linux-kernel - Re: [PATCH] crypto: sm4 - Do not change section of ck and sbox

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Date:   Thu, 26 Aug 2021 14:25:45 +0800
From:   Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
To:     Nathan Chancellor <nathan@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com, llvm@...ts.linux.dev
Subject: Re: [PATCH] crypto: sm4 - Do not change section of ck and sbox

Hi Nathan,

Thanks for pointing it out.

On 8/26/21 4:38 AM, Nathan Chancellor wrote:
> When building with clang and GNU as, there is a warning about ignored
> changed section attributes:
> 
> /tmp/sm4-c916c8.s: Assembler messages:
> /tmp/sm4-c916c8.s:677: Warning: ignoring changed section attributes for
> .data..cacheline_aligned
> 
> "static const" places the data in .rodata but __cacheline_aligned has
> the section attribute to place it in .data..cacheline_aligned, in
> addition to the aligned attribute.
> 
> To keep the alignment but avoid attempting to change sections, use the
> ____cacheline_aligned attribute, which is just the aligned attribute.
> 
> Fixes: 2b31277af577 ("crypto: sm4 - create SM4 library based on sm4 generic code")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1441
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>


Reviewed-by: Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>

Best regards,
Tianjia

> ---
>   lib/crypto/sm4.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/crypto/sm4.c b/lib/crypto/sm4.c
> index 633b59fed9db..284e62576d0c 100644
> --- a/lib/crypto/sm4.c
> +++ b/lib/crypto/sm4.c
> @@ -15,7 +15,7 @@ static const u32 fk[4] = {
>   	0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc
>   };
>   
> -static const u32 __cacheline_aligned ck[32] = {
> +static const u32 ____cacheline_aligned ck[32] = {
>   	0x00070e15, 0x1c232a31, 0x383f464d, 0x545b6269,
>   	0x70777e85, 0x8c939aa1, 0xa8afb6bd, 0xc4cbd2d9,
>   	0xe0e7eef5, 0xfc030a11, 0x181f262d, 0x343b4249,
> @@ -26,7 +26,7 @@ static const u32 __cacheline_aligned ck[32] = {
>   	0x10171e25, 0x2c333a41, 0x484f565d, 0x646b7279
>   };
>   
> -static const u8 __cacheline_aligned sbox[256] = {
> +static const u8 ____cacheline_aligned sbox[256] = {
>   	0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7,
>   	0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05,
>   	0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3,
> 
> base-commit: abfc7fad63940b8dfdfd25da6f0fa813d9561645
>