Usually the system's tracing directory is mounted as a subfolder in
/sys/kernel and is auto detected by the tracefs library, using the
information from the "/proc/mounts" file. But there are cases where
/sys and /proc are mounted inside a container on a custom mount point.
In those cases the tracefs library cannot auto detect the system's
tracing directory. That's why a new API is introduced, to handle these
custom use cases:
int tracefs_set_tracing_dir(char *tracing_dir);
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@xxxxxxxxx>
---
Documentation/libtracefs-files.txt | 14 ++++++++++++--
Documentation/libtracefs.txt | 1 +
include/tracefs.h | 1 +
src/tracefs-utils.c | 30 ++++++++++++++++++++++++++++++
utest/tracefs-utest.c | 20 ++++++++++++++++++++
5 files changed, 64 insertions(+), 2 deletions(-)
diff --git a/Documentation/libtracefs-files.txt b/Documentation/libtracefs-files.txt
index ab917a6..2a3f544 100644
--- a/Documentation/libtracefs-files.txt
+++ b/Documentation/libtracefs-files.txt
@@ -3,8 +3,8 @@ libtracefs(3)
NAME
----
-tracefs_get_tracing_file, tracefs_put_tracing_file, tracefs_tracing_dir, tracefs_debug_dir -
-Find locations of trace directory and files.
+tracefs_get_tracing_file, tracefs_put_tracing_file, tracefs_tracing_dir, tracefs_debug_dir, tracefs_set_tracing_dir -
+Find and set locations of trace directory and files.
SYNOPSIS
--------
@@ -16,6 +16,7 @@ char pass:[*]*tracefs_get_tracing_file*(const char pass:[*]_name_);
void *tracefs_put_tracing_file*(char pass:[*]_name_);
const char pass:[*]*tracefs_tracing_dir*(void);
const char pass:[*]*tracefs_debug_dir*(void);
+int *tracefs_set_tracing_dir*(char pass:[*]_tracing_dir_)
--
DESCRIPTION
@@ -23,6 +24,13 @@ DESCRIPTION
This set of APIs can be used to find the full path of the trace file
system mount point and trace files in it.
+The *tracefs_set_tracing_dir()* function sets a custom location of the
+system's tracing directory mount point. Usually, the library auto detects
+it using the information from the /proc/mounts file. Use this API only if the
+mount point is not standard and cannot be detected by the library. The _tracing_dir_
+argument can be NULL, in that case the custom location is deleted and the library
+auto detection logic is used.
+
The *tracefs_get_tracing_file()* function returns the full path of the
file with given _name_ in the trace file system. The function works
only with files in the tracefs main directory, it is not trace instance
@@ -46,6 +54,8 @@ be freed.
RETURN VALUE
------------
+The *tracefs_set_tracing_dir()* function returns 0 on success, -1 otherwise.
+
The *tracefs_get_tracing_file()* function returns a string or NULL in case
of an error. The returned string must be freed with *tracefs_put_tracing_file()*.
diff --git a/Documentation/libtracefs.txt b/Documentation/libtracefs.txt
index 82cb574..eb2eff4 100644
--- a/Documentation/libtracefs.txt
+++ b/Documentation/libtracefs.txt
@@ -15,6 +15,7 @@ Locations of tracing files and directories:
char pass:[*]*tracefs_get_tracing_file*(const char pass:[*]_name_);
void *tracefs_put_tracing_file*(char pass:[*]_name_);
const char pass:[*]*tracefs_tracing_dir*(void);
+ int *tracefs_set_tracing_dir*(char pass:[*]_tracing_dir_)
Trace instances:
struct tracefs_instance pass:[*]*tracefs_instance_create*(const char pass:[*]_name_);
diff --git a/include/tracefs.h b/include/tracefs.h
index 693860d..fd2240a 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -16,6 +16,7 @@ void tracefs_put_tracing_file(char *name);
/* the returned string must *not* be freed */
const char *tracefs_tracing_dir(void);
const char *tracefs_debug_dir(void);
+int tracefs_set_tracing_dir(char *tracing_dir);
/* ftrace instances */
struct tracefs_instance;
diff --git a/src/tracefs-utils.c b/src/tracefs-utils.c
index 22f82af..55a2f0a 100644
--- a/src/tracefs-utils.c
+++ b/src/tracefs-utils.c
@@ -29,6 +29,7 @@
#define STR(x) _STR(x)
static int log_level = TEP_LOG_CRITICAL;
+static char *custom_tracing_dir;
/**
* tracefs_set_loglevel - set log level of the library
@@ -164,6 +165,32 @@ __hidden char *trace_find_tracing_dir(bool debugfs)
return tracing_dir;
}
+/**
+ * tracefs_set_tracing_dir - Set location of the tracing directory
+ * @tracing_dir: full path to the system's tracing directory mount point.
+ *
+ * Set the location to the system's tracing directory. This API should be used
+ * to set a custom location of the tracing directory. There is no need to call
+ * it if the location is standard, in that case the library will auto detect it.
+ *
+ * Returns 0 on success, -1 otherwise.
+ */
+int tracefs_set_tracing_dir(char *tracing_dir)
+{
+ if (custom_tracing_dir) {
+ free(custom_tracing_dir);
+ custom_tracing_dir = NULL;
+ }
+
+ if (tracing_dir) {
+ custom_tracing_dir = strdup(tracing_dir);
+ if (!custom_tracing_dir)
+ return -1;
+ }
+
+ return 0;
+}
+
/**
* tracefs_tracing_dir - Get tracing directory
*
@@ -174,6 +201,9 @@ const char *tracefs_tracing_dir(void)
{
static const char *tracing_dir;
+ if (custom_tracing_dir)
+ return custom_tracing_dir;
+
if (tracing_dir)
return tracing_dir;
diff --git a/utest/tracefs-utest.c b/utest/tracefs-utest.c
index 3f63837..6f083db 100644
--- a/utest/tracefs-utest.c
+++ b/utest/tracefs-utest.c
@@ -11,6 +11,7 @@
#include <time.h>
#include <dirent.h>
#include <ftw.h>
+#include <libgen.h>
#include <CUnit/CUnit.h>
#include <CUnit/Basic.h>
@@ -1701,8 +1702,11 @@ void del_trace_dir(char *dir)
static void test_custom_trace_dir(void)
{
+ char *tdir = "/tmp/custom_tracefs";
struct tracefs_instance *instance;
char *dname = copy_trace_dir();
+ const char *trace_dir;
+ char *tfile;
instance = tracefs_instance_alloc(dname, NULL);
CU_TEST(instance != NULL);
@@ -1717,6 +1721,22 @@ static void test_custom_trace_dir(void)
tracefs_instance_free(instance);
del_trace_dir(dname);
free(dname);
+
+ trace_dir = tracefs_tracing_dir();
+ CU_TEST(trace_dir != NULL);
+ CU_TEST(tracefs_set_tracing_dir(tdir) == 0);
+ CU_TEST(strcmp(tdir, tracefs_tracing_dir()) == 0);
+ tfile = tracefs_get_tracing_file("trace");
+ CU_TEST(tfile != NULL);
+ CU_TEST(strcmp(tdir, dirname(tfile)) == 0);
+ free(tfile);
+
+ CU_TEST(tracefs_set_tracing_dir(NULL) == 0);
+ CU_TEST(strcmp(trace_dir, tracefs_tracing_dir()) == 0);
+ tfile = tracefs_get_tracing_file("trace");
+ CU_TEST(tfile != NULL);
+ CU_TEST(strcmp(trace_dir, dirname(tfile)) == 0);
+ free(tfile);
}
static int test_suite_destroy(void)
--
2.37.1
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