[PATCH 06/13 v2] libtracefs: Add checking of available_filter_functions to tracefs_function_filter()

[Steven Rostedt <rostedt@goodmis.org>]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Instead of modifying the set_ftrace_filter file with a filter that
possibly does not match anything, check the available_filter_functions
file first to make sure that each filter will match something. Then if
"reset" is enabled, it wont clear the filter file and not set any
filtering, which could cause issues if the application is not expecting
all functions to be enabled.

Link: https://lore.kernel.org/linux-trace-devel/20210323013225.156539389@goodmis.org

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 src/tracefs-tools.c | 183 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 178 insertions(+), 5 deletions(-)

diff --git a/src/tracefs-tools.c b/src/tracefs-tools.c
index 1348542a3419..db12f759be1b 100644
--- a/src/tracefs-tools.c
+++ b/src/tracefs-tools.c
@@ -10,6 +10,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <sys/types.h>
+#include <regex.h>
 #include <dirent.h>
 #include <limits.h>
 #include <errno.h>
@@ -416,6 +417,112 @@ static void add_errors(const char ***errs, const char *filter, int ret)
 	*errs = e;
 }
 
+struct func_filter {
+	const char		*filter;
+	regex_t			re;
+	bool			set;
+};
+
+/*
+ * Convert a glob into a regular expression.
+ */
+static char *make_regex(const char *glob)
+{
+	char *str;
+	int cnt = 0;
+	int i, j;
+
+	for (i = 0; glob[i]; i++) {
+		if (glob[i] == '*'|| glob[i] == '.')
+			cnt++;
+	}
+
+	/* '^' + ('*'->'.*' or '.' -> '\.') + '$' + '\0' */
+	str = malloc(i + cnt + 3);
+	if (!str)
+		return NULL;
+
+	str[0] = '^';
+	for (i = 0, j = 1; glob[i]; i++, j++) {
+		if (glob[i] == '*')
+			str[j++] = '.';
+		/* Dots can be part of a function name */
+		if (glob[i] == '.')
+			str[j++] = '\\';
+		str[j] = glob[i];
+	}
+	str[j++] = '$';
+	str[j] = '\0';
+	return str;
+}
+
+static bool match(const char *str, struct func_filter *func_filter)
+{
+	return regexec(&func_filter->re, str, 0, NULL, 0) == 0;
+}
+
+static int check_available_filters(struct func_filter *func_filters,
+				   const char *module, const char ***errs)
+{
+	char *line = NULL;
+	size_t size = 0;
+	char *path;
+	FILE *fp;
+	int ret = 1;
+	int mlen;
+	int i;
+
+	path = tracefs_get_tracing_file("available_filter_functions");
+	if (!path)
+		return 1;
+
+	fp = fopen(path, "r");
+	tracefs_put_tracing_file(path);
+
+	if (!fp)
+		return 1;
+
+	if (module)
+		mlen = strlen(module);
+
+	while (getline(&line, &size, fp) >= 0) {
+		char *saveptr = NULL;
+		char *tok, *mtok;
+		int len = strlen(line);
+
+		if (line[len - 1] == '\n')
+			line[len - 1] = '\0';
+		tok = strtok_r(line, " ", &saveptr);
+		if (!tok)
+			goto next;
+		if (module) {
+			mtok = strtok_r(NULL, " ", &saveptr);
+			if (!mtok)
+				goto next;
+			if ((strncmp(mtok + 1, module, mlen) != 0) ||
+			    (mtok[mlen + 1] != ']'))
+				goto next;
+		}
+		for (i = 0; func_filters[i].filter; i++) {
+			if (match(tok, &func_filters[i]))
+				func_filters[i].set = true;
+		}
+	next:
+		free(line);
+		line = NULL;
+		len = 0;
+	}
+	fclose(fp);
+
+	ret = 0;
+	for (i = 0; func_filters[i].filter; i++) {
+		if (!func_filters[i].set)
+			add_errors(errs, func_filters[i].filter, ret--);
+	}
+
+	return ret;
+}
+
 static int controlled_write(int fd, const char **filters,
 			    const char *module, const char ***errs)
 {
@@ -447,6 +554,62 @@ static int controlled_write(int fd, const char **filters,
 	return ret;
 }
 
+static int init_func_filter(struct func_filter *func_filter, const char *filter)
+{
+	char *str;
+	int ret;
+
+	str = make_regex(filter);
+	if (!str)
+		return -1;
+
+	ret = regcomp(&func_filter->re, str, REG_ICASE|REG_NOSUB);
+	free(str);
+
+	if (ret < 0)
+		return -1;
+
+	func_filter->filter = filter;
+	return 0;
+}
+
+static void free_func_filters(struct func_filter *func_filters)
+{
+	int i;
+
+	if (!func_filters)
+		return;
+
+	for (i = 0; func_filters[i].filter; i++) {
+		regfree(&func_filters[i].re);
+	}
+}
+
+static struct func_filter *make_func_filters(const char **filters)
+{
+	struct func_filter *func_filters = NULL;
+	int i;
+
+	for (i = 0; filters[i]; i++)
+		;
+
+	if (!i)
+		return NULL;
+
+	func_filters = calloc(i + 1, sizeof(*func_filters));
+	if (!func_filters)
+		return NULL;
+
+	for (i = 0; filters[i]; i++) {
+		if (init_func_filter(&func_filters[i], filters[i]) < 0)
+			goto out_err;
+	}
+	return func_filters;
+ out_err:
+	free_func_filters(func_filters);
+	return NULL;
+}
+
 /**
  * tracefs_function_filter - write to set_ftrace_filter file to trace
  * particular functions
@@ -478,14 +641,28 @@ static int controlled_write(int fd, const char **filters,
 int tracefs_function_filter(struct tracefs_instance *instance, const char **filters,
 			    const char *module, bool reset, const char ***errs)
 {
+	struct func_filter *func_filters;
 	char *ftrace_filter_path;
-	int ret = 0;
 	int flags;
+	int ret;
 	int fd;
 
 	if (!filters)
 		return 1;
 
+	func_filters = make_func_filters(filters);
+	if (!func_filters)
+		return 1;
+
+	/* Make sure errs is NULL to start with, realloc() depends on it. */
+	if (errs)
+		*errs = NULL;
+
+	ret = check_available_filters(func_filters, module, errs);
+	free_func_filters(func_filters);
+	if (ret)
+		return ret;
+
 	ftrace_filter_path = tracefs_instance_get_file(instance, TRACE_FILTER);
 	if (!ftrace_filter_path)
 		return 1;
@@ -497,10 +674,6 @@ int tracefs_function_filter(struct tracefs_instance *instance, const char **filt
 	if (fd < 0)
 		return 1;
 
-	/* Make sure errs is NULL to start with, realloc() depends on it. */
-	if (errs)
-		*errs = NULL;
-
 	ret = controlled_write(fd, filters, module, errs);
 
 	close(fd);
-- 
2.30.1