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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_ALTERNATIVE_H
#define _ASM_X86_ALTERNATIVE_H
#include <linux/types.h>
#include <linux/stringify.h>
#include <asm/asm.h>
#define ALT_FLAGS_SHIFT 16
#define ALT_FLAG_NOT (1 << 0)
#define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))
#define ALT_FLAG_DIRECT_CALL (1 << 1)
#define ALT_DIRECT_CALL(feature) ((ALT_FLAG_DIRECT_CALL << ALT_FLAGS_SHIFT) | (feature))
#define ALT_CALL_ALWAYS ALT_DIRECT_CALL(X86_FEATURE_ALWAYS)
#ifndef __ASSEMBLY__
#include <linux/stddef.h>
/*
* Alternative inline assembly for SMP.
*
* The LOCK_PREFIX macro defined here replaces the LOCK and
* LOCK_PREFIX macros used everywhere in the source tree.
*
* SMP alternatives use the same data structures as the other
* alternatives and the X86_FEATURE_UP flag to indicate the case of a
* UP system running a SMP kernel. The existing apply_alternatives()
* works fine for patching a SMP kernel for UP.
*
* The SMP alternative tables can be kept after boot and contain both
* UP and SMP versions of the instructions to allow switching back to
* SMP at runtime, when hotplugging in a new CPU, which is especially
* useful in virtualized environments.
*
* The very common lock prefix is handled as special case in a
* separate table which is a pure address list without replacement ptr
* and size information. That keeps the table sizes small.
*/
#ifdef CONFIG_SMP
#define LOCK_PREFIX_HERE \
".pushsection .smp_locks,\"a\"\n" \
".balign 4\n" \
".long 671f - .\n" /* offset */ \
".popsection\n" \
"671:"
#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
#else /* ! CONFIG_SMP */
#define LOCK_PREFIX_HERE ""
#define LOCK_PREFIX ""
#endif
/*
* objtool annotation to ignore the alternatives and only consider the original
* instruction(s).
*/
#define ANNOTATE_IGNORE_ALTERNATIVE \
"999:\n\t" \
".pushsection .discard.ignore_alts\n\t" \
".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;
};
u8 instrlen; /* length of original instruction */
u8 replacementlen; /* length of new instruction */
} __packed;
extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
/*
* Debug flag that can be tested to see whether alternative
* instructions were patched in already:
*/
extern int alternatives_patched;
extern void alternative_instructions(void);
extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
extern void apply_retpolines(s32 *start, s32 *end);
extern void apply_returns(s32 *start, s32 *end);
extern void apply_seal_endbr(s32 *start, s32 *end);
extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine,
s32 *start_cfi, s32 *end_cfi);
struct module;
struct callthunk_sites {
s32 *call_start, *call_end;
struct alt_instr *alt_start, *alt_end;
};
#ifdef CONFIG_CALL_THUNKS
extern void callthunks_patch_builtin_calls(void);
extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
struct module *mod);
extern void *callthunks_translate_call_dest(void *dest);
extern int x86_call_depth_emit_accounting(u8 **pprog, void *func);
#else
static __always_inline void callthunks_patch_builtin_calls(void) {}
static __always_inline void
callthunks_patch_module_calls(struct callthunk_sites *sites,
struct module *mod) {}
static __always_inline void *callthunks_translate_call_dest(void *dest)
{
return dest;
}
static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
void *func)
{
return 0;
}
#endif
#ifdef CONFIG_SMP
extern void alternatives_smp_module_add(struct module *mod, char *name,
void *locks, void *locks_end,
void *text, void *text_end);
extern void alternatives_smp_module_del(struct module *mod);
extern void alternatives_enable_smp(void);
extern int alternatives_text_reserved(void *start, void *end);
extern bool skip_smp_alternatives;
#else
static inline void alternatives_smp_module_add(struct module *mod, char *name,
void *locks, void *locks_end,
void *text, void *text_end) {}
static inline void alternatives_smp_module_del(struct module *mod) {}
static inline void alternatives_enable_smp(void) {}
static inline int alternatives_text_reserved(void *start, void *end)
{
return 0;
}
#endif /* CONFIG_SMP */
#define ALT_CALL_INSTR "call BUG_func"
#define b_replacement(num) "664"#num
#define e_replacement(num) "665"#num
#define alt_end_marker "663"
#define alt_slen "662b-661b"
#define alt_total_slen alt_end_marker"b-661b"
#define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"
#define OLDINSTR(oldinstr, num) \
"# ALT: oldnstr\n" \
"661:\n\t" oldinstr "\n662:\n" \
"# ALT: padding\n" \
".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \
alt_end_marker ":\n"
/*
* gas compatible max based on the idea from:
* http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
*
* The additional "-" is needed because gas uses a "true" value of -1.
*/
#define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"
/*
* Pad the second replacement alternative with additional NOPs if it is
* additionally longer than the first replacement alternative.
*/
#define OLDINSTR_2(oldinstr, num1, num2) \
"# ALT: oldinstr2\n" \
"661:\n\t" oldinstr "\n662:\n" \
"# ALT: padding2\n" \
".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \
"(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \
alt_end_marker ":\n"
#define OLDINSTR_3(oldinsn, n1, n2, n3) \
"# ALT: oldinstr3\n" \
"661:\n\t" oldinsn "\n662:\n" \
"# ALT: padding3\n" \
".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
" - (" alt_slen ")) > 0) * " \
"(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
" - (" alt_slen ")), 0x90\n" \
alt_end_marker ":\n"
#define ALTINSTR_ENTRY(ft_flags, num) \
" .long 661b - .\n" /* label */ \
" .long " b_replacement(num)"f - .\n" /* new instruction */ \
" .4byte " __stringify(ft_flags) "\n" /* feature + flags */ \
" .byte " alt_total_slen "\n" /* source len */ \
" .byte " alt_rlen(num) "\n" /* replacement len */
#define ALTINSTR_REPLACEMENT(newinstr, num) /* replacement */ \
"# ALT: replacement " #num "\n" \
b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"
/* alternative assembly primitive: */
#define ALTERNATIVE(oldinstr, newinstr, ft_flags) \
OLDINSTR(oldinstr, 1) \
".pushsection .altinstructions,\"a\"\n" \
ALTINSTR_ENTRY(ft_flags, 1) \
".popsection\n" \
".pushsection .altinstr_replacement, \"ax\"\n" \
ALTINSTR_REPLACEMENT(newinstr, 1) \
".popsection\n"
#define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
OLDINSTR_2(oldinstr, 1, 2) \
".pushsection .altinstructions,\"a\"\n" \
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, ft_flags, 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) \
".popsection\n"
/*
* Alternative instructions for different CPU types or capabilities.
*
* This allows to use optimized instructions even on generic binary
* kernels.
*
* length of oldinstr must be longer or equal the length of newinstr
* It can be padded with nops as needed.
*
* 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_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, ft_flags, newinstr_yes, newinstr_no) \
asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) ::: "memory")
/*
* Alternative inline assembly with input.
*
* Peculiarities:
* No memory clobber here.
* 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) \
: : "i" (0), ## input)
/*
* This is similar to alternative_input. But it has two features and
* respective instructions.
*
* If CPU has feature2, newinstr2 is used.
* 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) \
: : "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) \
: 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 %c[old]", "call %c[new]", ft_flags) \
: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
/*
* Like alternative_call, but there are two features and respective functions.
* If CPU has feature2, function2 is used.
* Otherwise, if CPU has feature1, function1 is used.
* Otherwise, old function is used.
*/
#define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2, \
output, input...) \
asm_inline volatile (ALTERNATIVE_2("call %c[old]", "call %c[new1]", ft_flags1, \
"call %c[new2]", ft_flags2) \
: output, ASM_CALL_CONSTRAINT \
: [old] "i" (oldfunc), [new1] "i" (newfunc1), \
[new2] "i" (newfunc2), ## input)
/*
* use this macro(s) if you need more than one output parameter
* in alternative_io
*/
#define ASM_OUTPUT2(a...) a
/*
* use this macro if you need clobbers but no inputs in
* alternative_{input,io,call}()
*/
#define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
/* Macro for creating assembler functions avoiding any C magic. */
#define DEFINE_ASM_FUNC(func, instr, sec) \
asm (".pushsection " #sec ", \"ax\"\n" \
".global " #func "\n\t" \
".type " #func ", @function\n\t" \
ASM_FUNC_ALIGN "\n" \
#func ":\n\t" \
ASM_ENDBR \
instr "\n\t" \
ASM_RET \
".size " #func ", . - " #func "\n\t" \
".popsection")
void BUG_func(void);
void nop_func(void);
#else /* __ASSEMBLY__ */
#ifdef CONFIG_SMP
.macro LOCK_PREFIX
672: lock
.pushsection .smp_locks,"a"
.balign 4
.long 672b - .
.popsection
.endm
#else
.macro LOCK_PREFIX
.endm
#endif
/*
* objtool annotation to ignore the alternatives and only consider the original
* instruction(s).
*/
.macro ANNOTATE_IGNORE_ALTERNATIVE
.Lannotate_\@:
.pushsection .discard.ignore_alts
.long .Lannotate_\@
.popsection
.endm
/*
* Issue one struct alt_instr descriptor entry (need to put it into
* the section .altinstructions, see below). This entry contains
* 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
.long \orig - .
.long \alt - .
.4byte \ft_flags
.byte \orig_len
.byte \alt_len
.endm
.macro ALT_CALL_INSTR
call BUG_func
.endm
/*
* Define an alternative between two instructions. If @feature is
* present, early code in apply_alternatives() replaces @oldinstr with
* @newinstr. ".skip" directive takes care of proper instruction padding
* in case @newinstr is longer than @oldinstr.
*/
.macro ALTERNATIVE oldinstr, newinstr, ft_flags
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
.popsection
.pushsection .altinstr_replacement,"ax"
143:
\newinstr
144:
.popsection
.endm
#define old_len 141b-140b
#define new_len1 144f-143f
#define new_len2 145f-144f
#define new_len3 146f-145f
/*
* gas compatible max based on the idea from:
* http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
*
* The additional "-" is needed because gas uses a "true" value of -1.
*/
#define alt_max_2(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
#define alt_max_3(a, b, c) (alt_max_2(alt_max_2(a, b), c))
/*
* Same as ALTERNATIVE macro above but for two alternatives. If CPU
* 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
140:
\oldinstr
141:
.skip -((alt_max_2(new_len1, new_len2) - (old_len)) > 0) * \
(alt_max_2(new_len1, new_len2) - (old_len)),0x90
142:
.pushsection .altinstructions,"a"
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"
143:
\newinstr1
144:
\newinstr2
145:
.popsection
.endm
.macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
140:
\oldinstr
141:
.skip -((alt_max_3(new_len1, new_len2, new_len3) - (old_len)) > 0) * \
(alt_max_3(new_len1, new_len2, new_len3) - (old_len)),0x90
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
.popsection
.pushsection .altinstr_replacement,"ax"
143:
\newinstr1
144:
\newinstr2
145:
\newinstr3
146:
.popsection
.endm
/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
#define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
newinstr_yes, ft_flags
#endif /* __ASSEMBLY__ */
#endif /* _ASM_X86_ALTERNATIVE_H */