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276 lines
9.6 KiB
276 lines
9.6 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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#ifndef _ASM_X86_ALTERNATIVE_H |
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#define _ASM_X86_ALTERNATIVE_H |
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#ifndef __ASSEMBLY__ |
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#include <linux/types.h> |
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#include <linux/stddef.h> |
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#include <linux/stringify.h> |
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#include <asm/asm.h> |
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/* |
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* Alternative inline assembly for SMP. |
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* |
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* The LOCK_PREFIX macro defined here replaces the LOCK and |
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* LOCK_PREFIX macros used everywhere in the source tree. |
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* |
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* SMP alternatives use the same data structures as the other |
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* alternatives and the X86_FEATURE_UP flag to indicate the case of a |
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* UP system running a SMP kernel. The existing apply_alternatives() |
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* works fine for patching a SMP kernel for UP. |
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* |
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* The SMP alternative tables can be kept after boot and contain both |
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* UP and SMP versions of the instructions to allow switching back to |
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* SMP at runtime, when hotplugging in a new CPU, which is especially |
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* useful in virtualized environments. |
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* |
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* The very common lock prefix is handled as special case in a |
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* separate table which is a pure address list without replacement ptr |
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* and size information. That keeps the table sizes small. |
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*/ |
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#ifdef CONFIG_SMP |
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#define LOCK_PREFIX_HERE \ |
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".pushsection .smp_locks,\"a\"\n" \ |
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".balign 4\n" \ |
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".long 671f - .\n" /* offset */ \ |
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".popsection\n" \ |
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"671:" |
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#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; " |
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#else /* ! CONFIG_SMP */ |
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#define LOCK_PREFIX_HERE "" |
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#define LOCK_PREFIX "" |
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#endif |
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/* |
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* objtool annotation to ignore the alternatives and only consider the original |
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* instruction(s). |
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*/ |
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#define ANNOTATE_IGNORE_ALTERNATIVE \ |
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"999:\n\t" \ |
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".pushsection .discard.ignore_alts\n\t" \ |
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".long 999b - .\n\t" \ |
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".popsection\n\t" |
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struct alt_instr { |
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s32 instr_offset; /* original instruction */ |
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s32 repl_offset; /* offset to replacement instruction */ |
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u16 cpuid; /* cpuid bit set for replacement */ |
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u8 instrlen; /* length of original instruction */ |
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u8 replacementlen; /* length of new instruction */ |
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u8 padlen; /* length of build-time padding */ |
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} __packed; |
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/* |
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* Debug flag that can be tested to see whether alternative |
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* instructions were patched in already: |
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*/ |
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extern int alternatives_patched; |
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extern void alternative_instructions(void); |
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extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end); |
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struct module; |
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#ifdef CONFIG_SMP |
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extern void alternatives_smp_module_add(struct module *mod, char *name, |
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void *locks, void *locks_end, |
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void *text, void *text_end); |
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extern void alternatives_smp_module_del(struct module *mod); |
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extern void alternatives_enable_smp(void); |
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extern int alternatives_text_reserved(void *start, void *end); |
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extern bool skip_smp_alternatives; |
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#else |
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static inline void alternatives_smp_module_add(struct module *mod, char *name, |
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void *locks, void *locks_end, |
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void *text, void *text_end) {} |
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static inline void alternatives_smp_module_del(struct module *mod) {} |
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static inline void alternatives_enable_smp(void) {} |
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static inline int alternatives_text_reserved(void *start, void *end) |
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{ |
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return 0; |
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} |
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#endif /* CONFIG_SMP */ |
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#define b_replacement(num) "664"#num |
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#define e_replacement(num) "665"#num |
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#define alt_end_marker "663" |
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#define alt_slen "662b-661b" |
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#define alt_pad_len alt_end_marker"b-662b" |
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#define alt_total_slen alt_end_marker"b-661b" |
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#define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" |
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#define OLDINSTR(oldinstr, num) \ |
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"# ALT: oldnstr\n" \ |
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"661:\n\t" oldinstr "\n662:\n" \ |
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"# ALT: padding\n" \ |
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".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ |
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"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \ |
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alt_end_marker ":\n" |
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/* |
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* gas compatible max based on the idea from: |
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* http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax |
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* |
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* The additional "-" is needed because gas uses a "true" value of -1. |
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*/ |
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#define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))" |
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/* |
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* Pad the second replacement alternative with additional NOPs if it is |
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* additionally longer than the first replacement alternative. |
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*/ |
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#define OLDINSTR_2(oldinstr, num1, num2) \ |
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"# ALT: oldinstr2\n" \ |
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"661:\n\t" oldinstr "\n662:\n" \ |
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"# ALT: padding2\n" \ |
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".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ |
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"(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ |
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alt_end_marker ":\n" |
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#define OLDINSTR_3(oldinsn, n1, n2, n3) \ |
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"# ALT: oldinstr3\n" \ |
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"661:\n\t" oldinsn "\n662:\n" \ |
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"# ALT: padding3\n" \ |
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".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ |
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" - (" alt_slen ")) > 0) * " \ |
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"(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ |
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" - (" alt_slen ")), 0x90\n" \ |
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alt_end_marker ":\n" |
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#define ALTINSTR_ENTRY(feature, num) \ |
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" .long 661b - .\n" /* label */ \ |
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" .long " b_replacement(num)"f - .\n" /* new instruction */ \ |
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" .word " __stringify(feature) "\n" /* feature bit */ \ |
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" .byte " alt_total_slen "\n" /* source len */ \ |
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" .byte " alt_rlen(num) "\n" /* replacement len */ \ |
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" .byte " alt_pad_len "\n" /* pad len */ |
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#define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \ |
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"# ALT: replacement " #num "\n" \ |
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b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n" |
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/* alternative assembly primitive: */ |
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#define ALTERNATIVE(oldinstr, newinstr, feature) \ |
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OLDINSTR(oldinstr, 1) \ |
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".pushsection .altinstructions,\"a\"\n" \ |
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ALTINSTR_ENTRY(feature, 1) \ |
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".popsection\n" \ |
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".pushsection .altinstr_replacement, \"ax\"\n" \ |
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ALTINSTR_REPLACEMENT(newinstr, feature, 1) \ |
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".popsection\n" |
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#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ |
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OLDINSTR_2(oldinstr, 1, 2) \ |
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".pushsection .altinstructions,\"a\"\n" \ |
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ALTINSTR_ENTRY(feature1, 1) \ |
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ALTINSTR_ENTRY(feature2, 2) \ |
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".popsection\n" \ |
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".pushsection .altinstr_replacement, \"ax\"\n" \ |
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ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \ |
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ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \ |
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".popsection\n" |
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#define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \ |
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OLDINSTR_3(oldinsn, 1, 2, 3) \ |
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".pushsection .altinstructions,\"a\"\n" \ |
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ALTINSTR_ENTRY(feat1, 1) \ |
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ALTINSTR_ENTRY(feat2, 2) \ |
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ALTINSTR_ENTRY(feat3, 3) \ |
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".popsection\n" \ |
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".pushsection .altinstr_replacement, \"ax\"\n" \ |
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ALTINSTR_REPLACEMENT(newinsn1, feat1, 1) \ |
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ALTINSTR_REPLACEMENT(newinsn2, feat2, 2) \ |
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ALTINSTR_REPLACEMENT(newinsn3, feat3, 3) \ |
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".popsection\n" |
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/* |
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* Alternative instructions for different CPU types or capabilities. |
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* |
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* This allows to use optimized instructions even on generic binary |
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* kernels. |
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* |
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* length of oldinstr must be longer or equal the length of newinstr |
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* It can be padded with nops as needed. |
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* |
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* For non barrier like inlines please define new variants |
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* without volatile and memory clobber. |
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*/ |
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#define alternative(oldinstr, newinstr, feature) \ |
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asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") |
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#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ |
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asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") |
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/* |
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* Alternative inline assembly with input. |
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* |
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* Peculiarities: |
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* No memory clobber here. |
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* Argument numbers start with 1. |
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* Best is to use constraints that are fixed size (like (%1) ... "r") |
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* If you use variable sized constraints like "m" or "g" in the |
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* replacement make sure to pad to the worst case length. |
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* Leaving an unused argument 0 to keep API compatibility. |
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*/ |
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#define alternative_input(oldinstr, newinstr, feature, input...) \ |
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asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ |
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: : "i" (0), ## input) |
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/* |
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* This is similar to alternative_input. But it has two features and |
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* respective instructions. |
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* |
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* If CPU has feature2, newinstr2 is used. |
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* Otherwise, if CPU has feature1, newinstr1 is used. |
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* Otherwise, oldinstr is used. |
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*/ |
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#define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \ |
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feature2, input...) \ |
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asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \ |
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newinstr2, feature2) \ |
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: : "i" (0), ## input) |
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/* Like alternative_input, but with a single output argument */ |
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#define alternative_io(oldinstr, newinstr, feature, output, input...) \ |
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asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ |
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: output : "i" (0), ## input) |
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/* Like alternative_io, but for replacing a direct call with another one. */ |
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#define alternative_call(oldfunc, newfunc, feature, output, input...) \ |
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asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ |
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: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) |
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/* |
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* Like alternative_call, but there are two features and respective functions. |
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* If CPU has feature2, function2 is used. |
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* Otherwise, if CPU has feature1, function1 is used. |
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* Otherwise, old function is used. |
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*/ |
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#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ |
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output, input...) \ |
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asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ |
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"call %P[new2]", feature2) \ |
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: output, ASM_CALL_CONSTRAINT \ |
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: [old] "i" (oldfunc), [new1] "i" (newfunc1), \ |
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[new2] "i" (newfunc2), ## input) |
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/* |
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* use this macro(s) if you need more than one output parameter |
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* in alternative_io |
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*/ |
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#define ASM_OUTPUT2(a...) a |
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/* |
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* use this macro if you need clobbers but no inputs in |
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* alternative_{input,io,call}() |
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*/ |
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#define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr |
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#endif /* __ASSEMBLY__ */ |
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#endif /* _ASM_X86_ALTERNATIVE_H */
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