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

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Date:	Mon, 29 Jul 2013 11:06:53 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>
Cc:	mingo@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org,
	masami.hiramatsu.pt@...achi.com, rostedt@...dmis.org,
	tglx@...utronix.de, fengguang.wu@...el.com,
	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 Wed, 24 Jul 2013, H. Peter Anvin 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.

I'd like to point out that this is still the case ... TIA,

-- 
Jiri Kosina
SUSE Labs
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