new file 100644
#ifndef _X86_64_ALTERNATIVE_H
#define _X86_64_ALTERNATIVE_H
#ifdef __KERNEL__
#include <linux/types.h>
#include <asm/cpufeature.h>
struct alt_instr {
u8 *instr; /* original instruction */
u8 *replacement;
u8 cpuid; /* cpuid bit set for replacement */
u8 instrlen; /* length of original instruction */
u8 replacementlen; /* length of new instruction, <= instrlen */
u8 pad[5];
};
extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
struct module;
#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_smp_switch(int smp);
#else
static inline void alternatives_smp_module_add(struct module *mod, char *name,
void *text, void *text_end) {}
static inline void alternatives_smp_module_del(struct module *mod) {}
static inline void alternatives_smp_switch(int smp) {}
#endif
/*
* 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, feature) \
asm volatile ("661:\n\t" oldinstr "\n662:\n" \
".section .altinstructions,\"a\"\n" \
" .align 8\n" \
" .quad 661b\n" /* label */ \
" .quad 663f\n" /* new instruction */ \
" .byte %c0\n" /* feature bit */ \
" .byte 662b-661b\n" /* sourcelen */ \
" .byte 664f-663f\n" /* replacementlen */ \
".previous\n" \
".section .altinstr_replacement,\"ax\"\n" \
"663:\n\t" newinstr "\n664:\n" /* replacement */ \
".previous" :: "i" (feature) : "memory")
* Alternative inline assembly with input.
* Pecularities:
* No memory clobber here.
* Argument numbers start with 1.
* Best is to use constraints that are fixed size (like (%1) ... "r")
* If you use variable sized constraints like "m" or "g" in the
* replacement make sure to pad to the worst case length.
#define alternative_input(oldinstr, newinstr, feature, input...) \
".previous" :: "i" (feature), ##input)
/* Like alternative_input, but with a single output argument */
#define alternative_io(oldinstr, newinstr, feature, output, input...) \
" .byte %c[feat]\n" /* feature bit */ \
".previous" : output : [feat] "i" (feature), ##input)
* 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.
#define LOCK_PREFIX \
".section .smp_locks,\"a\"\n" \
" .quad 661f\n" /* address */ \
"661:\n\tlock; "
#else /* ! CONFIG_SMP */
#define LOCK_PREFIX ""
#endif /* _X86_64_ALTERNATIVE_H */