linux-kernel - Re: linux-next: manual merge of the xen-tip tree with the tip tree

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Date:	Wed, 12 Aug 2015 14:44:52 -0400
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>
CC:	Stephen Rothwell <sfr@...b.auug.org.au>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Xen Devel <Xen-devel@...ts.xensource.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, linux-next@...r.kernel.org,
	linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
	David Vrabel <david.vrabel@...rix.com>
Subject: Re: linux-next: manual merge of the xen-tip tree with the tip tree

On 08/12/2015 02:36 PM, Peter Zijlstra wrote:
> On Wed, Aug 12, 2015 at 11:26:41AM -0700, H. Peter Anvin wrote:
>> One option might be to do the addition in assembly, i.e.:
>>
>> "i" (key), "i" (index)
>>
>> ... and put the addition into the assembly source.
> Like so? Seems to build on gcc-4.6.

Yes, this builds on 4.4.4. as well.

-boris

>
> ---
>   arch/x86/include/asm/jump_label.h | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
> index 28d7a857f9d1..5daeca3d0f9e 100644
> --- a/arch/x86/include/asm/jump_label.h
> +++ b/arch/x86/include/asm/jump_label.h
> @@ -22,9 +22,9 @@ static __always_inline bool arch_static_branch(struct static_key *key, bool bran
>   		".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t"
>   		".pushsection __jump_table,  \"aw\" \n\t"
>   		_ASM_ALIGN "\n\t"
> -		_ASM_PTR "1b, %l[l_yes], %c0 \n\t"
> +		_ASM_PTR "1b, %l[l_yes], %c0 + %c1 \n\t"
>   		".popsection \n\t"
> -		: :  "i" (&((char *)key)[branch]) : : l_yes);
> +		: :  "i" (key), "i" (branch) : : l_yes);
>   
>   	return false;
>   l_yes:
> @@ -38,9 +38,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, bool
>   		"2:\n\t"
>   		".pushsection __jump_table,  \"aw\" \n\t"
>   		_ASM_ALIGN "\n\t"
> -		_ASM_PTR "1b, %l[l_yes], %c0 \n\t"
> +		_ASM_PTR "1b, %l[l_yes], %c0 + %c1 \n\t"
>   		".popsection \n\t"
> -		: :  "i" (&((char *)key)[branch]) : : l_yes);
> +		: :  "i" (key), "i" (branch) : : l_yes);
>   
>   	return false;
>   l_yes:

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