linux-kernel - Re: [PATCH 5/5] x86, head_32: Remove an old gcc2 fix

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Date:	Sat, 09 Feb 2013 14:23:36 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>, Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH 5/5] x86, head_32: Remove an old gcc2 fix

On 02/09/2013 01:23 PM, Borislav Petkov wrote:
> On Sat, Feb 09, 2013 at 12:52:01PM -0800, H. Peter Anvin wrote:
>> However... DF should have been cleared long before this...
>
> How about we do this at the beginning of default_entry where we clear
> EFLAGS too:
>
> diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
> index fc56613224c3..8b2a8a824fc6 100644
> --- a/arch/x86/kernel/head_32.S
> +++ b/arch/x86/kernel/head_32.S
> @@ -322,10 +322,11 @@ default_entry:
>    * debugger if this code is traced. Best to initialize before switching to
>    * protected mode.
>    */
> -
>   	pushl $0
>   	popfl
>
> +	cld				# GCC wants DF=0 at all times
> +

The pushfl/popfl sequence clears DF too...

	-hpa


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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