linux-kernel - Re: [PATCH 26/33] x86/kvm: Add stack frame dependency to test

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Date:	Fri, 22 Jan 2016 10:02:45 -0600
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
	Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pedro Alves <palves@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Bernd Petrovitsch <bernd@...rovitsch.priv.at>,
	Chris J Arges <chris.j.arges@...onical.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Gleb Natapov <gleb@...nel.org>, kvm@...r.kernel.org
Subject: Re: [PATCH 26/33] x86/kvm: Add stack frame dependency to test_cc()
 inline asm

On Fri, Jan 22, 2016 at 11:05:06AM +0100, Paolo Bonzini wrote:
> 
> 
> On 21/01/2016 23:49, Josh Poimboeuf wrote:
> > With some configs, gcc doesn't inline test_cc().  When that happens, it
> > doesn't create a stack frame before inserting the call instruction.
> > This breaks frame pointer convention if CONFIG_FRAME_POINTER is enabled
> > and can result in a bad stack trace.
> > 
> > Force a stack frame to be created if CONFIG_FRAME_POINTER is enabled by
> > listing the stack pointer as an output operand for the inline asm
> > statement.
> 
> If an __always_inline allocation works, that would be better.

Yeah, that seems to work.  I'll update the patch.

-- 
Josh