include/libc-symbols.h

   1 /* Support macros for making weak and strong aliases for symbols,
   2    and for using symbol sets and linker warnings with GNU ld.
   3    Copyright (C) 1995-2023 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #ifndef _LIBC_SYMBOLS_H
  21 #define _LIBC_SYMBOLS_H 1
  22
  23 /* This file is included implicitly in the compilation of every source file,
  24    using -include.  It includes config.h.  */
  25
  26 /* Enable declarations of GNU extensions, since we are compiling them.  */
  27 #define _GNU_SOURCE 1
  28
  29 #ifdef MODULE_NAME
  30
  31 /* Use `#if IS_IN (module)` to detect what component is being compiled.  */
  32 #define PASTE_NAME1(a,b) a##b
  33 #define PASTE_NAME(a,b)  PASTE_NAME1 (a,b)
  34 #define IN_MODULE        PASTE_NAME (MODULE_, MODULE_NAME)
  35 #define IS_IN(lib)       (IN_MODULE == MODULE_##lib)
  36
  37 /* True if the current module is a versioned library.  Versioned
  38    library names culled from shlib-versions files are assigned a
  39    MODULE_* value greater than MODULE_LIBS_BEGIN.  */
  40 #define IS_IN_LIB        (IN_MODULE > MODULE_LIBS_BEGIN)
  41
  42 /* The testsuite, and some other ancillary code, should be compiled against
  43    as close an approximation to the installed headers as possible.
  44    Defining this symbol disables most internal-use-only declarations
  45    provided by this header, and all those provided by other internal
  46    wrapper headers.  */
  47 #if IS_IN (testsuite) || defined IS_IN_build || defined __cplusplus
  48 # define _ISOMAC 1
  49 #endif
  50
  51 #else
  52 /* The generation process for a few files created very early in the
  53    build (notably libc-modules.h itself) involves preprocessing this
  54    header without defining MODULE_NAME.  Under these conditions,
  55    internal declarations (especially from config.h) must be visible,
  56    but IS_IN should always evaluate as false.  */
  57 # define IS_IN(lib) 0
  58 # define IS_IN_LIB 0
  59 # define IN_MODULE (-1)
  60 #endif
  61
  62 #ifndef _ISOMAC
  63
  64 /* This is defined for the compilation of all C library code.  features.h
  65    tests this to avoid inclusion of stubs.h while compiling the library,
  66    before stubs.h has been generated.  Some library code that is shared
  67    with other packages also tests this symbol to see if it is being
  68    compiled as part of the C library.  We must define this before including
  69    config.h, because it makes some definitions conditional on whether libc
  70    itself is being compiled, or just some generator program.  */
  71 #define _LIBC   1
  72
  73 /* Some files must be compiled with optimization on.  */
  74 #if !defined __ASSEMBLER__ && !defined __OPTIMIZE__
  75 # error "glibc cannot be compiled without optimization"
  76 #endif
  77
  78 /* -ffast-math cannot be applied to the C library, as it alters the ABI.
  79    Some test components that use -ffast-math are currently not part of
  80    IS_IN (testsuite) for technical reasons, so we have a secondary override.  */
  81 #if defined __FAST_MATH__ && !defined TEST_FAST_MATH
  82 # error "glibc must not be compiled with -ffast-math"
  83 #endif
  84
  85 #include <config.h>
  86
  87 /* Obtain the definition of symbol_version_reference.  */
  88 #include <libc-symver.h>
  89
  90 /* When PIC is defined and SHARED isn't defined, we are building PIE
  91    by default.  */
  92 #if defined PIC && !defined SHARED
  93 # define BUILD_PIE_DEFAULT 1
  94 #else
  95 # define BUILD_PIE_DEFAULT 0
  96 #endif
  97
  98 /* Define this for the benefit of portable GNU code that wants to check it.
  99    Code that checks with #if will not #include <config.h> again, since we've
 100    already done it (and this file is implicitly included in every compile,
 101    via -include).  Code that checks with #ifdef will #include <config.h>,
 102    but that file should always be idempotent (i.e., it's just #define/#undef
 103    and nothing else anywhere should be changing the macro state it touches),
 104    so it's harmless.  */
 105 #define HAVE_CONFIG_H   0
 106
 107 /* Define these macros for the benefit of portable GNU code that wants to check
 108    them.  Of course, STDC_HEADERS is never false when building libc!  */
 109 #define STDC_HEADERS    1
 110 #define HAVE_MBSTATE_T  1
 111 #define HAVE_MBSRTOWCS  1
 112 #define HAVE_LIBINTL_H  1
 113 #define HAVE_WCTYPE_H   1
 114 #define HAVE_ISWCTYPE   1
 115 #define ENABLE_NLS      1
 116
 117 /* The symbols in all the user (non-_) macros are C symbols.  */
 118
 119 #ifndef __SYMBOL_PREFIX
 120 # define __SYMBOL_PREFIX
 121 #endif
 122
 123 #ifndef C_SYMBOL_NAME
 124 # define C_SYMBOL_NAME(name) name
 125 #endif
 126
 127 #ifndef ASM_LINE_SEP
 128 # define ASM_LINE_SEP ;
 129 #endif
 130
 131 #ifndef __attribute_copy__
 132 /* Provide an empty definition when cdefs.h is not included.  */
 133 # define __attribute_copy__(arg)
 134 #endif
 135
 136 #ifndef __ASSEMBLER__
 137 /* GCC understands weak symbols and aliases; use its interface where
 138    possible, instead of embedded assembly language.  */
 139
 140 /* Define ALIASNAME as a strong alias for NAME.  */
 141 # define strong_alias(name, aliasname) _strong_alias(name, aliasname)
 142 # define _strong_alias(name, aliasname) \
 143   extern __typeof (name) aliasname __attribute__ ((alias (#name))) \
 144     __attribute_copy__ (name);
 145
 146 /* This comes between the return type and function name in
 147    a function definition to make that definition weak.  */
 148 # define weak_function __attribute__ ((weak))
 149 # define weak_const_function __attribute__ ((weak, __const__))
 150
 151 /* Define ALIASNAME as a weak alias for NAME.
 152    If weak aliases are not available, this defines a strong alias.  */
 153 # define weak_alias(name, aliasname) _weak_alias (name, aliasname)
 154 # define _weak_alias(name, aliasname) \
 155   extern __typeof (name) aliasname __attribute__ ((weak, alias (#name))) \
 156     __attribute_copy__ (name);
 157
 158 /* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined).  */
 159 # define weak_extern(symbol) _weak_extern (weak symbol)
 160 # define _weak_extern(expr) _Pragma (#expr)
 161
 162 /* In shared builds, the expression call_function_static_weak
 163    (FUNCTION-SYMBOL, ARGUMENTS) invokes FUNCTION-SYMBOL (an
 164    identifier) unconditionally, with the (potentially empty) argument
 165    list ARGUMENTS.  In static builds, if FUNCTION-SYMBOL has a
 166    definition, the function is invoked as before; if FUNCTION-SYMBOL
 167    is NULL, no call is performed.  */
 168 # ifdef SHARED
 169 #  define call_function_static_weak(func, ...) func (__VA_ARGS__)
 170 # else  /* !SHARED */
 171 #  define call_function_static_weak(func, ...)          \
 172   ({                                                    \
 173     extern __typeof__ (func) func weak_function;        \
 174     (func != NULL ? func (__VA_ARGS__) : (void)0);      \
 175   })
 176 # endif
 177
 178 #else /* __ASSEMBLER__ */
 179
 180 # ifdef HAVE_ASM_SET_DIRECTIVE
 181 #  define strong_alias(original, alias)                         \
 182   .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP             \
 183   .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
 184 #  define strong_data_alias(original, alias) strong_alias(original, alias)
 185 # else
 186 #  define strong_alias(original, alias)                         \
 187   .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP             \
 188   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 189 #  define strong_data_alias(original, alias) strong_alias(original, alias)
 190 # endif
 191
 192 # define weak_alias(original, alias)                                    \
 193   .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP                              \
 194   C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
 195
 196 # define weak_extern(symbol)                                            \
 197   .weak C_SYMBOL_NAME (symbol)
 198
 199 #endif /* __ASSEMBLER__ */
 200
 201 /* Determine the return address.  */
 202 #define RETURN_ADDRESS(nr) \
 203   __builtin_extract_return_addr (__builtin_return_address (nr))
 204
 205 /* When a reference to SYMBOL is encountered, the linker will emit a
 206    warning message MSG.  */
 207 /* We want the .gnu.warning.SYMBOL section to be unallocated.  */
 208 #define __make_section_unallocated(section_string)      \
 209   asm (".section " section_string "\n\t.previous");
 210
 211 /* Tacking on "\n\t#" to the section name makes gcc put it's bogus
 212    section attributes on what looks like a comment to the assembler.  */
 213 #ifdef HAVE_SECTION_QUOTES
 214 # define __sec_comment "\"\n\t#\""
 215 #else
 216 # define __sec_comment "\n\t#"
 217 #endif
 218 #define link_warning(symbol, msg) \
 219   __make_section_unallocated (".gnu.warning." #symbol) \
 220   static const char __evoke_link_warning_##symbol[]     \
 221     __attribute__ ((used, section (".gnu.warning." #symbol __sec_comment))) \
 222     = msg;
 223
 224 /* A canned warning for sysdeps/stub functions.  */
 225 #define stub_warning(name) \
 226   __make_section_unallocated (".gnu.glibc-stub." #name) \
 227   link_warning (name, #name " is not implemented and will always fail")
 228
 229 /* Warning for linking functions calling dlopen into static binaries.  */
 230 #ifdef SHARED
 231 #define static_link_warning(name)
 232 #else
 233 #define static_link_warning(name) static_link_warning1(name)
 234 #define static_link_warning1(name) \
 235   link_warning(name, "Using '" #name "' in statically linked applications \
 236 requires at runtime the shared libraries from the glibc version used \
 237 for linking")
 238 #endif
 239
 240 /* Resource Freeing Hooks:
 241
 242    Normally a process exits and the OS cleans up any allocated
 243    memory.  However, when tooling like mtrace or valgrind is monitoring
 244    the process we need to free all resources that are part of the
 245    process in order to provide the consistency required to track
 246    memory leaks.
 247
 248    A single public API exists and is __libc_freeres(), and this is used
 249    by applications like valgrind to freee resouces.
 250
 251    There are 3 cases:
 252
 253    (a) __libc_freeres
 254
 255         In this case all you need to do is define the freeing routine:
 256
 257         foo.c:
 258         libfoo_freeres_fn (foo_freeres)
 259         {
 260           complex_free (mem);
 261         }
 262
 263         This ensures the function is called at the right point to free
 264         resources.
 265
 266    (b) __libc_freeres_ptr
 267
 268         The framework for (a) iterates over the list of pointers-to-free
 269         in (b) and frees them.
 270
 271         foo.c:
 272         libc_freeres_ptr (static char *foo_buffer);
 273
 274         Freeing these resources alaways happens last and is equivalent
 275         to registering a function that does 'free (foo_buffer)'.
 276
 277    (c) Explicit lists of free routines to call or objects to free.
 278
 279         It is the intended goal to remove (a) and (b) which have some
 280         non-determinism based on link order, and instead use explicit
 281         lists of functions and frees to resolve cleanup ordering issues
 282         and make it easy to debug and maintain.
 283
 284         As of today the following subsystems use (c):
 285
 286         Per-thread cleanup:
 287         * malloc/thread-freeres.c
 288
 289         libdl cleanup:
 290         * dlfcn/dlfreeres.c
 291
 292         libpthread cleanup:
 293         * nptl/nptlfreeres.c
 294
 295         So if you need any shutdown routines to run you should add them
 296         directly to the appropriate subsystem's shutdown list.  */
 297
 298 /* Resource pointers to free in libc.so.  */
 299 #define libc_freeres_ptr(decl) \
 300   __make_section_unallocated ("__libc_freeres_ptrs, \"aw\", %nobits") \
 301   decl __attribute__ ((section ("__libc_freeres_ptrs" __sec_comment)))
 302
 303 /* Resource freeing functions from libc.so go in this section.  */
 304 #define __libc_freeres_fn_section \
 305   __attribute__ ((__used__, section ("__libc_freeres_fn")))
 306
 307 /* Resource freeing functions for libc.so.  */
 308 #define libc_freeres_fn(name) \
 309   static void name (void) __attribute_used__ __libc_freeres_fn_section; \
 310   text_set_element (__libc_subfreeres, name);                           \
 311   static void name (void)
 312
 313 /* Declare SYMBOL to be TYPE (`function' or `object') of SIZE bytes
 314    alias to ORIGINAL, when the assembler supports such declarations
 315    (such as in ELF).
 316    This is only necessary when defining something in assembly, or playing
 317    funny alias games where the size should be other than what the compiler
 318    thinks it is.  */
 319 #ifdef __ASSEMBLER__
 320 # define declare_object_symbol_alias(symbol, original, size) \
 321   declare_object_symbol_alias_1 (symbol, original, size)
 322 # define declare_object_symbol_alias_1(symbol, original, s_size) \
 323    strong_alias (original, symbol) ASM_LINE_SEP \
 324    .type C_SYMBOL_NAME (symbol), %object ASM_LINE_SEP \
 325    .size C_SYMBOL_NAME (symbol), s_size ASM_LINE_SEP
 326 #else /* Not __ASSEMBLER__.  */
 327 # ifdef HAVE_ASM_SET_DIRECTIVE
 328 #  define declare_symbol_alias_1_alias(symbol, original) \
 329      ".set " __SYMBOL_PREFIX #symbol ", " __SYMBOL_PREFIX #original
 330 # else
 331 #  define declare_symbol_alias_1_alias(symbol, original) \
 332      __SYMBOL_PREFIX #symbol " = " __SYMBOL_PREFIX #original
 333 # endif /* HAVE_ASM_SET_DIRECTIVE */
 334 #endif /* __ASSEMBLER__ */
 335
 336
 337 /*
 338 \f
 339 */
 340
 341 #ifdef HAVE_GNU_RETAIN
 342 # define attribute_used_retain __attribute__ ((__used__, __retain__))
 343 #else
 344 # define attribute_used_retain __attribute__ ((__used__))
 345 #endif
 346
 347 /* Symbol set support macros.  */
 348
 349 /* Make SYMBOL, which is in the text segment, an element of SET.  */
 350 #define text_set_element(set, symbol)   _elf_set_element(set, symbol)
 351 /* Make SYMBOL, which is in the data segment, an element of SET.  */
 352 #define data_set_element(set, symbol)   _elf_set_element(set, symbol)
 353 /* Make SYMBOL, which is in the bss segment, an element of SET.  */
 354 #define bss_set_element(set, symbol)    _elf_set_element(set, symbol)
 355
 356 /* These are all done the same way in ELF.
 357    There is a new section created for each set.  */
 358 #ifdef SHARED
 359 /* When building a shared library, make the set section writable,
 360    because it will need to be relocated at run time anyway.  */
 361 # define _elf_set_element(set, symbol) \
 362     static const void *__elf_set_##set##_element_##symbol##__ \
 363       attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
 364 #else
 365 # define _elf_set_element(set, symbol) \
 366     static const void *const __elf_set_##set##_element_##symbol##__ \
 367       attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
 368 #endif
 369
 370 /* Define SET as a symbol set.  This may be required (it is in a.out) to
 371    be able to use the set's contents.  */
 372 #define symbol_set_define(set)  symbol_set_declare(set)
 373
 374 /* Declare SET for use in this module, if defined in another module.
 375    In a shared library, this is always local to that shared object.
 376    For static linking, the set might be wholly absent and so we use
 377    weak references.  */
 378 #define symbol_set_declare(set) \
 379   extern char const __start_##set[] __symbol_set_attribute; \
 380   extern char const __stop_##set[] __symbol_set_attribute;
 381 #ifdef SHARED
 382 # define __symbol_set_attribute attribute_hidden
 383 #else
 384 # define __symbol_set_attribute __attribute__ ((weak))
 385 #endif
 386
 387 /* Return a pointer (void *const *) to the first element of SET.  */
 388 #define symbol_set_first_element(set)   ((void *const *) (&__start_##set))
 389
 390 /* Return true iff PTR (a void *const *) has been incremented
 391    past the last element in SET.  */
 392 #define symbol_set_end_p(set, ptr) ((ptr) >= (void *const *) &__stop_##set)
 393
 394 #ifdef SHARED
 395 # define symbol_version(real, name, version) \
 396   symbol_version_reference(real, name, version)
 397 # define default_symbol_version(real, name, version) \
 398      _default_symbol_version(real, name, version)
 399 /* See <libc-symver.h>.  */
 400 # ifdef __ASSEMBLER__
 401 #  define _default_symbol_version(real, name, version) \
 402   _set_symbol_version (real, name@@version)
 403 # else
 404 #  define _default_symbol_version(real, name, version) \
 405   _set_symbol_version (real, #name "@@" #version)
 406 # endif
 407
 408 /* Evalutes to a string literal for VERSION in LIB.  */
 409 # define symbol_version_string(lib, version) \
 410   _symbol_version_stringify_1 (VERSION_##lib##_##version)
 411 # define _symbol_version_stringify_1(arg) _symbol_version_stringify_2 (arg)
 412 # define _symbol_version_stringify_2(arg) #arg
 413
 414 #else /* !SHARED */
 415 # define symbol_version(real, name, version)
 416 # define default_symbol_version(real, name, version) \
 417   strong_alias(real, name)
 418 #endif
 419
 420 #if defined SHARED || defined LIBC_NONSHARED \
 421   || (BUILD_PIE_DEFAULT && IS_IN (libc))
 422 # define attribute_hidden __attribute__ ((visibility ("hidden")))
 423 #else
 424 # define attribute_hidden
 425 #endif
 426
 427 #define attribute_tls_model_ie __attribute__ ((tls_model ("initial-exec")))
 428
 429 #define attribute_relro __attribute__ ((section (".data.rel.ro")))
 430
 431
 432 /* Used to disable stack protection in sensitive places, like ifunc
 433    resolvers and early static TLS init.  */
 434 #ifdef HAVE_CC_NO_STACK_PROTECTOR
 435 # define inhibit_stack_protector \
 436     __attribute__ ((__optimize__ ("-fno-stack-protector")))
 437 #else
 438 # define inhibit_stack_protector
 439 #endif
 440
 441 /* The following macros are used for PLT bypassing within libc.so
 442    (and if needed other libraries similarly).
 443    First of all, you need to have the function prototyped somewhere,
 444    say in foo/foo.h:
 445
 446    int foo (int __bar);
 447
 448    If calls to foo within libc.so should always go to foo defined in libc.so,
 449    then in include/foo.h you add:
 450
 451    libc_hidden_proto (foo)
 452
 453    line and after the foo function definition:
 454
 455    int foo (int __bar)
 456    {
 457      return __bar;
 458    }
 459    libc_hidden_def (foo)
 460
 461    or
 462
 463    int foo (int __bar)
 464    {
 465      return __bar;
 466    }
 467    libc_hidden_weak (foo)
 468
 469    Similarly for global data.  If references to foo within libc.so should
 470    always go to foo defined in libc.so, then in include/foo.h you add:
 471
 472    libc_hidden_proto (foo)
 473
 474    line and after foo's definition:
 475
 476    int foo = INITIAL_FOO_VALUE;
 477    libc_hidden_data_def (foo)
 478
 479    or
 480
 481    int foo = INITIAL_FOO_VALUE;
 482    libc_hidden_data_weak (foo)
 483
 484    If foo is normally just an alias (strong or weak) to some other function,
 485    you should use the normal strong_alias first, then add libc_hidden_def
 486    or libc_hidden_weak:
 487
 488    int baz (int __bar)
 489    {
 490      return __bar;
 491    }
 492    strong_alias (baz, foo)
 493    libc_hidden_weak (foo)
 494
 495    If the function should be internal to multiple objects, say ld.so and
 496    libc.so, the best way is to use:
 497
 498    #if IS_IN (libc) || IS_IN (rtld)
 499    hidden_proto (foo)
 500    #endif
 501
 502    in include/foo.h and the normal macros at all function definitions
 503    depending on what DSO they belong to.
 504
 505    If versioned_symbol macro is used to define foo,
 506    libc_hidden_ver macro should be used, as in:
 507
 508    int __real_foo (int __bar)
 509    {
 510      return __bar;
 511    }
 512    versioned_symbol (libc, __real_foo, foo, GLIBC_2_1);
 513    libc_hidden_ver (__real_foo, foo)  */
 514
 515 #if defined SHARED && !defined NO_HIDDEN
 516 # ifndef __ASSEMBLER__
 517 #  define __hidden_proto_hiddenattr(attrs...) \
 518   __attribute__ ((visibility ("hidden"), ##attrs))
 519 #  define hidden_proto(name, attrs...) \
 520   __hidden_proto (name, , __GI_##name, ##attrs)
 521 #  define hidden_proto_alias(name, alias, attrs...) \
 522   __hidden_proto_alias (name, , alias, ##attrs)
 523 #  define hidden_tls_proto(name, attrs...) \
 524   __hidden_proto (name, __thread, __GI_##name, ##attrs)
 525 #  define __hidden_proto(name, thread, internal, attrs...)           \
 526   extern thread __typeof (name) name __asm__ (__hidden_asmname (#internal)) \
 527   __hidden_proto_hiddenattr (attrs);
 528 #  define __hidden_proto_alias(name, thread, internal, attrs...)             \
 529   extern thread __typeof (name) internal __hidden_proto_hiddenattr (attrs);
 530 #  define __hidden_asmname(name) \
 531   __hidden_asmname1 (__USER_LABEL_PREFIX__, name)
 532 #  define __hidden_asmname1(prefix, name) __hidden_asmname2(prefix, name)
 533 #  define __hidden_asmname2(prefix, name) #prefix name
 534 #  define __hidden_ver1(local, internal, name) \
 535   __hidden_ver2 (, local, internal, name)
 536 #  define __hidden_ver2(thread, local, internal, name)                  \
 537   extern thread __typeof (name) __EI_##name \
 538     __asm__(__hidden_asmname (#internal));  \
 539   extern thread __typeof (name) __EI_##name \
 540     __attribute__((alias (__hidden_asmname (#local))))  \
 541     __attribute_copy__ (name)
 542 #  define hidden_ver(local, name)       __hidden_ver1(local, __GI_##name, name);
 543 #  define hidden_def(name)              __hidden_ver1(__GI_##name, name, name);
 544 #  define hidden_def_alias(name, internal) \
 545   strong_alias (name, internal)
 546 #  define hidden_data_def(name)         hidden_def(name)
 547 #  define hidden_data_def_alias(name, alias) hidden_def_alias(name, alias)
 548 #  define hidden_tls_def(name)                          \
 549   __hidden_ver2 (__thread, __GI_##name, name, name);
 550 #  define hidden_weak(name) \
 551         __hidden_ver1(__GI_##name, name, name) __attribute__((weak));
 552 #  define hidden_data_weak(name)        hidden_weak(name)
 553 #  define hidden_nolink(name, lib, version) \
 554   __hidden_nolink1 (__GI_##name, __EI_##name, name, VERSION_##lib##_##version)
 555 #  define __hidden_nolink1(local, internal, name, version) \
 556   __hidden_nolink2 (local, internal, name, version)
 557 #  define __hidden_nolink2(local, internal, name, version) \
 558   extern __typeof (name) internal __attribute__ ((alias (#local)))      \
 559     __attribute_copy__ (name);                                          \
 560   __hidden_nolink3 (local, internal, #name "@" #version)
 561 #  define __hidden_nolink3(local, internal, vername) \
 562   __asm__ (".symver " #internal ", " vername);
 563 # else
 564 /* For assembly, we need to do the opposite of what we do in C:
 565    in assembly gcc __REDIRECT stuff is not in place, so functions
 566    are defined by its normal name and we need to create the
 567    __GI_* alias to it, in C __REDIRECT causes the function definition
 568    to use __GI_* name and we need to add alias to the real name.
 569    There is no reason to use hidden_weak over hidden_def in assembly,
 570    but we provide it for consistency with the C usage.
 571    hidden_proto doesn't make sense for assembly but the equivalent
 572    is to call via the HIDDEN_JUMPTARGET macro instead of JUMPTARGET.  */
 573 #  define hidden_def(name)      strong_alias (name, __GI_##name)
 574 #  define hidden_def_alias(name, alias) strong_alias (name, alias)
 575 #  define hidden_weak(name)     hidden_def (name)
 576 #  define hidden_ver(local, name) strong_alias (local, __GI_##name)
 577 #  define hidden_data_def(name) strong_data_alias (name, __GI_##name)
 578 #  define hidden_data_def_alias(name, alias) strong_data_alias (name, alias)
 579 #  define hidden_tls_def(name)  hidden_data_def (name)
 580 #  define hidden_data_weak(name)        hidden_data_def (name)
 581 #  define HIDDEN_JUMPTARGET(name) __GI_##name
 582 # endif
 583 #else
 584 # ifndef __ASSEMBLER__
 585 #  if !defined SHARED && IS_IN (libc) && !defined LIBC_NONSHARED \
 586       && (!defined PIC || !defined NO_HIDDEN_EXTERN_FUNC_IN_PIE) \
 587       && !defined NO_HIDDEN
 588 #   define __hidden_proto_hiddenattr(attrs...) \
 589   __attribute__ ((visibility ("hidden"), ##attrs))
 590 #   define hidden_proto(name, attrs...) \
 591   __hidden_proto (name, , name, ##attrs)
 592 #  define hidden_proto_alias(name, alias, attrs...) \
 593   __hidden_proto_alias (name, , alias, ##attrs)
 594 #   define hidden_tls_proto(name, attrs...) \
 595   __hidden_proto (name, __thread, name, ##attrs)
 596 #  define __hidden_proto(name, thread, internal, attrs...)           \
 597   extern thread __typeof (name) name __hidden_proto_hiddenattr (attrs);
 598 #  define __hidden_proto_alias(name, thread, internal, attrs...)     \
 599   extern thread __typeof (name) internal __hidden_proto_hiddenattr (attrs);
 600 # else
 601 #   define hidden_proto(name, attrs...)
 602 #   define hidden_proto_alias(name, alias, attrs...)
 603 #   define hidden_tls_proto(name, attrs...)
 604 # endif
 605 # else
 606 #  define HIDDEN_JUMPTARGET(name) JUMPTARGET(name)
 607 # endif /* Not  __ASSEMBLER__ */
 608 # define hidden_weak(name)
 609 # define hidden_def(name)
 610 # define hidden_def_alias(name, alias)
 611 # define hidden_ver(local, name)
 612 # define hidden_data_weak(name)
 613 # define hidden_data_def(name)
 614 # define hidden_data_def_alias(name, alias)
 615 # define hidden_tls_def(name)
 616 # define hidden_nolink(name, lib, version)
 617 #endif
 618
 619 #if IS_IN (libc)
 620 # define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 621 # define libc_hidden_proto_alias(name, alias, attrs...) \
 622    hidden_proto_alias (name, alias, ##attrs)
 623 # define libc_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
 624 # define libc_hidden_def(name) hidden_def (name)
 625 # define libc_hidden_weak(name) hidden_weak (name)
 626 # define libc_hidden_nolink_sunrpc(name, version) hidden_nolink (name, libc, version)
 627 # define libc_hidden_ver(local, name) hidden_ver (local, name)
 628 # define libc_hidden_data_def(name) hidden_data_def (name)
 629 # define libc_hidden_data_def_alias(name, alias) hidden_data_def_alias (name, alias)
 630 # define libc_hidden_tls_def(name) hidden_tls_def (name)
 631 # define libc_hidden_data_weak(name) hidden_data_weak (name)
 632 #else
 633 # define libc_hidden_proto(name, attrs...)
 634 # define libc_hidden_proto_alias(name, alias, attrs...)
 635 # define libc_hidden_tls_proto(name, attrs...)
 636 # define libc_hidden_def(name)
 637 # define libc_hidden_weak(name)
 638 # define libc_hidden_ver(local, name)
 639 # define libc_hidden_data_def(name)
 640 # define libc_hidden_data_def_alias(name, alias)
 641 # define libc_hidden_tls_def(name)
 642 # define libc_hidden_data_weak(name)
 643 #endif
 644
 645 #if IS_IN (rtld)
 646 # define rtld_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 647 # define rtld_hidden_def(name) hidden_def (name)
 648 # define rtld_hidden_weak(name) hidden_weak (name)
 649 # define rtld_hidden_data_def(name) hidden_data_def (name)
 650 #else
 651 # define rtld_hidden_proto(name, attrs...)
 652 # define rtld_hidden_def(name)
 653 # define rtld_hidden_weak(name)
 654 # define rtld_hidden_data_def(name)
 655 #endif
 656
 657 #if IS_IN (libm)
 658 # define libm_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 659 # define libm_hidden_def(name) hidden_def (name)
 660 # define libm_hidden_weak(name) hidden_weak (name)
 661 # define libm_hidden_ver(local, name) hidden_ver (local, name)
 662 #else
 663 # define libm_hidden_proto(name, attrs...)
 664 # define libm_hidden_def(name)
 665 # define libm_hidden_weak(name)
 666 # define libm_hidden_ver(local, name)
 667 #endif
 668
 669 #if IS_IN (libmvec)
 670 # define libmvec_hidden_def(name) hidden_def (name)
 671 #else
 672 # define libmvec_hidden_def(name)
 673 #endif
 674
 675 #if IS_IN (libresolv)
 676 # define libresolv_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 677 # define libresolv_hidden_def(name) hidden_def (name)
 678 # define libresolv_hidden_data_def(name) hidden_data_def (name)
 679 #else
 680 # define libresolv_hidden_proto(name, attrs...)
 681 # define libresolv_hidden_def(name)
 682 # define libresolv_hidden_data_def(name)
 683 #endif
 684
 685 #if IS_IN (libpthread)
 686 # define libpthread_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 687 # define libpthread_hidden_def(name) hidden_def (name)
 688 #else
 689 # define libpthread_hidden_proto(name, attrs...)
 690 # define libpthread_hidden_def(name)
 691 #endif
 692
 693 #if IS_IN (librt)
 694 # define librt_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 695 # define librt_hidden_ver(local, name) hidden_ver (local, name)
 696 #else
 697 # define librt_hidden_proto(name, attrs...)
 698 # define librt_hidden_ver(local, name)
 699 #endif
 700
 701 #if IS_IN (libnsl)
 702 # define libnsl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 703 # define libnsl_hidden_nolink_def(name, version) hidden_nolink (name, libnsl, version)
 704 #else
 705 # define libnsl_hidden_proto(name, attrs...)
 706 #endif
 707
 708 #define libc_hidden_builtin_proto(name, attrs...) libc_hidden_proto (name, ##attrs)
 709 #define libc_hidden_builtin_def(name) libc_hidden_def (name)
 710
 711 #define libc_hidden_ldbl_proto(name, attrs...) libc_hidden_proto (name, ##attrs)
 712 #ifdef __ASSEMBLER__
 713 # define HIDDEN_BUILTIN_JUMPTARGET(name) HIDDEN_JUMPTARGET(name)
 714 #endif
 715
 716 #if IS_IN (libanl)
 717 # define libanl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 718 #else
 719 # define libanl_hidden_proto(name, attrs...)
 720 #endif
 721
 722 /* Get some dirty hacks.  */
 723 #include <symbol-hacks.h>
 724
 725 /* Move compatibility symbols out of the way by placing them all in a
 726    special section.  */
 727 #ifndef __ASSEMBLER__
 728 # define attribute_compat_text_section \
 729     __attribute__ ((section (".text.compat")))
 730 #else
 731 # define compat_text_section .section ".text.compat", "ax";
 732 #endif
 733
 734 /* Helper / base  macros for indirect function symbols.  */
 735 #define __ifunc_resolver(type_name, name, expr, arg, init, classifier)  \
 736   classifier inhibit_stack_protector                                    \
 737   __typeof (type_name) *name##_ifunc (arg)                              \
 738   {                                                                     \
 739     init ();                                                            \
 740     __typeof (type_name) *res = expr;                                   \
 741     return res;                                                         \
 742   }
 743
 744 #ifdef HAVE_GCC_IFUNC
 745 # define __ifunc(type_name, name, expr, arg, init)                      \
 746   extern __typeof (type_name) name __attribute__                        \
 747                               ((ifunc (#name "_ifunc")));               \
 748   __ifunc_resolver (type_name, name, expr, arg, init, static)
 749
 750 # define __ifunc_hidden(type_name, name, expr, arg, init)       \
 751   __ifunc (type_name, name, expr, arg, init)
 752 #else
 753 /* Gcc does not support __attribute__ ((ifunc (...))).  Use the old behaviour
 754    as fallback.  But keep in mind that the debug information for the ifunc
 755    resolver functions is not correct.  It contains the ifunc'ed function as
 756    DW_AT_linkage_name.  E.g. lldb uses this field and an inferior function
 757    call of the ifunc'ed function will fail due to "no matching function for
 758    call to ..." because the ifunc'ed function and the resolver function have
 759    different signatures.  (Gcc support is disabled at least on a ppc64le
 760    Ubuntu 14.04 system.)  */
 761
 762 # define __ifunc(type_name, name, expr, arg, init)                      \
 763   extern __typeof (type_name) name;                                     \
 764   __typeof (type_name) *name##_ifunc (arg) __asm__ (#name);             \
 765   __ifunc_resolver (type_name, name, expr, arg, init,)                  \
 766  __asm__ (".type " #name ", %gnu_indirect_function");
 767
 768 # define __ifunc_hidden(type_name, name, expr, arg, init)               \
 769   extern __typeof (type_name) __libc_##name;                            \
 770   __ifunc (type_name, __libc_##name, expr, arg, init)                   \
 771   strong_alias (__libc_##name, name);
 772 #endif /* !HAVE_GCC_IFUNC  */
 773
 774 /* The following macros are used for indirect function symbols in libc.so.
 775    First of all, you need to have the function prototyped somewhere,
 776    say in foo.h:
 777
 778    int foo (int __bar);
 779
 780    If you have an implementation for foo which e.g. uses a special hardware
 781    feature which isn't available on all machines where this libc.so will be
 782    used but decideable if available at runtime e.g. via hwcaps, you can provide
 783    two or multiple implementations of foo:
 784
 785    int __foo_default (int __bar)
 786    {
 787      return __bar;
 788    }
 789
 790    int __foo_special (int __bar)
 791    {
 792      return __bar;
 793    }
 794
 795    If your function foo has no libc_hidden_proto (foo) defined for PLT
 796    bypassing, you can use:
 797
 798    #define INIT_ARCH() unsigned long int hwcap = __GLRO(dl_hwcap);
 799
 800    libc_ifunc (foo, (hwcap & HWCAP_SPECIAL) ? __foo_special : __foo_default);
 801
 802    This will define a resolver function for foo which returns __foo_special or
 803    __foo_default depending on your specified expression.  Please note that you
 804    have to define a macro function INIT_ARCH before using libc_ifunc macro as
 805    it is called by the resolver function before evaluating the specified
 806    expression.  In this example it is used to prepare the hwcap variable.
 807    The resolver function is assigned to an ifunc'ed symbol foo.  Calls to foo
 808    from inside or outside of libc.so will be indirected by a PLT call.
 809
 810    If your function foo has a libc_hidden_proto (foo) defined for PLT bypassing
 811    and calls to foo within libc.so should always go to one specific
 812    implementation of foo e.g. __foo_default then you have to add:
 813
 814    __hidden_ver1 (__foo_default, __GI_foo, __foo_default);
 815
 816    or a tweaked definition of libc_hidden_def macro after the __foo_default
 817    function definition.  Calls to foo within libc.so will always go directly to
 818    __foo_default.  Calls to foo from outside libc.so will be indirected by a
 819    PLT call to ifunc'ed symbol foo which you have to define in a separate
 820    compile unit:
 821
 822    #define foo __redirect_foo
 823    #include <foo.h>
 824    #undef foo
 825
 826    extern __typeof (__redirect_foo) __foo_default attribute_hidden;
 827    extern __typeof (__redirect_foo) __foo_special attribute_hidden;
 828
 829    libc_ifunc_redirected (__redirect_foo, foo,
 830                           (hwcap & HWCAP_SPECIAL)
 831                           ? __foo_special
 832                           : __foo_default);
 833
 834    This will define the ifunc'ed symbol foo like above.  The redirection of foo
 835    in header file is needed to omit an additional defintion of __GI_foo which
 836    would end in a linker error while linking libc.so.  You have to specify
 837    __redirect_foo as first parameter which is used within libc_ifunc_redirected
 838    macro in conjunction with typeof to define the ifunc'ed symbol foo.
 839
 840    If your function foo has a libc_hidden_proto (foo) defined and calls to foo
 841    within or from outside libc.so should go via ifunc'ed symbol, then you have
 842    to use:
 843
 844    libc_ifunc_hidden (foo, foo,
 845                       (hwcap & HWCAP_SPECIAL)
 846                       ? __foo_special
 847                       : __foo_default);
 848    libc_hidden_def (foo)
 849
 850    The first parameter foo of libc_ifunc_hidden macro is used in the same way
 851    as for libc_ifunc_redirected macro.  */
 852
 853 #define libc_ifunc(name, expr) __ifunc (name, name, expr, void, INIT_ARCH)
 854
 855 #define libc_ifunc_redirected(redirected_name, name, expr)      \
 856   __ifunc (redirected_name, name, expr, void, INIT_ARCH)
 857
 858 #define libc_ifunc_hidden(redirected_name, name, expr)                  \
 859   __ifunc_hidden (redirected_name, name, expr, void, INIT_ARCH)
 860
 861 /* The body of the function is supposed to use __get_cpu_features
 862    which will, if necessary, initialize the data first.  */
 863 #define libm_ifunc_init()
 864 #define libm_ifunc(name, expr)                          \
 865   __ifunc (name, name, expr, void, libm_ifunc_init)
 866
 867 /* Add the compiler optimization to inhibit loop transformation to library
 868    calls.  This is used to avoid recursive calls in memset and memmove
 869    default implementations.  */
 870 #ifdef HAVE_CC_INHIBIT_LOOP_TO_LIBCALL
 871 # define inhibit_loop_to_libcall \
 872     __attribute__ ((__optimize__ ("-fno-tree-loop-distribute-patterns")))
 873 #else
 874 # define inhibit_loop_to_libcall
 875 #endif
 876 \f
 877 /* These macros facilitate sharing source files with gnulib.
 878
 879    They are here instead of sys/cdefs.h because they should not be
 880    used in public header files.
 881
 882    Their definitions should be kept consistent with the definitions in
 883    gnulib-common.m4, but it is not necessary to cater to old non-GCC
 884    compilers, since they will only be used while building glibc itself.
 885    (Note that _GNUC_PREREQ cannot be used in this file.)  */
 886
 887 /* Define as a marker that can be attached to declarations that might not
 888     be used.  This helps to reduce warnings, such as from
 889     GCC -Wunused-parameter.  */
 890 #if __GNUC__ >= 3 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 7)
 891 # define _GL_UNUSED __attribute__ ((__unused__))
 892 #else
 893 # define _GL_UNUSED
 894 #endif
 895
 896 /* gcc supports the "unused" attribute on possibly unused labels, and
 897    g++ has since version 4.5.  Note to support C++ as well as C,
 898    _GL_UNUSED_LABEL should be used with a trailing ;  */
 899 #if !defined __cplusplus || __GNUC__ > 4 \
 900     || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
 901 # define _GL_UNUSED_LABEL _GL_UNUSED
 902 #else
 903 # define _GL_UNUSED_LABEL
 904 #endif
 905
 906 /* The __pure__ attribute was added in gcc 2.96.  */
 907 #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 96)
 908 # define _GL_ATTRIBUTE_PURE __attribute__ ((__pure__))
 909 #else
 910 # define _GL_ATTRIBUTE_PURE /* empty */
 911 #endif
 912
 913 /* The __const__ attribute was added in gcc 2.95.  */
 914 #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 95)
 915 # define _GL_ATTRIBUTE_CONST __attribute__ ((__const__))
 916 #else
 917 # define _GL_ATTRIBUTE_CONST /* empty */
 918 #endif
 919
 920 #endif /* !_ISOMAC */
 921 #endif /* libc-symbols.h */