From: "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>
To: rostedt@goodmis.org
Cc: linux-trace-devel@vger.kernel.org
Subject: [PATCH v2 1/2] trace-cmd: [POC] Add APIs for extracting DWARF information from a file
Date: Thu, 18 Jun 2020 11:53:32 +0300 [thread overview]
Message-ID: <20200618085333.164150-2-tz.stoyanov@gmail.com> (raw)
In-Reply-To: <20200618085333.164150-1-tz.stoyanov@gmail.com>
Added initial infrastructure and trace-cmd library APIs for working with
DWARF debug information:
trace_obj_debug_create()
trace_obj_debug_destroy()
trace_obj_debug_get_fileoffset()
These internal APIs utilize libdwarf and libbfd for parsing ELF and
DWARF headers of the files. The trace_obj_debug_get_fileoffset()
API retrieves the offset in the file of the given functions. These
offsets can be used to set a uprobes to the functions.
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
Makefile | 12 +
lib/trace-cmd/Makefile | 17 ++
lib/trace-cmd/include/trace-cmd-local.h | 13 +
lib/trace-cmd/trace-obj-debug.c | 348 ++++++++++++++++++++++++
4 files changed, 390 insertions(+)
create mode 100644 lib/trace-cmd/trace-obj-debug.c
diff --git a/Makefile b/Makefile
index 2f9620e4..d737b588 100644
--- a/Makefile
+++ b/Makefile
@@ -243,6 +243,18 @@ endif
CUNIT_INSTALLED := $(shell if (echo -e "\#include <CUnit/Basic.h>\n void main(){CU_initialize_registry();}" | $(CC) -x c -lcunit - >/dev/null 2>&1) ; then echo 1; else echo 0 ; fi)
export CUNIT_INSTALLED
+DWARF_INSTALLED := $(shell if (echo -e "\#include <libdwarf/libdwarf.h>\n void main(){dwarf_init(-1, 0, 0, 0, 0, 0);}" | $(CC) -xc - -ldwarf >/dev/null 2>&1) ; then echo 1; else echo 0 ; fi)
+export DWARF_INSTALLED
+BFD_INSTALLED := $(shell if (echo -e "\#include <bfd.h>\n void main(){bfd_init();}" | $(CC) -xc - -lbfd >/dev/null 2>&1) ; then echo 1; else echo 0 ; fi)
+export BFD_INSTALLED
+
+ifeq ($(BFD_INSTALLED), 1)
+LIBS += -lbfd
+endif
+ifeq ($(DWARF_INSTALLED), 1)
+LIBS += -ldwarf
+endif
+
export CFLAGS
export INCLUDES
diff --git a/lib/trace-cmd/Makefile b/lib/trace-cmd/Makefile
index 666a1ebf..f8fb8390 100644
--- a/lib/trace-cmd/Makefile
+++ b/lib/trace-cmd/Makefile
@@ -24,6 +24,16 @@ endif
OBJS += trace-blk-hack.o
OBJS += trace-ftrace.o
+ifeq ($(BFD_INSTALLED), 1)
+ifeq ($(DWARF_INSTALLED), 1)
+OBJS += trace-obj-debug.o
+else
+$(warning libdwarf is not installed)
+endif
+else
+$(warning libbfd is not installed)
+endif
+
OBJS := $(OBJS:%.o=$(bdir)/%.o)
DEPS := $(OBJS:$(bdir)/%.o=$(bdir)/.%.d)
@@ -40,6 +50,13 @@ $(bdir)/libtracecmd.a: $(OBJS)
LIBS = -L$(obj)/lib/traceevent -ltraceevent
+ifeq ($(BFD_INSTALLED), 1)
+LIBS += -lbfd
+endif
+ifeq ($(DWARF_INSTALLED), 1)
+LIBS += -ldwarf
+endif
+
$(bdir)/libtracecmd.so: $(OBJS)
$(Q)$(call do_compile_shared_library)
diff --git a/lib/trace-cmd/include/trace-cmd-local.h b/lib/trace-cmd/include/trace-cmd-local.h
index 95dce66c..d4b31393 100644
--- a/lib/trace-cmd/include/trace-cmd-local.h
+++ b/lib/trace-cmd/include/trace-cmd-local.h
@@ -26,5 +26,18 @@ void warning(const char *fmt, ...);
#endif
#endif
+struct trace_obj_debug;
+struct trace_obj_symbols {
+ struct trace_obj_symbols *next;
+ char *name; /* symbol name */
+ unsigned long long vma; /* symbol virtual memory address */
+ unsigned long long foffset; /* symbol file offset */
+};
+
+struct trace_obj_debug *trace_obj_debug_create(char *file);
+void trace_obj_debug_destroy(struct trace_obj_debug *obj);
+int trace_obj_debug_get_fileoffset(struct trace_obj_debug *obj,
+ struct trace_obj_symbols *symbols);
+
#endif /* _TRACE_CMD_LOCAL_H */
diff --git a/lib/trace-cmd/trace-obj-debug.c b/lib/trace-cmd/trace-obj-debug.c
new file mode 100644
index 00000000..80d626c8
--- /dev/null
+++ b/lib/trace-cmd/trace-obj-debug.c
@@ -0,0 +1,348 @@
+// SPDX-License-Identifier: LGPL-2.1
+/*
+ * Copyright (C) 2020, VMware, Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
+ *
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <dwarf.h>
+#include <libdwarf/libdwarf.h>
+#include <bfd.h>
+#include "trace-cmd-local.h"
+#include "trace-cmd.h"
+
+struct trace_obj_debug {
+ Dwarf_Debug dwarf;
+ bfd *bfd;
+};
+
+static void dwarf_error_handler(Dwarf_Error error, Dwarf_Ptr errarg)
+{
+ warning("\nlibdwarf error detected: 0x%" DW_PR_DUx " %s\n",
+ dwarf_errno(error), dwarf_errmsg(error));
+}
+
+static int get_addr(Dwarf_Attribute attr, Dwarf_Addr *val)
+{
+ Dwarf_Error error = 0;
+ Dwarf_Addr uval = 0;
+ int res;
+
+ res = dwarf_formaddr(attr, &uval, &error);
+ if (res != DW_DLV_OK)
+ return -1;
+
+ *val = uval;
+ return 0;
+}
+
+static int dwarf_get_subprog(Dwarf_Debug dbg, Dwarf_Die die,
+ struct trace_obj_symbols *data, const char *name)
+{
+ Dwarf_Attribute *attrbuf = 0;
+ Dwarf_Signed attrcount = 0;
+ Dwarf_Error error = 0;
+ Dwarf_Addr lowpc = 0;
+ Dwarf_Half aform;
+ Dwarf_Signed i;
+ int res;
+
+ res = dwarf_attrlist(die, &attrbuf, &attrcount, &error);
+ if (res != DW_DLV_OK)
+ return -1;
+ for (i = 0; i < attrcount ; ++i) {
+ res = dwarf_whatattr(attrbuf[i], &aform, &error);
+ if (res == DW_DLV_OK) {
+ if (aform == DW_AT_low_pc)
+ get_addr(attrbuf[i], &lowpc);
+ }
+ dwarf_dealloc(dbg, attrbuf[i], DW_DLA_ATTR);
+ if (lowpc)
+ break;
+ }
+
+ while (data) {
+ if (lowpc && !strcmp(name, data->name) && !data->vma)
+ data->vma = lowpc;
+ data = data->next;
+ }
+
+ dwarf_dealloc(dbg, attrbuf, DW_DLA_LIST);
+
+ return 0;
+}
+
+
+static int dwarf_get_die_data(Dwarf_Debug dbg, Dwarf_Die die,
+ struct trace_obj_symbols *data)
+{
+ const char *formname = 0;
+ Dwarf_Attribute attr = 0;
+ const char *tagname = 0;
+ Dwarf_Half formnum = 0;
+ Dwarf_Error error = 0;
+ Dwarf_Half tag = 0;
+ char *name = NULL;
+ int res = 0;
+
+ res = dwarf_diename(die, &name, &error);
+ if (res == DW_DLV_ERROR) {
+ warning("Error in dwarf_diename: %s\n", dwarf_errmsg(error));
+ return -1;
+ }
+ if (res == DW_DLV_NO_ENTRY)
+ name = "<no DW_AT_name attr>";
+
+ res = dwarf_tag(die, &tag, &error);
+ if (res != DW_DLV_OK) {
+ warning("Error in dwarf_tag: %s n", dwarf_errmsg(error));
+ return -1;
+ }
+ res = dwarf_get_TAG_name(tag, &tagname);
+ if (res != DW_DLV_OK) {
+ warning("Error in dwarf_get_TAG_name: %s\n", dwarf_errmsg(error));
+ return -1;
+ }
+
+ res = dwarf_attr(die, DW_AT_name, &attr, &error);
+ if (res == DW_DLV_OK) {
+ res = dwarf_whatform(attr, &formnum, &error);
+ if (res != DW_DLV_OK) {
+ warning("Error in dwarf_whatform: %s\n",
+ dwarf_errmsg(error));
+ return -1;
+ }
+ formname = "form-name-unavailable";
+ res = dwarf_get_FORM_name(formnum, &formname);
+ if (res != DW_DLV_OK)
+ formname = "UNKNoWn FORM!";
+ dwarf_dealloc(dbg, attr, DW_DLA_ATTR);
+ }
+
+ if (tag == DW_TAG_subprogram)
+ dwarf_get_subprog(dbg, die, data, name);
+
+ return 0;
+}
+
+static void dwarf_get_die_and_siblings(Dwarf_Debug dbg, Dwarf_Die in_die,
+ struct trace_obj_symbols *data)
+{
+ Dwarf_Die cur_die = in_die;
+ int res = DW_DLV_ERROR;
+ Dwarf_Error error = 0;
+ Dwarf_Die child = 0;
+ Dwarf_Die sib_die;
+
+ dwarf_get_die_data(dbg, in_die, data);
+ for (;;) {
+ sib_die = 0;
+ res = dwarf_child(cur_die, &child, &error);
+ if (res == DW_DLV_ERROR) {
+ warning("Error in dwarf_child: %s\n", dwarf_errmsg(error));
+ return;
+ }
+ if (res == DW_DLV_OK) {
+ dwarf_get_die_and_siblings(dbg, child, data);
+ /* No longer need 'child' die. */
+ dwarf_dealloc(dbg, child, DW_DLA_DIE);
+ child = 0;
+ }
+ /* res == DW_DLV_NO_ENTRY or DW_DLV_OK */
+ res = dwarf_siblingof_b(dbg, cur_die, 1, &sib_die, &error);
+ if (res == DW_DLV_ERROR) {
+ warning("Error in dwarf_siblingof_b :%s\n",
+ dwarf_errmsg(error));
+ return;
+ }
+ if (res == DW_DLV_NO_ENTRY)
+ break; /* Done at this level. */
+
+ if (cur_die != in_die) {
+ dwarf_dealloc(dbg, cur_die, DW_DLA_DIE);
+ cur_die = 0;
+ }
+ cur_die = sib_die;
+ dwarf_get_die_data(dbg, cur_die, data);
+ }
+}
+
+static int dwarf_read_all(Dwarf_Debug dwarf, struct trace_obj_symbols *data)
+{
+ Dwarf_Half header_cu_type = DW_UT_compile;
+ Dwarf_Unsigned cu_header_length = 0;
+ Dwarf_Unsigned next_cu_header = 0;
+ Dwarf_Unsigned abbrev_offset = 0;
+ Dwarf_Unsigned typeoffset = 0;
+ Dwarf_Half extension_size = 0;
+ Dwarf_Half version_stamp = 0;
+ Dwarf_Half address_size = 0;
+ Dwarf_Half offset_size = 0;
+ Dwarf_Sig8 signature;
+ Dwarf_Die no_die = 0;
+ Dwarf_Die cu_die = 0;
+ Dwarf_Error error;
+ Dwarf_Sig8 sig;
+ int number = 0;
+ int res;
+
+ for (;; ++number) {
+ no_die = 0;
+ cu_die = 0;
+ memset(&sig, 0, sizeof(sig));
+
+ res = dwarf_next_cu_header_d(dwarf, 1, &cu_header_length,
+ &version_stamp, &abbrev_offset,
+ &address_size, &offset_size,
+ &extension_size, &signature,
+ &typeoffset, &next_cu_header,
+ &header_cu_type, &error);
+ if (res == DW_DLV_ERROR) {
+ warning("Error in dwarf_next_cu_header: %s\n",
+ dwarf_errmsg(error));
+ goto out_error;
+ }
+ if (res == DW_DLV_NO_ENTRY)
+ break;
+
+ res = dwarf_siblingof_b(dwarf, no_die, 1, &cu_die, &error);
+ if (res == DW_DLV_ERROR) {
+ warning("Error in dwarf_siblingof_b on CU die: %s\n",
+ dwarf_errmsg(error));
+ goto out_error;
+ }
+ if (res == DW_DLV_NO_ENTRY) {
+ warning("no entry! in dwarf_siblingof on CU die\n");
+ goto out_error;
+ }
+ dwarf_get_die_and_siblings(dwarf, cu_die, data);
+ dwarf_dealloc(dwarf, cu_die, DW_DLA_DIE);
+ }
+ return 0;
+
+out_error:
+ return -1;
+}
+
+static void bfd_dwarf_section(bfd *abfd, asection *section, void *param)
+{
+ struct trace_obj_symbols *data = (struct trace_obj_symbols *)param;
+
+ while (data) {
+ if ((section->flags & SEC_CODE) && section->vma <= data->vma &&
+ (section->vma + section->size) > data->vma)
+ data->foffset = section->filepos + (data->vma - section->vma);
+
+ data = data->next;
+ }
+}
+
+static int bfd_process_object(bfd *abfd, struct trace_obj_symbols *data)
+{
+ int ret = 0;
+
+ if (bfd_check_format_matches(abfd, bfd_object, NULL) ||
+ bfd_check_format_matches(abfd, bfd_core, NULL))
+ bfd_map_over_sections(abfd, bfd_dwarf_section, data);
+ else
+ ret = -1;
+
+ return ret;
+}
+
+static int bfd_read_all(bfd *handle, struct trace_obj_symbols *data)
+{
+ bfd *last_arfile = NULL;
+ bfd *arfile = NULL;
+ int ret = 0;
+
+ if (bfd_check_format(handle, bfd_archive)) {
+ for (;;) {
+ bfd_set_error(bfd_error_no_error);
+ arfile = bfd_openr_next_archived_file(handle, arfile);
+ if (arfile == NULL) {
+ if (bfd_get_error() != bfd_error_no_more_archived_files)
+ break;
+ }
+ ret = bfd_read_all(arfile, data);
+ if (last_arfile != NULL)
+ bfd_close(last_arfile);
+ last_arfile = arfile;
+ }
+ if (last_arfile != NULL)
+ bfd_close(last_arfile);
+ } else
+ ret = bfd_process_object(handle, data);
+
+ return ret;
+}
+
+/**
+ * trace_obj_debug_get_fileoffset - Get symbols VMA and file offset
+ * @obj - pointer to object, returned by trace_obj_debug_create()
+ * @symbols - link list with desired symbols
+ *
+ * Get VMA and file offset of the given symbols, using file debug information
+ * Return 0 on success, -1 on error
+ */
+int trace_obj_debug_get_fileoffset(struct trace_obj_debug *obj,
+ struct trace_obj_symbols *symbols)
+{
+ int ret;
+
+ ret = dwarf_read_all(obj->dwarf, symbols);
+ if (!ret)
+ ret = bfd_read_all(obj->bfd, symbols);
+
+ return ret;
+}
+
+/**
+ * trace_symbols_destroy - Close file opened with trace_obj_debug_create()
+ * @obj - pointer to object, returned by trace_obj_debug_create()
+ *
+ * Close the file and free any allocated resources, related to file's debug
+ * information
+ */
+void trace_obj_debug_destroy(struct trace_obj_debug *obj)
+{
+ if (obj && obj->dwarf)
+ dwarf_finish(obj->dwarf, NULL);
+ if (obj && obj->bfd)
+ bfd_close(obj->bfd);
+ free(obj);
+}
+
+/**
+ * trace_obj_debug_create - Open binary file for parsing ELF and DWARF information
+ * @name: Name of the binary ELF file.
+ *
+ * Return pointer to trace_obj_debug structure, that can be passed to other APIs
+ * for extracting debug information from the file. NULL in case of an error.
+ */
+struct trace_obj_debug *trace_obj_debug_create(char *file)
+{
+ struct trace_obj_debug *obj = NULL;
+ Dwarf_Error dw_error;
+ int res;
+
+ obj = calloc(1, sizeof(*obj));
+ if (!obj)
+ return NULL;
+
+ res = dwarf_init_path(file, NULL, 0, DW_DLC_READ, DW_GROUPNUMBER_ANY,
+ dwarf_error_handler, NULL, &obj->dwarf,
+ 0, 0, 0, &dw_error);
+ if (res != DW_DLV_OK)
+ goto error;
+ bfd_init();
+ obj->bfd = bfd_openr(file, NULL);
+ if (!obj->bfd)
+ goto error;
+ return obj;
+
+error:
+ trace_obj_debug_destroy(obj);
+ return NULL;
+}
--
2.26.2
next prev parent reply other threads:[~2020-06-18 8:53 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-18 8:53 [PATCH v2 0/2] POC] Add support for uprobes Tzvetomir Stoyanov (VMware)
2020-06-18 8:53 ` Tzvetomir Stoyanov (VMware) [this message]
2020-06-18 8:53 ` [PATCH v2 2/2] trace-cmd: [POC] " Tzvetomir Stoyanov (VMware)
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