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