Re: perf list dumps core using 5.13.0.rc2

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Wed, May 19, 2021 at 09:27:14AM -0700, Ian Rogers escreveu:
> On Wed, May 19, 2021 at 7:57 AM Thomas Richter <tmricht@linux.ibm.com> wrote:
> >
> > Using kernel 5.13.0.rc2 command perf list dumps core on my x86
> > virtual machine:
> >
> > [root@f34 perf]# ./perf list
> > Segmentation fault (core dumped)
> > ^C
> > [root@f34 perf]#
> >
> > The root case this this change in file ../include/uapi/linux/perf_event.h:
> > enum perf_sw_ids {
> >         PERF_COUNT_SW_CPU_CLOCK                 = 0,
> >         ...
> >  --->   PERF_COUNT_SW_CGROUP_SWITCHES           = 11,
> >
> >         PERF_COUNT_SW_MAX,                      /* non-ABI */
> > };
> >
> > This change increases PERF_COUNT_SW_MAX to 12. However this
> > change is not reflected in file util/parse-events.c where data structure
> >
> > struct event_symbol event_symbols_sw[PERF_COUNT_SW_MAX] = {
> >         ....
> > }
> >
> > is defined and it misses the symbol name and alias for this new software
> > event. So when command 'perf list' is called, the call chain sequence
> > is
> >   cmd_list()
> >     print_events()
> >       print_symbol_events(event_glob, PERF_TYPE_SOFTWARE,
> >                           event_symbols_sw, PERF_COUNT_SW_MAX, name_only);
> >
> > where PERF_COUNT_SW_MAX is 12 and  structure event_symbols_sw[] contains
> > only 11 elements. This ends up with the last element of the array being
> > all zeroes and the line:
> >
> >     if (!name_only && strlen(syms->alias))
> >
> > dumps core because syms->alias is a NULL pointer.
> >
> > Is this dummy event PERF_COUNT_SW_CGROUP_SWITCHES simply missing in the
> > event_symbols_sw[] array or is there more to it (which I am missing).
> >
> > Thanks.
> >
> > PS: I can sent a patch if needed....
> 
> I believe Namhyung's pending change will fix this:
> https://lore.kernel.org/lkml/20210210083327.22726-3-namhyung@kernel.org/

Ok, I'll pick that one instead of the one I did, similar one.

- Arnaldo