1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_X86_ALTERNATIVE_H 3 #define _ASM_X86_ALTERNATIVE_H 4 5 #include <linux/types.h> 6 #include <linux/stringify.h> 7 #include <asm/asm.h> 8 9 #define ALT_FLAGS_SHIFT 16 10 11 #define ALT_FLAG_NOT (1 << 0) 12 #define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature)) 13 14 #ifndef __ASSEMBLY__ 15 16 #include <linux/stddef.h> 17 18 /* 19 * Alternative inline assembly for SMP. 20 * 21 * The LOCK_PREFIX macro defined here replaces the LOCK and 22 * LOCK_PREFIX macros used everywhere in the source tree. 23 * 24 * SMP alternatives use the same data structures as the other 25 * alternatives and the X86_FEATURE_UP flag to indicate the case of a 26 * UP system running a SMP kernel. The existing apply_alternatives() 27 * works fine for patching a SMP kernel for UP. 28 * 29 * The SMP alternative tables can be kept after boot and contain both 30 * UP and SMP versions of the instructions to allow switching back to 31 * SMP at runtime, when hotplugging in a new CPU, which is especially 32 * useful in virtualized environments. 33 * 34 * The very common lock prefix is handled as special case in a 35 * separate table which is a pure address list without replacement ptr 36 * and size information. That keeps the table sizes small. 37 */ 38 39 #ifdef CONFIG_SMP 40 #define LOCK_PREFIX_HERE \ 41 ".pushsection .smp_locks,\"a\"\n" \ 42 ".balign 4\n" \ 43 ".long 671f - .\n" /* offset */ \ 44 ".popsection\n" \ 45 "671:" 46 47 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; " 48 49 #else /* ! CONFIG_SMP */ 50 #define LOCK_PREFIX_HERE "" 51 #define LOCK_PREFIX "" 52 #endif 53 54 /* 55 * objtool annotation to ignore the alternatives and only consider the original 56 * instruction(s). 57 */ 58 #define ANNOTATE_IGNORE_ALTERNATIVE \ 59 "999:\n\t" \ 60 ".pushsection .discard.ignore_alts\n\t" \ 61 ".long 999b - .\n\t" \ 62 ".popsection\n\t" 63 64 /* 65 * The patching flags are part of the upper bits of the @ft_flags parameter when 66 * specifying them. The split is currently like this: 67 * 68 * [31... flags ...16][15... CPUID feature bit ...0] 69 * 70 * but since this is all hidden in the macros argument being split, those fields can be 71 * extended in the future to fit in a u64 or however the need arises. 72 */ 73 struct alt_instr { 74 s32 instr_offset; /* original instruction */ 75 s32 repl_offset; /* offset to replacement instruction */ 76 77 union { 78 struct { 79 u32 cpuid: 16; /* CPUID bit set for replacement */ 80 u32 flags: 16; /* patching control flags */ 81 }; 82 u32 ft_flags; 83 }; 84 85 u8 instrlen; /* length of original instruction */ 86 u8 replacementlen; /* length of new instruction */ 87 } __packed; 88 89 /* 90 * Debug flag that can be tested to see whether alternative 91 * instructions were patched in already: 92 */ 93 extern int alternatives_patched; 94 95 extern void alternative_instructions(void); 96 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end); 97 extern void apply_retpolines(s32 *start, s32 *end); 98 extern void apply_returns(s32 *start, s32 *end); 99 extern void apply_ibt_endbr(s32 *start, s32 *end); 100 extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine, 101 s32 *start_cfi, s32 *end_cfi); 102 103 struct module; 104 struct paravirt_patch_site; 105 106 struct callthunk_sites { 107 s32 *call_start, *call_end; 108 struct paravirt_patch_site *pv_start, *pv_end; 109 }; 110 111 #ifdef CONFIG_CALL_THUNKS 112 extern void callthunks_patch_builtin_calls(void); 113 extern void callthunks_patch_module_calls(struct callthunk_sites *sites, 114 struct module *mod); 115 extern void *callthunks_translate_call_dest(void *dest); 116 extern int x86_call_depth_emit_accounting(u8 **pprog, void *func); 117 #else 118 static __always_inline void callthunks_patch_builtin_calls(void) {} 119 static __always_inline void 120 callthunks_patch_module_calls(struct callthunk_sites *sites, 121 struct module *mod) {} 122 static __always_inline void *callthunks_translate_call_dest(void *dest) 123 { 124 return dest; 125 } 126 static __always_inline int x86_call_depth_emit_accounting(u8 **pprog, 127 void *func) 128 { 129 return 0; 130 } 131 #endif 132 133 #ifdef CONFIG_SMP 134 extern void alternatives_smp_module_add(struct module *mod, char *name, 135 void *locks, void *locks_end, 136 void *text, void *text_end); 137 extern void alternatives_smp_module_del(struct module *mod); 138 extern void alternatives_enable_smp(void); 139 extern int alternatives_text_reserved(void *start, void *end); 140 extern bool skip_smp_alternatives; 141 #else 142 static inline void alternatives_smp_module_add(struct module *mod, char *name, 143 void *locks, void *locks_end, 144 void *text, void *text_end) {} 145 static inline void alternatives_smp_module_del(struct module *mod) {} 146 static inline void alternatives_enable_smp(void) {} 147 static inline int alternatives_text_reserved(void *start, void *end) 148 { 149 return 0; 150 } 151 #endif /* CONFIG_SMP */ 152 153 #define b_replacement(num) "664"#num 154 #define e_replacement(num) "665"#num 155 156 #define alt_end_marker "663" 157 #define alt_slen "662b-661b" 158 #define alt_total_slen alt_end_marker"b-661b" 159 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" 160 161 #define OLDINSTR(oldinstr, num) \ 162 "# ALT: oldnstr\n" \ 163 "661:\n\t" oldinstr "\n662:\n" \ 164 "# ALT: padding\n" \ 165 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ 166 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \ 167 alt_end_marker ":\n" 168 169 /* 170 * gas compatible max based on the idea from: 171 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 172 * 173 * The additional "-" is needed because gas uses a "true" value of -1. 174 */ 175 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))" 176 177 /* 178 * Pad the second replacement alternative with additional NOPs if it is 179 * additionally longer than the first replacement alternative. 180 */ 181 #define OLDINSTR_2(oldinstr, num1, num2) \ 182 "# ALT: oldinstr2\n" \ 183 "661:\n\t" oldinstr "\n662:\n" \ 184 "# ALT: padding2\n" \ 185 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ 186 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ 187 alt_end_marker ":\n" 188 189 #define OLDINSTR_3(oldinsn, n1, n2, n3) \ 190 "# ALT: oldinstr3\n" \ 191 "661:\n\t" oldinsn "\n662:\n" \ 192 "# ALT: padding3\n" \ 193 ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 194 " - (" alt_slen ")) > 0) * " \ 195 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 196 " - (" alt_slen ")), 0x90\n" \ 197 alt_end_marker ":\n" 198 199 #define ALTINSTR_ENTRY(ft_flags, num) \ 200 " .long 661b - .\n" /* label */ \ 201 " .long " b_replacement(num)"f - .\n" /* new instruction */ \ 202 " .4byte " __stringify(ft_flags) "\n" /* feature + flags */ \ 203 " .byte " alt_total_slen "\n" /* source len */ \ 204 " .byte " alt_rlen(num) "\n" /* replacement len */ 205 206 #define ALTINSTR_REPLACEMENT(newinstr, num) /* replacement */ \ 207 "# ALT: replacement " #num "\n" \ 208 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n" 209 210 /* alternative assembly primitive: */ 211 #define ALTERNATIVE(oldinstr, newinstr, ft_flags) \ 212 OLDINSTR(oldinstr, 1) \ 213 ".pushsection .altinstructions,\"a\"\n" \ 214 ALTINSTR_ENTRY(ft_flags, 1) \ 215 ".popsection\n" \ 216 ".pushsection .altinstr_replacement, \"ax\"\n" \ 217 ALTINSTR_REPLACEMENT(newinstr, 1) \ 218 ".popsection\n" 219 220 #define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \ 221 OLDINSTR_2(oldinstr, 1, 2) \ 222 ".pushsection .altinstructions,\"a\"\n" \ 223 ALTINSTR_ENTRY(ft_flags1, 1) \ 224 ALTINSTR_ENTRY(ft_flags2, 2) \ 225 ".popsection\n" \ 226 ".pushsection .altinstr_replacement, \"ax\"\n" \ 227 ALTINSTR_REPLACEMENT(newinstr1, 1) \ 228 ALTINSTR_REPLACEMENT(newinstr2, 2) \ 229 ".popsection\n" 230 231 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 232 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \ 233 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 234 newinstr_yes, ft_flags) 235 236 #define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \ 237 newinsn3, ft_flags3) \ 238 OLDINSTR_3(oldinsn, 1, 2, 3) \ 239 ".pushsection .altinstructions,\"a\"\n" \ 240 ALTINSTR_ENTRY(ft_flags1, 1) \ 241 ALTINSTR_ENTRY(ft_flags2, 2) \ 242 ALTINSTR_ENTRY(ft_flags3, 3) \ 243 ".popsection\n" \ 244 ".pushsection .altinstr_replacement, \"ax\"\n" \ 245 ALTINSTR_REPLACEMENT(newinsn1, 1) \ 246 ALTINSTR_REPLACEMENT(newinsn2, 2) \ 247 ALTINSTR_REPLACEMENT(newinsn3, 3) \ 248 ".popsection\n" 249 250 /* 251 * Alternative instructions for different CPU types or capabilities. 252 * 253 * This allows to use optimized instructions even on generic binary 254 * kernels. 255 * 256 * length of oldinstr must be longer or equal the length of newinstr 257 * It can be padded with nops as needed. 258 * 259 * For non barrier like inlines please define new variants 260 * without volatile and memory clobber. 261 */ 262 #define alternative(oldinstr, newinstr, ft_flags) \ 263 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory") 264 265 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \ 266 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory") 267 268 #define alternative_ternary(oldinstr, ft_flags, newinstr_yes, newinstr_no) \ 269 asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) ::: "memory") 270 271 /* 272 * Alternative inline assembly with input. 273 * 274 * Peculiarities: 275 * No memory clobber here. 276 * Argument numbers start with 1. 277 * Leaving an unused argument 0 to keep API compatibility. 278 */ 279 #define alternative_input(oldinstr, newinstr, ft_flags, input...) \ 280 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) \ 281 : : "i" (0), ## input) 282 283 /* 284 * This is similar to alternative_input. But it has two features and 285 * respective instructions. 286 * 287 * If CPU has feature2, newinstr2 is used. 288 * Otherwise, if CPU has feature1, newinstr1 is used. 289 * Otherwise, oldinstr is used. 290 */ 291 #define alternative_input_2(oldinstr, newinstr1, ft_flags1, newinstr2, \ 292 ft_flags2, input...) \ 293 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, \ 294 newinstr2, ft_flags2) \ 295 : : "i" (0), ## input) 296 297 /* Like alternative_input, but with a single output argument */ 298 #define alternative_io(oldinstr, newinstr, ft_flags, output, input...) \ 299 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) \ 300 : output : "i" (0), ## input) 301 302 /* Like alternative_io, but for replacing a direct call with another one. */ 303 #define alternative_call(oldfunc, newfunc, ft_flags, output, input...) \ 304 asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \ 305 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) 306 307 /* 308 * Like alternative_call, but there are two features and respective functions. 309 * If CPU has feature2, function2 is used. 310 * Otherwise, if CPU has feature1, function1 is used. 311 * Otherwise, old function is used. 312 */ 313 #define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2, \ 314 output, input...) \ 315 asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,\ 316 "call %P[new2]", ft_flags2) \ 317 : output, ASM_CALL_CONSTRAINT \ 318 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 319 [new2] "i" (newfunc2), ## input) 320 321 /* 322 * use this macro(s) if you need more than one output parameter 323 * in alternative_io 324 */ 325 #define ASM_OUTPUT2(a...) a 326 327 /* 328 * use this macro if you need clobbers but no inputs in 329 * alternative_{input,io,call}() 330 */ 331 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr 332 333 #else /* __ASSEMBLY__ */ 334 335 #ifdef CONFIG_SMP 336 .macro LOCK_PREFIX 337 672: lock 338 .pushsection .smp_locks,"a" 339 .balign 4 340 .long 672b - . 341 .popsection 342 .endm 343 #else 344 .macro LOCK_PREFIX 345 .endm 346 #endif 347 348 /* 349 * objtool annotation to ignore the alternatives and only consider the original 350 * instruction(s). 351 */ 352 .macro ANNOTATE_IGNORE_ALTERNATIVE 353 .Lannotate_\@: 354 .pushsection .discard.ignore_alts 355 .long .Lannotate_\@ - . 356 .popsection 357 .endm 358 359 /* 360 * Issue one struct alt_instr descriptor entry (need to put it into 361 * the section .altinstructions, see below). This entry contains 362 * enough information for the alternatives patching code to patch an 363 * instruction. See apply_alternatives(). 364 */ 365 .macro altinstr_entry orig alt ft_flags orig_len alt_len 366 .long \orig - . 367 .long \alt - . 368 .4byte \ft_flags 369 .byte \orig_len 370 .byte \alt_len 371 .endm 372 373 /* 374 * Define an alternative between two instructions. If @feature is 375 * present, early code in apply_alternatives() replaces @oldinstr with 376 * @newinstr. ".skip" directive takes care of proper instruction padding 377 * in case @newinstr is longer than @oldinstr. 378 */ 379 .macro ALTERNATIVE oldinstr, newinstr, ft_flags 380 140: 381 \oldinstr 382 141: 383 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90 384 142: 385 386 .pushsection .altinstructions,"a" 387 altinstr_entry 140b,143f,\ft_flags,142b-140b,144f-143f 388 .popsection 389 390 .pushsection .altinstr_replacement,"ax" 391 143: 392 \newinstr 393 144: 394 .popsection 395 .endm 396 397 #define old_len 141b-140b 398 #define new_len1 144f-143f 399 #define new_len2 145f-144f 400 #define new_len3 146f-145f 401 402 /* 403 * gas compatible max based on the idea from: 404 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 405 * 406 * The additional "-" is needed because gas uses a "true" value of -1. 407 */ 408 #define alt_max_2(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b))))) 409 #define alt_max_3(a, b, c) (alt_max_2(alt_max_2(a, b), c)) 410 411 412 /* 413 * Same as ALTERNATIVE macro above but for two alternatives. If CPU 414 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has 415 * @feature2, it replaces @oldinstr with @feature2. 416 */ 417 .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2 418 140: 419 \oldinstr 420 141: 421 .skip -((alt_max_2(new_len1, new_len2) - (old_len)) > 0) * \ 422 (alt_max_2(new_len1, new_len2) - (old_len)),0x90 423 142: 424 425 .pushsection .altinstructions,"a" 426 altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f 427 altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f 428 .popsection 429 430 .pushsection .altinstr_replacement,"ax" 431 143: 432 \newinstr1 433 144: 434 \newinstr2 435 145: 436 .popsection 437 .endm 438 439 .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3 440 140: 441 \oldinstr 442 141: 443 .skip -((alt_max_3(new_len1, new_len2, new_len3) - (old_len)) > 0) * \ 444 (alt_max_3(new_len1, new_len2, new_len3) - (old_len)),0x90 445 142: 446 447 .pushsection .altinstructions,"a" 448 altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f 449 altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f 450 altinstr_entry 140b,145f,\ft_flags3,142b-140b,146f-145f 451 .popsection 452 453 .pushsection .altinstr_replacement,"ax" 454 143: 455 \newinstr1 456 144: 457 \newinstr2 458 145: 459 \newinstr3 460 146: 461 .popsection 462 .endm 463 464 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 465 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \ 466 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 467 newinstr_yes, ft_flags 468 469 #endif /* __ASSEMBLY__ */ 470 471 #endif /* _ASM_X86_ALTERNATIVE_H */ 472