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SubjectRe: [PATCH] perf script: Fix obtaining next event
Em Wed, Oct 30, 2019 at 03:16:10PM +0530, Ravi Bangoria escreveu:
>
>
> On 10/30/19 2:10 PM, Chandan Rajendra wrote:
> > The current code segfaults when perf.data file contains two or more
> > events. This happens due to incorrect pointer arithmetic being performed
> > in trace_find_next_event().
> >
> > tep_handle->events is an array of pointers to 'struct tep_event'. The
> > pointer arithmetic interprets tep_handle->events as an array of 'struct
> > tep_event' elements.
> >
> > This commit replaces the usage of pointer arithmetic with calls to
> > tep_get_event().
> >
> > Fixes: bb3dd7e ("tools lib traceevent, perf tools: Move struct tep_handler definition in a local header file")
> > Signed-off-by: Chandan Rajendra <chandanrlinux@gmail.com>
>
> $ sudo ./perf record -e sched:sched_switch -e syscalls:sys_enter_openat -- make
>
> Without patch:
> $ sudo ./perf script -g python
> Segmentation fault
>
> With patch:
> $ sudo ./perf script -g python
> generated Python script: perf-script.py
>
> Reviewed-and-tested-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>

This was fixed already in perf/core, by Steven:

commit 9bdff5b6436655d42dd30253c521e86ce07b9961
Author: Steven Rostedt (VMware) <rostedt@goodmis.org>
Date: Thu Oct 17 17:05:23 2019 -0400

perf tools: Remove unused trace_find_next_event()

trace_find_next_event() was buggy and pretty much a useless helper. As
there are no more users, just remove it.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Tzvetomir Stoyanov <tstoyanov@vmware.com>
Cc: linux-trace-devel@vger.kernel.org
Link: http://lore.kernel.org/lkml/20191017210636.224045576@goodmis.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

commit a5e05abc6b8d81148b35cd8632a4a6252383d968
Author: Steven Rostedt (VMware) <rostedt@goodmis.org>
Date: Thu Oct 17 17:05:22 2019 -0400

perf scripting engines: Iterate on tep event arrays directly

Instead of calling a useless (and broken) helper function to get the
next event of a tep event array, just get the array directly and iterate
over it.

Note, the broken part was from trace_find_next_event() which after this
will no longer be used, and can be removed.

Committer notes:

This fixes a segfault when generating python scripts from perf.data
files with multiple tracepoint events, i.e. the following use case is
fixed by this patch:

# perf record -e sched:* sleep 1
[ perf record: Woken up 31 times to write data ]
[ perf record: Captured and wrote 0.031 MB perf.data (9 samples) ]
# perf script -g python
Segmentation fault (core dumped)
#

Reported-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Tzvetomir Stoyanov <tstoyanov@vmware.com>
Cc: linux-trace-devel@vger.kernel.org
Link: http://lkml.kernel.org/r/20191017153733.630cd5eb@gandalf.local.home
Link: http://lore.kernel.org/lkml/20191017210636.061448713@goodmis.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

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