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

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Message-ID: <alpine.LNX.2.00.1505222317370.13817@pobox.suse.cz>
Date:	Fri, 22 May 2015 23:18:57 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
cc:	Borislav Petkov <bp@...en8.de>, 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 Fri, 22 May 2015, Josh Poimboeuf wrote:

> Hm, alternatives do complicate things a bit.  It *is* a false positive,
> but not necessarily because its part of an alternative instruction
> block.
> 
> The above code would be patched into memmove(), which is a leaf function
> because it doesn't call any other functions.  Leaf functions don't need
> frame pointer logic, so we can ignore them.
> 
> If instead the above code were patched into a non-leaf function, we'd
> have to change it to restore the frame pointer before returning.

Is this really only a problem of alternatives? How about 
dynamically-enabled tracepoints?

-- 
Jiri Kosina
SUSE Labs
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