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Date: Tue, 28 Apr 2009 09:05:01 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To: akpm@...ux-foundation.org, Ingo Molnar <mingo@...e.hu>,
linux-kernel@...r.kernel.org
Cc: "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <andi@...stfloor.org>
Subject: [GIT PULL] x86: cleanup alternative.h
Ingo, do you think the cleanup below would be worth merging ? It adds
the ability to use ALTERNATIVE() directly in gcc inline assembly _and_
cleans up the current alternative*() cut-and-paste coding style. :)
So unless someone can spot any kind of serious drawback with it, I think
this cleanup patch should be pulled.
Alternative header duplicates assembly that could be merged in one single macro.
Merging this into this macro also allows to directly declare ALTERNATIVE()
statements within assembly code.
Uses a __stringify() of the feature bits rather than passing a "i" operand.
Leave the old %0 operand as-is (set to 0), unused to stay compatible with API.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
CC: 'Ingo Molnar' <mingo@...e.hu>
CC: H. Peter Anvin <hpa@...or.com>
CC: Andi Kleen <andi@...stfloor.org>
CC: Andrew Morton <akpm@...ux-foundation.org>
---
arch/x86/include/asm/alternative.h | 58 ++++++++++++++-----------------------
1 file changed, 22 insertions(+), 36 deletions(-)
Index: linux-2.6-lttng/arch/x86/include/asm/alternative.h
===================================================================
--- linux-2.6-lttng.orig/arch/x86/include/asm/alternative.h 2009-04-22 16:14:23.000000000 -0400
+++ linux-2.6-lttng/arch/x86/include/asm/alternative.h 2009-04-22 16:17:48.000000000 -0400
@@ -3,6 +3,7 @@
#include <linux/types.h>
#include <linux/stddef.h>
+#include <linux/stringify.h>
#include <asm/asm.h>
/*
@@ -74,6 +75,21 @@ static inline void alternatives_smp_swit
const unsigned char *const *find_nop_table(void);
+/* alternative assembly primitive */
+#define ALTERNATIVE(oldinstr, newinstr, feature) \
+ "661:\n\t" oldinstr "\n662:\n" \
+ ".section .altinstructions,\"a\"\n" \
+ _ASM_ALIGN "\n" \
+ _ASM_PTR "661b\n" /* label */ \
+ _ASM_PTR "663f\n" /* new instruction */ \
+ " .byte " __stringify(feature) "\n" /* feature bit */ \
+ " .byte 662b-661b\n" /* sourcelen */ \
+ " .byte 664f-663f\n" /* replacementlen */ \
+ ".previous\n" \
+ ".section .altinstr_replacement,\"ax\"\n" \
+ "663:\n\t" newinstr "\n664:\n" /* replacement */ \
+ ".previous"
+
/*
* Alternative instructions for different CPU types or capabilities.
*
@@ -87,18 +103,7 @@ const unsigned char *const *find_nop_tab
* without volatile and memory clobber.
*/
#define alternative(oldinstr, newinstr, feature) \
- asm volatile ("661:\n\t" oldinstr "\n662:\n" \
- ".section .altinstructions,\"a\"\n" \
- _ASM_ALIGN "\n" \
- _ASM_PTR "661b\n" /* label */ \
- _ASM_PTR "663f\n" /* new instruction */ \
- " .byte %c0\n" /* feature bit */ \
- " .byte 662b-661b\n" /* sourcelen */ \
- " .byte 664f-663f\n" /* replacementlen */ \
- ".previous\n" \
- ".section .altinstr_replacement,\"ax\"\n" \
- "663:\n\t" newinstr "\n664:\n" /* replacement */ \
- ".previous" :: "i" (feature) : "memory")
+ asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
/*
* Alternative inline assembly with input.
@@ -109,35 +114,16 @@ const unsigned char *const *find_nop_tab
* Best is to use constraints that are fixed size (like (%1) ... "r")
* If you use variable sized constraints like "m" or "g" in the
* replacement make sure to pad to the worst case length.
+ * Leaving an unused argument 0 to keep API compatibility.
*/
#define alternative_input(oldinstr, newinstr, feature, input...) \
- asm volatile ("661:\n\t" oldinstr "\n662:\n" \
- ".section .altinstructions,\"a\"\n" \
- _ASM_ALIGN "\n" \
- _ASM_PTR "661b\n" /* label */ \
- _ASM_PTR "663f\n" /* new instruction */ \
- " .byte %c0\n" /* feature bit */ \
- " .byte 662b-661b\n" /* sourcelen */ \
- " .byte 664f-663f\n" /* replacementlen */ \
- ".previous\n" \
- ".section .altinstr_replacement,\"ax\"\n" \
- "663:\n\t" newinstr "\n664:\n" /* replacement */ \
- ".previous" :: "i" (feature), ##input)
+ asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
+ : : "i" (0), ## input)
/* Like alternative_input, but with a single output argument */
#define alternative_io(oldinstr, newinstr, feature, output, input...) \
- asm volatile ("661:\n\t" oldinstr "\n662:\n" \
- ".section .altinstructions,\"a\"\n" \
- _ASM_ALIGN "\n" \
- _ASM_PTR "661b\n" /* label */ \
- _ASM_PTR "663f\n" /* new instruction */ \
- " .byte %c[feat]\n" /* feature bit */ \
- " .byte 662b-661b\n" /* sourcelen */ \
- " .byte 664f-663f\n" /* replacementlen */ \
- ".previous\n" \
- ".section .altinstr_replacement,\"ax\"\n" \
- "663:\n\t" newinstr "\n664:\n" /* replacement */ \
- ".previous" : output : [feat] "i" (feature), ##input)
+ asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
+ : output : "i" (0), ## input)
/*
* use this macro(s) if you need more than one output parameter
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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