linux-kernel - Re: [PATCH] x86/crc: add ANNOTATE_NOENDBR to suppress objtool warnings

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Message-ID: <Z7RII_fnk1d2nB3r@gmail.com>
Date: Tue, 18 Feb 2025 09:43:15 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Eric Biggers <ebiggers@...nel.org>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-crypto@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] x86/crc: add ANNOTATE_NOENDBR to suppress objtool
 warnings


* Eric Biggers <ebiggers@...nel.org> wrote:

> From: Eric Biggers <ebiggers@...gle.com>
> 
> The assembly functions generated by crc-pclmul-template.S are called
> only via static_call, so they do not need to begin with an endbr
> instruction.  But objtool still warns about a missing endbr by default.
> Add ANNOTATE_NOENDBR to suppress these warnings:
> 
>     vmlinux.o: warning: objtool: crc32_x86_init+0x1c0: relocation to !ENDBR: crc32_lsb_vpclmul_avx10_256+0x0
>     vmlinux.o: warning: objtool: crc64_x86_init+0x183: relocation to !ENDBR: crc64_msb_vpclmul_avx10_256+0x0
>     vmlinux.o: warning: objtool: crc_t10dif_x86_init+0x183: relocation to !ENDBR: crc16_msb_vpclmul_avx10_256+0x0
>     vmlinux.o: warning: objtool: __SCK__crc32_lsb_pclmul+0x0: data relocation to !ENDBR: crc32_lsb_pclmul_sse+0x0
>     vmlinux.o: warning: objtool: __SCK__crc64_lsb_pclmul+0x0: data relocation to !ENDBR: crc64_lsb_pclmul_sse+0x0
>     vmlinux.o: warning: objtool: __SCK__crc64_msb_pclmul+0x0: data relocation to !ENDBR: crc64_msb_pclmul_sse+0x0
>     vmlinux.o: warning: objtool: __SCK__crc16_msb_pclmul+0x0: data relocation to !ENDBR: crc16_msb_pclmul_sse+0x0
> 
> Fixes: 8d2d3e72e35b ("x86/crc: add "template" for [V]PCLMULQDQ based CRC functions")
> Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
> Closes: https://lore.kernel.org/r/20250217170555.3d14df62@canb.auug.org.au/
> Suggested-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> ---
> 
> This applies to
> https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=crc-next
> 
>  arch/x86/lib/crc-pclmul-template.S | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/x86/lib/crc-pclmul-template.S b/arch/x86/lib/crc-pclmul-template.S
> index dc91cc074b300..a19b730b642d3 100644
> --- a/arch/x86/lib/crc-pclmul-template.S
> +++ b/arch/x86/lib/crc-pclmul-template.S
> @@ -5,10 +5,11 @@
>  // Copyright 2025 Google LLC
>  //
>  // Author: Eric Biggers <ebiggers@...gle.com>
>  
>  #include <linux/linkage.h>
> +#include <linux/objtool.h>
>  
>  // Offsets within the generated constants table
>  .set OFFSETOF_BSWAP_MASK,			-5*16	// msb-first CRCs only
>  .set OFFSETOF_FOLD_ACROSS_2048_BITS_CONSTS,	-4*16	// must precede next
>  .set OFFSETOF_FOLD_ACROSS_1024_BITS_CONSTS,	-3*16	// must precede next
> @@ -270,10 +271,14 @@
>  	.set	BSWAP_MASK_XMM,	%xmm6
>  	.set	CONSTS,		V7
>  	.set	CONSTS_YMM,	%ymm7
>  	.set	CONSTS_XMM,	%xmm7
>  
> +	// Use ANNOTATE_NOENDBR to suppress an objtool warning, since the
> +	// functions generated by this macro are called only by static_call.
> +	ANNOTATE_NOENDBR

Acked-by: Ingo Molnar <mingo@...nel.org>

Thanks,

	Ingo