[PATCH] x86_64: Support alternative() with a output argument.

Needed for follow on patches

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/include/asm-x86_64/system.h b/include/asm-x86_64/system.h
index a3bca7552e14..80272190570e 100644
--- a/include/asm-x86_64/system.h
+++ b/include/asm-x86_64/system.h
@@ -137,6 +137,21 @@ struct alt_instr {
                       "663:\n\t" newinstr "\n664:\n"   /* replacement */ \
                       ".previous" :: "i" (feature), ##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"               \
+                      "  .align 8\n"                                    \
+                      "  .quad 661b\n"            /* label */           \
+                      "  .quad 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)
+
 /*
  * Clear and set 'TS' bit respectively
  */