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
  14 #ifndef __ASSEMBLY__
  15
  16 #include <linux/stddef.h>
  17
  18 /*
  19  * Alternative inline assembly for SMP.
  20  *
  21  * The LOCK_PREFIX macro defined here replaces the LOCK and
  22  * LOCK_PREFIX macros used everywhere in the source tree.
  23  *
  24  * SMP alternatives use the same data structures as the other
  25  * alternatives and the X86_FEATURE_UP flag to indicate the case of a
  26  * UP system running a SMP kernel.  The existing apply_alternatives()
  27  * works fine for patching a SMP kernel for UP.
  28  *
  29  * The SMP alternative tables can be kept after boot and contain both
  30  * UP and SMP versions of the instructions to allow switching back to
  31  * SMP at runtime, when hotplugging in a new CPU, which is especially
  32  * useful in virtualized environments.
  33  *
  34  * The very common lock prefix is handled as special case in a
  35  * separate table which is a pure address list without replacement ptr
  36  * and size information.  That keeps the table sizes small.
  37  */
  38
  39 #ifdef CONFIG_SMP
  40 #define LOCK_PREFIX_HERE \
  41                 ".pushsection .smp_locks,\"a\"\n"       \
  42                 ".balign 4\n"                           \
  43                 ".long 671f - .\n" /* offset */         \
  44                 ".popsection\n"                         \
  45                 "671:"
  46
  47 #define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
  48
  49 #else /* ! CONFIG_SMP */
  50 #define LOCK_PREFIX_HERE ""
  51 #define LOCK_PREFIX ""
  52 #endif
  53
  54 /*
  55  * objtool annotation to ignore the alternatives and only consider the original
  56  * instruction(s).
  57  */
  58 #define ANNOTATE_IGNORE_ALTERNATIVE                             \
  59         "999:\n\t"                                              \
  60         ".pushsection .discard.ignore_alts\n\t"                 \
  61         ".long 999b - .\n\t"                                    \
  62         ".popsection\n\t"
  63
  64 /*
  65  * The patching flags are part of the upper bits of the @ft_flags parameter when
  66  * specifying them. The split is currently like this:
  67  *
  68  * [31... flags ...16][15... CPUID feature bit ...0]
  69  *
  70  * but since this is all hidden in the macros argument being split, those fields can be
  71  * extended in the future to fit in a u64 or however the need arises.
  72  */
  73 struct alt_instr {
  74         s32 instr_offset;       /* original instruction */
  75         s32 repl_offset;        /* offset to replacement instruction */
  76
  77         union {
  78                 struct {
  79                         u32 cpuid: 16;  /* CPUID bit set for replacement */
  80                         u32 flags: 16;  /* patching control flags */
  81                 };
  82                 u32 ft_flags;
  83         };
  84
  85         u8  instrlen;           /* length of original instruction */
  86         u8  replacementlen;     /* length of new instruction */
  87 } __packed;
  88
  89 /*
  90  * Debug flag that can be tested to see whether alternative
  91  * instructions were patched in already:
  92  */
  93 extern int alternatives_patched;
  94
  95 extern void alternative_instructions(void);
  96 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
  97 extern void apply_retpolines(s32 *start, s32 *end);
  98 extern void apply_returns(s32 *start, s32 *end);
  99 extern void apply_seal_endbr(s32 *start, s32 *end);
 100 extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine,
 101                           s32 *start_cfi, s32 *end_cfi);
 102
 103 struct module;
 104 struct paravirt_patch_site;
 105
 106 struct callthunk_sites {
 107         s32                             *call_start, *call_end;
 108         struct paravirt_patch_site      *pv_start, *pv_end;
 109 };
 110
 111 #ifdef CONFIG_CALL_THUNKS
 112 extern void callthunks_patch_builtin_calls(void);
 113 extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
 114                                           struct module *mod);
 115 extern void *callthunks_translate_call_dest(void *dest);
 116 extern int x86_call_depth_emit_accounting(u8 **pprog, void *func);
 117 #else
 118 static __always_inline void callthunks_patch_builtin_calls(void) {}
 119 static __always_inline void
 120 callthunks_patch_module_calls(struct callthunk_sites *sites,
 121                               struct module *mod) {}
 122 static __always_inline void *callthunks_translate_call_dest(void *dest)
 123 {
 124         return dest;
 125 }
 126 static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
 127                                                           void *func)
 128 {
 129         return 0;
 130 }
 131 #endif
 132
 133 #ifdef CONFIG_SMP
 134 extern void alternatives_smp_module_add(struct module *mod, char *name,
 135                                         void *locks, void *locks_end,
 136                                         void *text, void *text_end);
 137 extern void alternatives_smp_module_del(struct module *mod);
 138 extern void alternatives_enable_smp(void);
 139 extern int alternatives_text_reserved(void *start, void *end);
 140 extern bool skip_smp_alternatives;
 141 #else
 142 static inline void alternatives_smp_module_add(struct module *mod, char *name,
 143                                                void *locks, void *locks_end,
 144                                                void *text, void *text_end) {}
 145 static inline void alternatives_smp_module_del(struct module *mod) {}
 146 static inline void alternatives_enable_smp(void) {}
 147 static inline int alternatives_text_reserved(void *start, void *end)
 148 {
 149         return 0;
 150 }
 151 #endif  /* CONFIG_SMP */
 152
 153 #define b_replacement(num)      "664"#num
 154 #define e_replacement(num)      "665"#num
 155
 156 #define alt_end_marker          "663"
 157 #define alt_slen                "662b-661b"
 158 #define alt_total_slen          alt_end_marker"b-661b"
 159 #define alt_rlen(num)           e_replacement(num)"f-"b_replacement(num)"f"
 160
 161 #define OLDINSTR(oldinstr, num)                                         \
 162         "# ALT: oldnstr\n"                                              \
 163         "661:\n\t" oldinstr "\n662:\n"                                  \
 164         "# ALT: padding\n"                                              \
 165         ".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * "          \
 166                 "((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"           \
 167         alt_end_marker ":\n"
 168
 169 /*
 170  * gas compatible max based on the idea from:
 171  * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
 172  *
 173  * The additional "-" is needed because gas uses a "true" value of -1.
 174  */
 175 #define alt_max_short(a, b)     "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"
 176
 177 /*
 178  * Pad the second replacement alternative with additional NOPs if it is
 179  * additionally longer than the first replacement alternative.
 180  */
 181 #define OLDINSTR_2(oldinstr, num1, num2) \
 182         "# ALT: oldinstr2\n"                                                                    \
 183         "661:\n\t" oldinstr "\n662:\n"                                                          \
 184         "# ALT: padding2\n"                                                                     \
 185         ".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * "  \
 186                 "(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n"  \
 187         alt_end_marker ":\n"
 188
 189 #define OLDINSTR_3(oldinsn, n1, n2, n3)                                                         \
 190         "# ALT: oldinstr3\n"                                                                    \
 191         "661:\n\t" oldinsn "\n662:\n"                                                           \
 192         "# ALT: padding3\n"                                                                     \
 193         ".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3))      \
 194                 " - (" alt_slen ")) > 0) * "                                                    \
 195                 "(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3))      \
 196                 " - (" alt_slen ")), 0x90\n"                                                    \
 197         alt_end_marker ":\n"
 198
 199 #define ALTINSTR_ENTRY(ft_flags, num)                                         \
 200         " .long 661b - .\n"                             /* label           */ \
 201         " .long " b_replacement(num)"f - .\n"           /* new instruction */ \
 202         " .4byte " __stringify(ft_flags) "\n"           /* feature + flags */ \
 203         " .byte " alt_total_slen "\n"                   /* source len      */ \
 204         " .byte " alt_rlen(num) "\n"                    /* replacement len */
 205
 206 #define ALTINSTR_REPLACEMENT(newinstr, num)             /* replacement */       \
 207         "# ALT: replacement " #num "\n"                                         \
 208         b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n"
 209
 210 /* alternative assembly primitive: */
 211 #define ALTERNATIVE(oldinstr, newinstr, ft_flags)                       \
 212         OLDINSTR(oldinstr, 1)                                           \
 213         ".pushsection .altinstructions,\"a\"\n"                         \
 214         ALTINSTR_ENTRY(ft_flags, 1)                                     \
 215         ".popsection\n"                                                 \
 216         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
 217         ALTINSTR_REPLACEMENT(newinstr, 1)                               \
 218         ".popsection\n"
 219
 220 #define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
 221         OLDINSTR_2(oldinstr, 1, 2)                                      \
 222         ".pushsection .altinstructions,\"a\"\n"                         \
 223         ALTINSTR_ENTRY(ft_flags1, 1)                                    \
 224         ALTINSTR_ENTRY(ft_flags2, 2)                                    \
 225         ".popsection\n"                                                 \
 226         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
 227         ALTINSTR_REPLACEMENT(newinstr1, 1)                              \
 228         ALTINSTR_REPLACEMENT(newinstr2, 2)                              \
 229         ".popsection\n"
 230
 231 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
 232 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
 233         ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,        \
 234                       newinstr_yes, ft_flags)
 235
 236 #define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \
 237                         newinsn3, ft_flags3)                            \
 238         OLDINSTR_3(oldinsn, 1, 2, 3)                                    \
 239         ".pushsection .altinstructions,\"a\"\n"                         \
 240         ALTINSTR_ENTRY(ft_flags1, 1)                                    \
 241         ALTINSTR_ENTRY(ft_flags2, 2)                                    \
 242         ALTINSTR_ENTRY(ft_flags3, 3)                                    \
 243         ".popsection\n"                                                 \
 244         ".pushsection .altinstr_replacement, \"ax\"\n"                  \
 245         ALTINSTR_REPLACEMENT(newinsn1, 1)                               \
 246         ALTINSTR_REPLACEMENT(newinsn2, 2)                               \
 247         ALTINSTR_REPLACEMENT(newinsn3, 3)                               \
 248         ".popsection\n"
 249
 250 /*
 251  * Alternative instructions for different CPU types or capabilities.
 252  *
 253  * This allows to use optimized instructions even on generic binary
 254  * kernels.
 255  *
 256  * length of oldinstr must be longer or equal the length of newinstr
 257  * It can be padded with nops as needed.
 258  *
 259  * For non barrier like inlines please define new variants
 260  * without volatile and memory clobber.
 261  */
 262 #define alternative(oldinstr, newinstr, ft_flags)                       \
 263         asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")
 264
 265 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
 266         asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")
 267
 268 #define alternative_ternary(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
 269         asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) ::: "memory")
 270
 271 /*
 272  * Alternative inline assembly with input.
 273  *
 274  * Peculiarities:
 275  * No memory clobber here.
 276  * Argument numbers start with 1.
 277  * Leaving an unused argument 0 to keep API compatibility.
 278  */
 279 #define alternative_input(oldinstr, newinstr, ft_flags, input...)       \
 280         asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags)  \
 281                 : : "i" (0), ## input)
 282
 283 /*
 284  * This is similar to alternative_input. But it has two features and
 285  * respective instructions.
 286  *
 287  * If CPU has feature2, newinstr2 is used.
 288  * Otherwise, if CPU has feature1, newinstr1 is used.
 289  * Otherwise, oldinstr is used.
 290  */
 291 #define alternative_input_2(oldinstr, newinstr1, ft_flags1, newinstr2,       \
 292                            ft_flags2, input...)                              \
 293         asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1,     \
 294                 newinstr2, ft_flags2)                                        \
 295                 : : "i" (0), ## input)
 296
 297 /* Like alternative_input, but with a single output argument */
 298 #define alternative_io(oldinstr, newinstr, ft_flags, output, input...)  \
 299         asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags)  \
 300                 : output : "i" (0), ## input)
 301
 302 /* Like alternative_io, but for replacing a direct call with another one. */
 303 #define alternative_call(oldfunc, newfunc, ft_flags, output, input...)  \
 304         asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
 305                 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
 306
 307 /*
 308  * Like alternative_call, but there are two features and respective functions.
 309  * If CPU has feature2, function2 is used.
 310  * Otherwise, if CPU has feature1, function1 is used.
 311  * Otherwise, old function is used.
 312  */
 313 #define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2,   \
 314                            output, input...)                                  \
 315         asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,\
 316                 "call %P[new2]", ft_flags2)                                   \
 317                 : output, ASM_CALL_CONSTRAINT                                 \
 318                 : [old] "i" (oldfunc), [new1] "i" (newfunc1),                 \
 319                   [new2] "i" (newfunc2), ## input)
 320
 321 /*
 322  * use this macro(s) if you need more than one output parameter
 323  * in alternative_io
 324  */
 325 #define ASM_OUTPUT2(a...) a
 326
 327 /*
 328  * use this macro if you need clobbers but no inputs in
 329  * alternative_{input,io,call}()
 330  */
 331 #define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
 332
 333 #else /* __ASSEMBLY__ */
 334
 335 #ifdef CONFIG_SMP
 336         .macro LOCK_PREFIX
 337 672:    lock
 338         .pushsection .smp_locks,"a"
 339         .balign 4
 340         .long 672b - .
 341         .popsection
 342         .endm
 343 #else
 344         .macro LOCK_PREFIX
 345         .endm
 346 #endif
 347
 348 /*
 349  * objtool annotation to ignore the alternatives and only consider the original
 350  * instruction(s).
 351  */
 352 .macro ANNOTATE_IGNORE_ALTERNATIVE
 353         .Lannotate_\@:
 354         .pushsection .discard.ignore_alts
 355         .long .Lannotate_\@ - .
 356         .popsection
 357 .endm
 358
 359 /*
 360  * Issue one struct alt_instr descriptor entry (need to put it into
 361  * the section .altinstructions, see below). This entry contains
 362  * enough information for the alternatives patching code to patch an
 363  * instruction. See apply_alternatives().
 364  */
 365 .macro altinstr_entry orig alt ft_flags orig_len alt_len
 366         .long \orig - .
 367         .long \alt - .
 368         .4byte \ft_flags
 369         .byte \orig_len
 370         .byte \alt_len
 371 .endm
 372
 373 /*
 374  * Define an alternative between two instructions. If @feature is
 375  * present, early code in apply_alternatives() replaces @oldinstr with
 376  * @newinstr. ".skip" directive takes care of proper instruction padding
 377  * in case @newinstr is longer than @oldinstr.
 378  */
 379 .macro ALTERNATIVE oldinstr, newinstr, ft_flags
 380 140:
 381         \oldinstr
 382 141:
 383         .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
 384 142:
 385
 386         .pushsection .altinstructions,"a"
 387         altinstr_entry 140b,143f,\ft_flags,142b-140b,144f-143f
 388         .popsection
 389
 390         .pushsection .altinstr_replacement,"ax"
 391 143:
 392         \newinstr
 393 144:
 394         .popsection
 395 .endm
 396
 397 #define old_len                 141b-140b
 398 #define new_len1                144f-143f
 399 #define new_len2                145f-144f
 400 #define new_len3                146f-145f
 401
 402 /*
 403  * gas compatible max based on the idea from:
 404  * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
 405  *
 406  * The additional "-" is needed because gas uses a "true" value of -1.
 407  */
 408 #define alt_max_2(a, b)         ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
 409 #define alt_max_3(a, b, c)      (alt_max_2(alt_max_2(a, b), c))
 410
 411
 412 /*
 413  * Same as ALTERNATIVE macro above but for two alternatives. If CPU
 414  * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
 415  * @feature2, it replaces @oldinstr with @feature2.
 416  */
 417 .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
 418 140:
 419         \oldinstr
 420 141:
 421         .skip -((alt_max_2(new_len1, new_len2) - (old_len)) > 0) * \
 422                 (alt_max_2(new_len1, new_len2) - (old_len)),0x90
 423 142:
 424
 425         .pushsection .altinstructions,"a"
 426         altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
 427         altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
 428         .popsection
 429
 430         .pushsection .altinstr_replacement,"ax"
 431 143:
 432         \newinstr1
 433 144:
 434         \newinstr2
 435 145:
 436         .popsection
 437 .endm
 438
 439 .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
 440 140:
 441         \oldinstr
 442 141:
 443         .skip -((alt_max_3(new_len1, new_len2, new_len3) - (old_len)) > 0) * \
 444                 (alt_max_3(new_len1, new_len2, new_len3) - (old_len)),0x90
 445 142:
 446
 447         .pushsection .altinstructions,"a"
 448         altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
 449         altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
 450         altinstr_entry 140b,145f,\ft_flags3,142b-140b,146f-145f
 451         .popsection
 452
 453         .pushsection .altinstr_replacement,"ax"
 454 143:
 455         \newinstr1
 456 144:
 457         \newinstr2
 458 145:
 459         \newinstr3
 460 146:
 461         .popsection
 462 .endm
 463
 464 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
 465 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
 466         ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS,        \
 467         newinstr_yes, ft_flags
 468
 469 #endif /* __ASSEMBLY__ */
 470
 471 #endif /* _ASM_X86_ALTERNATIVE_H */