arch/x86/include/asm/alternative.h

   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 ALT_FLAGS_SHIFT         16
  10
  11 #define ALT_FLAG_NOT            (1 << 0)
  12 #define ALT_NOT(feature)        ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))
  13 #define ALT_FLAG_DIRECT_CALL    (1 << 1)
  14 #define ALT_DIRECT_CALL(feature) ((ALT_FLAG_DIRECT_CALL << ALT_FLAGS_SHIFT) | (feature))
  15 #define ALT_CALL_ALWAYS         ALT_DIRECT_CALL(X86_FEATURE_ALWAYS)
  16
  17 #ifndef __ASSEMBLY__
  18
  19 #include <linux/stddef.h>
  20
  21 /*
  22  * Alternative inline assembly for SMP.
  23  *
  24  * The LOCK_PREFIX macro defined here replaces the LOCK and
  25  * LOCK_PREFIX macros used everywhere in the source tree.
  26  *
  27  * SMP alternatives use the same data structures as the other
  28  * alternatives and the X86_FEATURE_UP flag to indicate the case of a
  29  * UP system running a SMP kernel.  The existing apply_alternatives()
  30  * works fine for patching a SMP kernel for UP.
  31  *
  32  * The SMP alternative tables can be kept after boot and contain both
  33  * UP and SMP versions of the instructions to allow switching back to
  34  * SMP at runtime, when hotplugging in a new CPU, which is especially
  35  * useful in virtualized environments.
  36  *
  37  * The very common lock prefix is handled as special case in a
  38  * separate table which is a pure address list without replacement ptr
  39  * and size information.  That keeps the table sizes small.
  40  */
  41
  42 #ifdef CONFIG_SMP
  43 #define LOCK_PREFIX_HERE \
  44                 ".pushsection .smp_locks,\"a\"\n"       \
  45                 ".balign 4\n"                           \
  46                 ".long 671f - .\n" /* offset */         \
  47                 ".popsection\n"                         \
  48                 "671:"
  49
  50 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
  51
  52 #else /* ! CONFIG_SMP */
  53 #define LOCK_PREFIX_HERE ""
  54 #define LOCK_PREFIX ""
  55 #endif
  56
  57 /*
  58  * objtool annotation to ignore the alternatives and only consider the original
  59  * instruction(s).
  60  */
  61 #define ANNOTATE_IGNORE_ALTERNATIVE                             \
  62         "999:\n\t"                                              \
  63         ".pushsection .discard.ignore_alts\n\t"                 \
  64         ".long 999b\n\t"                                        \
  65         ".popsection\n\t"
  66
  67 /*
  68  * The patching flags are part of the upper bits of the @ft_flags parameter when
  69  * specifying them. The split is currently like this:
  70  *
  71  * [31... flags ...16][15... CPUID feature bit ...0]
  72  *
  73  * but since this is all hidden in the macros argument being split, those fields can be
  74  * extended in the future to fit in a u64 or however the need arises.
  75  */
  76 struct alt_instr {
  77         s32 instr_offset;       /* original instruction */
  78         s32 repl_offset;        /* offset to replacement instruction */
  79
  80         union {
  81                 struct {
  82                         u32 cpuid: 16;  /* CPUID bit set for replacement */
  83                         u32 flags: 16;  /* patching control flags */
  84                 };
  85                 u32 ft_flags;
  86         };
  87
  88         u8  instrlen;           /* length of original instruction */
  89         u8  replacementlen;     /* length of new instruction */
  90 } __packed;
  91
  92 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
  93
  94 /*
  95  * Debug flag that can be tested to see whether alternative
  96  * instructions were patched in already:
  97  */
  98 extern int alternatives_patched;
  99
 100 extern void alternative_instructions(void);
 101 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
 102 extern void apply_retpolines(s32 *start, s32 *end);
 103 extern void apply_returns(s32 *start, s32 *end);
 104 extern void apply_seal_endbr(s32 *start, s32 *end);
 105 extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine,
 106                           s32 *start_cfi, s32 *end_cfi);
 107
 108 struct module;
 109
 110 struct callthunk_sites {
 111         s32                             *call_start, *call_end;
 112         struct alt_instr                *alt_start, *alt_end;
 113 };
 114
 115 #ifdef CONFIG_CALL_THUNKS
 116 extern void callthunks_patch_builtin_calls(void);
 117 extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
 118                                           struct module *mod);
 119 extern void *callthunks_translate_call_dest(void *dest);
 120 extern int x86_call_depth_emit_accounting(u8 **pprog, void *func, void *ip);
 121 #else
 122 static __always_inline void callthunks_patch_builtin_calls(void) {}
 123 static __always_inline void
 124 callthunks_patch_module_calls(struct callthunk_sites *sites,
 125                               struct module *mod) {}
 126 static __always_inline void *callthunks_translate_call_dest(void *dest)
 127 {
 128         return dest;
 129 }
 130 static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
 131                                                           void *func, void *ip)
 132 {
 133         return 0;
 134 }
 135 #endif
 136
 137 #ifdef CONFIG_SMP
 138 extern void alternatives_smp_module_add(struct module *mod, char *name,
 139                                         void *locks, void *locks_end,
 140                                         void *text, void *text_end);
 141 extern void alternatives_smp_module_del(struct module *mod);
 142 extern void alternatives_enable_smp(void);
 143 extern int alternatives_text_reserved(void *start, void *end);
 144 extern bool skip_smp_alternatives;
 145 #else
 146 static inline void alternatives_smp_module_add(struct module *mod, char *name,
 147                                                void *locks, void *locks_end,
 148                                                void *text, void *text_end) {}
 149 static inline void alternatives_smp_module_del(struct module *mod) {}
 150 static inline void alternatives_enable_smp(void) {}
 151 static inline int alternatives_text_reserved(void *start, void *end)
 152 {
 153         return 0;
 154 }
 155 #endif  /* CONFIG_SMP */
 156
 157 #define ALT_CALL_INSTR          "call BUG_func"
 158
 159 #define b_replacement(num)      "664"#num
 160 #define e_replacement(num)      "665"#num
 161
 162 #define alt_end_marker          "663"
 163 #define alt_slen                "662b-661b"
 164 #define alt_total_slen          alt_end_marker"b-661b"
 165 #define alt_rlen(num)           e_replacement(num)"f-"b_replacement(num)"f"
 166
 167 #define OLDINSTR(oldinstr, num)                                         \
 168         "# ALT: oldnstr\n"                                              \
 169         "661:\n\t" oldinstr "\n662:\n"                                  \
 170         "# ALT: padding\n"                                              \
 171         ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * "          \
 172                 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"           \
 173         alt_end_marker ":\n"
 174
 175 /*
 176  * gas compatible max based on the idea from:
 177  * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
 178  *
 179  * The additional "-" is needed because gas uses a "true" value of -1.
 180  */
 181 #define alt_max_short(a, b)     "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"
 182
 183 /*
 184  * Pad the second replacement alternative with additional NOPs if it is
 185  * additionally longer than the first replacement alternative.
 186  */
 187 #define OLDINSTR_2(oldinstr, num1, num2) \
 188         "# ALT: oldinstr2\n"                                                                    \
 189         "661:\n\t" oldinstr "\n662:\n"                                                          \
 190         "# ALT: padding2\n"                                                                     \
 191         ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * "  \
 192                 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n"  \
 193         alt_end_marker ":\n"
 194
 195 #define OLDINSTR_3(oldinsn, n1, n2, n3)                                                         \
 196         "# ALT: oldinstr3\n"                                                                    \
 197         "661:\n\t" oldinsn "\n662:\n"                                                           \
 198         "# ALT: padding3\n"                                                                     \
 199         ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3))      \
 200                 " - (" alt_slen ")) > 0) * "                                                    \
 201                 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3))      \
 202                 " - (" alt_slen ")), 0x90\n"                                                    \
 203         alt_end_marker ":\n"
 204
 205 #define ALTINSTR_ENTRY(ft_flags, num)                                         \
 206         " .long 661b - .\n"                             /* label           */ \
 207         " .long " b_replacement(num)"f - .\n"           /* new instruction */ \
 208         " .4byte " __stringify(ft_flags) "\n"           /* feature + flags */ \
 209         " .byte " alt_total_slen "\n"                   /* source len      */ \
 210         " .byte " alt_rlen(num) "\n"                    /* replacement len */
 211
 212 #define ALTINSTR_REPLACEMENT(newinstr, num)             /* replacement */       \
 213         "# ALT: replacement " #num "\n"                                         \
 214         b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"
 215
 216 /* alternative assembly primitive: */
 217 #define ALTERNATIVE(oldinstr, newinstr, ft_flags)                       \
 218         OLDINSTR(oldinstr, 1)                                           \
 219         ".pushsection .altinstructions,\"a\"\n"                         \
 220         ALTINSTR_ENTRY(ft_flags, 1)                                     \
 221         ".popsection\n"                                                 \
 222         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
 223         ALTINSTR_REPLACEMENT(newinstr, 1)                               \
 224         ".popsection\n"
 225
 226 #define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
 227         OLDINSTR_2(oldinstr, 1, 2)                                      \
 228         ".pushsection .altinstructions,\"a\"\n"                         \
 229         ALTINSTR_ENTRY(ft_flags1, 1)                                    \
 230         ALTINSTR_ENTRY(ft_flags2, 2)                                    \
 231         ".popsection\n"                                                 \
 232         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
 233         ALTINSTR_REPLACEMENT(newinstr1, 1)                              \
 234         ALTINSTR_REPLACEMENT(newinstr2, 2)                              \
 235         ".popsection\n"
 236
 237 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
 238 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
 239         ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,        \
 240                       newinstr_yes, ft_flags)
 241
 242 #define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \
 243                         newinsn3, ft_flags3)                            \
 244         OLDINSTR_3(oldinsn, 1, 2, 3)                                    \
 245         ".pushsection .altinstructions,\"a\"\n"                         \
 246         ALTINSTR_ENTRY(ft_flags1, 1)                                    \
 247         ALTINSTR_ENTRY(ft_flags2, 2)                                    \
 248         ALTINSTR_ENTRY(ft_flags3, 3)                                    \
 249         ".popsection\n"                                                 \
 250         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
 251         ALTINSTR_REPLACEMENT(newinsn1, 1)                               \
 252         ALTINSTR_REPLACEMENT(newinsn2, 2)                               \
 253         ALTINSTR_REPLACEMENT(newinsn3, 3)                               \
 254         ".popsection\n"
 255
 256 /*
 257  * Alternative instructions for different CPU types or capabilities.
 258  *
 259  * This allows to use optimized instructions even on generic binary
 260  * kernels.
 261  *
 262  * length of oldinstr must be longer or equal the length of newinstr
 263  * It can be padded with nops as needed.
 264  *
 265  * For non barrier like inlines please define new variants
 266  * without volatile and memory clobber.
 267  */
 268 #define alternative(oldinstr, newinstr, ft_flags)                       \
 269         asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
 270
 271 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
 272         asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
 273
 274 #define alternative_ternary(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
 275         asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) ::: "memory")
 276
 277 /*
 278  * Alternative inline assembly with input.
 279  *
 280  * Peculiarities:
 281  * No memory clobber here.
 282  * Argument numbers start with 1.
 283  * Leaving an unused argument 0 to keep API compatibility.
 284  */
 285 #define alternative_input(oldinstr, newinstr, ft_flags, input...)       \
 286         asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags)  \
 287                 : : "i" (0), ## input)
 288
 289 /* Like alternative_input, but with a single output argument */
 290 #define alternative_io(oldinstr, newinstr, ft_flags, output, input...)  \
 291         asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags)  \
 292                 : output : "i" (0), ## input)
 293
 294 /* Like alternative_io, but for replacing a direct call with another one. */
 295 #define alternative_call(oldfunc, newfunc, ft_flags, output, input...)  \
 296         asm_inline volatile (ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \
 297                 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
 298
 299 /*
 300  * Like alternative_call, but there are two features and respective functions.
 301  * If CPU has feature2, function2 is used.
 302  * Otherwise, if CPU has feature1, function1 is used.
 303  * Otherwise, old function is used.
 304  */
 305 #define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2, \
 306                            output, input...)                            \
 307         asm_inline volatile (ALTERNATIVE_2("call %c[old]", "call %c[new1]", ft_flags1, \
 308                 "call %c[new2]", ft_flags2)                             \
 309                 : output, ASM_CALL_CONSTRAINT                           \
 310                 : [old] "i" (oldfunc), [new1] "i" (newfunc1),           \
 311                   [new2] "i" (newfunc2), ## input)
 312
 313 /*
 314  * use this macro(s) if you need more than one output parameter
 315  * in alternative_io
 316  */
 317 #define ASM_OUTPUT2(a...) a
 318
 319 /*
 320  * use this macro if you need clobbers but no inputs in
 321  * alternative_{input,io,call}()
 322  */
 323 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
 324
 325 /* Macro for creating assembler functions avoiding any C magic. */
 326 #define DEFINE_ASM_FUNC(func, instr, sec)               \
 327         asm (".pushsection " #sec ", \"ax\"\n"          \
 328              ".global " #func "\n\t"                    \
 329              ".type " #func ", @function\n\t"           \
 330              ASM_FUNC_ALIGN "\n"                        \
 331              #func ":\n\t"                              \
 332              ASM_ENDBR                                  \
 333              instr "\n\t"                               \
 334              ASM_RET                                    \
 335              ".size " #func ", . - " #func "\n\t"       \
 336              ".popsection")
 337
 338 void BUG_func(void);
 339 void nop_func(void);
 340
 341 #else /* __ASSEMBLY__ */
 342
 343 #ifdef CONFIG_SMP
 344         .macro LOCK_PREFIX
 345 672:    lock
 346         .pushsection .smp_locks,"a"
 347         .balign 4
 348         .long 672b - .
 349         .popsection
 350         .endm
 351 #else
 352         .macro LOCK_PREFIX
 353         .endm
 354 #endif
 355
 356 /*
 357  * objtool annotation to ignore the alternatives and only consider the original
 358  * instruction(s).
 359  */
 360 .macro ANNOTATE_IGNORE_ALTERNATIVE
 361         .Lannotate_\@:
 362         .pushsection .discard.ignore_alts
 363         .long .Lannotate_\@
 364         .popsection
 365 .endm
 366
 367 /*
 368  * Issue one struct alt_instr descriptor entry (need to put it into
 369  * the section .altinstructions, see below). This entry contains
 370  * enough information for the alternatives patching code to patch an
 371  * instruction. See apply_alternatives().
 372  */
 373 .macro altinstr_entry orig alt ft_flags orig_len alt_len
 374         .long \orig - .
 375         .long \alt - .
 376         .4byte \ft_flags
 377         .byte \orig_len
 378         .byte \alt_len
 379 .endm
 380
 381 .macro ALT_CALL_INSTR
 382         call BUG_func
 383 .endm
 384
 385 /*
 386  * Define an alternative between two instructions. If @feature is
 387  * present, early code in apply_alternatives() replaces @oldinstr with
 388  * @newinstr. ".skip" directive takes care of proper instruction padding
 389  * in case @newinstr is longer than @oldinstr.
 390  */
 391 .macro ALTERNATIVE oldinstr, newinstr, ft_flags
 392 140:
 393         \oldinstr
 394 141:
 395         .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
 396 142:
 397
 398         .pushsection .altinstructions,"a"
 399         altinstr_entry 140b,143f,\ft_flags,142b-140b,144f-143f
 400         .popsection
 401
 402         .pushsection .altinstr_replacement,"ax"
 403 143:
 404         \newinstr
 405 144:
 406         .popsection
 407 .endm
 408
 409 #define old_len                 141b-140b
 410 #define new_len1                144f-143f
 411 #define new_len2                145f-144f
 412 #define new_len3                146f-145f
 413
 414 /*
 415  * gas compatible max based on the idea from:
 416  * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
 417  *
 418  * The additional "-" is needed because gas uses a "true" value of -1.
 419  */
 420 #define alt_max_2(a, b)         ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
 421 #define alt_max_3(a, b, c)      (alt_max_2(alt_max_2(a, b), c))
 422
 423
 424 /*
 425  * Same as ALTERNATIVE macro above but for two alternatives. If CPU
 426  * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
 427  * @feature2, it replaces @oldinstr with @feature2.
 428  */
 429 .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
 430 140:
 431         \oldinstr
 432 141:
 433         .skip -((alt_max_2(new_len1, new_len2) - (old_len)) > 0) * \
 434                 (alt_max_2(new_len1, new_len2) - (old_len)),0x90
 435 142:
 436
 437         .pushsection .altinstructions,"a"
 438         altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
 439         altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
 440         .popsection
 441
 442         .pushsection .altinstr_replacement,"ax"
 443 143:
 444         \newinstr1
 445 144:
 446         \newinstr2
 447 145:
 448         .popsection
 449 .endm
 450
 451 .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
 452 140:
 453         \oldinstr
 454 141:
 455         .skip -((alt_max_3(new_len1, new_len2, new_len3) - (old_len)) > 0) * \
 456                 (alt_max_3(new_len1, new_len2, new_len3) - (old_len)),0x90
 457 142:
 458
 459         .pushsection .altinstructions,"a"
 460         altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
 461         altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
 462         altinstr_entry 140b,145f,\ft_flags3,142b-140b,146f-145f
 463         .popsection
 464
 465         .pushsection .altinstr_replacement,"ax"
 466 143:
 467         \newinstr1
 468 144:
 469         \newinstr2
 470 145:
 471         \newinstr3
 472 146:
 473         .popsection
 474 .endm
 475
 476 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
 477 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
 478         ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS,        \
 479         newinstr_yes, ft_flags
 480
 481 #endif /* __ASSEMBLY__ */
 482
 483 #endif /* _ASM_X86_ALTERNATIVE_H */