[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v4 08/15] x86/alternative: support "not feature" and ALTERNATIVE_TERNARY
Instead of only supporting to modify instructions when a specific feature is set, support doing so for the case a feature is not set. 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@xxxxxxxx> --- 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 --- arch/x86/include/asm/alternative-asm.h | 4 ++++ arch/x86/include/asm/alternative.h | 7 +++++++ arch/x86/kernel/alternative.c | 17 ++++++++++++----- 3 files changed, 23 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/alternative-asm.h b/arch/x86/include/asm/alternative-asm.h index 464034db299f..a0768e880976 100644 --- a/arch/x86/include/asm/alternative-asm.h +++ b/arch/x86/include/asm/alternative-asm.h @@ -109,6 +109,10 @@ .popsection .endm +#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2) \ + ALTERNATIVE_2 oldinstr, newinstr2, X86_FEATURE_ALWAYS, \ + newinstr1, feature + #endif /* __ASSEMBLY__ */ #endif /* _ASM_X86_ALTERNATIVE_ASM_H */ diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index 13adca37c99a..7412653182dd 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -59,6 +59,7 @@ struct alt_instr { s32 instr_offset; /* original instruction */ s32 repl_offset; /* offset to replacement instruction */ u16 cpuid; /* cpuid bit set for replacement */ +#define ALT_INSTR_CPUID_INV 0x8000 /* patch if ~cpuid bit is NOT set */ u8 instrlen; /* length of original instruction */ u8 replacementlen; /* length of new instruction */ u8 padlen; /* length of build-time padding */ @@ -175,6 +176,9 @@ static inline int alternatives_text_reserved(void *start, void *end) ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \ ".popsection\n" +#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2) \ + ALTERNATIVE_2(oldinstr, newinstr2, X86_FEATURE_ALWAYS, newinstr1, feature) + #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \ OLDINSTR_3(oldinsn, 1, 2, 3) \ ".pushsection .altinstructions,\"a\"\n" \ @@ -206,6 +210,9 @@ 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, newinstr1, newinstr2) \ + asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2) ::: "memory") + /* * Alternative inline assembly with input. * diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 8d778e46725d..0a904fb2678b 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -388,21 +388,28 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start, */ for (a = start; a < end; a++) { int insn_buff_sz = 0; + u16 feature; + bool not_feature; instr = (u8 *)&a->instr_offset + a->instr_offset; replacement = (u8 *)&a->repl_offset + a->repl_offset; + feature = a->cpuid; + not_feature = feature & ALT_INSTR_CPUID_INV; + if (not_feature) + feature = ~feature; BUG_ON(a->instrlen > sizeof(insn_buff)); - BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32); - if (!boot_cpu_has(a->cpuid)) { + BUG_ON(feature >= (NCAPINTS + NBUGINTS) * 32); + if (!!boot_cpu_has(feature) == not_feature) { if (a->padlen > 1) optimize_nops(a, instr); continue; } - DPRINTK("feat: %d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d), pad: %d", - a->cpuid >> 5, - a->cpuid & 0x1f, + DPRINTK("feat: %s%d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d), pad: %d", + not_feature ? "~" : "", + feature >> 5, + feature & 0x1f, instr, instr, a->instrlen, replacement, a->replacementlen, a->padlen); -- 2.26.2
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