Re: [PATCH 4/6] x86: entry_64.S: fold test_in_nmi macro into its only user

[Andy Lutomirski]

On Mon, Feb 23, 2015 at 4:12 PM, Denys Vlasenko <dvlasenk@xxxxxxxxxx> 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@xxxxxxxxxx>
> CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> CC: Oleg Nesterov <oleg@xxxxxxxxxx>
> CC: Borislav Petkov <bp@xxxxxxxxx>
> CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
> CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> CC: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> CC: X86 ML <x86@xxxxxxxxxx>
> CC: Alexei Starovoitov <ast@xxxxxxxxxxxx>
> CC: Will Drewry <wad@xxxxxxxxxxxx>
> CC: Kees Cook <keescook@xxxxxxxxxxxx>
> CC: linux-kernel@xxxxxxxxxxxxxxx
> ---
>  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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