1 files changed, 52 insertions, 1 deletions

diff --git a/arch/x86/include/asm/alternative-asm.h b/arch/x86/include/asm/alternative-asm.h
index 372231c22a47..bdf02eeee765 100644
--- a/arch/x86/include/asm/alternative-asm.h
+++ b/arch/x86/include/asm/alternative-asm.h
@@ -18,12 +18,63 @@
         .endm
 #endif
 
-.macro altinstruction_entry orig alt feature orig_len alt_len
+.macro altinstruction_entry orig alt feature orig_len alt_len pad_len
         .long \orig - .
         .long \alt - .
         .word \feature
         .byte \orig_len
         .byte \alt_len
+        .byte \pad_len
+.endm
+
+.macro ALTERNATIVE oldinstr, newinstr, feature
+140:
+        \oldinstr
+141:
+        .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
+142:
+
+        .pushsection .altinstructions,"a"
+        altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f,142b-141b
+        .popsection
+
+        .pushsection .altinstr_replacement,"ax"
+143:
+        \newinstr
+144:
+        .popsection
+.endm
+
+#define old_len                 141b-140b
+#define new_len1                144f-143f
+#define new_len2                145f-144f
+
+/*
+ * max without conditionals. Idea adapted from:
+ * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
+ */
+#define alt_max_short(a, b)     ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
+
+.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
+140:
+        \oldinstr
+141:
+        .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \
+                (alt_max_short(new_len1, new_len2) - (old_len)),0x90
+142:
+
+        .pushsection .altinstructions,"a"
+        altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f,142b-141b
+        altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f,142b-141b
+        .popsection
+
+        .pushsection .altinstr_replacement,"ax"
+143:
+        \newinstr1
+144:
+        \newinstr2
+145:
+        .popsection
 .endm
 
 #endif  /*  __ASSEMBLY__  */