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 ALTINSTR_FLAG_INV (1 << 15) 10 #define ALT_NOT(feat) ((feat) | ALTINSTR_FLAG_INV) 11 12 #ifndef __ASSEMBLY__ 13 14 #include <linux/stddef.h> 15 16 /* 17 * Alternative inline assembly for SMP. 18 * 19 * The LOCK_PREFIX macro defined here replaces the LOCK and 20 * LOCK_PREFIX macros used everywhere in the source tree. 21 * 22 * SMP alternatives use the same data structures as the other 23 * alternatives and the X86_FEATURE_UP flag to indicate the case of a 24 * UP system running a SMP kernel. The existing apply_alternatives() 25 * works fine for patching a SMP kernel for UP. 26 * 27 * The SMP alternative tables can be kept after boot and contain both 28 * UP and SMP versions of the instructions to allow switching back to 29 * SMP at runtime, when hotplugging in a new CPU, which is especially 30 * useful in virtualized environments. 31 * 32 * The very common lock prefix is handled as special case in a 33 * separate table which is a pure address list without replacement ptr 34 * and size information. That keeps the table sizes small. 35 */ 36 37 #ifdef CONFIG_SMP 38 #define LOCK_PREFIX_HERE \ 39 ".pushsection .smp_locks,\"a\"\n" \ 40 ".balign 4\n" \ 41 ".long 671f - .\n" /* offset */ \ 42 ".popsection\n" \ 43 "671:" 44 45 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; " 46 47 #else /* ! CONFIG_SMP */ 48 #define LOCK_PREFIX_HERE "" 49 #define LOCK_PREFIX "" 50 #endif 51 52 /* 53 * objtool annotation to ignore the alternatives and only consider the original 54 * instruction(s). 55 */ 56 #define ANNOTATE_IGNORE_ALTERNATIVE \ 57 "999:\n\t" \ 58 ".pushsection .discard.ignore_alts\n\t" \ 59 ".long 999b - .\n\t" \ 60 ".popsection\n\t" 61 62 struct alt_instr { 63 s32 instr_offset; /* original instruction */ 64 s32 repl_offset; /* offset to replacement instruction */ 65 u16 cpuid; /* cpuid bit set for replacement */ 66 u8 instrlen; /* length of original instruction */ 67 u8 replacementlen; /* length of new instruction */ 68 } __packed; 69 70 /* 71 * Debug flag that can be tested to see whether alternative 72 * instructions were patched in already: 73 */ 74 extern int alternatives_patched; 75 76 extern void alternative_instructions(void); 77 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end); 78 extern void apply_retpolines(s32 *start, s32 *end); 79 extern void apply_returns(s32 *start, s32 *end); 80 extern void apply_ibt_endbr(s32 *start, s32 *end); 81 82 struct module; 83 struct paravirt_patch_site; 84 85 struct callthunk_sites { 86 s32 *call_start, *call_end; 87 struct paravirt_patch_site *pv_start, *pv_end; 88 }; 89 90 #ifdef CONFIG_CALL_THUNKS 91 extern void callthunks_patch_builtin_calls(void); 92 extern void callthunks_patch_module_calls(struct callthunk_sites *sites, 93 struct module *mod); 94 extern void *callthunks_translate_call_dest(void *dest); 95 extern bool is_callthunk(void *addr); 96 extern int x86_call_depth_emit_accounting(u8 **pprog, void *func); 97 #else 98 static __always_inline void callthunks_patch_builtin_calls(void) {} 99 static __always_inline void 100 callthunks_patch_module_calls(struct callthunk_sites *sites, 101 struct module *mod) {} 102 static __always_inline void *callthunks_translate_call_dest(void *dest) 103 { 104 return dest; 105 } 106 static __always_inline bool is_callthunk(void *addr) 107 { 108 return false; 109 } 110 static __always_inline int x86_call_depth_emit_accounting(u8 **pprog, 111 void *func) 112 { 113 return 0; 114 } 115 #endif 116 117 #ifdef CONFIG_SMP 118 extern void alternatives_smp_module_add(struct module *mod, char *name, 119 void *locks, void *locks_end, 120 void *text, void *text_end); 121 extern void alternatives_smp_module_del(struct module *mod); 122 extern void alternatives_enable_smp(void); 123 extern int alternatives_text_reserved(void *start, void *end); 124 extern bool skip_smp_alternatives; 125 #else 126 static inline void alternatives_smp_module_add(struct module *mod, char *name, 127 void *locks, void *locks_end, 128 void *text, void *text_end) {} 129 static inline void alternatives_smp_module_del(struct module *mod) {} 130 static inline void alternatives_enable_smp(void) {} 131 static inline int alternatives_text_reserved(void *start, void *end) 132 { 133 return 0; 134 } 135 #endif /* CONFIG_SMP */ 136 137 #define b_replacement(num) "664"#num 138 #define e_replacement(num) "665"#num 139 140 #define alt_end_marker "663" 141 #define alt_slen "662b-661b" 142 #define alt_total_slen alt_end_marker"b-661b" 143 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" 144 145 #define OLDINSTR(oldinstr, num) \ 146 "# ALT: oldnstr\n" \ 147 "661:\n\t" oldinstr "\n662:\n" \ 148 "# ALT: padding\n" \ 149 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ 150 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \ 151 alt_end_marker ":\n" 152 153 /* 154 * gas compatible max based on the idea from: 155 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 156 * 157 * The additional "-" is needed because gas uses a "true" value of -1. 158 */ 159 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))" 160 161 /* 162 * Pad the second replacement alternative with additional NOPs if it is 163 * additionally longer than the first replacement alternative. 164 */ 165 #define OLDINSTR_2(oldinstr, num1, num2) \ 166 "# ALT: oldinstr2\n" \ 167 "661:\n\t" oldinstr "\n662:\n" \ 168 "# ALT: padding2\n" \ 169 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ 170 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ 171 alt_end_marker ":\n" 172 173 #define OLDINSTR_3(oldinsn, n1, n2, n3) \ 174 "# ALT: oldinstr3\n" \ 175 "661:\n\t" oldinsn "\n662:\n" \ 176 "# ALT: padding3\n" \ 177 ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 178 " - (" alt_slen ")) > 0) * " \ 179 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 180 " - (" alt_slen ")), 0x90\n" \ 181 alt_end_marker ":\n" 182 183 #define ALTINSTR_ENTRY(feature, num) \ 184 " .long 661b - .\n" /* label */ \ 185 " .long " b_replacement(num)"f - .\n" /* new instruction */ \ 186 " .word " __stringify(feature) "\n" /* feature bit */ \ 187 " .byte " alt_total_slen "\n" /* source len */ \ 188 " .byte " alt_rlen(num) "\n" /* replacement len */ 189 190 #define ALTINSTR_REPLACEMENT(newinstr, num) /* replacement */ \ 191 "# ALT: replacement " #num "\n" \ 192 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n" 193 194 /* alternative assembly primitive: */ 195 #define ALTERNATIVE(oldinstr, newinstr, feature) \ 196 OLDINSTR(oldinstr, 1) \ 197 ".pushsection .altinstructions,\"a\"\n" \ 198 ALTINSTR_ENTRY(feature, 1) \ 199 ".popsection\n" \ 200 ".pushsection .altinstr_replacement, \"ax\"\n" \ 201 ALTINSTR_REPLACEMENT(newinstr, 1) \ 202 ".popsection\n" 203 204 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ 205 OLDINSTR_2(oldinstr, 1, 2) \ 206 ".pushsection .altinstructions,\"a\"\n" \ 207 ALTINSTR_ENTRY(feature1, 1) \ 208 ALTINSTR_ENTRY(feature2, 2) \ 209 ".popsection\n" \ 210 ".pushsection .altinstr_replacement, \"ax\"\n" \ 211 ALTINSTR_REPLACEMENT(newinstr1, 1) \ 212 ALTINSTR_REPLACEMENT(newinstr2, 2) \ 213 ".popsection\n" 214 215 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 216 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \ 217 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 218 newinstr_yes, feature) 219 220 #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \ 221 OLDINSTR_3(oldinsn, 1, 2, 3) \ 222 ".pushsection .altinstructions,\"a\"\n" \ 223 ALTINSTR_ENTRY(feat1, 1) \ 224 ALTINSTR_ENTRY(feat2, 2) \ 225 ALTINSTR_ENTRY(feat3, 3) \ 226 ".popsection\n" \ 227 ".pushsection .altinstr_replacement, \"ax\"\n" \ 228 ALTINSTR_REPLACEMENT(newinsn1, 1) \ 229 ALTINSTR_REPLACEMENT(newinsn2, 2) \ 230 ALTINSTR_REPLACEMENT(newinsn3, 3) \ 231 ".popsection\n" 232 233 /* 234 * Alternative instructions for different CPU types or capabilities. 235 * 236 * This allows to use optimized instructions even on generic binary 237 * kernels. 238 * 239 * length of oldinstr must be longer or equal the length of newinstr 240 * It can be padded with nops as needed. 241 * 242 * For non barrier like inlines please define new variants 243 * without volatile and memory clobber. 244 */ 245 #define alternative(oldinstr, newinstr, feature) \ 246 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") 247 248 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ 249 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") 250 251 #define alternative_ternary(oldinstr, feature, newinstr_yes, newinstr_no) \ 252 asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) ::: "memory") 253 254 /* 255 * Alternative inline assembly with input. 256 * 257 * Peculiarities: 258 * No memory clobber here. 259 * Argument numbers start with 1. 260 * Leaving an unused argument 0 to keep API compatibility. 261 */ 262 #define alternative_input(oldinstr, newinstr, feature, input...) \ 263 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 264 : : "i" (0), ## input) 265 266 /* 267 * This is similar to alternative_input. But it has two features and 268 * respective instructions. 269 * 270 * If CPU has feature2, newinstr2 is used. 271 * Otherwise, if CPU has feature1, newinstr1 is used. 272 * Otherwise, oldinstr is used. 273 */ 274 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \ 275 feature2, input...) \ 276 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \ 277 newinstr2, feature2) \ 278 : : "i" (0), ## input) 279 280 /* Like alternative_input, but with a single output argument */ 281 #define alternative_io(oldinstr, newinstr, feature, output, input...) \ 282 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 283 : output : "i" (0), ## input) 284 285 /* Like alternative_io, but for replacing a direct call with another one. */ 286 #define alternative_call(oldfunc, newfunc, feature, output, input...) \ 287 asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ 288 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) 289 290 /* 291 * Like alternative_call, but there are two features and respective functions. 292 * If CPU has feature2, function2 is used. 293 * Otherwise, if CPU has feature1, function1 is used. 294 * Otherwise, old function is used. 295 */ 296 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ 297 output, input...) \ 298 asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ 299 "call %P[new2]", feature2) \ 300 : output, ASM_CALL_CONSTRAINT \ 301 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 302 [new2] "i" (newfunc2), ## input) 303 304 /* 305 * use this macro(s) if you need more than one output parameter 306 * in alternative_io 307 */ 308 #define ASM_OUTPUT2(a...) a 309 310 /* 311 * use this macro if you need clobbers but no inputs in 312 * alternative_{input,io,call}() 313 */ 314 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr 315 316 #else /* __ASSEMBLY__ */ 317 318 #ifdef CONFIG_SMP 319 .macro LOCK_PREFIX 320 672: lock 321 .pushsection .smp_locks,"a" 322 .balign 4 323 .long 672b - . 324 .popsection 325 .endm 326 #else 327 .macro LOCK_PREFIX 328 .endm 329 #endif 330 331 /* 332 * objtool annotation to ignore the alternatives and only consider the original 333 * instruction(s). 334 */ 335 .macro ANNOTATE_IGNORE_ALTERNATIVE 336 .Lannotate_\@: 337 .pushsection .discard.ignore_alts 338 .long .Lannotate_\@ - . 339 .popsection 340 .endm 341 342 /* 343 * Issue one struct alt_instr descriptor entry (need to put it into 344 * the section .altinstructions, see below). This entry contains 345 * enough information for the alternatives patching code to patch an 346 * instruction. See apply_alternatives(). 347 */ 348 .macro altinstruction_entry orig alt feature orig_len alt_len 349 .long \orig - . 350 .long \alt - . 351 .word \feature 352 .byte \orig_len 353 .byte \alt_len 354 .endm 355 356 /* 357 * Define an alternative between two instructions. If @feature is 358 * present, early code in apply_alternatives() replaces @oldinstr with 359 * @newinstr. ".skip" directive takes care of proper instruction padding 360 * in case @newinstr is longer than @oldinstr. 361 */ 362 .macro ALTERNATIVE oldinstr, newinstr, feature 363 140: 364 \oldinstr 365 141: 366 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90 367 142: 368 369 .pushsection .altinstructions,"a" 370 altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f 371 .popsection 372 373 .pushsection .altinstr_replacement,"ax" 374 143: 375 \newinstr 376 144: 377 .popsection 378 .endm 379 380 #define old_len 141b-140b 381 #define new_len1 144f-143f 382 #define new_len2 145f-144f 383 #define new_len3 146f-145f 384 385 /* 386 * gas compatible max based on the idea from: 387 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 388 * 389 * The additional "-" is needed because gas uses a "true" value of -1. 390 */ 391 #define alt_max_2(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b))))) 392 #define alt_max_3(a, b, c) (alt_max_2(alt_max_2(a, b), c)) 393 394 395 /* 396 * Same as ALTERNATIVE macro above but for two alternatives. If CPU 397 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has 398 * @feature2, it replaces @oldinstr with @feature2. 399 */ 400 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2 401 140: 402 \oldinstr 403 141: 404 .skip -((alt_max_2(new_len1, new_len2) - (old_len)) > 0) * \ 405 (alt_max_2(new_len1, new_len2) - (old_len)),0x90 406 142: 407 408 .pushsection .altinstructions,"a" 409 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f 410 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f 411 .popsection 412 413 .pushsection .altinstr_replacement,"ax" 414 143: 415 \newinstr1 416 144: 417 \newinstr2 418 145: 419 .popsection 420 .endm 421 422 .macro ALTERNATIVE_3 oldinstr, newinstr1, feature1, newinstr2, feature2, newinstr3, feature3 423 140: 424 \oldinstr 425 141: 426 .skip -((alt_max_3(new_len1, new_len2, new_len3) - (old_len)) > 0) * \ 427 (alt_max_3(new_len1, new_len2, new_len3) - (old_len)),0x90 428 142: 429 430 .pushsection .altinstructions,"a" 431 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f 432 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f 433 altinstruction_entry 140b,145f,\feature3,142b-140b,146f-145f 434 .popsection 435 436 .pushsection .altinstr_replacement,"ax" 437 143: 438 \newinstr1 439 144: 440 \newinstr2 441 145: 442 \newinstr3 443 146: 444 .popsection 445 .endm 446 447 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 448 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \ 449 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 450 newinstr_yes, feature 451 452 #endif /* __ASSEMBLY__ */ 453 454 #endif /* _ASM_X86_ALTERNATIVE_H */ 455