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Subject[patch 1/2] x86: cleanup alternative.h
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@polymtl.ca>
CC: 'Ingo Molnar' <mingo@elte.hu>
CC: H. Peter Anvin <hpa@zytor.com>
CC: Andi Kleen <andi@firstfloor.org>
CC: Andrew Morton <akpm@linux-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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