linux-kernel - Re: [tip:perf/core] kprobes/x86: Call out into INT3 handler directly instead of using notifier

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Message-ID: <51EFE5A8.1060109@linux.intel.com>
Date:	Wed, 24 Jul 2013 07:33:12 -0700
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	mingo@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org,
	jkosina@...e.cz, masami.hiramatsu.pt@...achi.com,
	rostedt@...dmis.org, tglx@...utronix.de, hpa@...ux.intel.com,
	fengguang.wu@...el.com
CC:	tip-bot for Jiri Kosina <tipbot@...or.com>,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/core] kprobes/x86: Call out into INT3 handler directly
 instead of using notifier

On 07/23/2013 08:55 PM, tip-bot for Jiri Kosina wrote:
> Commit-ID:  17f41571bb2c4a398785452ac2718a6c5d77180e
> Gitweb:     http://git.kernel.org/tip/17f41571bb2c4a398785452ac2718a6c5d77180e
> Author:     Jiri Kosina <jkosina@...e.cz>
> AuthorDate: Tue, 23 Jul 2013 10:09:28 +0200
> Committer:  Ingo Molnar <mingo@...nel.org>
> CommitDate: Tue, 23 Jul 2013 10:12:57 +0200
> 
> kprobes/x86: Call out into INT3 handler directly instead of using notifier
> 
> In fd4363fff3d96 ("x86: Introduce int3 (breakpoint)-based
> instruction patching"), the mechanism that was introduced for
> notifying alternatives code from int3 exception handler that and
> exception occured was die_notifier.
> 
> This is however problematic, as early code might be using jump
> labels even before the notifier registration has been performed,
> which will then lead to an oops due to unhandled exception. One
> of such occurences has been encountered by Fengguang:
> 

Please note that putting this patch in perf/core means x86/jumplabel is
completely nonfunctional by itself.

	-hpa


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