x86, alternative: Use .pushsection/.popsection

.section/.previous doesn't nest.  Use .pushsection/.popsection in
<asm/alternative.h> so that they can be properly nested.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1348256595-29119-5-git-send-email-hpa@linux.intel.com
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 7078068..87bc00d 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -29,10 +29,10 @@
 
 #ifdef CONFIG_SMP
 #define LOCK_PREFIX_HERE \
-		".section .smp_locks,\"a\"\n"	\
-		".balign 4\n"			\
-		".long 671f - .\n" /* offset */	\
-		".previous\n"			\
+		".pushsection .smp_locks,\"a\"\n"	\
+		".balign 4\n"				\
+		".long 671f - .\n" /* offset */		\
+		".popsection\n"				\
 		"671:"
 
 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
@@ -99,30 +99,30 @@
 /* alternative assembly primitive: */
 #define ALTERNATIVE(oldinstr, newinstr, feature)			\
 	OLDINSTR(oldinstr)						\
-	".section .altinstructions,\"a\"\n"				\
+	".pushsection .altinstructions,\"a\"\n"				\
 	ALTINSTR_ENTRY(feature, 1)					\
-	".previous\n"							\
-	".section .discard,\"aw\",@progbits\n"				\
+	".popsection\n"							\
+	".pushsection .discard,\"aw\",@progbits\n"			\
 	DISCARD_ENTRY(1)						\
-	".previous\n"							\
-	".section .altinstr_replacement, \"ax\"\n"			\
+	".popsection\n"							\
+	".pushsection .altinstr_replacement, \"ax\"\n"			\
 	ALTINSTR_REPLACEMENT(newinstr, feature, 1)			\
-	".previous"
+	".popsection"
 
 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
 	OLDINSTR(oldinstr)						\
-	".section .altinstructions,\"a\"\n"				\
+	".pushsection .altinstructions,\"a\"\n"				\
 	ALTINSTR_ENTRY(feature1, 1)					\
 	ALTINSTR_ENTRY(feature2, 2)					\
-	".previous\n"							\
-	".section .discard,\"aw\",@progbits\n"				\
+	".popsection\n"							\
+	".pushsection .discard,\"aw\",@progbits\n"			\
 	DISCARD_ENTRY(1)						\
 	DISCARD_ENTRY(2)						\
-	".previous\n"							\
-	".section .altinstr_replacement, \"ax\"\n"			\
+	".popsection\n"							\
+	".pushsection .altinstr_replacement, \"ax\"\n"			\
 	ALTINSTR_REPLACEMENT(newinstr1, feature1, 1)			\
 	ALTINSTR_REPLACEMENT(newinstr2, feature2, 2)			\
-	".previous"
+	".popsection"
 
 /*
  * This must be included *after* the definition of ALTERNATIVE due to