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Merge tag 'x86_alternatives_for_v6.3_rc1' of git://git.kernel.org/pub…
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…/scm/linux/kernel/git/tip/tip

Pull x86 asm alternatives updates from Borislav Petkov:

 - Teach the static_call patching infrastructure to handle conditional
   tall calls properly which can be static calls too

 - Add proper struct alt_instr.flags which controls different aspects of
   insn patching behavior

* tag 'x86_alternatives_for_v6.3_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/static_call: Add support for Jcc tail-calls
  x86/alternatives: Teach text_poke_bp() to patch Jcc.d32 instructions
  x86/alternatives: Introduce int3_emulate_jcc()
  x86/alternatives: Add alt_instr.flags
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Linus Torvalds committed Feb 21, 2023
2 parents d9de5ce + 923510c commit 1adce1b
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Showing 6 changed files with 218 additions and 115 deletions.
132 changes: 76 additions & 56 deletions arch/x86/include/asm/alternative.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,10 @@
#include <linux/stringify.h>
#include <asm/asm.h>

#define ALTINSTR_FLAG_INV (1 << 15)
#define ALT_NOT(feat) ((feat) | ALTINSTR_FLAG_INV)
#define ALT_FLAGS_SHIFT 16

#define ALT_FLAG_NOT BIT(0)
#define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))

#ifndef __ASSEMBLY__

Expand Down Expand Up @@ -59,10 +61,27 @@
".long 999b - .\n\t" \
".popsection\n\t"

/*
* The patching flags are part of the upper bits of the @ft_flags parameter when
* specifying them. The split is currently like this:
*
* [31... flags ...16][15... CPUID feature bit ...0]
*
* but since this is all hidden in the macros argument being split, those fields can be
* extended in the future to fit in a u64 or however the need arises.
*/
struct alt_instr {
s32 instr_offset; /* original instruction */
s32 repl_offset; /* offset to replacement instruction */
u16 cpuid; /* cpuid bit set for replacement */

union {
struct {
u32 cpuid: 16; /* CPUID bit set for replacement */
u32 flags: 16; /* patching control flags */
};
u32 ft_flags;
};

u8 instrlen; /* length of original instruction */
u8 replacementlen; /* length of new instruction */
} __packed;
Expand Down Expand Up @@ -182,10 +201,10 @@ static inline int alternatives_text_reserved(void *start, void *end)
" - (" alt_slen ")), 0x90\n" \
alt_end_marker ":\n"

#define ALTINSTR_ENTRY(feature, num) \
#define ALTINSTR_ENTRY(ft_flags, num) \
" .long 661b - .\n" /* label */ \
" .long " b_replacement(num)"f - .\n" /* new instruction */ \
" .word " __stringify(feature) "\n" /* feature bit */ \
" .4byte " __stringify(ft_flags) "\n" /* feature + flags */ \
" .byte " alt_total_slen "\n" /* source len */ \
" .byte " alt_rlen(num) "\n" /* replacement len */

Expand All @@ -194,42 +213,43 @@ static inline int alternatives_text_reserved(void *start, void *end)
b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"

/* alternative assembly primitive: */
#define ALTERNATIVE(oldinstr, newinstr, feature) \
#define ALTERNATIVE(oldinstr, newinstr, ft_flags) \
OLDINSTR(oldinstr, 1) \
".pushsection .altinstructions,\"a\"\n" \
ALTINSTR_ENTRY(feature, 1) \
ALTINSTR_ENTRY(ft_flags, 1) \
".popsection\n" \
".pushsection .altinstr_replacement, \"ax\"\n" \
ALTINSTR_REPLACEMENT(newinstr, 1) \
".popsection\n"

#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
#define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
OLDINSTR_2(oldinstr, 1, 2) \
".pushsection .altinstructions,\"a\"\n" \
ALTINSTR_ENTRY(feature1, 1) \
ALTINSTR_ENTRY(feature2, 2) \
ALTINSTR_ENTRY(ft_flags1, 1) \
ALTINSTR_ENTRY(ft_flags2, 2) \
".popsection\n" \
".pushsection .altinstr_replacement, \"ax\"\n" \
ALTINSTR_REPLACEMENT(newinstr1, 1) \
ALTINSTR_REPLACEMENT(newinstr2, 2) \
".popsection\n"

/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
#define ALTERNATIVE_TERNARY(oldinstr, ft_flags, 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" \
ALTINSTR_ENTRY(feat1, 1) \
ALTINSTR_ENTRY(feat2, 2) \
ALTINSTR_ENTRY(feat3, 3) \
".popsection\n" \
".pushsection .altinstr_replacement, \"ax\"\n" \
ALTINSTR_REPLACEMENT(newinsn1, 1) \
ALTINSTR_REPLACEMENT(newinsn2, 2) \
ALTINSTR_REPLACEMENT(newinsn3, 3) \
newinstr_yes, ft_flags)

#define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \
newinsn3, ft_flags3) \
OLDINSTR_3(oldinsn, 1, 2, 3) \
".pushsection .altinstructions,\"a\"\n" \
ALTINSTR_ENTRY(ft_flags1, 1) \
ALTINSTR_ENTRY(ft_flags2, 2) \
ALTINSTR_ENTRY(ft_flags3, 3) \
".popsection\n" \
".pushsection .altinstr_replacement, \"ax\"\n" \
ALTINSTR_REPLACEMENT(newinsn1, 1) \
ALTINSTR_REPLACEMENT(newinsn2, 2) \
ALTINSTR_REPLACEMENT(newinsn3, 3) \
".popsection\n"

/*
Expand All @@ -244,14 +264,14 @@ static inline int alternatives_text_reserved(void *start, void *end)
* For non barrier like inlines please define new variants
* without volatile and memory clobber.
*/
#define alternative(oldinstr, newinstr, feature) \
asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
#define alternative(oldinstr, newinstr, ft_flags) \
asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")

#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
#define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")

#define alternative_ternary(oldinstr, feature, newinstr_yes, newinstr_no) \
asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) ::: "memory")
#define alternative_ternary(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) ::: "memory")

/*
* Alternative inline assembly with input.
Expand All @@ -261,8 +281,8 @@ static inline int alternatives_text_reserved(void *start, void *end)
* Argument numbers start with 1.
* Leaving an unused argument 0 to keep API compatibility.
*/
#define alternative_input(oldinstr, newinstr, feature, input...) \
asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
#define alternative_input(oldinstr, newinstr, ft_flags, input...) \
asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) \
: : "i" (0), ## input)

/*
Expand All @@ -273,20 +293,20 @@ static inline int alternatives_text_reserved(void *start, void *end)
* Otherwise, if CPU has feature1, newinstr1 is used.
* Otherwise, oldinstr is used.
*/
#define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \
feature2, input...) \
asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \
newinstr2, feature2) \
#define alternative_input_2(oldinstr, newinstr1, ft_flags1, newinstr2, \
ft_flags2, input...) \
asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, \
newinstr2, ft_flags2) \
: : "i" (0), ## input)

/* Like alternative_input, but with a single output argument */
#define alternative_io(oldinstr, newinstr, feature, output, input...) \
asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
#define alternative_io(oldinstr, newinstr, ft_flags, output, input...) \
asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) \
: output : "i" (0), ## input)

/* Like alternative_io, but for replacing a direct call with another one. */
#define alternative_call(oldfunc, newfunc, feature, output, input...) \
asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
#define alternative_call(oldfunc, newfunc, ft_flags, output, input...) \
asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)

/*
Expand All @@ -295,10 +315,10 @@ static inline int alternatives_text_reserved(void *start, void *end)
* Otherwise, if CPU has feature1, function1 is used.
* Otherwise, old function is used.
*/
#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \
#define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2, \
output, input...) \
asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
"call %P[new2]", feature2) \
asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,\
"call %P[new2]", ft_flags2) \
: output, ASM_CALL_CONSTRAINT \
: [old] "i" (oldfunc), [new1] "i" (newfunc1), \
[new2] "i" (newfunc2), ## input)
Expand Down Expand Up @@ -347,10 +367,10 @@ static inline int alternatives_text_reserved(void *start, void *end)
* enough information for the alternatives patching code to patch an
* instruction. See apply_alternatives().
*/
.macro altinstruction_entry orig alt feature orig_len alt_len
.macro altinstr_entry orig alt ft_flags orig_len alt_len
.long \orig - .
.long \alt - .
.word \feature
.4byte \ft_flags
.byte \orig_len
.byte \alt_len
.endm
Expand All @@ -361,15 +381,15 @@ static inline int alternatives_text_reserved(void *start, void *end)
* @newinstr. ".skip" directive takes care of proper instruction padding
* in case @newinstr is longer than @oldinstr.
*/
.macro ALTERNATIVE oldinstr, newinstr, feature
.macro ALTERNATIVE oldinstr, newinstr, ft_flags
140:
\oldinstr
141:
.skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
142:

.pushsection .altinstructions,"a"
altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f
altinstr_entry 140b,143f,\ft_flags,142b-140b,144f-143f
.popsection

.pushsection .altinstr_replacement,"ax"
Expand Down Expand Up @@ -399,7 +419,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
* has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
* @feature2, it replaces @oldinstr with @feature2.
*/
.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
.macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
140:
\oldinstr
141:
Expand All @@ -408,8 +428,8 @@ static inline int alternatives_text_reserved(void *start, void *end)
142:

.pushsection .altinstructions,"a"
altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f
altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f
altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
.popsection

.pushsection .altinstr_replacement,"ax"
Expand All @@ -421,7 +441,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
.popsection
.endm

.macro ALTERNATIVE_3 oldinstr, newinstr1, feature1, newinstr2, feature2, newinstr3, feature3
.macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
140:
\oldinstr
141:
Expand All @@ -430,9 +450,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
142:

.pushsection .altinstructions,"a"
altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f
altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f
altinstruction_entry 140b,145f,\feature3,142b-140b,146f-145f
altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
altinstr_entry 140b,145f,\ft_flags3,142b-140b,146f-145f
.popsection

.pushsection .altinstr_replacement,"ax"
Expand All @@ -447,9 +467,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
.endm

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

#endif /* __ASSEMBLY__ */

Expand Down
31 changes: 31 additions & 0 deletions arch/x86/include/asm/text-patching.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -184,6 +184,37 @@ void int3_emulate_ret(struct pt_regs *regs)
unsigned long ip = int3_emulate_pop(regs);
int3_emulate_jmp(regs, ip);
}

static __always_inline
void int3_emulate_jcc(struct pt_regs *regs, u8 cc, unsigned long ip, unsigned long disp)
{
static const unsigned long jcc_mask[6] = {
[0] = X86_EFLAGS_OF,
[1] = X86_EFLAGS_CF,
[2] = X86_EFLAGS_ZF,
[3] = X86_EFLAGS_CF | X86_EFLAGS_ZF,
[4] = X86_EFLAGS_SF,
[5] = X86_EFLAGS_PF,
};

bool invert = cc & 1;
bool match;

if (cc < 0xc) {
match = regs->flags & jcc_mask[cc >> 1];
} else {
match = ((regs->flags & X86_EFLAGS_SF) >> X86_EFLAGS_SF_BIT) ^
((regs->flags & X86_EFLAGS_OF) >> X86_EFLAGS_OF_BIT);
if (cc >= 0xe)
match = match || (regs->flags & X86_EFLAGS_ZF);
}

if ((match && !invert) || (!match && invert))
ip += disp;

int3_emulate_jmp(regs, ip);
}

#endif /* !CONFIG_UML_X86 */

#endif /* _ASM_X86_TEXT_PATCHING_H */
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