1 #ifndef __ASM_ALTERNATIVE_H 2 #define __ASM_ALTERNATIVE_H 3 4 #include <asm/cpufeature.h> 5 6 #ifndef __ASSEMBLY__ 7 8 #include <linux/init.h> 9 #include <linux/kconfig.h> 10 #include <linux/types.h> 11 #include <linux/stddef.h> 12 #include <linux/stringify.h> 13 14 struct alt_instr { 15 s32 orig_offset; /* offset to original instruction */ 16 s32 alt_offset; /* offset to replacement instruction */ 17 u16 cpufeature; /* cpufeature bit set for replacement */ 18 u8 orig_len; /* size of original instruction(s) */ 19 u8 alt_len; /* size of new instruction(s), <= orig_len */ 20 }; 21 22 void __init apply_alternatives_all(void); 23 void apply_alternatives(void *start, size_t length); 24 25 #define ALTINSTR_ENTRY(feature) \ 26 " .word 661b - .\n" /* label */ \ 27 " .word 663f - .\n" /* new instruction */ \ 28 " .hword " __stringify(feature) "\n" /* feature bit */ \ 29 " .byte 662b-661b\n" /* source len */ \ 30 " .byte 664f-663f\n" /* replacement len */ 31 32 /* 33 * alternative assembly primitive: 34 * 35 * If any of these .org directive fail, it means that insn1 and insn2 36 * don't have the same length. This used to be written as 37 * 38 * .if ((664b-663b) != (662b-661b)) 39 * .error "Alternatives instruction length mismatch" 40 * .endif 41 * 42 * but most assemblers die if insn1 or insn2 have a .inst. This should 43 * be fixed in a binutils release posterior to 2.25.51.0.2 (anything 44 * containing commit 4e4d08cf7399b606 or c1baaddf8861). 45 */ 46 #define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \ 47 ".if "__stringify(cfg_enabled)" == 1\n" \ 48 "661:\n\t" \ 49 oldinstr "\n" \ 50 "662:\n" \ 51 ".pushsection .altinstructions,\"a\"\n" \ 52 ALTINSTR_ENTRY(feature) \ 53 ".popsection\n" \ 54 ".pushsection .altinstr_replacement, \"a\"\n" \ 55 "663:\n\t" \ 56 newinstr "\n" \ 57 "664:\n\t" \ 58 ".popsection\n\t" \ 59 ".org . - (664b-663b) + (662b-661b)\n\t" \ 60 ".org . - (662b-661b) + (664b-663b)\n" \ 61 ".endif\n" 62 63 #define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \ 64 __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg)) 65 66 #else 67 68 #include <asm/assembler.h> 69 70 .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len 71 .word \orig_offset - . 72 .word \alt_offset - . 73 .hword \feature 74 .byte \orig_len 75 .byte \alt_len 76 .endm 77 78 .macro alternative_insn insn1, insn2, cap, enable = 1 79 .if \enable 80 661: \insn1 81 662: .pushsection .altinstructions, "a" 82 altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f 83 .popsection 84 .pushsection .altinstr_replacement, "ax" 85 663: \insn2 86 664: .popsection 87 .org . - (664b-663b) + (662b-661b) 88 .org . - (662b-661b) + (664b-663b) 89 .endif 90 .endm 91 92 /* 93 * Begin an alternative code sequence. 94 * 95 * The code that follows this macro will be assembled and linked as 96 * normal. There are no restrictions on this code. 97 */ 98 .macro alternative_if_not cap, enable = 1 99 .if \enable 100 .pushsection .altinstructions, "a" 101 altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f 102 .popsection 103 661: 104 .endif 105 .endm 106 107 /* 108 * Provide the alternative code sequence. 109 * 110 * The code that follows this macro is assembled into a special 111 * section to be used for dynamic patching. Code that follows this 112 * macro must: 113 * 114 * 1. Be exactly the same length (in bytes) as the default code 115 * sequence. 116 * 117 * 2. Not contain a branch target that is used outside of the 118 * alternative sequence it is defined in (branches into an 119 * alternative sequence are not fixed up). 120 */ 121 .macro alternative_else, enable = 1 122 .if \enable 123 662: .pushsection .altinstr_replacement, "ax" 124 663: 125 .endif 126 .endm 127 128 /* 129 * Complete an alternative code sequence. 130 */ 131 .macro alternative_endif, enable = 1 132 .if \enable 133 664: .popsection 134 .org . - (664b-663b) + (662b-661b) 135 .org . - (662b-661b) + (664b-663b) 136 .endif 137 .endm 138 139 #define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \ 140 alternative_insn insn1, insn2, cap, IS_ENABLED(cfg) 141 142 143 /* 144 * Generate the assembly for UAO alternatives with exception table entries. 145 * This is complicated as there is no post-increment or pair versions of the 146 * unprivileged instructions, and USER() only works for single instructions. 147 */ 148 #ifdef CONFIG_ARM64_UAO 149 .macro uao_ldp l, reg1, reg2, addr, post_inc 150 alternative_if_not ARM64_HAS_UAO 151 8888: ldp \reg1, \reg2, [\addr], \post_inc; 152 8889: nop; 153 nop; 154 alternative_else 155 ldtr \reg1, [\addr]; 156 ldtr \reg2, [\addr, #8]; 157 add \addr, \addr, \post_inc; 158 alternative_endif 159 160 .section __ex_table,"a"; 161 .align 3; 162 .quad 8888b,\l; 163 .quad 8889b,\l; 164 .previous; 165 .endm 166 167 .macro uao_stp l, reg1, reg2, addr, post_inc 168 alternative_if_not ARM64_HAS_UAO 169 8888: stp \reg1, \reg2, [\addr], \post_inc; 170 8889: nop; 171 nop; 172 alternative_else 173 sttr \reg1, [\addr]; 174 sttr \reg2, [\addr, #8]; 175 add \addr, \addr, \post_inc; 176 alternative_endif 177 178 .section __ex_table,"a"; 179 .align 3; 180 .quad 8888b,\l; 181 .quad 8889b,\l; 182 .previous 183 .endm 184 185 .macro uao_user_alternative l, inst, alt_inst, reg, addr, post_inc 186 alternative_if_not ARM64_HAS_UAO 187 8888: \inst \reg, [\addr], \post_inc; 188 nop; 189 alternative_else 190 \alt_inst \reg, [\addr]; 191 add \addr, \addr, \post_inc; 192 alternative_endif 193 194 .section __ex_table,"a"; 195 .align 3; 196 .quad 8888b,\l; 197 .previous 198 .endm 199 #else 200 .macro uao_ldp l, reg1, reg2, addr, post_inc 201 USER(\l, ldp \reg1, \reg2, [\addr], \post_inc) 202 .endm 203 .macro uao_stp l, reg1, reg2, addr, post_inc 204 USER(\l, stp \reg1, \reg2, [\addr], \post_inc) 205 .endm 206 .macro uao_user_alternative l, inst, alt_inst, reg, addr, post_inc 207 USER(\l, \inst \reg, [\addr], \post_inc) 208 .endm 209 #endif 210 211 #endif /* __ASSEMBLY__ */ 212 213 /* 214 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature)); 215 * 216 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO)); 217 * N.B. If CONFIG_FOO is specified, but not selected, the whole block 218 * will be omitted, including oldinstr. 219 */ 220 #define ALTERNATIVE(oldinstr, newinstr, ...) \ 221 _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1) 222 223 #endif /* __ASM_ALTERNATIVE_H */ 224