lkml.org 
[lkml]   [2013]   [Mar]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] perf,x86: fix uninitialized pt_regs in intel_pmu_drain_bts_buffer()
From
Date
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(&regs, 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.



\
 
 \ /
  Last update: 2013-03-19 14:21    [W:0.038 / U:0.524 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site