[PATCH 15/24] x86: Annotate static_cpu_has alternative

[Peter Zijlstra]

In order to recognise static_cpu_has() alternatives from any other
alternative without dodgy heuristics, we need to explicitly mark them.
Use the new type field for this.

Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 arch/x86/include/asm/alternative.h |    6 ++++++
 arch/x86/include/asm/cpufeature.h  |    5 +++--
 2 files changed, 9 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -47,6 +47,12 @@
 
 #define ALT_TYPE_DEFAULT	0
 
+/*
+ * This alt_instr descriptor is part of a static_cpu_has() construct. Use it to
+ * detect its type when processing with other tools, like objtool, for example.
+ */
+#define ALT_TYPE_STATIC_CPU_HAS	1
+
 struct alt_instr {
 	s32 instr_offset;	/* original instruction */
 	s32 repl_offset;	/* offset to replacement instruction */
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -157,7 +157,7 @@ static __always_inline __pure bool _stat
 		 " .byte 3b - 1b\n"		/* src len */
 		 " .byte 5f - 4f\n"		/* repl len */
 		 " .byte 3b - 2b\n"		/* pad len */
-		 " .byte 0\n"			/* type */
+		 " .byte %P[type]\n"		/* type */
 		 ".previous\n"
 		 ".section .altinstr_replacement,\"ax\"\n"
 		 "4: jmp %l[t_no]\n"
@@ -170,7 +170,7 @@ static __always_inline __pure bool _stat
 		 " .byte 3b - 1b\n"		/* src len */
 		 " .byte 0\n"			/* repl len */
 		 " .byte 0\n"			/* pad len */
-		 " .byte 0\n"			/* type */
+		 " .byte %P[type]\n"		/* type */
 		 ".previous\n"
 		 ".section .altinstr_aux,\"ax\"\n"
 		 "6:\n"
@@ -181,6 +181,7 @@ static __always_inline __pure bool _stat
 		 : : [feature]  "i" (bit),
 		     [always]   "i" (X86_FEATURE_ALWAYS),
 		     [bitnum]   "i" (1 << (bit & 7)),
+		     [type]	"i" (ALT_TYPE_STATIC_CPU_HAS),
 		     [cap_byte] "m" (((const char *)boot_cpu_data.x86_capability)[bit >> 3])
 		 : : t_yes, t_no);
 t_yes: