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- /* Support macros for making weak and strong aliases for symbols,
- and for using symbol sets and linker warnings with GNU ld.
- Copyright (C) 1995-2026 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
- The GNU C Library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2.1 of the License, or (at your option) any later version.
- The GNU C Library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
- You should have received a copy of the GNU Lesser General Public
- License along with the GNU C Library; if not, see
- <https://www.gnu.org/licenses/>. */
- #ifndef _LIBC_SYMBOLS_H
- #define _LIBC_SYMBOLS_H 1
- /* This file is included implicitly in the compilation of every source file,
- using -include. It includes config.h. */
- /* Enable declarations of GNU extensions, since we are compiling them. */
- #define _GNU_SOURCE 1
- #ifdef MODULE_NAME
- /* Use `#if IS_IN (module)` to detect what component is being compiled. */
- #define PASTE_NAME1(a,b) a##b
- #define PASTE_NAME(a,b) PASTE_NAME1 (a,b)
- #define IN_MODULE PASTE_NAME (MODULE_, MODULE_NAME)
- #define IS_IN(lib) (IN_MODULE == MODULE_##lib)
- /* True if the current module is a versioned library. Versioned
- library names culled from shlib-versions files are assigned a
- MODULE_* value greater than MODULE_LIBS_BEGIN. */
- #define IS_IN_LIB (IN_MODULE > MODULE_LIBS_BEGIN)
- /* The testsuite, and some other ancillary code, should be compiled against
- as close an approximation to the installed headers as possible.
- Defining this symbol disables most internal-use-only declarations
- provided by this header, and all those provided by other internal
- wrapper headers. */
- #if IS_IN (testsuite) || defined IS_IN_build || defined __cplusplus
- # define _ISOMAC 1
- #endif
- #else
- /* The generation process for a few files created very early in the
- build (notably libc-modules.h itself) involves preprocessing this
- header without defining MODULE_NAME. Under these conditions,
- internal declarations (especially from config.h) must be visible,
- but IS_IN should always evaluate as false. */
- # define IS_IN(lib) 0
- # define IS_IN_LIB 0
- # define IN_MODULE (-1)
- #endif
- #include <libc-misc.h>
- #ifndef _ISOMAC
- /* This is defined for the compilation of all C library code. features.h
- tests this to avoid inclusion of stubs.h while compiling the library,
- before stubs.h has been generated. Some library code that is shared
- with other packages also tests this symbol to see if it is being
- compiled as part of the C library. We must define this before including
- config.h, because it makes some definitions conditional on whether libc
- itself is being compiled, or just some generator program. */
- #define _LIBC 1
- /* Some files must be compiled with optimization on. */
- #if !defined __ASSEMBLER__ && !defined __OPTIMIZE__
- # error "glibc cannot be compiled without optimization"
- #endif
- /* -ffast-math cannot be applied to the C library, as it alters the ABI.
- Some test components that use -ffast-math are currently not part of
- IS_IN (testsuite) for technical reasons, so we have a secondary override. */
- #if defined __FAST_MATH__ && !defined TEST_FAST_MATH
- # error "glibc must not be compiled with -ffast-math"
- #endif
- /* Obtain the definition of symbol_version_reference. */
- #include <libc-symver.h>
- #include <libc-diag.h>
- /* When PIC is defined and SHARED isn't defined, we are building PIE
- by default. */
- #if defined PIC && !defined SHARED
- # define BUILD_PIE_DEFAULT 1
- #else
- # define BUILD_PIE_DEFAULT 0
- #endif
- /* Define this for the benefit of portable GNU code that wants to check it.
- Code that checks with #if will not #include <config.h> again, since we've
- already done it (and this file is implicitly included in every compile,
- via -include). Code that checks with #ifdef will #include <config.h>,
- but that file should always be idempotent (i.e., it's just #define/#undef
- and nothing else anywhere should be changing the macro state it touches),
- so it's harmless. */
- #define HAVE_CONFIG_H 0
- /* Define these macros for the benefit of portable GNU code that wants to check
- them. Of course, STDC_HEADERS is never false when building libc! */
- #define STDC_HEADERS 1
- #define HAVE_MBSTATE_T 1
- #define HAVE_MBSRTOWCS 1
- #define HAVE_LIBINTL_H 1
- #define HAVE_WCTYPE_H 1
- #define HAVE_ISWCTYPE 1
- #define ENABLE_NLS 1
- /* The symbols in all the user (non-_) macros are C symbols. */
- #ifndef __SYMBOL_PREFIX
- # define __SYMBOL_PREFIX
- #endif
- #ifndef C_SYMBOL_NAME
- # define C_SYMBOL_NAME(name) name
- #endif
- #ifndef ASM_LINE_SEP
- # define ASM_LINE_SEP ;
- #endif
- #ifndef __attribute_copy__
- /* Provide an empty definition when cdefs.h is not included. */
- # define __attribute_copy__(arg)
- #endif
- #ifndef __ASSEMBLER__
- /* GCC understands weak symbols and aliases; use its interface where
- possible, instead of embedded assembly language. */
- /* Define ALIASNAME as a strong alias for NAME. */
- # define strong_alias(name, aliasname) _strong_alias(name, aliasname)
- # define _strong_alias(name, aliasname) \
- extern __typeof (name) aliasname __attribute__ ((alias (#name))) \
- __attribute_copy__ (name);
- /* This comes between the return type and function name in
- a function definition to make that definition weak. */
- # define weak_function __attribute__ ((weak))
- # define weak_const_function __attribute__ ((weak, __const__))
- /* Define ALIASNAME as a weak alias for NAME.
- If weak aliases are not available, this defines a strong alias. */
- # define weak_alias(name, aliasname) _weak_alias (name, aliasname)
- # define _weak_alias(name, aliasname) \
- extern __typeof (name) aliasname __attribute__ ((weak, alias (#name))) \
- __attribute_copy__ (name);
- /* Define a strong_alias for SHARED, or weak_alias otherwise. It is used to
- avoid potential compiler warnings for weak alias indirection (when a weak
- alias is always resolved to a symbol even if a weak definition also
- exists). */
- # ifdef SHARED
- # define static_weak_alias(name, aliasname) strong_alias (name, aliasname)
- # else
- # define static_weak_alias(name, aliasname) weak_alias (name, aliasname)
- # endif
- /* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined). */
- # define weak_extern(symbol) _weak_extern (weak symbol)
- # define _weak_extern(expr) _Pragma (#expr)
- /* In shared builds, the expression call_function_static_weak
- (FUNCTION-SYMBOL, ARGUMENTS) invokes FUNCTION-SYMBOL (an
- identifier) unconditionally, with the (potentially empty) argument
- list ARGUMENTS. In static builds, if FUNCTION-SYMBOL has a
- definition, the function is invoked as before; if FUNCTION-SYMBOL
- is NULL, no call is performed. */
- # ifdef SHARED
- # define call_function_static_weak(func, ...) func (__VA_ARGS__)
- # else /* !SHARED */
- # define call_function_static_weak(func, ...) \
- ({ \
- extern __typeof__ (func) func weak_function; \
- (func != NULL ? func (__VA_ARGS__) : (void)0); \
- })
- # endif
- #else /* __ASSEMBLER__ */
- # ifdef HAVE_ASM_SET_DIRECTIVE
- # define strong_alias(original, alias) \
- .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP \
- .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
- # define strong_data_alias(original, alias) strong_alias(original, alias)
- # else
- # define strong_alias(original, alias) \
- .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP \
- C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
- # define strong_data_alias(original, alias) strong_alias(original, alias)
- # endif
- # define weak_alias(original, alias) \
- .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP \
- C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
- # define weak_extern(symbol) \
- .weak C_SYMBOL_NAME (symbol)
- #endif /* __ASSEMBLER__ */
- /* Determine the return address. */
- #define RETURN_ADDRESS(nr) \
- __builtin_extract_return_addr (__builtin_return_address (nr))
- /* When a reference to SYMBOL is encountered, the linker will emit a
- warning message MSG. */
- /* We want the .gnu.warning.SYMBOL section to be unallocated. */
- #define __make_section_unallocated(section_string) \
- asm (".section " section_string "\n\t.previous");
- /* Tacking on "\n\t#" to the section name makes gcc put its bogus
- section attributes on what looks like a comment to the assembler. */
- #ifdef HAVE_SECTION_QUOTES
- # define __sec_comment "\"\n\t#\""
- #else
- # define __sec_comment "\n\t#"
- #endif
- #define link_warning(symbol, msg) \
- __make_section_unallocated (".gnu.warning." #symbol) \
- static const char __evoke_link_warning_##symbol[] \
- __attribute__ ((used, section (".gnu.warning." #symbol __sec_comment))) \
- = msg;
- /* A canned warning for sysdeps/stub functions. */
- #define stub_warning(name) \
- __make_section_unallocated (".gnu.glibc-stub." #name) \
- link_warning (name, #name " is not implemented and will always fail")
- /* Warning for linking functions calling dlopen into static binaries. */
- #ifdef SHARED
- #define static_link_warning(name)
- #else
- #define static_link_warning(name) static_link_warning1(name)
- #define static_link_warning1(name) \
- link_warning(name, "Using '" #name "' in statically linked applications \
- requires at runtime the shared libraries from the glibc version used \
- for linking")
- #endif
- /* Declare SYMBOL to be TYPE (`function' or `object') of SIZE bytes
- alias to ORIGINAL, when the assembler supports such declarations
- (such as in ELF).
- This is only necessary when defining something in assembly, or playing
- funny alias games where the size should be other than what the compiler
- thinks it is. */
- #define declare_object_symbol_alias(symbol, original, size) \
- declare_object_symbol_alias_1 (symbol, original, size)
- #ifdef __ASSEMBLER__
- # define declare_object_symbol_alias_1(symbol, original, s_size) \
- strong_alias (original, symbol) ASM_LINE_SEP \
- .type C_SYMBOL_NAME (symbol), %object ASM_LINE_SEP \
- .size C_SYMBOL_NAME (symbol), s_size ASM_LINE_SEP
- #else /* Not __ASSEMBLER__. */
- # ifdef HAVE_ASM_SET_DIRECTIVE
- # define declare_object_symbol_alias_1(symbol, original, size) \
- asm (".global " __SYMBOL_PREFIX # symbol "\n" \
- ".type " __SYMBOL_PREFIX # symbol ", %object\n" \
- ".set " __SYMBOL_PREFIX #symbol ", " __SYMBOL_PREFIX original "\n" \
- ".size " __SYMBOL_PREFIX #symbol ", " #size "\n");
- # else
- # define declare_object_symbol_alias_1(symbol, original, size) \
- asm (".global " __SYMBOL_PREFIX # symbol "\n" \
- ".type " __SYMBOL_PREFIX # symbol ", %object\n" \
- __SYMBOL_PREFIX #symbol " = " __SYMBOL_PREFIX original "\n" \
- ".size " __SYMBOL_PREFIX #symbol ", " #size "\n");
- # endif /* HAVE_ASM_SET_DIRECTIVE */
- #endif /* __ASSEMBLER__ */
- /*
- */
- #ifdef HAVE_GNU_RETAIN
- # define attribute_used_retain __attribute__ ((__used__, __retain__))
- #else
- # define attribute_used_retain __attribute__ ((__used__))
- #endif
- /* Symbol set support macros. */
- /* Make SYMBOL, which is in the text segment, an element of SET. */
- #define text_set_element(set, symbol) _elf_set_element(set, symbol)
- /* Make SYMBOL, which is in the data segment, an element of SET. */
- #define data_set_element(set, symbol) _elf_set_element(set, symbol)
- /* Make SYMBOL, which is in the bss segment, an element of SET. */
- #define bss_set_element(set, symbol) _elf_set_element(set, symbol)
- /* These are all done the same way in ELF.
- There is a new section created for each set. */
- #ifdef SHARED
- /* When building a shared library, make the set section writable,
- because it will need to be relocated at run time anyway. */
- # define _elf_set_element(set, symbol) \
- static const void *__elf_set_##set##_element_##symbol##__ \
- attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
- #else
- # define _elf_set_element(set, symbol) \
- static const void *const __elf_set_##set##_element_##symbol##__ \
- attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
- #endif
- /* Define SET as a symbol set. This may be required (it is in a.out) to
- be able to use the set's contents. */
- #define symbol_set_define(set) symbol_set_declare(set)
- /* Declare SET for use in this module, if defined in another module.
- In a shared library, this is always local to that shared object.
- For static linking, the set might be wholly absent and so we use
- weak references. */
- #define symbol_set_declare(set) \
- extern char const __start_##set[] __symbol_set_attribute; \
- extern char const __stop_##set[] __symbol_set_attribute;
- #ifdef SHARED
- # define __symbol_set_attribute attribute_hidden
- #else
- # define __symbol_set_attribute __attribute__ ((weak))
- #endif
- /* Return a pointer (void *const *) to the first element of SET. */
- #define symbol_set_first_element(set) ((void *const *) (&__start_##set))
- /* Return true iff PTR (a void *const *) has been incremented
- past the last element in SET. */
- #define symbol_set_end_p(set, ptr) ((ptr) >= (void *const *) &__stop_##set)
- #ifdef SHARED
- # define symbol_version(real, name, version) \
- symbol_version_reference(real, name, version)
- # define default_symbol_version(real, name, version) \
- _default_symbol_version(real, name, version)
- /* See <libc-symver.h>. */
- # ifdef __ASSEMBLER__
- # define _default_symbol_version(real, name, version) \
- _set_symbol_version (real, name@@version)
- # else
- # define _default_symbol_version(real, name, version) \
- _set_symbol_version (real, #name "@@" #version)
- # endif
- /* Evaluates to a string literal for VERSION in LIB. */
- # define symbol_version_string(lib, version) \
- _symbol_version_stringify_1 (VERSION_##lib##_##version)
- # define _symbol_version_stringify_1(arg) _symbol_version_stringify_2 (arg)
- # define _symbol_version_stringify_2(arg) #arg
- #else /* !SHARED */
- # define symbol_version(real, name, version)
- # define default_symbol_version(real, name, version) \
- strong_alias(real, name)
- #endif
- #if defined SHARED || defined LIBC_NONSHARED \
- || (BUILD_PIE_DEFAULT && IS_IN (libc))
- # define attribute_hidden __attribute__ ((visibility ("hidden")))
- #else
- # define attribute_hidden
- #endif
- #define attribute_tls_model_ie __attribute__ ((tls_model ("initial-exec")))
- #define attribute_relro __attribute__ ((section (".data.rel.ro")))
- /* The following macros are used for PLT bypassing within libc.so
- (and if needed other libraries similarly).
- First of all, you need to have the function prototyped somewhere,
- say in foo/foo.h:
- int foo (int __bar);
- If calls to foo within libc.so should always go to foo defined in libc.so,
- then in include/foo.h you add:
- libc_hidden_proto (foo)
- line and after the foo function definition:
- int foo (int __bar)
- {
- return __bar;
- }
- libc_hidden_def (foo)
- or
- int foo (int __bar)
- {
- return __bar;
- }
- libc_hidden_weak (foo)
- Similarly for global data. If references to foo within libc.so should
- always go to foo defined in libc.so, then in include/foo.h you add:
- libc_hidden_proto (foo)
- line and after foo's definition:
- int foo = INITIAL_FOO_VALUE;
- libc_hidden_data_def (foo)
- or
- int foo = INITIAL_FOO_VALUE;
- libc_hidden_data_weak (foo)
- If foo is normally just an alias (strong or weak) to some other function,
- you should use the normal strong_alias first, then add libc_hidden_def
- or libc_hidden_weak:
- int baz (int __bar)
- {
- return __bar;
- }
- strong_alias (baz, foo)
- libc_hidden_weak (foo)
- If the function should be internal to multiple objects, say ld.so and
- libc.so, the best way is to use:
- #if IS_IN (libc) || IS_IN (rtld)
- hidden_proto (foo)
- #endif
- in include/foo.h and the normal macros at all function definitions
- depending on what DSO they belong to.
- If versioned_symbol macro is used to define foo,
- libc_hidden_ver macro should be used, as in:
- int __real_foo (int __bar)
- {
- return __bar;
- }
- versioned_symbol (libc, __real_foo, foo, GLIBC_2_1);
- libc_hidden_ver (__real_foo, foo) */
- #if defined SHARED && !defined NO_HIDDEN
- # ifndef __ASSEMBLER__
- # define __hidden_proto_hiddenattr(attrs...) \
- __attribute__ ((visibility ("hidden"), ##attrs))
- # define hidden_proto(name, attrs...) \
- __hidden_proto (name, , __GI_##name, ##attrs)
- # define hidden_proto_alias(name, alias, attrs...) \
- __hidden_proto_alias (name, , alias, ##attrs)
- # define hidden_tls_proto(name, attrs...) \
- __hidden_proto (name, __thread, __GI_##name, ##attrs)
- # define __hidden_proto(name, thread, internal, attrs...) \
- extern thread __typeof (name) name __asm__ (__hidden_asmname (#internal)) \
- __hidden_proto_hiddenattr (attrs);
- # define __hidden_proto_alias(name, thread, internal, attrs...) \
- extern thread __typeof (name) internal __hidden_proto_hiddenattr (attrs);
- # define __hidden_asmname(name) \
- __hidden_asmname1 (__USER_LABEL_PREFIX__, name)
- # define __hidden_asmname1(prefix, name) __hidden_asmname2(prefix, name)
- # define __hidden_asmname2(prefix, name) #prefix name
- # define __hidden_ver1(local, internal, name) \
- __hidden_ver2 (, local, internal, name)
- # define __hidden_ver2(thread, local, internal, name) \
- extern thread __typeof (name) __EI_##name \
- __asm__(__hidden_asmname (#internal)); \
- extern thread __typeof (name) __EI_##name \
- __attribute__((alias (__hidden_asmname (#local)))) \
- __attribute_copy__ (name)
- # define hidden_ver(local, name) __hidden_ver1(local, __GI_##name, name);
- # define hidden_def(name) __hidden_ver1(__GI_##name, name, name);
- # define hidden_def_alias(name, internal) \
- strong_alias (name, internal)
- # define hidden_data_def(name) hidden_def(name)
- # define hidden_data_def_alias(name, alias) hidden_def_alias(name, alias)
- # define hidden_tls_def(name) \
- __hidden_ver2 (__thread, __GI_##name, name, name);
- # define hidden_weak(name) \
- __hidden_ver1(__GI_##name, name, name) __attribute__((weak));
- # define hidden_data_weak(name) hidden_weak(name)
- # define hidden_nolink(name, lib, version) \
- __hidden_nolink1 (__GI_##name, __EI_##name, name, VERSION_##lib##_##version)
- # define __hidden_nolink1(local, internal, name, version) \
- __hidden_nolink2 (local, internal, name, version)
- # define __hidden_nolink2(local, internal, name, version) \
- extern __typeof (name) internal __attribute__ ((alias (#local))) \
- __attribute_copy__ (name); \
- __hidden_nolink3 (local, internal, #name "@" #version)
- # define __hidden_nolink3(local, internal, vername) \
- __asm__ (".symver " #internal ", " vername);
- # else
- /* For assembly, we need to do the opposite of what we do in C:
- in assembly gcc __REDIRECT stuff is not in place, so functions
- are defined by its normal name and we need to create the
- __GI_* alias to it, in C __REDIRECT causes the function definition
- to use __GI_* name and we need to add alias to the real name.
- There is no reason to use hidden_weak over hidden_def in assembly,
- but we provide it for consistency with the C usage.
- hidden_proto doesn't make sense for assembly but the equivalent
- is to call via the HIDDEN_JUMPTARGET macro instead of JUMPTARGET. */
- # define hidden_def(name) strong_alias (name, __GI_##name)
- # define hidden_def_alias(name, alias) strong_alias (name, alias)
- # define hidden_weak(name) hidden_def (name)
- # define hidden_ver(local, name) strong_alias (local, __GI_##name)
- # define hidden_data_def(name) strong_data_alias (name, __GI_##name)
- # define hidden_data_def_alias(name, alias) strong_data_alias (name, alias)
- # define hidden_tls_def(name) hidden_data_def (name)
- # define hidden_data_weak(name) hidden_data_def (name)
- # define HIDDEN_JUMPTARGET(name) __GI_##name
- # endif
- #else
- # ifndef __ASSEMBLER__
- # if !defined SHARED && IS_IN (libc) && !defined LIBC_NONSHARED \
- && (!defined PIC || !defined NO_HIDDEN_EXTERN_FUNC_IN_PIE) \
- && !defined NO_HIDDEN
- # define __hidden_proto_hiddenattr(attrs...) \
- __attribute__ ((visibility ("hidden"), ##attrs))
- # define hidden_proto(name, attrs...) \
- __hidden_proto (name, , name, ##attrs)
- # define hidden_proto_alias(name, alias, attrs...) \
- __hidden_proto_alias (name, , alias, ##attrs)
- # define hidden_tls_proto(name, attrs...) \
- __hidden_proto (name, __thread, name, ##attrs)
- # define __hidden_proto(name, thread, internal, attrs...) \
- extern thread __typeof (name) name __hidden_proto_hiddenattr (attrs);
- # define __hidden_proto_alias(name, thread, internal, attrs...) \
- extern thread __typeof (name) internal __hidden_proto_hiddenattr (attrs);
- # else
- # define hidden_proto(name, attrs...)
- # define hidden_proto_alias(name, alias, attrs...)
- # define hidden_tls_proto(name, attrs...)
- # endif
- # else
- # define HIDDEN_JUMPTARGET(name) JUMPTARGET(name)
- # endif /* Not __ASSEMBLER__ */
- # define hidden_weak(name)
- # define hidden_def(name)
- # define hidden_def_alias(name, alias)
- # define hidden_ver(local, name)
- # define hidden_data_weak(name)
- # define hidden_data_def(name)
- # define hidden_data_def_alias(name, alias)
- # define hidden_tls_def(name)
- # define hidden_nolink(name, lib, version)
- #endif
- #if IS_IN (libc)
- # define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
- # define libc_hidden_proto_alias(name, alias, attrs...) \
- hidden_proto_alias (name, alias, ##attrs)
- # define libc_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
- # define libc_hidden_def(name) hidden_def (name)
- # define libc_hidden_weak(name) hidden_weak (name)
- # define libc_hidden_nolink_sunrpc(name, version) hidden_nolink (name, libc, version)
- # define libc_hidden_ver(local, name) hidden_ver (local, name)
- # define libc_hidden_data_def(name) hidden_data_def (name)
- # define libc_hidden_data_def_alias(name, alias) hidden_data_def_alias (name, alias)
- # define libc_hidden_tls_def(name) hidden_tls_def (name)
- # define libc_hidden_data_weak(name) hidden_data_weak (name)
- #else
- # define libc_hidden_proto(name, attrs...)
- # define libc_hidden_proto_alias(name, alias, attrs...)
- # define libc_hidden_tls_proto(name, attrs...)
- # define libc_hidden_def(name)
- # define libc_hidden_weak(name)
- # define libc_hidden_ver(local, name)
- # define libc_hidden_data_def(name)
- # define libc_hidden_data_def_alias(name, alias)
- # define libc_hidden_tls_def(name)
- # define libc_hidden_data_weak(name)
- #endif
- #if IS_IN (rtld)
- # define rtld_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
- # define rtld_hidden_def(name) hidden_def (name)
- # define rtld_hidden_weak(name) hidden_weak (name)
- # define rtld_hidden_data_def(name) hidden_data_def (name)
- #else
- # define rtld_hidden_proto(name, attrs...)
- # define rtld_hidden_def(name)
- # define rtld_hidden_weak(name)
- # define rtld_hidden_data_def(name)
- #endif
- #if IS_IN (libm)
- # define libm_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
- # define libm_hidden_def(name) hidden_def (name)
- # define libm_hidden_weak(name) hidden_weak (name)
- # define libm_hidden_ver(local, name) hidden_ver (local, name)
- #else
- # define libm_hidden_proto(name, attrs...)
- # define libm_hidden_def(name)
- # define libm_hidden_weak(name)
- # define libm_hidden_ver(local, name)
- #endif
- #if IS_IN (libmvec)
- # define libmvec_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
- # define libmvec_hidden_def(name) hidden_def (name)
- #else
- # define libmvec_hidden_proto(name, attrs...)
- # define libmvec_hidden_def(name)
- #endif
- #if IS_IN (libresolv)
- # define libresolv_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
- # define libresolv_hidden_def(name) hidden_def (name)
- # define libresolv_hidden_data_def(name) hidden_data_def (name)
- #else
- # define libresolv_hidden_proto(name, attrs...)
- # define libresolv_hidden_def(name)
- # define libresolv_hidden_data_def(name)
- #endif
- #if IS_IN (libpthread)
- # define libpthread_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
- # define libpthread_hidden_def(name) hidden_def (name)
- #else
- # define libpthread_hidden_proto(name, attrs...)
- # define libpthread_hidden_def(name)
- #endif
- #if IS_IN (librt)
- # define librt_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
- # define librt_hidden_ver(local, name) hidden_ver (local, name)
- #else
- # define librt_hidden_proto(name, attrs...)
- # define librt_hidden_ver(local, name)
- #endif
- #if IS_IN (libnsl)
- # define libnsl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
- # define libnsl_hidden_nolink_def(name, version) hidden_nolink (name, libnsl, version)
- #else
- # define libnsl_hidden_proto(name, attrs...)
- #endif
- #define libc_hidden_builtin_proto(name, attrs...) libc_hidden_proto (name, ##attrs)
- #define libc_hidden_builtin_def(name) libc_hidden_def (name)
- #define libc_hidden_ldbl_proto(name, attrs...) libc_hidden_proto (name, ##attrs)
- #ifdef __ASSEMBLER__
- # define HIDDEN_BUILTIN_JUMPTARGET(name) HIDDEN_JUMPTARGET(name)
- #endif
- #if IS_IN (libanl)
- # define libanl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
- #else
- # define libanl_hidden_proto(name, attrs...)
- #endif
- /* Get some dirty hacks. */
- #include <symbol-hacks.h>
- /* Move compatibility symbols out of the way by placing them all in a
- special section. */
- #ifndef __ASSEMBLER__
- # define attribute_compat_text_section \
- __attribute__ ((section (".text.compat")))
- #else
- # define compat_text_section .section ".text.compat", "ax";
- #endif
- /* Helper / base macros for indirect function symbols. */
- #define __ifunc_resolver(type_name, name, expr, init, classifier, ...) \
- classifier inhibit_stack_protector \
- __typeof (type_name) *name##_ifunc (__VA_ARGS__) \
- { \
- init (); \
- __typeof (type_name) *res = expr; \
- return res; \
- }
- #ifdef HAVE_GCC_IFUNC
- # define __ifunc_args(type_name, name, expr, init, ...) \
- extern __typeof (type_name) name __attribute__ \
- ((ifunc (#name "_ifunc"))); \
- DIAG_PUSH_NEEDS_COMMENT_CLANG; \
- DIAG_IGNORE_NEEDS_COMMENT_CLANG (13, "-Wunused-function"); \
- __ifunc_resolver (type_name, name, expr, init, static, __VA_ARGS__); \
- DIAG_POP_NEEDS_COMMENT_CLANG;
- # define __ifunc_args_hidden(type_name, name, expr, init, ...) \
- __ifunc_args (type_name, name, expr, init, __VA_ARGS__)
- #else
- /* Gcc does not support __attribute__ ((ifunc (...))). Use the old behaviour
- as fallback. But keep in mind that the debug information for the ifunc
- resolver functions is not correct. It contains the ifunc'ed function as
- DW_AT_linkage_name. E.g. lldb uses this field and an inferior function
- call of the ifunc'ed function will fail due to "no matching function for
- call to ..." because the ifunc'ed function and the resolver function have
- different signatures. (Gcc support is disabled at least on a ppc64le
- Ubuntu 14.04 system.) */
- # define __ifunc_args(type_name, name, expr, init, ...) \
- extern __typeof (type_name) name; \
- __typeof (type_name) *name##_ifunc (__VA_ARGS__) __asm__ (#name); \
- __ifunc_resolver (type_name, name, expr, init, , __VA_ARGS__) \
- __asm__ (".type " #name ", %gnu_indirect_function");
- # define __ifunc_args_hidden(type_name, name, expr, init, ...) \
- extern __typeof (type_name) __libc_##name; \
- __ifunc (type_name, __libc_##name, expr, __VA_ARGS__, init) \
- strong_alias (__libc_##name, name);
- #endif /* !HAVE_GCC_IFUNC */
- #define __ifunc(type_name, name, expr, arg, init) \
- __ifunc_args (type_name, name, expr, init, arg)
- #define __ifunc_hidden(type_name, name, expr, arg, init) \
- __ifunc_args_hidden (type_name, name, expr, init, arg)
- /* The following macros are used for indirect function symbols in libc.so.
- First of all, you need to have the function prototyped somewhere,
- say in foo.h:
- int foo (int __bar);
- If you have an implementation for foo which e.g. uses a special hardware
- feature which isn't available on all machines where this libc.so will be
- used but decidable if available at runtime e.g. via hwcaps, you can provide
- two or multiple implementations of foo:
- int __foo_default (int __bar)
- {
- return __bar;
- }
- int __foo_special (int __bar)
- {
- return __bar;
- }
- If your function foo has no libc_hidden_proto (foo) defined for PLT
- bypassing, you can use:
- #define INIT_ARCH() unsigned long int hwcap = __GLRO(dl_hwcap);
- libc_ifunc (foo, (hwcap & HWCAP_SPECIAL) ? __foo_special : __foo_default);
- This will define a resolver function for foo which returns __foo_special or
- __foo_default depending on your specified expression. Please note that you
- have to define a macro function INIT_ARCH before using libc_ifunc macro as
- it is called by the resolver function before evaluating the specified
- expression. In this example it is used to prepare the hwcap variable.
- The resolver function is assigned to an ifunc'ed symbol foo. Calls to foo
- from inside or outside of libc.so will be indirected by a PLT call.
- If your function foo has a libc_hidden_proto (foo) defined for PLT bypassing
- and calls to foo within libc.so should always go to one specific
- implementation of foo e.g. __foo_default then you have to add:
- __hidden_ver1 (__foo_default, __GI_foo, __foo_default);
- or a tweaked definition of libc_hidden_def macro after the __foo_default
- function definition. Calls to foo within libc.so will always go directly to
- __foo_default. Calls to foo from outside libc.so will be indirected by a
- PLT call to ifunc'ed symbol foo which you have to define in a separate
- compile unit:
- #define foo __redirect_foo
- #include <foo.h>
- #undef foo
- extern __typeof (__redirect_foo) __foo_default attribute_hidden;
- extern __typeof (__redirect_foo) __foo_special attribute_hidden;
- libc_ifunc_redirected (__redirect_foo, foo,
- (hwcap & HWCAP_SPECIAL)
- ? __foo_special
- : __foo_default);
- This will define the ifunc'ed symbol foo like above. The redirection of foo
- in header file is needed to omit an additional definition of __GI_foo which
- would end in a linker error while linking libc.so. You have to specify
- __redirect_foo as first parameter which is used within libc_ifunc_redirected
- macro in conjunction with typeof to define the ifunc'ed symbol foo.
- If your function foo has a libc_hidden_proto (foo) defined and calls to foo
- within or from outside libc.so should go via ifunc'ed symbol, then you have
- to use:
- libc_ifunc_hidden (foo, foo,
- (hwcap & HWCAP_SPECIAL)
- ? __foo_special
- : __foo_default);
- libc_hidden_def (foo)
- The first parameter foo of libc_ifunc_hidden macro is used in the same way
- as for libc_ifunc_redirected macro. */
- #define libc_ifunc(name, expr) __ifunc (name, name, expr, void, INIT_ARCH)
- #define libc_ifunc_redirected(redirected_name, name, expr) \
- __ifunc (redirected_name, name, expr, void, INIT_ARCH)
- #define libc_ifunc_hidden(redirected_name, name, expr) \
- __ifunc_hidden (redirected_name, name, expr, void, INIT_ARCH)
- /* The body of the function is supposed to use __get_cpu_features
- which will, if necessary, initialize the data first. */
- #define libm_ifunc_init()
- #define libm_ifunc(name, expr) \
- __ifunc (name, name, expr, void, libm_ifunc_init)
- /* These macros facilitate sharing source files with gnulib.
- They are here instead of sys/cdefs.h because they should not be
- used in public header files.
- Their definitions should be kept consistent with the definitions in
- gnulib-common.m4, but it is not necessary to cater to old non-GCC
- compilers, since they will only be used while building glibc itself.
- (Note that _GNUC_PREREQ cannot be used in this file.) */
- /* Define as a marker that can be attached to declarations that might not
- be used. This helps to reduce warnings, such as from
- GCC -Wunused-parameter. */
- #if __GNUC__ >= 3 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 7)
- # define _GL_UNUSED __attribute__ ((__unused__))
- #else
- # define _GL_UNUSED
- #endif
- /* gcc supports the "unused" attribute on possibly unused labels, and
- g++ has since version 4.5. Note to support C++ as well as C,
- _GL_UNUSED_LABEL should be used with a trailing ; */
- #if !defined __cplusplus || __GNUC__ > 4 \
- || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
- # define _GL_UNUSED_LABEL _GL_UNUSED
- #else
- # define _GL_UNUSED_LABEL
- #endif
- /* The __pure__ attribute was added in gcc 2.96. */
- #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 96)
- # define _GL_ATTRIBUTE_PURE __attribute__ ((__pure__))
- #else
- # define _GL_ATTRIBUTE_PURE /* empty */
- #endif
- /* The __const__ attribute was added in gcc 2.95. */
- #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 95)
- # define _GL_ATTRIBUTE_CONST __attribute__ ((__const__))
- #else
- # define _GL_ATTRIBUTE_CONST /* empty */
- #endif
- #endif /* !_ISOMAC */
- #endif /* libc-symbols.h */
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