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@polymtl.ca>
LKML-Reference: <20090428151346.GA31212@Krystal>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index f6aa18e..1a37bcd 100644 (file)
--- 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  */   \
+      ".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