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Message-ID: <4FD649CF.5020300@fb.com> Date: Mon, 11 Jun 2012 12:41:03 -0700 From: Arun Sharma <asharma@...com> To: Peter Zijlstra <peterz@...radead.org> CC: Stephane Eranian <eranian@...gle.com>, <linux-kernel@...r.kernel.org>, <mingo@...e.hu> Subject: Re: [PATCH] perf/x86: fix broken LBR fixup code 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@...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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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