#ifndef _ASM_X86_ALTERNATIVE_H #define _ASM_X86_ALTERNATIVE_H #include <linux/types.h> #include <linux/stddef.h> #include <linux/stringify.h> #include <asm/asm.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 \ ".section .smp_locks,\"a\"\n" \ _ASM_ALIGN "\n" \ _ASM_PTR "671f\n" /* address */ \ ".previous\n" \ "671:" #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; " #else /* ! CONFIG_SMP */ #define LOCK_PREFIX_HERE "" #define LOCK_PREFIX "" #endif /* This must be included *after* the definition of LOCK_PREFIX */ #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 pad1; #ifdef CONFIG_X86_64 u32 pad2; #endif }; extern void alternative_instructions(void); 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 *locks, void *locks_end, void *text, void *text_end) {} static inline void alternatives_smp_module_del(struct module *mod) {} static inline void alternatives_smp_switch(int smp) {} #endif /* CONFIG_SMP */ /* alternative assembly primitive: */ #define ALTERNATIVE(oldinstr, newinstr, feature) \ \ "661:\n\t" oldinstr "\n662:\n" \ ".section .altinstructions,\"a\"\n" \ _ASM_ALIGN "\n" \ _ASM_PTR "661b\n" /* label */ \ _ASM_PTR "663f\n" /* new instruction */ \ " .byte " __stringify(feature) "\n" /* feature bit */ \ " .byte 662b-661b\n" /* sourcelen */ \ " .byte 664f-663f\n" /* replacementlen */ \ " .byte 0xff + (664f-663f) - (662b-661b)\n" /* rlen <= slen */ \ ".previous\n" \ ".section .altinstr_replacement, \"ax\"\n" \ "663:\n\t" newinstr "\n664:\n" /* replacement */ \ ".previous" /* * 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 (ALTERNATIVE(oldinstr, newinstr, 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. * Leaving an unused argument 0 to keep API compatibility. */ #define alternative_input(oldinstr, newinstr, feature, input...) \ asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ : : "i" (0), ## input) /* Like alternative_input, but with a single output argument */ #define alternative_io(oldinstr, newinstr, feature, output, input...) \ asm 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, feature, output, input...) \ asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) /* * use this macro(s) if you need more than one output parameter * in alternative_io */ #define ASM_OUTPUT2(a...) a struct paravirt_patch_site; #ifdef CONFIG_PARAVIRT void apply_paravirt(struct paravirt_patch_site *start, struct paravirt_patch_site *end); #else static inline void apply_paravirt(struct paravirt_patch_site *start, struct paravirt_patch_site *end) {} #define __parainstructions NULL #define __parainstructions_end NULL #endif /* * Clear and restore the kernel write-protection flag on the local CPU. * Allows the kernel to edit read-only pages. * Side-effect: any interrupt handler running between save and restore will have * the ability to write to read-only pages. * * Warning: * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and * no thread can be preempted in the instructions being modified (no iret to an * invalid instruction possible) or if the instructions are changed from a * consistent state to another consistent state atomically. * More care must be taken when modifying code in the SMP case because of * Intel's errata. * On the local CPU you need to be protected again NMI or MCE handlers seeing an * inconsistent instruction while you patch. */ extern void *text_poke(void *addr, const void *opcode, size_t len); #endif /* _ASM_X86_ALTERNATIVE_H */