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 80 struct module; 81 82 #ifdef CONFIG_SMP 83 extern void alternatives_smp_module_add(struct module *mod, char *name, 84 void *locks, void *locks_end, 85 void *text, void *text_end); 86 extern void alternatives_smp_module_del(struct module *mod); 87 extern void alternatives_enable_smp(void); 88 extern int alternatives_text_reserved(void *start, void *end); 89 extern bool skip_smp_alternatives; 90 #else 91 static inline void alternatives_smp_module_add(struct module *mod, char *name, 92 void *locks, void *locks_end, 93 void *text, void *text_end) {} 94 static inline void alternatives_smp_module_del(struct module *mod) {} 95 static inline void alternatives_enable_smp(void) {} 96 static inline int alternatives_text_reserved(void *start, void *end) 97 { 98 return 0; 99 } 100 #endif /* CONFIG_SMP */ 101 102 #define b_replacement(num) "664"#num 103 #define e_replacement(num) "665"#num 104 105 #define alt_end_marker "663" 106 #define alt_slen "662b-661b" 107 #define alt_total_slen alt_end_marker"b-661b" 108 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" 109 110 #define OLDINSTR(oldinstr, num) \ 111 "# ALT: oldnstr\n" \ 112 "661:\n\t" oldinstr "\n662:\n" \ 113 "# ALT: padding\n" \ 114 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ 115 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \ 116 alt_end_marker ":\n" 117 118 /* 119 * gas compatible max based on the idea from: 120 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 121 * 122 * The additional "-" is needed because gas uses a "true" value of -1. 123 */ 124 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))" 125 126 /* 127 * Pad the second replacement alternative with additional NOPs if it is 128 * additionally longer than the first replacement alternative. 129 */ 130 #define OLDINSTR_2(oldinstr, num1, num2) \ 131 "# ALT: oldinstr2\n" \ 132 "661:\n\t" oldinstr "\n662:\n" \ 133 "# ALT: padding2\n" \ 134 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ 135 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ 136 alt_end_marker ":\n" 137 138 #define OLDINSTR_3(oldinsn, n1, n2, n3) \ 139 "# ALT: oldinstr3\n" \ 140 "661:\n\t" oldinsn "\n662:\n" \ 141 "# ALT: padding3\n" \ 142 ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 143 " - (" alt_slen ")) > 0) * " \ 144 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 145 " - (" alt_slen ")), 0x90\n" \ 146 alt_end_marker ":\n" 147 148 #define ALTINSTR_ENTRY(feature, num) \ 149 " .long 661b - .\n" /* label */ \ 150 " .long " b_replacement(num)"f - .\n" /* new instruction */ \ 151 " .word " __stringify(feature) "\n" /* feature bit */ \ 152 " .byte " alt_total_slen "\n" /* source len */ \ 153 " .byte " alt_rlen(num) "\n" /* replacement len */ 154 155 #define ALTINSTR_REPLACEMENT(newinstr, num) /* replacement */ \ 156 "# ALT: replacement " #num "\n" \ 157 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n" 158 159 /* alternative assembly primitive: */ 160 #define ALTERNATIVE(oldinstr, newinstr, feature) \ 161 OLDINSTR(oldinstr, 1) \ 162 ".pushsection .altinstructions,\"a\"\n" \ 163 ALTINSTR_ENTRY(feature, 1) \ 164 ".popsection\n" \ 165 ".pushsection .altinstr_replacement, \"ax\"\n" \ 166 ALTINSTR_REPLACEMENT(newinstr, 1) \ 167 ".popsection\n" 168 169 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ 170 OLDINSTR_2(oldinstr, 1, 2) \ 171 ".pushsection .altinstructions,\"a\"\n" \ 172 ALTINSTR_ENTRY(feature1, 1) \ 173 ALTINSTR_ENTRY(feature2, 2) \ 174 ".popsection\n" \ 175 ".pushsection .altinstr_replacement, \"ax\"\n" \ 176 ALTINSTR_REPLACEMENT(newinstr1, 1) \ 177 ALTINSTR_REPLACEMENT(newinstr2, 2) \ 178 ".popsection\n" 179 180 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 181 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \ 182 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 183 newinstr_yes, feature) 184 185 #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \ 186 OLDINSTR_3(oldinsn, 1, 2, 3) \ 187 ".pushsection .altinstructions,\"a\"\n" \ 188 ALTINSTR_ENTRY(feat1, 1) \ 189 ALTINSTR_ENTRY(feat2, 2) \ 190 ALTINSTR_ENTRY(feat3, 3) \ 191 ".popsection\n" \ 192 ".pushsection .altinstr_replacement, \"ax\"\n" \ 193 ALTINSTR_REPLACEMENT(newinsn1, 1) \ 194 ALTINSTR_REPLACEMENT(newinsn2, 2) \ 195 ALTINSTR_REPLACEMENT(newinsn3, 3) \ 196 ".popsection\n" 197 198 /* 199 * Alternative instructions for different CPU types or capabilities. 200 * 201 * This allows to use optimized instructions even on generic binary 202 * kernels. 203 * 204 * length of oldinstr must be longer or equal the length of newinstr 205 * It can be padded with nops as needed. 206 * 207 * For non barrier like inlines please define new variants 208 * without volatile and memory clobber. 209 */ 210 #define alternative(oldinstr, newinstr, feature) \ 211 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") 212 213 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ 214 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") 215 216 #define alternative_ternary(oldinstr, feature, newinstr_yes, newinstr_no) \ 217 asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) ::: "memory") 218 219 /* 220 * Alternative inline assembly with input. 221 * 222 * Peculiarities: 223 * No memory clobber here. 224 * Argument numbers start with 1. 225 * Leaving an unused argument 0 to keep API compatibility. 226 */ 227 #define alternative_input(oldinstr, newinstr, feature, input...) \ 228 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 229 : : "i" (0), ## input) 230 231 /* 232 * This is similar to alternative_input. But it has two features and 233 * respective instructions. 234 * 235 * If CPU has feature2, newinstr2 is used. 236 * Otherwise, if CPU has feature1, newinstr1 is used. 237 * Otherwise, oldinstr is used. 238 */ 239 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \ 240 feature2, input...) \ 241 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \ 242 newinstr2, feature2) \ 243 : : "i" (0), ## input) 244 245 /* Like alternative_input, but with a single output argument */ 246 #define alternative_io(oldinstr, newinstr, feature, output, input...) \ 247 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 248 : output : "i" (0), ## input) 249 250 /* Like alternative_io, but for replacing a direct call with another one. */ 251 #define alternative_call(oldfunc, newfunc, feature, output, input...) \ 252 asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ 253 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) 254 255 /* 256 * Like alternative_call, but there are two features and respective functions. 257 * If CPU has feature2, function2 is used. 258 * Otherwise, if CPU has feature1, function1 is used. 259 * Otherwise, old function is used. 260 */ 261 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ 262 output, input...) \ 263 asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ 264 "call %P[new2]", feature2) \ 265 : output, ASM_CALL_CONSTRAINT \ 266 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 267 [new2] "i" (newfunc2), ## input) 268 269 /* 270 * use this macro(s) if you need more than one output parameter 271 * in alternative_io 272 */ 273 #define ASM_OUTPUT2(a...) a 274 275 /* 276 * use this macro if you need clobbers but no inputs in 277 * alternative_{input,io,call}() 278 */ 279 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr 280 281 #else /* __ASSEMBLY__ */ 282 283 #ifdef CONFIG_SMP 284 .macro LOCK_PREFIX 285 672: lock 286 .pushsection .smp_locks,"a" 287 .balign 4 288 .long 672b - . 289 .popsection 290 .endm 291 #else 292 .macro LOCK_PREFIX 293 .endm 294 #endif 295 296 /* 297 * objtool annotation to ignore the alternatives and only consider the original 298 * instruction(s). 299 */ 300 .macro ANNOTATE_IGNORE_ALTERNATIVE 301 .Lannotate_\@: 302 .pushsection .discard.ignore_alts 303 .long .Lannotate_\@ - . 304 .popsection 305 .endm 306 307 /* 308 * Issue one struct alt_instr descriptor entry (need to put it into 309 * the section .altinstructions, see below). This entry contains 310 * enough information for the alternatives patching code to patch an 311 * instruction. See apply_alternatives(). 312 */ 313 .macro altinstruction_entry orig alt feature orig_len alt_len 314 .long \orig - . 315 .long \alt - . 316 .word \feature 317 .byte \orig_len 318 .byte \alt_len 319 .endm 320 321 /* 322 * Define an alternative between two instructions. If @feature is 323 * present, early code in apply_alternatives() replaces @oldinstr with 324 * @newinstr. ".skip" directive takes care of proper instruction padding 325 * in case @newinstr is longer than @oldinstr. 326 */ 327 .macro ALTERNATIVE oldinstr, newinstr, feature 328 140: 329 \oldinstr 330 141: 331 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90 332 142: 333 334 .pushsection .altinstructions,"a" 335 altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f 336 .popsection 337 338 .pushsection .altinstr_replacement,"ax" 339 143: 340 \newinstr 341 144: 342 .popsection 343 .endm 344 345 #define old_len 141b-140b 346 #define new_len1 144f-143f 347 #define new_len2 145f-144f 348 349 /* 350 * gas compatible max based on the idea from: 351 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 352 * 353 * The additional "-" is needed because gas uses a "true" value of -1. 354 */ 355 #define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b))))) 356 357 358 /* 359 * Same as ALTERNATIVE macro above but for two alternatives. If CPU 360 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has 361 * @feature2, it replaces @oldinstr with @feature2. 362 */ 363 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2 364 140: 365 \oldinstr 366 141: 367 .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \ 368 (alt_max_short(new_len1, new_len2) - (old_len)),0x90 369 142: 370 371 .pushsection .altinstructions,"a" 372 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f 373 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f 374 .popsection 375 376 .pushsection .altinstr_replacement,"ax" 377 143: 378 \newinstr1 379 144: 380 \newinstr2 381 145: 382 .popsection 383 .endm 384 385 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 386 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \ 387 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 388 newinstr_yes, feature 389 390 #endif /* __ASSEMBLY__ */ 391 392 #endif /* _ASM_X86_ALTERNATIVE_H */ 393