[v2,4/5] libtracefs: Add tracefs_function_notrace() API

Commit Message

Steven Rostedt April 8, 2021, 1:34 p.m. UTC

From: "Steven Rostedt (VMware)" <[e-mail]>

Add the API of tracefs_function_notrace() that is identical to how
tracefs_function_filter() works, but will work with the set_ftrace_notrace
filter file.

Signed-off-by: Steven Rostedt (VMware) <[e-mail]>
---
Changes since v1:
 - Close the descriptor when the instance is freed.

 Documentation/libtracefs-function-filter.txt | 19 ++++++++---
 include/tracefs-local.h                      |  1 +
 include/tracefs.h                            |  3 ++
 src/tracefs-instance.c                       |  4 +++
 src/tracefs-tools.c                          | 33 ++++++++++++++++++++
 5 files changed, 56 insertions(+), 4 deletions(-)

Patch

diff --git a/Documentation/libtracefs-function-filter.txt b/Documentation/libtracefs-function-filter.txt
index ccf20e9..746be37 100644
--- a/Documentation/libtracefs-function-filter.txt
+++ b/Documentation/libtracefs-function-filter.txt
@@ -4,6 +4,7 @@  libtracefs(3)
 NAME
 ----
 tracefs_function_filter - Function to limit kernel functions that are traced
+tracefs_function_notrace - Function to filter kernel functions that not to be traced
 
 SYNOPSIS
 --------
@@ -12,15 +13,18 @@  SYNOPSIS
 *#include <tracefs.h>*
 
 int *tracefs_function_filter*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_filter_, const char pass:[*]_module_, int _flags_);
+int *tracefs_function_notrace*(struct tracefs_instance pass:[*]_instance_, const char pass:[*]_filter_, const char pass:[*]_module_, int _flags_);
 --
 
 DESCRIPTION
 -----------
-This function can be used to limit the Linux kernel functions that would be
-traced by the function and function-graph tracers
+*tracefs_function_filter* and *tracefs_function_notrace* can be used to limit the
+Linux kernel functions that would be traced by the function and function-graph tracers.
+The *tracefs_function_filter* defines a list of functions that can be traced.
+The *tracefs_function_notrace* defines a list of functions that will not be traced.
+If a function is in both lists, it will not be traced.
 
-It will take an
-_instance_ , that can be NULL for the top level tracing,
+They take an _instance_ , that can be NULL for the top level tracing,
 _filter_, a string that represents a filter that should
 be applied to define what functions are to be traced,
 _module_, to limit the filtering on a specific module (or NULL to filter on all functions),
@@ -125,6 +129,13 @@  int main(int argc, char *argv[])
 		/* Error creating new trace instance */
 	}
 
+	/* Do not trace any function with the word "lock" in it */
+	ret = tracefs_function_notrace(inst, "*lock*", NULL, TRACEFS_FL_RESET);
+	if (ret) {
+		printf("Failed to set the notrace filter\n");
+		goto out;
+	}
+
 	/* First reset the filter */
 	ret = tracefs_function_filter(inst, NULL, NULL,
 				      TRACEFS_FL_RESET | TRACEFS_FL_CONTINUE);
diff --git a/include/tracefs-local.h b/include/tracefs-local.h
index 73ec113..060de7e 100644
--- a/include/tracefs-local.h
+++ b/include/tracefs-local.h
@@ -19,6 +19,7 @@  struct tracefs_instance {
 	char	*name;
 	int	flags;
 	int	ftrace_filter_fd;
+	int	ftrace_notrace_fd;
 };
 
 /* Can be overridden */
diff --git a/include/tracefs.h b/include/tracefs.h
index befcc48..70b7ebe 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -160,4 +160,7 @@  enum {
 
 int tracefs_function_filter(struct tracefs_instance *instance, const char *filter,
 			    const char *module, unsigned int flags);
+int tracefs_function_notrace(struct tracefs_instance *instance, const char *filter,
+			     const char *module, unsigned int flags);
+
 #endif /* _TRACE_FS_H */
diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
index e222191..6ccf7d8 100644
--- a/src/tracefs-instance.c
+++ b/src/tracefs-instance.c
@@ -44,6 +44,7 @@  static struct tracefs_instance *instance_alloc(const char *trace_dir, const char
 	}
 
 	instance->ftrace_filter_fd = -1;
+	instance->ftrace_notrace_fd = -1;
 
 	return instance;
 
@@ -70,6 +71,9 @@  void tracefs_instance_free(struct tracefs_instance *instance)
 	if (instance->ftrace_filter_fd >= 0)
 		close(instance->ftrace_filter_fd);
 
+	if (instance->ftrace_notrace_fd >= 0)
+		close(instance->ftrace_notrace_fd);
+
 	free(instance->trace_dir);
 	free(instance->name);
 	free(instance);
diff --git a/src/tracefs-tools.c b/src/tracefs-tools.c
index 9bd9a72..0f733b4 100644
--- a/src/tracefs-tools.c
+++ b/src/tracefs-tools.c
@@ -21,10 +21,12 @@ 
 
 #define TRACE_CTRL		"tracing_on"
 #define TRACE_FILTER		"set_ftrace_filter"
+#define TRACE_NOTRACE		"set_ftrace_notrace"
 #define TRACE_FILTER_LIST	"available_filter_functions"
 
 /* File descriptor for Top level set_ftrace_filter  */
 static int ftrace_filter_fd = -1;
+static int ftrace_notrace_fd = -1;
 static pthread_mutex_t filter_lock = PTHREAD_MUTEX_INITIALIZER;
 
 static const char * const options_map[] = {
@@ -898,3 +900,34 @@  int tracefs_function_filter(struct tracefs_instance *instance, const char *filte
 	tracefs_put_tracing_file(filter_path);
 	return ret;
 }
+
+/**
+ * tracefs_function_notrace - filter the functions that are not to be traced
+ * @instance: ftrace instance, can be NULL for top tracing instance.
+ * @filter: The filter to filter what functions are not to be traced
+ * @module: Module to be traced or NULL if all functions are to be examined.
+ * @flags: flags on modifying the filter file
+ *
+ * See tracefs_function_filter, as this has the same functionality but
+ * for adding to the "notrace" filter.
+ */
+int tracefs_function_notrace(struct tracefs_instance *instance, const char *filter,
+			     const char *module, unsigned int flags)
+{
+	char *filter_path;
+	int *fd;
+	int ret;
+
+	filter_path = tracefs_instance_get_file(instance, TRACE_NOTRACE);
+	if (!filter_path)
+		return -1;
+
+	if (instance)
+		fd = &instance->ftrace_notrace_fd;
+	else
+		fd = &ftrace_notrace_fd;
+
+	ret = update_filter(filter_path, fd, instance, filter, module, flags);
+	tracefs_put_tracing_file(filter_path);
+	return ret;
+}