linux-kernel - Re: [PATCH 3/3] x86: do not save callee-preserved registers around lockdep_sys_exit

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Message-ID: <20150302084502.GE5029@twins.programming.kicks-ass.net>
Date:	Mon, 2 Mar 2015 09:45:02 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>, Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] x86: do not save callee-preserved registers around
 lockdep_sys_exit_thunk

On Sun, Mar 01, 2015 at 08:16:18AM -0800, Andy Lutomirski wrote:
> On Fri, Feb 27, 2015 at 4:29 PM, Denys Vlasenko <dvlasenk@...hat.com> wrote:
> > Internally, lockdep_sys_exit_thunk saves callee-clobbered registers,
> > and calls a C function, lockdep_sys_exix. Thus, callee-preserved
> > won't be mangled, there is no need to save them.
> >
> > Patch was run-tested.
> 
> Peterz, I think this was your code.

It was, I'm forever unsure on when what register are saved by which
macros/functions.

Thanks!
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