linux-kernel - Re: [tip:x86/asm] x86/asm/entry/64: Use better label name, fix comments

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Message-ID: <20150327121521.GC18927@pd.tnic>
Date:	Fri, 27 Mar 2015 13:15:21 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	ast@...mgrid.com, dvlasenk@...hat.com, luto@...capital.net,
	fweisbec@...il.com, linux-kernel@...r.kernel.org, wad@...omium.org,
	rostedt@...dmis.org, oleg@...hat.com, mingo@...nel.org,
	torvalds@...ux-foundation.org, hpa@...or.com,
	keescook@...omium.org, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/asm] x86/asm/entry/64: Use better label name, fix
 comments

On Fri, Mar 27, 2015 at 04:46:44AM -0700, tip-bot for Denys Vlasenko wrote:
> Commit-ID:  146b2b097d7a322b64b88a927fc5d870fc79a60b
> Gitweb:     http://git.kernel.org/tip/146b2b097d7a322b64b88a927fc5d870fc79a60b
> Author:     Denys Vlasenko <dvlasenk@...hat.com>
> AuthorDate: Wed, 25 Mar 2015 18:18:13 +0100
> Committer:  Ingo Molnar <mingo@...nel.org>
> CommitDate: Fri, 27 Mar 2015 09:57:05 +0100
> 
> x86/asm/entry/64: Use better label name, fix comments
> 
> A named label "ret_from_sys_call" implies that there are jumps
> to this location from elsewhere, as happens with many other
> labels in this file.
> 
> But this label is used only by the JMP a few insns above.
> To make that obvious, use local numeric label instead.
> 
> Improve comments:
> 
> "and return regs->ax" isn't too informative. We always return
> regs->ax.
> 
> The comment suggesting that it'd be cool to use rip relative
> addressing for CALL is deleted. It's unclear why that would be
> an improvement - we aren't striving to use position-independent
> code here. PIC code here would require something like LEA
> sys_call_table(%rip),reg + CALL *(reg,%rax*8)...
> 
> "iret frame is also incomplete" is no longer true, fix that too.
> 
> Also fix typo in comment.
> 
> Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
> Cc: Alexei Starovoitov <ast@...mgrid.com>
> Cc: Andy Lutomirski <luto@...capital.net>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: H. Peter Anvin <hpa@...or.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Will Drewry <wad@...omium.org>
> Link: http://lkml.kernel.org/r/1427303896-24023-1-git-send-email-dvlasenk@redhat.com
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> ---
>  arch/x86/kernel/entry_64.S | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)

Shouldn't you take v2 of that one?

https://lkml.kernel.org/r/1427307629-10024-1-git-send-email-dvlasenk@redhat.com

v2 is missing this hunk though:

---
@@ -1407,7 +1406,7 @@ ENTRY(nmi)
         * NMI.
         */

-       /* Use %rdx as out temp variable throughout */
+       /* Use %rdx as our temp variable throughout */
        pushq_cfi %rdx
        CFI_REL_OFFSET rdx, 0
--

I blame Denys for sending too many patches! :)

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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