linux-kernel - Re: [PATCH 3/4] x86: open-code register save/restore in trace

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Message-ID: <CAK1hOcMqqcp=-4Q49VqcO1kNFdvaNy0H6PiUfKyknE2hjQmkrw@mail.gmail.com>
Date:	Sat, 10 Jan 2015 23:03:04 +0100
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	Frederic Weisbecker <fweisbec@...il.com>,
	X86 ML <x86@...nel.org>, Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 3/4] x86: open-code register save/restore in
 trace_hardirqs thunks

On Sat, Jan 10, 2015 at 11:00 PM, Borislav Petkov <bp@...en8.de> wrote:
>> --- a/arch/x86/lib/thunk_64.S
>> +++ b/arch/x86/lib/thunk_64.S
>> @@ -17,9 +17,27 @@
>>       CFI_STARTPROC
>>
>>       /* this one pushes 9 elems, the next one would be %rIP */
>> -     SAVE_ARGS
>> +     pushq_cfi %rdi
>> +     CFI_REL_OFFSET rdi, 0
>
> Btw, why the second CFI annotation?
>
> pushq_cfi does already CFI_ADJUST_CFA_OFFSET 8. Can't we use one and
> hide it in the macro?

We probably should.

Since thunk_32.S uses the very same construct, I think it should be fixed
in both files by one patch.
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