Message-ID: <556E111F.50000@redhat.com>
Date: Tue, 02 Jun 2015 22:25:03 +0200
From: Denys Vlasenko <dvlasenk@redhat.com>
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To: Steven Rostedt <rostedt@goodmis.org>
CC: Ingo Molnar <mingo@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
        Andy Lutomirski <luto@amacapital.net>, Oleg Nesterov <oleg@redhat.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Alexei Starovoitov <ast@plumgrid.com>, Will Drewry <wad@chromium.org>,
        Kees Cook <keescook@chromium.org>, x86@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] x86/asm/entry/32: Open-code CLEAR_RREGS. No code
 changes.
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On 06/02/2015 09:34 PM, Steven Rostedt wrote:
> On Tue,  2 Jun 2015 21:04:01 +0200
> Denys Vlasenko <dvlasenk@redhat.com> wrote:
> 
>> This macro is small, has only four callsites, and one of them is
>> slightly different using a conditional parameter.
>>
>> A few saved lines aren't worth the resulting obfuscation.
> 
> I'm curious, why? Did someone recommend this change?

I'm proposing to do this. Of course, I don't expect that
any my patch must be accepted.


> I don't see it as obfuscation at all.

Riddle me this, looking at the current code. What's up with that
strange manipulations of %r9 register? Why the code in
SYSCALL and SYSENTER entry points is not the same,
why "r9 dance" is done only in one of these entry points?

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