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 84 #ifdef CONFIG_SMP 85 extern void alternatives_smp_module_add(struct module *mod, char *name, 86 void *locks, void *locks_end, 87 void *text, void *text_end); 88 extern void alternatives_smp_module_del(struct module *mod); 89 extern void alternatives_enable_smp(void); 90 extern int alternatives_text_reserved(void *start, void *end); 91 extern bool skip_smp_alternatives; 92 #else 93 static inline void alternatives_smp_module_add(struct module *mod, char *name, 94 void *locks, void *locks_end, 95 void *text, void *text_end) {} 96 static inline void alternatives_smp_module_del(struct module *mod) {} 97 static inline void alternatives_enable_smp(void) {} 98 static inline int alternatives_text_reserved(void *start, void *end) 99 { 100 return 0; 101 } 102 #endif /* CONFIG_SMP */ 103 104 #define b_replacement(num) "664"#num 105 #define e_replacement(num) "665"#num 106 107 #define alt_end_marker "663" 108 #define alt_slen "662b-661b" 109 #define alt_total_slen alt_end_marker"b-661b" 110 #define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" 111 112 #define OLDINSTR(oldinstr, num) \ 113 "# ALT: oldnstr\n" \ 114 "661:\n\t" oldinstr "\n662:\n" \ 115 "# ALT: padding\n" \ 116 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ 117 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \ 118 alt_end_marker ":\n" 119 120 /* 121 * gas compatible max based on the idea from: 122 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 123 * 124 * The additional "-" is needed because gas uses a "true" value of -1. 125 */ 126 #define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))" 127 128 /* 129 * Pad the second replacement alternative with additional NOPs if it is 130 * additionally longer than the first replacement alternative. 131 */ 132 #define OLDINSTR_2(oldinstr, num1, num2) \ 133 "# ALT: oldinstr2\n" \ 134 "661:\n\t" oldinstr "\n662:\n" \ 135 "# ALT: padding2\n" \ 136 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ 137 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ 138 alt_end_marker ":\n" 139 140 #define OLDINSTR_3(oldinsn, n1, n2, n3) \ 141 "# ALT: oldinstr3\n" \ 142 "661:\n\t" oldinsn "\n662:\n" \ 143 "# ALT: padding3\n" \ 144 ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 145 " - (" alt_slen ")) > 0) * " \ 146 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 147 " - (" alt_slen ")), 0x90\n" \ 148 alt_end_marker ":\n" 149 150 #define ALTINSTR_ENTRY(feature, num) \ 151 " .long 661b - .\n" /* label */ \ 152 " .long " b_replacement(num)"f - .\n" /* new instruction */ \ 153 " .word " __stringify(feature) "\n" /* feature bit */ \ 154 " .byte " alt_total_slen "\n" /* source len */ \ 155 " .byte " alt_rlen(num) "\n" /* replacement len */ 156 157 #define ALTINSTR_REPLACEMENT(newinstr, num) /* replacement */ \ 158 "# ALT: replacement " #num "\n" \ 159 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n" 160 161 /* alternative assembly primitive: */ 162 #define ALTERNATIVE(oldinstr, newinstr, feature) \ 163 OLDINSTR(oldinstr, 1) \ 164 ".pushsection .altinstructions,\"a\"\n" \ 165 ALTINSTR_ENTRY(feature, 1) \ 166 ".popsection\n" \ 167 ".pushsection .altinstr_replacement, \"ax\"\n" \ 168 ALTINSTR_REPLACEMENT(newinstr, 1) \ 169 ".popsection\n" 170 171 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ 172 OLDINSTR_2(oldinstr, 1, 2) \ 173 ".pushsection .altinstructions,\"a\"\n" \ 174 ALTINSTR_ENTRY(feature1, 1) \ 175 ALTINSTR_ENTRY(feature2, 2) \ 176 ".popsection\n" \ 177 ".pushsection .altinstr_replacement, \"ax\"\n" \ 178 ALTINSTR_REPLACEMENT(newinstr1, 1) \ 179 ALTINSTR_REPLACEMENT(newinstr2, 2) \ 180 ".popsection\n" 181 182 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 183 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \ 184 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 185 newinstr_yes, feature) 186 187 #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \ 188 OLDINSTR_3(oldinsn, 1, 2, 3) \ 189 ".pushsection .altinstructions,\"a\"\n" \ 190 ALTINSTR_ENTRY(feat1, 1) \ 191 ALTINSTR_ENTRY(feat2, 2) \ 192 ALTINSTR_ENTRY(feat3, 3) \ 193 ".popsection\n" \ 194 ".pushsection .altinstr_replacement, \"ax\"\n" \ 195 ALTINSTR_REPLACEMENT(newinsn1, 1) \ 196 ALTINSTR_REPLACEMENT(newinsn2, 2) \ 197 ALTINSTR_REPLACEMENT(newinsn3, 3) \ 198 ".popsection\n" 199 200 /* 201 * Alternative instructions for different CPU types or capabilities. 202 * 203 * This allows to use optimized instructions even on generic binary 204 * kernels. 205 * 206 * length of oldinstr must be longer or equal the length of newinstr 207 * It can be padded with nops as needed. 208 * 209 * For non barrier like inlines please define new variants 210 * without volatile and memory clobber. 211 */ 212 #define alternative(oldinstr, newinstr, feature) \ 213 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") 214 215 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ 216 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") 217 218 #define alternative_ternary(oldinstr, feature, newinstr_yes, newinstr_no) \ 219 asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) ::: "memory") 220 221 /* 222 * Alternative inline assembly with input. 223 * 224 * Peculiarities: 225 * No memory clobber here. 226 * Argument numbers start with 1. 227 * Leaving an unused argument 0 to keep API compatibility. 228 */ 229 #define alternative_input(oldinstr, newinstr, feature, input...) \ 230 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 231 : : "i" (0), ## input) 232 233 /* 234 * This is similar to alternative_input. But it has two features and 235 * respective instructions. 236 * 237 * If CPU has feature2, newinstr2 is used. 238 * Otherwise, if CPU has feature1, newinstr1 is used. 239 * Otherwise, oldinstr is used. 240 */ 241 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \ 242 feature2, input...) \ 243 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \ 244 newinstr2, feature2) \ 245 : : "i" (0), ## input) 246 247 /* Like alternative_input, but with a single output argument */ 248 #define alternative_io(oldinstr, newinstr, feature, output, input...) \ 249 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 250 : output : "i" (0), ## input) 251 252 /* Like alternative_io, but for replacing a direct call with another one. */ 253 #define alternative_call(oldfunc, newfunc, feature, output, input...) \ 254 asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ 255 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) 256 257 /* 258 * Like alternative_call, but there are two features and respective functions. 259 * If CPU has feature2, function2 is used. 260 * Otherwise, if CPU has feature1, function1 is used. 261 * Otherwise, old function is used. 262 */ 263 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ 264 output, input...) \ 265 asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ 266 "call %P[new2]", feature2) \ 267 : output, ASM_CALL_CONSTRAINT \ 268 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 269 [new2] "i" (newfunc2), ## input) 270 271 /* 272 * use this macro(s) if you need more than one output parameter 273 * in alternative_io 274 */ 275 #define ASM_OUTPUT2(a...) a 276 277 /* 278 * use this macro if you need clobbers but no inputs in 279 * alternative_{input,io,call}() 280 */ 281 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr 282 283 #else /* __ASSEMBLY__ */ 284 285 #ifdef CONFIG_SMP 286 .macro LOCK_PREFIX 287 672: lock 288 .pushsection .smp_locks,"a" 289 .balign 4 290 .long 672b - . 291 .popsection 292 .endm 293 #else 294 .macro LOCK_PREFIX 295 .endm 296 #endif 297 298 /* 299 * objtool annotation to ignore the alternatives and only consider the original 300 * instruction(s). 301 */ 302 .macro ANNOTATE_IGNORE_ALTERNATIVE 303 .Lannotate_\@: 304 .pushsection .discard.ignore_alts 305 .long .Lannotate_\@ - . 306 .popsection 307 .endm 308 309 /* 310 * Issue one struct alt_instr descriptor entry (need to put it into 311 * the section .altinstructions, see below). This entry contains 312 * enough information for the alternatives patching code to patch an 313 * instruction. See apply_alternatives(). 314 */ 315 .macro altinstruction_entry orig alt feature orig_len alt_len 316 .long \orig - . 317 .long \alt - . 318 .word \feature 319 .byte \orig_len 320 .byte \alt_len 321 .endm 322 323 /* 324 * Define an alternative between two instructions. If @feature is 325 * present, early code in apply_alternatives() replaces @oldinstr with 326 * @newinstr. ".skip" directive takes care of proper instruction padding 327 * in case @newinstr is longer than @oldinstr. 328 */ 329 .macro ALTERNATIVE oldinstr, newinstr, feature 330 140: 331 \oldinstr 332 141: 333 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90 334 142: 335 336 .pushsection .altinstructions,"a" 337 altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f 338 .popsection 339 340 .pushsection .altinstr_replacement,"ax" 341 143: 342 \newinstr 343 144: 344 .popsection 345 .endm 346 347 #define old_len 141b-140b 348 #define new_len1 144f-143f 349 #define new_len2 145f-144f 350 351 /* 352 * gas compatible max based on the idea from: 353 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 354 * 355 * The additional "-" is needed because gas uses a "true" value of -1. 356 */ 357 #define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b))))) 358 359 360 /* 361 * Same as ALTERNATIVE macro above but for two alternatives. If CPU 362 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has 363 * @feature2, it replaces @oldinstr with @feature2. 364 */ 365 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2 366 140: 367 \oldinstr 368 141: 369 .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \ 370 (alt_max_short(new_len1, new_len2) - (old_len)),0x90 371 142: 372 373 .pushsection .altinstructions,"a" 374 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f 375 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f 376 .popsection 377 378 .pushsection .altinstr_replacement,"ax" 379 143: 380 \newinstr1 381 144: 382 \newinstr2 383 145: 384 .popsection 385 .endm 386 387 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 388 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \ 389 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 390 newinstr_yes, feature 391 392 #endif /* __ASSEMBLY__ */ 393 394 #endif /* _ASM_X86_ALTERNATIVE_H */ 395