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Date: Wed, 29 Apr 2009 02:22:22 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To: mingo@...hat.com
Cc: linux-kernel@...r.kernel.org, hpa@...or.com, tglx@...utronix.de,
mingo@...e.hu, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/asm] x86: clean up alternative.h
* tip-bot for Mathieu Desnoyers (mathieu.desnoyers@...ymtl.ca) wrote:
> Commit-ID: edc953fa4ebc0265ef3b1754fe116a9fd4264e15
> Gitweb: http://git.kernel.org/tip/edc953fa4ebc0265ef3b1754fe116a9fd4264e15
> Author: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> AuthorDate: Tue, 28 Apr 2009 11:13:46 -0400
> Committer: Ingo Molnar <mingo@...e.hu>
> CommitDate: Tue, 28 Apr 2009 17:42:08 +0200
>
> x86: clean up 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.
>
> (v2: tab alignment fixes)
>
> [ Impact: cleanup ]
>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
> LKML-Reference: <20090428151346.GA31212@...stal>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
>
>
> ---
> arch/x86/include/asm/alternative.h | 59 ++++++++++++++----------------------
> 1 files changed, 23 insertions(+), 36 deletions(-)
>
> diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
> index f6aa18e..1a37bcd 100644
> --- a/arch/x86/include/asm/alternative.h
> +++ b/arch/x86/include/asm/alternative.h
> @@ -3,6 +3,7 @@
>
> #include <linux/types.h>
> #include <linux/stddef.h>
> +#include <linux/stringify.h>
> #include <asm/asm.h>
>
> /*
> @@ -74,6 +75,22 @@ static inline void alternatives_smp_switch(int smp) {}
>
> 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 */ \
I posted an updated v3 this morning which removes the "tab" before each
of these .byte, as requested by Peter.
Mathieu
> + ".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 +104,7 @@ const unsigned char *const *find_nop_table(void);
> * 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 +115,16 @@ const unsigned char *const *find_nop_table(void);
> * 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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