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 20:36:14 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	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 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.

---
 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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