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 62struct 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 */ 74extern int alternatives_patched; 75 76extern void alternative_instructions(void); 77extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end); 78extern void apply_retpolines(s32 *start, s32 *end); 79extern void apply_returns(s32 *start, s32 *end); 80 81struct module; 82 83#ifdef CONFIG_SMP 84extern void alternatives_smp_module_add(struct module *mod, char *name, 85 void *locks, void *locks_end, 86 void *text, void *text_end); 87extern void alternatives_smp_module_del(struct module *mod); 88extern void alternatives_enable_smp(void); 89extern int alternatives_text_reserved(void *start, void *end); 90extern bool skip_smp_alternatives; 91#else 92static inline void alternatives_smp_module_add(struct module *mod, char *name, 93 void *locks, void *locks_end, 94 void *text, void *text_end) {} 95static inline void alternatives_smp_module_del(struct module *mod) {} 96static inline void alternatives_enable_smp(void) {} 97static inline int alternatives_text_reserved(void *start, void *end) 98{ 99 return 0; 100} 101#endif /* CONFIG_SMP */ 102 103#define b_replacement(num) "664"#num 104#define e_replacement(num) "665"#num 105 106#define alt_end_marker "663" 107#define alt_slen "662b-661b" 108#define alt_total_slen alt_end_marker"b-661b" 109#define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f" 110 111#define OLDINSTR(oldinstr, num) \ 112 "# ALT: oldnstr\n" \ 113 "661:\n\t" oldinstr "\n662:\n" \ 114 "# ALT: padding\n" \ 115 ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \ 116 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \ 117 alt_end_marker ":\n" 118 119/* 120 * gas compatible max based on the idea from: 121 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 122 * 123 * The additional "-" is needed because gas uses a "true" value of -1. 124 */ 125#define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))" 126 127/* 128 * Pad the second replacement alternative with additional NOPs if it is 129 * additionally longer than the first replacement alternative. 130 */ 131#define OLDINSTR_2(oldinstr, num1, num2) \ 132 "# ALT: oldinstr2\n" \ 133 "661:\n\t" oldinstr "\n662:\n" \ 134 "# ALT: padding2\n" \ 135 ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \ 136 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \ 137 alt_end_marker ":\n" 138 139#define OLDINSTR_3(oldinsn, n1, n2, n3) \ 140 "# ALT: oldinstr3\n" \ 141 "661:\n\t" oldinsn "\n662:\n" \ 142 "# ALT: padding3\n" \ 143 ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 144 " - (" alt_slen ")) > 0) * " \ 145 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \ 146 " - (" alt_slen ")), 0x90\n" \ 147 alt_end_marker ":\n" 148 149#define ALTINSTR_ENTRY(feature, num) \ 150 " .long 661b - .\n" /* label */ \ 151 " .long " b_replacement(num)"f - .\n" /* new instruction */ \ 152 " .word " __stringify(feature) "\n" /* feature bit */ \ 153 " .byte " alt_total_slen "\n" /* source len */ \ 154 " .byte " alt_rlen(num) "\n" /* replacement len */ 155 156#define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \ 157 "# ALT: replacement " #num "\n" \ 158 b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n" 159 160/* alternative assembly primitive: */ 161#define ALTERNATIVE(oldinstr, newinstr, feature) \ 162 OLDINSTR(oldinstr, 1) \ 163 ".pushsection .altinstructions,\"a\"\n" \ 164 ALTINSTR_ENTRY(feature, 1) \ 165 ".popsection\n" \ 166 ".pushsection .altinstr_replacement, \"ax\"\n" \ 167 ALTINSTR_REPLACEMENT(newinstr, feature, 1) \ 168 ".popsection\n" 169 170#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\ 171 OLDINSTR_2(oldinstr, 1, 2) \ 172 ".pushsection .altinstructions,\"a\"\n" \ 173 ALTINSTR_ENTRY(feature1, 1) \ 174 ALTINSTR_ENTRY(feature2, 2) \ 175 ".popsection\n" \ 176 ".pushsection .altinstr_replacement, \"ax\"\n" \ 177 ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \ 178 ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \ 179 ".popsection\n" 180 181/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 182#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \ 183 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 184 newinstr_yes, feature) 185 186#define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \ 187 OLDINSTR_3(oldinsn, 1, 2, 3) \ 188 ".pushsection .altinstructions,\"a\"\n" \ 189 ALTINSTR_ENTRY(feat1, 1) \ 190 ALTINSTR_ENTRY(feat2, 2) \ 191 ALTINSTR_ENTRY(feat3, 3) \ 192 ".popsection\n" \ 193 ".pushsection .altinstr_replacement, \"ax\"\n" \ 194 ALTINSTR_REPLACEMENT(newinsn1, feat1, 1) \ 195 ALTINSTR_REPLACEMENT(newinsn2, feat2, 2) \ 196 ALTINSTR_REPLACEMENT(newinsn3, feat3, 3) \ 197 ".popsection\n" 198 199/* 200 * Alternative instructions for different CPU types or capabilities. 201 * 202 * This allows to use optimized instructions even on generic binary 203 * kernels. 204 * 205 * length of oldinstr must be longer or equal the length of newinstr 206 * It can be padded with nops as needed. 207 * 208 * For non barrier like inlines please define new variants 209 * without volatile and memory clobber. 210 */ 211#define alternative(oldinstr, newinstr, feature) \ 212 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory") 213 214#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \ 215 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory") 216 217#define alternative_ternary(oldinstr, feature, newinstr_yes, newinstr_no) \ 218 asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) ::: "memory") 219 220/* 221 * Alternative inline assembly with input. 222 * 223 * Peculiarities: 224 * No memory clobber here. 225 * Argument numbers start with 1. 226 * Leaving an unused argument 0 to keep API compatibility. 227 */ 228#define alternative_input(oldinstr, newinstr, feature, input...) \ 229 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 230 : : "i" (0), ## input) 231 232/* 233 * This is similar to alternative_input. But it has two features and 234 * respective instructions. 235 * 236 * If CPU has feature2, newinstr2 is used. 237 * Otherwise, if CPU has feature1, newinstr1 is used. 238 * Otherwise, oldinstr is used. 239 */ 240#define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \ 241 feature2, input...) \ 242 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \ 243 newinstr2, feature2) \ 244 : : "i" (0), ## input) 245 246/* Like alternative_input, but with a single output argument */ 247#define alternative_io(oldinstr, newinstr, feature, output, input...) \ 248 asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) \ 249 : output : "i" (0), ## input) 250 251/* Like alternative_io, but for replacing a direct call with another one. */ 252#define alternative_call(oldfunc, newfunc, feature, output, input...) \ 253 asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \ 254 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) 255 256/* 257 * Like alternative_call, but there are two features and respective functions. 258 * If CPU has feature2, function2 is used. 259 * Otherwise, if CPU has feature1, function1 is used. 260 * Otherwise, old function is used. 261 */ 262#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ 263 output, input...) \ 264 asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ 265 "call %P[new2]", feature2) \ 266 : output, ASM_CALL_CONSTRAINT \ 267 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 268 [new2] "i" (newfunc2), ## input) 269 270/* 271 * use this macro(s) if you need more than one output parameter 272 * in alternative_io 273 */ 274#define ASM_OUTPUT2(a...) a 275 276/* 277 * use this macro if you need clobbers but no inputs in 278 * alternative_{input,io,call}() 279 */ 280#define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr 281 282#else /* __ASSEMBLY__ */ 283 284#ifdef CONFIG_SMP 285 .macro LOCK_PREFIX 286672: lock 287 .pushsection .smp_locks,"a" 288 .balign 4 289 .long 672b - . 290 .popsection 291 .endm 292#else 293 .macro LOCK_PREFIX 294 .endm 295#endif 296 297/* 298 * objtool annotation to ignore the alternatives and only consider the original 299 * instruction(s). 300 */ 301.macro ANNOTATE_IGNORE_ALTERNATIVE 302 .Lannotate_\@: 303 .pushsection .discard.ignore_alts 304 .long .Lannotate_\@ - . 305 .popsection 306.endm 307 308/* 309 * Issue one struct alt_instr descriptor entry (need to put it into 310 * the section .altinstructions, see below). This entry contains 311 * enough information for the alternatives patching code to patch an 312 * instruction. See apply_alternatives(). 313 */ 314.macro altinstruction_entry orig alt feature orig_len alt_len 315 .long \orig - . 316 .long \alt - . 317 .word \feature 318 .byte \orig_len 319 .byte \alt_len 320.endm 321 322/* 323 * Define an alternative between two instructions. If @feature is 324 * present, early code in apply_alternatives() replaces @oldinstr with 325 * @newinstr. ".skip" directive takes care of proper instruction padding 326 * in case @newinstr is longer than @oldinstr. 327 */ 328.macro ALTERNATIVE oldinstr, newinstr, feature 329140: 330 \oldinstr 331141: 332 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90 333142: 334 335 .pushsection .altinstructions,"a" 336 altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f 337 .popsection 338 339 .pushsection .altinstr_replacement,"ax" 340143: 341 \newinstr 342144: 343 .popsection 344.endm 345 346#define old_len 141b-140b 347#define new_len1 144f-143f 348#define new_len2 145f-144f 349 350/* 351 * gas compatible max based on the idea from: 352 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax 353 * 354 * The additional "-" is needed because gas uses a "true" value of -1. 355 */ 356#define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b))))) 357 358 359/* 360 * Same as ALTERNATIVE macro above but for two alternatives. If CPU 361 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has 362 * @feature2, it replaces @oldinstr with @feature2. 363 */ 364.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2 365140: 366 \oldinstr 367141: 368 .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \ 369 (alt_max_short(new_len1, new_len2) - (old_len)),0x90 370142: 371 372 .pushsection .altinstructions,"a" 373 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f 374 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f 375 .popsection 376 377 .pushsection .altinstr_replacement,"ax" 378143: 379 \newinstr1 380144: 381 \newinstr2 382145: 383 .popsection 384.endm 385 386/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 387#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \ 388 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 389 newinstr_yes, feature 390 391#endif /* __ASSEMBLY__ */ 392 393#endif /* _ASM_X86_ALTERNATIVE_H */ 394