Messages in this thread | | | Subject | Re: [PATCH] perf,x86: fix uninitialized pt_regs in intel_pmu_drain_bts_buffer() | From | Peter Zijlstra <> | Date | Tue, 19 Mar 2013 13:43:04 +0100 |
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On Mon, 2013-03-18 at 14:46 +0100, Stephane Eranian wrote: > > This patch fixes an uninitialized pt_regs struct in drain BTS > function. The pt_regs struct is propagated all the way to the > code_get_segment() function from perf_instruction_pointer() > and may get garbage. > > We cannot simply inherit the actual pt_regs from the interrupt > because BTS must be flushed on context-switch or when the associated > event is disabled. And there we do not have a pt_regs handy. > > Setting pt_regs to all zeroes may not be the best option but it is > not clear what else to do given where the drain_bts_buffer() is called > from. > > Signed-off-by: Stephane Eranian <eranian@google.com> > --- > > diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c > index b05a575..208f0c8 100644 > --- a/arch/x86/kernel/cpu/perf_event_intel_ds.c > +++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c > @@ -302,6 +302,8 @@ int intel_pmu_drain_bts_buffer(void) > struct perf_sample_data data; > struct pt_regs regs; > > + memset(®s, 0, sizeof(regs)); > + > if (!event) > return 0; >
Should we not replace:
regs.ip = 0;
with that memset? It avoids the memset work in a few cases and removes the then superfluous clearing of the IP field.
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