1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __ASM_ALTERNATIVE_H 3 #define __ASM_ALTERNATIVE_H 4 5 #include <asm/cpucaps.h> 6 #include <asm/insn.h> 7 8 #define ARM64_CB_PATCH ARM64_NCAPS 9 10 #ifndef __ASSEMBLY__ 11 12 #include <linux/init.h> 13 #include <linux/types.h> 14 #include <linux/stddef.h> 15 #include <linux/stringify.h> 16 17 struct alt_instr { 18 s32 orig_offset; /* offset to original instruction */ 19 s32 alt_offset; /* offset to replacement instruction */ 20 u16 cpufeature; /* cpufeature bit set for replacement */ 21 u8 orig_len; /* size of original instruction(s) */ 22 u8 alt_len; /* size of new instruction(s), <= orig_len */ 23 }; 24 25 typedef void (*alternative_cb_t)(struct alt_instr *alt, 26 __le32 *origptr, __le32 *updptr, int nr_inst); 27 28 void __init apply_boot_alternatives(void); 29 void __init apply_alternatives_all(void); 30 bool alternative_is_applied(u16 cpufeature); 31 32 #ifdef CONFIG_MODULES 33 void apply_alternatives_module(void *start, size_t length); 34 #else 35 static inline void apply_alternatives_module(void *start, size_t length) { } 36 #endif 37 38 #define ALTINSTR_ENTRY(feature) \ 39 " .word 661b - .\n" /* label */ \ 40 " .word 663f - .\n" /* new instruction */ \ 41 " .hword " __stringify(feature) "\n" /* feature bit */ \ 42 " .byte 662b-661b\n" /* source len */ \ 43 " .byte 664f-663f\n" /* replacement len */ 44 45 #define ALTINSTR_ENTRY_CB(feature, cb) \ 46 " .word 661b - .\n" /* label */ \ 47 " .word " __stringify(cb) "- .\n" /* callback */ \ 48 " .hword " __stringify(feature) "\n" /* feature bit */ \ 49 " .byte 662b-661b\n" /* source len */ \ 50 " .byte 664f-663f\n" /* replacement len */ 51 52 /* 53 * alternative assembly primitive: 54 * 55 * If any of these .org directive fail, it means that insn1 and insn2 56 * don't have the same length. This used to be written as 57 * 58 * .if ((664b-663b) != (662b-661b)) 59 * .error "Alternatives instruction length mismatch" 60 * .endif 61 * 62 * but most assemblers die if insn1 or insn2 have a .inst. This should 63 * be fixed in a binutils release posterior to 2.25.51.0.2 (anything 64 * containing commit 4e4d08cf7399b606 or c1baaddf8861). 65 * 66 * Alternatives with callbacks do not generate replacement instructions. 67 */ 68 #define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \ 69 ".if "__stringify(cfg_enabled)" == 1\n" \ 70 "661:\n\t" \ 71 oldinstr "\n" \ 72 "662:\n" \ 73 ".pushsection .altinstructions,\"a\"\n" \ 74 ALTINSTR_ENTRY(feature) \ 75 ".popsection\n" \ 76 ".pushsection .altinstr_replacement, \"a\"\n" \ 77 "663:\n\t" \ 78 newinstr "\n" \ 79 "664:\n\t" \ 80 ".popsection\n\t" \ 81 ".org . - (664b-663b) + (662b-661b)\n\t" \ 82 ".org . - (662b-661b) + (664b-663b)\n" \ 83 ".endif\n" 84 85 #define __ALTERNATIVE_CFG_CB(oldinstr, feature, cfg_enabled, cb) \ 86 ".if "__stringify(cfg_enabled)" == 1\n" \ 87 "661:\n\t" \ 88 oldinstr "\n" \ 89 "662:\n" \ 90 ".pushsection .altinstructions,\"a\"\n" \ 91 ALTINSTR_ENTRY_CB(feature, cb) \ 92 ".popsection\n" \ 93 "663:\n\t" \ 94 "664:\n\t" \ 95 ".endif\n" 96 97 #define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \ 98 __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg)) 99 100 #define ALTERNATIVE_CB(oldinstr, cb) \ 101 __ALTERNATIVE_CFG_CB(oldinstr, ARM64_CB_PATCH, 1, cb) 102 #else 103 104 #include <asm/assembler.h> 105 106 .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len 107 .word \orig_offset - . 108 .word \alt_offset - . 109 .hword \feature 110 .byte \orig_len 111 .byte \alt_len 112 .endm 113 114 .macro alternative_insn insn1, insn2, cap, enable = 1 115 .if \enable 116 661: \insn1 117 662: .pushsection .altinstructions, "a" 118 altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f 119 .popsection 120 .pushsection .altinstr_replacement, "ax" 121 663: \insn2 122 664: .popsection 123 .org . - (664b-663b) + (662b-661b) 124 .org . - (662b-661b) + (664b-663b) 125 .endif 126 .endm 127 128 /* 129 * Alternative sequences 130 * 131 * The code for the case where the capability is not present will be 132 * assembled and linked as normal. There are no restrictions on this 133 * code. 134 * 135 * The code for the case where the capability is present will be 136 * assembled into a special section to be used for dynamic patching. 137 * Code for that case must: 138 * 139 * 1. Be exactly the same length (in bytes) as the default code 140 * sequence. 141 * 142 * 2. Not contain a branch target that is used outside of the 143 * alternative sequence it is defined in (branches into an 144 * alternative sequence are not fixed up). 145 */ 146 147 /* 148 * Begin an alternative code sequence. 149 */ 150 .macro alternative_if_not cap 151 .set .Lasm_alt_mode, 0 152 .pushsection .altinstructions, "a" 153 altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f 154 .popsection 155 661: 156 .endm 157 158 .macro alternative_if cap 159 .set .Lasm_alt_mode, 1 160 .pushsection .altinstructions, "a" 161 altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f 162 .popsection 163 .pushsection .altinstr_replacement, "ax" 164 .align 2 /* So GAS knows label 661 is suitably aligned */ 165 661: 166 .endm 167 168 .macro alternative_cb cb 169 .set .Lasm_alt_mode, 0 170 .pushsection .altinstructions, "a" 171 altinstruction_entry 661f, \cb, ARM64_CB_PATCH, 662f-661f, 0 172 .popsection 173 661: 174 .endm 175 176 /* 177 * Provide the other half of the alternative code sequence. 178 */ 179 .macro alternative_else 180 662: 181 .if .Lasm_alt_mode==0 182 .pushsection .altinstr_replacement, "ax" 183 .else 184 .popsection 185 .endif 186 663: 187 .endm 188 189 /* 190 * Complete an alternative code sequence. 191 */ 192 .macro alternative_endif 193 664: 194 .if .Lasm_alt_mode==0 195 .popsection 196 .endif 197 .org . - (664b-663b) + (662b-661b) 198 .org . - (662b-661b) + (664b-663b) 199 .endm 200 201 /* 202 * Callback-based alternative epilogue 203 */ 204 .macro alternative_cb_end 205 662: 206 .endm 207 208 /* 209 * Provides a trivial alternative or default sequence consisting solely 210 * of NOPs. The number of NOPs is chosen automatically to match the 211 * previous case. 212 */ 213 .macro alternative_else_nop_endif 214 alternative_else 215 nops (662b-661b) / AARCH64_INSN_SIZE 216 alternative_endif 217 .endm 218 219 #define _ALTERNATIVE_CFG(insn1, insn2, cap, cfg, ...) \ 220 alternative_insn insn1, insn2, cap, IS_ENABLED(cfg) 221 222 .macro user_alt, label, oldinstr, newinstr, cond 223 9999: alternative_insn "\oldinstr", "\newinstr", \cond 224 _asm_extable 9999b, \label 225 .endm 226 227 /* 228 * Generate the assembly for UAO alternatives with exception table entries. 229 * This is complicated as there is no post-increment or pair versions of the 230 * unprivileged instructions, and USER() only works for single instructions. 231 */ 232 #ifdef CONFIG_ARM64_UAO 233 .macro uao_ldp l, reg1, reg2, addr, post_inc 234 alternative_if_not ARM64_HAS_UAO 235 8888: ldp \reg1, \reg2, [\addr], \post_inc; 236 8889: nop; 237 nop; 238 alternative_else 239 ldtr \reg1, [\addr]; 240 ldtr \reg2, [\addr, #8]; 241 add \addr, \addr, \post_inc; 242 alternative_endif 243 244 _asm_extable 8888b,\l; 245 _asm_extable 8889b,\l; 246 .endm 247 248 .macro uao_stp l, reg1, reg2, addr, post_inc 249 alternative_if_not ARM64_HAS_UAO 250 8888: stp \reg1, \reg2, [\addr], \post_inc; 251 8889: nop; 252 nop; 253 alternative_else 254 sttr \reg1, [\addr]; 255 sttr \reg2, [\addr, #8]; 256 add \addr, \addr, \post_inc; 257 alternative_endif 258 259 _asm_extable 8888b,\l; 260 _asm_extable 8889b,\l; 261 .endm 262 263 .macro uao_user_alternative l, inst, alt_inst, reg, addr, post_inc 264 alternative_if_not ARM64_HAS_UAO 265 8888: \inst \reg, [\addr], \post_inc; 266 nop; 267 alternative_else 268 \alt_inst \reg, [\addr]; 269 add \addr, \addr, \post_inc; 270 alternative_endif 271 272 _asm_extable 8888b,\l; 273 .endm 274 #else 275 .macro uao_ldp l, reg1, reg2, addr, post_inc 276 USER(\l, ldp \reg1, \reg2, [\addr], \post_inc) 277 .endm 278 .macro uao_stp l, reg1, reg2, addr, post_inc 279 USER(\l, stp \reg1, \reg2, [\addr], \post_inc) 280 .endm 281 .macro uao_user_alternative l, inst, alt_inst, reg, addr, post_inc 282 USER(\l, \inst \reg, [\addr], \post_inc) 283 .endm 284 #endif 285 286 #endif /* __ASSEMBLY__ */ 287 288 /* 289 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature)); 290 * 291 * Usage: asm(ALTERNATIVE(oldinstr, newinstr, feature, CONFIG_FOO)); 292 * N.B. If CONFIG_FOO is specified, but not selected, the whole block 293 * will be omitted, including oldinstr. 294 */ 295 #define ALTERNATIVE(oldinstr, newinstr, ...) \ 296 _ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1) 297 298 #endif /* __ASM_ALTERNATIVE_H */ 299