/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _ASM_X86_ALTERNATIVE_H #define _ASM_X86_ALTERNATIVE_H #ifndef __ASSEMBLY__ #include #include #include #include /* * 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 struct alt_instr { s32 instr_offset; /* original instruction */ s32 repl_offset; /* offset to replacement instruction */ u16 cpuid; /* cpuid bit set for replacement */ u8 instrlen; /* length of original instruction */ u8 replacementlen; /* length of new instruction */ u8 padlen; /* length of build-time padding */ } __packed; /* * 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); 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_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 b_replacement(num) "664"#num #define e_replacement(num) "665"#num #define alt_end_marker "663" #define alt_slen "662b-661b" #define alt_pad_len alt_end_marker"b-662b" #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(feature, num) \ " .long 661b - .\n" /* label */ \ " .long " b_replacement(num)"f - .\n" /* new instruction */ \ " .word " __stringify(feature) "\n" /* feature bit */ \ " .byte " alt_total_slen "\n" /* source len */ \ " .byte " alt_rlen(num) "\n" /* replacement len */ \ " .byte " alt_pad_len "\n" /* pad len */ #define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \ "# ALT: replacement " #num "\n" \ b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n" /* alternative assembly primitive: */ #define ALTERNATIVE(oldinstr, newinstr, feature) \ OLDINSTR(oldinstr, 1) \ ".pushsection .altinstructions,\"a\"\n" \ ALTINSTR_ENTRY(feature, 1) \ ".popsection\n" \ ".pushsection .altinstr_replacement, \"ax\"\n" \ ALTINSTR_REPLACEMENT(newinstr, feature, 1) \ ".popsection\n" #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ OLDINSTR_2(oldinstr, 1, 2) \ ".pushsection .altinstructions,\"a\"\n" \ ALTINSTR_ENTRY(feature1, 1) \ ALTINSTR_ENTRY(feature2, 2) \ ".popsection\n" \ ".pushsection .altinstr_replacement, \"ax\"\n" \ ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \ ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \ ".popsection\n" #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, feat1, 1) \ ALTINSTR_REPLACEMENT(newinsn2, feat2, 2) \ ALTINSTR_REPLACEMENT(newinsn3, feat3, 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, feature) \ asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") /* * Alternative inline assembly with input. * * Peculiarities: * 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) /* * 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, feature1, newinstr2, \ feature2, input...) \ asm 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, 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) /* * 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, feature1, newfunc2, feature2, \ output, input...) \ asm 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) /* * 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 #endif /* __ASSEMBLY__ */ #endif /* _ASM_X86_ALTERNATIVE_H */