Re: [PATCH] perf/x86: fix broken LBR fixup code
From: Arun Sharma
Date: Mon Jun 11 2012 - 15:41:11 EST
On 6/11/12 6:47 AM, Peter Zijlstra wrote:
On Mon, 2012-06-11 at 15:44 +0200, Stephane Eranian wrote:
I noticed that the LBR fixups were not working anymore
on programs where they used to. I tracked this down to
a recent change to copy_from_user_nmi().
commit db0dc75d6403b6663c0eab4c6ccb672eb9b2ed72
Author: Arun Sharma<asharma@xxxxxx>
Date: Fri Apr 20 15:41:36 2012 -0700
perf/x86: Check user address explicitly in copy_from_user_nmi()
This commit added a call to __range_not_ok() to the
copy_from_user_nmi() routine. The problem is that the logic
of the test must be reversed. __range_not_ok() returns 0 if the
range is VALID. We want to return early from copy_from_user_nmi()
if the range is NOT valid.
D'0h.. Thanks!
My bad. I was fooled by all the kernel addresses that were unwound
properly. Didn't notice the broken unwinding in user space before I sent
the patch. The fix looks good. Thanks.
-Arun
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