Re: [PATCH] perf kvm: fix segfault with default guest arguments

[David Ahern]

On 6/28/12 8:44 AM, Arnaldo Carvalho de Melo wrote:
> Em Sun, Jun 24, 2012 at 10:41:26PM -0600, David Ahern escreveu:
> > File generated with:
> > $ perf kvm --host --guest --guestkallsyms=/tmp/guest-kallsyms
> >      --guestmodules=/tmp/guest-modules record -a
> >
> > The report command:
> > $ perf kvm --host --guest --guestkallsyms=/tmp/guest-kallsyms
> >      --guestmodules=/tmp/guest-modules report
> >
> > dies with a SEGFAULT:
> > Program received signal SIGSEGV, Segmentation fault.
> > 0x000000000046dd7b in machine__mmap_name (self=0x0, bf=0x7fffffffbd20 "q\021", size=4096) at util/map.c:715
> > 715			snprintf(bf, size, "[%s.%d]", "guest.kernel.kallsyms", self->pid);
> >
> > (gdb) bt
> > 0  0x000000000046dd7b in machine__mmap_name (self=0x0, bf=0x7fffffffbd20 "q\021", size=4096) at util/map.c:715
> > 1  0x0000000000444161 in perf_event__process_kernel_mmap (tool=0x7fffffffdd80, event=0x7ffff7fb4120, machine=0x0) at util/event.c:562
>
> I think that this should be handled at perf_event__process_kernel_mmap,
> i.e. tools can conceivably handle this situation in their specific
> handlers.
>
> >   @@ -976,6 +976,8 @@ static int perf_session_deliver_event(struct perf_session *session,
> >   		}
> >   		return tool->sample(tool, event, sample, evsel, machine);
> >   	case PERF_RECORD_MMAP:
> > +		if (machine == NULL)
> > +			return 0;
> >   		return tool->mmap(tool, event, sample, machine);
> - Arnaldo

Ok. Doing it in perf_session_deliver_event makes it consistent with the 
SAMPLE case.

David
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