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Subject[PATCH v7 06/14] x86/alternative: support ALTERNATIVE_TERNARY
Date
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".

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
V3:
- new patch
V4:
- use X86_FEATURE_ALWAYS instead of negated feature (Boris Petkov)
- unfortunately this isn't enough to get rid of the "not feature"
support, as this is needed in the patch "x86/paravirt: switch
functions with custom code to ALTERNATIVE", too
V5:
- carve out the "not feature" part
V7:
- rename parameter names (Boris Petkov)
---
arch/x86/include/asm/alternative.h | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 649e56f70889..a044e59cbdf5 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -179,6 +179,10 @@ static inline int alternatives_text_reserved(void *start, void *end)
ALTINSTR_REPLACEMENT(newinstr2, 2) \
".popsection\n"

+#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 +214,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
#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 +387,10 @@ static inline int alternatives_text_reserved(void *start, void *end)
.popsection
.endm

+#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 */
--
2.26.2
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