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

Borislav Petkov
2015-03-27T12:17:13Z

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@redhat.com>
> AuthorDate: Wed, 25 Mar 2015 18:18:13 +0100
> Committer: Ingo Molnar <mingo@kernel.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@redhat.com>
> Cc: Alexei Starovoitov <ast@plumgrid.com>
> Cc: Andy Lutomirski <luto@amacapital.net>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Oleg Nesterov <oleg@redhat.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Will Drewry <wad@chromium.org>
> Link: http://lkml.kernel.org/r/1427303896-24023-1-git-send-email-dvlasenk@redhat.com
> Signed-off-by: Ingo Molnar <mingo@kernel.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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