linux-kernel - Re: [PATCH] x86/alternatives: check int3 breakpoint physical addresses

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Message-ID: <alpine.DEB.2.21.1902102221500.8784@nanos.tec.linutronix.de>
Date:   Sun, 10 Feb 2019 22:23:45 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Alexandre Chartre <alexandre.chartre@...cle.com>
cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] x86/alternatives: check int3 breakpoint physical
 addresses

On Fri, 25 Jan 2019, Alexandre Chartre wrote:
> Note that this issue has been observed and reproduced with a custom kernel
> with some code mapped to different virtual addresses and using jump labels
> As jump labels use text_poke_bp(), crashes were sometimes observed when
> updating jump labels.

Rightfully so. text_poke_bp() pokes at the kernels text mapping which is
very well defined and unique. Why would you map the same text to different
virtual addresses and then use a randomly chosen one to poke at it?

Thanks,

	tglx