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| author | James Morse <james.morse@arm.com> | 2015-07-21 13:23:30 +0100 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2015-07-27 11:08:41 +0100 |
| commit | 91a5cefa2f98bdd3404c2fba57048c4fa225cc37 (patch) | |
| tree | 269b9169b6427df0eca8f3883aa426a9dd98e6fe /arch | |
| parent | 18ffa046c509d0cd011eeea2c0418f2d014771fc (diff) | |
| download | linux-91a5cefa2f98bdd3404c2fba57048c4fa225cc37.tar.gz linux-91a5cefa2f98bdd3404c2fba57048c4fa225cc37.tar.bz2 linux-91a5cefa2f98bdd3404c2fba57048c4fa225cc37.zip | |
arm64: kernel: Add optional CONFIG_ parameter to ALTERNATIVE()
Some uses of ALTERNATIVE() may depend on a feature that is disabled at
compile time by a Kconfig option. In this case the unused alternative
instructions waste space, and if the original instruction is a nop, it
wastes time and space.
This patch adds an optional 'config' option to ALTERNATIVE() and
alternative_insn that allows the compiler to remove both the original
and alternative instructions if the config option is not defined.
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/include/asm/alternative.h | 28 |
1 files changed, 25 insertions, 3 deletions
diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h index e86681ad0931..20367882226c 100644 --- a/arch/arm64/include/asm/alternative.h +++ b/arch/arm64/include/asm/alternative.h @@ -3,6 +3,7 @@ #ifndef __ASSEMBLY__ +#include <linux/kconfig.h> #include <linux/types.h> #include <linux/stddef.h> #include <linux/stringify.h> @@ -40,7 +41,8 @@ void free_alternatives_memory(void); * be fixed in a binutils release posterior to 2.25.51.0.2 (anything * containing commit 4e4d08cf7399b606 or c1baaddf8861). */ -#define ALTERNATIVE(oldinstr, newinstr, feature) \ +#define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \ + ".if "__stringify(cfg_enabled)" == 1\n" \ "661:\n\t" \ oldinstr "\n" \ "662:\n" \ @@ -53,7 +55,11 @@ void free_alternatives_memory(void); "664:\n\t" \ ".popsection\n\t" \ ".org . - (664b-663b) + (662b-661b)\n\t" \ - ".org . - (662b-661b) + (664b-663b)\n" + ".org . - (662b-661b) + (664b-663b)\n" \ + ".endif\n" + +#define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \ + __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg)) #else @@ -65,7 +71,8 @@ void free_alternatives_memory(void); .byte \alt_len .endm -.macro alternative_insn insn1 insn2 cap +.macro alternative_insn insn1, insn2, cap, enable = 1 + .if \enable 661: \insn1 662: .pushsection .altinstructions, "a" altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f @@ -75,6 +82,7 @@ void free_alternatives_memory(void); 664: .popsection .org . - (664b-663b) + (662b-661b) .org . - (662b-661b) + (664b-663b) + .endif .endm /* @@ -118,6 +126,20 @@ void free_alternatives_memory(void); .org . - (662b-661b) + (664b-663b) .endm +#define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \ + alternative_insn insn1, insn2, cap, IS_ENABLED(cfg) + + #endif /* __ASSEMBLY__ */ +/* + * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature)); + * + * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO)); + * N.B. If CONFIG_FOO is specified, but not selected, the whole block + * will be omitted, including oldinstr. + */ +#define ALTERNATIVE(oldinstr, newinstr, ...) \ + _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1) + #endif /* __ASM_ALTERNATIVE_H */ |