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 79 struct module; 80 81 #ifdef CONFIG_SMP 82 extern void alternatives_smp_module_add(struct module *mod, char *name, 83 void *locks, void *locks_end, 84 void *text, void *text_end); 85 extern void alternatives_smp_module_del(struct module *mod); 86 extern void alternatives_enable_smp(void); 87 extern int alternatives_text_reserved(void *start, void *end); 88 extern bool skip_smp_alternatives; 89 #else 90 static inline void alternatives_smp_module_add(struct module *mod, char *name, 91 void *locks, void *locks_end, 92 void *text, void *text_end) {} 93 static inline void alternatives_smp_module_del(struct module *mod) {} 94 static inline void alternatives_enable_smp(void) {} 95 static inline int alternatives_text_reserved(void *start, void *end) 96 { 97 return 0; 98 } 99 #endif /* CONFIG_SMP */ 100 101 #define b_replacement(num) "664"#num 102 #define e_replacement(num) "665"#num 103 104 #define alt_end_marker "663" 105 #define alt_slen "662b-661b" 106 #define alt_total_slen alt_end_marker"b-661b" 107 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" 108 109 #define OLDINSTR(oldinstr, num) \ 110 "# ALT: oldnstr\n" \ 111 "661:\n\t" oldinstr "\n662:\n" \ 112 "# ALT: padding\n" \ 113 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ 114 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \ 115 alt_end_marker ":\n" 116 117 /* 118 * gas compatible max based on the idea from: 119 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 120 * 121 * The additional "-" is needed because gas uses a "true" value of -1. 122 */ 123 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))" 124 125 /* 126 * Pad the second replacement alternative with additional NOPs if it is 127 * additionally longer than the first replacement alternative. 128 */ 129 #define OLDINSTR_2(oldinstr, num1, num2) \ 130 "# ALT: oldinstr2\n" \ 131 "661:\n\t" oldinstr "\n662:\n" \ 132 "# ALT: padding2\n" \ 133 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ 134 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ 135 alt_end_marker ":\n" 136 137 #define OLDINSTR_3(oldinsn, n1, n2, n3) \ 138 "# ALT: oldinstr3\n" \ 139 "661:\n\t" oldinsn "\n662:\n" \ 140 "# ALT: padding3\n" \ 141 ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 142 " - (" alt_slen ")) > 0) * " \ 143 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 144 " - (" alt_slen ")), 0x90\n" \ 145 alt_end_marker ":\n" 146 147 #define ALTINSTR_ENTRY(feature, num) \ 148 " .long 661b - .\n" /* label */ \ 149 " .long " b_replacement(num)"f - .\n" /* new instruction */ \ 150 " .word " __stringify(feature) "\n" /* feature bit */ \ 151 " .byte " alt_total_slen "\n" /* source len */ \ 152 " .byte " alt_rlen(num) "\n" /* replacement len */ 153 154 #define ALTINSTR_REPLACEMENT(newinstr, num) /* replacement */ \ 155 "# ALT: replacement " #num "\n" \ 156 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n" 157 158 /* alternative assembly primitive: */ 159 #define ALTERNATIVE(oldinstr, newinstr, feature) \ 160 OLDINSTR(oldinstr, 1) \ 161 ".pushsection .altinstructions,\"a\"\n" \ 162 ALTINSTR_ENTRY(feature, 1) \ 163 ".popsection\n" \ 164 ".pushsection .altinstr_replacement, \"ax\"\n" \ 165 ALTINSTR_REPLACEMENT(newinstr, 1) \ 166 ".popsection\n" 167 168 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ 169 OLDINSTR_2(oldinstr, 1, 2) \ 170 ".pushsection .altinstructions,\"a\"\n" \ 171 ALTINSTR_ENTRY(feature1, 1) \ 172 ALTINSTR_ENTRY(feature2, 2) \ 173 ".popsection\n" \ 174 ".pushsection .altinstr_replacement, \"ax\"\n" \ 175 ALTINSTR_REPLACEMENT(newinstr1, 1) \ 176 ALTINSTR_REPLACEMENT(newinstr2, 2) \ 177 ".popsection\n" 178 179 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 180 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \ 181 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 182 newinstr_yes, feature) 183 184 #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \ 185 OLDINSTR_3(oldinsn, 1, 2, 3) \ 186 ".pushsection .altinstructions,\"a\"\n" \ 187 ALTINSTR_ENTRY(feat1, 1) \ 188 ALTINSTR_ENTRY(feat2, 2) \ 189 ALTINSTR_ENTRY(feat3, 3) \ 190 ".popsection\n" \ 191 ".pushsection .altinstr_replacement, \"ax\"\n" \ 192 ALTINSTR_REPLACEMENT(newinsn1, 1) \ 193 ALTINSTR_REPLACEMENT(newinsn2, 2) \ 194 ALTINSTR_REPLACEMENT(newinsn3, 3) \ 195 ".popsection\n" 196 197 /* 198 * Alternative instructions for different CPU types or capabilities. 199 * 200 * This allows to use optimized instructions even on generic binary 201 * kernels. 202 * 203 * length of oldinstr must be longer or equal the length of newinstr 204 * It can be padded with nops as needed. 205 * 206 * For non barrier like inlines please define new variants 207 * without volatile and memory clobber. 208 */ 209 #define alternative(oldinstr, newinstr, feature) \ 210 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") 211 212 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ 213 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") 214 215 #define alternative_ternary(oldinstr, feature, newinstr_yes, newinstr_no) \ 216 asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) ::: "memory") 217 218 /* 219 * Alternative inline assembly with input. 220 * 221 * Peculiarities: 222 * No memory clobber here. 223 * Argument numbers start with 1. 224 * Leaving an unused argument 0 to keep API compatibility. 225 */ 226 #define alternative_input(oldinstr, newinstr, feature, input...) \ 227 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 228 : : "i" (0), ## input) 229 230 /* 231 * This is similar to alternative_input. But it has two features and 232 * respective instructions. 233 * 234 * If CPU has feature2, newinstr2 is used. 235 * Otherwise, if CPU has feature1, newinstr1 is used. 236 * Otherwise, oldinstr is used. 237 */ 238 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \ 239 feature2, input...) \ 240 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \ 241 newinstr2, feature2) \ 242 : : "i" (0), ## input) 243 244 /* Like alternative_input, but with a single output argument */ 245 #define alternative_io(oldinstr, newinstr, feature, output, input...) \ 246 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 247 : output : "i" (0), ## input) 248 249 /* Like alternative_io, but for replacing a direct call with another one. */ 250 #define alternative_call(oldfunc, newfunc, feature, output, input...) \ 251 asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ 252 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) 253 254 /* 255 * Like alternative_call, but there are two features and respective functions. 256 * If CPU has feature2, function2 is used. 257 * Otherwise, if CPU has feature1, function1 is used. 258 * Otherwise, old function is used. 259 */ 260 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ 261 output, input...) \ 262 asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ 263 "call %P[new2]", feature2) \ 264 : output, ASM_CALL_CONSTRAINT \ 265 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 266 [new2] "i" (newfunc2), ## input) 267 268 /* 269 * use this macro(s) if you need more than one output parameter 270 * in alternative_io 271 */ 272 #define ASM_OUTPUT2(a...) a 273 274 /* 275 * use this macro if you need clobbers but no inputs in 276 * alternative_{input,io,call}() 277 */ 278 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr 279 280 #else /* __ASSEMBLY__ */ 281 282 #ifdef CONFIG_SMP 283 .macro LOCK_PREFIX 284 672: lock 285 .pushsection .smp_locks,"a" 286 .balign 4 287 .long 672b - . 288 .popsection 289 .endm 290 #else 291 .macro LOCK_PREFIX 292 .endm 293 #endif 294 295 /* 296 * objtool annotation to ignore the alternatives and only consider the original 297 * instruction(s). 298 */ 299 .macro ANNOTATE_IGNORE_ALTERNATIVE 300 .Lannotate_\@: 301 .pushsection .discard.ignore_alts 302 .long .Lannotate_\@ - . 303 .popsection 304 .endm 305 306 /* 307 * Issue one struct alt_instr descriptor entry (need to put it into 308 * the section .altinstructions, see below). This entry contains 309 * enough information for the alternatives patching code to patch an 310 * instruction. See apply_alternatives(). 311 */ 312 .macro altinstruction_entry orig alt feature orig_len alt_len 313 .long \orig - . 314 .long \alt - . 315 .word \feature 316 .byte \orig_len 317 .byte \alt_len 318 .endm 319 320 /* 321 * Define an alternative between two instructions. If @feature is 322 * present, early code in apply_alternatives() replaces @oldinstr with 323 * @newinstr. ".skip" directive takes care of proper instruction padding 324 * in case @newinstr is longer than @oldinstr. 325 */ 326 .macro ALTERNATIVE oldinstr, newinstr, feature 327 140: 328 \oldinstr 329 141: 330 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90 331 142: 332 333 .pushsection .altinstructions,"a" 334 altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f 335 .popsection 336 337 .pushsection .altinstr_replacement,"ax" 338 143: 339 \newinstr 340 144: 341 .popsection 342 .endm 343 344 #define old_len 141b-140b 345 #define new_len1 144f-143f 346 #define new_len2 145f-144f 347 348 /* 349 * gas compatible max based on the idea from: 350 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 351 * 352 * The additional "-" is needed because gas uses a "true" value of -1. 353 */ 354 #define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b))))) 355 356 357 /* 358 * Same as ALTERNATIVE macro above but for two alternatives. If CPU 359 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has 360 * @feature2, it replaces @oldinstr with @feature2. 361 */ 362 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2 363 140: 364 \oldinstr 365 141: 366 .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \ 367 (alt_max_short(new_len1, new_len2) - (old_len)),0x90 368 142: 369 370 .pushsection .altinstructions,"a" 371 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f 372 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f 373 .popsection 374 375 .pushsection .altinstr_replacement,"ax" 376 143: 377 \newinstr1 378 144: 379 \newinstr2 380 145: 381 .popsection 382 .endm 383 384 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 385 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \ 386 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 387 newinstr_yes, feature 388 389 #endif /* __ASSEMBLY__ */ 390 391 #endif /* _ASM_X86_ALTERNATIVE_H */ 392