[PATCH 5.10 013/130] x86/alternative: Support ALTERNATIVE_TERNARY

Greg Kroah-Hartman
2022-07-12T18:45:03Z

From: Juergen Gross <jgross@suse.com>

commit e208b3c4a9748b2c17aa09ba663b5096ccf82dce upstream.

Add ALTERNATIVE_TERNARY support for replacing an initial instruction
with either of two instructions depending on a feature:

ALTERNATIVE_TERNARY "default_instr", FEATURE_NR,
"feature_on_instr", "feature_off_instr"

which will start with "default_instr" and at patch time will,
depending on FEATURE_NR being set or not, patch that with either
"feature_on_instr" or "feature_off_instr".

[ bp: Add comment ontop. ]

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210311142319.4723-7-jgross@suse.com
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/include/asm/alternative.h | 13 +++++++++++++
1 file changed, 13 insertions(+)

--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -179,6 +179,11 @@ static inline int alternatives_text_rese
ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
".popsection\n"

+/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
+#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
+ ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
+ newinstr_yes, feature)
+
#define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \
OLDINSTR_3(oldinsn, 1, 2, 3) \
".pushsection .altinstructions,\"a\"\n" \
@@ -210,6 +215,9 @@ static inline int alternatives_text_rese
#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")

+#define alternative_ternary(oldinstr, feature, newinstr_yes, newinstr_no) \
+ asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) ::: "memory")
+
/*
* Alternative inline assembly with input.
*
@@ -380,6 +388,11 @@ static inline int alternatives_text_rese
.popsection
.endm

+/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
+#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
+ ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
+ newinstr_yes, feature
+
#endif /* __ASSEMBLY__ */

#endif /* _ASM_X86_ALTERNATIVE_H */