linux-kernel - Re: [PATCH] x86/asm/entry: fix stack return address retrieval in thunk

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Date:	Tue, 17 May 2016 12:25:11 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Alex Thorlton <athorlton@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...nel.org>,
	Denys Vlasenko <dvlasenk@...hat.com>
Subject: Re: [PATCH] x86/asm/entry: fix stack return address retrieval in
 thunk

On Tue, May 17, 2016 at 12:51:41PM -0400, Steven Rostedt wrote:
> On Tue, 17 May 2016 09:31:12 -0700
> Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
> > Considering that we got this wrong in two places, it's clearly too
> > subtle for our little brains as-is.
> 
> And did we only get this wrong in two places? That is, do we really
> know how little our brains really are?

I've looked again at all the other users of FRAME_BEGIN, and this
pattern of a callee attempting to access the caller's stack is pretty
rare in x86_64 (which is the main user of the macro).  My little brain
is telling me there are no more bugs.

-- 
Josh