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 <linux/objtool.h> 8 #include <asm/asm.h> 9 10 #define ALT_FLAGS_SHIFT 16 11 12 #define ALT_FLAG_NOT (1 << 0) 13 #define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature)) 14 #define ALT_FLAG_DIRECT_CALL (1 << 1) 15 #define ALT_DIRECT_CALL(feature) ((ALT_FLAG_DIRECT_CALL << ALT_FLAGS_SHIFT) | (feature)) 16 #define ALT_CALL_ALWAYS ALT_DIRECT_CALL(X86_FEATURE_ALWAYS) 17 18 #ifndef __ASSEMBLY__ 19 20 #include <linux/stddef.h> 21 22 /* 23 * Alternative inline assembly for SMP. 24 * 25 * The LOCK_PREFIX macro defined here replaces the LOCK and 26 * LOCK_PREFIX macros used everywhere in the source tree. 27 * 28 * SMP alternatives use the same data structures as the other 29 * alternatives and the X86_FEATURE_UP flag to indicate the case of a 30 * UP system running a SMP kernel. The existing apply_alternatives() 31 * works fine for patching a SMP kernel for UP. 32 * 33 * The SMP alternative tables can be kept after boot and contain both 34 * UP and SMP versions of the instructions to allow switching back to 35 * SMP at runtime, when hotplugging in a new CPU, which is especially 36 * useful in virtualized environments. 37 * 38 * The very common lock prefix is handled as special case in a 39 * separate table which is a pure address list without replacement ptr 40 * and size information. That keeps the table sizes small. 41 */ 42 43 #ifdef CONFIG_SMP 44 #define LOCK_PREFIX_HERE \ 45 ".pushsection .smp_locks,\"a\"\n" \ 46 ".balign 4\n" \ 47 ".long 671f - .\n" /* offset */ \ 48 ".popsection\n" \ 49 "671:" 50 51 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; " 52 53 #else /* ! CONFIG_SMP */ 54 #define LOCK_PREFIX_HERE "" 55 #define LOCK_PREFIX "" 56 #endif 57 58 /* 59 * The patching flags are part of the upper bits of the @ft_flags parameter when 60 * specifying them. The split is currently like this: 61 * 62 * [31... flags ...16][15... CPUID feature bit ...0] 63 * 64 * but since this is all hidden in the macros argument being split, those fields can be 65 * extended in the future to fit in a u64 or however the need arises. 66 */ 67 struct alt_instr { 68 s32 instr_offset; /* original instruction */ 69 s32 repl_offset; /* offset to replacement instruction */ 70 71 union { 72 struct { 73 u32 cpuid: 16; /* CPUID bit set for replacement */ 74 u32 flags: 16; /* patching control flags */ 75 }; 76 u32 ft_flags; 77 }; 78 79 u8 instrlen; /* length of original instruction */ 80 u8 replacementlen; /* length of new instruction */ 81 } __packed; 82 83 extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; 84 85 /* 86 * Debug flag that can be tested to see whether alternative 87 * instructions were patched in already: 88 */ 89 extern int alternatives_patched; 90 struct module; 91 92 extern void alternative_instructions(void); 93 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end, 94 struct module *mod); 95 extern void apply_retpolines(s32 *start, s32 *end, struct module *mod); 96 extern void apply_returns(s32 *start, s32 *end, struct module *mod); 97 extern void apply_seal_endbr(s32 *start, s32 *end, struct module *mod); 98 extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine, 99 s32 *start_cfi, s32 *end_cfi, struct module *mod); 100 101 struct callthunk_sites { 102 s32 *call_start, *call_end; 103 struct alt_instr *alt_start, *alt_end; 104 }; 105 106 #ifdef CONFIG_CALL_THUNKS 107 extern void callthunks_patch_builtin_calls(void); 108 extern void callthunks_patch_module_calls(struct callthunk_sites *sites, 109 struct module *mod); 110 extern void *callthunks_translate_call_dest(void *dest); 111 extern int x86_call_depth_emit_accounting(u8 **pprog, void *func, void *ip); 112 #else 113 static __always_inline void callthunks_patch_builtin_calls(void) {} 114 static __always_inline void 115 callthunks_patch_module_calls(struct callthunk_sites *sites, 116 struct module *mod) {} 117 static __always_inline void *callthunks_translate_call_dest(void *dest) 118 { 119 return dest; 120 } 121 static __always_inline int x86_call_depth_emit_accounting(u8 **pprog, 122 void *func, void *ip) 123 { 124 return 0; 125 } 126 #endif 127 128 #ifdef CONFIG_SMP 129 extern void alternatives_smp_module_add(struct module *mod, char *name, 130 void *locks, void *locks_end, 131 void *text, void *text_end); 132 extern void alternatives_smp_module_del(struct module *mod); 133 extern void alternatives_enable_smp(void); 134 extern int alternatives_text_reserved(void *start, void *end); 135 extern bool skip_smp_alternatives; 136 #else 137 static inline void alternatives_smp_module_add(struct module *mod, char *name, 138 void *locks, void *locks_end, 139 void *text, void *text_end) {} 140 static inline void alternatives_smp_module_del(struct module *mod) {} 141 static inline void alternatives_enable_smp(void) {} 142 static inline int alternatives_text_reserved(void *start, void *end) 143 { 144 return 0; 145 } 146 #endif /* CONFIG_SMP */ 147 148 #define ALT_CALL_INSTR "call BUG_func" 149 150 #define alt_slen "772b-771b" 151 #define alt_total_slen "773b-771b" 152 #define alt_rlen "775f-774f" 153 154 #define OLDINSTR(oldinstr) \ 155 "# ALT: oldinstr\n" \ 156 "771:\n\t" oldinstr "\n772:\n" \ 157 "# ALT: padding\n" \ 158 ".skip -(((" alt_rlen ")-(" alt_slen ")) > 0) * " \ 159 "((" alt_rlen ")-(" alt_slen ")),0x90\n" \ 160 "773:\n" 161 162 #define ALTINSTR_ENTRY(ft_flags) \ 163 ".pushsection .altinstructions,\"a\"\n" \ 164 " .long 771b - .\n" /* label */ \ 165 " .long 774f - .\n" /* new instruction */ \ 166 " .4byte " __stringify(ft_flags) "\n" /* feature + flags */ \ 167 " .byte " alt_total_slen "\n" /* source len */ \ 168 " .byte " alt_rlen "\n" /* replacement len */ \ 169 ".popsection\n" 170 171 #define ALTINSTR_REPLACEMENT(newinstr) /* replacement */ \ 172 ".pushsection .altinstr_replacement, \"ax\"\n" \ 173 "# ALT: replacement\n" \ 174 "774:\n\t" newinstr "\n775:\n" \ 175 ".popsection\n" 176 177 /* alternative assembly primitive: */ 178 #define ALTERNATIVE(oldinstr, newinstr, ft_flags) \ 179 OLDINSTR(oldinstr) \ 180 ALTINSTR_ENTRY(ft_flags) \ 181 ALTINSTR_REPLACEMENT(newinstr) 182 183 #define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \ 184 ALTERNATIVE(ALTERNATIVE(oldinstr, newinstr1, ft_flags1), newinstr2, ft_flags2) 185 186 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 187 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \ 188 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, newinstr_yes, ft_flags) 189 190 #define ALTERNATIVE_3(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, \ 191 newinstr3, ft_flags3) \ 192 ALTERNATIVE(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2), \ 193 newinstr3, ft_flags3) 194 195 /* 196 * Alternative instructions for different CPU types or capabilities. 197 * 198 * This allows to use optimized instructions even on generic binary 199 * kernels. 200 * 201 * length of oldinstr must be longer or equal the length of newinstr 202 * It can be padded with nops as needed. 203 * 204 * For non barrier like inlines please define new variants 205 * without volatile and memory clobber. 206 */ 207 #define alternative(oldinstr, newinstr, ft_flags) \ 208 asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory") 209 210 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \ 211 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory") 212 213 /* 214 * Alternative inline assembly with input. 215 * 216 * Peculiarities: 217 * No memory clobber here. 218 * Argument numbers start with 1. 219 * Leaving an unused argument 0 to keep API compatibility. 220 */ 221 #define alternative_input(oldinstr, newinstr, ft_flags, input...) \ 222 asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) \ 223 : : "i" (0), ## input) 224 225 /* Like alternative_input, but with a single output argument */ 226 #define alternative_io(oldinstr, newinstr, ft_flags, output, input...) \ 227 asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) \ 228 : output : "i" (0), ## input) 229 230 /* 231 * Like alternative_io, but for replacing a direct call with another one. 232 * 233 * Use the %c operand modifier which is the generic way to print a bare 234 * constant expression with all syntax-specific punctuation omitted. %P 235 * is the x86-specific variant which can handle constants too, for 236 * historical reasons, but it should be used primarily for PIC 237 * references: i.e., if used for a function, it would add the PLT 238 * suffix. 239 */ 240 #define alternative_call(oldfunc, newfunc, ft_flags, output, input...) \ 241 asm_inline volatile(ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \ 242 : ALT_OUTPUT_SP(output) \ 243 : [old] "i" (oldfunc), [new] "i" (newfunc), ## input) 244 245 /* 246 * Like alternative_call, but there are two features and respective functions. 247 * If CPU has feature2, function2 is used. 248 * Otherwise, if CPU has feature1, function1 is used. 249 * Otherwise, old function is used. 250 */ 251 #define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2, \ 252 output, input...) \ 253 asm_inline volatile(ALTERNATIVE_2("call %c[old]", "call %c[new1]", ft_flags1, \ 254 "call %c[new2]", ft_flags2) \ 255 : ALT_OUTPUT_SP(output) \ 256 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 257 [new2] "i" (newfunc2), ## input) 258 259 /* 260 * use this macro(s) if you need more than one output parameter 261 * in alternative_io 262 */ 263 #define ASM_OUTPUT2(a...) a 264 265 /* 266 * use this macro if you need clobbers but no inputs in 267 * alternative_{input,io,call}() 268 */ 269 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr 270 271 #define ALT_OUTPUT_SP(...) ASM_CALL_CONSTRAINT, ## __VA_ARGS__ 272 273 /* Macro for creating assembler functions avoiding any C magic. */ 274 #define DEFINE_ASM_FUNC(func, instr, sec) \ 275 asm (".pushsection " #sec ", \"ax\"\n" \ 276 ".global " #func "\n\t" \ 277 ".type " #func ", @function\n\t" \ 278 ASM_FUNC_ALIGN "\n" \ 279 #func ":\n\t" \ 280 ASM_ENDBR \ 281 instr "\n\t" \ 282 ASM_RET \ 283 ".size " #func ", . - " #func "\n\t" \ 284 ".popsection") 285 286 void BUG_func(void); 287 void nop_func(void); 288 289 #else /* __ASSEMBLY__ */ 290 291 #ifdef CONFIG_SMP 292 .macro LOCK_PREFIX 293 672: lock 294 .pushsection .smp_locks,"a" 295 .balign 4 296 .long 672b - . 297 .popsection 298 .endm 299 #else 300 .macro LOCK_PREFIX 301 .endm 302 #endif 303 304 /* 305 * Issue one struct alt_instr descriptor entry (need to put it into 306 * the section .altinstructions, see below). This entry contains 307 * enough information for the alternatives patching code to patch an 308 * instruction. See apply_alternatives(). 309 */ 310 .macro altinstr_entry orig alt ft_flags orig_len alt_len 311 .long \orig - . 312 .long \alt - . 313 .4byte \ft_flags 314 .byte \orig_len 315 .byte \alt_len 316 .endm 317 318 .macro ALT_CALL_INSTR 319 call BUG_func 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 #define __ALTERNATIVE(oldinst, newinst, flag) \ 329 740: \ 330 oldinst ; \ 331 741: \ 332 .skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ;\ 333 742: \ 334 .pushsection .altinstructions,"a" ; \ 335 altinstr_entry 740b,743f,flag,742b-740b,744f-743f ; \ 336 .popsection ; \ 337 .pushsection .altinstr_replacement,"ax" ; \ 338 743: \ 339 newinst ; \ 340 744: \ 341 .popsection ; 342 343 .macro ALTERNATIVE oldinstr, newinstr, ft_flags 344 __ALTERNATIVE(\oldinstr, \newinstr, \ft_flags) 345 .endm 346 347 #define old_len 141b-140b 348 #define new_len1 144f-143f 349 #define new_len2 145f-144f 350 #define new_len3 146f-145f 351 352 /* 353 * Same as ALTERNATIVE macro above but for two alternatives. If CPU 354 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has 355 * @feature2, it replaces @oldinstr with @feature2. 356 */ 357 .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2 358 __ALTERNATIVE(__ALTERNATIVE(\oldinstr, \newinstr1, \ft_flags1), 359 \newinstr2, \ft_flags2) 360 .endm 361 362 .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3 363 __ALTERNATIVE(ALTERNATIVE_2(\oldinstr, \newinstr1, \ft_flags1, \newinstr2, \ft_flags2), 364 \newinstr3, \ft_flags3) 365 .endm 366 367 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 368 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \ 369 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 370 newinstr_yes, ft_flags 371 372 #endif /* __ASSEMBLY__ */ 373 374 #endif /* _ASM_X86_ALTERNATIVE_H */ 375