)->stype) == 'd') ||  (((s)->stype) == 'D') || \
> +			 (((s)->stype) == 'r') ||  (((s)->stype) == 'R'))
> +#ifdef CONFIG_KALLSYMS_ALIAS_DATA
> +#define SYMB_NEEDS_ALIAS(s) (SYMB_IS_TEXT(s) || SYMB_IS_DATA(s))
> +#else
> +#define SYMB_NEEDS_ALIAS(s) SYMB_IS_TEXT(s)
> +#endif
> +#define FNOMATCH 0
> +#define FMATCH 1
> +#define EREGEX 2
> +
> +const char *ignore_regex[] = {
> +	"^__cfi_.*$",				// __cfi_ preamble
> +#ifndef CONFIG_KALLSYMS_ALIAS_DATA_ALL
> +	"^_*TRACE_SYSTEM.*$",
> +	"^__already_done\\.[0-9]+$",		// Call a function once data
> +	"^___tp_str\\.[0-9]+$",
> +	"^___done\\.[0-9]+$",
> +	"^__print_once\\.[0-9]+$",
> +	"^_rs\\.[0-9]+$",
> +	"^__compound_literal\\.[0-9]+$",
> +	"^___once_key\\.[0-9]+$",
> +	"^__func__\\.[0-9]+$",
> +	"^__msg\\.[0-9]+$",
> +	"^CSWTCH\\.[0-9]+$",
> +	"^__flags\\.[0-9]+$",
> +	"^__wkey.*$",
> +	"^__mkey.*$",
> +	"^__key.*$",
> +#endif
> +	"^__pfx_.*$"				// NOP-padding
> +};
> +
> +int suffix_serial;
> +
> +static inline void verbose_msg(bool verbose, const char *fmt, ...)
> +{
> +	va_list args;
> +
> +	va_start(args, fmt);
> +	if (verbose)
> +		printf(fmt, args);
> +
> +	va_end(args);
> +}
> +
> +static void create_suffix(const char *name, char *output_suffix)
> +{
> +	sprintf(output_suffix, "%s__alias__%d", name, suffix_serial++);
> +}
> +
> +static void create_file_suffix(const char *name, uint64_t address, char
> *output_suffix, char *cwd) +{
> +	const char *f_path;
> +	char *buf;
> +	int i = 0;
> +
> +	buf = addr2line_get_lines(address);
> +	f_path = remove_subdir(cwd, buf);
> +	if (f_path) {
> +		sprintf(output_suffix, "%s@%s", name, f_path);
> +		while (*(output_suffix + i) != '\0') {
> +			switch (*(output_suffix + i)) {
> +			case '/':
> +			case ':':
> +			case '.':
> +				*(output_suffix + i) = '_';
> +				break;
> +			default:
> +			}
> +		i++;
> +		}
> +	} else {
> +		create_suffix(name, output_suffix);
> +	}
> +}
> +
> +static int filter_symbols(char *symbol, const char **ignore_list, int
> regex_no) +{
> +	regex_t regex;
> +	int res, i;
> +
> +	for (i = 0; i < regex_no; i++) {
> +		res = regcomp(&regex, ignore_list[i], REG_EXTENDED);
> +		if (res)
> +			return -EREGEX;
> +
> +		res = regexec(&regex, symbol, 0, NULL, 0);
> +		regfree(&regex);
> +		switch (res) {
> +		case 0:
> +			return FMATCH;
> +		case REG_NOMATCH:
> +			break;
> +		default:
> +			return -EREGEX;
> +		}
> +	}
> +
> +	return FNOMATCH;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	char t, sym_name[MAX_NAME_SIZE], new_name[MAX_NAME_SIZE + 15];
> +	struct duplicate_item  *duplicate_iterator;
> +	struct duplicate_item *duplicate;
> +	struct item *head = {NULL};
> +	bool need_2_process = true;
> +	struct item *last = {NULL};
> +	struct item  *current;
> +	int verbose_mode = 0;
> +	uint64_t address;
> +	FILE *fp;
> +	int res;
> +
> +	if (argc < 2 || argc > 3) {
> +		printf("Usage: %s <nmfile> [-verbose]\n", argv[0]);
> +		return 1;
> +	}
> +
> +	if (argc == 3 && strcmp(argv[2], "-verbose") == 0)
> +		verbose_mode = 1;
> +
> +	verbose_msg(verbose_mode, "Scanning nm data(%s)\n", argv[1]);
> +
> +	fp = fopen(argv[1], "r");
> +	if (!fp) {
> +		printf("Can't open input file.\n");
> +		return 1;
> +	}
> +
> +	if (!addr2line_init(get_addr2line(A2L_DEFAULT), get_vmlinux(argv[1])))
> +		return 1;
> +
> +	while (fscanf(fp, "%lx %c %99s\n", &address, &t, sym_name) == 3) {
> +		if (strstr(sym_name, "@_")) {
> +			if (verbose_mode && need_2_process)
> +				printf("Already processed\n");
> +			need_2_process = false;
> +			}
> +		last = add_item(&last, sym_name, t, address);
> +		if (!last) {
> +			printf("Error in allocate memory\n");
> +			free_items(&head);
> +			return 1;
> +		}
> +
> +		if (!head)
> +			head = last;
> +	}
> +
> +	fclose(fp);
> +
> +	if (need_2_process) {
> +		verbose_msg(verbose_mode, "Sorting nm data\n");
> +		sort_list_m(&head, BY_NAME);
> +		verbose_msg(verbose_mode, "Scanning nm data for duplicates\n");
> +		duplicate = find_duplicates(head);
> +		if (!duplicate) {
> +			printf("Error in duplicates list\n");
> +			return 1;
> +		}
> +
> +		verbose_msg(verbose_mode, "Applying suffixes\n");
> +		build_index(head);
> +		duplicate_iterator = duplicate;
> +		while (duplicate_iterator) {
> +			res = filter_symbols(duplicate_iterator->original_item-
>symb_name,
> +					     ignore_regex, sizeof(ignore_regex) /
> +					     sizeof(ignore_regex[0]));
> +			if (res != FMATCH &&
> +			    SYMB_NEEDS_ALIAS(duplicate_iterator->original_item)) 
{
> +				if (res < 0)
> +					return 1;
> +
> +				create_file_suffix(duplicate_iterator-
>original_item->symb_name,
> +						   duplicate_iterator-
>original_item->addr,
> +						   new_name, vmlinux_path);
> +				if (!insert_after(head, duplicate_iterator-
>original_item->addr,
> +						  new_name, duplicate_iterator-
>original_item->addr,
> +						  duplicate_iterator-
>original_item->stype))
> +					return 1;
> +			}
> +
> +			duplicate_iterator = duplicate_iterator->next;
> +		}
> +
> +		sort_list_m(&head, BY_ADDRESS);
> +	}
> +	current = head;
> +	while (current) {
> +		printf("%08lx %c %s\n", current->addr, current->stype,
> current->symb_name); +		current = current->next;
> +	}
> +
> +	free_items(&head);
> +	free_duplicates(&duplicate);
> +	addr2line_cleanup();
> +	return 0;
> +}
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index a432b171be82..cacf60b597ce 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -89,8 +89,9 @@ vmlinux_link()
> 
>  	ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
> 
> -	# The kallsyms linking does not need debug symbols included.
> -	if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> +	# The kallsyms linking does not need debug symbols included, unless 
the
> KALLSYMS_ALIAS. +	if [ ! is_enabled CONFIG_KALLSYMS_ALIAS ] && \
> +	    [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
>  		ldflags="${ldflags} ${wl}--strip-debug"
>  	fi
> 
> @@ -161,7 +162,11 @@ kallsyms()
>  	fi
> 
>  	info KSYMS ${2}
> -	scripts/kallsyms ${kallsymopt} ${1} > ${2}
> +	if is_enabled CONFIG_KALLSYMS_ALIAS; then
> +		ALIAS=".alias"
> +		scripts/kas_alias/kas_alias ${1} >${1}${ALIAS}
> +		fi
> +	scripts/kallsyms ${kallsymopt} ${1}${ALIAS} > ${2}
>  }
> 
>  # Perform one step in kallsyms generation, including temporary linking of

Best regards.



^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-08-28  8:04 [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms Alessandro Carminati (Red Hat)
  2023-08-29 14:51 ` Francis Laniel
@ 2023-08-30  6:00 ` Masami Hiramatsu
  2023-09-02  7:26   ` Alessandro Carminati
  2023-09-01  5:31 ` Masahiro Yamada
                   ` (2 subsequent siblings)
  4 siblings, 1 reply; 16+ messages in thread
From: Masami Hiramatsu @ 2023-08-30  6:00 UTC (permalink / raw)
  To: Alessandro Carminati (Red Hat)
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Masahiro Yamada, Luis Chamberlain,
	Nathan Chancellor, Nick Desaulniers, Nicolas Schier,
	Alexander Lobakin, Nick Alcock, Kris Van Hees, Eugene Loh,
	Francis Laniel, Viktor Malik, linux-kbuild, linux-kernel,
	linux-trace-kernel, live-patching

Hi Alessandro,

Thanks for your update!

On Mon, 28 Aug 2023 08:04:23 +0000
"Alessandro Carminati (Red Hat)" <alessandro.carminati@gmail.com> wrote:

> From: Alessandro Carminati <alessandro.carminati@gmail.com>
> 
> It is not uncommon for drivers or modules related to similar peripherals
> to have symbols with the exact same name.
> While this is not a problem for the kernel's binary itself, it becomes an
> issue when attempting to trace or probe specific functions using
> infrastructure like ftrace or kprobe.
> 
> The tracing subsystem relies on the `nm -n vmlinux` output, which provides
> symbol information from the kernel's ELF binary. However, when multiple
> symbols share the same name, the standard nm output does not differentiate
> between them. This can lead to confusion and difficulty when trying to
> probe the intended symbol.
> 
>  ~ # cat /proc/kallsyms | grep " name_show"
>  ffffffff8c4f76d0 t name_show
>  ffffffff8c9cccb0 t name_show
>  ffffffff8cb0ac20 t name_show
>  ffffffff8cc728c0 t name_show
>  ffffffff8ce0efd0 t name_show
>  ffffffff8ce126c0 t name_show
>  ffffffff8ce1dd20 t name_show
>  ffffffff8ce24e70 t name_show
>  ffffffff8d1104c0 t name_show
>  ffffffff8d1fe480 t name_show
> 
> **kas_alias** addresses this challenge by extending the symbol names with
> unique suffixes during the kernel build process.
> The newly created aliases for these duplicated symbols are unique names
> that can be fed to the ftracefs interface. By doing so, it enables
> previously unreachable symbols to be probed.
> 
>  ~ # cat /proc/kallsyms | grep " name_show"
>  ffffffff974f76d0 t name_show
>  ffffffff974f76d0 t name_show__alias__6340
>  ffffffff979cccb0 t name_show
>  ffffffff979cccb0 t name_show__alias__6341
>  ffffffff97b0ac20 t name_show
>  ffffffff97b0ac20 t name_show__alias__6342
>  ffffffff97c728c0 t name_show
>  ffffffff97c728c0 t name_show__alias__6343
>  ffffffff97e0efd0 t name_show
>  ffffffff97e0efd0 t name_show__alias__6344
>  ffffffff97e126c0 t name_show
>  ffffffff97e126c0 t name_show__alias__6345
>  ffffffff97e1dd20 t name_show
>  ffffffff97e1dd20 t name_show__alias__6346
>  ffffffff97e24e70 t name_show
>  ffffffff97e24e70 t name_show__alias__6347
>  ffffffff981104c0 t name_show
>  ffffffff981104c0 t name_show__alias__6348
>  ffffffff981fe480 t name_show
>  ffffffff981fe480 t name_show__alias__6349
>  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
>  > >/sys/kernel/tracing/kprobe_events
>  ~ # cat /sys/kernel/tracing/kprobe_events
>  p:kprobes/evnt1 name_show__alias__6349
> 
> Changes from v1:
> - Integrated changes requested by Masami to exclude symbols with prefixes
>   "_cfi" and "_pfx".
> - Introduced a small framework to handle patterns that need to be excluded
>   from the alias production.
> - Excluded other symbols using the framework.
> - Introduced the ability to discriminate between text and data symbols.
> - Added two new config symbols in this version: CONFIG_KALLSYMS_ALIAS_DATA,
>   which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
>   excludes all filters and provides an alias for each duplicated symbol.
> 
> https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gmail.com/
> 
> Changes from v2:
> - Alias tags are created by querying DWARF information from the vmlinux.
> - The filename + line number is normalized and appended to the original name.
> - The tag begins with '@' to indicate the symbol source.
> - Not a change, but worth mentioning, since the alias is added to the existing
>   list, the old duplicated name is preserved, and the livepatch way of dealing
>   with duplicates is maintained.
> - Acknowledging the existence of scenarios where inlined functions declared in
>   header files may result in multiple copies due to compiler behavior, though
>    it is not actionable as it does not pose an operational issue.
> - Highlighting a single exception where the same name refers to different
>   functions: the case of "compat_binfmt_elf.c," which directly includes
>   "binfmt_elf.c" producing identical function copies in two separate
>   modules.
> 
> sample from new v3
> 
>  ~ # cat /proc/kallsyms | grep gic_mask_irq
>  ffffd0b03c04dae4 t gic_mask_irq
>  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
>  ffffd0b03c050960 t gic_mask_irq
>  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404

Could you also update the sample output in the patch description?
And I can not see this line information but a serial number aliases,
is there any way to enable this file-name aliases? (LLVM is not supported?)
I think we'd better to have a new CONFIG_KALLSYMS_ALIAS_SRCLINE and
clarify what is required.

>  ~ #
> 
> https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gmail.com/
> 
> Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> ---
>  init/Kconfig                        |  36 ++++
>  scripts/Makefile                    |   4 +
>  scripts/kas_alias/Makefile          |   4 +
>  scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
>  scripts/kas_alias/a2l.h             |  32 ++++
>  scripts/kas_alias/duplicates_list.c |  70 ++++++++
>  scripts/kas_alias/duplicates_list.h |  15 ++
>  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
>  scripts/kas_alias/item_list.h       |  26 +++
>  scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
>  scripts/link-vmlinux.sh             |  11 +-
>  11 files changed, 910 insertions(+), 3 deletions(-)
>  create mode 100644 scripts/kas_alias/Makefile
>  create mode 100644 scripts/kas_alias/a2l.c
>  create mode 100644 scripts/kas_alias/a2l.h
>  create mode 100644 scripts/kas_alias/duplicates_list.c
>  create mode 100644 scripts/kas_alias/duplicates_list.h
>  create mode 100644 scripts/kas_alias/item_list.c
>  create mode 100644 scripts/kas_alias/item_list.h
>  create mode 100644 scripts/kas_alias/kas_alias.c
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index f7f65af4ee12..bc69fcd9cbc8 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1737,6 +1737,42 @@ config KALLSYMS_BASE_RELATIVE
>  	  time constants, and no relocation pass is required at runtime to fix
>  	  up the entries based on the runtime load address of the kernel.
>  
> +config KALLSYMS_ALIAS
> +	bool "Produces alias for duplicated symbols" if EXPERT
> +	depends on KALLSYMS && (DEBUG_INFO_DWARF4 || DEBUG_INFO_DWARF5)
> +	help
> +	  It is not uncommon for drivers or modules related to similar
> +	  peripherals to have symbols with the exact same name.
> +	  While this is not a problem for the kernel's binary itself, it
> +	  becomes an issue when attempting to trace or probe specific
> +	  functions using infrastructure like ftrace or kprobe.
> +
> +	  This option addresses this challenge by extending the symbol names
> +	  with unique suffixes during the kernel build process.
> +	  The newly created aliases for these duplicated symbols are unique
> +	  names that can be fed to the ftrace sysfs interface. By doing so, it
> +	  enables previously unreachable symbols to be probed.
> +
> +config CONFIG_KALLSYMS_ALIAS_DATA

You don't need 'CONFIG_' prefix here.

> +	bool "Produces alias also for data"
> +	depends on KALLSYMS_ALIAS
> +	help
> +	  Sometimes it can be useful to refer to data. In live patch scenarios,
> +	  you may find yourself needing to use symbols that are shared with
> +	  other functions. Since symbols face the same issue as functions, this
> +	  option allows you to create aliases for data as well.
> +
> +config CONFIG_KALLSYMS_ALIAS_DATA_ALL
> +	bool "Removes all filter when producing data alias"
> +	depends on CONFIG_KALLSYMS_ALIAS_DATA
> +	help
> +	  When selecting data aliases, not all symbols are included in the set
> +	  This is because many symbols are unlikely to be used. If you choose
> +	  to have an alias for all data symbols, be aware that it will
> +	  significantly increase the size.
> +
> +	  If unsure, say N.
> +
>  # end of the "standard kernel features (expert users)" menu
>  
>  # syscall, maps, verifier
> diff --git a/scripts/Makefile b/scripts/Makefile
> index 32b6ba722728..65fafe17cfe5 100644
> --- a/scripts/Makefile
> +++ b/scripts/Makefile
> @@ -49,3 +49,7 @@ subdir-$(CONFIG_SECURITY_SELINUX) += selinux
>  
>  # Let clean descend into subdirs
>  subdir-	+= basic dtc gdb kconfig mod
> +
> +# KALLSyms alias
> +subdir-$(CONFIG_KALLSYMS_ALIAS) += kas_alias
> +
> diff --git a/scripts/kas_alias/Makefile b/scripts/kas_alias/Makefile
> new file mode 100644
> index 000000000000..e1fde69232b4
> --- /dev/null
> +++ b/scripts/kas_alias/Makefile
> @@ -0,0 +1,4 @@
> +# SPDX-License-Identifier: GPL-2.0
> +hostprogs-always-$(CONFIG_KALLSYMS_ALIAS)    += kas_alias
> +
> +kas_alias-objs        := duplicates_list.o item_list.o kas_alias.o a2l.o
> diff --git a/scripts/kas_alias/a2l.c b/scripts/kas_alias/a2l.c
> new file mode 100644
> index 000000000000..a9692ac30180
> --- /dev/null
> +++ b/scripts/kas_alias/a2l.c
> @@ -0,0 +1,268 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <sys/types.h>
> +#include <sys/wait.h>
> +#include <string.h>
> +#include <stdint.h>
> +#include <stdbool.h>
> +
> +#include "a2l.h"
> +
> +int addr2line_pid = -1;
> +int a2l_in[2];
> +int a2l_out[2];
> +char line[MAX_BUF];
> +char vmlinux_path[MAX_BUF];
> +char addr2line_cmd[MAX_CMD_LEN];
> +FILE *a2l_stdin, *a2l_stdout;
> +
> +static char *normalize_path(const char *input_path, char *output_path)
> +{
> +	char *prev_token = NULL;
> +	char *delimiter = "/";
> +	char inbuf[MAX_BUF];
> +	char *token;
> +	char *pos;
> +
> +	memset(inbuf, 0, MAX_BUF);
> +	*output_path = '\0';
> +	strncpy(inbuf, input_path, MAX_BUF);
> +	if (!input_path || !output_path || strlen(input_path) == 0)
> +		return NULL;
> +
> +	token = strtok(inbuf, delimiter);
> +	while (token) {
> +		if (strcmp(token, "..") == 0 && prev_token) {
> +			pos = strrchr(output_path, '/');
> +			if (pos)
> +				*pos = '\0';
> +
> +		} else if (strcmp(token, ".") != 0) {
> +			strcat(output_path, "/");
> +			strcat(output_path, token);
> +		}
> +
> +		prev_token = token;
> +		token = strtok(NULL, delimiter);
> +	}
> +
> +	return output_path;
> +}
> +
> +static void path_of(const char *full_path, char *path)
> +{
> +	const char *last_slash = strrchr(full_path, '/');
> +	size_t path_length;
> +	char cwd[MAX_BUF];
> +
> +	if (!last_slash) {
> +		if (getcwd(cwd, sizeof(cwd)))
> +			strcpy(path, cwd);
> +		else
> +			strcpy(path, ".");
> +	} else {
> +		path_length = last_slash - full_path;
> +		strncpy(path, full_path, path_length);
> +		path[path_length] = '\0';
> +	}
> +}
> +
> +static bool file_exists(const char *file_path)
> +{
> +	FILE *file;
> +
> +	file = fopen(file_path, "r");
> +	if (file) {
> +		fclose(file);
> +		return true;
> +	}
> +	return false;
> +}
> +
> +int addr2line_init(const char *cmd, const char *vmlinux)
> +{
> +	if ((!file_exists(cmd)) || (!file_exists(vmlinux))) {
> +		printf("file not found\n");
> +		return 0;
> +		}

nit: mis-indentation?

> +
> +	path_of(vmlinux, vmlinux_path);
> +	if (pipe(a2l_in) == -1) {
> +		printf("Failed to create pipe\n");
> +		return 0;
> +	}
> +
> +	if (pipe(a2l_out) == -1) {
> +		printf("Failed to create pipe\n");
> +		return 0;
> +	}
> +
> +	addr2line_pid = fork();
> +	if (addr2line_pid == -1) {
> +		printf("Failed to fork process\n");
> +		close(a2l_in[P_READ]);
> +		close(a2l_in[P_WRITE]);
> +		close(a2l_out[P_READ]);
> +		close(a2l_out[P_WRITE]);
> +		return 0;
> +	}
> +
> +	if (addr2line_pid == 0) {
> +		dup2(a2l_in[P_READ], 0);
> +		dup2(a2l_out[P_WRITE], 1);
> +		close(a2l_in[P_WRITE]);
> +		close(a2l_out[P_READ]);
> +
> +		execlp(cmd, cmd, ADDR2LINE_ARGS, vmlinux, NULL);
> +
> +		printf("Failed to execute addr2line command\n");
> +		exit(1);
> +	} else {
> +		close(a2l_in[P_READ]);
> +		close(a2l_out[P_WRITE]);
> +	}
> +
> +	a2l_stdin = fdopen(a2l_in[P_WRITE], "w");
> +	if (!a2l_stdin) {
> +		printf("Failed to open pipe a2l_in\n");
> +		return 0;
> +	}
> +
> +	a2l_stdout = fdopen(a2l_out[P_READ], "r");
> +	if (!a2l_stdout) {
> +		printf("Failed to open pipe a2l_out\n");
> +		fclose(a2l_stdin);
> +		return 0;
> +	}
> +
> +	return 1;
> +}
> +
> +const char *remove_subdir(const char *home, const char *f_path)
> +{
> +	int i = 0;
> +
> +	while (*(home + i) == *(f_path + i))
> +		i++;
> +
> +	return (strlen(home) != i) ? NULL : f_path + i;
> +}
> +
> +char *addr2line_get_lines(uint64_t address)
> +{
> +	char buf[MAX_BUF];
> +
> +	fprintf(a2l_stdin, "%08lx\n", address);
> +	fflush(a2l_stdin);
> +
> +	if (!fgets(line, sizeof(line), a2l_stdout)) {
> +		printf("Failed to read lines from addr2line\n");
> +		return NULL;
> +	}
> +
> +	if (!fgets(line, sizeof(line), a2l_stdout)) {
> +		printf("Failed to read lines from addr2line\n");
> +		return NULL;
> +	}
> +
> +	line[strcspn(line, "\n")] = '\0';
> +	strncpy(buf, line, MAX_BUF);
> +	return normalize_path(buf, line);
> +}
> +
> +int addr2line_cleanup(void)
> +{
> +	int status;
> +
> +	if (addr2line_pid != -1) {
> +		kill(addr2line_pid, SIGKILL);
> +		waitpid(addr2line_pid, &status, 0);
> +		fclose(a2l_stdin);
> +		fclose(a2l_stdout);
> +		addr2line_pid = -1;
> +	}
> +
> +	return 1;
> +}
> +
> +static char *find_executable(const char *command)
> +{
> +	char *path_env = getenv("PATH");
> +	char *executable_path;
> +	char *path_copy;
> +	char *path;
> +	int n;
> +
> +	if (!path_env)
> +		return NULL;
> +
> +	path_copy = strdup(path_env);
> +	if (!path_copy)
> +		return NULL;
> +
> +	path = strtok(path_copy, ":");
> +	while (path) {
> +		n = snprintf(0, 0, "%s/%s", path, command);
> +		executable_path = (char *)malloc(n + 1);
> +		snprintf(executable_path, n + 1, "%s/%s", path, command);
> +		if (access(executable_path, X_OK) == 0) {
> +			free(path_copy);
> +			return executable_path;
> +		}
> +
> +	path = strtok(NULL, ":");
> +	free(executable_path);
> +	executable_path = NULL;

nit: mis-indentation?

> +	}
> +
> +	free(path_copy);
> +	if (executable_path)
> +		free(executable_path);
> +	return NULL;
> +}
> +
> +const char *get_addr2line(int mode)
> +{
> +	char *buf = "";
> +
> +	switch (mode) {
> +	case A2L_CROSS:
> +		buf = getenv("CROSS_COMPILE");
> +		memcpy(addr2line_cmd, buf, strlen(buf));
> +	case A2L_DEFAULT:
> +		memcpy(addr2line_cmd + strlen(buf), ADDR2LINE, strlen(ADDR2LINE));
> +		buf = find_executable(addr2line_cmd);
> +		if (buf) {
> +			memcpy(addr2line_cmd, buf, strlen(buf));
> +			free(buf);
> +		}
> +		return addr2line_cmd;
> +	case A2L_LLVM:
> +	default:
> +		return NULL;
> +	}
> +}
> +
> +char *get_vmlinux(char *input)
> +{
> +	const char *match_string1 = ".syms";
> +	const char *match_string2 = ".tmp_vmlinux.kallsyms";
> +	char *result = NULL;
> +	char *match_pos;
> +
> +	match_pos = strstr(input, match_string1);
> +	if (!match_pos)
> +		return NULL;
> +
> +	match_pos = strstr(input, match_string2);
> +	if (!match_pos)
> +		return NULL;
> +
> +	result = strdup(input);
> +	match_pos = strstr(result, match_string1);
> +	*match_pos = '\0';
> +	return result;
> +}
> diff --git a/scripts/kas_alias/a2l.h b/scripts/kas_alias/a2l.h
> new file mode 100644
> index 000000000000..ca6419229dde
> --- /dev/null
> +++ b/scripts/kas_alias/a2l.h
> @@ -0,0 +1,32 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef A2L_H
> +#define A2L_H
> +#include <stdint.h>
> +
> +#define ADDR2LINE "addr2line"
> +#define ADDR2LINE_ARGS "-fe"
> +//#define VMLINUX "vmlinux"

Nit: this should be removed if it is not used.

> +#define MAX_BUF 4096
> +#define MAX_CMD_LEN 256
> +#define P_READ 0
> +#define P_WRITE 1
> +#define A2L_DEFAULT 1
> +#define A2L_CROSS 2
> +#define A2L_LLVM 3
> +#define A2L_MAKE_VALUE 2
> +
> +extern int addr2line_pid;
> +extern int a2l_in[2];
> +extern int a2l_out[2];
> +extern char line[MAX_BUF];
> +extern char vmlinux_path[MAX_BUF];
> +extern char addr2line_cmd[MAX_CMD_LEN];
> +
> +int addr2line_init(const char *cmd, const char *vmlinux);
> +char *addr2line_get_lines(uint64_t address);
> +int addr2line_cleanup(void);
> +const char *remove_subdir(const char *home, const char *f_path);
> +const char *get_addr2line(int mode);
> +char *get_vmlinux(char *input);
> +
> +#endif
> diff --git a/scripts/kas_alias/duplicates_list.c b/scripts/kas_alias/duplicates_list.c
> new file mode 100644
> index 000000000000..e7a3d2917937
> --- /dev/null
> +++ b/scripts/kas_alias/duplicates_list.c
> @@ -0,0 +1,70 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <stdint.h>
> +#include <stdio.h>
> +#include <string.h>
> +#include <stdlib.h>
> +#include <stdbool.h>
> +
> +#include "item_list.h"
> +#include "duplicates_list.h"
> +

/* The item list must be sorted. */

I think we can find the duplicated symbol without sorting the list,
but such implementation level optimization will be done later.

> +struct duplicate_item *find_duplicates(struct item *list)
> +{
> +	struct duplicate_item *current_duplicate = NULL;
> +	struct duplicate_item *duplicates = NULL;
> +	struct duplicate_item *new_duplicate;
> +	struct item *current_item = list;
> +	bool prev_was_duplicate = false;
> +	struct item *prev_item = NULL;
> +
> +	while (current_item) {
> +		if ((prev_item && (strcmp(current_item->symb_name, prev_item->symb_name) == 0)) ||
> +		    prev_was_duplicate) {
> +			if (!duplicates) {
> +				duplicates = malloc(sizeof(struct duplicate_item));
> +				if (!duplicates)
> +					return NULL;
> +
> +				duplicates->original_item = prev_item;
> +				duplicates->next = NULL;
> +				current_duplicate = duplicates;
> +			} else {
> +				new_duplicate = malloc(sizeof(struct duplicate_item));
> +				if (!new_duplicate) {
> +					free_duplicates(&duplicates);
> +					return NULL;
> +				}
> +
> +				new_duplicate->original_item = prev_item;
> +				new_duplicate->next = NULL;
> +				current_duplicate->next = new_duplicate;
> +				current_duplicate = new_duplicate;
> +
> +				if ((strcmp(current_item->symb_name, prev_item->symb_name) != 0) &&
> +				    (prev_was_duplicate))
> +					prev_was_duplicate = false;
> +				else
> +					prev_was_duplicate = true;
> +			}
> +		}
> +
> +		prev_item = current_item;
> +		current_item = current_item->next;
> +	}
> +
> +	return duplicates;
> +}
> +
> +void free_duplicates(struct duplicate_item **duplicates)
> +{
> +	struct duplicate_item *duplicates_iterator = *duplicates;
> +	struct duplicate_item *app;
> +
> +	while (duplicates_iterator) {
> +		app = duplicates_iterator;
> +		duplicates_iterator = duplicates_iterator->next;
> +		free(app);
> +	}
> +
> +	*duplicates = NULL;
> +}
> diff --git a/scripts/kas_alias/duplicates_list.h b/scripts/kas_alias/duplicates_list.h
> new file mode 100644
> index 000000000000..76aa73e584bc
> --- /dev/null
> +++ b/scripts/kas_alias/duplicates_list.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef DUPLICATES_LIST_H
> +#define DUPLICATES_LIST_H
> +
> +#include "item_list.h"
> +
> +struct duplicate_item {
> +	struct item *original_item;
> +	struct duplicate_item *next;
> +};
> +
> +struct duplicate_item *find_duplicates(struct item *list);
> +void free_duplicates(struct duplicate_item **duplicates);
> +
> +#endif
> diff --git a/scripts/kas_alias/item_list.c b/scripts/kas_alias/item_list.c
> new file mode 100644
> index 000000000000..48f2e525592a
> --- /dev/null
> +++ b/scripts/kas_alias/item_list.c
> @@ -0,0 +1,230 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <stdint.h>
> +#include <string.h>
> +#include <stdbool.h>
> +#include <assert.h>
> +#include "item_list.h"
> +
> +#define CHECK_ORDER_BY_ADDRESS(sort_by, current, temp, op) \
> +	((sort_by) == BY_ADDRESS && (current)->addr op (temp)->addr)
> +#define CHECK_ORDER_BY_NAME(sort_by, current, temp, op) \
> +	((sort_by) == BY_NAME && strcmp((current)->symb_name, (temp)->symb_name) op 0)
> +
> +struct item *list_index[96] = {0};
> +
> +void build_index(struct item *list)
> +{
> +	char current_first_letter = ' ';
> +	struct item *current = list;
> +
> +	while (current) {
> +		if (current->symb_name[0] != current_first_letter) {
> +			current_first_letter = current->symb_name[0];
> +			list_index[current_first_letter - 32] = current;
> +		}
> +		current = current->next;
> +	}
> +}
> +
> +struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr)
> +{
> +	struct item *new_item;
> +	struct item *current;
> +
> +	new_item = malloc(sizeof(struct item));
> +	if (!new_item)
> +		return NULL;
> +
> +	strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> +	new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> +	new_item->addr = addr;
> +	new_item->stype = stype;
> +	new_item->next = NULL;
> +
> +	if (!(*list)) {
> +		*list = new_item;
> +	} else {
> +		current = *list;
> +		while (current->next)
> +			current = current->next;
> +
> +		current->next = new_item;
> +	}
> +	return new_item;
> +}
> +
> +void sort_list(struct item **list, int sort_by)
> +{
> +	struct item *current = *list;
> +	struct item *sorted = NULL;
> +	struct item *next_item;
> +	struct item *temp;
> +
> +	if (!(*list) || !((*list)->next))
> +		return;
> +
> +	while (current) {
> +		next_item = current->next;
> +		if (!sorted ||
> +		    (CHECK_ORDER_BY_ADDRESS(sort_by, current, sorted, <) ||
> +		    CHECK_ORDER_BY_NAME(sort_by, current, sorted, >=))) {
> +			current->next = sorted;
> +			sorted = current;
> +		} else {
> +			temp = sorted;
> +			while (temp->next &&
> +			       (CHECK_ORDER_BY_ADDRESS(sort_by, current, temp->next, >=) ||
> +			       CHECK_ORDER_BY_NAME(sort_by, current, temp->next, >=)))
> +				temp = temp->next;
> +
> +			current->next = temp->next;
> +			temp->next = current;
> +		}
> +		current = next_item;
> +	}
> +
> +	*list = sorted;
> +}
> +
> +struct item *merge(struct item *left, struct item *right, int sort_by)
> +{
> +	struct item *current = NULL;
> +	struct item *result = NULL;
> +
> +	if (!left)
> +		return right;
> +	if (!right)
> +		return left;
> +
> +	if (sort_by == BY_NAME) {
> +		if (strcmp(left->symb_name, right->symb_name) <= 0) {
> +			result = left;
> +			left = left->next;
> +		} else {
> +			result = right;
> +			right = right->next;
> +		}
> +	} else {
> +		if (sort_by == BY_ADDRESS) {
> +			if (left->addr <= right->addr) {
> +				result = left;
> +				left = left->next;
> +			} else {
> +				result = right;
> +				right = right->next;
> +			}
> +		}
> +	}
> +
> +	current = result;
> +
> +	while (left && right) {
> +		if (sort_by == BY_NAME) {
> +			if (strcmp(left->symb_name, right->symb_name) <= 0) {
> +				current->next = left;
> +				left = left->next;
> +			} else {
> +				current->next = right;
> +				right = right->next;
> +			}
> +		} else {
> +			if (sort_by == BY_ADDRESS) {
> +				if (left->addr <= right->addr) {
> +					current->next = left;
> +					left = left->next;
> +				} else {
> +					current->next = right;
> +					right = right->next;
> +				}
> +			}
> +		}
> +
> +		current = current->next;
> +	}
> +
> +	if (left) {
> +		current->next = left;
> +	} else {
> +		if (right)
> +			current->next = right;
> +	}
> +
> +	return result;
> +}
> +
> +struct item *merge_sort(struct item *head, int sort_by)
> +{
> +	struct item *right;
> +	struct item *slow;
> +	struct item *fast;
> +	struct item *left;
> +
> +	if (!head || !head->next)
> +		return head;
> +
> +	slow = head;
> +	fast = head->next;
> +
> +	while (fast && fast->next) {
> +		slow = slow->next;
> +		fast = fast->next->next;
> +	}
> +
> +	left = head;
> +	right = slow->next;
> +	slow->next = NULL;
> +
> +	left = merge_sort(left, sort_by);
> +	right = merge_sort(right, sort_by);
> +
> +	return merge(left, right, sort_by);
> +}
> +
> +void sort_list_m(struct item **head, int sort_by)
> +{
> +	if (!(*head) || !((*head)->next))
> +		return;
> +
> +	*head = merge_sort(*head, sort_by);
> +}
> +
> +int insert_after(struct item *list, const uint64_t search_addr,
> +		 const char *name, uint64_t addr, char stype)
> +{
> +	struct item *new_item;
> +	struct item *current;
> +	int ret = 0;
> +
> +	current = (list_index[name[0] - 32]) ? list_index[name[0] - 32] : list;
> +	while (current) {
> +		if (current->addr == search_addr) {
> +			new_item = malloc(sizeof(struct item));
> +			if (!new_item)
> +				return ret;
> +			strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> +			new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> +			new_item->addr = addr;
> +			new_item->stype = stype;
> +			new_item->next = current->next;
> +			current->next = new_item;
> +			ret = 1;
> +			break;
> +		}
> +		current = current->next;
> +	}
> +	return ret;
> +}
> +
> +void free_items(struct item **head)
> +{
> +	struct item *app, *item_iterator = *head;
> +
> +	while (item_iterator) {
> +		app = item_iterator;
> +		item_iterator = item_iterator->next;
> +		free(app);
> +	}
> +	*head = NULL;
> +}
> diff --git a/scripts/kas_alias/item_list.h b/scripts/kas_alias/item_list.h
> new file mode 100644
> index 000000000000..b4891cb088ee
> --- /dev/null
> +++ b/scripts/kas_alias/item_list.h
> @@ -0,0 +1,26 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef ITEM_LIST_H
> +#define ITEM_LIST_H
> +#include <stdint.h>
> +
> +#define MAX_NAME_SIZE 256
> +#define BY_ADDRESS 1
> +#define BY_NAME 2
> +
> +struct item {
> +	char		symb_name[MAX_NAME_SIZE];
> +	uint64_t	addr;
> +	char		stype;
> +	struct item	*next;
> +};
> +
> +void build_index(struct item *list);
> +struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr);
> +void sort_list(struct item **list, int sort_by);
> +struct item *merge(struct item *left, struct item *right, int sort_by);
> +struct item *merge_sort(struct item *head, int sort_by);
> +void sort_list_m(struct item **head, int sort_by);
> +int insert_after(struct item *list, const uint64_t search_addr,
> +		 const char *name, uint64_t addr, char stype);
> +void free_items(struct item **head);
> +#endif
> diff --git a/scripts/kas_alias/kas_alias.c b/scripts/kas_alias/kas_alias.c
> new file mode 100644
> index 000000000000..532aeb39f851
> --- /dev/null
> +++ b/scripts/kas_alias/kas_alias.c
> @@ -0,0 +1,217 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <stdint.h>
> +#include <unistd.h>
> +#include <string.h>
> +#include <stdbool.h>
> +#include <stdarg.h>
> +#include <regex.h>
> +
> +#include "item_list.h"
> +#include "duplicates_list.h"
> +#include "a2l.h"
> +
> +#define SYMB_IS_TEXT(s) ((((s)->stype) == 't') ||  (((s)->stype) == 'T'))
> +#define SYMB_IS_DATA(s) ((((s)->stype) == 'b') ||  (((s)->stype) == 'B') || \
> +			 (((s)->stype) == 'd') ||  (((s)->stype) == 'D') || \
> +			 (((s)->stype) == 'r') ||  (((s)->stype) == 'R'))
> +#ifdef CONFIG_KALLSYMS_ALIAS_DATA
> +#define SYMB_NEEDS_ALIAS(s) (SYMB_IS_TEXT(s) || SYMB_IS_DATA(s))
> +#else
> +#define SYMB_NEEDS_ALIAS(s) SYMB_IS_TEXT(s)
> +#endif
> +#define FNOMATCH 0
> +#define FMATCH 1
> +#define EREGEX 2
> +
> +const char *ignore_regex[] = {
> +	"^__cfi_.*$",				// __cfi_ preamble
> +#ifndef CONFIG_KALLSYMS_ALIAS_DATA_ALL
> +	"^_*TRACE_SYSTEM.*$",
> +	"^__already_done\\.[0-9]+$",		// Call a function once data
> +	"^___tp_str\\.[0-9]+$",
> +	"^___done\\.[0-9]+$",
> +	"^__print_once\\.[0-9]+$",
> +	"^_rs\\.[0-9]+$",
> +	"^__compound_literal\\.[0-9]+$",
> +	"^___once_key\\.[0-9]+$",
> +	"^__func__\\.[0-9]+$",
> +	"^__msg\\.[0-9]+$",
> +	"^CSWTCH\\.[0-9]+$",
> +	"^__flags\\.[0-9]+$",
> +	"^__wkey.*$",
> +	"^__mkey.*$",
> +	"^__key.*$",
> +#endif
> +	"^__pfx_.*$"				// NOP-padding
> +};
> +
> +int suffix_serial;
> +
> +static inline void verbose_msg(bool verbose, const char *fmt, ...)
> +{
> +	va_list args;
> +
> +	va_start(args, fmt);
> +	if (verbose)
> +		printf(fmt, args);
> +
> +	va_end(args);
> +}
> +
> +static void create_suffix(const char *name, char *output_suffix)
> +{
> +	sprintf(output_suffix, "%s__alias__%d", name, suffix_serial++);
> +}
> +
> +static void create_file_suffix(const char *name, uint64_t address, char *output_suffix, char *cwd)
> +{
> +	const char *f_path;
> +	char *buf;
> +	int i = 0;
> +
> +	buf = addr2line_get_lines(address);
> +	f_path = remove_subdir(cwd, buf);
> +	if (f_path) {
> +		sprintf(output_suffix, "%s@%s", name, f_path);
> +		while (*(output_suffix + i) != '\0') {
> +			switch (*(output_suffix + i)) {
> +			case '/':
> +			case ':':
> +			case '.':

This is not enough because file path will accept more than that.
E.g. '+', '&', '-'. 
So I think we should check it by '!isalnum()'. (allow-list method)

> +				*(output_suffix + i) = '_';
> +				break;
> +			default:
> +			}
> +		i++;
> +		}
> +	} else {
> +		create_suffix(name, output_suffix);
> +	}
> +}
> +
> +static int filter_symbols(char *symbol, const char **ignore_list, int regex_no)
> +{
> +	regex_t regex;
> +	int res, i;
> +
> +	for (i = 0; i < regex_no; i++) {
> +		res = regcomp(&regex, ignore_list[i], REG_EXTENDED);
> +		if (res)
> +			return -EREGEX;
> +
> +		res = regexec(&regex, symbol, 0, NULL, 0);
> +		regfree(&regex);
> +		switch (res) {
> +		case 0:
> +			return FMATCH;
> +		case REG_NOMATCH:
> +			break;
> +		default:
> +			return -EREGEX;
> +		}
> +	}
> +
> +	return FNOMATCH;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	char t, sym_name[MAX_NAME_SIZE], new_name[MAX_NAME_SIZE + 15];
> +	struct duplicate_item  *duplicate_iterator;
> +	struct duplicate_item *duplicate;
> +	struct item *head = {NULL};
> +	bool need_2_process = true;
> +	struct item *last = {NULL};
> +	struct item  *current;
> +	int verbose_mode = 0;
> +	uint64_t address;
> +	FILE *fp;
> +	int res;
> +
> +	if (argc < 2 || argc > 3) {
> +		printf("Usage: %s <nmfile> [-verbose]\n", argv[0]);
> +		return 1;
> +	}
> +
> +	if (argc == 3 && strcmp(argv[2], "-verbose") == 0)
> +		verbose_mode = 1;
> +
> +	verbose_msg(verbose_mode, "Scanning nm data(%s)\n", argv[1]);
> +
> +	fp = fopen(argv[1], "r");
> +	if (!fp) {
> +		printf("Can't open input file.\n");
> +		return 1;
> +	}
> +
> +	if (!addr2line_init(get_addr2line(A2L_DEFAULT), get_vmlinux(argv[1])))
> +		return 1;
> +
> +	while (fscanf(fp, "%lx %c %99s\n", &address, &t, sym_name) == 3) {
> +		if (strstr(sym_name, "@_")) {
> +			if (verbose_mode && need_2_process)
> +				printf("Already processed\n");
> +			need_2_process = false;
> +			}
> +		last = add_item(&last, sym_name, t, address);
> +		if (!last) {
> +			printf("Error in allocate memory\n");
> +			free_items(&head);
> +			return 1;
> +		}
> +
> +		if (!head)
> +			head = last;
> +	}
> +
> +	fclose(fp);
> +
> +	if (need_2_process) {
> +		verbose_msg(verbose_mode, "Sorting nm data\n");
> +		sort_list_m(&head, BY_NAME);
> +		verbose_msg(verbose_mode, "Scanning nm data for duplicates\n");
> +		duplicate = find_duplicates(head);
> +		if (!duplicate) {
> +			printf("Error in duplicates list\n");
> +			return 1;
> +		}
> +
> +		verbose_msg(verbose_mode, "Applying suffixes\n");
> +		build_index(head);
> +		duplicate_iterator = duplicate;
> +		while (duplicate_iterator) {
> +			res = filter_symbols(duplicate_iterator->original_item->symb_name,
> +					     ignore_regex, sizeof(ignore_regex) /
> +					     sizeof(ignore_regex[0]));
> +			if (res != FMATCH &&
> +			    SYMB_NEEDS_ALIAS(duplicate_iterator->original_item)) {
> +				if (res < 0)
> +					return 1;
> +
> +				create_file_suffix(duplicate_iterator->original_item->symb_name,
> +						   duplicate_iterator->original_item->addr,
> +						   new_name, vmlinux_path);
> +				if (!insert_after(head, duplicate_iterator->original_item->addr,
> +						  new_name, duplicate_iterator->original_item->addr,
> +						  duplicate_iterator->original_item->stype))
> +					return 1;
> +			}
> +
> +			duplicate_iterator = duplicate_iterator->next;
> +		}
> +
> +		sort_list_m(&head, BY_ADDRESS);
> +	}
> +	current = head;
> +	while (current) {
> +		printf("%08lx %c %s\n", current->addr, current->stype, current->symb_name);
> +		current = current->next;
> +	}
> +
> +	free_items(&head);
> +	free_duplicates(&duplicate);
> +	addr2line_cleanup();
> +	return 0;
> +}
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index a432b171be82..cacf60b597ce 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -89,8 +89,9 @@ vmlinux_link()
>  
>  	ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
>  
> -	# The kallsyms linking does not need debug symbols included.
> -	if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> +	# The kallsyms linking does not need debug symbols included, unless the KALLSYMS_ALIAS.
> +	if [ ! is_enabled CONFIG_KALLSYMS_ALIAS ] && \
> +	    [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
>  		ldflags="${ldflags} ${wl}--strip-debug"
>  	fi
>  
> @@ -161,7 +162,11 @@ kallsyms()
>  	fi
>  
>  	info KSYMS ${2}
> -	scripts/kallsyms ${kallsymopt} ${1} > ${2}
> +	if is_enabled CONFIG_KALLSYMS_ALIAS; then
> +		ALIAS=".alias"
> +		scripts/kas_alias/kas_alias ${1} >${1}${ALIAS}
> +		fi

Nit: wrong indentation.
And ALIAS is not defined if CONFIG_KALLSYMS_ALIAS=n.


> +	scripts/kallsyms ${kallsymopt} ${1}${ALIAS} > ${2}
>  }
>  
>  # Perform one step in kallsyms generation, including temporary linking of
> -- 
> 2.34.1
> 


Thank you,

-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-08-28  8:04 [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms Alessandro Carminati (Red Hat)
  2023-08-29 14:51 ` Francis Laniel
  2023-08-30  6:00 ` Masami Hiramatsu
@ 2023-09-01  5:31 ` Masahiro Yamada
  2023-09-02  7:27   ` Alessandro Carminati
  2023-09-02  6:36 ` Masahiro Yamada
  2023-09-11 14:21 ` Alexander Lobakin
  4 siblings, 1 reply; 16+ messages in thread
From: Masahiro Yamada @ 2023-09-01  5:31 UTC (permalink / raw)
  To: Alessandro Carminati (Red Hat)
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Luis Chamberlain, Nathan Chancellor,
	Nick Desaulniers, Nicolas Schier, Alexander Lobakin, Nick Alcock,
	Kris Van Hees, Eugene Loh, Francis Laniel, Viktor Malik,
	linux-kbuild, linux-kernel, linux-trace-kernel, live-patching

On Mon, Aug 28, 2023 at 8:45 PM Alessandro Carminati (Red Hat)
<alessandro.carminati@gmail.com> wrote:
>
> From: Alessandro Carminati <alessandro.carminati@gmail.com>
>
> It is not uncommon for drivers or modules related to similar peripherals
> to have symbols with the exact same name.
> While this is not a problem for the kernel's binary itself, it becomes an
> issue when attempting to trace or probe specific functions using
> infrastructure like ftrace or kprobe.
>
> The tracing subsystem relies on the `nm -n vmlinux` output, which provides
> symbol information from the kernel's ELF binary. However, when multiple
> symbols share the same name, the standard nm output does not differentiate
> between them. This can lead to confusion and difficulty when trying to
> probe the intended symbol.
>
>  ~ # cat /proc/kallsyms | grep " name_show"
>  ffffffff8c4f76d0 t name_show
>  ffffffff8c9cccb0 t name_show
>  ffffffff8cb0ac20 t name_show
>  ffffffff8cc728c0 t name_show
>  ffffffff8ce0efd0 t name_show
>  ffffffff8ce126c0 t name_show
>  ffffffff8ce1dd20 t name_show
>  ffffffff8ce24e70 t name_show
>  ffffffff8d1104c0 t name_show
>  ffffffff8d1fe480 t name_show
>
> **kas_alias** addresses this challenge by extending the symbol names with
> unique suffixes during the kernel build process.
> The newly created aliases for these duplicated symbols are unique names
> that can be fed to the ftracefs interface. By doing so, it enables
> previously unreachable symbols to be probed.
>
>  ~ # cat /proc/kallsyms | grep " name_show"
>  ffffffff974f76d0 t name_show
>  ffffffff974f76d0 t name_show__alias__6340
>  ffffffff979cccb0 t name_show
>  ffffffff979cccb0 t name_show__alias__6341
>  ffffffff97b0ac20 t name_show
>  ffffffff97b0ac20 t name_show__alias__6342
>  ffffffff97c728c0 t name_show
>  ffffffff97c728c0 t name_show__alias__6343
>  ffffffff97e0efd0 t name_show
>  ffffffff97e0efd0 t name_show__alias__6344
>  ffffffff97e126c0 t name_show
>  ffffffff97e126c0 t name_show__alias__6345
>  ffffffff97e1dd20 t name_show
>  ffffffff97e1dd20 t name_show__alias__6346
>  ffffffff97e24e70 t name_show
>  ffffffff97e24e70 t name_show__alias__6347
>  ffffffff981104c0 t name_show
>  ffffffff981104c0 t name_show__alias__6348
>  ffffffff981fe480 t name_show
>  ffffffff981fe480 t name_show__alias__6349
>
>  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
>  > >/sys/kernel/tracing/kprobe_events
>  ~ # cat /sys/kernel/tracing/kprobe_events
>  p:kprobes/evnt1 name_show__alias__6349
>
> Changes from v1:
> - Integrated changes requested by Masami to exclude symbols with prefixes
>   "_cfi" and "_pfx".
> - Introduced a small framework to handle patterns that need to be excluded
>   from the alias production.
> - Excluded other symbols using the framework.
> - Introduced the ability to discriminate between text and data symbols.
> - Added two new config symbols in this version: CONFIG_KALLSYMS_ALIAS_DATA,
>   which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
>   excludes all filters and provides an alias for each duplicated symbol.
>
> https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gmail.com/
>
> Changes from v2:
> - Alias tags are created by querying DWARF information from the vmlinux.
> - The filename + line number is normalized and appended to the original name.
> - The tag begins with '@' to indicate the symbol source.
> - Not a change, but worth mentioning, since the alias is added to the existing
>   list, the old duplicated name is preserved, and the livepatch way of dealing
>   with duplicates is maintained.
> - Acknowledging the existence of scenarios where inlined functions declared in
>   header files may result in multiple copies due to compiler behavior, though
>    it is not actionable as it does not pose an operational issue.
> - Highlighting a single exception where the same name refers to different
>   functions: the case of "compat_binfmt_elf.c," which directly includes
>   "binfmt_elf.c" producing identical function copies in two separate
>   modules.
>
> sample from new v3
>
>  ~ # cat /proc/kallsyms | grep gic_mask_irq
>  ffffd0b03c04dae4 t gic_mask_irq
>  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
>  ffffd0b03c050960 t gic_mask_irq
>  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
>  ~ #
>
> https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gmail.com/
>
> Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> ---
>  init/Kconfig                        |  36 ++++
>  scripts/Makefile                    |   4 +
>  scripts/kas_alias/Makefile          |   4 +
>  scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
>  scripts/kas_alias/a2l.h             |  32 ++++
>  scripts/kas_alias/duplicates_list.c |  70 ++++++++
>  scripts/kas_alias/duplicates_list.h |  15 ++
>  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
>  scripts/kas_alias/item_list.h       |  26 +++
>  scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
>  scripts/link-vmlinux.sh             |  11 +-
>  11 files changed, 910 insertions(+), 3 deletions(-)
>  create mode 100644 scripts/kas_alias/Makefile
>  create mode 100644 scripts/kas_alias/a2l.c
>  create mode 100644 scripts/kas_alias/a2l.h
>  create mode 100644 scripts/kas_alias/duplicates_list.c
>  create mode 100644 scripts/kas_alias/duplicates_list.h
>  create mode 100644 scripts/kas_alias/item_list.c
>  create mode 100644 scripts/kas_alias/item_list.h
>  create mode 100644 scripts/kas_alias/kas_alias.c
>
> diff --git a/init/Kconfig b/init/Kconfig
> index f7f65af4ee12..bc69fcd9cbc8 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1737,6 +1737,42 @@ config KALLSYMS_BASE_RELATIVE
>           time constants, and no relocation pass is required at runtime to fix
>           up the entries based on the runtime load address of the kernel.
>
> +config KALLSYMS_ALIAS
> +       bool "Produces alias for duplicated symbols" if EXPERT
> +       depends on KALLSYMS && (DEBUG_INFO_DWARF4 || DEBUG_INFO_DWARF5)


You can simplify this to


           depends on KALLSYMS && DEBUG_INFO

I re-checked the commit log of
a66049e2cf0ef166dba5bafdbb3062287fc965ad

It says "GCC since ~4.8 has defaulted to DWARF v4
implicitly, and GCC 11 has bumped this to v5"


When DEBUG_INFO is enabled, the dwarf version is 4 or 5.


Presumably, your code does not work with DEBUG_INFO_SPLIT


   depends on KALLSYMS && DEBUG_INFO && !DEBUG_INFO_SPLIT




> diff --git a/scripts/kas_alias/a2l.c b/scripts/kas_alias/a2l.c
> new file mode 100644
> index 000000000000..a9692ac30180
> --- /dev/null
> +++ b/scripts/kas_alias/a2l.c
> @@ -0,0 +1,268 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <sys/types.h>
> +#include <sys/wait.h>
> +#include <string.h>


<string.h> is included twice.

I always sort include directives alphabetically
to avoid such a mistake.






> +#include <stdint.h>
> +#include <stdbool.h>
> +
> +#include "a2l.h"
> +
> +int addr2line_pid = -1;
> +int a2l_in[2];
> +int a2l_out[2];
> +char line[MAX_BUF];
> +char vmlinux_path[MAX_BUF];
> +char addr2line_cmd[MAX_CMD_LEN];
> +FILE *a2l_stdin, *a2l_stdout;
> +
> +static char *normalize_path(const char *input_path, char *output_path)
> +{
> +       char *prev_token = NULL;
> +       char *delimiter = "/";
> +       char inbuf[MAX_BUF];
> +       char *token;
> +       char *pos;
> +
> +       memset(inbuf, 0, MAX_BUF);
> +       *output_path = '\0';
> +       strncpy(inbuf, input_path, MAX_BUF);
> +       if (!input_path || !output_path || strlen(input_path) == 0)
> +               return NULL;
> +
> +       token = strtok(inbuf, delimiter);
> +       while (token) {
> +               if (strcmp(token, "..") == 0 && prev_token) {
> +                       pos = strrchr(output_path, '/');
> +                       if (pos)
> +                               *pos = '\0';
> +
> +               } else if (strcmp(token, ".") != 0) {
> +                       strcat(output_path, "/");
> +                       strcat(output_path, token);
> +               }
> +
> +               prev_token = token;
> +               token = strtok(NULL, delimiter);
> +       }
> +
> +       return output_path;
> +}
> +
> +static void path_of(const char *full_path, char *path)
> +{
> +       const char *last_slash = strrchr(full_path, '/');
> +       size_t path_length;
> +       char cwd[MAX_BUF];
> +
> +       if (!last_slash) {
> +               if (getcwd(cwd, sizeof(cwd)))
> +                       strcpy(path, cwd);
> +               else
> +                       strcpy(path, ".");
> +       } else {
> +               path_length = last_slash - full_path;
> +               strncpy(path, full_path, path_length);
> +               path[path_length] = '\0';
> +       }
> +}
> +
> +static bool file_exists(const char *file_path)
> +{
> +       FILE *file;
> +
> +       file = fopen(file_path, "r");
> +       if (file) {
> +               fclose(file);
> +               return true;
> +       }
> +       return false;
> +}
> +
> +int addr2line_init(const char *cmd, const char *vmlinux)
> +{
> +       if ((!file_exists(cmd)) || (!file_exists(vmlinux))) {
> +               printf("file not found\n");
> +               return 0;
> +               }
> +
> +       path_of(vmlinux, vmlinux_path);
> +       if (pipe(a2l_in) == -1) {
> +               printf("Failed to create pipe\n");
> +               return 0;
> +       }
> +
> +       if (pipe(a2l_out) == -1) {
> +               printf("Failed to create pipe\n");
> +               return 0;
> +       }
> +
> +       addr2line_pid = fork();
> +       if (addr2line_pid == -1) {
> +               printf("Failed to fork process\n");
> +               close(a2l_in[P_READ]);
> +               close(a2l_in[P_WRITE]);
> +               close(a2l_out[P_READ]);
> +               close(a2l_out[P_WRITE]);
> +               return 0;
> +       }
> +
> +       if (addr2line_pid == 0) {
> +               dup2(a2l_in[P_READ], 0);
> +               dup2(a2l_out[P_WRITE], 1);
> +               close(a2l_in[P_WRITE]);
> +               close(a2l_out[P_READ]);
> +
> +               execlp(cmd, cmd, ADDR2LINE_ARGS, vmlinux, NULL);
> +
> +               printf("Failed to execute addr2line command\n");
> +               exit(1);
> +       } else {
> +               close(a2l_in[P_READ]);
> +               close(a2l_out[P_WRITE]);
> +       }
> +
> +       a2l_stdin = fdopen(a2l_in[P_WRITE], "w");
> +       if (!a2l_stdin) {
> +               printf("Failed to open pipe a2l_in\n");
> +               return 0;
> +       }
> +
> +       a2l_stdout = fdopen(a2l_out[P_READ], "r");
> +       if (!a2l_stdout) {
> +               printf("Failed to open pipe a2l_out\n");
> +               fclose(a2l_stdin);
> +               return 0;
> +       }
> +
> +       return 1;
> +}
> +
> +const char *remove_subdir(const char *home, const char *f_path)
> +{
> +       int i = 0;
> +
> +       while (*(home + i) == *(f_path + i))
> +               i++;
> +
> +       return (strlen(home) != i) ? NULL : f_path + i;
> +}
> +
> +char *addr2line_get_lines(uint64_t address)
> +{
> +       char buf[MAX_BUF];
> +
> +       fprintf(a2l_stdin, "%08lx\n", address);
> +       fflush(a2l_stdin);
> +
> +       if (!fgets(line, sizeof(line), a2l_stdout)) {
> +               printf("Failed to read lines from addr2line\n");
> +               return NULL;
> +       }
> +
> +       if (!fgets(line, sizeof(line), a2l_stdout)) {
> +               printf("Failed to read lines from addr2line\n");
> +               return NULL;
> +       }
> +
> +       line[strcspn(line, "\n")] = '\0';
> +       strncpy(buf, line, MAX_BUF);
> +       return normalize_path(buf, line);
> +}
> +
> +int addr2line_cleanup(void)
> +{
> +       int status;
> +
> +       if (addr2line_pid != -1) {
> +               kill(addr2line_pid, SIGKILL);
> +               waitpid(addr2line_pid, &status, 0);
> +               fclose(a2l_stdin);
> +               fclose(a2l_stdout);
> +               addr2line_pid = -1;
> +       }
> +
> +       return 1;
> +}
> +
> +static char *find_executable(const char *command)
> +{
> +       char *path_env = getenv("PATH");
> +       char *executable_path;
> +       char *path_copy;
> +       char *path;
> +       int n;
> +
> +       if (!path_env)
> +               return NULL;
> +
> +       path_copy = strdup(path_env);
> +       if (!path_copy)
> +               return NULL;
> +
> +       path = strtok(path_copy, ":");
> +       while (path) {
> +               n = snprintf(0, 0, "%s/%s", path, command);
> +               executable_path = (char *)malloc(n + 1);
> +               snprintf(executable_path, n + 1, "%s/%s", path, command);
> +               if (access(executable_path, X_OK) == 0) {
> +                       free(path_copy);
> +                       return executable_path;
> +               }
> +
> +       path = strtok(NULL, ":");
> +       free(executable_path);
> +       executable_path = NULL;
> +       }
> +
> +       free(path_copy);
> +       if (executable_path)
> +               free(executable_path);
> +       return NULL;
> +}
> +
> +const char *get_addr2line(int mode)
> +{
> +       char *buf = "";
> +
> +       switch (mode) {
> +       case A2L_CROSS:
> +               buf = getenv("CROSS_COMPILE");
> +               memcpy(addr2line_cmd, buf, strlen(buf));

Dangerous code.
It is easy to cause a buffer overrun by setting a long string to CROSS_COMPILE.


I am fine with adding ADDR2LINE in the top Makefile.





> +       case A2L_DEFAULT:
> +               memcpy(addr2line_cmd + strlen(buf), ADDR2LINE, strlen(ADDR2LINE));
> +               buf = find_executable(addr2line_cmd);
> +               if (buf) {
> +                       memcpy(addr2line_cmd, buf, strlen(buf));
> +                       free(buf);
> +               }
> +               return addr2line_cmd;
> +       case A2L_LLVM:
> +       default:
> +               return NULL;
> +       }
> +}
> +
> +char *get_vmlinux(char *input)
> +{
> +       const char *match_string1 = ".syms";
> +       const char *match_string2 = ".tmp_vmlinux.kallsyms";
> +       char *result = NULL;
> +       char *match_pos;
> +
> +       match_pos = strstr(input, match_string1);
> +       if (!match_pos)
> +               return NULL;
> +
> +       match_pos = strstr(input, match_string2);
> +       if (!match_pos)
> +               return NULL;
> +
> +       result = strdup(input);
> +       match_pos = strstr(result, match_string1);
> +       *match_pos = '\0';
> +       return result;
> +}

Tedious code to compute the vmlinux name.
You can pass vmlinux from command line.




> diff --git a/scripts/kas_alias/item_list.c b/scripts/kas_alias/item_list.c
> new file mode 100644
> index 000000000000..48f2e525592a
> --- /dev/null
> +++ b/scripts/kas_alias/item_list.c
> @@ -0,0 +1,230 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <stdint.h>
> +#include <string.h>
> +#include <stdbool.h>
> +#include <assert.h>
> +#include "item_list.h"
> +
> +#define CHECK_ORDER_BY_ADDRESS(sort_by, current, temp, op) \
> +       ((sort_by) == BY_ADDRESS && (current)->addr op (temp)->addr)
> +#define CHECK_ORDER_BY_NAME(sort_by, current, temp, op) \
> +       ((sort_by) == BY_NAME && strcmp((current)->symb_name, (temp)->symb_name) op 0)
> +
> +struct item *list_index[96] = {0};
> +
> +void build_index(struct item *list)
> +{
> +       char current_first_letter = ' ';
> +       struct item *current = list;
> +
> +       while (current) {
> +               if (current->symb_name[0] != current_first_letter) {
> +                       current_first_letter = current->symb_name[0];
> +                       list_index[current_first_letter - 32] = current;
> +               }
> +               current = current->next;
> +       }
> +}
> +
> +struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr)
> +{
> +       struct item *new_item;
> +       struct item *current;
> +
> +       new_item = malloc(sizeof(struct item));
> +       if (!new_item)
> +               return NULL;
> +
> +       strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> +       new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> +       new_item->addr = addr;
> +       new_item->stype = stype;
> +       new_item->next = NULL;
> +
> +       if (!(*list)) {
> +               *list = new_item;
> +       } else {
> +               current = *list;
> +               while (current->next)
> +                       current = current->next;


What is the purpose of the ->next traverse in while() loop?

If you remember the last item,
you know where the new item should be connected, don't you?





> +struct item *merge(struct item *left, struct item *right, int sort_by)
> +{
> +       struct item *current = NULL;
> +       struct item *result = NULL;
> +
> +       if (!left)
> +               return right;
> +       if (!right)
> +               return left;
> +
> +       if (sort_by == BY_NAME) {
> +               if (strcmp(left->symb_name, right->symb_name) <= 0) {
> +                       result = left;
> +                       left = left->next;
> +               } else {
> +                       result = right;
> +                       right = right->next;
> +               }
> +       } else {
> +               if (sort_by == BY_ADDRESS) {
> +                       if (left->addr <= right->addr) {
> +                               result = left;
> +                               left = left->next;
> +                       } else {
> +                               result = right;
> +                               right = right->next;
> +                       }
> +               }
> +       }
> +
> +       current = result;
> +
> +       while (left && right) {
> +               if (sort_by == BY_NAME) {
> +                       if (strcmp(left->symb_name, right->symb_name) <= 0) {
> +                               current->next = left;
> +                               left = left->next;
> +                       } else {
> +                               current->next = right;
> +                               right = right->next;
> +                       }
> +               } else {
> +                       if (sort_by == BY_ADDRESS) {
> +                               if (left->addr <= right->addr) {
> +                                       current->next = left;
> +                                       left = left->next;
> +                               } else {
> +                                       current->next = right;
> +                                       right = right->next;
> +                               }
> +                       }
> +               }
> +
> +               current = current->next;
> +       }
> +
> +       if (left) {
> +               current->next = left;
> +       } else {
> +               if (right)
> +                       current->next = right;
> +       }
> +
> +       return result;
> +}
> +
> +struct item *merge_sort(struct item *head, int sort_by)



Any reason why you did not use qsort() in the C library?


One disadvantage of quick sort is that it is not "stable sort".

But, your algorithm (sort by name and sort by address)
does not keep the order anyway.




> diff --git a/scripts/kas_alias/item_list.h b/scripts/kas_alias/item_list.h
> new file mode 100644
> index 000000000000..b4891cb088ee
> --- /dev/null
> +++ b/scripts/kas_alias/item_list.h
> @@ -0,0 +1,26 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef ITEM_LIST_H
> +#define ITEM_LIST_H
> +#include <stdint.h>
> +
> +#define MAX_NAME_SIZE 256
> +#define BY_ADDRESS 1
> +#define BY_NAME 2
> +
> +struct item {
> +       char            symb_name[MAX_NAME_SIZE];
> +       uint64_t        addr;
> +       char            stype;
> +       struct item     *next;
> +};
> +
> +void build_index(struct item *list);
> +struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr);
> +void sort_list(struct item **list, int sort_by);
> +struct item *merge(struct item *left, struct item *right, int sort_by);
> +struct item *merge_sort(struct item *head, int sort_by);
> +void sort_list_m(struct item **head, int sort_by);
> +int insert_after(struct item *list, const uint64_t search_addr,
> +                const char *name, uint64_t addr, char stype);
> +void free_items(struct item **head);
> +#endif
> diff --git a/scripts/kas_alias/kas_alias.c b/scripts/kas_alias/kas_alias.c
> new file mode 100644
> index 000000000000..532aeb39f851
> --- /dev/null
> +++ b/scripts/kas_alias/kas_alias.c
> @@ -0,0 +1,217 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <stdint.h>
> +#include <unistd.h>
> +#include <string.h>
> +#include <stdbool.h>
> +#include <stdarg.h>
> +#include <regex.h>
> +
> +#include "item_list.h"
> +#include "duplicates_list.h"
> +#include "a2l.h"
> +
> +#define SYMB_IS_TEXT(s) ((((s)->stype) == 't') ||  (((s)->stype) == 'T'))
> +#define SYMB_IS_DATA(s) ((((s)->stype) == 'b') ||  (((s)->stype) == 'B') || \
> +                        (((s)->stype) == 'd') ||  (((s)->stype) == 'D') || \
> +                        (((s)->stype) == 'r') ||  (((s)->stype) == 'R'))
> +#ifdef CONFIG_KALLSYMS_ALIAS_DATA



Please do not use #ifdef CONFIG_ in host programs.

Also, please note include/linux/kconfig.h is not included
for host programs, so this #ifdef is always false.

You never tested this CONFIG_KALLSYMS_ALIAS_DATA







> +#define SYMB_NEEDS_ALIAS(s) (SYMB_IS_TEXT(s) || SYMB_IS_DATA(s))
> +#else
> +#define SYMB_NEEDS_ALIAS(s) SYMB_IS_TEXT(s)
> +#endif
> +#define FNOMATCH 0
> +#define FMATCH 1
> +#define EREGEX 2
> +
> +const char *ignore_regex[] = {
> +       "^__cfi_.*$",                           // __cfi_ preamble
> +#ifndef CONFIG_KALLSYMS_ALIAS_DATA_ALL
> +       "^_*TRACE_SYSTEM.*$",
> +       "^__already_done\\.[0-9]+$",            // Call a function once data
> +       "^___tp_str\\.[0-9]+$",
> +       "^___done\\.[0-9]+$",
> +       "^__print_once\\.[0-9]+$",
> +       "^_rs\\.[0-9]+$",
> +       "^__compound_literal\\.[0-9]+$",
> +       "^___once_key\\.[0-9]+$",
> +       "^__func__\\.[0-9]+$",
> +       "^__msg\\.[0-9]+$",
> +       "^CSWTCH\\.[0-9]+$",
> +       "^__flags\\.[0-9]+$",
> +       "^__wkey.*$",
> +       "^__mkey.*$",
> +       "^__key.*$",
> +#endif
> +       "^__pfx_.*$"                            // NOP-padding
> +};
> +
> +int suffix_serial;
> +
> +static inline void verbose_msg(bool verbose, const char *fmt, ...)

Meaningless 'inline'.  Only 'static' is enough.


> +{
> +       va_list args;
> +
> +       va_start(args, fmt);
> +       if (verbose)
> +               printf(fmt, args);



You cannot pass va_list to printf().

The correct code is:

          vprintf(fmt, args);








> +
> +       va_end(args);
> +}


verbose_msg() prints the message to stdout.

If verbose_msge is enabled, the output file breaks
because you redirect both real data and debug messages
in this way:
   scripts/kas_alias/kas_alias <input>   > <output>


If you implement debug logging, I recommend this:

   scripts/kas_alias/kas_alias <input> <output>





> +
> +static void create_suffix(const char *name, char *output_suffix)
> +{
> +       sprintf(output_suffix, "%s__alias__%d", name, suffix_serial++);
> +}
> +
> +static void create_file_suffix(const char *name, uint64_t address, char *output_suffix, char *cwd)
> +{
> +       const char *f_path;
> +       char *buf;
> +       int i = 0;
> +
> +       buf = addr2line_get_lines(address);
> +       f_path = remove_subdir(cwd, buf);
> +       if (f_path) {
> +               sprintf(output_suffix, "%s@%s", name, f_path);
> +               while (*(output_suffix + i) != '\0') {
> +                       switch (*(output_suffix + i)) {
> +                       case '/':
> +                       case ':':
> +                       case '.':
> +                               *(output_suffix + i) = '_';
> +                               break;
> +                       default:
> +                       }
> +               i++;
> +               }
> +       } else {
> +               create_suffix(name, output_suffix);
> +       }
> +}
> +
> +static int filter_symbols(char *symbol, const char **ignore_list, int regex_no)
> +{
> +       regex_t regex;
> +       int res, i;
> +
> +       for (i = 0; i < regex_no; i++) {
> +               res = regcomp(&regex, ignore_list[i], REG_EXTENDED);
> +               if (res)
> +                       return -EREGEX;
> +
> +               res = regexec(&regex, symbol, 0, NULL, 0);
> +               regfree(&regex);
> +               switch (res) {
> +               case 0:
> +                       return FMATCH;
> +               case REG_NOMATCH:
> +                       break;
> +               default:
> +                       return -EREGEX;
> +               }
> +       }
> +
> +       return FNOMATCH;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +       char t, sym_name[MAX_NAME_SIZE], new_name[MAX_NAME_SIZE + 15];
> +       struct duplicate_item  *duplicate_iterator;
> +       struct duplicate_item *duplicate;
> +       struct item *head = {NULL};



This might be something new I should learn.

When I initialize a pointer, I always write like this:
        struct item *head = NULL;


I have never seen this style before:
        struct item *head = {NULL};

But, the compiler does not warn about it.
Could you educate me how it works?





> +       bool need_2_process = true;
> +       struct item *last = {NULL};
> +       struct item  *current;
> +       int verbose_mode = 0;
> +       uint64_t address;
> +       FILE *fp;
> +       int res;
> +
> +       if (argc < 2 || argc > 3) {
> +               printf("Usage: %s <nmfile> [-verbose]\n", argv[0]);
> +               return 1;
> +       }
> +
> +       if (argc == 3 && strcmp(argv[2], "-verbose") == 0)


"-v" or "--verbose" is better
(although there is no way to enable it.)


Anyway, I only see super-boring messages
even with -verbose given.

Scanning nm data()
Sorting nm data
Scanning nm data for duplicates
Applying suffixes



> +               verbose_mode = 1;
> +
> +       verbose_msg(verbose_mode, "Scanning nm data(%s)\n", argv[1]);
> +
> +       fp = fopen(argv[1], "r");
> +       if (!fp) {
> +               printf("Can't open input file.\n");
> +               return 1;
> +       }
> +
> +       if (!addr2line_init(get_addr2line(A2L_DEFAULT), get_vmlinux(argv[1])))
> +               return 1;
> +
> +       while (fscanf(fp, "%lx %c %99s\n", &address, &t, sym_name) == 3) {
> +               if (strstr(sym_name, "@_")) {
> +                       if (verbose_mode && need_2_process)
> +                               printf("Already processed\n");
> +                       need_2_process = false;
> +                       }
> +               last = add_item(&last, sym_name, t, address);
> +               if (!last) {
> +                       printf("Error in allocate memory\n");
> +                       free_items(&head);
> +                       return 1;
> +               }
> +
> +               if (!head)
> +                       head = last;
> +       }
> +
> +       fclose(fp);
> +
> +       if (need_2_process) {
> +               verbose_msg(verbose_mode, "Sorting nm data\n");
> +               sort_list_m(&head, BY_NAME);
> +               verbose_msg(verbose_mode, "Scanning nm data for duplicates\n");
> +               duplicate = find_duplicates(head);
> +               if (!duplicate) {
> +                       printf("Error in duplicates list\n");
> +                       return 1;
> +               }
> +
> +               verbose_msg(verbose_mode, "Applying suffixes\n");
> +               build_index(head);
> +               duplicate_iterator = duplicate;
> +               while (duplicate_iterator) {
> +                       res = filter_symbols(duplicate_iterator->original_item->symb_name,
> +                                            ignore_regex, sizeof(ignore_regex) /
> +                                            sizeof(ignore_regex[0]));
> +                       if (res != FMATCH &&
> +                           SYMB_NEEDS_ALIAS(duplicate_iterator->original_item)) {
> +                               if (res < 0)
> +                                       return 1;
> +
> +                               create_file_suffix(duplicate_iterator->original_item->symb_name,
> +                                                  duplicate_iterator->original_item->addr,
> +                                                  new_name, vmlinux_path);
> +                               if (!insert_after(head, duplicate_iterator->original_item->addr,
> +                                                 new_name, duplicate_iterator->original_item->addr,
> +                                                 duplicate_iterator->original_item->stype))
> +                                       return 1;
> +                       }
> +
> +                       duplicate_iterator = duplicate_iterator->next;
> +               }
> +
> +               sort_list_m(&head, BY_ADDRESS);



Do you sort just for finding duplicates?


Since you sort the list by name, and then sort by address.

It can potentially change the order.


[input]
00000000 D foo
00000000 D bar
00000010 D baz

[merge sort by name]
00000000 D bar
00000010 D baz
00000000 D foo

[merge sort by address = final result]
00000000 D bar
00000000 D foo
00000010 D baz


It may not be a big deal, but such a destructive algorithm is frowned.



You do not need to sort the list to find duplicates.


Another choice is a hashtable of { name : count }.
Traversing the list, you can count the number of occurrences.
If count >= 2, it is duplicated.

The average look-up of a hashtable is O(1).
So, the hashtable (or set) algorithm is O(N).


Sorting is O(N log N).





> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index a432b171be82..cacf60b597ce 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -89,8 +89,9 @@ vmlinux_link()
>
>         ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
>
> -       # The kallsyms linking does not need debug symbols included.
> -       if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> +       # The kallsyms linking does not need debug symbols included, unless the KALLSYMS_ALIAS.
> +       if [ ! is_enabled CONFIG_KALLSYMS_ALIAS ] && \


I observed this error message:


scripts/link-vmlinux.sh: 93: [: is_enabled: unexpected operator


The correct code is this:


        if ! is_enabled CONFIG_KALLSYMS_ALIAS && \










> +           [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
>                 ldflags="${ldflags} ${wl}--strip-debug"
>         fi
>
> @@ -161,7 +162,11 @@ kallsyms()
>         fi
>
>         info KSYMS ${2}
> -       scripts/kallsyms ${kallsymopt} ${1} > ${2}
> +       if is_enabled CONFIG_KALLSYMS_ALIAS; then
> +               ALIAS=".alias"
> +               scripts/kas_alias/kas_alias ${1} >${1}${ALIAS}
> +               fi
> +       scripts/kallsyms ${kallsymopt} ${1}${ALIAS} > ${2}
>  }
>
>  # Perform one step in kallsyms generation, including temporary linking of
> --
> 2.34.1
>


--
Best Regards



Masahiro Yamada

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-08-28  8:04 [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms Alessandro Carminati (Red Hat)
                   ` (2 preceding siblings ...)
  2023-09-01  5:31 ` Masahiro Yamada
@ 2023-09-02  6:36 ` Masahiro Yamada
  2023-09-02  7:40   ` Alessandro Carminati
  2023-09-06 10:09   ` Alessandro Carminati
  2023-09-11 14:21 ` Alexander Lobakin
  4 siblings, 2 replies; 16+ messages in thread
From: Masahiro Yamada @ 2023-09-02  6:36 UTC (permalink / raw)
  To: Alessandro Carminati (Red Hat)
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Luis Chamberlain, Nathan Chancellor,
	Nick Desaulniers, Nicolas Schier, Alexander Lobakin, Nick Alcock,
	Kris Van Hees, Eugene Loh, Francis Laniel, Viktor Malik,
	linux-kbuild, linux-kernel, linux-trace-kernel, live-patching

On Mon, Aug 28, 2023 at 8:45 PM Alessandro Carminati (Red Hat)
<alessandro.carminati@gmail.com> wrote:
>
> From: Alessandro Carminati <alessandro.carminati@gmail.com>
>
> It is not uncommon for drivers or modules related to similar peripherals
> to have symbols with the exact same name.
> While this is not a problem for the kernel's binary itself, it becomes an
> issue when attempting to trace or probe specific functions using
> infrastructure like ftrace or kprobe.
>
> The tracing subsystem relies on the `nm -n vmlinux` output, which provides
> symbol information from the kernel's ELF binary. However, when multiple
> symbols share the same name, the standard nm output does not differentiate
> between them. This can lead to confusion and difficulty when trying to
> probe the intended symbol.
>
>  ~ # cat /proc/kallsyms | grep " name_show"
>  ffffffff8c4f76d0 t name_show
>  ffffffff8c9cccb0 t name_show
>  ffffffff8cb0ac20 t name_show
>  ffffffff8cc728c0 t name_show
>  ffffffff8ce0efd0 t name_show
>  ffffffff8ce126c0 t name_show
>  ffffffff8ce1dd20 t name_show
>  ffffffff8ce24e70 t name_show
>  ffffffff8d1104c0 t name_show
>  ffffffff8d1fe480 t name_show
>
> **kas_alias** addresses this challenge by extending the symbol names with
> unique suffixes during the kernel build process.
> The newly created aliases for these duplicated symbols are unique names
> that can be fed to the ftracefs interface. By doing so, it enables
> previously unreachable symbols to be probed.
>
>  ~ # cat /proc/kallsyms | grep " name_show"
>  ffffffff974f76d0 t name_show
>  ffffffff974f76d0 t name_show__alias__6340
>  ffffffff979cccb0 t name_show
>  ffffffff979cccb0 t name_show__alias__6341
>  ffffffff97b0ac20 t name_show
>  ffffffff97b0ac20 t name_show__alias__6342
>  ffffffff97c728c0 t name_show
>  ffffffff97c728c0 t name_show__alias__6343
>  ffffffff97e0efd0 t name_show
>  ffffffff97e0efd0 t name_show__alias__6344
>  ffffffff97e126c0 t name_show
>  ffffffff97e126c0 t name_show__alias__6345
>  ffffffff97e1dd20 t name_show
>  ffffffff97e1dd20 t name_show__alias__6346
>  ffffffff97e24e70 t name_show
>  ffffffff97e24e70 t name_show__alias__6347
>  ffffffff981104c0 t name_show
>  ffffffff981104c0 t name_show__alias__6348
>  ffffffff981fe480 t name_show
>  ffffffff981fe480 t name_show__alias__6349
>  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
>  > >/sys/kernel/tracing/kprobe_events
>  ~ # cat /sys/kernel/tracing/kprobe_events
>  p:kprobes/evnt1 name_show__alias__6349
>
> Changes from v1:
> - Integrated changes requested by Masami to exclude symbols with prefixes
>   "_cfi" and "_pfx".
> - Introduced a small framework to handle patterns that need to be excluded
>   from the alias production.
> - Excluded other symbols using the framework.
> - Introduced the ability to discriminate between text and data symbols.
> - Added two new config symbols in this version: CONFIG_KALLSYMS_ALIAS_DATA,
>   which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
>   excludes all filters and provides an alias for each duplicated symbol.
>
> https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gmail.com/
>
> Changes from v2:
> - Alias tags are created by querying DWARF information from the vmlinux.
> - The filename + line number is normalized and appended to the original name.
> - The tag begins with '@' to indicate the symbol source.
> - Not a change, but worth mentioning, since the alias is added to the existing
>   list, the old duplicated name is preserved, and the livepatch way of dealing
>   with duplicates is maintained.
> - Acknowledging the existence of scenarios where inlined functions declared in
>   header files may result in multiple copies due to compiler behavior, though
>    it is not actionable as it does not pose an operational issue.
> - Highlighting a single exception where the same name refers to different
>   functions: the case of "compat_binfmt_elf.c," which directly includes
>   "binfmt_elf.c" producing identical function copies in two separate
>   modules.
>
> sample from new v3
>
>  ~ # cat /proc/kallsyms | grep gic_mask_irq
>  ffffd0b03c04dae4 t gic_mask_irq
>  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
>  ffffd0b03c050960 t gic_mask_irq
>  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
>  ~ #
>
> https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gmail.com/
>
> Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> ---
>  init/Kconfig                        |  36 ++++
>  scripts/Makefile                    |   4 +
>  scripts/kas_alias/Makefile          |   4 +
>  scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
>  scripts/kas_alias/a2l.h             |  32 ++++
>  scripts/kas_alias/duplicates_list.c |  70 ++++++++
>  scripts/kas_alias/duplicates_list.h |  15 ++
>  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
>  scripts/kas_alias/item_list.h       |  26 +++
>  scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
>  scripts/link-vmlinux.sh             |  11 +-
>  11 files changed, 910 insertions(+), 3 deletions(-)


I added some review comments in another thread, but
one of the biggest concerns might be "910 insertions".


What this program does is quite simple,
"find duplicated names, and call addr2line".



You wrote a lot of code to self-implement these:

 - sort function
 - parse PATH env variable to find addr2line
 - fork addr2line to establish pipe communications



Have you considered writing the code in Python (or Perl)?
Is it too slow?

Most of the functions you implemented are already
available in script languages.



I am not sure if "@<file-path>" is a good solution,
but the amount of the added code looks too much to me.




--
Best Regards
Masahiro Yamada

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-08-29 14:51 ` Francis Laniel
@ 2023-09-02  7:26   ` Alessandro Carminati
  0 siblings, 0 replies; 16+ messages in thread
From: Alessandro Carminati @ 2023-09-02  7:26 UTC (permalink / raw)
  To: Francis Laniel
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Masahiro Yamada, Luis Chamberlain,
	Nathan Chancellor, Nick Desaulniers, Nicolas Schier,
	Alexander Lobakin, Nick Alcock, Kris Van Hees, Eugene Loh,
	Viktor Malik, linux-kbuild, linux-kernel, linux-trace-kernel,
	live-patching

Hi Francis,

I want to express my gratitude for your review and the time you took
to provide it.

Il giorno mar 29 ago 2023 alle ore 16:51 Francis Laniel
<flaniel@linux.microsoft.com> ha scritto:
>
> Hi.
>
> Le lundi 28 août 2023, 10:04:23 CEST Alessandro Carminati (Red Hat) a écrit :
> > From: Alessandro Carminati <alessandro.carminati@gmail.com>
> >
> > It is not uncommon for drivers or modules related to similar peripherals
> > to have symbols with the exact same name.
> > While this is not a problem for the kernel's binary itself, it becomes an
> > issue when attempting to trace or probe specific functions using
> > infrastructure like ftrace or kprobe.
>
> Thank you for the patch!
> I tested it and it works fine:
> root@vm-amd64:~# grep -m 6 ' name_show' /proc/kallsyms
> ffffffff81108330 t name_show
> ffffffff81108330 t name_show@_kernel_irq_irqdesc_c_264
> ffffffff816d2dd0 t name_show
> ffffffff816d2dd0 t name_show@_drivers_pnp_card_c_186
> ffffffff81814990 t name_show
> ffffffff81814990 t name_show@_drivers_gpu_drm_i915_gt_sysfs_engines_c_26
>
> On the paper, it combines well with my other patch forbidding tracing non
> unique symbols.
> I will nonetheless need to try yours on top of mine and I will let you know
> the result, even though everything should go well.
>
> Regarding the code itself, from my review your implementation is good.
> I was just wondering if we cannot avoid the first sort BY_NAME by modifying
> find_duplicates() and the returned structured, but the index you are using
> later should reduce the loopthrough time and compensate the first sort.
> I have some specific comments but they are mainly nits:
>
> > The tracing subsystem relies on the `nm -n vmlinux` output, which provides
> > symbol information from the kernel's ELF binary. However, when multiple
> > symbols share the same name, the standard nm output does not differentiate
> > between them. This can lead to confusion and difficulty when trying to
> > probe the intended symbol.
> >
> >  ~ # cat /proc/kallsyms | grep " name_show"
> >  ffffffff8c4f76d0 t name_show
> >  ffffffff8c9cccb0 t name_show
> >  ffffffff8cb0ac20 t name_show
> >  ffffffff8cc728c0 t name_show
> >  ffffffff8ce0efd0 t name_show
> >  ffffffff8ce126c0 t name_show
> >  ffffffff8ce1dd20 t name_show
> >  ffffffff8ce24e70 t name_show
> >  ffffffff8d1104c0 t name_show
> >  ffffffff8d1fe480 t name_show
> >
> > **kas_alias** addresses this challenge by extending the symbol names with
> > unique suffixes during the kernel build process.
> > The newly created aliases for these duplicated symbols are unique names
> > that can be fed to the ftracefs interface. By doing so, it enables
> > previously unreachable symbols to be probed.
> >
> >  ~ # cat /proc/kallsyms | grep " name_show"
> >  ffffffff974f76d0 t name_show
> >  ffffffff974f76d0 t name_show__alias__6340
>
> This output is outdated.
> This is not a big problem but it would be better with the updated one as the
> "@_file_line" is better.
>
> >  ffffffff979cccb0 t name_show
> >  ffffffff979cccb0 t name_show__alias__6341
> >  ffffffff97b0ac20 t name_show
> >  ffffffff97b0ac20 t name_show__alias__6342
> >  ffffffff97c728c0 t name_show
> >  ffffffff97c728c0 t name_show__alias__6343
> >  ffffffff97e0efd0 t name_show
> >  ffffffff97e0efd0 t name_show__alias__6344
> >  ffffffff97e126c0 t name_show
> >  ffffffff97e126c0 t name_show__alias__6345
> >  ffffffff97e1dd20 t name_show
> >  ffffffff97e1dd20 t name_show__alias__6346
> >  ffffffff97e24e70 t name_show
> >  ffffffff97e24e70 t name_show__alias__6347
> >  ffffffff981104c0 t name_show
> >  ffffffff981104c0 t name_show__alias__6348
> >  ffffffff981fe480 t name_show
> >  ffffffff981fe480 t name_show__alias__6349
> >  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
> >
> >  > >/sys/kernel/tracing/kprobe_events
> >
> >  ~ # cat /sys/kernel/tracing/kprobe_events
> >  p:kprobes/evnt1 name_show__alias__6349
> >
> > Changes from v1:
> > - Integrated changes requested by Masami to exclude symbols with prefixes
> >   "_cfi" and "_pfx".
> > - Introduced a small framework to handle patterns that need to be excluded
> >   from the alias production.
> > - Excluded other symbols using the framework.
> > - Introduced the ability to discriminate between text and data symbols.
> > - Added two new config symbols in this version: CONFIG_KALLSYMS_ALIAS_DATA,
> >   which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
> >   excludes all filters and provides an alias for each duplicated symbol.
> >
> > https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gm
> > ail.com/
> >
> > Changes from v2:
> > - Alias tags are created by querying DWARF information from the vmlinux.
> > - The filename + line number is normalized and appended to the original
> > name. - The tag begins with '@' to indicate the symbol source.
> > - Not a change, but worth mentioning, since the alias is added to the
> > existing list, the old duplicated name is preserved, and the livepatch way
> > of dealing with duplicates is maintained.
> > - Acknowledging the existence of scenarios where inlined functions declared
> > in header files may result in multiple copies due to compiler behavior,
> > though it is not actionable as it does not pose an operational issue.
> > - Highlighting a single exception where the same name refers to different
> >   functions: the case of "compat_binfmt_elf.c," which directly includes
> >   "binfmt_elf.c" producing identical function copies in two separate
> >   modules.
> >
> > sample from new v3
> >
> >  ~ # cat /proc/kallsyms | grep gic_mask_irq
> >  ffffd0b03c04dae4 t gic_mask_irq
> >  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
> >  ffffd0b03c050960 t gic_mask_irq
> >  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
> >  ~ #
> >
> > https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gm
> > ail.com/
> >
> > Signed-off-by: Alessandro Carminati (Red Hat)
> > <alessandro.carminati@gmail.com> ---
> >  init/Kconfig                        |  36 ++++
> >  scripts/Makefile                    |   4 +
> >  scripts/kas_alias/Makefile          |   4 +
> >  scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
> >  scripts/kas_alias/a2l.h             |  32 ++++
> >  scripts/kas_alias/duplicates_list.c |  70 ++++++++
> >  scripts/kas_alias/duplicates_list.h |  15 ++
> >  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
> >  scripts/kas_alias/item_list.h       |  26 +++
> >  scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
> >  scripts/link-vmlinux.sh             |  11 +-
> >  11 files changed, 910 insertions(+), 3 deletions(-)
> >  create mode 100644 scripts/kas_alias/Makefile
> >  create mode 100644 scripts/kas_alias/a2l.c
> >  create mode 100644 scripts/kas_alias/a2l.h
> >  create mode 100644 scripts/kas_alias/duplicates_list.c
> >  create mode 100644 scripts/kas_alias/duplicates_list.h
> >  create mode 100644 scripts/kas_alias/item_list.c
> >  create mode 100644 scripts/kas_alias/item_list.h
> >  create mode 100644 scripts/kas_alias/kas_alias.c
> >
> > diff --git a/init/Kconfig b/init/Kconfig
> > index f7f65af4ee12..bc69fcd9cbc8 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -1737,6 +1737,42 @@ config KALLSYMS_BASE_RELATIVE
> >         time constants, and no relocation pass is required at runtime to fix
> >         up the entries based on the runtime load address of the kernel.
> >
> > +config KALLSYMS_ALIAS
> > +     bool "Produces alias for duplicated symbols" if EXPERT
> > +     depends on KALLSYMS && (DEBUG_INFO_DWARF4 || DEBUG_INFO_DWARF5)
> > +     help
> > +       It is not uncommon for drivers or modules related to similar
> > +       peripherals to have symbols with the exact same name.
> > +       While this is not a problem for the kernel's binary itself, it
> > +       becomes an issue when attempting to trace or probe specific
> > +       functions using infrastructure like ftrace or kprobe.
> > +
> > +       This option addresses this challenge by extending the symbol names
> > +       with unique suffixes during the kernel build process.
> > +       The newly created aliases for these duplicated symbols are unique
> > +       names that can be fed to the ftrace sysfs interface. By doing so, it
> > +       enables previously unreachable symbols to be probed.
> > +
> > +config CONFIG_KALLSYMS_ALIAS_DATA
> > +     bool "Produces alias also for data"
> > +     depends on KALLSYMS_ALIAS
> > +     help
> > +       Sometimes it can be useful to refer to data. In live patch
> scenarios,
> > +       you may find yourself needing to use symbols that are shared with
> > +       other functions. Since symbols face the same issue as functions,
> this
> > +       option allows you to create aliases for data as well.
> > +
> > +config CONFIG_KALLSYMS_ALIAS_DATA_ALL
> > +     bool "Removes all filter when producing data alias"
> > +     depends on CONFIG_KALLSYMS_ALIAS_DATA
> > +     help
> > +       When selecting data aliases, not all symbols are included in the set
> > +       This is because many symbols are unlikely to be used. If you choose
> > +       to have an alias for all data symbols, be aware that it will
> > +       significantly increase the size.
> > +
> > +       If unsure, say N.
> > +
> >  # end of the "standard kernel features (expert users)" menu
> >
> >  # syscall, maps, verifier
> > diff --git a/scripts/Makefile b/scripts/Makefile
> > index 32b6ba722728..65fafe17cfe5 100644
> > --- a/scripts/Makefile
> > +++ b/scripts/Makefile
> > @@ -49,3 +49,7 @@ subdir-$(CONFIG_SECURITY_SELINUX) += selinux
> >
> >  # Let clean descend into subdirs
> >  subdir-      += basic dtc gdb kconfig mod
> > +
> > +# KALLSyms alias
> > +subdir-$(CONFIG_KALLSYMS_ALIAS) += kas_alias
> > +
> > diff --git a/scripts/kas_alias/Makefile b/scripts/kas_alias/Makefile
> > new file mode 100644
> > index 000000000000..e1fde69232b4
> > --- /dev/null
> > +++ b/scripts/kas_alias/Makefile
> > @@ -0,0 +1,4 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +hostprogs-always-$(CONFIG_KALLSYMS_ALIAS)    += kas_alias
> > +
> > +kas_alias-objs        := duplicates_list.o item_list.o kas_alias.o a2l.o
> > diff --git a/scripts/kas_alias/a2l.c b/scripts/kas_alias/a2l.c
> > new file mode 100644
> > index 000000000000..a9692ac30180
> > --- /dev/null
> > +++ b/scripts/kas_alias/a2l.c
> > @@ -0,0 +1,268 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +#include <sys/types.h>
> > +#include <sys/wait.h>
> > +#include <string.h>
> > +#include <stdint.h>
> > +#include <stdbool.h>
> > +
> > +#include "a2l.h"
> > +
> > +int addr2line_pid = -1;
> > +int a2l_in[2];
> > +int a2l_out[2];
> > +char line[MAX_BUF];
> > +char vmlinux_path[MAX_BUF];
> > +char addr2line_cmd[MAX_CMD_LEN];
> > +FILE *a2l_stdin, *a2l_stdout;
> > +
> > +static char *normalize_path(const char *input_path, char *output_path)
> > +{
> > +     char *prev_token = NULL;
> > +     char *delimiter = "/";
> > +     char inbuf[MAX_BUF];
>
> Rather than using memset below you can initialize it like this above:
> char inbuf[MAX_BUF] = {0};
>
> > +     char *token;
> > +     char *pos;
> > +
> > +     memset(inbuf, 0, MAX_BUF);
> > +     *output_path = '\0';
> > +     strncpy(inbuf, input_path, MAX_BUF);
> > +     if (!input_path || !output_path || strlen(input_path) == 0)
> > +             return NULL;
> > +
> > +     token = strtok(inbuf, delimiter);
> > +     while (token) {
> > +             if (strcmp(token, "..") == 0 && prev_token) {
> > +                     pos = strrchr(output_path, '/');
>
> > +                     if (pos)
> > +                             *pos = '\0';
> > +
> > +             } else if (strcmp(token, ".") != 0) {
> > +                     strcat(output_path, "/");
> > +                     strcat(output_path, token);
> > +             }
> > +
> > +             prev_token = token;
> > +             token = strtok(NULL, delimiter);
> > +     }
> > +
> > +     return output_path;
> > +}
> > +
> > +static void path_of(const char *full_path, char *path)
> > +{
> > +     const char *last_slash = strrchr(full_path, '/');
> > +     size_t path_length;
> > +     char cwd[MAX_BUF];
> > +
> > +     if (!last_slash) {
> > +             if (getcwd(cwd, sizeof(cwd)))
> > +                     strcpy(path, cwd);
> > +             else
> > +                     strcpy(path, ".");
> > +     } else {
> > +             path_length = last_slash - full_path;
> > +             strncpy(path, full_path, path_length);
> > +             path[path_length] = '\0';
> > +     }
> > +}
> > +
> > +static bool file_exists(const char *file_path)
> > +{
> > +     FILE *file;
> > +
> > +     file = fopen(file_path, "r");
> > +     if (file) {
> > +             fclose(file);
> > +             return true;
> > +     }
> > +     return false;
> > +}
> > +
> > +int addr2line_init(const char *cmd, const char *vmlinux)
> > +{
> > +     if ((!file_exists(cmd)) || (!file_exists(vmlinux))) {
> > +             printf("file not found\n");
> > +             return 0;
> > +             }
> > +
> > +     path_of(vmlinux, vmlinux_path);
> > +     if (pipe(a2l_in) == -1) {
> > +             printf("Failed to create pipe\n");
> > +             return 0;
> > +     }
> > +
> > +     if (pipe(a2l_out) == -1) {
> > +             printf("Failed to create pipe\n");
> > +             return 0;
> > +     }
> > +
> > +     addr2line_pid = fork();
> > +     if (addr2line_pid == -1) {
> > +             printf("Failed to fork process\n");
> > +             close(a2l_in[P_READ]);
> > +             close(a2l_in[P_WRITE]);
> > +             close(a2l_out[P_READ]);
> > +             close(a2l_out[P_WRITE]);
> > +             return 0;
> > +     }
> > +
> > +     if (addr2line_pid == 0) {
> > +             dup2(a2l_in[P_READ], 0);
> > +             dup2(a2l_out[P_WRITE], 1);
> > +             close(a2l_in[P_WRITE]);
> > +             close(a2l_out[P_READ]);
> > +
> > +             execlp(cmd, cmd, ADDR2LINE_ARGS, vmlinux, NULL);
> > +
> > +             printf("Failed to execute addr2line command\n");
> > +             exit(1);
> > +     } else {
> > +             close(a2l_in[P_READ]);
> > +             close(a2l_out[P_WRITE]);
> > +     }
> > +
> > +     a2l_stdin = fdopen(a2l_in[P_WRITE], "w");
> > +     if (!a2l_stdin) {
> > +             printf("Failed to open pipe a2l_in\n");
> > +             return 0;
> > +     }
> > +
> > +     a2l_stdout = fdopen(a2l_out[P_READ], "r");
> > +     if (!a2l_stdout) {
> > +             printf("Failed to open pipe a2l_out\n");
> > +             fclose(a2l_stdin);
> > +             return 0;
> > +     }
> > +
> > +     return 1;
> > +}
> > +
> > +const char *remove_subdir(const char *home, const char *f_path)
> > +{
> > +     int i = 0;
> > +
> > +     while (*(home + i) == *(f_path + i))
>
> Using home[i] and f_path[i] should do the trick too.
>
> > +             i++;
> > +
> > +     return (strlen(home) != i) ? NULL : f_path + i;
> > +}
> > +
> > +char *addr2line_get_lines(uint64_t address)
> > +{
> > +     char buf[MAX_BUF];
> > +
> > +     fprintf(a2l_stdin, "%08lx\n", address);
> > +     fflush(a2l_stdin);
> > +
> > +     if (!fgets(line, sizeof(line), a2l_stdout)) {
> > +             printf("Failed to read lines from addr2line\n");
> > +             return NULL;
> > +     }
> > +
> > +     if (!fgets(line, sizeof(line), a2l_stdout)) {
> > +             printf("Failed to read lines from addr2line\n");
> > +             return NULL;
> > +     }
> > +     line[strcspn(line, "\n")] = '\0';
> > +     strncpy(buf, line, MAX_BUF);
> > +     return normalize_path(buf, line);
> > +}
> > +
> > +int addr2line_cleanup(void)
> > +{
> > +     int status;
> > +
> > +     if (addr2line_pid != -1) {
> > +             kill(addr2line_pid, SIGKILL);
> > +             waitpid(addr2line_pid, &status, 0);
> > +             fclose(a2l_stdin);
> > +             fclose(a2l_stdout);
> > +             addr2line_pid = -1;
> > +     }
> > +
> > +     return 1;
> > +}
> > +
> > +static char *find_executable(const char *command)
>
> Nice function, I would rather have tried to execve() the command.
>
> > +{
> > +     char *path_env = getenv("PATH");
> > +     char *executable_path;
> > +     char *path_copy;
> > +     char *path;
> > +     int n;
> > +
> > +     if (!path_env)
> > +             return NULL;
> > +
> > +     path_copy = strdup(path_env);
> > +     if (!path_copy)
> > +             return NULL;
> > +
> > +     path = strtok(path_copy, ":");
> > +     while (path) {
> > +             n = snprintf(0, 0, "%s/%s", path, command);
> > +             executable_path = (char *)malloc(n + 1);
> > +             snprintf(executable_path, n + 1, "%s/%s", path, command);
> > +             if (access(executable_path, X_OK) == 0) {
> > +                     free(path_copy);
> > +                     return executable_path;
> > +             }
> > +
> > +     path = strtok(NULL, ":");
> > +     free(executable_path);
> > +     executable_path = NULL;
>
> > +     }
> > +
> > +     free(path_copy);
> > +     if (executable_path)
> > +             free(executable_path);
>
> If you arrive here, executable_path should be NULL, right?
>
> > +     return NULL;
> > +}
> > +
> > +const char *get_addr2line(int mode)
> > +{
> > +     char *buf = "";
> > +
> > +     switch (mode) {
> > +     case A2L_CROSS:
> > +             buf = getenv("CROSS_COMPILE");
> > +             memcpy(addr2line_cmd, buf, strlen(buf));
> > +     case A2L_DEFAULT:
> > +             memcpy(addr2line_cmd + strlen(buf), ADDR2LINE,
> strlen(ADDR2LINE));
> > +             buf = find_executable(addr2line_cmd);
> > +             if (buf) {
> > +                     memcpy(addr2line_cmd, buf, strlen(buf));
> > +                     free(buf);
> > +             }
> > +             return addr2line_cmd;
> > +     case A2L_LLVM:
> > +     default:
> > +             return NULL;
> > +     }
> > +}
> > +
> > +char *get_vmlinux(char *input)
> > +{
> > +     const char *match_string1 = ".syms";
> > +     const char *match_string2 = ".tmp_vmlinux.kallsyms";
> > +     char *result = NULL;
> > +     char *match_pos;
> > +
> > +     match_pos = strstr(input, match_string1);
> > +     if (!match_pos)
> > +             return NULL;
> > +
> > +     match_pos = strstr(input, match_string2);
> > +     if (!match_pos)
> > +             return NULL;
> > +
> > +     result = strdup(input);
> > +     match_pos = strstr(result, match_string1);
> > +     *match_pos = '\0';
> > +     return result;
> > +}
> > diff --git a/scripts/kas_alias/a2l.h b/scripts/kas_alias/a2l.h
> > new file mode 100644
> > index 000000000000..ca6419229dde
> > --- /dev/null
> > +++ b/scripts/kas_alias/a2l.h
> > @@ -0,0 +1,32 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +#ifndef A2L_H
> > +#define A2L_H
> > +#include <stdint.h>
> > +
> > +#define ADDR2LINE "addr2line"
> > +#define ADDR2LINE_ARGS "-fe"
> > +//#define VMLINUX "vmlinux"
> > +#define MAX_BUF 4096
> > +#define MAX_CMD_LEN 256
> > +#define P_READ 0
> > +#define P_WRITE 1
> > +#define A2L_DEFAULT 1
> > +#define A2L_CROSS 2
> > +#define A2L_LLVM 3
> > +#define A2L_MAKE_VALUE 2
> > +
> > +extern int addr2line_pid;
> > +extern int a2l_in[2];
> > +extern int a2l_out[2];
> > +extern char line[MAX_BUF];
> > +extern char vmlinux_path[MAX_BUF];
> > +extern char addr2line_cmd[MAX_CMD_LEN];
> > +
> > +int addr2line_init(const char *cmd, const char *vmlinux);
> > +char *addr2line_get_lines(uint64_t address);
> > +int addr2line_cleanup(void);
> > +const char *remove_subdir(const char *home, const char *f_path);
> > +const char *get_addr2line(int mode);
> > +char *get_vmlinux(char *input);
> > +
> > +#endif
> > diff --git a/scripts/kas_alias/duplicates_list.c
> > b/scripts/kas_alias/duplicates_list.c new file mode 100644
> > index 000000000000..e7a3d2917937
> > --- /dev/null
> > +++ b/scripts/kas_alias/duplicates_list.c
> > @@ -0,0 +1,70 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdint.h>
> > +#include <stdio.h>
> > +#include <string.h>
> > +#include <stdlib.h>
> > +#include <stdbool.h>
> > +
> > +#include "item_list.h"
> > +#include "duplicates_list.h"
> > +
> > +struct duplicate_item *find_duplicates(struct item *list)
> > +{
> > +     struct duplicate_item *current_duplicate = NULL;
> > +     struct duplicate_item *duplicates = NULL;
> > +     struct duplicate_item *new_duplicate;
> > +     struct item *current_item = list;
> > +     bool prev_was_duplicate = false;
> > +     struct item *prev_item = NULL;
> > +
> > +     while (current_item) {
> > +             if ((prev_item && (strcmp(current_item->symb_name, prev_item-
> >symb_name)
> > == 0)) || +               prev_was_duplicate) {
> > +                     if (!duplicates) {
> > +                             duplicates = malloc(sizeof(struct
> duplicate_item));
> > +                             if (!duplicates)
> > +                                     return NULL;
> > +
> > +                             duplicates->original_item = prev_item;
> > +                             duplicates->next = NULL;
> > +                             current_duplicate = duplicates;
> > +                     } else {
> > +                             new_duplicate = malloc(sizeof(struct
> duplicate_item));
> > +                             if (!new_duplicate) {
> > +                                     free_duplicates(&duplicates);
> > +                                     return NULL;
> > +                             }
> > +
> > +                             new_duplicate->original_item = prev_item;
> > +                             new_duplicate->next = NULL;
> > +                             current_duplicate->next = new_duplicate;
> > +                             current_duplicate = new_duplicate;
> > +
> > +                             if ((strcmp(current_item->symb_name, prev_item-
> >symb_name) != 0) &&
> > +                                 (prev_was_duplicate))
> > +                                     prev_was_duplicate = false;
> > +                             else
> > +                                     prev_was_duplicate = true;
>
> You can remove the branch and set prev_was_duplicate to:
> prev_was_duplicate = strcmp(current_item->symb_name, prev_item->symb_name) !=
> 0 && prev_was_duplicate;
 I agree with all your points, except for one.
While your statement is undoubtedly more concise than mine, in the v4,
I actually use its negation.
>
> > +                     }
> > +             }
> > +
> > +             prev_item = current_item;
> > +             current_item = current_item->next;
> > +     }
> > +
> > +     return duplicates;
> > +}
> > +
> > +void free_duplicates(struct duplicate_item **duplicates)
> > +{
> > +     struct duplicate_item *duplicates_iterator = *duplicates;
> > +     struct duplicate_item *app;
> > +
> > +     while (duplicates_iterator) {
> > +             app = duplicates_iterator;
> > +             duplicates_iterator = duplicates_iterator->next;
> > +             free(app);
> > +     }
> > +
> > +     *duplicates = NULL;
> > +}
> > diff --git a/scripts/kas_alias/duplicates_list.h
> > b/scripts/kas_alias/duplicates_list.h new file mode 100644
> > index 000000000000..76aa73e584bc
> > --- /dev/null
> > +++ b/scripts/kas_alias/duplicates_list.h
> > @@ -0,0 +1,15 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +#ifndef DUPLICATES_LIST_H
> > +#define DUPLICATES_LIST_H
> > +
> > +#include "item_list.h"
> > +
> > +struct duplicate_item {
> > +     struct item *original_item;
> > +     struct duplicate_item *next;
> > +};
> > +
> > +struct duplicate_item *find_duplicates(struct item *list);
> > +void free_duplicates(struct duplicate_item **duplicates);
> > +
> > +#endif
> > diff --git a/scripts/kas_alias/item_list.c b/scripts/kas_alias/item_list.c
> > new file mode 100644
> > index 000000000000..48f2e525592a
> > --- /dev/null
> > +++ b/scripts/kas_alias/item_list.c
> > @@ -0,0 +1,230 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <stdint.h>
> > +#include <string.h>
> > +#include <stdbool.h>
> > +#include <assert.h>
> > +#include "item_list.h"
> > +
> > +#define CHECK_ORDER_BY_ADDRESS(sort_by, current, temp, op) \
> > +     ((sort_by) == BY_ADDRESS && (current)->addr op (temp)->addr)
> > +#define CHECK_ORDER_BY_NAME(sort_by, current, temp, op) \
> > +     ((sort_by) == BY_NAME && strcmp((current)->symb_name, (temp)-
> >symb_name)
> > op 0) +
> > +struct item *list_index[96] = {0};
> > +
> > +void build_index(struct item *list)
> > +{
> > +     char current_first_letter = ' ';
> > +     struct item *current = list;
> > +
> > +     while (current) {
> > +             if (current->symb_name[0] != current_first_letter) {
> > +                     current_first_letter = current->symb_name[0];
> > +                     list_index[current_first_letter - 32] = current;
>
> > +             }
> > +             current = current->next;
> > +     }
> > +}
> > +
> > +struct item *add_item(struct item **list, const char *name, char stype,
> > uint64_t addr) +{
> > +     struct item *new_item;
> > +     struct item *current;
> > +
> > +     new_item = malloc(sizeof(struct item));
> > +     if (!new_item)
> > +             return NULL;
> > +
> > +     strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> > +     new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> > +     new_item->addr = addr;
> > +     new_item->stype = stype;
> > +     new_item->next = NULL;
> > +
> > +     if (!(*list)) {
> > +             *list = new_item;
> > +     } else {
> > +             current = *list;
> > +             while (current->next)
> > +                     current = current->next;
> > +
> > +             current->next = new_item;
> > +     }
> > +     return new_item;
> > +}
> > +
> > +void sort_list(struct item **list, int sort_by)
> > +{
> > +     struct item *current = *list;
> > +     struct item *sorted = NULL;
> > +     struct item *next_item;
> > +     struct item *temp;
> > +
> > +     if (!(*list) || !((*list)->next))
> > +             return;
> > +
> > +     while (current) {
> > +             next_item = current->next;
> > +             if (!sorted ||
> > +                 (CHECK_ORDER_BY_ADDRESS(sort_by, current, sorted, <) ||
> > +                 CHECK_ORDER_BY_NAME(sort_by, current, sorted, >=))) {
> > +                     current->next = sorted;
> > +                     sorted = current;
> > +             } else {
> > +                     temp = sorted;
> > +                     while (temp->next &&
> > +                            (CHECK_ORDER_BY_ADDRESS(sort_by, current, temp-
> >next, >=) ||
> > +                            CHECK_ORDER_BY_NAME(sort_by, current, temp->next,
> >=)))
> > +                             temp = temp->next;
> > +
> > +                     current->next = temp->next;
> > +                     temp->next = current;
> > +             }
> > +             current = next_item;
> > +     }
> > +
> > +     *list = sorted;
> > +}
> > +
> > +struct item *merge(struct item *left, struct item *right, int sort_by)
>
> > +{
> > +     struct item *current = NULL;
> > +     struct item *result = NULL;
> > +
> > +     if (!left)
> > +             return right;
> > +     if (!right)
> > +             return left;
> > +
> > +     if (sort_by == BY_NAME) {
> > +             if (strcmp(left->symb_name, right->symb_name) <= 0) {
> > +                     result = left;
> > +                     left = left->next;
> > +             } else {
> > +                     result = right;
> > +                     right = right->next;
> > +             }
> > +     } else {
> > +             if (sort_by == BY_ADDRESS) {
> > +                     if (left->addr <= right->addr) {
> > +                             result = left;
> > +                             left = left->next;
> > +                     } else {
> > +                             result = right;
> > +                             right = right->next;
> > +                     }
> > +             }
> > +     }
> > +
> > +     current = result;
> > +
> > +     while (left && right) {
> > +             if (sort_by == BY_NAME) {
> > +                     if (strcmp(left->symb_name, right->symb_name) <= 0) {
> > +                             current->next = left;
> > +                             left = left->next;
> > +                     } else {
> > +                             current->next = right;
> > +                             right = right->next;
> > +                     }
> > +             } else {
> > +                     if (sort_by == BY_ADDRESS) {
> > +                             if (left->addr <= right->addr) {
> > +                                     current->next = left;
> > +                                     left = left->next;
> > +                             } else {
> > +                                     current->next = right;
> > +                                     right = right->next;
> > +                             }
> > +                     }
> > +             }
> > +
> > +             current = current->next;
> > +     }
> > +
> > +     if (left) {
> > +             current->next = left;
> > +     } else {
> > +             if (right)
>
> > +                     current->next = right;
> > +     }
> > +
> > +     return result;
> > +}
> > +
> > +struct item *merge_sort(struct item *head, int sort_by)
> > +{
> > +     struct item *right;
> > +     struct item *slow;
> > +     struct item *fast;
> > +     struct item *left;
> > +
> > +     if (!head || !head->next)
> > +             return head;
> > +
> > +     slow = head;
> > +     fast = head->next;
> > +
> > +     while (fast && fast->next) {
> > +             slow = slow->next;
> > +             fast = fast->next->next;
> > +     }
> > +
> > +     left = head;
> > +     right = slow->next;
> > +     slow->next = NULL;
> > +
> > +     left = merge_sort(left, sort_by);
> > +     right = merge_sort(right, sort_by);
> > +
> > +     return merge(left, right, sort_by);
> > +}
> > +
> > +void sort_list_m(struct item **head, int sort_by)
> > +{
> > +     if (!(*head) || !((*head)->next))
> > +             return;
> > +
> > +     *head = merge_sort(*head, sort_by);
> > +}
> > +
> > +int insert_after(struct item *list, const uint64_t search_addr,
> > +              const char *name, uint64_t addr, char stype)
> > +{
> > +     struct item *new_item;
> > +     struct item *current;
> > +     int ret = 0;
> > +
> > +     current = (list_index[name[0] - 32]) ? list_index[name[0] - 32] :
> list;
> > +     while (current) {
> > +             if (current->addr == search_addr) {
> > +                     new_item = malloc(sizeof(struct item));
> > +                     if (!new_item)
> > +                             return ret;
> > +                     strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> > +                     new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> > +                     new_item->addr = addr;
> > +                     new_item->stype = stype;
> > +                     new_item->next = current->next;
> > +                     current->next = new_item;
> > +                     ret = 1;
> > +                     break;
>
> > +             }
> > +             current = current->next;
> > +     }
> > +     return ret;
> > +}
> > +
> > +void free_items(struct item **head)
> > +{
> > +     struct item *app, *item_iterator = *head;
> > +
> > +     while (item_iterator) {
> > +             app = item_iterator;
> > +             item_iterator = item_iterator->next;
> > +             free(app);
> > +     }
> > +     *head = NULL;
> > +}
> > diff --git a/scripts/kas_alias/item_list.h b/scripts/kas_alias/item_list.h
> > new file mode 100644
> > index 000000000000..b4891cb088ee
> > --- /dev/null
> > +++ b/scripts/kas_alias/item_list.h
> > @@ -0,0 +1,26 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +#ifndef ITEM_LIST_H
> > +#define ITEM_LIST_H
> > +#include <stdint.h>
> > +
> > +#define MAX_NAME_SIZE 256
> > +#define BY_ADDRESS 1
> > +#define BY_NAME 2
> > +
> > +struct item {
> > +     char            symb_name[MAX_NAME_SIZE];
> > +     uint64_t        addr;
> > +     char            stype;
> > +     struct item     *next;
> > +};
> > +
> > +void build_index(struct item *list);
> > +struct item *add_item(struct item **list, const char *name, char stype,
> > uint64_t addr); +void sort_list(struct item **list, int sort_by);
> > +struct item *merge(struct item *left, struct item *right, int sort_by);
> > +struct item *merge_sort(struct item *head, int sort_by);
> > +void sort_list_m(struct item **head, int sort_by);
> > +int insert_after(struct item *list, const uint64_t search_addr,
> > +              const char *name, uint64_t addr, char stype);
> > +void free_items(struct item **head);
> > +#endif
> > diff --git a/scripts/kas_alias/kas_alias.c b/scripts/kas_alias/kas_alias.c
> > new file mode 100644
> > index 000000000000..532aeb39f851
> > --- /dev/null
> > +++ b/scripts/kas_alias/kas_alias.c
> > @@ -0,0 +1,217 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <stdint.h>
> > +#include <unistd.h>
> > +#include <string.h>
> > +#include <stdbool.h>
> > +#include <stdarg.h>
> > +#include <regex.h>
> > +
> > +#include "item_list.h"
> > +#include "duplicates_list.h"
> > +#include "a2l.h"
> > +
> > +#define SYMB_IS_TEXT(s) ((((s)->stype) == 't') ||  (((s)->stype) == 'T'))
> > +#define SYMB_IS_DATA(s) ((((s)->stype) == 'b') ||  (((s)->stype) == 'B') ||
> > \ +                    (((s)->stype) == 'd') ||  (((s)->stype) == 'D') || \
> > +                      (((s)->stype) == 'r') ||  (((s)->stype) == 'R'))
> > +#ifdef CONFIG_KALLSYMS_ALIAS_DATA
> > +#define SYMB_NEEDS_ALIAS(s) (SYMB_IS_TEXT(s) || SYMB_IS_DATA(s))
> > +#else
> > +#define SYMB_NEEDS_ALIAS(s) SYMB_IS_TEXT(s)
> > +#endif
> > +#define FNOMATCH 0
> > +#define FMATCH 1
> > +#define EREGEX 2
> > +
> > +const char *ignore_regex[] = {
> > +     "^__cfi_.*$",                           // __cfi_ preamble
> > +#ifndef CONFIG_KALLSYMS_ALIAS_DATA_ALL
> > +     "^_*TRACE_SYSTEM.*$",
> > +     "^__already_done\\.[0-9]+$",            // Call a function once data
> > +     "^___tp_str\\.[0-9]+$",
> > +     "^___done\\.[0-9]+$",
> > +     "^__print_once\\.[0-9]+$",
> > +     "^_rs\\.[0-9]+$",
> > +     "^__compound_literal\\.[0-9]+$",
> > +     "^___once_key\\.[0-9]+$",
> > +     "^__func__\\.[0-9]+$",
> > +     "^__msg\\.[0-9]+$",
> > +     "^CSWTCH\\.[0-9]+$",
> > +     "^__flags\\.[0-9]+$",
> > +     "^__wkey.*$",
> > +     "^__mkey.*$",
> > +     "^__key.*$",
> > +#endif
> > +     "^__pfx_.*$"                            // NOP-padding
> > +};
> > +
> > +int suffix_serial;
> > +
> > +static inline void verbose_msg(bool verbose, const char *fmt, ...)
> > +{
> > +     va_list args;
> > +
> > +     va_start(args, fmt);
> > +     if (verbose)
> > +             printf(fmt, args);
> > +
> > +     va_end(args);
> > +}
> > +
> > +static void create_suffix(const char *name, char *output_suffix)
> > +{
> > +     sprintf(output_suffix, "%s__alias__%d", name, suffix_serial++);
> > +}
> > +
> > +static void create_file_suffix(const char *name, uint64_t address, char
> > *output_suffix, char *cwd) +{
> > +     const char *f_path;
> > +     char *buf;
> > +     int i = 0;
> > +
> > +     buf = addr2line_get_lines(address);
> > +     f_path = remove_subdir(cwd, buf);
> > +     if (f_path) {
> > +             sprintf(output_suffix, "%s@%s", name, f_path);
> > +             while (*(output_suffix + i) != '\0') {
> > +                     switch (*(output_suffix + i)) {
> > +                     case '/':
> > +                     case ':':
> > +                     case '.':
> > +                             *(output_suffix + i) = '_';
> > +                             break;
> > +                     default:
> > +                     }
> > +             i++;
> > +             }
> > +     } else {
> > +             create_suffix(name, output_suffix);
> > +     }
> > +}
> > +
> > +static int filter_symbols(char *symbol, const char **ignore_list, int
> > regex_no) +{
> > +     regex_t regex;
> > +     int res, i;
> > +
> > +     for (i = 0; i < regex_no; i++) {
> > +             res = regcomp(&regex, ignore_list[i], REG_EXTENDED);
> > +             if (res)
> > +                     return -EREGEX;
> > +
> > +             res = regexec(&regex, symbol, 0, NULL, 0);
> > +             regfree(&regex);
> > +             switch (res) {
> > +             case 0:
> > +                     return FMATCH;
> > +             case REG_NOMATCH:
> > +                     break;
> > +             default:
> > +                     return -EREGEX;
> > +             }
> > +     }
> > +
> > +     return FNOMATCH;
> > +}
> > +
> > +int main(int argc, char *argv[])
> > +{
> > +     char t, sym_name[MAX_NAME_SIZE], new_name[MAX_NAME_SIZE + 15];
> > +     struct duplicate_item  *duplicate_iterator;
> > +     struct duplicate_item *duplicate;
> > +     struct item *head = {NULL};
> > +     bool need_2_process = true;
> > +     struct item *last = {NULL};
> > +     struct item  *current;
> > +     int verbose_mode = 0;
> > +     uint64_t address;
> > +     FILE *fp;
> > +     int res;
> > +
> > +     if (argc < 2 || argc > 3) {
> > +             printf("Usage: %s <nmfile> [-verbose]\n", argv[0]);
> > +             return 1;
> > +     }
> > +
> > +     if (argc == 3 && strcmp(argv[2], "-verbose") == 0)
> > +             verbose_mode = 1;
> > +
> > +     verbose_msg(verbose_mode, "Scanning nm data(%s)\n", argv[1]);
> > +
> > +     fp = fopen(argv[1], "r");
> > +     if (!fp) {
> > +             printf("Can't open input file.\n");
> > +             return 1;
> > +     }
> > +
> > +     if (!addr2line_init(get_addr2line(A2L_DEFAULT), get_vmlinux(argv[1])))
> > +             return 1;
> > +
> > +     while (fscanf(fp, "%lx %c %99s\n", &address, &t, sym_name) == 3) {
> > +             if (strstr(sym_name, "@_")) {
> > +                     if (verbose_mode && need_2_process)
> > +                             printf("Already processed\n");
> > +                     need_2_process = false;
> > +                     }
> > +             last = add_item(&last, sym_name, t, address);
> > +             if (!last) {
> > +                     printf("Error in allocate memory\n");
> > +                     free_items(&head);
> > +                     return 1;
> > +             }
> > +
> > +             if (!head)
> > +                     head = last;
> > +     }
> > +
> > +     fclose(fp);
> > +
> > +     if (need_2_process) {
> > +             verbose_msg(verbose_mode, "Sorting nm data\n");
> > +             sort_list_m(&head, BY_NAME);
> > +             verbose_msg(verbose_mode, "Scanning nm data for duplicates\n");
> > +             duplicate = find_duplicates(head);
> > +             if (!duplicate) {
> > +                     printf("Error in duplicates list\n");
> > +                     return 1;
> > +             }
> > +
> > +             verbose_msg(verbose_mode, "Applying suffixes\n");
> > +             build_index(head);
> > +             duplicate_iterator = duplicate;
> > +             while (duplicate_iterator) {
> > +                     res = filter_symbols(duplicate_iterator->original_item-
> >symb_name,
> > +                                          ignore_regex, sizeof(ignore_regex) /
> > +                                          sizeof(ignore_regex[0]));
> > +                     if (res != FMATCH &&
> > +                         SYMB_NEEDS_ALIAS(duplicate_iterator->original_item))
> {
> > +                             if (res < 0)
> > +                                     return 1;
> > +
> > +                             create_file_suffix(duplicate_iterator-
> >original_item->symb_name,
> > +                                                duplicate_iterator-
> >original_item->addr,
> > +                                                new_name, vmlinux_path);
> > +                             if (!insert_after(head, duplicate_iterator-
> >original_item->addr,
> > +                                               new_name, duplicate_iterator-
> >original_item->addr,
> > +                                               duplicate_iterator-
> >original_item->stype))
> > +                                     return 1;
> > +                     }
> > +
> > +                     duplicate_iterator = duplicate_iterator->next;
> > +             }
> > +
> > +             sort_list_m(&head, BY_ADDRESS);
> > +     }
> > +     current = head;
> > +     while (current) {
> > +             printf("%08lx %c %s\n", current->addr, current->stype,
> > current->symb_name); +                current = current->next;
> > +     }
> > +
> > +     free_items(&head);
> > +     free_duplicates(&duplicate);
> > +     addr2line_cleanup();
> > +     return 0;
> > +}
> > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> > index a432b171be82..cacf60b597ce 100755
> > --- a/scripts/link-vmlinux.sh
> > +++ b/scripts/link-vmlinux.sh
> > @@ -89,8 +89,9 @@ vmlinux_link()
> >
> >       ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
> >
> > -     # The kallsyms linking does not need debug symbols included.
> > -     if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> > +     # The kallsyms linking does not need debug symbols included, unless
> the
> > KALLSYMS_ALIAS. +     if [ ! is_enabled CONFIG_KALLSYMS_ALIAS ] && \
> > +         [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> >               ldflags="${ldflags} ${wl}--strip-debug"
> >       fi
> >
> > @@ -161,7 +162,11 @@ kallsyms()
> >       fi
> >
> >       info KSYMS ${2}
> > -     scripts/kallsyms ${kallsymopt} ${1} > ${2}
> > +     if is_enabled CONFIG_KALLSYMS_ALIAS; then
> > +             ALIAS=".alias"
> > +             scripts/kas_alias/kas_alias ${1} >${1}${ALIAS}
> > +             fi
> > +     scripts/kallsyms ${kallsymopt} ${1}${ALIAS} > ${2}
> >  }
> >
> >  # Perform one step in kallsyms generation, including temporary linking of
>
> Best regards.
>
>
Cheers

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-08-30  6:00 ` Masami Hiramatsu
@ 2023-09-02  7:26   ` Alessandro Carminati
  2023-09-03 14:50     ` Masami Hiramatsu
  0 siblings, 1 reply; 16+ messages in thread
From: Alessandro Carminati @ 2023-09-02  7:26 UTC (permalink / raw)
  To: Masami Hiramatsu
  Cc: Steven Rostedt, Daniel Bristot de Oliveira, Josh Poimboeuf,
	Masahiro Yamada, Luis Chamberlain, Nathan Chancellor,
	Nick Desaulniers, Nicolas Schier, Alexander Lobakin, Nick Alcock,
	Kris Van Hees, Eugene Loh, Francis Laniel, Viktor Malik,
	linux-kbuild, linux-kernel, linux-trace-kernel, live-patching

Hey Masami,
Thanks a lot for your review and for your time.

Il giorno mer 30 ago 2023 alle ore 08:00 Masami Hiramatsu
<mhiramat@kernel.org> ha scritto:
>
> Hi Alessandro,
>
> Thanks for your update!
>
> On Mon, 28 Aug 2023 08:04:23 +0000
> "Alessandro Carminati (Red Hat)" <alessandro.carminati@gmail.com> wrote:
>
> > From: Alessandro Carminati <alessandro.carminati@gmail.com>
> >
> > It is not uncommon for drivers or modules related to similar peripherals
> > to have symbols with the exact same name.
> > While this is not a problem for the kernel's binary itself, it becomes an
> > issue when attempting to trace or probe specific functions using
> > infrastructure like ftrace or kprobe.
> >
> > The tracing subsystem relies on the `nm -n vmlinux` output, which provides
> > symbol information from the kernel's ELF binary. However, when multiple
> > symbols share the same name, the standard nm output does not differentiate
> > between them. This can lead to confusion and difficulty when trying to
> > probe the intended symbol.
> >
> >  ~ # cat /proc/kallsyms | grep " name_show"
> >  ffffffff8c4f76d0 t name_show
> >  ffffffff8c9cccb0 t name_show
> >  ffffffff8cb0ac20 t name_show
> >  ffffffff8cc728c0 t name_show
> >  ffffffff8ce0efd0 t name_show
> >  ffffffff8ce126c0 t name_show
> >  ffffffff8ce1dd20 t name_show
> >  ffffffff8ce24e70 t name_show
> >  ffffffff8d1104c0 t name_show
> >  ffffffff8d1fe480 t name_show
> >
> > **kas_alias** addresses this challenge by extending the symbol names with
> > unique suffixes during the kernel build process.
> > The newly created aliases for these duplicated symbols are unique names
> > that can be fed to the ftracefs interface. By doing so, it enables
> > previously unreachable symbols to be probed.
> >
> >  ~ # cat /proc/kallsyms | grep " name_show"
> >  ffffffff974f76d0 t name_show
> >  ffffffff974f76d0 t name_show__alias__6340
> >  ffffffff979cccb0 t name_show
> >  ffffffff979cccb0 t name_show__alias__6341
> >  ffffffff97b0ac20 t name_show
> >  ffffffff97b0ac20 t name_show__alias__6342
> >  ffffffff97c728c0 t name_show
> >  ffffffff97c728c0 t name_show__alias__6343
> >  ffffffff97e0efd0 t name_show
> >  ffffffff97e0efd0 t name_show__alias__6344
> >  ffffffff97e126c0 t name_show
> >  ffffffff97e126c0 t name_show__alias__6345
> >  ffffffff97e1dd20 t name_show
> >  ffffffff97e1dd20 t name_show__alias__6346
> >  ffffffff97e24e70 t name_show
> >  ffffffff97e24e70 t name_show__alias__6347
> >  ffffffff981104c0 t name_show
> >  ffffffff981104c0 t name_show__alias__6348
> >  ffffffff981fe480 t name_show
> >  ffffffff981fe480 t name_show__alias__6349
> >  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
> >  > >/sys/kernel/tracing/kprobe_events
> >  ~ # cat /sys/kernel/tracing/kprobe_events
> >  p:kprobes/evnt1 name_show__alias__6349
> >
> > Changes from v1:
> > - Integrated changes requested by Masami to exclude symbols with prefixes
> >   "_cfi" and "_pfx".
> > - Introduced a small framework to handle patterns that need to be excluded
> >   from the alias production.
> > - Excluded other symbols using the framework.
> > - Introduced the ability to discriminate between text and data symbols.
> > - Added two new config symbols in this version: CONFIG_KALLSYMS_ALIAS_DATA,
> >   which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
> >   excludes all filters and provides an alias for each duplicated symbol.
> >
> > https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gmail.com/
> >
> > Changes from v2:
> > - Alias tags are created by querying DWARF information from the vmlinux.
> > - The filename + line number is normalized and appended to the original name.
> > - The tag begins with '@' to indicate the symbol source.
> > - Not a change, but worth mentioning, since the alias is added to the existing
> >   list, the old duplicated name is preserved, and the livepatch way of dealing
> >   with duplicates is maintained.
> > - Acknowledging the existence of scenarios where inlined functions declared in
> >   header files may result in multiple copies due to compiler behavior, though
> >    it is not actionable as it does not pose an operational issue.
> > - Highlighting a single exception where the same name refers to different
> >   functions: the case of "compat_binfmt_elf.c," which directly includes
> >   "binfmt_elf.c" producing identical function copies in two separate
> >   modules.
> >
> > sample from new v3
> >
> >  ~ # cat /proc/kallsyms | grep gic_mask_irq
> >  ffffd0b03c04dae4 t gic_mask_irq
> >  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
> >  ffffd0b03c050960 t gic_mask_irq
> >  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
>
> Could you also update the sample output in the patch description?
> And I can not see this line information but a serial number aliases,
> is there any way to enable this file-name aliases? (LLVM is not supported?)
> I think we'd better to have a new CONFIG_KALLSYMS_ALIAS_SRCLINE and
> clarify what is required.
In this version of the patch, there's still a fallback action that
produces the old "__alias__<seqnum>" if the addr2line action fails.
In the v3 patch, addr2line is default to the native option.
The CROSS_COMPILE setting remains a manual selection. While in my tests,
I didn't encounter any issues, and the native addr2line worked well on
all the architectures I tested, there is still a possibility of failure
leading to the fallback action. Somthing I will change in the v4.

Additionally, if CONFIG_KALLSYMS_ALIAS_DATA is set to 'Y,' data names
included in the KALLSYMS receive an old-style alias.
Regarding this matter, I'd like to discuss with you the relevance of
CONFIG_KALLSYMS_ALIAS_DATA and CONFIG_KALLSYMS_ALIAS_DATA_ALL.
Both of these settings aim to provide an alias for variable names as
well. In the past, I had to "livepatch" a function for an architecture
that had no support, and I thought it would be beneficial to have
unique variable names as well. What are your thoughts on this?
>
> >  ~ #
> >
> > https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gmail.com/
> >
> > Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> > ---
> >  init/Kconfig                        |  36 ++++
> >  scripts/Makefile                    |   4 +
> >  scripts/kas_alias/Makefile          |   4 +
> >  scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
> >  scripts/kas_alias/a2l.h             |  32 ++++
> >  scripts/kas_alias/duplicates_list.c |  70 ++++++++
> >  scripts/kas_alias/duplicates_list.h |  15 ++
> >  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
> >  scripts/kas_alias/item_list.h       |  26 +++
> >  scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
> >  scripts/link-vmlinux.sh             |  11 +-
> >  11 files changed, 910 insertions(+), 3 deletions(-)
> >  create mode 100644 scripts/kas_alias/Makefile
> >  create mode 100644 scripts/kas_alias/a2l.c
> >  create mode 100644 scripts/kas_alias/a2l.h
> >  create mode 100644 scripts/kas_alias/duplicates_list.c
> >  create mode 100644 scripts/kas_alias/duplicates_list.h
> >  create mode 100644 scripts/kas_alias/item_list.c
> >  create mode 100644 scripts/kas_alias/item_list.h
> >  create mode 100644 scripts/kas_alias/kas_alias.c
> >
> > diff --git a/init/Kconfig b/init/Kconfig
> > index f7f65af4ee12..bc69fcd9cbc8 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -1737,6 +1737,42 @@ config KALLSYMS_BASE_RELATIVE
> >         time constants, and no relocation pass is required at runtime to fix
> >         up the entries based on the runtime load address of the kernel.
> >
> > +config KALLSYMS_ALIAS
> > +     bool "Produces alias for duplicated symbols" if EXPERT
> > +     depends on KALLSYMS && (DEBUG_INFO_DWARF4 || DEBUG_INFO_DWARF5)
> > +     help
> > +       It is not uncommon for drivers or modules related to similar
> > +       peripherals to have symbols with the exact same name.
> > +       While this is not a problem for the kernel's binary itself, it
> > +       becomes an issue when attempting to trace or probe specific
> > +       functions using infrastructure like ftrace or kprobe.
> > +
> > +       This option addresses this challenge by extending the symbol names
> > +       with unique suffixes during the kernel build process.
> > +       The newly created aliases for these duplicated symbols are unique
> > +       names that can be fed to the ftrace sysfs interface. By doing so, it
> > +       enables previously unreachable symbols to be probed.
> > +
> > +config CONFIG_KALLSYMS_ALIAS_DATA
>
> You don't need 'CONFIG_' prefix here.
>
> > +     bool "Produces alias also for data"
> > +     depends on KALLSYMS_ALIAS
> > +     help
> > +       Sometimes it can be useful to refer to data. In live patch scenarios,
> > +       you may find yourself needing to use symbols that are shared with
> > +       other functions. Since symbols face the same issue as functions, this
> > +       option allows you to create aliases for data as well.
> > +
> > +config CONFIG_KALLSYMS_ALIAS_DATA_ALL
> > +     bool "Removes all filter when producing data alias"
> > +     depends on CONFIG_KALLSYMS_ALIAS_DATA
> > +     help
> > +       When selecting data aliases, not all symbols are included in the set
> > +       This is because many symbols are unlikely to be used. If you choose
> > +       to have an alias for all data symbols, be aware that it will
> > +       significantly increase the size.
> > +
> > +       If unsure, say N.
> > +
> >  # end of the "standard kernel features (expert users)" menu
> >
> >  # syscall, maps, verifier
> > diff --git a/scripts/Makefile b/scripts/Makefile
> > index 32b6ba722728..65fafe17cfe5 100644
> > --- a/scripts/Makefile
> > +++ b/scripts/Makefile
> > @@ -49,3 +49,7 @@ subdir-$(CONFIG_SECURITY_SELINUX) += selinux
> >
> >  # Let clean descend into subdirs
> >  subdir-      += basic dtc gdb kconfig mod
> > +
> > +# KALLSyms alias
> > +subdir-$(CONFIG_KALLSYMS_ALIAS) += kas_alias
> > +
> > diff --git a/scripts/kas_alias/Makefile b/scripts/kas_alias/Makefile
> > new file mode 100644
> > index 000000000000..e1fde69232b4
> > --- /dev/null
> > +++ b/scripts/kas_alias/Makefile
> > @@ -0,0 +1,4 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +hostprogs-always-$(CONFIG_KALLSYMS_ALIAS)    += kas_alias
> > +
> > +kas_alias-objs        := duplicates_list.o item_list.o kas_alias.o a2l.o
> > diff --git a/scripts/kas_alias/a2l.c b/scripts/kas_alias/a2l.c
> > new file mode 100644
> > index 000000000000..a9692ac30180
> > --- /dev/null
> > +++ b/scripts/kas_alias/a2l.c
> > @@ -0,0 +1,268 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +#include <sys/types.h>
> > +#include <sys/wait.h>
> > +#include <string.h>
> > +#include <stdint.h>
> > +#include <stdbool.h>
> > +
> > +#include "a2l.h"
> > +
> > +int addr2line_pid = -1;
> > +int a2l_in[2];
> > +int a2l_out[2];
> > +char line[MAX_BUF];
> > +char vmlinux_path[MAX_BUF];
> > +char addr2line_cmd[MAX_CMD_LEN];
> > +FILE *a2l_stdin, *a2l_stdout;
> > +
> > +static char *normalize_path(const char *input_path, char *output_path)
> > +{
> > +     char *prev_token = NULL;
> > +     char *delimiter = "/";
> > +     char inbuf[MAX_BUF];
> > +     char *token;
> > +     char *pos;
> > +
> > +     memset(inbuf, 0, MAX_BUF);
> > +     *output_path = '\0';
> > +     strncpy(inbuf, input_path, MAX_BUF);
> > +     if (!input_path || !output_path || strlen(input_path) == 0)
> > +             return NULL;
> > +
> > +     token = strtok(inbuf, delimiter);
> > +     while (token) {
> > +             if (strcmp(token, "..") == 0 && prev_token) {
> > +                     pos = strrchr(output_path, '/');
> > +                     if (pos)
> > +                             *pos = '\0';
> > +
> > +             } else if (strcmp(token, ".") != 0) {
> > +                     strcat(output_path, "/");
> > +                     strcat(output_path, token);
> > +             }
> > +
> > +             prev_token = token;
> > +             token = strtok(NULL, delimiter);
> > +     }
> > +
> > +     return output_path;
> > +}
> > +
> > +static void path_of(const char *full_path, char *path)
> > +{
> > +     const char *last_slash = strrchr(full_path, '/');
> > +     size_t path_length;
> > +     char cwd[MAX_BUF];
> > +
> > +     if (!last_slash) {
> > +             if (getcwd(cwd, sizeof(cwd)))
> > +                     strcpy(path, cwd);
> > +             else
> > +                     strcpy(path, ".");
> > +     } else {
> > +             path_length = last_slash - full_path;
> > +             strncpy(path, full_path, path_length);
> > +             path[path_length] = '\0';
> > +     }
> > +}
> > +
> > +static bool file_exists(const char *file_path)
> > +{
> > +     FILE *file;
> > +
> > +     file = fopen(file_path, "r");
> > +     if (file) {
> > +             fclose(file);
> > +             return true;
> > +     }
> > +     return false;
> > +}
> > +
> > +int addr2line_init(const char *cmd, const char *vmlinux)
> > +{
> > +     if ((!file_exists(cmd)) || (!file_exists(vmlinux))) {
> > +             printf("file not found\n");
> > +             return 0;
> > +             }
>
> nit: mis-indentation?
>
> > +
> > +     path_of(vmlinux, vmlinux_path);
> > +     if (pipe(a2l_in) == -1) {
> > +             printf("Failed to create pipe\n");
> > +             return 0;
> > +     }
> > +
> > +     if (pipe(a2l_out) == -1) {
> > +             printf("Failed to create pipe\n");
> > +             return 0;
> > +     }
> > +
> > +     addr2line_pid = fork();
> > +     if (addr2line_pid == -1) {
> > +             printf("Failed to fork process\n");
> > +             close(a2l_in[P_READ]);
> > +             close(a2l_in[P_WRITE]);
> > +             close(a2l_out[P_READ]);
> > +             close(a2l_out[P_WRITE]);
> > +             return 0;
> > +     }
> > +
> > +     if (addr2line_pid == 0) {
> > +             dup2(a2l_in[P_READ], 0);
> > +             dup2(a2l_out[P_WRITE], 1);
> > +             close(a2l_in[P_WRITE]);
> > +             close(a2l_out[P_READ]);
> > +
> > +             execlp(cmd, cmd, ADDR2LINE_ARGS, vmlinux, NULL);
> > +
> > +             printf("Failed to execute addr2line command\n");
> > +             exit(1);
> > +     } else {
> > +             close(a2l_in[P_READ]);
> > +             close(a2l_out[P_WRITE]);
> > +     }
> > +
> > +     a2l_stdin = fdopen(a2l_in[P_WRITE], "w");
> > +     if (!a2l_stdin) {
> > +             printf("Failed to open pipe a2l_in\n");
> > +             return 0;
> > +     }
> > +
> > +     a2l_stdout = fdopen(a2l_out[P_READ], "r");
> > +     if (!a2l_stdout) {
> > +             printf("Failed to open pipe a2l_out\n");
> > +             fclose(a2l_stdin);
> > +             return 0;
> > +     }
> > +
> > +     return 1;
> > +}
> > +
> > +const char *remove_subdir(const char *home, const char *f_path)
> > +{
> > +     int i = 0;
> > +
> > +     while (*(home + i) == *(f_path + i))
> > +             i++;
> > +
> > +     return (strlen(home) != i) ? NULL : f_path + i;
> > +}
> > +
> > +char *addr2line_get_lines(uint64_t address)
> > +{
> > +     char buf[MAX_BUF];
> > +
> > +     fprintf(a2l_stdin, "%08lx\n", address);
> > +     fflush(a2l_stdin);
> > +
> > +     if (!fgets(line, sizeof(line), a2l_stdout)) {
> > +             printf("Failed to read lines from addr2line\n");
> > +             return NULL;
> > +     }
> > +
> > +     if (!fgets(line, sizeof(line), a2l_stdout)) {
> > +             printf("Failed to read lines from addr2line\n");
> > +             return NULL;
> > +     }
> > +
> > +     line[strcspn(line, "\n")] = '\0';
> > +     strncpy(buf, line, MAX_BUF);
> > +     return normalize_path(buf, line);
> > +}
> > +
> > +int addr2line_cleanup(void)
> > +{
> > +     int status;
> > +
> > +     if (addr2line_pid != -1) {
> > +             kill(addr2line_pid, SIGKILL);
> > +             waitpid(addr2line_pid, &status, 0);
> > +             fclose(a2l_stdin);
> > +             fclose(a2l_stdout);
> > +             addr2line_pid = -1;
> > +     }
> > +
> > +     return 1;
> > +}
> > +
> > +static char *find_executable(const char *command)
> > +{
> > +     char *path_env = getenv("PATH");
> > +     char *executable_path;
> > +     char *path_copy;
> > +     char *path;
> > +     int n;
> > +
> > +     if (!path_env)
> > +             return NULL;
> > +
> > +     path_copy = strdup(path_env);
> > +     if (!path_copy)
> > +             return NULL;
> > +
> > +     path = strtok(path_copy, ":");
> > +     while (path) {
> > +             n = snprintf(0, 0, "%s/%s", path, command);
> > +             executable_path = (char *)malloc(n + 1);
> > +             snprintf(executable_path, n + 1, "%s/%s", path, command);
> > +             if (access(executable_path, X_OK) == 0) {
> > +                     free(path_copy);
> > +                     return executable_path;
> > +             }
> > +
> > +     path = strtok(NULL, ":");
> > +     free(executable_path);
> > +     executable_path = NULL;
>
> nit: mis-indentation?
>
> > +     }
> > +
> > +     free(path_copy);
> > +     if (executable_path)
> > +             free(executable_path);
> > +     return NULL;
> > +}
> > +
> > +const char *get_addr2line(int mode)
> > +{
> > +     char *buf = "";
> > +
> > +     switch (mode) {
> > +     case A2L_CROSS:
> > +             buf = getenv("CROSS_COMPILE");
> > +             memcpy(addr2line_cmd, buf, strlen(buf));
> > +     case A2L_DEFAULT:
> > +             memcpy(addr2line_cmd + strlen(buf), ADDR2LINE, strlen(ADDR2LINE));
> > +             buf = find_executable(addr2line_cmd);
> > +             if (buf) {
> > +                     memcpy(addr2line_cmd, buf, strlen(buf));
> > +                     free(buf);
> > +             }
> > +             return addr2line_cmd;
> > +     case A2L_LLVM:
> > +     default:
> > +             return NULL;
> > +     }
> > +}
> > +
> > +char *get_vmlinux(char *input)
> > +{
> > +     const char *match_string1 = ".syms";
> > +     const char *match_string2 = ".tmp_vmlinux.kallsyms";
> > +     char *result = NULL;
> > +     char *match_pos;
> > +
> > +     match_pos = strstr(input, match_string1);
> > +     if (!match_pos)
> > +             return NULL;
> > +
> > +     match_pos = strstr(input, match_string2);
> > +     if (!match_pos)
> > +             return NULL;
> > +
> > +     result = strdup(input);
> > +     match_pos = strstr(result, match_string1);
> > +     *match_pos = '\0';
> > +     return result;
> > +}
> > diff --git a/scripts/kas_alias/a2l.h b/scripts/kas_alias/a2l.h
> > new file mode 100644
> > index 000000000000..ca6419229dde
> > --- /dev/null
> > +++ b/scripts/kas_alias/a2l.h
> > @@ -0,0 +1,32 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +#ifndef A2L_H
> > +#define A2L_H
> > +#include <stdint.h>
> > +
> > +#define ADDR2LINE "addr2line"
> > +#define ADDR2LINE_ARGS "-fe"
> > +//#define VMLINUX "vmlinux"
>
> Nit: this should be removed if it is not used.
>
> > +#define MAX_BUF 4096
> > +#define MAX_CMD_LEN 256
> > +#define P_READ 0
> > +#define P_WRITE 1
> > +#define A2L_DEFAULT 1
> > +#define A2L_CROSS 2
> > +#define A2L_LLVM 3
> > +#define A2L_MAKE_VALUE 2
> > +
> > +extern int addr2line_pid;
> > +extern int a2l_in[2];
> > +extern int a2l_out[2];
> > +extern char line[MAX_BUF];
> > +extern char vmlinux_path[MAX_BUF];
> > +extern char addr2line_cmd[MAX_CMD_LEN];
> > +
> > +int addr2line_init(const char *cmd, const char *vmlinux);
> > +char *addr2line_get_lines(uint64_t address);
> > +int addr2line_cleanup(void);
> > +const char *remove_subdir(const char *home, const char *f_path);
> > +const char *get_addr2line(int mode);
> > +char *get_vmlinux(char *input);
> > +
> > +#endif
> > diff --git a/scripts/kas_alias/duplicates_list.c b/scripts/kas_alias/duplicates_list.c
> > new file mode 100644
> > index 000000000000..e7a3d2917937
> > --- /dev/null
> > +++ b/scripts/kas_alias/duplicates_list.c
> > @@ -0,0 +1,70 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdint.h>
> > +#include <stdio.h>
> > +#include <string.h>
> > +#include <stdlib.h>
> > +#include <stdbool.h>
> > +
> > +#include "item_list.h"
> > +#include "duplicates_list.h"
> > +
>
> /* The item list must be sorted. */
>
> I think we can find the duplicated symbol without sorting the list,
> but such implementation level optimization will be done later.

I think I will handle this aspect in the v4.

>
> > +struct duplicate_item *find_duplicates(struct item *list)
> > +{
> > +     struct duplicate_item *current_duplicate = NULL;
> > +     struct duplicate_item *duplicates = NULL;
> > +     struct duplicate_item *new_duplicate;
> > +     struct item *current_item = list;
> > +     bool prev_was_duplicate = false;
> > +     struct item *prev_item = NULL;
> > +
> > +     while (current_item) {
> > +             if ((prev_item && (strcmp(current_item->symb_name, prev_item->symb_name) == 0)) ||
> > +                 prev_was_duplicate) {
> > +                     if (!duplicates) {
> > +                             duplicates = malloc(sizeof(struct duplicate_item));
> > +                             if (!duplicates)
> > +                                     return NULL;
> > +
> > +                             duplicates->original_item = prev_item;
> > +                             duplicates->next = NULL;
> > +                             current_duplicate = duplicates;
> > +                     } else {
> > +                             new_duplicate = malloc(sizeof(struct duplicate_item));
> > +                             if (!new_duplicate) {
> > +                                     free_duplicates(&duplicates);
> > +                                     return NULL;
> > +                             }
> > +
> > +                             new_duplicate->original_item = prev_item;
> > +                             new_duplicate->next = NULL;
> > +                             current_duplicate->next = new_duplicate;
> > +                             current_duplicate = new_duplicate;
> > +
> > +                             if ((strcmp(current_item->symb_name, prev_item->symb_name) != 0) &&
> > +                                 (prev_was_duplicate))
> > +                                     prev_was_duplicate = false;
> > +                             else
> > +                                     prev_was_duplicate = true;
> > +                     }
> > +             }
> > +
> > +             prev_item = current_item;
> > +             current_item = current_item->next;
> > +     }
> > +
> > +     return duplicates;
> > +}
> > +
> > +void free_duplicates(struct duplicate_item **duplicates)
> > +{
> > +     struct duplicate_item *duplicates_iterator = *duplicates;
> > +     struct duplicate_item *app;
> > +
> > +     while (duplicates_iterator) {
> > +             app = duplicates_iterator;
> > +             duplicates_iterator = duplicates_iterator->next;
> > +             free(app);
> > +     }
> > +
> > +     *duplicates = NULL;
> > +}
> > diff --git a/scripts/kas_alias/duplicates_list.h b/scripts/kas_alias/duplicates_list.h
> > new file mode 100644
> > index 000000000000..76aa73e584bc
> > --- /dev/null
> > +++ b/scripts/kas_alias/duplicates_list.h
> > @@ -0,0 +1,15 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +#ifndef DUPLICATES_LIST_H
> > +#define DUPLICATES_LIST_H
> > +
> > +#include "item_list.h"
> > +
> > +struct duplicate_item {
> > +     struct item *original_item;
> > +     struct duplicate_item *next;
> > +};
> > +
> > +struct duplicate_item *find_duplicates(struct item *list);
> > +void free_duplicates(struct duplicate_item **duplicates);
> > +
> > +#endif
> > diff --git a/scripts/kas_alias/item_list.c b/scripts/kas_alias/item_list.c
> > new file mode 100644
> > index 000000000000..48f2e525592a
> > --- /dev/null
> > +++ b/scripts/kas_alias/item_list.c
> > @@ -0,0 +1,230 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <stdint.h>
> > +#include <string.h>
> > +#include <stdbool.h>
> > +#include <assert.h>
> > +#include "item_list.h"
> > +
> > +#define CHECK_ORDER_BY_ADDRESS(sort_by, current, temp, op) \
> > +     ((sort_by) == BY_ADDRESS && (current)->addr op (temp)->addr)
> > +#define CHECK_ORDER_BY_NAME(sort_by, current, temp, op) \
> > +     ((sort_by) == BY_NAME && strcmp((current)->symb_name, (temp)->symb_name) op 0)
> > +
> > +struct item *list_index[96] = {0};
> > +
> > +void build_index(struct item *list)
> > +{
> > +     char current_first_letter = ' ';
> > +     struct item *current = list;
> > +
> > +     while (current) {
> > +             if (current->symb_name[0] != current_first_letter) {
> > +                     current_first_letter = current->symb_name[0];
> > +                     list_index[current_first_letter - 32] = current;
> > +             }
> > +             current = current->next;
> > +     }
> > +}
> > +
> > +struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr)
> > +{
> > +     struct item *new_item;
> > +     struct item *current;
> > +
> > +     new_item = malloc(sizeof(struct item));
> > +     if (!new_item)
> > +             return NULL;
> > +
> > +     strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> > +     new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> > +     new_item->addr = addr;
> > +     new_item->stype = stype;
> > +     new_item->next = NULL;
> > +
> > +     if (!(*list)) {
> > +             *list = new_item;
> > +     } else {
> > +             current = *list;
> > +             while (current->next)
> > +                     current = current->next;
> > +
> > +             current->next = new_item;
> > +     }
> > +     return new_item;
> > +}
> > +
> > +void sort_list(struct item **list, int sort_by)
> > +{
> > +     struct item *current = *list;
> > +     struct item *sorted = NULL;
> > +     struct item *next_item;
> > +     struct item *temp;
> > +
> > +     if (!(*list) || !((*list)->next))
> > +             return;
> > +
> > +     while (current) {
> > +             next_item = current->next;
> > +             if (!sorted ||
> > +                 (CHECK_ORDER_BY_ADDRESS(sort_by, current, sorted, <) ||
> > +                 CHECK_ORDER_BY_NAME(sort_by, current, sorted, >=))) {
> > +                     current->next = sorted;
> > +                     sorted = current;
> > +             } else {
> > +                     temp = sorted;
> > +                     while (temp->next &&
> > +                            (CHECK_ORDER_BY_ADDRESS(sort_by, current, temp->next, >=) ||
> > +                            CHECK_ORDER_BY_NAME(sort_by, current, temp->next, >=)))
> > +                             temp = temp->next;
> > +
> > +                     current->next = temp->next;
> > +                     temp->next = current;
> > +             }
> > +             current = next_item;
> > +     }
> > +
> > +     *list = sorted;
> > +}
> > +
> > +struct item *merge(struct item *left, struct item *right, int sort_by)
> > +{
> > +     struct item *current = NULL;
> > +     struct item *result = NULL;
> > +
> > +     if (!left)
> > +             return right;
> > +     if (!right)
> > +             return left;
> > +
> > +     if (sort_by == BY_NAME) {
> > +             if (strcmp(left->symb_name, right->symb_name) <= 0) {
> > +                     result = left;
> > +                     left = left->next;
> > +             } else {
> > +                     result = right;
> > +                     right = right->next;
> > +             }
> > +     } else {
> > +             if (sort_by == BY_ADDRESS) {
> > +                     if (left->addr <= right->addr) {
> > +                             result = left;
> > +                             left = left->next;
> > +                     } else {
> > +                             result = right;
> > +                             right = right->next;
> > +                     }
> > +             }
> > +     }
> > +
> > +     current = result;
> > +
> > +     while (left && right) {
> > +             if (sort_by == BY_NAME) {
> > +                     if (strcmp(left->symb_name, right->symb_name) <= 0) {
> > +                             current->next = left;
> > +                             left = left->next;
> > +                     } else {
> > +                             current->next = right;
> > +                             right = right->next;
> > +                     }
> > +             } else {
> > +                     if (sort_by == BY_ADDRESS) {
> > +                             if (left->addr <= right->addr) {
> > +                                     current->next = left;
> > +                                     left = left->next;
> > +                             } else {
> > +                                     current->next = right;
> > +                                     right = right->next;
> > +                             }
> > +                     }
> > +             }
> > +
> > +             current = current->next;
> > +     }
> > +
> > +     if (left) {
> > +             current->next = left;
> > +     } else {
> > +             if (right)
> > +                     current->next = right;
> > +     }
> > +
> > +     return result;
> > +}
> > +
> > +struct item *merge_sort(struct item *head, int sort_by)
> > +{
> > +     struct item *right;
> > +     struct item *slow;
> > +     struct item *fast;
> > +     struct item *left;
> > +
> > +     if (!head || !head->next)
> > +             return head;
> > +
> > +     slow = head;
> > +     fast = head->next;
> > +
> > +     while (fast && fast->next) {
> > +             slow = slow->next;
> > +             fast = fast->next->next;
> > +     }
> > +
> > +     left = head;
> > +     right = slow->next;
> > +     slow->next = NULL;
> > +
> > +     left = merge_sort(left, sort_by);
> > +     right = merge_sort(right, sort_by);
> > +
> > +     return merge(left, right, sort_by);
> > +}
> > +
> > +void sort_list_m(struct item **head, int sort_by)
> > +{
> > +     if (!(*head) || !((*head)->next))
> > +             return;
> > +
> > +     *head = merge_sort(*head, sort_by);
> > +}
> > +
> > +int insert_after(struct item *list, const uint64_t search_addr,
> > +              const char *name, uint64_t addr, char stype)
> > +{
> > +     struct item *new_item;
> > +     struct item *current;
> > +     int ret = 0;
> > +
> > +     current = (list_index[name[0] - 32]) ? list_index[name[0] - 32] : list;
> > +     while (current) {
> > +             if (current->addr == search_addr) {
> > +                     new_item = malloc(sizeof(struct item));
> > +                     if (!new_item)
> > +                             return ret;
> > +                     strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> > +                     new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> > +                     new_item->addr = addr;
> > +                     new_item->stype = stype;
> > +                     new_item->next = current->next;
> > +                     current->next = new_item;
> > +                     ret = 1;
> > +                     break;
> > +             }
> > +             current = current->next;
> > +     }
> > +     return ret;
> > +}
> > +
> > +void free_items(struct item **head)
> > +{
> > +     struct item *app, *item_iterator = *head;
> > +
> > +     while (item_iterator) {
> > +             app = item_iterator;
> > +             item_iterator = item_iterator->next;
> > +             free(app);
> > +     }
> > +     *head = NULL;
> > +}
> > diff --git a/scripts/kas_alias/item_list.h b/scripts/kas_alias/item_list.h
> > new file mode 100644
> > index 000000000000..b4891cb088ee
> > --- /dev/null
> > +++ b/scripts/kas_alias/item_list.h
> > @@ -0,0 +1,26 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +#ifndef ITEM_LIST_H
> > +#define ITEM_LIST_H
> > +#include <stdint.h>
> > +
> > +#define MAX_NAME_SIZE 256
> > +#define BY_ADDRESS 1
> > +#define BY_NAME 2
> > +
> > +struct item {
> > +     char            symb_name[MAX_NAME_SIZE];
> > +     uint64_t        addr;
> > +     char            stype;
> > +     struct item     *next;
> > +};
> > +
> > +void build_index(struct item *list);
> > +struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr);
> > +void sort_list(struct item **list, int sort_by);
> > +struct item *merge(struct item *left, struct item *right, int sort_by);
> > +struct item *merge_sort(struct item *head, int sort_by);
> > +void sort_list_m(struct item **head, int sort_by);
> > +int insert_after(struct item *list, const uint64_t search_addr,
> > +              const char *name, uint64_t addr, char stype);
> > +void free_items(struct item **head);
> > +#endif
> > diff --git a/scripts/kas_alias/kas_alias.c b/scripts/kas_alias/kas_alias.c
> > new file mode 100644
> > index 000000000000..532aeb39f851
> > --- /dev/null
> > +++ b/scripts/kas_alias/kas_alias.c
> > @@ -0,0 +1,217 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <stdint.h>
> > +#include <unistd.h>
> > +#include <string.h>
> > +#include <stdbool.h>
> > +#include <stdarg.h>
> > +#include <regex.h>
> > +
> > +#include "item_list.h"
> > +#include "duplicates_list.h"
> > +#include "a2l.h"
> > +
> > +#define SYMB_IS_TEXT(s) ((((s)->stype) == 't') ||  (((s)->stype) == 'T'))
> > +#define SYMB_IS_DATA(s) ((((s)->stype) == 'b') ||  (((s)->stype) == 'B') || \
> > +                      (((s)->stype) == 'd') ||  (((s)->stype) == 'D') || \
> > +                      (((s)->stype) == 'r') ||  (((s)->stype) == 'R'))
> > +#ifdef CONFIG_KALLSYMS_ALIAS_DATA
> > +#define SYMB_NEEDS_ALIAS(s) (SYMB_IS_TEXT(s) || SYMB_IS_DATA(s))
> > +#else
> > +#define SYMB_NEEDS_ALIAS(s) SYMB_IS_TEXT(s)
> > +#endif
> > +#define FNOMATCH 0
> > +#define FMATCH 1
> > +#define EREGEX 2
> > +
> > +const char *ignore_regex[] = {
> > +     "^__cfi_.*$",                           // __cfi_ preamble
> > +#ifndef CONFIG_KALLSYMS_ALIAS_DATA_ALL
> > +     "^_*TRACE_SYSTEM.*$",
> > +     "^__already_done\\.[0-9]+$",            // Call a function once data
> > +     "^___tp_str\\.[0-9]+$",
> > +     "^___done\\.[0-9]+$",
> > +     "^__print_once\\.[0-9]+$",
> > +     "^_rs\\.[0-9]+$",
> > +     "^__compound_literal\\.[0-9]+$",
> > +     "^___once_key\\.[0-9]+$",
> > +     "^__func__\\.[0-9]+$",
> > +     "^__msg\\.[0-9]+$",
> > +     "^CSWTCH\\.[0-9]+$",
> > +     "^__flags\\.[0-9]+$",
> > +     "^__wkey.*$",
> > +     "^__mkey.*$",
> > +     "^__key.*$",
> > +#endif
> > +     "^__pfx_.*$"                            // NOP-padding
> > +};
> > +
> > +int suffix_serial;
> > +
> > +static inline void verbose_msg(bool verbose, const char *fmt, ...)
> > +{
> > +     va_list args;
> > +
> > +     va_start(args, fmt);
> > +     if (verbose)
> > +             printf(fmt, args);
> > +
> > +     va_end(args);
> > +}
> > +
> > +static void create_suffix(const char *name, char *output_suffix)
> > +{
> > +     sprintf(output_suffix, "%s__alias__%d", name, suffix_serial++);
> > +}
> > +
> > +static void create_file_suffix(const char *name, uint64_t address, char *output_suffix, char *cwd)
> > +{
> > +     const char *f_path;
> > +     char *buf;
> > +     int i = 0;
> > +
> > +     buf = addr2line_get_lines(address);
> > +     f_path = remove_subdir(cwd, buf);
> > +     if (f_path) {
> > +             sprintf(output_suffix, "%s@%s", name, f_path);
> > +             while (*(output_suffix + i) != '\0') {
> > +                     switch (*(output_suffix + i)) {
> > +                     case '/':
> > +                     case ':':
> > +                     case '.':
>
> This is not enough because file path will accept more than that.
> E.g. '+', '&', '-'.
> So I think we should check it by '!isalnum()'. (allow-list method)
>
> > +                             *(output_suffix + i) = '_';
> > +                             break;
> > +                     default:
> > +                     }
> > +             i++;
> > +             }
> > +     } else {
> > +             create_suffix(name, output_suffix);
> > +     }
> > +}
> > +
> > +static int filter_symbols(char *symbol, const char **ignore_list, int regex_no)
> > +{
> > +     regex_t regex;
> > +     int res, i;
> > +
> > +     for (i = 0; i < regex_no; i++) {
> > +             res = regcomp(&regex, ignore_list[i], REG_EXTENDED);
> > +             if (res)
> > +                     return -EREGEX;
> > +
> > +             res = regexec(&regex, symbol, 0, NULL, 0);
> > +             regfree(&regex);
> > +             switch (res) {
> > +             case 0:
> > +                     return FMATCH;
> > +             case REG_NOMATCH:
> > +                     break;
> > +             default:
> > +                     return -EREGEX;
> > +             }
> > +     }
> > +
> > +     return FNOMATCH;
> > +}
> > +
> > +int main(int argc, char *argv[])
> > +{
> > +     char t, sym_name[MAX_NAME_SIZE], new_name[MAX_NAME_SIZE + 15];
> > +     struct duplicate_item  *duplicate_iterator;
> > +     struct duplicate_item *duplicate;
> > +     struct item *head = {NULL};
> > +     bool need_2_process = true;
> > +     struct item *last = {NULL};
> > +     struct item  *current;
> > +     int verbose_mode = 0;
> > +     uint64_t address;
> > +     FILE *fp;
> > +     int res;
> > +
> > +     if (argc < 2 || argc > 3) {
> > +             printf("Usage: %s <nmfile> [-verbose]\n", argv[0]);
> > +             return 1;
> > +     }
> > +
> > +     if (argc == 3 && strcmp(argv[2], "-verbose") == 0)
> > +             verbose_mode = 1;
> > +
> > +     verbose_msg(verbose_mode, "Scanning nm data(%s)\n", argv[1]);
> > +
> > +     fp = fopen(argv[1], "r");
> > +     if (!fp) {
> > +             printf("Can't open input file.\n");
> > +             return 1;
> > +     }
> > +
> > +     if (!addr2line_init(get_addr2line(A2L_DEFAULT), get_vmlinux(argv[1])))
> > +             return 1;
> > +
> > +     while (fscanf(fp, "%lx %c %99s\n", &address, &t, sym_name) == 3) {
> > +             if (strstr(sym_name, "@_")) {
> > +                     if (verbose_mode && need_2_process)
> > +                             printf("Already processed\n");
> > +                     need_2_process = false;
> > +                     }
> > +             last = add_item(&last, sym_name, t, address);
> > +             if (!last) {
> > +                     printf("Error in allocate memory\n");
> > +                     free_items(&head);
> > +                     return 1;
> > +             }
> > +
> > +             if (!head)
> > +                     head = last;
> > +     }
> > +
> > +     fclose(fp);
> > +
> > +     if (need_2_process) {
> > +             verbose_msg(verbose_mode, "Sorting nm data\n");
> > +             sort_list_m(&head, BY_NAME);
> > +             verbose_msg(verbose_mode, "Scanning nm data for duplicates\n");
> > +             duplicate = find_duplicates(head);
> > +             if (!duplicate) {
> > +                     printf("Error in duplicates list\n");
> > +                     return 1;
> > +             }
> > +
> > +             verbose_msg(verbose_mode, "Applying suffixes\n");
> > +             build_index(head);
> > +             duplicate_iterator = duplicate;
> > +             while (duplicate_iterator) {
> > +                     res = filter_symbols(duplicate_iterator->original_item->symb_name,
> > +                                          ignore_regex, sizeof(ignore_regex) /
> > +                                          sizeof(ignore_regex[0]));
> > +                     if (res != FMATCH &&
> > +                         SYMB_NEEDS_ALIAS(duplicate_iterator->original_item)) {
> > +                             if (res < 0)
> > +                                     return 1;
> > +
> > +                             create_file_suffix(duplicate_iterator->original_item->symb_name,
> > +                                                duplicate_iterator->original_item->addr,
> > +                                                new_name, vmlinux_path);
> > +                             if (!insert_after(head, duplicate_iterator->original_item->addr,
> > +                                               new_name, duplicate_iterator->original_item->addr,
> > +                                               duplicate_iterator->original_item->stype))
> > +                                     return 1;
> > +                     }
> > +
> > +                     duplicate_iterator = duplicate_iterator->next;
> > +             }
> > +
> > +             sort_list_m(&head, BY_ADDRESS);
> > +     }
> > +     current = head;
> > +     while (current) {
> > +             printf("%08lx %c %s\n", current->addr, current->stype, current->symb_name);
> > +             current = current->next;
> > +     }
> > +
> > +     free_items(&head);
> > +     free_duplicates(&duplicate);
> > +     addr2line_cleanup();
> > +     return 0;
> > +}
> > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> > index a432b171be82..cacf60b597ce 100755
> > --- a/scripts/link-vmlinux.sh
> > +++ b/scripts/link-vmlinux.sh
> > @@ -89,8 +89,9 @@ vmlinux_link()
> >
> >       ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
> >
> > -     # The kallsyms linking does not need debug symbols included.
> > -     if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> > +     # The kallsyms linking does not need debug symbols included, unless the KALLSYMS_ALIAS.
> > +     if [ ! is_enabled CONFIG_KALLSYMS_ALIAS ] && \
> > +         [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> >               ldflags="${ldflags} ${wl}--strip-debug"
> >       fi
> >
> > @@ -161,7 +162,11 @@ kallsyms()
> >       fi
> >
> >       info KSYMS ${2}
> > -     scripts/kallsyms ${kallsymopt} ${1} > ${2}
> > +     if is_enabled CONFIG_KALLSYMS_ALIAS; then
> > +             ALIAS=".alias"
> > +             scripts/kas_alias/kas_alias ${1} >${1}${ALIAS}
> > +             fi
>
> Nit: wrong indentation.
> And ALIAS is not defined if CONFIG_KALLSYMS_ALIAS=n.

I rely on the fact that ALIAS is undefined if CONFIG_KALLSYMS_ALIAS=n.
The undefined variable expands to an empty string, and I was constructing
my name using this approach. This method functions in this manner with
all the shells I'm familiar with.
However, I acknowledge that it's more of a hack than a clean programming
practice. In version 4, I will provide a cleaner shell programming
solution.

>
>
> > +     scripts/kallsyms ${kallsymopt} ${1}${ALIAS} > ${2}
> >  }
> >
> >  # Perform one step in kallsyms generation, including temporary linking of
> > --
> > 2.34.1
> >
>
>
> Thank you,
>
> --
> Masami Hiramatsu (Google) <mhiramat@kernel.org>

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-09-01  5:31 ` Masahiro Yamada
@ 2023-09-02  7:27   ` Alessandro Carminati
  0 siblings, 0 replies; 16+ messages in thread
From: Alessandro Carminati @ 2023-09-02  7:27 UTC (permalink / raw)
  To: Masahiro Yamada
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Luis Chamberlain, Nathan Chancellor,
	Nick Desaulniers, Nicolas Schier, Alexander Lobakin, Nick Alcock,
	Kris Van Hees, Eugene Loh, Francis Laniel, Viktor Malik,
	linux-kbuild, linux-kernel, linux-trace-kernel, live-patching

Hello Masahiro,
This review is outstanding. Thanks for the time you used to write me this.


Il giorno ven 1 set 2023 alle ore 07:32 Masahiro Yamada
<masahiroy@kernel.org> ha scritto:
>
> On Mon, Aug 28, 2023 at 8:45 PM Alessandro Carminati (Red Hat)
> <alessandro.carminati@gmail.com> wrote:
> >
> > From: Alessandro Carminati <alessandro.carminati@gmail.com>
> >
> > It is not uncommon for drivers or modules related to similar peripherals
> > to have symbols with the exact same name.
> > While this is not a problem for the kernel's binary itself, it becomes an
> > issue when attempting to trace or probe specific functions using
> > infrastructure like ftrace or kprobe.
> >
> > The tracing subsystem relies on the `nm -n vmlinux` output, which provides
> > symbol information from the kernel's ELF binary. However, when multiple
> > symbols share the same name, the standard nm output does not differentiate
> > between them. This can lead to confusion and difficulty when trying to
> > probe the intended symbol.
> >
> >  ~ # cat /proc/kallsyms | grep " name_show"
> >  ffffffff8c4f76d0 t name_show
> >  ffffffff8c9cccb0 t name_show
> >  ffffffff8cb0ac20 t name_show
> >  ffffffff8cc728c0 t name_show
> >  ffffffff8ce0efd0 t name_show
> >  ffffffff8ce126c0 t name_show
> >  ffffffff8ce1dd20 t name_show
> >  ffffffff8ce24e70 t name_show
> >  ffffffff8d1104c0 t name_show
> >  ffffffff8d1fe480 t name_show
> >
> > **kas_alias** addresses this challenge by extending the symbol names with
> > unique suffixes during the kernel build process.
> > The newly created aliases for these duplicated symbols are unique names
> > that can be fed to the ftracefs interface. By doing so, it enables
> > previously unreachable symbols to be probed.
> >
> >  ~ # cat /proc/kallsyms | grep " name_show"
> >  ffffffff974f76d0 t name_show
> >  ffffffff974f76d0 t name_show__alias__6340
> >  ffffffff979cccb0 t name_show
> >  ffffffff979cccb0 t name_show__alias__6341
> >  ffffffff97b0ac20 t name_show
> >  ffffffff97b0ac20 t name_show__alias__6342
> >  ffffffff97c728c0 t name_show
> >  ffffffff97c728c0 t name_show__alias__6343
> >  ffffffff97e0efd0 t name_show
> >  ffffffff97e0efd0 t name_show__alias__6344
> >  ffffffff97e126c0 t name_show
> >  ffffffff97e126c0 t name_show__alias__6345
> >  ffffffff97e1dd20 t name_show
> >  ffffffff97e1dd20 t name_show__alias__6346
> >  ffffffff97e24e70 t name_show
> >  ffffffff97e24e70 t name_show__alias__6347
> >  ffffffff981104c0 t name_show
> >  ffffffff981104c0 t name_show__alias__6348
> >  ffffffff981fe480 t name_show
> >  ffffffff981fe480 t name_show__alias__6349
> >
> >  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
> >  > >/sys/kernel/tracing/kprobe_events
> >  ~ # cat /sys/kernel/tracing/kprobe_events
> >  p:kprobes/evnt1 name_show__alias__6349
> >
> > Changes from v1:
> > - Integrated changes requested by Masami to exclude symbols with prefixes
> >   "_cfi" and "_pfx".
> > - Introduced a small framework to handle patterns that need to be excluded
> >   from the alias production.
> > - Excluded other symbols using the framework.
> > - Introduced the ability to discriminate between text and data symbols.
> > - Added two new config symbols in this version: CONFIG_KALLSYMS_ALIAS_DATA,
> >   which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
> >   excludes all filters and provides an alias for each duplicated symbol.
> >
> > https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gmail.com/
> >
> > Changes from v2:
> > - Alias tags are created by querying DWARF information from the vmlinux.
> > - The filename + line number is normalized and appended to the original name.
> > - The tag begins with '@' to indicate the symbol source.
> > - Not a change, but worth mentioning, since the alias is added to the existing
> >   list, the old duplicated name is preserved, and the livepatch way of dealing
> >   with duplicates is maintained.
> > - Acknowledging the existence of scenarios where inlined functions declared in
> >   header files may result in multiple copies due to compiler behavior, though
> >    it is not actionable as it does not pose an operational issue.
> > - Highlighting a single exception where the same name refers to different
> >   functions: the case of "compat_binfmt_elf.c," which directly includes
> >   "binfmt_elf.c" producing identical function copies in two separate
> >   modules.
> >
> > sample from new v3
> >
> >  ~ # cat /proc/kallsyms | grep gic_mask_irq
> >  ffffd0b03c04dae4 t gic_mask_irq
> >  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
> >  ffffd0b03c050960 t gic_mask_irq
> >  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
> >  ~ #
> >
> > https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gmail.com/
> >
> > Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> > ---
> >  init/Kconfig                        |  36 ++++
> >  scripts/Makefile                    |   4 +
> >  scripts/kas_alias/Makefile          |   4 +
> >  scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
> >  scripts/kas_alias/a2l.h             |  32 ++++
> >  scripts/kas_alias/duplicates_list.c |  70 ++++++++
> >  scripts/kas_alias/duplicates_list.h |  15 ++
> >  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
> >  scripts/kas_alias/item_list.h       |  26 +++
> >  scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
> >  scripts/link-vmlinux.sh             |  11 +-
> >  11 files changed, 910 insertions(+), 3 deletions(-)
> >  create mode 100644 scripts/kas_alias/Makefile
> >  create mode 100644 scripts/kas_alias/a2l.c
> >  create mode 100644 scripts/kas_alias/a2l.h
> >  create mode 100644 scripts/kas_alias/duplicates_list.c
> >  create mode 100644 scripts/kas_alias/duplicates_list.h
> >  create mode 100644 scripts/kas_alias/item_list.c
> >  create mode 100644 scripts/kas_alias/item_list.h
> >  create mode 100644 scripts/kas_alias/kas_alias.c
> >
> > diff --git a/init/Kconfig b/init/Kconfig
> > index f7f65af4ee12..bc69fcd9cbc8 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -1737,6 +1737,42 @@ config KALLSYMS_BASE_RELATIVE
> >           time constants, and no relocation pass is required at runtime to fix
> >           up the entries based on the runtime load address of the kernel.
> >
> > +config KALLSYMS_ALIAS
> > +       bool "Produces alias for duplicated symbols" if EXPERT
> > +       depends on KALLSYMS && (DEBUG_INFO_DWARF4 || DEBUG_INFO_DWARF5)
>
>
> You can simplify this to
>
>
>            depends on KALLSYMS && DEBUG_INFO
>
> I re-checked the commit log of
> a66049e2cf0ef166dba5bafdbb3062287fc965ad
>
> It says "GCC since ~4.8 has defaulted to DWARF v4
> implicitly, and GCC 11 has bumped this to v5"
>
>
> When DEBUG_INFO is enabled, the dwarf version is 4 or 5.
>
>
> Presumably, your code does not work with DEBUG_INFO_SPLIT
>
>
>    depends on KALLSYMS && DEBUG_INFO && !DEBUG_INFO_SPLIT
>
>
>
>

I will make the necessary updates to v4 based on your analysis.

> > diff --git a/scripts/kas_alias/a2l.c b/scripts/kas_alias/a2l.c
> > new file mode 100644
> > index 000000000000..a9692ac30180
> > --- /dev/null
> > +++ b/scripts/kas_alias/a2l.c
> > @@ -0,0 +1,268 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +#include <sys/types.h>
> > +#include <sys/wait.h>
> > +#include <string.h>
>
>
> <string.h> is included twice.
>
> I always sort include directives alphabetically
> to avoid such a mistake.
>
>
>
>
>
>
> > +#include <stdint.h>
> > +#include <stdbool.h>
> > +
> > +#include "a2l.h"
> > +
> > +int addr2line_pid = -1;
> > +int a2l_in[2];
> > +int a2l_out[2];
> > +char line[MAX_BUF];
> > +char vmlinux_path[MAX_BUF];
> > +char addr2line_cmd[MAX_CMD_LEN];
> > +FILE *a2l_stdin, *a2l_stdout;
> > +
> > +static char *normalize_path(const char *input_path, char *output_path)
> > +{
> > +       char *prev_token = NULL;
> > +       char *delimiter = "/";
> > +       char inbuf[MAX_BUF];
> > +       char *token;
> > +       char *pos;
> > +
> > +       memset(inbuf, 0, MAX_BUF);
> > +       *output_path = '\0';
> > +       strncpy(inbuf, input_path, MAX_BUF);
> > +       if (!input_path || !output_path || strlen(input_path) == 0)
> > +               return NULL;
> > +
> > +       token = strtok(inbuf, delimiter);
> > +       while (token) {
> > +               if (strcmp(token, "..") == 0 && prev_token) {
> > +                       pos = strrchr(output_path, '/');
> > +                       if (pos)
> > +                               *pos = '\0';
> > +
> > +               } else if (strcmp(token, ".") != 0) {
> > +                       strcat(output_path, "/");
> > +                       strcat(output_path, token);
> > +               }
> > +
> > +               prev_token = token;
> > +               token = strtok(NULL, delimiter);
> > +       }
> > +
> > +       return output_path;
> > +}
> > +
> > +static void path_of(const char *full_path, char *path)
> > +{
> > +       const char *last_slash = strrchr(full_path, '/');
> > +       size_t path_length;
> > +       char cwd[MAX_BUF];
> > +
> > +       if (!last_slash) {
> > +               if (getcwd(cwd, sizeof(cwd)))
> > +                       strcpy(path, cwd);
> > +               else
> > +                       strcpy(path, ".");
> > +       } else {
> > +               path_length = last_slash - full_path;
> > +               strncpy(path, full_path, path_length);
> > +               path[path_length] = '\0';
> > +       }
> > +}
> > +
> > +static bool file_exists(const char *file_path)
> > +{
> > +       FILE *file;
> > +
> > +       file = fopen(file_path, "r");
> > +       if (file) {
> > +               fclose(file);
> > +               return true;
> > +       }
> > +       return false;
> > +}
> > +
> > +int addr2line_init(const char *cmd, const char *vmlinux)
> > +{
> > +       if ((!file_exists(cmd)) || (!file_exists(vmlinux))) {
> > +               printf("file not found\n");
> > +               return 0;
> > +               }
> > +
> > +       path_of(vmlinux, vmlinux_path);
> > +       if (pipe(a2l_in) == -1) {
> > +               printf("Failed to create pipe\n");
> > +               return 0;
> > +       }
> > +
> > +       if (pipe(a2l_out) == -1) {
> > +               printf("Failed to create pipe\n");
> > +               return 0;
> > +       }
> > +
> > +       addr2line_pid = fork();
> > +       if (addr2line_pid == -1) {
> > +               printf("Failed to fork process\n");
> > +               close(a2l_in[P_READ]);
> > +               close(a2l_in[P_WRITE]);
> > +               close(a2l_out[P_READ]);
> > +               close(a2l_out[P_WRITE]);
> > +               return 0;
> > +       }
> > +
> > +       if (addr2line_pid == 0) {
> > +               dup2(a2l_in[P_READ], 0);
> > +               dup2(a2l_out[P_WRITE], 1);
> > +               close(a2l_in[P_WRITE]);
> > +               close(a2l_out[P_READ]);
> > +
> > +               execlp(cmd, cmd, ADDR2LINE_ARGS, vmlinux, NULL);
> > +
> > +               printf("Failed to execute addr2line command\n");
> > +               exit(1);
> > +       } else {
> > +               close(a2l_in[P_READ]);
> > +               close(a2l_out[P_WRITE]);
> > +       }
> > +
> > +       a2l_stdin = fdopen(a2l_in[P_WRITE], "w");
> > +       if (!a2l_stdin) {
> > +               printf("Failed to open pipe a2l_in\n");
> > +               return 0;
> > +       }
> > +
> > +       a2l_stdout = fdopen(a2l_out[P_READ], "r");
> > +       if (!a2l_stdout) {
> > +               printf("Failed to open pipe a2l_out\n");
> > +               fclose(a2l_stdin);
> > +               return 0;
> > +       }
> > +
> > +       return 1;
> > +}
> > +
> > +const char *remove_subdir(const char *home, const char *f_path)
> > +{
> > +       int i = 0;
> > +
> > +       while (*(home + i) == *(f_path + i))
> > +               i++;
> > +
> > +       return (strlen(home) != i) ? NULL : f_path + i;
> > +}
> > +
> > +char *addr2line_get_lines(uint64_t address)
> > +{
> > +       char buf[MAX_BUF];
> > +
> > +       fprintf(a2l_stdin, "%08lx\n", address);
> > +       fflush(a2l_stdin);
> > +
> > +       if (!fgets(line, sizeof(line), a2l_stdout)) {
> > +               printf("Failed to read lines from addr2line\n");
> > +               return NULL;
> > +       }
> > +
> > +       if (!fgets(line, sizeof(line), a2l_stdout)) {
> > +               printf("Failed to read lines from addr2line\n");
> > +               return NULL;
> > +       }
> > +
> > +       line[strcspn(line, "\n")] = '\0';
> > +       strncpy(buf, line, MAX_BUF);
> > +       return normalize_path(buf, line);
> > +}
> > +
> > +int addr2line_cleanup(void)
> > +{
> > +       int status;
> > +
> > +       if (addr2line_pid != -1) {
> > +               kill(addr2line_pid, SIGKILL);
> > +               waitpid(addr2line_pid, &status, 0);
> > +               fclose(a2l_stdin);
> > +               fclose(a2l_stdout);
> > +               addr2line_pid = -1;
> > +       }
> > +
> > +       return 1;
> > +}
> > +
> > +static char *find_executable(const char *command)
> > +{
> > +       char *path_env = getenv("PATH");
> > +       char *executable_path;
> > +       char *path_copy;
> > +       char *path;
> > +       int n;
> > +
> > +       if (!path_env)
> > +               return NULL;
> > +
> > +       path_copy = strdup(path_env);
> > +       if (!path_copy)
> > +               return NULL;
> > +
> > +       path = strtok(path_copy, ":");
> > +       while (path) {
> > +               n = snprintf(0, 0, "%s/%s", path, command);
> > +               executable_path = (char *)malloc(n + 1);
> > +               snprintf(executable_path, n + 1, "%s/%s", path, command);
> > +               if (access(executable_path, X_OK) == 0) {
> > +                       free(path_copy);
> > +                       return executable_path;
> > +               }
> > +
> > +       path = strtok(NULL, ":");
> > +       free(executable_path);
> > +       executable_path = NULL;
> > +       }
> > +
> > +       free(path_copy);
> > +       if (executable_path)
> > +               free(executable_path);
> > +       return NULL;
> > +}
> > +
> > +const char *get_addr2line(int mode)
> > +{
> > +       char *buf = "";
> > +
> > +       switch (mode) {
> > +       case A2L_CROSS:
> > +               buf = getenv("CROSS_COMPILE");
> > +               memcpy(addr2line_cmd, buf, strlen(buf));
>
> Dangerous code.
> It is easy to cause a buffer overrun by setting a long string to CROSS_COMPILE.
>
>
> I am fine with adding ADDR2LINE in the top Makefile.
>
>
>
>
>

Understood. In version 4, I will remove all of this and place a new
variable, ADDR2LINE, in the top Makefile.

I'll remove all this in favour of a ne
> > +       case A2L_DEFAULT:
> > +               memcpy(addr2line_cmd + strlen(buf), ADDR2LINE, strlen(ADDR2LINE));
> > +               buf = find_executable(addr2line_cmd);
> > +               if (buf) {
> > +                       memcpy(addr2line_cmd, buf, strlen(buf));
> > +                       free(buf);
> > +               }
> > +               return addr2line_cmd;
> > +       case A2L_LLVM:
> > +       default:
> > +               return NULL;
> > +       }
> > +}
> > +
> > +char *get_vmlinux(char *input)
> > +{
> > +       const char *match_string1 = ".syms";
> > +       const char *match_string2 = ".tmp_vmlinux.kallsyms";
> > +       char *result = NULL;
> > +       char *match_pos;
> > +
> > +       match_pos = strstr(input, match_string1);
> > +       if (!match_pos)
> > +               return NULL;
> > +
> > +       match_pos = strstr(input, match_string2);
> > +       if (!match_pos)
> > +               return NULL;
> > +
> > +       result = strdup(input);
> > +       match_pos = strstr(result, match_string1);
> > +       *match_pos = '\0';
> > +       return result;
> > +}
>
> Tedious code to compute the vmlinux name.
> You can pass vmlinux from command line.
>
>
>
>
> > diff --git a/scripts/kas_alias/item_list.c b/scripts/kas_alias/item_list.c
> > new file mode 100644
> > index 000000000000..48f2e525592a
> > --- /dev/null
> > +++ b/scripts/kas_alias/item_list.c
> > @@ -0,0 +1,230 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <stdint.h>
> > +#include <string.h>
> > +#include <stdbool.h>
> > +#include <assert.h>
> > +#include "item_list.h"
> > +
> > +#define CHECK_ORDER_BY_ADDRESS(sort_by, current, temp, op) \
> > +       ((sort_by) == BY_ADDRESS && (current)->addr op (temp)->addr)
> > +#define CHECK_ORDER_BY_NAME(sort_by, current, temp, op) \
> > +       ((sort_by) == BY_NAME && strcmp((current)->symb_name, (temp)->symb_name) op 0)
> > +
> > +struct item *list_index[96] = {0};
> > +
> > +void build_index(struct item *list)
> > +{
> > +       char current_first_letter = ' ';
> > +       struct item *current = list;
> > +
> > +       while (current) {
> > +               if (current->symb_name[0] != current_first_letter) {
> > +                       current_first_letter = current->symb_name[0];
> > +                       list_index[current_first_letter - 32] = current;
> > +               }
> > +               current = current->next;
> > +       }
> > +}
> > +
> > +struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr)
> > +{
> > +       struct item *new_item;
> > +       struct item *current;
> > +
> > +       new_item = malloc(sizeof(struct item));
> > +       if (!new_item)
> > +               return NULL;
> > +
> > +       strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> > +       new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> > +       new_item->addr = addr;
> > +       new_item->stype = stype;
> > +       new_item->next = NULL;
> > +
> > +       if (!(*list)) {
> > +               *list = new_item;
> > +       } else {
> > +               current = *list;
> > +               while (current->next)
> > +                       current = current->next;
>
>
> What is the purpose of the ->next traverse in while() loop?
>
> If you remember the last item,
> you know where the new item should be connected, don't you?
>
>
>
>
>

Yes, I can keep the last item I added and avoid the seek.
I will make this on the v4.

> > +struct item *merge(struct item *left, struct item *right, int sort_by)
> > +{
> > +       struct item *current = NULL;
> > +       struct item *result = NULL;
> > +
> > +       if (!left)
> > +               return right;
> > +       if (!right)
> > +               return left;
> > +
> > +       if (sort_by == BY_NAME) {
> > +               if (strcmp(left->symb_name, right->symb_name) <= 0) {
> > +                       result = left;
> > +                       left = left->next;
> > +               } else {
> > +                       result = right;
> > +                       right = right->next;
> > +               }
> > +       } else {
> > +               if (sort_by == BY_ADDRESS) {
> > +                       if (left->addr <= right->addr) {
> > +                               result = left;
> > +                               left = left->next;
> > +                       } else {
> > +                               result = right;
> > +                               right = right->next;
> > +                       }
> > +               }
> > +       }
> > +
> > +       current = result;
> > +
> > +       while (left && right) {
> > +               if (sort_by == BY_NAME) {
> > +                       if (strcmp(left->symb_name, right->symb_name) <= 0) {
> > +                               current->next = left;
> > +                               left = left->next;
> > +                       } else {
> > +                               current->next = right;
> > +                               right = right->next;
> > +                       }
> > +               } else {
> > +                       if (sort_by == BY_ADDRESS) {
> > +                               if (left->addr <= right->addr) {
> > +                                       current->next = left;
> > +                                       left = left->next;
> > +                               } else {
> > +                                       current->next = right;
> > +                                       right = right->next;
> > +                               }
> > +                       }
> > +               }
> > +
> > +               current = current->next;
> > +       }
> > +
> > +       if (left) {
> > +               current->next = left;
> > +       } else {
> > +               if (right)
> > +                       current->next = right;
> > +       }
> > +
> > +       return result;
> > +}
> > +
> > +struct item *merge_sort(struct item *head, int sort_by)
>
>
>
> Any reason why you did not use qsort() in the C library?
>
>
> One disadvantage of quick sort is that it is not "stable sort".
>
> But, your algorithm (sort by name and sort by address)
> does not keep the order anyway.
>
>
>
>
> > diff --git a/scripts/kas_alias/item_list.h b/scripts/kas_alias/item_list.h
> > new file mode 100644
> > index 000000000000..b4891cb088ee
> > --- /dev/null
> > +++ b/scripts/kas_alias/item_list.h
> > @@ -0,0 +1,26 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +#ifndef ITEM_LIST_H
> > +#define ITEM_LIST_H
> > +#include <stdint.h>
> > +
> > +#define MAX_NAME_SIZE 256
> > +#define BY_ADDRESS 1
> > +#define BY_NAME 2
> > +
> > +struct item {
> > +       char            symb_name[MAX_NAME_SIZE];
> > +       uint64_t        addr;
> > +       char            stype;
> > +       struct item     *next;
> > +};
> > +
> > +void build_index(struct item *list);
> > +struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr);
> > +void sort_list(struct item **list, int sort_by);
> > +struct item *merge(struct item *left, struct item *right, int sort_by);
> > +struct item *merge_sort(struct item *head, int sort_by);
> > +void sort_list_m(struct item **head, int sort_by);
> > +int insert_after(struct item *list, const uint64_t search_addr,
> > +                const char *name, uint64_t addr, char stype);
> > +void free_items(struct item **head);
> > +#endif
> > diff --git a/scripts/kas_alias/kas_alias.c b/scripts/kas_alias/kas_alias.c
> > new file mode 100644
> > index 000000000000..532aeb39f851
> > --- /dev/null
> > +++ b/scripts/kas_alias/kas_alias.c
> > @@ -0,0 +1,217 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <stdint.h>
> > +#include <unistd.h>
> > +#include <string.h>
> > +#include <stdbool.h>
> > +#include <stdarg.h>
> > +#include <regex.h>
> > +
> > +#include "item_list.h"
> > +#include "duplicates_list.h"
> > +#include "a2l.h"
> > +
> > +#define SYMB_IS_TEXT(s) ((((s)->stype) == 't') ||  (((s)->stype) == 'T'))
> > +#define SYMB_IS_DATA(s) ((((s)->stype) == 'b') ||  (((s)->stype) == 'B') || \
> > +                        (((s)->stype) == 'd') ||  (((s)->stype) == 'D') || \
> > +                        (((s)->stype) == 'r') ||  (((s)->stype) == 'R'))
> > +#ifdef CONFIG_KALLSYMS_ALIAS_DATA
>
>
>
> Please do not use #ifdef CONFIG_ in host programs.
>
> Also, please note include/linux/kconfig.h is not included
> for host programs, so this #ifdef is always false.
>
> You never tested this CONFIG_KALLSYMS_ALIAS_DATA
>
>
>
>
>
>
>

I initiated a conversation with Masami to inquire about the practical
utility of these two items. I personally find them useful, but it's
possible they may not serve a significant purpose.
Therefore, before proceeding with any modifications, I'd like to
receive feedback regarding their usefulness.

In essence, these two configuration items enable the creation of unique
variable names. Since I couldn't identify any other method to ensure
their uniqueness except by adding the "__alias__<seqnum>" as seen in my
v1 patch, it's important to note that the resulting names may be less
meaningful than those for function names.

> > +#define SYMB_NEEDS_ALIAS(s) (SYMB_IS_TEXT(s) || SYMB_IS_DATA(s))
> > +#else
> > +#define SYMB_NEEDS_ALIAS(s) SYMB_IS_TEXT(s)
> > +#endif
> > +#define FNOMATCH 0
> > +#define FMATCH 1
> > +#define EREGEX 2
> > +
> > +const char *ignore_regex[] = {
> > +       "^__cfi_.*$",                           // __cfi_ preamble
> > +#ifndef CONFIG_KALLSYMS_ALIAS_DATA_ALL
> > +       "^_*TRACE_SYSTEM.*$",
> > +       "^__already_done\\.[0-9]+$",            // Call a function once data
> > +       "^___tp_str\\.[0-9]+$",
> > +       "^___done\\.[0-9]+$",
> > +       "^__print_once\\.[0-9]+$",
> > +       "^_rs\\.[0-9]+$",
> > +       "^__compound_literal\\.[0-9]+$",
> > +       "^___once_key\\.[0-9]+$",
> > +       "^__func__\\.[0-9]+$",
> > +       "^__msg\\.[0-9]+$",
> > +       "^CSWTCH\\.[0-9]+$",
> > +       "^__flags\\.[0-9]+$",
> > +       "^__wkey.*$",
> > +       "^__mkey.*$",
> > +       "^__key.*$",
> > +#endif
> > +       "^__pfx_.*$"                            // NOP-padding
> > +};
> > +
> > +int suffix_serial;
> > +
> > +static inline void verbose_msg(bool verbose, const char *fmt, ...)
>
> Meaningless 'inline'.  Only 'static' is enough.
>
>
> > +{
> > +       va_list args;
> > +
> > +       va_start(args, fmt);
> > +       if (verbose)
> > +               printf(fmt, args);
>
>
>
> You cannot pass va_list to printf().
>
> The correct code is:
>
>           vprintf(fmt, args);
>
>
>
>
>
>
>
>
> > +
> > +       va_end(args);
> > +}
>
>
> verbose_msg() prints the message to stdout.
>
> If verbose_msge is enabled, the output file breaks
> because you redirect both real data and debug messages
> in this way:
>    scripts/kas_alias/kas_alias <input>   > <output>
>
>
> If you implement debug logging, I recommend this:
>
>    scripts/kas_alias/kas_alias <input> <output>
>
>
>
>
>
> > +
> > +static void create_suffix(const char *name, char *output_suffix)
> > +{
> > +       sprintf(output_suffix, "%s__alias__%d", name, suffix_serial++);
> > +}
> > +
> > +static void create_file_suffix(const char *name, uint64_t address, char *output_suffix, char *cwd)
> > +{
> > +       const char *f_path;
> > +       char *buf;
> > +       int i = 0;
> > +
> > +       buf = addr2line_get_lines(address);
> > +       f_path = remove_subdir(cwd, buf);
> > +       if (f_path) {
> > +               sprintf(output_suffix, "%s@%s", name, f_path);
> > +               while (*(output_suffix + i) != '\0') {
> > +                       switch (*(output_suffix + i)) {
> > +                       case '/':
> > +                       case ':':
> > +                       case '.':
> > +                               *(output_suffix + i) = '_';
> > +                               break;
> > +                       default:
> > +                       }
> > +               i++;
> > +               }
> > +       } else {
> > +               create_suffix(name, output_suffix);
> > +       }
> > +}
> > +
> > +static int filter_symbols(char *symbol, const char **ignore_list, int regex_no)
> > +{
> > +       regex_t regex;
> > +       int res, i;
> > +
> > +       for (i = 0; i < regex_no; i++) {
> > +               res = regcomp(&regex, ignore_list[i], REG_EXTENDED);
> > +               if (res)
> > +                       return -EREGEX;
> > +
> > +               res = regexec(&regex, symbol, 0, NULL, 0);
> > +               regfree(&regex);
> > +               switch (res) {
> > +               case 0:
> > +                       return FMATCH;
> > +               case REG_NOMATCH:
> > +                       break;
> > +               default:
> > +                       return -EREGEX;
> > +               }
> > +       }
> > +
> > +       return FNOMATCH;
> > +}
> > +
> > +int main(int argc, char *argv[])
> > +{
> > +       char t, sym_name[MAX_NAME_SIZE], new_name[MAX_NAME_SIZE + 15];
> > +       struct duplicate_item  *duplicate_iterator;
> > +       struct duplicate_item *duplicate;
> > +       struct item *head = {NULL};
>
>
>
> This might be something new I should learn.
>
> When I initialize a pointer, I always write like this:
>         struct item *head = NULL;
>
>
> I have never seen this style before:
>         struct item *head = {NULL};
>
> But, the compiler does not warn about it.
> Could you educate me how it works?
>
>
>
>
>

You might be giving me too much credit, or perhaps I didn't catch onto
your humor.

To clarify, what you're witnessing is an error that arose during the
debugging process. During my debugging phase, I had a habit of
initializing variables. However, when it came time to reset them to
NULL, I inadvertently made the wrong adjustment.

From a compiler's perspective, these mistakes yield the same outcome
and no error as setting the pointer to NULL, which is why the error
went unnoticed.

Moving forward, I plan to be more attentive to ensure I produce
higher-quality code for my upcoming contributions.


> > +       bool need_2_process = true;
> > +       struct item *last = {NULL};
> > +       struct item  *current;
> > +       int verbose_mode = 0;
> > +       uint64_t address;
> > +       FILE *fp;
> > +       int res;
> > +
> > +       if (argc < 2 || argc > 3) {
> > +               printf("Usage: %s <nmfile> [-verbose]\n", argv[0]);
> > +               return 1;
> > +       }
> > +
> > +       if (argc == 3 && strcmp(argv[2], "-verbose") == 0)
>
>
> "-v" or "--verbose" is better
> (although there is no way to enable it.)
>
>
> Anyway, I only see super-boring messages
> even with -verbose given.
>
> Scanning nm data()
> Sorting nm data
> Scanning nm data for duplicates
> Applying suffixes
>
>
>
> > +               verbose_mode = 1;
> > +
> > +       verbose_msg(verbose_mode, "Scanning nm data(%s)\n", argv[1]);
> > +
> > +       fp = fopen(argv[1], "r");
> > +       if (!fp) {
> > +               printf("Can't open input file.\n");
> > +               return 1;
> > +       }
> > +
> > +       if (!addr2line_init(get_addr2line(A2L_DEFAULT), get_vmlinux(argv[1])))
> > +               return 1;
> > +
> > +       while (fscanf(fp, "%lx %c %99s\n", &address, &t, sym_name) == 3) {
> > +               if (strstr(sym_name, "@_")) {
> > +                       if (verbose_mode && need_2_process)
> > +                               printf("Already processed\n");
> > +                       need_2_process = false;
> > +                       }
> > +               last = add_item(&last, sym_name, t, address);
> > +               if (!last) {
> > +                       printf("Error in allocate memory\n");
> > +                       free_items(&head);
> > +                       return 1;
> > +               }
> > +
> > +               if (!head)
> > +                       head = last;
> > +       }
> > +
> > +       fclose(fp);
> > +
> > +       if (need_2_process) {
> > +               verbose_msg(verbose_mode, "Sorting nm data\n");
> > +               sort_list_m(&head, BY_NAME);
> > +               verbose_msg(verbose_mode, "Scanning nm data for duplicates\n");
> > +               duplicate = find_duplicates(head);
> > +               if (!duplicate) {
> > +                       printf("Error in duplicates list\n");
> > +                       return 1;
> > +               }
> > +
> > +               verbose_msg(verbose_mode, "Applying suffixes\n");
> > +               build_index(head);
> > +               duplicate_iterator = duplicate;
> > +               while (duplicate_iterator) {
> > +                       res = filter_symbols(duplicate_iterator->original_item->symb_name,
> > +                                            ignore_regex, sizeof(ignore_regex) /
> > +                                            sizeof(ignore_regex[0]));
> > +                       if (res != FMATCH &&
> > +                           SYMB_NEEDS_ALIAS(duplicate_iterator->original_item)) {
> > +                               if (res < 0)
> > +                                       return 1;
> > +
> > +                               create_file_suffix(duplicate_iterator->original_item->symb_name,
> > +                                                  duplicate_iterator->original_item->addr,
> > +                                                  new_name, vmlinux_path);
> > +                               if (!insert_after(head, duplicate_iterator->original_item->addr,
> > +                                                 new_name, duplicate_iterator->original_item->addr,
> > +                                                 duplicate_iterator->original_item->stype))
> > +                                       return 1;
> > +                       }
> > +
> > +                       duplicate_iterator = duplicate_iterator->next;
> > +               }
> > +
> > +               sort_list_m(&head, BY_ADDRESS);
>
>
>
> Do you sort just for finding duplicates?
>
>
> Since you sort the list by name, and then sort by address.
>
> It can potentially change the order.
>
>
> [input]
> 00000000 D foo
> 00000000 D bar
> 00000010 D baz
>
> [merge sort by name]
> 00000000 D bar
> 00000010 D baz
> 00000000 D foo
>
> [merge sort by address = final result]
> 00000000 D bar
> 00000000 D foo
> 00000010 D baz
>
>
> It may not be a big deal, but such a destructive algorithm is frowned.
>
>
>
> You do not need to sort the list to find duplicates.
>
>
> Another choice is a hashtable of { name : count }.
> Traversing the list, you can count the number of occurrences.
> If count >= 2, it is duplicated.
>
> The average look-up of a hashtable is O(1).
> So, the hashtable (or set) algorithm is O(N).
>
>
> Sorting is O(N log N).
>
>
>
>
>
> > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> > index a432b171be82..cacf60b597ce 100755
> > --- a/scripts/link-vmlinux.sh
> > +++ b/scripts/link-vmlinux.sh
> > @@ -89,8 +89,9 @@ vmlinux_link()
> >
> >         ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
> >
> > -       # The kallsyms linking does not need debug symbols included.
> > -       if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> > +       # The kallsyms linking does not need debug symbols included, unless the KALLSYMS_ALIAS.
> > +       if [ ! is_enabled CONFIG_KALLSYMS_ALIAS ] && \
>
>
> I observed this error message:
>
>
> scripts/link-vmlinux.sh: 93: [: is_enabled: unexpected operator
>
>
> The correct code is this:
>
>
>         if ! is_enabled CONFIG_KALLSYMS_ALIAS && \
>
>
>
>
>
>
>
>
>
>
> > +           [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> >                 ldflags="${ldflags} ${wl}--strip-debug"
> >         fi
> >
> > @@ -161,7 +162,11 @@ kallsyms()
> >         fi
> >
> >         info KSYMS ${2}
> > -       scripts/kallsyms ${kallsymopt} ${1} > ${2}
> > +       if is_enabled CONFIG_KALLSYMS_ALIAS; then
> > +               ALIAS=".alias"
> > +               scripts/kas_alias/kas_alias ${1} >${1}${ALIAS}
> > +               fi
> > +       scripts/kallsyms ${kallsymopt} ${1}${ALIAS} > ${2}
> >  }
> >
> >  # Perform one step in kallsyms generation, including temporary linking of
> > --
> > 2.34.1
> >
>
>
> --
> Best Regards
>
>
>
> Masahiro Yamada

thank you

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-09-02  6:36 ` Masahiro Yamada
@ 2023-09-02  7:40   ` Alessandro Carminati
  2023-09-04 13:09     ` Francis Laniel
  2023-09-06 10:09   ` Alessandro Carminati
  1 sibling, 1 reply; 16+ messages in thread
From: Alessandro Carminati @ 2023-09-02  7:40 UTC (permalink / raw)
  To: Masahiro Yamada
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Luis Chamberlain, Nathan Chancellor,
	Nick Desaulniers, Nicolas Schier, Alexander Lobakin, Nick Alcock,
	Kris Van Hees, Eugene Loh, Francis Laniel, Viktor Malik,
	linux-kbuild, linux-kernel, linux-trace-kernel, live-patching

Il giorno sab 2 set 2023 alle ore 08:36 Masahiro Yamada
<masahiroy@kernel.org> ha scritto:
>
> On Mon, Aug 28, 2023 at 8:45 PM Alessandro Carminati (Red Hat)
> <alessandro.carminati@gmail.com> wrote:
> >
> > From: Alessandro Carminati <alessandro.carminati@gmail.com>
> >
> > It is not uncommon for drivers or modules related to similar peripherals
> > to have symbols with the exact same name.
> > While this is not a problem for the kernel's binary itself, it becomes an
> > issue when attempting to trace or probe specific functions using
> > infrastructure like ftrace or kprobe.
> >
> > The tracing subsystem relies on the `nm -n vmlinux` output, which provides
> > symbol information from the kernel's ELF binary. However, when multiple
> > symbols share the same name, the standard nm output does not differentiate
> > between them. This can lead to confusion and difficulty when trying to
> > probe the intended symbol.
> >
> >  ~ # cat /proc/kallsyms | grep " name_show"
> >  ffffffff8c4f76d0 t name_show
> >  ffffffff8c9cccb0 t name_show
> >  ffffffff8cb0ac20 t name_show
> >  ffffffff8cc728c0 t name_show
> >  ffffffff8ce0efd0 t name_show
> >  ffffffff8ce126c0 t name_show
> >  ffffffff8ce1dd20 t name_show
> >  ffffffff8ce24e70 t name_show
> >  ffffffff8d1104c0 t name_show
> >  ffffffff8d1fe480 t name_show
> >
> > **kas_alias** addresses this challenge by extending the symbol names with
> > unique suffixes during the kernel build process.
> > The newly created aliases for these duplicated symbols are unique names
> > that can be fed to the ftracefs interface. By doing so, it enables
> > previously unreachable symbols to be probed.
> >
> >  ~ # cat /proc/kallsyms | grep " name_show"
> >  ffffffff974f76d0 t name_show
> >  ffffffff974f76d0 t name_show__alias__6340
> >  ffffffff979cccb0 t name_show
> >  ffffffff979cccb0 t name_show__alias__6341
> >  ffffffff97b0ac20 t name_show
> >  ffffffff97b0ac20 t name_show__alias__6342
> >  ffffffff97c728c0 t name_show
> >  ffffffff97c728c0 t name_show__alias__6343
> >  ffffffff97e0efd0 t name_show
> >  ffffffff97e0efd0 t name_show__alias__6344
> >  ffffffff97e126c0 t name_show
> >  ffffffff97e126c0 t name_show__alias__6345
> >  ffffffff97e1dd20 t name_show
> >  ffffffff97e1dd20 t name_show__alias__6346
> >  ffffffff97e24e70 t name_show
> >  ffffffff97e24e70 t name_show__alias__6347
> >  ffffffff981104c0 t name_show
> >  ffffffff981104c0 t name_show__alias__6348
> >  ffffffff981fe480 t name_show
> >  ffffffff981fe480 t name_show__alias__6349
> >  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
> >  > >/sys/kernel/tracing/kprobe_events
> >  ~ # cat /sys/kernel/tracing/kprobe_events
> >  p:kprobes/evnt1 name_show__alias__6349
> >
> > Changes from v1:
> > - Integrated changes requested by Masami to exclude symbols with prefixes
> >   "_cfi" and "_pfx".
> > - Introduced a small framework to handle patterns that need to be excluded
> >   from the alias production.
> > - Excluded other symbols using the framework.
> > - Introduced the ability to discriminate between text and data symbols.
> > - Added two new config symbols in this version: CONFIG_KALLSYMS_ALIAS_DATA,
> >   which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
> >   excludes all filters and provides an alias for each duplicated symbol.
> >
> > https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gmail.com/
> >
> > Changes from v2:
> > - Alias tags are created by querying DWARF information from the vmlinux.
> > - The filename + line number is normalized and appended to the original name.
> > - The tag begins with '@' to indicate the symbol source.
> > - Not a change, but worth mentioning, since the alias is added to the existing
> >   list, the old duplicated name is preserved, and the livepatch way of dealing
> >   with duplicates is maintained.
> > - Acknowledging the existence of scenarios where inlined functions declared in
> >   header files may result in multiple copies due to compiler behavior, though
> >    it is not actionable as it does not pose an operational issue.
> > - Highlighting a single exception where the same name refers to different
> >   functions: the case of "compat_binfmt_elf.c," which directly includes
> >   "binfmt_elf.c" producing identical function copies in two separate
> >   modules.
> >
> > sample from new v3
> >
> >  ~ # cat /proc/kallsyms | grep gic_mask_irq
> >  ffffd0b03c04dae4 t gic_mask_irq
> >  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
> >  ffffd0b03c050960 t gic_mask_irq
> >  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
> >  ~ #
> >
> > https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gmail.com/
> >
> > Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> > ---
> >  init/Kconfig                        |  36 ++++
> >  scripts/Makefile                    |   4 +
> >  scripts/kas_alias/Makefile          |   4 +
> >  scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
> >  scripts/kas_alias/a2l.h             |  32 ++++
> >  scripts/kas_alias/duplicates_list.c |  70 ++++++++
> >  scripts/kas_alias/duplicates_list.h |  15 ++
> >  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
> >  scripts/kas_alias/item_list.h       |  26 +++
> >  scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
> >  scripts/link-vmlinux.sh             |  11 +-
> >  11 files changed, 910 insertions(+), 3 deletions(-)
>
>
> I added some review comments in another thread, but
> one of the biggest concerns might be "910 insertions".

Based on the feedback I received in the reviews, I need to overhaul the
code, potentially reducing its size. What would be a reasonable number
of lines for this feature?

>
>
> What this program does is quite simple,
> "find duplicated names, and call addr2line".
>
>
>
> You wrote a lot of code to self-implement these:
>
>  - sort function
>  - parse PATH env variable to find addr2line
>  - fork addr2line to establish pipe communications

Some of these functions might become obsolete in the upcoming v4, which
will certainly reduce the line count.

>
>
>
> Have you considered writing the code in Python (or Perl)?
> Is it too slow?

From my perspective, there is a concern that using Python or Perl might
result in slower performance. My proficiency in Python and Perl is
limited, so I did not initially consider them as viable options for
implementing this solution.

>
> Most of the functions you implemented are already
> available in script languages.
>
>
>
> I am not sure if "@<file-path>" is a good solution,
> but the amount of the added code looks too much to me.
>

I had reservations about using the '@' symbol to decorate the alias because
it's not a character commonly found in the kallsyms output. However, after
careful consideration, I arrived at the conclusion that it was suitable for
the task because it would make the alias stand-out and be easily
identifiable.
I'm open to any suggestions or alternative approaches you may have on this
matter.

>
>
>
> --
> Best Regards
> Masahiro Yamada

Thank you

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-09-02  7:26   ` Alessandro Carminati
@ 2023-09-03 14:50     ` Masami Hiramatsu
  0 siblings, 0 replies; 16+ messages in thread
From: Masami Hiramatsu @ 2023-09-03 14:50 UTC (permalink / raw)
  To: Alessandro Carminati
  Cc: Steven Rostedt, Daniel Bristot de Oliveira, Josh Poimboeuf,
	Masahiro Yamada, Luis Chamberlain, Nathan Chancellor,
	Nick Desaulniers, Nicolas Schier, Alexander Lobakin, Nick Alcock,
	Kris Van Hees, Eugene Loh, Francis Laniel, Viktor Malik,
	linux-kbuild, linux-kernel, linux-trace-kernel, live-patching

On Sat, 2 Sep 2023 09:26:59 +0200
Alessandro Carminati <alessandro.carminati@gmail.com> wrote:

> Hey Masami,
> Thanks a lot for your review and for your time.
> 
> Il giorno mer 30 ago 2023 alle ore 08:00 Masami Hiramatsu
> <mhiramat@kernel.org> ha scritto:
> >
> > Hi Alessandro,
> >
> > Thanks for your update!
> >
> > On Mon, 28 Aug 2023 08:04:23 +0000
> > "Alessandro Carminati (Red Hat)" <alessandro.carminati@gmail.com> wrote:
> >
> > > From: Alessandro Carminati <alessandro.carminati@gmail.com>
> > >
> > > It is not uncommon for drivers or modules related to similar peripherals
> > > to have symbols with the exact same name.
> > > While this is not a problem for the kernel's binary itself, it becomes an
> > > issue when attempting to trace or probe specific functions using
> > > infrastructure like ftrace or kprobe.
> > >
> > > The tracing subsystem relies on the `nm -n vmlinux` output, which provides
> > > symbol information from the kernel's ELF binary. However, when multiple
> > > symbols share the same name, the standard nm output does not differentiate
> > > between them. This can lead to confusion and difficulty when trying to
> > > probe the intended symbol.
> > >
> > >  ~ # cat /proc/kallsyms | grep " name_show"
> > >  ffffffff8c4f76d0 t name_show
> > >  ffffffff8c9cccb0 t name_show
> > >  ffffffff8cb0ac20 t name_show
> > >  ffffffff8cc728c0 t name_show
> > >  ffffffff8ce0efd0 t name_show
> > >  ffffffff8ce126c0 t name_show
> > >  ffffffff8ce1dd20 t name_show
> > >  ffffffff8ce24e70 t name_show
> > >  ffffffff8d1104c0 t name_show
> > >  ffffffff8d1fe480 t name_show
> > >
> > > **kas_alias** addresses this challenge by extending the symbol names with
> > > unique suffixes during the kernel build process.
> > > The newly created aliases for these duplicated symbols are unique names
> > > that can be fed to the ftracefs interface. By doing so, it enables
> > > previously unreachable symbols to be probed.
> > >
> > >  ~ # cat /proc/kallsyms | grep " name_show"
> > >  ffffffff974f76d0 t name_show
> > >  ffffffff974f76d0 t name_show__alias__6340
> > >  ffffffff979cccb0 t name_show
> > >  ffffffff979cccb0 t name_show__alias__6341
> > >  ffffffff97b0ac20 t name_show
> > >  ffffffff97b0ac20 t name_show__alias__6342
> > >  ffffffff97c728c0 t name_show
> > >  ffffffff97c728c0 t name_show__alias__6343
> > >  ffffffff97e0efd0 t name_show
> > >  ffffffff97e0efd0 t name_show__alias__6344
> > >  ffffffff97e126c0 t name_show
> > >  ffffffff97e126c0 t name_show__alias__6345
> > >  ffffffff97e1dd20 t name_show
> > >  ffffffff97e1dd20 t name_show__alias__6346
> > >  ffffffff97e24e70 t name_show
> > >  ffffffff97e24e70 t name_show__alias__6347
> > >  ffffffff981104c0 t name_show
> > >  ffffffff981104c0 t name_show__alias__6348
> > >  ffffffff981fe480 t name_show
> > >  ffffffff981fe480 t name_show__alias__6349
> > >  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
> > >  > >/sys/kernel/tracing/kprobe_events
> > >  ~ # cat /sys/kernel/tracing/kprobe_events
> > >  p:kprobes/evnt1 name_show__alias__6349
> > >
> > > Changes from v1:
> > > - Integrated changes requested by Masami to exclude symbols with prefixes
> > >   "_cfi" and "_pfx".
> > > - Introduced a small framework to handle patterns that need to be excluded
> > >   from the alias production.
> > > - Excluded other symbols using the framework.
> > > - Introduced the ability to discriminate between text and data symbols.
> > > - Added two new config symbols in this version: CONFIG_KALLSYMS_ALIAS_DATA,
> > >   which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
> > >   excludes all filters and provides an alias for each duplicated symbol.
> > >
> > > https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gmail.com/
> > >
> > > Changes from v2:
> > > - Alias tags are created by querying DWARF information from the vmlinux.
> > > - The filename + line number is normalized and appended to the original name.
> > > - The tag begins with '@' to indicate the symbol source.
> > > - Not a change, but worth mentioning, since the alias is added to the existing
> > >   list, the old duplicated name is preserved, and the livepatch way of dealing
> > >   with duplicates is maintained.
> > > - Acknowledging the existence of scenarios where inlined functions declared in
> > >   header files may result in multiple copies due to compiler behavior, though
> > >    it is not actionable as it does not pose an operational issue.
> > > - Highlighting a single exception where the same name refers to different
> > >   functions: the case of "compat_binfmt_elf.c," which directly includes
> > >   "binfmt_elf.c" producing identical function copies in two separate
> > >   modules.
> > >
> > > sample from new v3
> > >
> > >  ~ # cat /proc/kallsyms | grep gic_mask_irq
> > >  ffffd0b03c04dae4 t gic_mask_irq
> > >  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
> > >  ffffd0b03c050960 t gic_mask_irq
> > >  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
> >
> > Could you also update the sample output in the patch description?
> > And I can not see this line information but a serial number aliases,
> > is there any way to enable this file-name aliases? (LLVM is not supported?)
> > I think we'd better to have a new CONFIG_KALLSYMS_ALIAS_SRCLINE and
> > clarify what is required.
> 
> In this version of the patch, there's still a fallback action that
> produces the old "__alias__<seqnum>" if the addr2line action fails.
> In the v3 patch, addr2line is default to the native option.

OK, do you know when the addr2line fails? If it is clear, it is
better to unselect the CONFIG_KALLSYMS_ALIAS_SRCLINE instead of
statically failback to seqnum suffix (or failed to build), because
user expects that the built kernel image is including the alias has
suffixes based on src line number.
This is important especially it depends on user environment, because
it gives user to update their environment before building the kernel.

> The CROSS_COMPILE setting remains a manual selection. While in my tests,
> I didn't encounter any issues, and the native addr2line worked well on
> all the architectures I tested, there is still a possibility of failure
> leading to the fallback action. Somthing I will change in the v4.

Good.

> 
> Additionally, if CONFIG_KALLSYMS_ALIAS_DATA is set to 'Y,' data names
> included in the KALLSYMS receive an old-style alias.
> Regarding this matter, I'd like to discuss with you the relevance of
> CONFIG_KALLSYMS_ALIAS_DATA and CONFIG_KALLSYMS_ALIAS_DATA_ALL.

Would you mean that the symbols of DATA can not use src lines?
(what is the "old-style alias" you meant here?)

> Both of these settings aim to provide an alias for variable names as
> well. In the past, I had to "livepatch" a function for an architecture
> that had no support, and I thought it would be beneficial to have
> unique variable names as well. What are your thoughts on this?

Yeah, it is also good for kprobe-events because it supports probes
to access global variables by name. Thus if the alias can specify a
unique symbol, it ensures which variable we will trace.

> >
> > >  ~ #
> > >
> > > https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gmail.com/
> > >
> > > Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> > > ---
> > >  init/Kconfig                        |  36 ++++
> > >  scripts/Makefile                    |   4 +
> > >  scripts/kas_alias/Makefile          |   4 +
> > >  scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
> > >  scripts/kas_alias/a2l.h             |  32 ++++
> > >  scripts/kas_alias/duplicates_list.c |  70 ++++++++
> > >  scripts/kas_alias/duplicates_list.h |  15 ++
> > >  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
> > >  scripts/kas_alias/item_list.h       |  26 +++
> > >  scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
> > >  scripts/link-vmlinux.sh             |  11 +-
> > >  11 files changed, 910 insertions(+), 3 deletions(-)
> > >  create mode 100644 scripts/kas_alias/Makefile
> > >  create mode 100644 scripts/kas_alias/a2l.c
> > >  create mode 100644 scripts/kas_alias/a2l.h
> > >  create mode 100644 scripts/kas_alias/duplicates_list.c
> > >  create mode 100644 scripts/kas_alias/duplicates_list.h
> > >  create mode 100644 scripts/kas_alias/item_list.c
> > >  create mode 100644 scripts/kas_alias/item_list.h
> > >  create mode 100644 scripts/kas_alias/kas_alias.c
> > >
> > > diff --git a/init/Kconfig b/init/Kconfig
> > > index f7f65af4ee12..bc69fcd9cbc8 100644
> > > --- a/init/Kconfig
> > > +++ b/init/Kconfig
> > > @@ -1737,6 +1737,42 @@ config KALLSYMS_BASE_RELATIVE
> > >         time constants, and no relocation pass is required at runtime to fix
> > >         up the entries based on the runtime load address of the kernel.
> > >
> > > +config KALLSYMS_ALIAS
> > > +     bool "Produces alias for duplicated symbols" if EXPERT
> > > +     depends on KALLSYMS && (DEBUG_INFO_DWARF4 || DEBUG_INFO_DWARF5)
> > > +     help
> > > +       It is not uncommon for drivers or modules related to similar
> > > +       peripherals to have symbols with the exact same name.
> > > +       While this is not a problem for the kernel's binary itself, it
> > > +       becomes an issue when attempting to trace or probe specific
> > > +       functions using infrastructure like ftrace or kprobe.
> > > +
> > > +       This option addresses this challenge by extending the symbol names
> > > +       with unique suffixes during the kernel build process.
> > > +       The newly created aliases for these duplicated symbols are unique
> > > +       names that can be fed to the ftrace sysfs interface. By doing so, it
> > > +       enables previously unreachable symbols to be probed.
> > > +
> > > +config CONFIG_KALLSYMS_ALIAS_DATA
> >
> > You don't need 'CONFIG_' prefix here.
> >
> > > +     bool "Produces alias also for data"
> > > +     depends on KALLSYMS_ALIAS
> > > +     help
> > > +       Sometimes it can be useful to refer to data. In live patch scenarios,
> > > +       you may find yourself needing to use symbols that are shared with
> > > +       other functions. Since symbols face the same issue as functions, this
> > > +       option allows you to create aliases for data as well.
> > > +
> > > +config CONFIG_KALLSYMS_ALIAS_DATA_ALL
> > > +     bool "Removes all filter when producing data alias"
> > > +     depends on CONFIG_KALLSYMS_ALIAS_DATA
> > > +     help
> > > +       When selecting data aliases, not all symbols are included in the set
> > > +       This is because many symbols are unlikely to be used. If you choose
> > > +       to have an alias for all data symbols, be aware that it will
> > > +       significantly increase the size.
> > > +
> > > +       If unsure, say N.
> > > +
> > >  # end of the "standard kernel features (expert users)" menu
> > >
> > >  # syscall, maps, verifier
> > > diff --git a/scripts/Makefile b/scripts/Makefile
> > > index 32b6ba722728..65fafe17cfe5 100644
> > > --- a/scripts/Makefile
> > > +++ b/scripts/Makefile
> > > @@ -49,3 +49,7 @@ subdir-$(CONFIG_SECURITY_SELINUX) += selinux
> > >
> > >  # Let clean descend into subdirs
> > >  subdir-      += basic dtc gdb kconfig mod
> > > +
> > > +# KALLSyms alias
> > > +subdir-$(CONFIG_KALLSYMS_ALIAS) += kas_alias
> > > +
> > > diff --git a/scripts/kas_alias/Makefile b/scripts/kas_alias/Makefile
> > > new file mode 100644
> > > index 000000000000..e1fde69232b4
> > > --- /dev/null
> > > +++ b/scripts/kas_alias/Makefile
> > > @@ -0,0 +1,4 @@
> > > +# SPDX-License-Identifier: GPL-2.0
> > > +hostprogs-always-$(CONFIG_KALLSYMS_ALIAS)    += kas_alias
> > > +
> > > +kas_alias-objs        := duplicates_list.o item_list.o kas_alias.o a2l.o
> > > diff --git a/scripts/kas_alias/a2l.c b/scripts/kas_alias/a2l.c
> > > new file mode 100644
> > > index 000000000000..a9692ac30180
> > > --- /dev/null
> > > +++ b/scripts/kas_alias/a2l.c
> > > @@ -0,0 +1,268 @@
> > > +// SPDX-License-Identifier: GPL-2.0-or-later
> > > +#include <stdio.h>
> > > +#include <stdlib.h>
> > > +#include <string.h>
> > > +#include <unistd.h>
> > > +#include <sys/types.h>
> > > +#include <sys/wait.h>
> > > +#include <string.h>
> > > +#include <stdint.h>
> > > +#include <stdbool.h>
> > > +
> > > +#include "a2l.h"
> > > +
> > > +int addr2line_pid = -1;
> > > +int a2l_in[2];
> > > +int a2l_out[2];
> > > +char line[MAX_BUF];
> > > +char vmlinux_path[MAX_BUF];
> > > +char addr2line_cmd[MAX_CMD_LEN];
> > > +FILE *a2l_stdin, *a2l_stdout;
> > > +
> > > +static char *normalize_path(const char *input_path, char *output_path)
> > > +{
> > > +     char *prev_token = NULL;
> > > +     char *delimiter = "/";
> > > +     char inbuf[MAX_BUF];
> > > +     char *token;
> > > +     char *pos;
> > > +
> > > +     memset(inbuf, 0, MAX_BUF);
> > > +     *output_path = '\0';
> > > +     strncpy(inbuf, input_path, MAX_BUF);
> > > +     if (!input_path || !output_path || strlen(input_path) == 0)
> > > +             return NULL;
> > > +
> > > +     token = strtok(inbuf, delimiter);
> > > +     while (token) {
> > > +             if (strcmp(token, "..") == 0 && prev_token) {
> > > +                     pos = strrchr(output_path, '/');
> > > +                     if (pos)
> > > +                             *pos = '\0';
> > > +
> > > +             } else if (strcmp(token, ".") != 0) {
> > > +                     strcat(output_path, "/");
> > > +                     strcat(output_path, token);
> > > +             }
> > > +
> > > +             prev_token = token;
> > > +             token = strtok(NULL, delimiter);
> > > +     }
> > > +
> > > +     return output_path;
> > > +}
> > > +
> > > +static void path_of(const char *full_path, char *path)
> > > +{
> > > +     const char *last_slash = strrchr(full_path, '/');
> > > +     size_t path_length;
> > > +     char cwd[MAX_BUF];
> > > +
> > > +     if (!last_slash) {
> > > +             if (getcwd(cwd, sizeof(cwd)))
> > > +                     strcpy(path, cwd);
> > > +             else
> > > +                     strcpy(path, ".");
> > > +     } else {
> > > +             path_length = last_slash - full_path;
> > > +             strncpy(path, full_path, path_length);
> > > +             path[path_length] = '\0';
> > > +     }
> > > +}
> > > +
> > > +static bool file_exists(const char *file_path)
> > > +{
> > > +     FILE *file;
> > > +
> > > +     file = fopen(file_path, "r");
> > > +     if (file) {
> > > +             fclose(file);
> > > +             return true;
> > > +     }
> > > +     return false;
> > > +}
> > > +
> > > +int addr2line_init(const char *cmd, const char *vmlinux)
> > > +{
> > > +     if ((!file_exists(cmd)) || (!file_exists(vmlinux))) {
> > > +             printf("file not found\n");
> > > +             return 0;
> > > +             }
> >
> > nit: mis-indentation?
> >
> > > +
> > > +     path_of(vmlinux, vmlinux_path);
> > > +     if (pipe(a2l_in) == -1) {
> > > +             printf("Failed to create pipe\n");
> > > +             return 0;
> > > +     }
> > > +
> > > +     if (pipe(a2l_out) == -1) {
> > > +             printf("Failed to create pipe\n");
> > > +             return 0;
> > > +     }
> > > +
> > > +     addr2line_pid = fork();
> > > +     if (addr2line_pid == -1) {
> > > +             printf("Failed to fork process\n");
> > > +             close(a2l_in[P_READ]);
> > > +             close(a2l_in[P_WRITE]);
> > > +             close(a2l_out[P_READ]);
> > > +             close(a2l_out[P_WRITE]);
> > > +             return 0;
> > > +     }
> > > +
> > > +     if (addr2line_pid == 0) {
> > > +             dup2(a2l_in[P_READ], 0);
> > > +             dup2(a2l_out[P_WRITE], 1);
> > > +             close(a2l_in[P_WRITE]);
> > > +             close(a2l_out[P_READ]);
> > > +
> > > +             execlp(cmd, cmd, ADDR2LINE_ARGS, vmlinux, NULL);
> > > +
> > > +             printf("Failed to execute addr2line command\n");
> > > +             exit(1);
> > > +     } else {
> > > +             close(a2l_in[P_READ]);
> > > +             close(a2l_out[P_WRITE]);
> > > +     }
> > > +
> > > +     a2l_stdin = fdopen(a2l_in[P_WRITE], "w");
> > > +     if (!a2l_stdin) {
> > > +             printf("Failed to open pipe a2l_in\n");
> > > +             return 0;
> > > +     }
> > > +
> > > +     a2l_stdout = fdopen(a2l_out[P_READ], "r");
> > > +     if (!a2l_stdout) {
> > > +             printf("Failed to open pipe a2l_out\n");
> > > +             fclose(a2l_stdin);
> > > +             return 0;
> > > +     }
> > > +
> > > +     return 1;
> > > +}
> > > +
> > > +const char *remove_subdir(const char *home, const char *f_path)
> > > +{
> > > +     int i = 0;
> > > +
> > > +     while (*(home + i) == *(f_path + i))
> > > +             i++;
> > > +
> > > +     return (strlen(home) != i) ? NULL : f_path + i;
> > > +}
> > > +
> > > +char *addr2line_get_lines(uint64_t address)
> > > +{
> > > +     char buf[MAX_BUF];
> > > +
> > > +     fprintf(a2l_stdin, "%08lx\n", address);
> > > +     fflush(a2l_stdin);
> > > +
> > > +     if (!fgets(line, sizeof(line), a2l_stdout)) {
> > > +             printf("Failed to read lines from addr2line\n");
> > > +             return NULL;
> > > +     }
> > > +
> > > +     if (!fgets(line, sizeof(line), a2l_stdout)) {
> > > +             printf("Failed to read lines from addr2line\n");
> > > +             return NULL;
> > > +     }
> > > +
> > > +     line[strcspn(line, "\n")] = '\0';
> > > +     strncpy(buf, line, MAX_BUF);
> > > +     return normalize_path(buf, line);
> > > +}
> > > +
> > > +int addr2line_cleanup(void)
> > > +{
> > > +     int status;
> > > +
> > > +     if (addr2line_pid != -1) {
> > > +             kill(addr2line_pid, SIGKILL);
> > > +             waitpid(addr2line_pid, &status, 0);
> > > +             fclose(a2l_stdin);
> > > +             fclose(a2l_stdout);
> > > +             addr2line_pid = -1;
> > > +     }
> > > +
> > > +     return 1;
> > > +}
> > > +
> > > +static char *find_executable(const char *command)
> > > +{
> > > +     char *path_env = getenv("PATH");
> > > +     char *executable_path;
> > > +     char *path_copy;
> > > +     char *path;
> > > +     int n;
> > > +
> > > +     if (!path_env)
> > > +             return NULL;
> > > +
> > > +     path_copy = strdup(path_env);
> > > +     if (!path_copy)
> > > +             return NULL;
> > > +
> > > +     path = strtok(path_copy, ":");
> > > +     while (path) {
> > > +             n = snprintf(0, 0, "%s/%s", path, command);
> > > +             executable_path = (char *)malloc(n + 1);
> > > +             snprintf(executable_path, n + 1, "%s/%s", path, command);
> > > +             if (access(executable_path, X_OK) == 0) {
> > > +                     free(path_copy);
> > > +                     return executable_path;
> > > +             }
> > > +
> > > +     path = strtok(NULL, ":");
> > > +     free(executable_path);
> > > +     executable_path = NULL;
> >
> > nit: mis-indentation?
> >
> > > +     }
> > > +
> > > +     free(path_copy);
> > > +     if (executable_path)
> > > +             free(executable_path);
> > > +     return NULL;
> > > +}
> > > +
> > > +const char *get_addr2line(int mode)
> > > +{
> > > +     char *buf = "";
> > > +
> > > +     switch (mode) {
> > > +     case A2L_CROSS:
> > > +             buf = getenv("CROSS_COMPILE");
> > > +             memcpy(addr2line_cmd, buf, strlen(buf));
> > > +     case A2L_DEFAULT:
> > > +             memcpy(addr2line_cmd + strlen(buf), ADDR2LINE, strlen(ADDR2LINE));
> > > +             buf = find_executable(addr2line_cmd);
> > > +             if (buf) {
> > > +                     memcpy(addr2line_cmd, buf, strlen(buf));
> > > +                     free(buf);
> > > +             }
> > > +             return addr2line_cmd;
> > > +     case A2L_LLVM:
> > > +     default:
> > > +             return NULL;
> > > +     }
> > > +}
> > > +
> > > +char *get_vmlinux(char *input)
> > > +{
> > > +     const char *match_string1 = ".syms";
> > > +     const char *match_string2 = ".tmp_vmlinux.kallsyms";
> > > +     char *result = NULL;
> > > +     char *match_pos;
> > > +
> > > +     match_pos = strstr(input, match_string1);
> > > +     if (!match_pos)
> > > +             return NULL;
> > > +
> > > +     match_pos = strstr(input, match_string2);
> > > +     if (!match_pos)
> > > +             return NULL;
> > > +
> > > +     result = strdup(input);
> > > +     match_pos = strstr(result, match_string1);
> > > +     *match_pos = '\0';
> > > +     return result;
> > > +}
> > > diff --git a/scripts/kas_alias/a2l.h b/scripts/kas_alias/a2l.h
> > > new file mode 100644
> > > index 000000000000..ca6419229dde
> > > --- /dev/null
> > > +++ b/scripts/kas_alias/a2l.h
> > > @@ -0,0 +1,32 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > > +#ifndef A2L_H
> > > +#define A2L_H
> > > +#include <stdint.h>
> > > +
> > > +#define ADDR2LINE "addr2line"
> > > +#define ADDR2LINE_ARGS "-fe"
> > > +//#define VMLINUX "vmlinux"
> >
> > Nit: this should be removed if it is not used.
> >
> > > +#define MAX_BUF 4096
> > > +#define MAX_CMD_LEN 256
> > > +#define P_READ 0
> > > +#define P_WRITE 1
> > > +#define A2L_DEFAULT 1
> > > +#define A2L_CROSS 2
> > > +#define A2L_LLVM 3
> > > +#define A2L_MAKE_VALUE 2
> > > +
> > > +extern int addr2line_pid;
> > > +extern int a2l_in[2];
> > > +extern int a2l_out[2];
> > > +extern char line[MAX_BUF];
> > > +extern char vmlinux_path[MAX_BUF];
> > > +extern char addr2line_cmd[MAX_CMD_LEN];
> > > +
> > > +int addr2line_init(const char *cmd, const char *vmlinux);
> > > +char *addr2line_get_lines(uint64_t address);
> > > +int addr2line_cleanup(void);
> > > +const char *remove_subdir(const char *home, const char *f_path);
> > > +const char *get_addr2line(int mode);
> > > +char *get_vmlinux(char *input);
> > > +
> > > +#endif
> > > diff --git a/scripts/kas_alias/duplicates_list.c b/scripts/kas_alias/duplicates_list.c
> > > new file mode 100644
> > > index 000000000000..e7a3d2917937
> > > --- /dev/null
> > > +++ b/scripts/kas_alias/duplicates_list.c
> > > @@ -0,0 +1,70 @@
> > > +// SPDX-License-Identifier: GPL-2.0-or-later
> > > +#include <stdint.h>
> > > +#include <stdio.h>
> > > +#include <string.h>
> > > +#include <stdlib.h>
> > > +#include <stdbool.h>
> > > +
> > > +#include "item_list.h"
> > > +#include "duplicates_list.h"
> > > +
> >
> > /* The item list must be sorted. */
> >
> > I think we can find the duplicated symbol without sorting the list,
> > but such implementation level optimization will be done later.
> 
> I think I will handle this aspect in the v4.

Good :)

> 
> >
> > > +struct duplicate_item *find_duplicates(struct item *list)
> > > +{
> > > +     struct duplicate_item *current_duplicate = NULL;
> > > +     struct duplicate_item *duplicates = NULL;
> > > +     struct duplicate_item *new_duplicate;
> > > +     struct item *current_item = list;
> > > +     bool prev_was_duplicate = false;
> > > +     struct item *prev_item = NULL;
> > > +
> > > +     while (current_item) {
> > > +             if ((prev_item && (strcmp(current_item->symb_name, prev_item->symb_name) == 0)) ||
> > > +                 prev_was_duplicate) {
> > > +                     if (!duplicates) {
> > > +                             duplicates = malloc(sizeof(struct duplicate_item));
> > > +                             if (!duplicates)
> > > +                                     return NULL;
> > > +
> > > +                             duplicates->original_item = prev_item;
> > > +                             duplicates->next = NULL;
> > > +                             current_duplicate = duplicates;
> > > +                     } else {
> > > +                             new_duplicate = malloc(sizeof(struct duplicate_item));
> > > +                             if (!new_duplicate) {
> > > +                                     free_duplicates(&duplicates);
> > > +                                     return NULL;
> > > +                             }
> > > +
> > > +                             new_duplicate->original_item = prev_item;
> > > +                             new_duplicate->next = NULL;
> > > +                             current_duplicate->next = new_duplicate;
> > > +                             current_duplicate = new_duplicate;
> > > +
> > > +                             if ((strcmp(current_item->symb_name, prev_item->symb_name) != 0) &&
> > > +                                 (prev_was_duplicate))
> > > +                                     prev_was_duplicate = false;
> > > +                             else
> > > +                                     prev_was_duplicate = true;
> > > +                     }
> > > +             }
> > > +
> > > +             prev_item = current_item;
> > > +             current_item = current_item->next;
> > > +     }
> > > +
> > > +     return duplicates;
> > > +}
> > > +
> > > +void free_duplicates(struct duplicate_item **duplicates)
> > > +{
> > > +     struct duplicate_item *duplicates_iterator = *duplicates;
> > > +     struct duplicate_item *app;
> > > +
> > > +     while (duplicates_iterator) {
> > > +             app = duplicates_iterator;
> > > +             duplicates_iterator = duplicates_iterator->next;
> > > +             free(app);
> > > +     }
> > > +
> > > +     *duplicates = NULL;
> > > +}
> > > diff --git a/scripts/kas_alias/duplicates_list.h b/scripts/kas_alias/duplicates_list.h
> > > new file mode 100644
> > > index 000000000000..76aa73e584bc
> > > --- /dev/null
> > > +++ b/scripts/kas_alias/duplicates_list.h
> > > @@ -0,0 +1,15 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > > +#ifndef DUPLICATES_LIST_H
> > > +#define DUPLICATES_LIST_H
> > > +
> > > +#include "item_list.h"
> > > +
> > > +struct duplicate_item {
> > > +     struct item *original_item;
> > > +     struct duplicate_item *next;
> > > +};
> > > +
> > > +struct duplicate_item *find_duplicates(struct item *list);
> > > +void free_duplicates(struct duplicate_item **duplicates);
> > > +
> > > +#endif
> > > diff --git a/scripts/kas_alias/item_list.c b/scripts/kas_alias/item_list.c
> > > new file mode 100644
> > > index 000000000000..48f2e525592a
> > > --- /dev/null
> > > +++ b/scripts/kas_alias/item_list.c
> > > @@ -0,0 +1,230 @@
> > > +// SPDX-License-Identifier: GPL-2.0-or-later
> > > +#include <stdio.h>
> > > +#include <stdlib.h>
> > > +#include <stdint.h>
> > > +#include <string.h>
> > > +#include <stdbool.h>
> > > +#include <assert.h>
> > > +#include "item_list.h"
> > > +
> > > +#define CHECK_ORDER_BY_ADDRESS(sort_by, current, temp, op) \
> > > +     ((sort_by) == BY_ADDRESS && (current)->addr op (temp)->addr)
> > > +#define CHECK_ORDER_BY_NAME(sort_by, current, temp, op) \
> > > +     ((sort_by) == BY_NAME && strcmp((current)->symb_name, (temp)->symb_name) op 0)
> > > +
> > > +struct item *list_index[96] = {0};
> > > +
> > > +void build_index(struct item *list)
> > > +{
> > > +     char current_first_letter = ' ';
> > > +     struct item *current = list;
> > > +
> > > +     while (current) {
> > > +             if (current->symb_name[0] != current_first_letter) {
> > > +                     current_first_letter = current->symb_name[0];
> > > +                     list_index[current_first_letter - 32] = current;
> > > +             }
> > > +             current = current->next;
> > > +     }
> > > +}
> > > +
> > > +struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr)
> > > +{
> > > +     struct item *new_item;
> > > +     struct item *current;
> > > +
> > > +     new_item = malloc(sizeof(struct item));
> > > +     if (!new_item)
> > > +             return NULL;
> > > +
> > > +     strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> > > +     new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> > > +     new_item->addr = addr;
> > > +     new_item->stype = stype;
> > > +     new_item->next = NULL;
> > > +
> > > +     if (!(*list)) {
> > > +             *list = new_item;
> > > +     } else {
> > > +             current = *list;
> > > +             while (current->next)
> > > +                     current = current->next;
> > > +
> > > +             current->next = new_item;
> > > +     }
> > > +     return new_item;
> > > +}
> > > +
> > > +void sort_list(struct item **list, int sort_by)
> > > +{
> > > +     struct item *current = *list;
> > > +     struct item *sorted = NULL;
> > > +     struct item *next_item;
> > > +     struct item *temp;
> > > +
> > > +     if (!(*list) || !((*list)->next))
> > > +             return;
> > > +
> > > +     while (current) {
> > > +             next_item = current->next;
> > > +             if (!sorted ||
> > > +                 (CHECK_ORDER_BY_ADDRESS(sort_by, current, sorted, <) ||
> > > +                 CHECK_ORDER_BY_NAME(sort_by, current, sorted, >=))) {
> > > +                     current->next = sorted;
> > > +                     sorted = current;
> > > +             } else {
> > > +                     temp = sorted;
> > > +                     while (temp->next &&
> > > +                            (CHECK_ORDER_BY_ADDRESS(sort_by, current, temp->next, >=) ||
> > > +                            CHECK_ORDER_BY_NAME(sort_by, current, temp->next, >=)))
> > > +                             temp = temp->next;
> > > +
> > > +                     current->next = temp->next;
> > > +                     temp->next = current;
> > > +             }
> > > +             current = next_item;
> > > +     }
> > > +
> > > +     *list = sorted;
> > > +}
> > > +
> > > +struct item *merge(struct item *left, struct item *right, int sort_by)
> > > +{
> > > +     struct item *current = NULL;
> > > +     struct item *result = NULL;
> > > +
> > > +     if (!left)
> > > +             return right;
> > > +     if (!right)
> > > +             return left;
> > > +
> > > +     if (sort_by == BY_NAME) {
> > > +             if (strcmp(left->symb_name, right->symb_name) <= 0) {
> > > +                     result = left;
> > > +                     left = left->next;
> > > +             } else {
> > > +                     result = right;
> > > +                     right = right->next;
> > > +             }
> > > +     } else {
> > > +             if (sort_by == BY_ADDRESS) {
> > > +                     if (left->addr <= right->addr) {
> > > +                             result = left;
> > > +                             left = left->next;
> > > +                     } else {
> > > +                             result = right;
> > > +                             right = right->next;
> > > +                     }
> > > +             }
> > > +     }
> > > +
> > > +     current = result;
> > > +
> > > +     while (left && right) {
> > > +             if (sort_by == BY_NAME) {
> > > +                     if (strcmp(left->symb_name, right->symb_name) <= 0) {
> > > +                             current->next = left;
> > > +                             left = left->next;
> > > +                     } else {
> > > +                             current->next = right;
> > > +                             right = right->next;
> > > +                     }
> > > +             } else {
> > > +                     if (sort_by == BY_ADDRESS) {
> > > +                             if (left->addr <= right->addr) {
> > > +                                     current->next = left;
> > > +                                     left = left->next;
> > > +                             } else {
> > > +                                     current->next = right;
> > > +                                     right = right->next;
> > > +                             }
> > > +                     }
> > > +             }
> > > +
> > > +             current = current->next;
> > > +     }
> > > +
> > > +     if (left) {
> > > +             current->next = left;
> > > +     } else {
> > > +             if (right)
> > > +                     current->next = right;
> > > +     }
> > > +
> > > +     return result;
> > > +}
> > > +
> > > +struct item *merge_sort(struct item *head, int sort_by)
> > > +{
> > > +     struct item *right;
> > > +     struct item *slow;
> > > +     struct item *fast;
> > > +     struct item *left;
> > > +
> > > +     if (!head || !head->next)
> > > +             return head;
> > > +
> > > +     slow = head;
> > > +     fast = head->next;
> > > +
> > > +     while (fast && fast->next) {
> > > +             slow = slow->next;
> > > +             fast = fast->next->next;
> > > +     }
> > > +
> > > +     left = head;
> > > +     right = slow->next;
> > > +     slow->next = NULL;
> > > +
> > > +     left = merge_sort(left, sort_by);
> > > +     right = merge_sort(right, sort_by);
> > > +
> > > +     return merge(left, right, sort_by);
> > > +}
> > > +
> > > +void sort_list_m(struct item **head, int sort_by)
> > > +{
> > > +     if (!(*head) || !((*head)->next))
> > > +             return;
> > > +
> > > +     *head = merge_sort(*head, sort_by);
> > > +}
> > > +
> > > +int insert_after(struct item *list, const uint64_t search_addr,
> > > +              const char *name, uint64_t addr, char stype)
> > > +{
> > > +     struct item *new_item;
> > > +     struct item *current;
> > > +     int ret = 0;
> > > +
> > > +     current = (list_index[name[0] - 32]) ? list_index[name[0] - 32] : list;
> > > +     while (current) {
> > > +             if (current->addr == search_addr) {
> > > +                     new_item = malloc(sizeof(struct item));
> > > +                     if (!new_item)
> > > +                             return ret;
> > > +                     strncpy(new_item->symb_name, name, MAX_NAME_SIZE);
> > > +                     new_item->symb_name[MAX_NAME_SIZE - 1] = '\0';
> > > +                     new_item->addr = addr;
> > > +                     new_item->stype = stype;
> > > +                     new_item->next = current->next;
> > > +                     current->next = new_item;
> > > +                     ret = 1;
> > > +                     break;
> > > +             }
> > > +             current = current->next;
> > > +     }
> > > +     return ret;
> > > +}
> > > +
> > > +void free_items(struct item **head)
> > > +{
> > > +     struct item *app, *item_iterator = *head;
> > > +
> > > +     while (item_iterator) {
> > > +             app = item_iterator;
> > > +             item_iterator = item_iterator->next;
> > > +             free(app);
> > > +     }
> > > +     *head = NULL;
> > > +}
> > > diff --git a/scripts/kas_alias/item_list.h b/scripts/kas_alias/item_list.h
> > > new file mode 100644
> > > index 000000000000..b4891cb088ee
> > > --- /dev/null
> > > +++ b/scripts/kas_alias/item_list.h
> > > @@ -0,0 +1,26 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > > +#ifndef ITEM_LIST_H
> > > +#define ITEM_LIST_H
> > > +#include <stdint.h>
> > > +
> > > +#define MAX_NAME_SIZE 256
> > > +#define BY_ADDRESS 1
> > > +#define BY_NAME 2
> > > +
> > > +struct item {
> > > +     char            symb_name[MAX_NAME_SIZE];
> > > +     uint64_t        addr;
> > > +     char            stype;
> > > +     struct item     *next;
> > > +};
> > > +
> > > +void build_index(struct item *list);
> > > +struct item *add_item(struct item **list, const char *name, char stype, uint64_t addr);
> > > +void sort_list(struct item **list, int sort_by);
> > > +struct item *merge(struct item *left, struct item *right, int sort_by);
> > > +struct item *merge_sort(struct item *head, int sort_by);
> > > +void sort_list_m(struct item **head, int sort_by);
> > > +int insert_after(struct item *list, const uint64_t search_addr,
> > > +              const char *name, uint64_t addr, char stype);
> > > +void free_items(struct item **head);
> > > +#endif
> > > diff --git a/scripts/kas_alias/kas_alias.c b/scripts/kas_alias/kas_alias.c
> > > new file mode 100644
> > > index 000000000000..532aeb39f851
> > > --- /dev/null
> > > +++ b/scripts/kas_alias/kas_alias.c
> > > @@ -0,0 +1,217 @@
> > > +// SPDX-License-Identifier: GPL-2.0-or-later
> > > +#include <stdio.h>
> > > +#include <stdlib.h>
> > > +#include <stdint.h>
> > > +#include <unistd.h>
> > > +#include <string.h>
> > > +#include <stdbool.h>
> > > +#include <stdarg.h>
> > > +#include <regex.h>
> > > +
> > > +#include "item_list.h"
> > > +#include "duplicates_list.h"
> > > +#include "a2l.h"
> > > +
> > > +#define SYMB_IS_TEXT(s) ((((s)->stype) == 't') ||  (((s)->stype) == 'T'))
> > > +#define SYMB_IS_DATA(s) ((((s)->stype) == 'b') ||  (((s)->stype) == 'B') || \
> > > +                      (((s)->stype) == 'd') ||  (((s)->stype) == 'D') || \
> > > +                      (((s)->stype) == 'r') ||  (((s)->stype) == 'R'))
> > > +#ifdef CONFIG_KALLSYMS_ALIAS_DATA
> > > +#define SYMB_NEEDS_ALIAS(s) (SYMB_IS_TEXT(s) || SYMB_IS_DATA(s))
> > > +#else
> > > +#define SYMB_NEEDS_ALIAS(s) SYMB_IS_TEXT(s)
> > > +#endif
> > > +#define FNOMATCH 0
> > > +#define FMATCH 1
> > > +#define EREGEX 2
> > > +
> > > +const char *ignore_regex[] = {
> > > +     "^__cfi_.*$",                           // __cfi_ preamble
> > > +#ifndef CONFIG_KALLSYMS_ALIAS_DATA_ALL
> > > +     "^_*TRACE_SYSTEM.*$",
> > > +     "^__already_done\\.[0-9]+$",            // Call a function once data
> > > +     "^___tp_str\\.[0-9]+$",
> > > +     "^___done\\.[0-9]+$",
> > > +     "^__print_once\\.[0-9]+$",
> > > +     "^_rs\\.[0-9]+$",
> > > +     "^__compound_literal\\.[0-9]+$",
> > > +     "^___once_key\\.[0-9]+$",
> > > +     "^__func__\\.[0-9]+$",
> > > +     "^__msg\\.[0-9]+$",
> > > +     "^CSWTCH\\.[0-9]+$",
> > > +     "^__flags\\.[0-9]+$",
> > > +     "^__wkey.*$",
> > > +     "^__mkey.*$",
> > > +     "^__key.*$",
> > > +#endif
> > > +     "^__pfx_.*$"                            // NOP-padding
> > > +};
> > > +
> > > +int suffix_serial;
> > > +
> > > +static inline void verbose_msg(bool verbose, const char *fmt, ...)
> > > +{
> > > +     va_list args;
> > > +
> > > +     va_start(args, fmt);
> > > +     if (verbose)
> > > +             printf(fmt, args);
> > > +
> > > +     va_end(args);
> > > +}
> > > +
> > > +static void create_suffix(const char *name, char *output_suffix)
> > > +{
> > > +     sprintf(output_suffix, "%s__alias__%d", name, suffix_serial++);
> > > +}
> > > +
> > > +static void create_file_suffix(const char *name, uint64_t address, char *output_suffix, char *cwd)
> > > +{
> > > +     const char *f_path;
> > > +     char *buf;
> > > +     int i = 0;
> > > +
> > > +     buf = addr2line_get_lines(address);
> > > +     f_path = remove_subdir(cwd, buf);
> > > +     if (f_path) {
> > > +             sprintf(output_suffix, "%s@%s", name, f_path);
> > > +             while (*(output_suffix + i) != '\0') {
> > > +                     switch (*(output_suffix + i)) {
> > > +                     case '/':
> > > +                     case ':':
> > > +                     case '.':
> >
> > This is not enough because file path will accept more than that.
> > E.g. '+', '&', '-'.
> > So I think we should check it by '!isalnum()'. (allow-list method)
> >
> > > +                             *(output_suffix + i) = '_';
> > > +                             break;
> > > +                     default:
> > > +                     }
> > > +             i++;
> > > +             }
> > > +     } else {
> > > +             create_suffix(name, output_suffix);
> > > +     }
> > > +}
> > > +
> > > +static int filter_symbols(char *symbol, const char **ignore_list, int regex_no)
> > > +{
> > > +     regex_t regex;
> > > +     int res, i;
> > > +
> > > +     for (i = 0; i < regex_no; i++) {
> > > +             res = regcomp(&regex, ignore_list[i], REG_EXTENDED);
> > > +             if (res)
> > > +                     return -EREGEX;
> > > +
> > > +             res = regexec(&regex, symbol, 0, NULL, 0);
> > > +             regfree(&regex);
> > > +             switch (res) {
> > > +             case 0:
> > > +                     return FMATCH;
> > > +             case REG_NOMATCH:
> > > +                     break;
> > > +             default:
> > > +                     return -EREGEX;
> > > +             }
> > > +     }
> > > +
> > > +     return FNOMATCH;
> > > +}
> > > +
> > > +int main(int argc, char *argv[])
> > > +{
> > > +     char t, sym_name[MAX_NAME_SIZE], new_name[MAX_NAME_SIZE + 15];
> > > +     struct duplicate_item  *duplicate_iterator;
> > > +     struct duplicate_item *duplicate;
> > > +     struct item *head = {NULL};
> > > +     bool need_2_process = true;
> > > +     struct item *last = {NULL};
> > > +     struct item  *current;
> > > +     int verbose_mode = 0;
> > > +     uint64_t address;
> > > +     FILE *fp;
> > > +     int res;
> > > +
> > > +     if (argc < 2 || argc > 3) {
> > > +             printf("Usage: %s <nmfile> [-verbose]\n", argv[0]);
> > > +             return 1;
> > > +     }
> > > +
> > > +     if (argc == 3 && strcmp(argv[2], "-verbose") == 0)
> > > +             verbose_mode = 1;
> > > +
> > > +     verbose_msg(verbose_mode, "Scanning nm data(%s)\n", argv[1]);
> > > +
> > > +     fp = fopen(argv[1], "r");
> > > +     if (!fp) {
> > > +             printf("Can't open input file.\n");
> > > +             return 1;
> > > +     }
> > > +
> > > +     if (!addr2line_init(get_addr2line(A2L_DEFAULT), get_vmlinux(argv[1])))
> > > +             return 1;
> > > +
> > > +     while (fscanf(fp, "%lx %c %99s\n", &address, &t, sym_name) == 3) {
> > > +             if (strstr(sym_name, "@_")) {
> > > +                     if (verbose_mode && need_2_process)
> > > +                             printf("Already processed\n");
> > > +                     need_2_process = false;
> > > +                     }
> > > +             last = add_item(&last, sym_name, t, address);
> > > +             if (!last) {
> > > +                     printf("Error in allocate memory\n");
> > > +                     free_items(&head);
> > > +                     return 1;
> > > +             }
> > > +
> > > +             if (!head)
> > > +                     head = last;
> > > +     }
> > > +
> > > +     fclose(fp);
> > > +
> > > +     if (need_2_process) {
> > > +             verbose_msg(verbose_mode, "Sorting nm data\n");
> > > +             sort_list_m(&head, BY_NAME);
> > > +             verbose_msg(verbose_mode, "Scanning nm data for duplicates\n");
> > > +             duplicate = find_duplicates(head);
> > > +             if (!duplicate) {
> > > +                     printf("Error in duplicates list\n");
> > > +                     return 1;
> > > +             }
> > > +
> > > +             verbose_msg(verbose_mode, "Applying suffixes\n");
> > > +             build_index(head);
> > > +             duplicate_iterator = duplicate;
> > > +             while (duplicate_iterator) {
> > > +                     res = filter_symbols(duplicate_iterator->original_item->symb_name,
> > > +                                          ignore_regex, sizeof(ignore_regex) /
> > > +                                          sizeof(ignore_regex[0]));
> > > +                     if (res != FMATCH &&
> > > +                         SYMB_NEEDS_ALIAS(duplicate_iterator->original_item)) {
> > > +                             if (res < 0)
> > > +                                     return 1;
> > > +
> > > +                             create_file_suffix(duplicate_iterator->original_item->symb_name,
> > > +                                                duplicate_iterator->original_item->addr,
> > > +                                                new_name, vmlinux_path);
> > > +                             if (!insert_after(head, duplicate_iterator->original_item->addr,
> > > +                                               new_name, duplicate_iterator->original_item->addr,
> > > +                                               duplicate_iterator->original_item->stype))
> > > +                                     return 1;
> > > +                     }
> > > +
> > > +                     duplicate_iterator = duplicate_iterator->next;
> > > +             }
> > > +
> > > +             sort_list_m(&head, BY_ADDRESS);
> > > +     }
> > > +     current = head;
> > > +     while (current) {
> > > +             printf("%08lx %c %s\n", current->addr, current->stype, current->symb_name);
> > > +             current = current->next;
> > > +     }
> > > +
> > > +     free_items(&head);
> > > +     free_duplicates(&duplicate);
> > > +     addr2line_cleanup();
> > > +     return 0;
> > > +}
> > > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> > > index a432b171be82..cacf60b597ce 100755
> > > --- a/scripts/link-vmlinux.sh
> > > +++ b/scripts/link-vmlinux.sh
> > > @@ -89,8 +89,9 @@ vmlinux_link()
> > >
> > >       ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
> > >
> > > -     # The kallsyms linking does not need debug symbols included.
> > > -     if [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> > > +     # The kallsyms linking does not need debug symbols included, unless the KALLSYMS_ALIAS.
> > > +     if [ ! is_enabled CONFIG_KALLSYMS_ALIAS ] && \
> > > +         [ "$output" != "${output#.tmp_vmlinux.kallsyms}" ] ; then
> > >               ldflags="${ldflags} ${wl}--strip-debug"
> > >       fi
> > >
> > > @@ -161,7 +162,11 @@ kallsyms()
> > >       fi
> > >
> > >       info KSYMS ${2}
> > > -     scripts/kallsyms ${kallsymopt} ${1} > ${2}
> > > +     if is_enabled CONFIG_KALLSYMS_ALIAS; then
> > > +             ALIAS=".alias"
> > > +             scripts/kas_alias/kas_alias ${1} >${1}${ALIAS}
> > > +             fi
> >
> > Nit: wrong indentation.
> > And ALIAS is not defined if CONFIG_KALLSYMS_ALIAS=n.
> 
> I rely on the fact that ALIAS is undefined if CONFIG_KALLSYMS_ALIAS=n.
> The undefined variable expands to an empty string, and I was constructing
> my name using this approach. This method functions in this manner with
> all the shells I'm familiar with.

yeah, but I feel this is fragile. you can just add "else" block and
initialize ALIAS with empty string for maintenanceability.

> However, I acknowledge that it's more of a hack than a clean programming
> practice. In version 4, I will provide a cleaner shell programming
> solution.

OK.

Thank you!

> 
> >
> >
> > > +     scripts/kallsyms ${kallsymopt} ${1}${ALIAS} > ${2}
> > >  }
> > >
> > >  # Perform one step in kallsyms generation, including temporary linking of
> > > --
> > > 2.34.1
> > >
> >
> >
> > Thank you,
> >
> > --
> > Masami Hiramatsu (Google) <mhiramat@kernel.org>


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-09-02  7:40   ` Alessandro Carminati
@ 2023-09-04 13:09     ` Francis Laniel
  0 siblings, 0 replies; 16+ messages in thread
From: Francis Laniel @ 2023-09-04 13:09 UTC (permalink / raw)
  To: Masahiro Yamada, Alessandro Carminati
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Luis Chamberlain, Nathan Chancellor,
	Nick Desaulniers, Nicolas Schier, Alexander Lobakin, Nick Alcock,
	Kris Van Hees, Eugene Loh, Viktor Malik, linux-kbuild,
	linux-kernel, linux-trace-kernel, live-patching

Hi.

Le samedi 2 septembre 2023, 09:40:46 CEST Alessandro Carminati a écrit :
> Il giorno sab 2 set 2023 alle ore 08:36 Masahiro Yamada
> 
> <masahiroy@kernel.org> ha scritto:
> > On Mon, Aug 28, 2023 at 8:45 PM Alessandro Carminati (Red Hat)
> > 
> > <alessandro.carminati@gmail.com> wrote:
> > > From: Alessandro Carminati <alessandro.carminati@gmail.com>
> > > 
> > > It is not uncommon for drivers or modules related to similar peripherals
> > > to have symbols with the exact same name.
> > > While this is not a problem for the kernel's binary itself, it becomes
> > > an
> > > issue when attempting to trace or probe specific functions using
> > > infrastructure like ftrace or kprobe.
> > > 
> > > The tracing subsystem relies on the `nm -n vmlinux` output, which
> > > provides
> > > symbol information from the kernel's ELF binary. However, when multiple
> > > symbols share the same name, the standard nm output does not
> > > differentiate
> > > between them. This can lead to confusion and difficulty when trying to
> > > probe the intended symbol.
> > > 
> > >  ~ # cat /proc/kallsyms | grep " name_show"
> > >  ffffffff8c4f76d0 t name_show
> > >  ffffffff8c9cccb0 t name_show
> > >  ffffffff8cb0ac20 t name_show
> > >  ffffffff8cc728c0 t name_show
> > >  ffffffff8ce0efd0 t name_show
> > >  ffffffff8ce126c0 t name_show
> > >  ffffffff8ce1dd20 t name_show
> > >  ffffffff8ce24e70 t name_show
> > >  ffffffff8d1104c0 t name_show
> > >  ffffffff8d1fe480 t name_show
> > > 
> > > **kas_alias** addresses this challenge by extending the symbol names
> > > with
> > > unique suffixes during the kernel build process.
> > > The newly created aliases for these duplicated symbols are unique names
> > > that can be fed to the ftracefs interface. By doing so, it enables
> > > previously unreachable symbols to be probed.
> > > 
> > >  ~ # cat /proc/kallsyms | grep " name_show"
> > >  ffffffff974f76d0 t name_show
> > >  ffffffff974f76d0 t name_show__alias__6340
> > >  ffffffff979cccb0 t name_show
> > >  ffffffff979cccb0 t name_show__alias__6341
> > >  ffffffff97b0ac20 t name_show
> > >  ffffffff97b0ac20 t name_show__alias__6342
> > >  ffffffff97c728c0 t name_show
> > >  ffffffff97c728c0 t name_show__alias__6343
> > >  ffffffff97e0efd0 t name_show
> > >  ffffffff97e0efd0 t name_show__alias__6344
> > >  ffffffff97e126c0 t name_show
> > >  ffffffff97e126c0 t name_show__alias__6345
> > >  ffffffff97e1dd20 t name_show
> > >  ffffffff97e1dd20 t name_show__alias__6346
> > >  ffffffff97e24e70 t name_show
> > >  ffffffff97e24e70 t name_show__alias__6347
> > >  ffffffff981104c0 t name_show
> > >  ffffffff981104c0 t name_show__alias__6348
> > >  ffffffff981fe480 t name_show
> > >  ffffffff981fe480 t name_show__alias__6349
> > >  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
> > >  
> > >  > >/sys/kernel/tracing/kprobe_events
> > >  
> > >  ~ # cat /sys/kernel/tracing/kprobe_events
> > >  p:kprobes/evnt1 name_show__alias__6349
> > > 
> > > Changes from v1:
> > > - Integrated changes requested by Masami to exclude symbols with
> > > prefixes
> > > 
> > >   "_cfi" and "_pfx".
> > > 
> > > - Introduced a small framework to handle patterns that need to be
> > > excluded
> > > 
> > >   from the alias production.
> > > 
> > > - Excluded other symbols using the framework.
> > > - Introduced the ability to discriminate between text and data symbols.
> > > - Added two new config symbols in this version:
> > > CONFIG_KALLSYMS_ALIAS_DATA,
> > > 
> > >   which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
> > >   excludes all filters and provides an alias for each duplicated symbol.
> > > 
> > > https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminat
> > > i@gmail.com/
> > > 
> > > Changes from v2:
> > > - Alias tags are created by querying DWARF information from the vmlinux.
> > > - The filename + line number is normalized and appended to the original
> > > name. - The tag begins with '@' to indicate the symbol source.
> > > - Not a change, but worth mentioning, since the alias is added to the
> > > existing> > 
> > >   list, the old duplicated name is preserved, and the livepatch way of
> > >   dealing with duplicates is maintained.
> > > 
> > > - Acknowledging the existence of scenarios where inlined functions
> > > declared in> > 
> > >   header files may result in multiple copies due to compiler behavior,
> > >   though
> > >   
> > >    it is not actionable as it does not pose an operational issue.
> > > 
> > > - Highlighting a single exception where the same name refers to
> > > different
> > > 
> > >   functions: the case of "compat_binfmt_elf.c," which directly includes
> > >   "binfmt_elf.c" producing identical function copies in two separate
> > >   modules.
> > > 
> > > sample from new v3
> > > 
> > >  ~ # cat /proc/kallsyms | grep gic_mask_irq
> > >  ffffd0b03c04dae4 t gic_mask_irq
> > >  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
> > >  ffffd0b03c050960 t gic_mask_irq
> > >  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
> > >  ~ #
> > > 
> > > https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminat
> > > i@gmail.com/
> > > 
> > > Signed-off-by: Alessandro Carminati (Red Hat)
> > > <alessandro.carminati@gmail.com> ---
> > > 
> > >  init/Kconfig                        |  36 ++++
> > >  scripts/Makefile                    |   4 +
> > >  scripts/kas_alias/Makefile          |   4 +
> > >  scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
> > >  scripts/kas_alias/a2l.h             |  32 ++++
> > >  scripts/kas_alias/duplicates_list.c |  70 ++++++++
> > >  scripts/kas_alias/duplicates_list.h |  15 ++
> > >  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
> > >  scripts/kas_alias/item_list.h       |  26 +++
> > >  scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
> > >  scripts/link-vmlinux.sh             |  11 +-
> > >  11 files changed, 910 insertions(+), 3 deletions(-)
> > 
> > I added some review comments in another thread, but
> > one of the biggest concerns might be "910 insertions".
> 
> Based on the feedback I received in the reviews, I need to overhaul the
> code, potentially reducing its size. What would be a reasonable number
> of lines for this feature?
> 
> > What this program does is quite simple,
> > "find duplicated names, and call addr2line".
> > 
> > You wrote a lot of code to self-implement these:
> >  - sort function
> >  - parse PATH env variable to find addr2line
> >  - fork addr2line to establish pipe communications
> 
> Some of these functions might become obsolete in the upcoming v4, which
> will certainly reduce the line count.
> 
> > Have you considered writing the code in Python (or Perl)?
> > Is it too slow?
> >
> >From my perspective, there is a concern that using Python or Perl might
> 
> result in slower performance. My proficiency in Python and Perl is
> limited, so I did not initially consider them as viable options for
> implementing this solution.
> 
> > Most of the functions you implemented are already
> > available in script languages.
> > 
> > 
> > 
> > I am not sure if "@<file-path>" is a good solution,
> > but the amount of the added code looks too much to me.
> 
> I had reservations about using the '@' symbol to decorate the alias because
> it's not a character commonly found in the kallsyms output. However, after
> careful consideration, I arrived at the conclusion that it was suitable for
> the task because it would make the alias stand-out and be easily
> identifiable.
> I'm open to any suggestions or alternative approaches you may have on this
> matter.

I am maybe over-engineering the thing, but maybe we can have a 
CONFIG_KALLSYMS_ALIAS_FORMAT which users would set to indicate how to 
differentiate between two symbols?
For example, CONFIG_KALLSYMS_ALIAS_FORMAT=@file-lineno would lead to what we 
have currently.
If you switch to using a higher level language, you can maybe focus more on 
this.
Anyway, I personally like what this contribution offers currently as it permits 
to distinguish between same symbols.
I will take a look at v4! Thank you again for working on this.

> > --
> > Best Regards
> > Masahiro Yamada
> 
> Thank you

Best regards.



^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-09-02  6:36 ` Masahiro Yamada
  2023-09-02  7:40   ` Alessandro Carminati
@ 2023-09-06 10:09   ` Alessandro Carminati
  2023-09-06 15:06     ` Masahiro Yamada
  1 sibling, 1 reply; 16+ messages in thread
From: Alessandro Carminati @ 2023-09-06 10:09 UTC (permalink / raw)
  To: Masahiro Yamada
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Luis Chamberlain, Nathan Chancellor,
	Nick Desaulniers, Nicolas Schier, Alexander Lobakin, Nick Alcock,
	Kris Van Hees, Eugene Loh, Francis Laniel, Viktor Malik,
	linux-kbuild, linux-kernel, linux-trace-kernel, live-patching

Hello Masahiro,

Thank you for your suggestions,
Il giorno sab 2 set 2023 alle ore 08:36 Masahiro Yamada
<masahiroy@kernel.org> ha scritto:
>
> On Mon, Aug 28, 2023 at 8:45 PM Alessandro Carminati (Red Hat)
> <alessandro.carminati@gmail.com> wrote:
> >
> > From: Alessandro Carminati <alessandro.carminati@gmail.com>
> >
> > It is not uncommon for drivers or modules related to similar peripherals
> > to have symbols with the exact same name.
> > While this is not a problem for the kernel's binary itself, it becomes an
> > issue when attempting to trace or probe specific functions using
> > infrastructure like ftrace or kprobe.
> >
> > The tracing subsystem relies on the `nm -n vmlinux` output, which provides
> > symbol information from the kernel's ELF binary. However, when multiple
> > symbols share the same name, the standard nm output does not differentiate
> > between them. This can lead to confusion and difficulty when trying to
> > probe the intended symbol.
> >
> >  ~ # cat /proc/kallsyms | grep " name_show"
> >  ffffffff8c4f76d0 t name_show
> >  ffffffff8c9cccb0 t name_show
> >  ffffffff8cb0ac20 t name_show
> >  ffffffff8cc728c0 t name_show
> >  ffffffff8ce0efd0 t name_show
> >  ffffffff8ce126c0 t name_show
> >  ffffffff8ce1dd20 t name_show
> >  ffffffff8ce24e70 t name_show
> >  ffffffff8d1104c0 t name_show
> >  ffffffff8d1fe480 t name_show
> >
> > **kas_alias** addresses this challenge by extending the symbol names with
> > unique suffixes during the kernel build process.
> > The newly created aliases for these duplicated symbols are unique names
> > that can be fed to the ftracefs interface. By doing so, it enables
> > previously unreachable symbols to be probed.
> >
> >  ~ # cat /proc/kallsyms | grep " name_show"
> >  ffffffff974f76d0 t name_show
> >  ffffffff974f76d0 t name_show__alias__6340
> >  ffffffff979cccb0 t name_show
> >  ffffffff979cccb0 t name_show__alias__6341
> >  ffffffff97b0ac20 t name_show
> >  ffffffff97b0ac20 t name_show__alias__6342
> >  ffffffff97c728c0 t name_show
> >  ffffffff97c728c0 t name_show__alias__6343
> >  ffffffff97e0efd0 t name_show
> >  ffffffff97e0efd0 t name_show__alias__6344
> >  ffffffff97e126c0 t name_show
> >  ffffffff97e126c0 t name_show__alias__6345
> >  ffffffff97e1dd20 t name_show
> >  ffffffff97e1dd20 t name_show__alias__6346
> >  ffffffff97e24e70 t name_show
> >  ffffffff97e24e70 t name_show__alias__6347
> >  ffffffff981104c0 t name_show
> >  ffffffff981104c0 t name_show__alias__6348
> >  ffffffff981fe480 t name_show
> >  ffffffff981fe480 t name_show__alias__6349
> >  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
> >  > >/sys/kernel/tracing/kprobe_events
> >  ~ # cat /sys/kernel/tracing/kprobe_events
> >  p:kprobes/evnt1 name_show__alias__6349
> >
> > Changes from v1:
> > - Integrated changes requested by Masami to exclude symbols with prefixes
> >   "_cfi" and "_pfx".
> > - Introduced a small framework to handle patterns that need to be excluded
> >   from the alias production.
> > - Excluded other symbols using the framework.
> > - Introduced the ability to discriminate between text and data symbols.
> > - Added two new config symbols in this version: CONFIG_KALLSYMS_ALIAS_DATA,
> >   which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
> >   excludes all filters and provides an alias for each duplicated symbol.
> >
> > https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gmail.com/
> >
> > Changes from v2:
> > - Alias tags are created by querying DWARF information from the vmlinux.
> > - The filename + line number is normalized and appended to the original name.
> > - The tag begins with '@' to indicate the symbol source.
> > - Not a change, but worth mentioning, since the alias is added to the existing
> >   list, the old duplicated name is preserved, and the livepatch way of dealing
> >   with duplicates is maintained.
> > - Acknowledging the existence of scenarios where inlined functions declared in
> >   header files may result in multiple copies due to compiler behavior, though
> >    it is not actionable as it does not pose an operational issue.
> > - Highlighting a single exception where the same name refers to different
> >   functions: the case of "compat_binfmt_elf.c," which directly includes
> >   "binfmt_elf.c" producing identical function copies in two separate
> >   modules.
> >
> > sample from new v3
> >
> >  ~ # cat /proc/kallsyms | grep gic_mask_irq
> >  ffffd0b03c04dae4 t gic_mask_irq
> >  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
> >  ffffd0b03c050960 t gic_mask_irq
> >  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
> >  ~ #
> >
> > https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gmail.com/
> >
> > Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> > ---
> >  init/Kconfig                        |  36 ++++
> >  scripts/Makefile                    |   4 +
> >  scripts/kas_alias/Makefile          |   4 +
> >  scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
> >  scripts/kas_alias/a2l.h             |  32 ++++
> >  scripts/kas_alias/duplicates_list.c |  70 ++++++++
> >  scripts/kas_alias/duplicates_list.h |  15 ++
> >  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
> >  scripts/kas_alias/item_list.h       |  26 +++
> >  scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
> >  scripts/link-vmlinux.sh             |  11 +-
> >  11 files changed, 910 insertions(+), 3 deletions(-)
>
>
> I added some review comments in another thread, but
> one of the biggest concerns might be "910 insertions".
>
>
> What this program does is quite simple,
> "find duplicated names, and call addr2line".
>
>
>
> You wrote a lot of code to self-implement these:
>
>  - sort function
>  - parse PATH env variable to find addr2line
>  - fork addr2line to establish pipe communications
>
>
>
> Have you considered writing the code in Python (or Perl)?
> Is it too slow?

I have attempted to incorporate all your suggestions.
I refactored the C code to utilize hashing instead of sorting, and I
completely re-implemented the entire thing in Python for the purpose of
comparison.

You are correct;
the C version is indeed faster, but the difference is negligible when
considering the use case and code maintainability.

Here's a direct comparison of the two.
```
~ $ time ./kas_alias.py -a /usr/bin/aarch64-linux-gnu-addr2line \
                      -n linux-6.5/.tmp_vmlinux.kallsyms1.syms \
                      -v linux-6.5/.tmp_vmlinux.kallsyms1 \
                      -o output_py

real    0m1.626s
user    0m1.436s
sys     0m0.185s
$ cat kas_alias.py | wc -l
133
~ $ time ./kas_alias -a /usr/bin/aarch64-linux-gnu-addr2line \
                   -v linux-6.5/.tmp_vmlinux.kallsyms1 \
                   -n linux-6.5/.tmp_vmlinux.kallsyms1.syms \
                   -o output_c

real    0m1.418s
user    0m1.262s
sys     0m0.162s
~ $ cat a2l.c a2l.h conf.c conf.h item_list.c item_list.h kas_alias.c | wc -l
742
~ $ diff output_py output_c
~ $
```
C version is 7/10% faster but is more than 5 times in terms of code size.

>
> Most of the functions you implemented are already
> available in script languages.
>
>
>
> I am not sure if "@<file-path>" is a good solution,
> but the amount of the added code looks too much to me.

I followed Francis's suggestion and made the separator between
<symbol name> and <normalized filename> an argument that you can select
using the command line. Since I'm not aware of a better choice, I set the
default value to '@'.

>
>
>
>
> --
> Best Regards
> Masahiro Yamada

Best regards
Alessandro Carminati

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-09-06 10:09   ` Alessandro Carminati
@ 2023-09-06 15:06     ` Masahiro Yamada
  0 siblings, 0 replies; 16+ messages in thread
From: Masahiro Yamada @ 2023-09-06 15:06 UTC (permalink / raw)
  To: Alessandro Carminati
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Luis Chamberlain, Nathan Chancellor,
	Nick Desaulniers, Nicolas Schier, Alexander Lobakin, Nick Alcock,
	Kris Van Hees, Eugene Loh, Francis Laniel, Viktor Malik,
	linux-kbuild, linux-kernel, linux-trace-kernel, live-patching

On Wed, Sep 6, 2023 at 7:09 PM Alessandro Carminati
<alessandro.carminati@gmail.com> wrote:
>
> Hello Masahiro,
>
> Thank you for your suggestions,
> Il giorno sab 2 set 2023 alle ore 08:36 Masahiro Yamada
> <masahiroy@kernel.org> ha scritto:
> >
> > On Mon, Aug 28, 2023 at 8:45 PM Alessandro Carminati (Red Hat)
> > <alessandro.carminati@gmail.com> wrote:
> > >
> > > From: Alessandro Carminati <alessandro.carminati@gmail.com>
> > >
> > > It is not uncommon for drivers or modules related to similar peripherals
> > > to have symbols with the exact same name.
> > > While this is not a problem for the kernel's binary itself, it becomes an
> > > issue when attempting to trace or probe specific functions using
> > > infrastructure like ftrace or kprobe.
> > >
> > > The tracing subsystem relies on the `nm -n vmlinux` output, which provides
> > > symbol information from the kernel's ELF binary. However, when multiple
> > > symbols share the same name, the standard nm output does not differentiate
> > > between them. This can lead to confusion and difficulty when trying to
> > > probe the intended symbol.
> > >
> > >  ~ # cat /proc/kallsyms | grep " name_show"
> > >  ffffffff8c4f76d0 t name_show
> > >  ffffffff8c9cccb0 t name_show
> > >  ffffffff8cb0ac20 t name_show
> > >  ffffffff8cc728c0 t name_show
> > >  ffffffff8ce0efd0 t name_show
> > >  ffffffff8ce126c0 t name_show
> > >  ffffffff8ce1dd20 t name_show
> > >  ffffffff8ce24e70 t name_show
> > >  ffffffff8d1104c0 t name_show
> > >  ffffffff8d1fe480 t name_show
> > >
> > > **kas_alias** addresses this challenge by extending the symbol names with
> > > unique suffixes during the kernel build process.
> > > The newly created aliases for these duplicated symbols are unique names
> > > that can be fed to the ftracefs interface. By doing so, it enables
> > > previously unreachable symbols to be probed.
> > >
> > >  ~ # cat /proc/kallsyms | grep " name_show"
> > >  ffffffff974f76d0 t name_show
> > >  ffffffff974f76d0 t name_show__alias__6340
> > >  ffffffff979cccb0 t name_show
> > >  ffffffff979cccb0 t name_show__alias__6341
> > >  ffffffff97b0ac20 t name_show
> > >  ffffffff97b0ac20 t name_show__alias__6342
> > >  ffffffff97c728c0 t name_show
> > >  ffffffff97c728c0 t name_show__alias__6343
> > >  ffffffff97e0efd0 t name_show
> > >  ffffffff97e0efd0 t name_show__alias__6344
> > >  ffffffff97e126c0 t name_show
> > >  ffffffff97e126c0 t name_show__alias__6345
> > >  ffffffff97e1dd20 t name_show
> > >  ffffffff97e1dd20 t name_show__alias__6346
> > >  ffffffff97e24e70 t name_show
> > >  ffffffff97e24e70 t name_show__alias__6347
> > >  ffffffff981104c0 t name_show
> > >  ffffffff981104c0 t name_show__alias__6348
> > >  ffffffff981fe480 t name_show
> > >  ffffffff981fe480 t name_show__alias__6349
> > >  ~ # echo "p:kprobes/evnt1 name_show__alias__6349" \
> > >  > >/sys/kernel/tracing/kprobe_events
> > >  ~ # cat /sys/kernel/tracing/kprobe_events
> > >  p:kprobes/evnt1 name_show__alias__6349
> > >
> > > Changes from v1:
> > > - Integrated changes requested by Masami to exclude symbols with prefixes
> > >   "_cfi" and "_pfx".
> > > - Introduced a small framework to handle patterns that need to be excluded
> > >   from the alias production.
> > > - Excluded other symbols using the framework.
> > > - Introduced the ability to discriminate between text and data symbols.
> > > - Added two new config symbols in this version: CONFIG_KALLSYMS_ALIAS_DATA,
> > >   which allows data for data, and CONFIG_KALLSYMS_ALIAS_DATA_ALL, which
> > >   excludes all filters and provides an alias for each duplicated symbol.
> > >
> > > https://lore.kernel.org/all/20230711151925.1092080-1-alessandro.carminati@gmail.com/
> > >
> > > Changes from v2:
> > > - Alias tags are created by querying DWARF information from the vmlinux.
> > > - The filename + line number is normalized and appended to the original name.
> > > - The tag begins with '@' to indicate the symbol source.
> > > - Not a change, but worth mentioning, since the alias is added to the existing
> > >   list, the old duplicated name is preserved, and the livepatch way of dealing
> > >   with duplicates is maintained.
> > > - Acknowledging the existence of scenarios where inlined functions declared in
> > >   header files may result in multiple copies due to compiler behavior, though
> > >    it is not actionable as it does not pose an operational issue.
> > > - Highlighting a single exception where the same name refers to different
> > >   functions: the case of "compat_binfmt_elf.c," which directly includes
> > >   "binfmt_elf.c" producing identical function copies in two separate
> > >   modules.
> > >
> > > sample from new v3
> > >
> > >  ~ # cat /proc/kallsyms | grep gic_mask_irq
> > >  ffffd0b03c04dae4 t gic_mask_irq
> > >  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
> > >  ffffd0b03c050960 t gic_mask_irq
> > >  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
> > >  ~ #
> > >
> > > https://lore.kernel.org/all/20230714150326.1152359-1-alessandro.carminati@gmail.com/
> > >
> > > Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> > > ---
> > >  init/Kconfig                        |  36 ++++
> > >  scripts/Makefile                    |   4 +
> > >  scripts/kas_alias/Makefile          |   4 +
> > >  scripts/kas_alias/a2l.c             | 268 ++++++++++++++++++++++++++++
> > >  scripts/kas_alias/a2l.h             |  32 ++++
> > >  scripts/kas_alias/duplicates_list.c |  70 ++++++++
> > >  scripts/kas_alias/duplicates_list.h |  15 ++
> > >  scripts/kas_alias/item_list.c       | 230 ++++++++++++++++++++++++
> > >  scripts/kas_alias/item_list.h       |  26 +++
> > >  scripts/kas_alias/kas_alias.c       | 217 ++++++++++++++++++++++
> > >  scripts/link-vmlinux.sh             |  11 +-
> > >  11 files changed, 910 insertions(+), 3 deletions(-)
> >
> >
> > I added some review comments in another thread, but
> > one of the biggest concerns might be "910 insertions".
> >
> >
> > What this program does is quite simple,
> > "find duplicated names, and call addr2line".
> >
> >
> >
> > You wrote a lot of code to self-implement these:
> >
> >  - sort function
> >  - parse PATH env variable to find addr2line
> >  - fork addr2line to establish pipe communications
> >
> >
> >
> > Have you considered writing the code in Python (or Perl)?
> > Is it too slow?
>
> I have attempted to incorporate all your suggestions.
> I refactored the C code to utilize hashing instead of sorting, and I
> completely re-implemented the entire thing in Python for the purpose of
> comparison.
>
> You are correct;
> the C version is indeed faster, but the difference is negligible when
> considering the use case and code maintainability.


Nice. Then, I prefer shorter code.

The Python implementation is 0.2 sec slower
(given the script is executed three times, 0.6 sec cost in total)
but it is not a big issue, I think.

Thanks.









>
> Here's a direct comparison of the two.
> ```
> ~ $ time ./kas_alias.py -a /usr/bin/aarch64-linux-gnu-addr2line \
>                       -n linux-6.5/.tmp_vmlinux.kallsyms1.syms \
>                       -v linux-6.5/.tmp_vmlinux.kallsyms1 \
>                       -o output_py
>
> real    0m1.626s
> user    0m1.436s
> sys     0m0.185s
> $ cat kas_alias.py | wc -l
> 133
> ~ $ time ./kas_alias -a /usr/bin/aarch64-linux-gnu-addr2line \
>                    -v linux-6.5/.tmp_vmlinux.kallsyms1 \
>                    -n linux-6.5/.tmp_vmlinux.kallsyms1.syms \
>                    -o output_c
>
> real    0m1.418s
> user    0m1.262s
> sys     0m0.162s
> ~ $ cat a2l.c a2l.h conf.c conf.h item_list.c item_list.h kas_alias.c | wc -l
> 742
> ~ $ diff output_py output_c
> ~ $
> ```
> C version is 7/10% faster but is more than 5 times in terms of code size.
>
> >
> > Most of the functions you implemented are already
> > available in script languages.
> >
> >
> >
> > I am not sure if "@<file-path>" is a good solution,
> > but the amount of the added code looks too much to me.
>
> I followed Francis's suggestion and made the separator between
> <symbol name> and <normalized filename> an argument that you can select
> using the command line. Since I'm not aware of a better choice, I set the
> default value to '@'.
>
> >
> >
> >
> >
> > --
> > Best Regards
> > Masahiro Yamada
>
> Best regards
> Alessandro Carminati



-- 
Best Regards
Masahiro Yamada

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-08-28  8:04 [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms Alessandro Carminati (Red Hat)
                   ` (3 preceding siblings ...)
  2023-09-02  6:36 ` Masahiro Yamada
@ 2023-09-11 14:21 ` Alexander Lobakin
  2023-09-12 14:18   ` Alessandro Carminati
  4 siblings, 1 reply; 16+ messages in thread
From: Alexander Lobakin @ 2023-09-11 14:21 UTC (permalink / raw)
  To: Alessandro Carminati (Red Hat)
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Masahiro Yamada, Luis Chamberlain,
	Nathan Chancellor, Nick Desaulniers, Nicolas Schier, Nick Alcock,
	Kris Van Hees, Eugene Loh, Francis Laniel, Viktor Malik,
	linux-kbuild, linux-kernel, linux-trace-kernel, live-patching

From: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
Date: Mon, 28 Aug 2023 08:04:23 +0000

> From: Alessandro Carminati <alessandro.carminati@gmail.com>
> 
> It is not uncommon for drivers or modules related to similar peripherals
> to have symbols with the exact same name.

[...]

> Changes from v2:
> - Alias tags are created by querying DWARF information from the vmlinux.
> - The filename + line number is normalized and appended to the original name.
> - The tag begins with '@' to indicate the symbol source.
> - Not a change, but worth mentioning, since the alias is added to the existing
>   list, the old duplicated name is preserved, and the livepatch way of dealing
>   with duplicates is maintained.
> - Acknowledging the existence of scenarios where inlined functions declared in
>   header files may result in multiple copies due to compiler behavior, though
>    it is not actionable as it does not pose an operational issue.
> - Highlighting a single exception where the same name refers to different
>   functions: the case of "compat_binfmt_elf.c," which directly includes
>   "binfmt_elf.c" producing identical function copies in two separate
>   modules.

Oh, I thought you managed to handle this in v3 since you didn't reply in
the previous thread...

> 
> sample from new v3
> 
>  ~ # cat /proc/kallsyms | grep gic_mask_irq
>  ffffd0b03c04dae4 t gic_mask_irq
>  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
>  ffffd0b03c050960 t gic_mask_irq
>  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404

BTW, why normalize them? Why not just

gic_mask_irq@drivers/irqchip/...

Aaaaand why line number? Line numbers break reproducible builds and also
would make it harder to refer to a particular symbol by its path and
name since we also have to pass its line number which may change once
you add a debug print there, for example.
OTOH there can't be 2 symbols with the same name within one file, so
just path + name would be enough. Or not?

(sorry if some of this was already discussed previously)

[...]

Thanks,
Olek

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-09-11 14:21 ` Alexander Lobakin
@ 2023-09-12 14:18   ` Alessandro Carminati
  2023-09-13  8:06     ` Petr Mladek
  0 siblings, 1 reply; 16+ messages in thread
From: Alessandro Carminati @ 2023-09-12 14:18 UTC (permalink / raw)
  To: Alexander Lobakin
  Cc: Masami Hiramatsu, Steven Rostedt, Daniel Bristot de Oliveira,
	Josh Poimboeuf, Masahiro Yamada, Luis Chamberlain,
	Nathan Chancellor, Nick Desaulniers, Nicolas Schier, Nick Alcock,
	Kris Van Hees, Eugene Loh, Francis Laniel, Viktor Malik,
	linux-kbuild, linux-kernel, linux-trace-kernel, live-patching

Hello Alexander,

Thank you for your mail.

Il giorno lun 11 set 2023 alle ore 16:26 Alexander Lobakin
<aleksander.lobakin@intel.com> ha scritto:
>
> From: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> Date: Mon, 28 Aug 2023 08:04:23 +0000
>
> > From: Alessandro Carminati <alessandro.carminati@gmail.com>
> >
> > It is not uncommon for drivers or modules related to similar peripherals
> > to have symbols with the exact same name.
>
> [...]
>
> > Changes from v2:
> > - Alias tags are created by querying DWARF information from the vmlinux.
> > - The filename + line number is normalized and appended to the original name.
> > - The tag begins with '@' to indicate the symbol source.
> > - Not a change, but worth mentioning, since the alias is added to the existing
> >   list, the old duplicated name is preserved, and the livepatch way of dealing
> >   with duplicates is maintained.
> > - Acknowledging the existence of scenarios where inlined functions declared in
> >   header files may result in multiple copies due to compiler behavior, though
> >    it is not actionable as it does not pose an operational issue.
> > - Highlighting a single exception where the same name refers to different
> >   functions: the case of "compat_binfmt_elf.c," which directly includes
> >   "binfmt_elf.c" producing identical function copies in two separate
> >   modules.
>
> Oh, I thought you managed to handle this in v3 since you didn't reply in
> the previous thread...
I want to thank you for this observation because it gives me the chance to
discuss this topic.

It is evident that the corner case in question is inherently challenging
to address using the addr2line approach. Attempting to conceal this
limitation would be counterproductive.

compat_binfmt_elf.c includes directly binfmt_elf.c, addr2line can't help
but report all functions and data declared in that file, coming from that
file. compat_binfmt_elf.c is just a bunch of macro definitions that
rename a few symbols and define some items used in macro-defined
compilation in binfmt_elf.c.

Looking at the functions, only two of the functions defined by
compat_binfmt_elf.c are binary different from their counterpart in
binfmt_elf.c.
These differences, while present, are indeed minimal, but this fact not
relevant to this discussion.

My position is that, rather than producing a more complicated pipeline
to handle this corner case, it is better to fix it. Before reading your
message, I was about to send the v4, but now I'd prefer to hear the
others' opinions on this matter before taking any future action.


>
> >
> > sample from new v3
> >
> >  ~ # cat /proc/kallsyms | grep gic_mask_irq
> >  ffffd0b03c04dae4 t gic_mask_irq
> >  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
> >  ffffd0b03c050960 t gic_mask_irq
> >  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
>
> BTW, why normalize them? Why not just
>
> gic_mask_irq@drivers/irqchip/...
>
> Aaaaand why line number? Line numbers break reproducible builds and also
> would make it harder to refer to a particular symbol by its path and
> name since we also have to pass its line number which may change once
> you add a debug print there, for example.
> OTOH there can't be 2 symbols with the same name within one file, so
> just path + name would be enough. Or not?

Regarding the use of full file paths and line numbers for symbol decoration,
it indeed provides the highest level of uniqueness for each symbol.
However, I understand your point that this level of detail might be more than
necessary.

This approach was implemented in response to a specific request expressed in
the live-patching list, and I wanted to ensure we met those requirements.
I am open to revisiting this aspect, and I am willing to accommodate changes
based on feedback.

If you believe that simplifying the format to just path + name would be more
practical, or if you think that eliminating line numbers is a better choice
to avoid potential issues while debugging builds, I'm open to considering
these adjustments.
Additionally, I've interpreted and implemented Francis's suggestion as making
the separator a configurable option, but maybe a proper format string here,
would be more appropriate.


>
> (sorry if some of this was already discussed previously)
>
> [...]
>
> Thanks,
> Olek

Thank you,
Alessandro

^ permalink raw reply	[flat|nested] 16+ messages in thread

* Re: [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms
  2023-09-12 14:18   ` Alessandro Carminati
@ 2023-09-13  8:06     ` Petr Mladek
  0 siblings, 0 replies; 16+ messages in thread
From: Petr Mladek @ 2023-09-13  8:06 UTC (permalink / raw)
  To: Alessandro Carminati
  Cc: Alexander Lobakin, Masami Hiramatsu, Steven Rostedt,
	Daniel Bristot de Oliveira, Josh Poimboeuf, Masahiro Yamada,
	Luis Chamberlain, Nathan Chancellor, Nick Desaulniers,
	Nicolas Schier, Nick Alcock, Kris Van Hees, Eugene Loh,
	Francis Laniel, Viktor Malik, linux-kbuild, linux-kernel,
	linux-trace-kernel, live-patching

On Tue 2023-09-12 16:18:00, Alessandro Carminati wrote:
> <aleksander.lobakin@intel.com> ha scritto:
> > From: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> > > sample from new v3
> > >
> > >  ~ # cat /proc/kallsyms | grep gic_mask_irq
> > >  ffffd0b03c04dae4 t gic_mask_irq
> > >  ffffd0b03c04dae4 t gic_mask_irq@_drivers_irqchip_irq-gic_c_167
> > >  ffffd0b03c050960 t gic_mask_irq
> > >  ffffd0b03c050960 t gic_mask_irq@_drivers_irqchip_irq-gic-v3_c_404
> >
> > BTW, why normalize them? Why not just
> >
> > gic_mask_irq@drivers/irqchip/...
> >
> > Aaaaand why line number? Line numbers break reproducible builds and also
> > would make it harder to refer to a particular symbol by its path and
> > name since we also have to pass its line number which may change once
> > you add a debug print there, for example.
> > OTOH there can't be 2 symbols with the same name within one file, so
> > just path + name would be enough. Or not?

I am afraid that there can be more symbols with the same name in a
single source file. For example, static variables defined inside
functions:

$> cat >test-duplicate-symbols.c <<EOT
#include <stdio.h>

void a(void)
{
	static int duplicate_var = 100;

	printf("%s: %d\n", __func__, duplicate_var);
}

void b(void)
{
	static int duplicate_var = 200;

	printf("%s: %d\n", __func__, duplicate_var);
}

int main(int argc, char *argv)
{
	a();
	b();
}
EOT

$> gcc -o test-duplicate-symbols test-duplicate-symbols.c

$> ./test-duplicate-symbols 
a: 100
b: 200

$> objdump -t test-duplicate-symbols | grep duplicate
test-duplicate-symbols:     file format elf64-x86-64
0000000000000000 l    df *ABS*  0000000000000000              test-duplicate-symbols.c
0000000000402018 l     O .data  0000000000000004              duplicate_var.2190
000000000040201c l     O .data  0000000000000004              duplicate_var.2195


> Regarding the use of full file paths and line numbers for symbol decoration,
> it indeed provides the highest level of uniqueness for each symbol.
> However, I understand your point that this level of detail might be more than
> necessary.
> 
> This approach was implemented in response to a specific request expressed in
> the live-patching list, and I wanted to ensure we met those requirements.
> I am open to revisiting this aspect, and I am willing to accommodate changes
> based on feedback.

Yeah, livepatching needs to be able to find any symbol which might
need to be accessed from the livepatch.

The line number is perfectly fine for livepatching because there
is 1:1:1 relationship between the kernel sources, binary, and
livepatch.

And it might be even useful for the tracing. It helps to find
and investigate the traced code easily.

Hmm, I understand that it complicates the live for the trace
tooling. I wonder if we could allow searching the symbols
with a pattern, e.g. the bash style
"duplicated_symbol_name-source_file_c*"


> If you believe that simplifying the format to just path + name would be more
> practical, or if you think that eliminating line numbers is a better choice
> to avoid potential issues while debugging builds, I'm open to considering
> these adjustments.
> Additionally, I've interpreted and implemented Francis's suggestion as making
> the separator a configurable option, but maybe a proper format string here,
> would be more appropriate.

Please, do not make the format configurable. I think that it will
cause more harm than good. It would make the life more complicated
for developing tracing tools.

The tools would need to support all the formats as well. Or they
would support only some and will not be able to trace kernels
with the others. Both is bad.

Anyway, thanks a lot for working on this.

Best Regards,
Petr

^ permalink raw reply	[flat|nested] 16+ messages in thread

end of thread, other threads:[~2023-09-13  8:06 UTC | newest]

Thread overview: 16+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-08-28  8:04 [PATCH v3] scripts/link-vmlinux.sh: Add alias to duplicate symbols for kallsyms Alessandro Carminati (Red Hat)
2023-08-29 14:51 ` Francis Laniel
2023-09-02  7:26   ` Alessandro Carminati
2023-08-30  6:00 ` Masami Hiramatsu
2023-09-02  7:26   ` Alessandro Carminati
2023-09-03 14:50     ` Masami Hiramatsu
2023-09-01  5:31 ` Masahiro Yamada
2023-09-02  7:27   ` Alessandro Carminati
2023-09-02  6:36 ` Masahiro Yamada
2023-09-02  7:40   ` Alessandro Carminati
2023-09-04 13:09     ` Francis Laniel
2023-09-06 10:09   ` Alessandro Carminati
2023-09-06 15:06     ` Masahiro Yamada
2023-09-11 14:21 ` Alexander Lobakin
2023-09-12 14:18   ` Alessandro Carminati
2023-09-13  8:06     ` Petr Mladek

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