1 #ifndef __ASM_ALTERNATIVE_H 2 #define __ASM_ALTERNATIVE_H 3 4 #ifndef __ASSEMBLY__ 5 6 #include <linux/init.h> 7 #include <linux/kconfig.h> 8 #include <linux/types.h> 9 #include <linux/stddef.h> 10 #include <linux/stringify.h> 11 12 struct alt_instr { 13 s32 orig_offset; /* offset to original instruction */ 14 s32 alt_offset; /* offset to replacement instruction */ 15 u16 cpufeature; /* cpufeature bit set for replacement */ 16 u8 orig_len; /* size of original instruction(s) */ 17 u8 alt_len; /* size of new instruction(s), <= orig_len */ 18 }; 19 20 void __init apply_alternatives_all(void); 21 void apply_alternatives(void *start, size_t length); 22 void free_alternatives_memory(void); 23 24 #define ALTINSTR_ENTRY(feature) \ 25 " .word 661b - .\n" /* label */ \ 26 " .word 663f - .\n" /* new instruction */ \ 27 " .hword " __stringify(feature) "\n" /* feature bit */ \ 28 " .byte 662b-661b\n" /* source len */ \ 29 " .byte 664f-663f\n" /* replacement len */ 30 31 /* 32 * alternative assembly primitive: 33 * 34 * If any of these .org directive fail, it means that insn1 and insn2 35 * don't have the same length. This used to be written as 36 * 37 * .if ((664b-663b) != (662b-661b)) 38 * .error "Alternatives instruction length mismatch" 39 * .endif 40 * 41 * but most assemblers die if insn1 or insn2 have a .inst. This should 42 * be fixed in a binutils release posterior to 2.25.51.0.2 (anything 43 * containing commit 4e4d08cf7399b606 or c1baaddf8861). 44 */ 45 #define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \ 46 ".if "__stringify(cfg_enabled)" == 1\n" \ 47 "661:\n\t" \ 48 oldinstr "\n" \ 49 "662:\n" \ 50 ".pushsection .altinstructions,\"a\"\n" \ 51 ALTINSTR_ENTRY(feature) \ 52 ".popsection\n" \ 53 ".pushsection .altinstr_replacement, \"a\"\n" \ 54 "663:\n\t" \ 55 newinstr "\n" \ 56 "664:\n\t" \ 57 ".popsection\n\t" \ 58 ".org . - (664b-663b) + (662b-661b)\n\t" \ 59 ".org . - (662b-661b) + (664b-663b)\n" \ 60 ".endif\n" 61 62 #define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \ 63 __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg)) 64 65 #else 66 67 .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len 68 .word \orig_offset - . 69 .word \alt_offset - . 70 .hword \feature 71 .byte \orig_len 72 .byte \alt_len 73 .endm 74 75 .macro alternative_insn insn1, insn2, cap, enable = 1 76 .if \enable 77 661: \insn1 78 662: .pushsection .altinstructions, "a" 79 altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f 80 .popsection 81 .pushsection .altinstr_replacement, "ax" 82 663: \insn2 83 664: .popsection 84 .org . - (664b-663b) + (662b-661b) 85 .org . - (662b-661b) + (664b-663b) 86 .endif 87 .endm 88 89 /* 90 * Begin an alternative code sequence. 91 * 92 * The code that follows this macro will be assembled and linked as 93 * normal. There are no restrictions on this code. 94 */ 95 .macro alternative_if_not cap, enable = 1 96 .if \enable 97 .pushsection .altinstructions, "a" 98 altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f 99 .popsection 100 661: 101 .endif 102 .endm 103 104 /* 105 * Provide the alternative code sequence. 106 * 107 * The code that follows this macro is assembled into a special 108 * section to be used for dynamic patching. Code that follows this 109 * macro must: 110 * 111 * 1. Be exactly the same length (in bytes) as the default code 112 * sequence. 113 * 114 * 2. Not contain a branch target that is used outside of the 115 * alternative sequence it is defined in (branches into an 116 * alternative sequence are not fixed up). 117 */ 118 .macro alternative_else, enable = 1 119 .if \enable 120 662: .pushsection .altinstr_replacement, "ax" 121 663: 122 .endif 123 .endm 124 125 /* 126 * Complete an alternative code sequence. 127 */ 128 .macro alternative_endif, enable = 1 129 .if \enable 130 664: .popsection 131 .org . - (664b-663b) + (662b-661b) 132 .org . - (662b-661b) + (664b-663b) 133 .endif 134 .endm 135 136 #define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \ 137 alternative_insn insn1, insn2, cap, IS_ENABLED(cfg) 138 139 140 #endif /* __ASSEMBLY__ */ 141 142 /* 143 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature)); 144 * 145 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO)); 146 * N.B. If CONFIG_FOO is specified, but not selected, the whole block 147 * will be omitted, including oldinstr. 148 */ 149 #define ALTERNATIVE(oldinstr, newinstr, ...) \ 150 _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1) 151 152 #endif /* __ASM_ALTERNATIVE_H */ 153