From: Arun Sharma <asharma@fb.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>,
<linux-kernel@vger.kernel.org>, <mingo@elte.hu>
Subject: Re: [PATCH] perf/x86: fix broken LBR fixup code
Date: Mon, 11 Jun 2012 12:41:03 -0700 [thread overview]
Message-ID: <4FD649CF.5020300@fb.com> (raw)
In-Reply-To: <1339422464.30462.17.camel@twins>
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@fb.com>
>> 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
next prev parent reply other threads:[~2012-06-11 19:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-11 13:44 [PATCH] perf/x86: fix broken LBR fixup code Stephane Eranian
2012-06-11 13:47 ` Peter Zijlstra
2012-06-11 19:41 ` Arun Sharma [this message]
2012-06-14 8:40 ` [tip:perf/urgent] perf/x86: Fix " tip-bot for Stephane Eranian
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