linux-kernel - Re: [PATCH 04/13] x86/crypto/aesni-intel_avx: Standardize stack alignment prologue

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Message-ID: <YDdwK8aPnc6X9WTB@hirez.programming.kicks-ass.net>
Date:   Thu, 25 Feb 2021 10:38:51 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     x86@...nel.org, Herbert Xu <herbert@...dor.apana.org.au>,
        linux-kernel@...r.kernel.org, Miroslav Benes <mbenes@...e.cz>,
        Eric Biggers <ebiggers@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        linux-crypto@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH 04/13] x86/crypto/aesni-intel_avx: Standardize stack
 alignment prologue

On Wed, Feb 24, 2021 at 10:29:17AM -0600, Josh Poimboeuf wrote:
> Use RBP instead of R14 for saving the old stack pointer before
> realignment.  This resembles what compilers normally do.
> 
> This enables ORC unwinding by allowing objtool to understand the stack
> realignment.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> ---
>  arch/x86/crypto/aesni-intel_avx-x86_64.S | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/crypto/aesni-intel_avx-x86_64.S b/arch/x86/crypto/aesni-intel_avx-x86_64.S
> index 188f1848a730..98e3552b6e03 100644
> --- a/arch/x86/crypto/aesni-intel_avx-x86_64.S
> +++ b/arch/x86/crypto/aesni-intel_avx-x86_64.S
> @@ -251,22 +251,20 @@ VARIABLE_OFFSET = 16*8
>  .macro FUNC_SAVE
>          push    %r12
>          push    %r13
> -        push    %r14
>          push    %r15
>  
> -        mov     %rsp, %r14
> -
> -
> +	push	%rbp
> +	mov	%rsp, %rbp
>  
>          sub     $VARIABLE_OFFSET, %rsp
>          and     $~63, %rsp                    # align rsp to 64 bytes
>  .endm
>  
>  .macro FUNC_RESTORE
> -        mov     %r14, %rsp
> +        mov     %rbp, %rsp
> +	pop	%rbp
>  
>          pop     %r15
> -        pop     %r14
>          pop     %r13
>          pop     %r12
>  .endm

Urgh, I was about to say your patch is whitespace damaged, but it's the
original file :-/