linux-kernel - Re: x86/boot: Avoid using Intel mnemonics in AT&T syntax asm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Y71NllA2NjlNiZpX@gmail.com>
Date:   Tue, 10 Jan 2023 12:35:50 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>
Subject: Re: x86/boot: Avoid using Intel mnemonics in AT&T syntax asm


* Peter Zijlstra <peterz@...radead.org> wrote:

> 
> With 'GNU assembler (GNU Binutils for Debian) 2.39.90.20221231' the
> build now reports:
> 
>   arch/x86/realmode/rm/../../boot/bioscall.S: Assembler messages:
>   arch/x86/realmode/rm/../../boot/bioscall.S:35: Warning: found `movsd'; assuming `movsl' was meant
>   arch/x86/realmode/rm/../../boot/bioscall.S:70: Warning: found `movsd'; assuming `movsl' was meant
> 
>   arch/x86/boot/bioscall.S: Assembler messages:
>   arch/x86/boot/bioscall.S:35: Warning: found `movsd'; assuming `movsl' was meant
>   arch/x86/boot/bioscall.S:70: Warning: found `movsd'; assuming `movsl' was meant
> 
> Which is due to:
> 
>   PR gas/29525
> 
>   Note that with the dropped CMPSD and MOVSD Intel Syntax string insn
>   templates taking operands, mixed IsString/non-IsString template groups
>   (with memory operands) cannot occur anymore. With that
>   maybe_adjust_templates() becomes unnecessary (and is hence being
>   removed).
> 
> More details: https://sourceware.org/bugzilla/show_bug.cgi?id=29525
> 
> Fixes: 7a734e7dd93b ("x86, setup: "glove box" BIOS calls -- infrastructure")
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  arch/x86/boot/bioscall.S |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> --- a/arch/x86/boot/bioscall.S
> +++ b/arch/x86/boot/bioscall.S
> @@ -32,7 +32,7 @@
>  	movw	%dx, %si
>  	movw	%sp, %di
>  	movw	$11, %cx
> -	rep; movsd
> +	rep; movsl
>  
>  	/* Pop full state from the stack */
>  	popal
> @@ -67,7 +67,7 @@
>  	jz	4f
>  	movw	%sp, %si
>  	movw	$11, %cx
> -	rep; movsd
> +	rep; movsl
>  4:	addw	$44, %sp

So I think the GAS change to introduce this warning was probably 
unnecessary - these instructions weren't really causing any trouble and the 
syntax was basically a legacy thing that shouldn't be touched - but I guess 
that argument is water down the bridge now:

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

Thanks,

	Ingo