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Revert "x86/alternatives: Add alt_instr.flags"
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This reverts commit 5d1dd96.
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@cpaasch
cpaasch committed Feb 27, 2023
1 parent 697afce commit cc518bd
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Showing 3 changed files with 67 additions and 85 deletions.
132 changes: 56 additions & 76 deletions arch/x86/include/asm/alternative.h
View file
Expand Up @@ -6,10 +6,8 @@
#include <linux/stringify.h>
#include <asm/asm.h>

#define ALT_FLAGS_SHIFT 16

#define ALT_FLAG_NOT BIT(0)
#define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))
#define ALTINSTR_FLAG_INV (1 << 15)
#define ALT_NOT(feat) ((feat) | ALTINSTR_FLAG_INV)

#ifndef __ASSEMBLY__

Expand Down Expand Up @@ -61,27 +59,10 @@
".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 */

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

u16 cpuid; /* cpuid bit set for replacement */
u8 instrlen; /* length of original instruction */
u8 replacementlen; /* length of new instruction */
} __packed;
Expand Down Expand Up @@ -201,10 +182,10 @@ static inline int alternatives_text_reserved(void *start, void *end)
" - (" alt_slen ")), 0x90\n" \
alt_end_marker ":\n"

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

Expand All @@ -213,43 +194,42 @@ 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, ft_flags) \
#define ALTERNATIVE(oldinstr, newinstr, feature) \
OLDINSTR(oldinstr, 1) \
".pushsection .altinstructions,\"a\"\n" \
ALTINSTR_ENTRY(ft_flags, 1) \
ALTINSTR_ENTRY(feature, 1) \
".popsection\n" \
".pushsection .altinstr_replacement, \"ax\"\n" \
ALTINSTR_REPLACEMENT(newinstr, 1) \
".popsection\n"

#define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
OLDINSTR_2(oldinstr, 1, 2) \
".pushsection .altinstructions,\"a\"\n" \
ALTINSTR_ENTRY(ft_flags1, 1) \
ALTINSTR_ENTRY(ft_flags2, 2) \
ALTINSTR_ENTRY(feature1, 1) \
ALTINSTR_ENTRY(feature2, 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, ft_flags, newinstr_yes, newinstr_no) \
#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
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) \
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) \
".popsection\n"

/*
Expand All @@ -264,14 +244,14 @@ 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, ft_flags) \
asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
#define alternative(oldinstr, newinstr, feature) \
asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "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_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")

#define alternative_ternary(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) ::: "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.
Expand All @@ -281,8 +261,8 @@ 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, ft_flags, input...) \
asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) \
#define alternative_input(oldinstr, newinstr, feature, input...) \
asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
: : "i" (0), ## input)

/*
Expand All @@ -293,20 +273,20 @@ 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, ft_flags1, newinstr2, \
ft_flags2, input...) \
asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, \
newinstr2, ft_flags2) \
#define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \
feature2, input...) \
asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \
newinstr2, feature2) \
: : "i" (0), ## input)

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

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

/*
Expand All @@ -315,10 +295,10 @@ 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, ft_flags1, newfunc2, ft_flags2, \
#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \
output, input...) \
asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,\
"call %P[new2]", ft_flags2) \
asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
"call %P[new2]", feature2) \
: output, ASM_CALL_CONSTRAINT \
: [old] "i" (oldfunc), [new1] "i" (newfunc1), \
[new2] "i" (newfunc2), ## input)
Expand Down Expand Up @@ -367,10 +347,10 @@ 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 altinstr_entry orig alt ft_flags orig_len alt_len
.macro altinstruction_entry orig alt feature orig_len alt_len
.long \orig - .
.long \alt - .
.4byte \ft_flags
.word \feature
.byte \orig_len
.byte \alt_len
.endm
Expand All @@ -381,15 +361,15 @@ 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, ft_flags
.macro ALTERNATIVE oldinstr, newinstr, feature
140:
\oldinstr
141:
.skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
142:

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

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

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

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

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

.pushsection .altinstructions,"a"
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
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
.popsection

.pushsection .altinstr_replacement,"ax"
Expand All @@ -467,9 +447,9 @@ 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, ft_flags, newinstr_yes, newinstr_no) \
#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
newinstr_yes, ft_flags
newinstr_yes, feature

#endif /* __ASSEMBLY__ */

Expand Down
14 changes: 8 additions & 6 deletions arch/x86/kernel/alternative.c
View file
Expand Up @@ -282,25 +282,27 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start,
*/
for (a = start; a < end; a++) {
int insn_buff_sz = 0;
/* Mask away "NOT" flag bit for feature to test. */
u16 feature = a->cpuid & ~ALTINSTR_FLAG_INV;

instr = (u8 *)&a->instr_offset + a->instr_offset;
replacement = (u8 *)&a->repl_offset + a->repl_offset;
BUG_ON(a->instrlen > sizeof(insn_buff));
BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32);
BUG_ON(feature >= (NCAPINTS + NBUGINTS) * 32);

/*
* Patch if either:
* - feature is present
* - feature not present but ALT_FLAG_NOT is set to mean,
* - feature not present but ALTINSTR_FLAG_INV is set to mean,
* patch if feature is *NOT* present.
*/
if (!boot_cpu_has(a->cpuid) == !(a->flags & ALT_FLAG_NOT))
if (!boot_cpu_has(feature) == !(a->cpuid & ALTINSTR_FLAG_INV))
goto next;

DPRINTK("feat: %s%d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d)",
(a->flags & ALT_FLAG_NOT) ? "!" : "",
a->cpuid >> 5,
a->cpuid & 0x1f,
(a->cpuid & ALTINSTR_FLAG_INV) ? "!" : "",
feature >> 5,
feature & 0x1f,
instr, instr, a->instrlen,
replacement, a->replacementlen);

Expand Down
6 changes: 3 additions & 3 deletions tools/objtool/arch/x86/include/arch/special.h
View file
Expand Up @@ -11,11 +11,11 @@
#define JUMP_NEW_OFFSET 4
#define JUMP_KEY_OFFSET 8

#define ALT_ENTRY_SIZE 14
#define ALT_ENTRY_SIZE 12
#define ALT_ORIG_OFFSET 0
#define ALT_NEW_OFFSET 4
#define ALT_FEATURE_OFFSET 8
#define ALT_ORIG_LEN_OFFSET 12
#define ALT_NEW_LEN_OFFSET 13
#define ALT_ORIG_LEN_OFFSET 10
#define ALT_NEW_LEN_OFFSET 11

#endif /* _X86_ARCH_SPECIAL_H */

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