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authorJames Morse <james.morse@arm.com>2015-07-21 13:23:30 +0100
committerDavid Brown <david.brown@linaro.org>2015-12-03 16:53:51 -0800
commit9aaa9a81735a9a324dfd53d68532c9fa89aaf2af (patch)
treec99c075e2ba96524bb4ef0a6ba41bc6c78ad379c
parentce88966224d3f9ed4a2b83c694e535999a40e6d5 (diff)
downloadlinux-linaro-stable-9aaa9a81735a9a324dfd53d68532c9fa89aaf2af.tar.gz
arm64: kernel: Add optional CONFIG_ parameter to ALTERNATIVE()
commit 91a5cefa2f98bdd3404c2fba57048c4fa225cc37 upstream. 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> Signed-off-by: David Brown <david.brown@linaro.org>
-rw-r--r--arch/arm64/include/asm/alternative.h28
1 files changed, 25 insertions, 3 deletions
diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
index c4243a4a6c14..4e3d4c8b50d1 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>
@@ -39,7 +40,8 @@ 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" \
@@ -52,7 +54,11 @@ 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
@@ -64,7 +70,8 @@ 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
@@ -74,6 +81,7 @@ void free_alternatives_memory(void);
664: .popsection
.org . - (664b-663b) + (662b-661b)
.org . - (662b-661b) + (664b-663b)
+ .endif
.endm
/*
@@ -117,6 +125,20 @@ 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 */