[PATCH] perf ftrace: Fix the buffer size in __write_tracing_file

[PATCH] perf ftrace: Fix the buffer size in __write_tracing_file

[changbin.du]

From: Changbin Du <changbin.du@intel.com>

The terminal character '\0' should take into account as size of the string
buffer. Without this fix, the '--graph-funcs', '--nograph-funcs' and
'--trace-funcs' options didn't work as expected when the <func> doesn't
exist.

I didn't dive into kernel ftrace fops, but strace shows that if usersapce
writes a non-terminated string, the kernel side will return success but
no filter applied. After this fix in userspace, the kernel will return an
error.

$ sudo ./perf ftrace -a --graph-depth 1 --graph-funcs abcdefg
 0)   0.140 us    |  rcu_all_qs();
 3)   0.304 us    |  mutex_unlock();
 0)   0.153 us    |  find_vma();
 3)   0.088 us    |  __fsnotify_parent();
 0)   6.145 us    |  handle_mm_fault();
 3)   0.089 us    |  fsnotify();
 3)   0.161 us    |  __sb_end_write();
 3)   0.710 us    |  SyS_close();
 3)   7.848 us    |  exit_to_usermode_loop();

On above example, I specified function filter 'abcdefg' but all functions
are enabled.

Signed-off-by: Changbin Du <changbin.du@intel.com>
---
 tools/perf/builtin-ftrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 25a42ac..2604a64 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -69,7 +69,7 @@ static int __write_tracing_file(const char *name, const char *val, bool append)
 {
 	char *file;
 	int fd, ret = -1;
-	ssize_t size = strlen(val);
+	ssize_t size = strlen(val) + 1;
 	int flags = O_WRONLY;
 	char errbuf[512];
 
-- 
2.7.4

Re: [PATCH] perf ftrace: Fix the buffer size in __write_tracing_file

[Du, Changbin]

Hi Olsa,
What about this fix now? Thanks!

On Tue, Dec 26, 2017 at 05:26:56PM +0800, changbin.du@intel.com wrote:
> From: Changbin Du <changbin.du@intel.com>
> 
> The terminal character '\0' should take into account as size of the string
> buffer. Without this fix, the '--graph-funcs', '--nograph-funcs' and
> '--trace-funcs' options didn't work as expected when the <func> doesn't
> exist.
> 
> I didn't dive into kernel ftrace fops, but strace shows that if usersapce
> writes a non-terminated string, the kernel side will return success but
> no filter applied. After this fix in userspace, the kernel will return an
> error.
> 
> $ sudo ./perf ftrace -a --graph-depth 1 --graph-funcs abcdefg
>  0)   0.140 us    |  rcu_all_qs();
>  3)   0.304 us    |  mutex_unlock();
>  0)   0.153 us    |  find_vma();
>  3)   0.088 us    |  __fsnotify_parent();
>  0)   6.145 us    |  handle_mm_fault();
>  3)   0.089 us    |  fsnotify();
>  3)   0.161 us    |  __sb_end_write();
>  3)   0.710 us    |  SyS_close();
>  3)   7.848 us    |  exit_to_usermode_loop();
> 
> On above example, I specified function filter 'abcdefg' but all functions
> are enabled.
> 
> Signed-off-by: Changbin Du <changbin.du@intel.com>
> ---
>  tools/perf/builtin-ftrace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index 25a42ac..2604a64 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -69,7 +69,7 @@ static int __write_tracing_file(const char *name, const char *val, bool append)
>  {
>  	char *file;
>  	int fd, ret = -1;
> -	ssize_t size = strlen(val);
> +	ssize_t size = strlen(val) + 1;
>  	int flags = O_WRONLY;
>  	char errbuf[512];
>  
> -- 
> 2.7.4
> 

-- 
Thanks,
Changbin Du

Re: [PATCH] perf ftrace: Fix the buffer size in __write_tracing_file

[Jiri Olsa]

On Mon, Jan 08, 2018 at 11:05:12AM +0800, Du, Changbin wrote:
> Hi Olsa,
> What about this fix now? Thanks!
> 
> On Tue, Dec 26, 2017 at 05:26:56PM +0800, changbin.du@intel.com wrote:
> > From: Changbin Du <changbin.du@intel.com>
> > 
> > The terminal character '\0' should take into account as size of the string
> > buffer. Without this fix, the '--graph-funcs', '--nograph-funcs' and
> > '--trace-funcs' options didn't work as expected when the <func> doesn't
> > exist.
> > 
> > I didn't dive into kernel ftrace fops, but strace shows that if usersapce
> > writes a non-terminated string, the kernel side will return success but
> > no filter applied. After this fix in userspace, the kernel will return an
> > error.
> > 
> > $ sudo ./perf ftrace -a --graph-depth 1 --graph-funcs abcdefg
> >  0)   0.140 us    |  rcu_all_qs();
> >  3)   0.304 us    |  mutex_unlock();
> >  0)   0.153 us    |  find_vma();
> >  3)   0.088 us    |  __fsnotify_parent();
> >  0)   6.145 us    |  handle_mm_fault();
> >  3)   0.089 us    |  fsnotify();
> >  3)   0.161 us    |  __sb_end_write();
> >  3)   0.710 us    |  SyS_close();
> >  3)   7.848 us    |  exit_to_usermode_loop();
> > 
> > On above example, I specified function filter 'abcdefg' but all functions
> > are enabled.

hum, haven't checked, but looks like the filter is not working at all now:

[root@krava perf]# ./perf ftrace -vv -a --graph-depth 1 --graph-funcs proc_sys_read
write ' ' to tracing/set_ftrace_pid failed: Invalid argument
[root@krava perf]# ./perf ftrace -vv -a --graph-depth 1 --graph-funcs SyS_read
write ' ' to tracing/set_ftrace_pid failed: Invalid argument
[root@krava perf]# ./perf ftrace -vv -a --graph-depth 1 --graph-funcs fsnotify
write ' ' to tracing/set_ftrace_pid failed: Invalid argument

jirka

> > 
> > Signed-off-by: Changbin Du <changbin.du@intel.com>
> > ---
> >  tools/perf/builtin-ftrace.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> > index 25a42ac..2604a64 100644
> > --- a/tools/perf/builtin-ftrace.c
> > +++ b/tools/perf/builtin-ftrace.c
> > @@ -69,7 +69,7 @@ static int __write_tracing_file(const char *name, const char *val, bool append)
> >  {
> >  	char *file;
> >  	int fd, ret = -1;
> > -	ssize_t size = strlen(val);
> > +	ssize_t size = strlen(val) + 1;
> >  	int flags = O_WRONLY;
> >  	char errbuf[512];
> >  
> > -- 
> > 2.7.4
> > 
> 
> -- 
> Thanks,
> Changbin Du

Re: [PATCH] perf ftrace: Fix the buffer size in __write_tracing_file

[Du, Changbin]

On Mon, Jan 08, 2018 at 03:34:57PM +0100, Jiri Olsa wrote:
> On Mon, Jan 08, 2018 at 11:05:12AM +0800, Du, Changbin wrote:
> > Hi Olsa,
> > What about this fix now? Thanks!
> > 
> > On Tue, Dec 26, 2017 at 05:26:56PM +0800, changbin.du@intel.com wrote:
> > > From: Changbin Du <changbin.du@intel.com>
> > > 
> > > The terminal character '\0' should take into account as size of the string
> > > buffer. Without this fix, the '--graph-funcs', '--nograph-funcs' and
> > > '--trace-funcs' options didn't work as expected when the <func> doesn't
> > > exist.
> > > 
> > > I didn't dive into kernel ftrace fops, but strace shows that if usersapce
> > > writes a non-terminated string, the kernel side will return success but
> > > no filter applied. After this fix in userspace, the kernel will return an
> > > error.
> > > 
> > > $ sudo ./perf ftrace -a --graph-depth 1 --graph-funcs abcdefg
> > >  0)   0.140 us    |  rcu_all_qs();
> > >  3)   0.304 us    |  mutex_unlock();
> > >  0)   0.153 us    |  find_vma();
> > >  3)   0.088 us    |  __fsnotify_parent();
> > >  0)   6.145 us    |  handle_mm_fault();
> > >  3)   0.089 us    |  fsnotify();
> > >  3)   0.161 us    |  __sb_end_write();
> > >  3)   0.710 us    |  SyS_close();
> > >  3)   7.848 us    |  exit_to_usermode_loop();
> > > 
> > > On above example, I specified function filter 'abcdefg' but all functions
> > > are enabled.
> 
> hum, haven't checked, but looks like the filter is not working at all now:
> 
> [root@krava perf]# ./perf ftrace -vv -a --graph-depth 1 --graph-funcs proc_sys_read
> write ' ' to tracing/set_ftrace_pid failed: Invalid argument
> [root@krava perf]# ./perf ftrace -vv -a --graph-depth 1 --graph-funcs SyS_read
> write ' ' to tracing/set_ftrace_pid failed: Invalid argument
> [root@krava perf]# ./perf ftrace -vv -a --graph-depth 1 --graph-funcs fsnotify
> write ' ' to tracing/set_ftrace_pid failed: Invalid argument
>
Thanks for your test. I forgot to test normal case and thought the err is expected...

This time I dived into kernel side, and found 3 issues (if I am all right) at the
kernel function trace_get_user(). This function has problems to process both complete
C string or not.

I will send the kernel patches and Cc you guys. And I still think it is better
let perf write a complete C string.

Thanks!
Changbin Du

> jirka
>
[...] 

Re: [PATCH] perf ftrace: Fix the buffer size in __write_tracing_file

[Namhyung Kim]

Hi,

On Mon, Jan 08, 2018 at 03:34:57PM +0100, Jiri Olsa wrote:
> On Mon, Jan 08, 2018 at 11:05:12AM +0800, Du, Changbin wrote:
> > Hi Olsa,
> > What about this fix now? Thanks!
> > 
> > On Tue, Dec 26, 2017 at 05:26:56PM +0800, changbin.du@intel.com wrote:
> > > From: Changbin Du <changbin.du@intel.com>
> > > 
> > > The terminal character '\0' should take into account as size of the string
> > > buffer. Without this fix, the '--graph-funcs', '--nograph-funcs' and
> > > '--trace-funcs' options didn't work as expected when the <func> doesn't
> > > exist.
> > > 
> > > I didn't dive into kernel ftrace fops, but strace shows that if usersapce
> > > writes a non-terminated string, the kernel side will return success but
> > > no filter applied. After this fix in userspace, the kernel will return an
> > > error.
> > > 
> > > $ sudo ./perf ftrace -a --graph-depth 1 --graph-funcs abcdefg
> > >  0)   0.140 us    |  rcu_all_qs();
> > >  3)   0.304 us    |  mutex_unlock();
> > >  0)   0.153 us    |  find_vma();
> > >  3)   0.088 us    |  __fsnotify_parent();
> > >  0)   6.145 us    |  handle_mm_fault();
> > >  3)   0.089 us    |  fsnotify();
> > >  3)   0.161 us    |  __sb_end_write();
> > >  3)   0.710 us    |  SyS_close();
> > >  3)   7.848 us    |  exit_to_usermode_loop();
> > > 
> > > On above example, I specified function filter 'abcdefg' but all functions
> > > are enabled.
> 
> hum, haven't checked, but looks like the filter is not working at all now:
> 
> [root@krava perf]# ./perf ftrace -vv -a --graph-depth 1 --graph-funcs proc_sys_read
> write ' ' to tracing/set_ftrace_pid failed: Invalid argument
> [root@krava perf]# ./perf ftrace -vv -a --graph-depth 1 --graph-funcs SyS_read
> write ' ' to tracing/set_ftrace_pid failed: Invalid argument
> [root@krava perf]# ./perf ftrace -vv -a --graph-depth 1 --graph-funcs fsnotify
> write ' ' to tracing/set_ftrace_pid failed: Invalid argument

Hmm.. it seems writing a whitespace alone caused the failure.

The filter files are handled little bit different in that they process
the given string when it find a whitespace or at the close() if not.
But the thing is that it's gonna lose the return value if handled at
close().

Anyway adding a NUL character at the end won't make different IMHO
since it's not a whitespace.  And I think it needs a separate function
to set filters with a whitespace.  But this will change the program
behavior on invalid filter inputs.

Thanks,
Namhyung