linux-kernel - Re: [PATCH 4/6] x86: entry_64.S: fold test_in

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Date:	Mon, 23 Feb 2015 16:34:15 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Denys Vlasenko <dvlasenk@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	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>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/6] x86: entry_64.S: fold test_in_nmi macro into its only user

On Mon, Feb 23, 2015 at 4:12 PM, Denys Vlasenko <dvlasenk@...hat.com> wrote:
> No code changes.

This needs to address Steven's comments, I think, and I'd like his ack, too.

--Andy

>
> Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
> CC: Linus Torvalds <torvalds@...ux-foundation.org>
> CC: Oleg Nesterov <oleg@...hat.com>
> CC: Borislav Petkov <bp@...en8.de>
> CC: "H. Peter Anvin" <hpa@...or.com>
> CC: Andy Lutomirski <luto@...capital.net>
> CC: Frederic Weisbecker <fweisbec@...il.com>
> CC: X86 ML <x86@...nel.org>
> CC: Alexei Starovoitov <ast@...mgrid.com>
> CC: Will Drewry <wad@...omium.org>
> CC: Kees Cook <keescook@...omium.org>
> CC: linux-kernel@...r.kernel.org
> ---
>  arch/x86/kernel/entry_64.S | 24 +++++++++---------------
>  1 file changed, 9 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
> index 03498d0..c628a1b 100644
> --- a/arch/x86/kernel/entry_64.S
> +++ b/arch/x86/kernel/entry_64.S
> @@ -1378,19 +1378,7 @@ ENTRY(error_exit)
>         CFI_ENDPROC
>  END(error_exit)
>
> -/*
> - * Test if a given stack is an NMI stack or not.
> - */
> -       .macro test_in_nmi reg stack nmi_ret normal_ret
> -       cmpq %\reg, \stack
> -       ja \normal_ret
> -       subq $EXCEPTION_STKSZ, %\reg
> -       cmpq %\reg, \stack
> -       jb \normal_ret
> -       jmp \nmi_ret
> -       .endm
> -
> -       /* runs on exception stack */
> +/* Runs on exception stack */
>  ENTRY(nmi)
>         INTR_FRAME
>         PARAVIRT_ADJUST_EXCEPTION_FRAME
> @@ -1451,8 +1439,14 @@ ENTRY(nmi)
>          * We check the variable because the first NMI could be in a
>          * breakpoint routine using a breakpoint stack.
>          */
> -       lea 6*8(%rsp), %rdx
> -       test_in_nmi rdx, 4*8(%rsp), nested_nmi, first_nmi
> +       lea     6*8(%rsp), %rdx
> +       cmpq    %rdx, 4*8(%rsp)
> +       ja      first_nmi
> +       subq    $EXCEPTION_STKSZ, %rdx
> +       cmpq    %rdx, 4*8(%rsp)
> +       jb      first_nmi
> +       jmp     nested_nmi
> +
>         CFI_REMEMBER_STATE
>
>  nested_nmi:
> --
> 1.8.1.4
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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