linux-kernel - Re: [PATCH] perf,x86: fix uninitialized pt_regs in intel_pmu_drain_bts

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Date:	Tue, 19 Mar 2013 13:58:22 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>, Jiri Olsa <jolsa@...hat.com>,
	Salman Qazi <sqazi@...gle.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>
Subject: Re: [PATCH] perf,x86: fix uninitialized pt_regs in
 intel_pmu_drain_bts_buffer()

On Tue, 2013-03-19 at 13:50 +0100, Stephane Eranian wrote:
> > 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.
> >
> We could drop it because it's covered by the memset().

Yeah, but also place the memset a little lower than you did, avoids the
stack writes when not needed.

> The issue here was that you eventually end up in code_segment_base()
> which
> looks at other uninitialized fields in pt_regs and may cause breakage.

Right, your changelog said so ;-)

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