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* [PATCH] tools lib traceevent: Fix kbuffer_read_at_offset()
@ 2016-10-01 10:17 Namhyung Kim
  2016-10-05 11:37 ` Arnaldo Carvalho de Melo
                   ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Namhyung Kim @ 2016-10-01 10:17 UTC (permalink / raw)
  To: Arnaldo Carvalho de Melo
  Cc: Ingo Molnar, Peter Zijlstra, Jiri Olsa, LKML, Steven Rostedt

When it's called with an offset less than or equal to the first event,
it'll return a garbage value since the data is not initialized.

Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/lib/traceevent/kbuffer-parse.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/lib/traceevent/kbuffer-parse.c b/tools/lib/traceevent/kbuffer-parse.c
index 3bcada3ae05a..65984f1c2974 100644
--- a/tools/lib/traceevent/kbuffer-parse.c
+++ b/tools/lib/traceevent/kbuffer-parse.c
@@ -622,6 +622,7 @@ void *kbuffer_read_at_offset(struct kbuffer *kbuf, int offset,
 
 	/* Reset the buffer */
 	kbuffer_load_subbuffer(kbuf, kbuf->subbuffer);
+	data = kbuffer_read_event(kbuf, ts);
 
 	while (kbuf->curr < offset) {
 		data = kbuffer_next_event(kbuf, ts);
-- 
2.10.0

^ permalink raw reply related	[flat|nested] 6+ messages in thread
* Re: [PATCH] tools lib traceevent: Fix kbuffer_read_at_offset()
  2016-10-01 10:17 [PATCH] tools lib traceevent: Fix kbuffer_read_at_offset() Namhyung Kim
@ 2016-10-05 11:37 ` Arnaldo Carvalho de Melo
  2016-10-05 13:28 ` Steven Rostedt
  2016-10-06 22:41 ` [tip:perf/urgent] " tip-bot for Namhyung Kim
  2 siblings, 0 replies; 6+ messages in thread
From: Arnaldo Carvalho de Melo @ 2016-10-05 11:37 UTC (permalink / raw)
  To: Steven Rostedt; +Cc: Namhyung Kim, Ingo Molnar, Peter Zijlstra, Jiri Olsa, LKML

Em Sat, Oct 01, 2016 at 07:17:00PM +0900, Namhyung Kim escreveu:
> When it's called with an offset less than or equal to the first event,
> it'll return a garbage value since the data is not initialized.

Steven, Ack?

- Arnaldo
 
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
>  tools/lib/traceevent/kbuffer-parse.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/tools/lib/traceevent/kbuffer-parse.c b/tools/lib/traceevent/kbuffer-parse.c
> index 3bcada3ae05a..65984f1c2974 100644
> --- a/tools/lib/traceevent/kbuffer-parse.c
> +++ b/tools/lib/traceevent/kbuffer-parse.c
> @@ -622,6 +622,7 @@ void *kbuffer_read_at_offset(struct kbuffer *kbuf, int offset,
>  
>  	/* Reset the buffer */
>  	kbuffer_load_subbuffer(kbuf, kbuf->subbuffer);
> +	data = kbuffer_read_event(kbuf, ts);
>  
>  	while (kbuf->curr < offset) {
>  		data = kbuffer_next_event(kbuf, ts);
> -- 
> 2.10.0

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] tools lib traceevent: Fix kbuffer_read_at_offset()
  2016-10-01 10:17 [PATCH] tools lib traceevent: Fix kbuffer_read_at_offset() Namhyung Kim
  2016-10-05 11:37 ` Arnaldo Carvalho de Melo
@ 2016-10-05 13:28 ` Steven Rostedt
  2016-10-07  4:19   ` Namhyung Kim
  2016-10-06 22:41 ` [tip:perf/urgent] " tip-bot for Namhyung Kim
  2 siblings, 1 reply; 6+ messages in thread
From: Steven Rostedt @ 2016-10-05 13:28 UTC (permalink / raw)
  To: Namhyung Kim
  Cc: Arnaldo Carvalho de Melo, Ingo Molnar, Peter Zijlstra, Jiri Olsa, LKML

On Sat,  1 Oct 2016 19:17:00 +0900
Namhyung Kim <namhyung@kernel.org> wrote:

> When it's called with an offset less than or equal to the first event,
> it'll return a garbage value since the data is not initialized.

Well, it can at most be equal to (unless offset is negative) because
kbuffer_load_subbuffer() sets kbuf->curr to zero.

But that said, it looks like offset == 0 is buggy.

Acked-by: Steven Rostedt <rostedt@goodmis.org>


-- Steve

> 
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
>  tools/lib/traceevent/kbuffer-parse.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/tools/lib/traceevent/kbuffer-parse.c b/tools/lib/traceevent/kbuffer-parse.c
> index 3bcada3ae05a..65984f1c2974 100644
> --- a/tools/lib/traceevent/kbuffer-parse.c
> +++ b/tools/lib/traceevent/kbuffer-parse.c
> @@ -622,6 +622,7 @@ void *kbuffer_read_at_offset(struct kbuffer *kbuf, int offset,
>  
>  	/* Reset the buffer */
>  	kbuffer_load_subbuffer(kbuf, kbuf->subbuffer);
> +	data = kbuffer_read_event(kbuf, ts);
>  
>  	while (kbuf->curr < offset) {
>  		data = kbuffer_next_event(kbuf, ts);

^ permalink raw reply	[flat|nested] 6+ messages in thread
* [tip:perf/urgent] tools lib traceevent: Fix kbuffer_read_at_offset()
  2016-10-01 10:17 [PATCH] tools lib traceevent: Fix kbuffer_read_at_offset() Namhyung Kim
  2016-10-05 11:37 ` Arnaldo Carvalho de Melo
  2016-10-05 13:28 ` Steven Rostedt
@ 2016-10-06 22:41 ` tip-bot for Namhyung Kim
  2 siblings, 0 replies; 6+ messages in thread
From: tip-bot for Namhyung Kim @ 2016-10-06 22:41 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: acme, tglx, namhyung, rostedt, jolsa, linux-kernel, peterz, hpa, mingo

Commit-ID:  a130347973c408c0e0017a52c74cbc3226c1f0ef
Gitweb:     http://git.kernel.org/tip/a130347973c408c0e0017a52c74cbc3226c1f0ef
Author:     Namhyung Kim <namhyung@kernel.org>
AuthorDate: Sat, 1 Oct 2016 19:17:00 +0900
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Wed, 5 Oct 2016 11:36:22 -0300

tools lib traceevent: Fix kbuffer_read_at_offset()

When it's called with an offset less than or equal to the first event,
it'll return a garbage value since the data is not initialized.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20161001101700.29146-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/lib/traceevent/kbuffer-parse.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/lib/traceevent/kbuffer-parse.c b/tools/lib/traceevent/kbuffer-parse.c
index 3bcada3..65984f1 100644
--- a/tools/lib/traceevent/kbuffer-parse.c
+++ b/tools/lib/traceevent/kbuffer-parse.c
@@ -622,6 +622,7 @@ void *kbuffer_read_at_offset(struct kbuffer *kbuf, int offset,
 
 	/* Reset the buffer */
 	kbuffer_load_subbuffer(kbuf, kbuf->subbuffer);
+	data = kbuffer_read_event(kbuf, ts);
 
 	while (kbuf->curr < offset) {
 		data = kbuffer_next_event(kbuf, ts);

^ permalink raw reply related	[flat|nested] 6+ messages in thread
* Re: [PATCH] tools lib traceevent: Fix kbuffer_read_at_offset()
  2016-10-05 13:28 ` Steven Rostedt
@ 2016-10-07  4:19   ` Namhyung Kim
  2016-10-07 14:06     ` Steven Rostedt
  0 siblings, 1 reply; 6+ messages in thread
From: Namhyung Kim @ 2016-10-07  4:19 UTC (permalink / raw)
  To: Steven Rostedt
  Cc: Arnaldo Carvalho de Melo, Ingo Molnar, Peter Zijlstra, Jiri Olsa, LKML

Hi Steve,

On Wed, Oct 05, 2016 at 09:28:01AM -0400, Steven Rostedt wrote:
> On Sat,  1 Oct 2016 19:17:00 +0900
> Namhyung Kim <namhyung@kernel.org> wrote:
> 
> > When it's called with an offset less than or equal to the first event,
> > it'll return a garbage value since the data is not initialized.
> 
> Well, it can at most be equal to (unless offset is negative) because
> kbuffer_load_subbuffer() sets kbuf->curr to zero.

Actually kbuffer_load_subbuffer() calls kbuf->next_event().  Inside
the function it has a loop updating next valid event.  Sometimes, the
data starts with TIME_EXTEND with value of 0 and the loop skips it
which ended up setting kbuf->curr to 8. :)

I'll take a look it later.

> 
> But that said, it looks like offset == 0 is buggy.
> 
> Acked-by: Steven Rostedt <rostedt@goodmis.org>

Thanks,
Namhyung

> 
> 
> -- Steve
> 
> > 
> > Cc: Steven Rostedt <rostedt@goodmis.org>
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> >  tools/lib/traceevent/kbuffer-parse.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/tools/lib/traceevent/kbuffer-parse.c b/tools/lib/traceevent/kbuffer-parse.c
> > index 3bcada3ae05a..65984f1c2974 100644
> > --- a/tools/lib/traceevent/kbuffer-parse.c
> > +++ b/tools/lib/traceevent/kbuffer-parse.c
> > @@ -622,6 +622,7 @@ void *kbuffer_read_at_offset(struct kbuffer *kbuf, int offset,
> >  
> >  	/* Reset the buffer */
> >  	kbuffer_load_subbuffer(kbuf, kbuf->subbuffer);
> > +	data = kbuffer_read_event(kbuf, ts);
> >  
> >  	while (kbuf->curr < offset) {
> >  		data = kbuffer_next_event(kbuf, ts);
> 

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] tools lib traceevent: Fix kbuffer_read_at_offset()
  2016-10-07  4:19   ` Namhyung Kim
@ 2016-10-07 14:06     ` Steven Rostedt
  0 siblings, 0 replies; 6+ messages in thread
From: Steven Rostedt @ 2016-10-07 14:06 UTC (permalink / raw)
  To: Namhyung Kim
  Cc: Arnaldo Carvalho de Melo, Ingo Molnar, Peter Zijlstra, Jiri Olsa, LKML

On Fri, 7 Oct 2016 13:19:08 +0900
Namhyung Kim <namhyung@kernel.org> wrote:

> Actually kbuffer_load_subbuffer() calls kbuf->next_event().  Inside
> the function it has a loop updating next valid event.  Sometimes, the
> data starts with TIME_EXTEND with value of 0 and the loop skips it
> which ended up setting kbuf->curr to 8. :)

Right, because kbuffer_read_at_offset() should not return a TIME_EXTEND.

-- Steve

^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2016-10-07 14:07 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-10-01 10:17 [PATCH] tools lib traceevent: Fix kbuffer_read_at_offset() Namhyung Kim
2016-10-05 11:37 ` Arnaldo Carvalho de Melo
2016-10-05 13:28 ` Steven Rostedt
2016-10-07  4:19   ` Namhyung Kim
2016-10-07 14:06     ` Steven Rostedt
2016-10-06 22:41 ` [tip:perf/urgent] " tip-bot for Namhyung Kim

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