[PATCH] perf_event: mount debugfs automatically

[PATCH] perf_event: mount debugfs automatically

[Xiao Guangrong]

Mount debugfs automatically if it's not mounted, umount it
when programme exit

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 tools/perf/perf.c         |   10 +++++++++-
 tools/perf/util/debugfs.c |   16 +++++++---------
 tools/perf/util/debugfs.h |    2 +-
 3 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 873e55f..ee84fc1 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -388,7 +388,7 @@ static int run_argv(int *argcp, const char ***argv)
 /* mini /proc/mounts parser: searching for "^blah /mount/point debugfs" */
 static void get_debugfs_mntpt(void)
 {
-	const char *path = debugfs_find_mountpoint();
+	const char *path = debugfs_mount(NULL);
 
 	if (path)
 		strncpy(debugfs_mntpt, path, sizeof(debugfs_mntpt));
@@ -396,6 +396,11 @@ static void get_debugfs_mntpt(void)
 		debugfs_mntpt[0] = '\0';
 }
 
+static void umount_debugfs(void)
+{
+	debugfs_umount();
+}
+
 int main(int argc, const char **argv)
 {
 	const char *cmd;
@@ -405,6 +410,9 @@ int main(int argc, const char **argv)
 		cmd = "perf-help";
 	/* get debugfs mount point from /proc/mounts */
 	get_debugfs_mntpt();
+
+	atexit(umount_debugfs);
+
 	/*
 	 * "perf-xxxx" is the same as "perf xxxx", but we obviously:
 	 *
diff --git a/tools/perf/util/debugfs.c b/tools/perf/util/debugfs.c
index 06b73ee..1f805fd 100644
--- a/tools/perf/util/debugfs.c
+++ b/tools/perf/util/debugfs.c
@@ -106,16 +106,14 @@ int debugfs_valid_entry(const char *path)
 	return 0;
 }
 
-/* mount the debugfs somewhere */
+/* mount the debugfs somewhere if it's not mounted */
 
-int debugfs_mount(const char *mountpoint)
+char *debugfs_mount(const char *mountpoint)
 {
-	char mountcmd[128];
-
 	/* see if it's already mounted */
 	if (debugfs_find_mountpoint()) {
 		debugfs_premounted = 1;
-		return 0;
+		return debugfs_mountpoint;
 	}
 
 	/* if not mounted and no argument */
@@ -127,13 +125,13 @@ int debugfs_mount(const char *mountpoint)
 			mountpoint = "/sys/kernel/debug";
 	}
 
+	if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
+		return NULL;
+
 	/* save the mountpoint */
 	strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
 
-	/* mount it */
-	snprintf(mountcmd, sizeof(mountcmd),
-		 "/bin/mount -t debugfs debugfs %s", mountpoint);
-	return system(mountcmd);
+	return debugfs_mountpoint;
 }
 
 /* umount the debugfs */
diff --git a/tools/perf/util/debugfs.h b/tools/perf/util/debugfs.h
index 3cd14f9..83a0287 100644
--- a/tools/perf/util/debugfs.h
+++ b/tools/perf/util/debugfs.h
@@ -15,7 +15,7 @@
 extern const char *debugfs_find_mountpoint(void);
 extern int debugfs_valid_mountpoint(const char *debugfs);
 extern int debugfs_valid_entry(const char *path);
-extern int debugfs_mount(const char *mountpoint);
+extern char *debugfs_mount(const char *mountpoint);
 extern int debugfs_umount(void);
 extern int debugfs_write(const char *entry, const char *value);
 extern int debugfs_read(const char *entry, char *buffer, size_t size);
-- 
1.6.1.2

Re: [PATCH] perf_event: mount debugfs automatically

[Ingo Molnar]

* Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> wrote:

> Mount debugfs automatically if it's not mounted, umount it
> when programme exit
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
> ---
>  tools/perf/perf.c         |   10 +++++++++-
>  tools/perf/util/debugfs.c |   16 +++++++---------
>  tools/perf/util/debugfs.h |    2 +-
>  3 files changed, 17 insertions(+), 11 deletions(-)

I'm not sure that's a good idea. What happens if two perf tools are running in 
parallel:

  perf report #1 start
                          perf report #2 start
  perf report #2 exit [umount debugfs]
                          perf report #2 tries to open /debug file: kaboom
                          perf report #2 exit

But your idea is sound if we only do the first half: we should mount it under 
/sys/kernel/debug/ if it's not mounted already [and that directory is 
available], and leave it mounted there.

Furthermore please not that we must not mount it under any other path - 
mounting is always a dangerous operation because it changes the VFS namespace. 
For example some system might have some local files under /debug for whatever 
reason, we must not over-mount it and potentially destroy data because we'd 
confuse an app that writes into /debug. /sys/kernel/debug/ is a fair game to 
mount into OTOH.

(and even then we should just leave it mounted and never umount it.)

Thanks,

	Ingo

Re: [PATCH] perf_event: mount debugfs automatically

[Xiao Guangrong]

Ingo Molnar wrote:
> * Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> wrote:
> 
>> Mount debugfs automatically if it's not mounted, umount it
>> when programme exit
>>
>> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
>> ---
>>  tools/perf/perf.c         |   10 +++++++++-
>>  tools/perf/util/debugfs.c |   16 +++++++---------
>>  tools/perf/util/debugfs.h |    2 +-
>>  3 files changed, 17 insertions(+), 11 deletions(-)
> 
> I'm not sure that's a good idea. What happens if two perf tools are running in 
> parallel:
> 
>   perf report #1 start
>                           perf report #2 start
>   perf report #2 exit [umount debugfs]
>                           perf report #2 tries to open /debug file: kaboom
>                           perf report #2 exit
> 

Sorry, i not notice it, it can't work under this case.

> But your idea is sound if we only do the first half: we should mount it under 
> /sys/kernel/debug/ if it's not mounted already [and that directory is 
> available], and leave it mounted there.
> 

Um, i'll rewrite it and just mount it under /sys/kernel/debug

Thanks,
Xiao

Re: [PATCH] perf_event: mount debugfs automatically

[Ingo Molnar]

* Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> wrote:

> > But your idea is sound if we only do the first half: we should mount it 
> > under /sys/kernel/debug/ if it's not mounted already [and that directory 
> > is available], and leave it mounted there.
> > 
> 
> Um, i'll rewrite it and just mount it under /sys/kernel/debug

Yeah, i think that will work better. Thanks!

	Ingo

[PATCH v2 1/3] perf tools: mount debugfs automatically

[Xiao Guangrong]

Mount debugfs filesystem under '/sys/kernel/debug' if it's not mounted

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 tools/perf/perf.c         |    2 +-
 tools/perf/util/debugfs.c |   16 +++++++---------
 tools/perf/util/debugfs.h |    2 +-
 3 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 873e55f..fc89005 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -388,7 +388,7 @@ static int run_argv(int *argcp, const char ***argv)
 /* mini /proc/mounts parser: searching for "^blah /mount/point debugfs" */
 static void get_debugfs_mntpt(void)
 {
-	const char *path = debugfs_find_mountpoint();
+	const char *path = debugfs_mount(NULL);
 
 	if (path)
 		strncpy(debugfs_mntpt, path, sizeof(debugfs_mntpt));
diff --git a/tools/perf/util/debugfs.c b/tools/perf/util/debugfs.c
index 06b73ee..1f805fd 100644
--- a/tools/perf/util/debugfs.c
+++ b/tools/perf/util/debugfs.c
@@ -106,16 +106,14 @@ int debugfs_valid_entry(const char *path)
 	return 0;
 }
 
-/* mount the debugfs somewhere */
+/* mount the debugfs somewhere if it's not mounted */
 
-int debugfs_mount(const char *mountpoint)
+char *debugfs_mount(const char *mountpoint)
 {
-	char mountcmd[128];
-
 	/* see if it's already mounted */
 	if (debugfs_find_mountpoint()) {
 		debugfs_premounted = 1;
-		return 0;
+		return debugfs_mountpoint;
 	}
 
 	/* if not mounted and no argument */
@@ -127,13 +125,13 @@ int debugfs_mount(const char *mountpoint)
 			mountpoint = "/sys/kernel/debug";
 	}
 
+	if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
+		return NULL;
+
 	/* save the mountpoint */
 	strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
 
-	/* mount it */
-	snprintf(mountcmd, sizeof(mountcmd),
-		 "/bin/mount -t debugfs debugfs %s", mountpoint);
-	return system(mountcmd);
+	return debugfs_mountpoint;
 }
 
 /* umount the debugfs */
diff --git a/tools/perf/util/debugfs.h b/tools/perf/util/debugfs.h
index 3cd14f9..83a0287 100644
--- a/tools/perf/util/debugfs.h
+++ b/tools/perf/util/debugfs.h
@@ -15,7 +15,7 @@
 extern const char *debugfs_find_mountpoint(void);
 extern int debugfs_valid_mountpoint(const char *debugfs);
 extern int debugfs_valid_entry(const char *path);
-extern int debugfs_mount(const char *mountpoint);
+extern char *debugfs_mount(const char *mountpoint);
 extern int debugfs_umount(void);
 extern int debugfs_write(const char *entry, const char *value);
 extern int debugfs_read(const char *entry, char *buffer, size_t size);
-- 
1.6.1.2

[PATCH 2/3] perf trace: cleanup find_debugfs()

[Xiao Guangrong]

Remove redundant code for 'perf trace'

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 tools/perf/util/debugfs.c          |    1 +
 tools/perf/util/trace-event-info.c |   29 +++++------------------------
 2 files changed, 6 insertions(+), 24 deletions(-)

diff --git a/tools/perf/util/debugfs.c b/tools/perf/util/debugfs.c
index 1f805fd..a88fefc 100644
--- a/tools/perf/util/debugfs.c
+++ b/tools/perf/util/debugfs.c
@@ -130,6 +130,7 @@ char *debugfs_mount(const char *mountpoint)
 
 	/* save the mountpoint */
 	strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
+	debugfs_found = 1;
 
 	return debugfs_mountpoint;
 }
diff --git a/tools/perf/util/trace-event-info.c b/tools/perf/util/trace-event-info.c
index cace355..5dd5c81 100644
--- a/tools/perf/util/trace-event-info.c
+++ b/tools/perf/util/trace-event-info.c
@@ -37,6 +37,7 @@
 
 #include "../perf.h"
 #include "trace-event.h"
+#include "debugfs.h"
 
 #define VERSION "0.5"
 
@@ -101,32 +102,12 @@ void *malloc_or_die(unsigned int size)
 
 static const char *find_debugfs(void)
 {
-	static char debugfs[MAX_PATH+1];
-	static int debugfs_found;
-	char type[100];
-	FILE *fp;
-
-	if (debugfs_found)
-		return debugfs;
-
-	if ((fp = fopen("/proc/mounts","r")) == NULL)
-		die("Can't open /proc/mounts for read");
-
-	while (fscanf(fp, "%*s %"
-		      STR(MAX_PATH)
-		      "s %99s %*s %*d %*d\n",
-		      debugfs, type) == 2) {
-		if (strcmp(type, "debugfs") == 0)
-			break;
-	}
-	fclose(fp);
-
-	if (strcmp(type, "debugfs") != 0)
-		die("debugfs not mounted, please mount");
+	const char *path = debugfs_mount(NULL);
 
-	debugfs_found = 1;
+	if (!path)
+		die("Your kernel not support debugfs filesystem");
 
-	return debugfs;
+	return path;
 }
 
 /*
-- 
1.6.1.2

[PATCH 3/3] perf trace: fix forgetting close file/dir

[Xiao Guangrong]

Fix forgetting close file/dir

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 tools/perf/util/trace-event-info.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/trace-event-info.c b/tools/perf/util/trace-event-info.c
index 5dd5c81..2c84fb6 100644
--- a/tools/perf/util/trace-event-info.c
+++ b/tools/perf/util/trace-event-info.c
@@ -252,6 +252,8 @@ static void read_header_files(void)
 	write_or_die("header_page", 12);
 	write_or_die(&size, 8);
 	check_size = copy_file_fd(fd);
+	close(fd);
+
 	if (size != check_size)
 		die("wrong size for '%s' size=%lld read=%lld",
 		    path, size, check_size);
@@ -270,6 +272,7 @@ static void read_header_files(void)
 	if (size != check_size)
 		die("wrong size for '%s'", path);
 	put_tracing_file(path);
+	close(fd);
 }
 
 static bool name_in_tp_list(char *sys, struct tracepoint_path *tps)
@@ -334,6 +337,7 @@ static void copy_event_system(const char *sys, struct tracepoint_path *tps)
 
 		free(format);
 	}
+	closedir(dir);
 }
 
 static void read_ftrace_files(struct tracepoint_path *tps)
@@ -411,6 +415,7 @@ static void read_event_files(struct tracepoint_path *tps)
 		free(sys);
 	}
 
+	closedir(dir);
 	put_tracing_file(path);
 }
 
-- 
1.6.1.2

[tip:perf/core] perf tools: Mount debugfs automatically

[tip-bot for Xiao Guangrong]

Commit-ID:  29c52aa2300173dd45df04dae1f5acc81a2c93b1
Gitweb:     http://git.kernel.org/tip/29c52aa2300173dd45df04dae1f5acc81a2c93b1
Author:     Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
AuthorDate: Mon, 28 Dec 2009 16:47:12 +0800
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 28 Dec 2009 10:36:36 +0100

perf tools: Mount debugfs automatically

Mount debugfs filesystem under '/sys/kernel/debug', if it's not
mounted.

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <4B387090.7080407@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 tools/perf/perf.c         |    2 +-
 tools/perf/util/debugfs.c |   16 +++++++---------
 tools/perf/util/debugfs.h |    2 +-
 3 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 873e55f..fc89005 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -388,7 +388,7 @@ static int run_argv(int *argcp, const char ***argv)
 /* mini /proc/mounts parser: searching for "^blah /mount/point debugfs" */
 static void get_debugfs_mntpt(void)
 {
-	const char *path = debugfs_find_mountpoint();
+	const char *path = debugfs_mount(NULL);
 
 	if (path)
 		strncpy(debugfs_mntpt, path, sizeof(debugfs_mntpt));
diff --git a/tools/perf/util/debugfs.c b/tools/perf/util/debugfs.c
index 06b73ee..1f805fd 100644
--- a/tools/perf/util/debugfs.c
+++ b/tools/perf/util/debugfs.c
@@ -106,16 +106,14 @@ int debugfs_valid_entry(const char *path)
 	return 0;
 }
 
-/* mount the debugfs somewhere */
+/* mount the debugfs somewhere if it's not mounted */
 
-int debugfs_mount(const char *mountpoint)
+char *debugfs_mount(const char *mountpoint)
 {
-	char mountcmd[128];
-
 	/* see if it's already mounted */
 	if (debugfs_find_mountpoint()) {
 		debugfs_premounted = 1;
-		return 0;
+		return debugfs_mountpoint;
 	}
 
 	/* if not mounted and no argument */
@@ -127,13 +125,13 @@ int debugfs_mount(const char *mountpoint)
 			mountpoint = "/sys/kernel/debug";
 	}
 
+	if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
+		return NULL;
+
 	/* save the mountpoint */
 	strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
 
-	/* mount it */
-	snprintf(mountcmd, sizeof(mountcmd),
-		 "/bin/mount -t debugfs debugfs %s", mountpoint);
-	return system(mountcmd);
+	return debugfs_mountpoint;
 }
 
 /* umount the debugfs */
diff --git a/tools/perf/util/debugfs.h b/tools/perf/util/debugfs.h
index 3cd14f9..83a0287 100644
--- a/tools/perf/util/debugfs.h
+++ b/tools/perf/util/debugfs.h
@@ -15,7 +15,7 @@
 extern const char *debugfs_find_mountpoint(void);
 extern int debugfs_valid_mountpoint(const char *debugfs);
 extern int debugfs_valid_entry(const char *path);
-extern int debugfs_mount(const char *mountpoint);
+extern char *debugfs_mount(const char *mountpoint);
 extern int debugfs_umount(void);
 extern int debugfs_write(const char *entry, const char *value);
 extern int debugfs_read(const char *entry, char *buffer, size_t size);

[tip:perf/core] perf trace: Clean up find_debugfs()

[tip-bot for Xiao Guangrong]

Commit-ID:  61be3e59ba7a6dbd39f92fd1f107285a0caeb008
Gitweb:     http://git.kernel.org/tip/61be3e59ba7a6dbd39f92fd1f107285a0caeb008
Author:     Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
AuthorDate: Mon, 28 Dec 2009 16:48:30 +0800
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 28 Dec 2009 10:36:36 +0100

perf trace: Clean up find_debugfs()

Remove redundant code for 'perf trace'

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <4B3870DE.7090500@cn.fujitsu.com>
[ v2: resolved conflicts with recent changes ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 tools/perf/util/debugfs.c          |    1 +
 tools/perf/util/trace-event-info.c |   29 +++++------------------------
 2 files changed, 6 insertions(+), 24 deletions(-)

diff --git a/tools/perf/util/debugfs.c b/tools/perf/util/debugfs.c
index 1f805fd..a88fefc 100644
--- a/tools/perf/util/debugfs.c
+++ b/tools/perf/util/debugfs.c
@@ -130,6 +130,7 @@ char *debugfs_mount(const char *mountpoint)
 
 	/* save the mountpoint */
 	strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
+	debugfs_found = 1;
 
 	return debugfs_mountpoint;
 }
diff --git a/tools/perf/util/trace-event-info.c b/tools/perf/util/trace-event-info.c
index dfef238..535176d 100644
--- a/tools/perf/util/trace-event-info.c
+++ b/tools/perf/util/trace-event-info.c
@@ -38,6 +38,7 @@
 
 #include "../perf.h"
 #include "trace-event.h"
+#include "debugfs.h"
 
 #define VERSION "0.5"
 
@@ -102,32 +103,12 @@ void *malloc_or_die(unsigned int size)
 
 static const char *find_debugfs(void)
 {
-	static char debugfs[MAX_PATH+1];
-	static int debugfs_found;
-	FILE *fp;
-	struct mntent *m;
-
-	if (debugfs_found)
-		return debugfs;
-
-	fp = setmntent("/proc/mounts", "r");
-	if (!fp)
-		die("Can't open /proc/mounts for read");
-
-	while ((m = getmntent(fp)) != NULL) {
-		if (strcmp(m->mnt_type, "debugfs") == 0) {
-			strcpy(debugfs, m->mnt_dir);
-			debugfs_found = 1;
-			break;
-		}
-	}
-
-	endmntent(fp);
+	const char *path = debugfs_mount(NULL);
 
-	if (!debugfs_found)
-		die("debugfs not mounted, please mount");
+	if (!path)
+		die("Your kernel not support debugfs filesystem");
 
-	return debugfs;
+	return path;
 }
 
 /*

[tip:perf/core] perf trace: Fix forgotten close of file/dir

[tip-bot for Xiao Guangrong]

Commit-ID:  9967411e5b324a908e344d6ce66b77bd5d372c3e
Gitweb:     http://git.kernel.org/tip/9967411e5b324a908e344d6ce66b77bd5d372c3e
Author:     Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
AuthorDate: Mon, 28 Dec 2009 16:49:38 +0800
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 28 Dec 2009 10:36:36 +0100

perf trace: Fix forgotten close of file/dir

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <4B387122.7090801@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 tools/perf/util/trace-event-info.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/trace-event-info.c b/tools/perf/util/trace-event-info.c
index 535176d..407fd65 100644
--- a/tools/perf/util/trace-event-info.c
+++ b/tools/perf/util/trace-event-info.c
@@ -253,6 +253,8 @@ static void read_header_files(void)
 	write_or_die("header_page", 12);
 	write_or_die(&size, 8);
 	check_size = copy_file_fd(fd);
+	close(fd);
+
 	if (size != check_size)
 		die("wrong size for '%s' size=%lld read=%lld",
 		    path, size, check_size);
@@ -271,6 +273,7 @@ static void read_header_files(void)
 	if (size != check_size)
 		die("wrong size for '%s'", path);
 	put_tracing_file(path);
+	close(fd);
 }
 
 static bool name_in_tp_list(char *sys, struct tracepoint_path *tps)
@@ -337,6 +340,7 @@ static void copy_event_system(const char *sys, struct tracepoint_path *tps)
 
 		free(format);
 	}
+	closedir(dir);
 }
 
 static void read_ftrace_files(struct tracepoint_path *tps)
@@ -407,6 +411,7 @@ static void read_event_files(struct tracepoint_path *tps)
 		free(sys);
 	}
 
+	closedir(dir);
 	put_tracing_file(path);
 }