linux-kernel - Re: [PATCH v4 0/3] Compile-time stack frame pointer validation

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Message-ID: <20150521220158.GH3689@pd.tnic>
Date:	Fri, 22 May 2015 00:01:58 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Brian Gerst <brgerst@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v4 0/3] Compile-time stack frame pointer validation

On Thu, May 21, 2015 at 03:54:25PM -0500, Josh Poimboeuf wrote:
> stackvalidate: arch/x86/lib/memmove_64.o: return instruction outside of a function at .altinstr_replacement+0x5

That must be something like this:

0000000000000000 <.altinstr_replacement>:
   0:   48 89 d1                mov    %rdx,%rcx
   3:   f3 a4                   rep movsb %ds:(%rsi),%es:(%rdi)
   5:   c3                      retq

right?

In any case, anything with alternatives is probably a false positive
because even if instructions appear outside of the containing function,
they get patched in and are actually inside. Jump offsets get fixed up
properly too. Should, at least :-)

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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