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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) 1995-2025 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#include <libc-misc.h>
63
64#ifndef _ISOMAC
65
66/* This is defined for the compilation of all C library code. features.h
67 tests this to avoid inclusion of stubs.h while compiling the library,
68 before stubs.h has been generated. Some library code that is shared
69 with other packages also tests this symbol to see if it is being
70 compiled as part of the C library. We must define this before including
71 config.h, because it makes some definitions conditional on whether libc
72 itself is being compiled, or just some generator program. */
73#define _LIBC 1
74
75/* Some files must be compiled with optimization on. */
76#if !defined __ASSEMBLER__ && !defined __OPTIMIZE__
77# error "glibc cannot be compiled without optimization"
78#endif
79
80/* -ffast-math cannot be applied to the C library, as it alters the ABI.
81 Some test components that use -ffast-math are currently not part of
82 IS_IN (testsuite) for technical reasons, so we have a secondary override. */
83#if defined __FAST_MATH__ && !defined TEST_FAST_MATH
84# error "glibc must not be compiled with -ffast-math"
85#endif
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/* zig patch: weak_hidden_alias was removed from glibc v2.36 (v2.37?), Zig
159 needs it for the v2.32 and earlier {f,l,}stat wrappers, so only include
160 in this header for 2.32 and earlier. */
161#if (__GLIBC__ == 2 && __GLIBC_MINOR__ <= 32) || __GLIBC__ < 2
162# define weak_hidden_alias(name, aliasname) \
163 _weak_hidden_alias (name, aliasname)
164# define _weak_hidden_alias(name, aliasname) \
165 extern __typeof (name) aliasname \
166 __attribute__ ((weak, alias (#name), __visibility__ ("hidden"))) \
167 __attribute_copy__ (name);
168#endif
169
170/* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined). */
171# define weak_extern(symbol) _weak_extern (weak symbol)
172# define _weak_extern(expr) _Pragma (#expr)
173
174/* In shared builds, the expression call_function_static_weak
175 (FUNCTION-SYMBOL, ARGUMENTS) invokes FUNCTION-SYMBOL (an
176 identifier) unconditionally, with the (potentially empty) argument
177 list ARGUMENTS. In static builds, if FUNCTION-SYMBOL has a
178 definition, the function is invoked as before; if FUNCTION-SYMBOL
179 is NULL, no call is performed. */
180# ifdef SHARED
181# define call_function_static_weak(func, ...) func (__VA_ARGS__)
182# else /* !SHARED */
183# define call_function_static_weak(func, ...) \
184 ({ \
185 extern __typeof__ (func) func weak_function; \
186 (func != NULL ? func (__VA_ARGS__) : (void)0); \
187 })
188# endif
189
190#else /* __ASSEMBLER__ */
191
192# ifdef HAVE_ASM_SET_DIRECTIVE
193# define strong_alias(original, alias) \
194 .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP \
195 .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original)
196# define strong_data_alias(original, alias) strong_alias(original, alias)
197# else
198# define strong_alias(original, alias) \
199 .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP \
200 C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
201# define strong_data_alias(original, alias) strong_alias(original, alias)
202# endif
203
204# define weak_alias(original, alias) \
205 .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP \
206 C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original)
207
208# define weak_extern(symbol) \
209 .weak C_SYMBOL_NAME (symbol)
210
211#endif /* __ASSEMBLER__ */
212
213/* Determine the return address. */
214#define RETURN_ADDRESS(nr) \
215 __builtin_extract_return_addr (__builtin_return_address (nr))
216
217/* When a reference to SYMBOL is encountered, the linker will emit a
218 warning message MSG. */
219/* We want the .gnu.warning.SYMBOL section to be unallocated. */
220#define __make_section_unallocated(section_string) \
221 asm (".section " section_string "\n\t.previous");
222
223/* Tacking on "\n\t#" to the section name makes gcc put its bogus
224 section attributes on what looks like a comment to the assembler. */
225#ifdef HAVE_SECTION_QUOTES
226# define __sec_comment "\"\n\t#\""
227#else
228# define __sec_comment "\n\t#"
229#endif
230#define link_warning(symbol, msg) \
231 __make_section_unallocated (".gnu.warning." #symbol) \
232 static const char __evoke_link_warning_##symbol[] \
233 __attribute__ ((used, section (".gnu.warning." #symbol __sec_comment))) \
234 = msg;
235
236/* A canned warning for sysdeps/stub functions. */
237#define stub_warning(name) \
238 __make_section_unallocated (".gnu.glibc-stub." #name) \
239 link_warning (name, #name " is not implemented and will always fail")
240
241/* Warning for linking functions calling dlopen into static binaries. */
242#ifdef SHARED
243#define static_link_warning(name)
244#else
245#define static_link_warning(name) static_link_warning1(name)
246#define static_link_warning1(name) \
247 link_warning(name, "Using '" #name "' in statically linked applications \
248requires at runtime the shared libraries from the glibc version used \
249for linking")
250#endif
251
252/* Declare SYMBOL to be TYPE (`function' or `object') of SIZE bytes
253 alias to ORIGINAL, when the assembler supports such declarations
254 (such as in ELF).
255 This is only necessary when defining something in assembly, or playing
256 funny alias games where the size should be other than what the compiler
257 thinks it is. */
258#define declare_object_symbol_alias(symbol, original, size) \
259 declare_object_symbol_alias_1 (symbol, original, size)
260#ifdef __ASSEMBLER__
261# define declare_object_symbol_alias_1(symbol, original, s_size) \
262 strong_alias (original, symbol) ASM_LINE_SEP \
263 .type C_SYMBOL_NAME (symbol), %object ASM_LINE_SEP \
264 .size C_SYMBOL_NAME (symbol), s_size ASM_LINE_SEP
265#else /* Not __ASSEMBLER__. */
266# ifdef HAVE_ASM_SET_DIRECTIVE
267# define declare_object_symbol_alias_1(symbol, original, size) \
268 asm (".global " __SYMBOL_PREFIX # symbol "\n" \
269 ".type " __SYMBOL_PREFIX # symbol ", %object\n" \
270 ".set " __SYMBOL_PREFIX #symbol ", " __SYMBOL_PREFIX original "\n" \
271 ".size " __SYMBOL_PREFIX #symbol ", " #size "\n");
272# else
273# define declare_object_symbol_alias_1(symbol, original, size) \
274 asm (".global " __SYMBOL_PREFIX # symbol "\n" \
275 ".type " __SYMBOL_PREFIX # symbol ", %object\n" \
276 __SYMBOL_PREFIX #symbol " = " __SYMBOL_PREFIX original "\n" \
277 ".size " __SYMBOL_PREFIX #symbol ", " #size "\n");
278# endif /* HAVE_ASM_SET_DIRECTIVE */
279#endif /* __ASSEMBLER__ */
280
281
282/*
283
284*/
285
286#ifdef HAVE_GNU_RETAIN
287# define attribute_used_retain __attribute__ ((__used__, __retain__))
288#else
289# define attribute_used_retain __attribute__ ((__used__))
290#endif
291
292/* Symbol set support macros. */
293
294/* Make SYMBOL, which is in the text segment, an element of SET. */
295#define text_set_element(set, symbol) _elf_set_element(set, symbol)
296/* Make SYMBOL, which is in the data segment, an element of SET. */
297#define data_set_element(set, symbol) _elf_set_element(set, symbol)
298/* Make SYMBOL, which is in the bss segment, an element of SET. */
299#define bss_set_element(set, symbol) _elf_set_element(set, symbol)
300
301/* These are all done the same way in ELF.
302 There is a new section created for each set. */
303#ifdef SHARED
304/* When building a shared library, make the set section writable,
305 because it will need to be relocated at run time anyway. */
306# define _elf_set_element(set, symbol) \
307 static const void *__elf_set_##set##_element_##symbol##__ \
308 attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
309#else
310# define _elf_set_element(set, symbol) \
311 static const void *const __elf_set_##set##_element_##symbol##__ \
312 attribute_used_retain __attribute__ ((section (#set))) = &(symbol)
313#endif
314
315/* Define SET as a symbol set. This may be required (it is in a.out) to
316 be able to use the set's contents. */
317#define symbol_set_define(set) symbol_set_declare(set)
318
319/* Declare SET for use in this module, if defined in another module.
320 In a shared library, this is always local to that shared object.
321 For static linking, the set might be wholly absent and so we use
322 weak references. */
323#define symbol_set_declare(set) \
324 extern char const __start_##set[] __symbol_set_attribute; \
325 extern char const __stop_##set[] __symbol_set_attribute;
326#ifdef SHARED
327# define __symbol_set_attribute attribute_hidden
328#else
329# define __symbol_set_attribute __attribute__ ((weak))
330#endif
331
332/* Return a pointer (void *const *) to the first element of SET. */
333#define symbol_set_first_element(set) ((void *const *) (&__start_##set))
334
335/* Return true iff PTR (a void *const *) has been incremented
336 past the last element in SET. */
337#define symbol_set_end_p(set, ptr) ((ptr) >= (void *const *) &__stop_##set)
338
339#ifdef SHARED
340# define symbol_version(real, name, version) \
341 symbol_version_reference(real, name, version)
342# define default_symbol_version(real, name, version) \
343 _default_symbol_version(real, name, version)
344/* See <libc-symver.h>. */
345# ifdef __ASSEMBLER__
346# define _default_symbol_version(real, name, version) \
347 _set_symbol_version (real, name@@version)
348# else
349# define _default_symbol_version(real, name, version) \
350 _set_symbol_version (real, #name "@@" #version)
351# endif
352
353/* Evaluates to a string literal for VERSION in LIB. */
354# define symbol_version_string(lib, version) \
355 _symbol_version_stringify_1 (VERSION_##lib##_##version)
356# define _symbol_version_stringify_1(arg) _symbol_version_stringify_2 (arg)
357# define _symbol_version_stringify_2(arg) #arg
358
359#else /* !SHARED */
360# define symbol_version(real, name, version)
361# define default_symbol_version(real, name, version) \
362 strong_alias(real, name)
363#endif
364
365#if defined SHARED || defined LIBC_NONSHARED \
366 || (BUILD_PIE_DEFAULT && IS_IN (libc))
367# define attribute_hidden __attribute__ ((visibility ("hidden")))
368#else
369# define attribute_hidden
370#endif
371
372#define attribute_tls_model_ie __attribute__ ((tls_model ("initial-exec")))
373
374#define attribute_relro __attribute__ ((section (".data.rel.ro")))
375
376
377/* The following macros are used for PLT bypassing within libc.so
378 (and if needed other libraries similarly).
379 First of all, you need to have the function prototyped somewhere,
380 say in foo/foo.h:
381
382 int foo (int __bar);
383
384 If calls to foo within libc.so should always go to foo defined in libc.so,
385 then in include/foo.h you add:
386
387 libc_hidden_proto (foo)
388
389 line and after the foo function definition:
390
391 int foo (int __bar)
392 {
393 return __bar;
394 }
395 libc_hidden_def (foo)
396
397 or
398
399 int foo (int __bar)
400 {
401 return __bar;
402 }
403 libc_hidden_weak (foo)
404
405 Similarly for global data. If references to foo within libc.so should
406 always go to foo defined in libc.so, then in include/foo.h you add:
407
408 libc_hidden_proto (foo)
409
410 line and after foo's definition:
411
412 int foo = INITIAL_FOO_VALUE;
413 libc_hidden_data_def (foo)
414
415 or
416
417 int foo = INITIAL_FOO_VALUE;
418 libc_hidden_data_weak (foo)
419
420 If foo is normally just an alias (strong or weak) to some other function,
421 you should use the normal strong_alias first, then add libc_hidden_def
422 or libc_hidden_weak:
423
424 int baz (int __bar)
425 {
426 return __bar;
427 }
428 strong_alias (baz, foo)
429 libc_hidden_weak (foo)
430
431 If the function should be internal to multiple objects, say ld.so and
432 libc.so, the best way is to use:
433
434 #if IS_IN (libc) || IS_IN (rtld)
435 hidden_proto (foo)
436 #endif
437
438 in include/foo.h and the normal macros at all function definitions
439 depending on what DSO they belong to.
440
441 If versioned_symbol macro is used to define foo,
442 libc_hidden_ver macro should be used, as in:
443
444 int __real_foo (int __bar)
445 {
446 return __bar;
447 }
448 versioned_symbol (libc, __real_foo, foo, GLIBC_2_1);
449 libc_hidden_ver (__real_foo, foo) */
450
451#if defined SHARED && !defined NO_HIDDEN
452# ifndef __ASSEMBLER__
453# define __hidden_proto_hiddenattr(attrs...) \
454 __attribute__ ((visibility ("hidden"), ##attrs))
455# define hidden_proto(name, attrs...) \
456 __hidden_proto (name, , __GI_##name, ##attrs)
457# define hidden_proto_alias(name, alias, attrs...) \
458 __hidden_proto_alias (name, , alias, ##attrs)
459# define hidden_tls_proto(name, attrs...) \
460 __hidden_proto (name, __thread, __GI_##name, ##attrs)
461# define __hidden_proto(name, thread, internal, attrs...) \
462 extern thread __typeof (name) name __asm__ (__hidden_asmname (#internal)) \
463 __hidden_proto_hiddenattr (attrs);
464# define __hidden_proto_alias(name, thread, internal, attrs...) \
465 extern thread __typeof (name) internal __hidden_proto_hiddenattr (attrs);
466# define __hidden_asmname(name) \
467 __hidden_asmname1 (__USER_LABEL_PREFIX__, name)
468# define __hidden_asmname1(prefix, name) __hidden_asmname2(prefix, name)
469# define __hidden_asmname2(prefix, name) #prefix name
470# define __hidden_ver1(local, internal, name) \
471 __hidden_ver2 (, local, internal, name)
472# define __hidden_ver2(thread, local, internal, name) \
473 extern thread __typeof (name) __EI_##name \
474 __asm__(__hidden_asmname (#internal)); \
475 extern thread __typeof (name) __EI_##name \
476 __attribute__((alias (__hidden_asmname (#local)))) \
477 __attribute_copy__ (name)
478# define hidden_ver(local, name) __hidden_ver1(local, __GI_##name, name);
479# define hidden_def(name) __hidden_ver1(__GI_##name, name, name);
480# define hidden_def_alias(name, internal) \
481 strong_alias (name, internal)
482# define hidden_data_def(name) hidden_def(name)
483# define hidden_data_def_alias(name, alias) hidden_def_alias(name, alias)
484# define hidden_tls_def(name) \
485 __hidden_ver2 (__thread, __GI_##name, name, name);
486# define hidden_weak(name) \
487 __hidden_ver1(__GI_##name, name, name) __attribute__((weak));
488# define hidden_data_weak(name) hidden_weak(name)
489# define hidden_nolink(name, lib, version) \
490 __hidden_nolink1 (__GI_##name, __EI_##name, name, VERSION_##lib##_##version)
491# define __hidden_nolink1(local, internal, name, version) \
492 __hidden_nolink2 (local, internal, name, version)
493# define __hidden_nolink2(local, internal, name, version) \
494 extern __typeof (name) internal __attribute__ ((alias (#local))) \
495 __attribute_copy__ (name); \
496 __hidden_nolink3 (local, internal, #name "@" #version)
497# define __hidden_nolink3(local, internal, vername) \
498 __asm__ (".symver " #internal ", " vername);
499# else
500/* For assembly, we need to do the opposite of what we do in C:
501 in assembly gcc __REDIRECT stuff is not in place, so functions
502 are defined by its normal name and we need to create the
503 __GI_* alias to it, in C __REDIRECT causes the function definition
504 to use __GI_* name and we need to add alias to the real name.
505 There is no reason to use hidden_weak over hidden_def in assembly,
506 but we provide it for consistency with the C usage.
507 hidden_proto doesn't make sense for assembly but the equivalent
508 is to call via the HIDDEN_JUMPTARGET macro instead of JUMPTARGET. */
509# define hidden_def(name) strong_alias (name, __GI_##name)
510# define hidden_def_alias(name, alias) strong_alias (name, alias)
511# define hidden_weak(name) hidden_def (name)
512# define hidden_ver(local, name) strong_alias (local, __GI_##name)
513# define hidden_data_def(name) strong_data_alias (name, __GI_##name)
514# define hidden_data_def_alias(name, alias) strong_data_alias (name, alias)
515# define hidden_tls_def(name) hidden_data_def (name)
516# define hidden_data_weak(name) hidden_data_def (name)
517# define HIDDEN_JUMPTARGET(name) __GI_##name
518# endif
519#else
520# ifndef __ASSEMBLER__
521# if !defined SHARED && IS_IN (libc) && !defined LIBC_NONSHARED \
522 && (!defined PIC || !defined NO_HIDDEN_EXTERN_FUNC_IN_PIE) \
523 && !defined NO_HIDDEN
524# define __hidden_proto_hiddenattr(attrs...) \
525 __attribute__ ((visibility ("hidden"), ##attrs))
526# define hidden_proto(name, attrs...) \
527 __hidden_proto (name, , name, ##attrs)
528# define hidden_proto_alias(name, alias, attrs...) \
529 __hidden_proto_alias (name, , alias, ##attrs)
530# define hidden_tls_proto(name, attrs...) \
531 __hidden_proto (name, __thread, name, ##attrs)
532# define __hidden_proto(name, thread, internal, attrs...) \
533 extern thread __typeof (name) name __hidden_proto_hiddenattr (attrs);
534# define __hidden_proto_alias(name, thread, internal, attrs...) \
535 extern thread __typeof (name) internal __hidden_proto_hiddenattr (attrs);
536# else
537# define hidden_proto(name, attrs...)
538# define hidden_proto_alias(name, alias, attrs...)
539# define hidden_tls_proto(name, attrs...)
540# endif
541# else
542# define HIDDEN_JUMPTARGET(name) JUMPTARGET(name)
543# endif /* Not __ASSEMBLER__ */
544# define hidden_weak(name)
545# define hidden_def(name)
546# define hidden_def_alias(name, alias)
547# define hidden_ver(local, name)
548# define hidden_data_weak(name)
549# define hidden_data_def(name)
550# define hidden_data_def_alias(name, alias)
551# define hidden_tls_def(name)
552# define hidden_nolink(name, lib, version)
553#endif
554
555#if IS_IN (libc)
556# define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
557# define libc_hidden_proto_alias(name, alias, attrs...) \
558 hidden_proto_alias (name, alias, ##attrs)
559# define libc_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
560# define libc_hidden_def(name) hidden_def (name)
561# define libc_hidden_weak(name) hidden_weak (name)
562# define libc_hidden_nolink_sunrpc(name, version) hidden_nolink (name, libc, version)
563# define libc_hidden_ver(local, name) hidden_ver (local, name)
564# define libc_hidden_data_def(name) hidden_data_def (name)
565# define libc_hidden_data_def_alias(name, alias) hidden_data_def_alias (name, alias)
566# define libc_hidden_tls_def(name) hidden_tls_def (name)
567# define libc_hidden_data_weak(name) hidden_data_weak (name)
568#else
569# define libc_hidden_proto(name, attrs...)
570# define libc_hidden_proto_alias(name, alias, attrs...)
571# define libc_hidden_tls_proto(name, attrs...)
572# define libc_hidden_def(name)
573# define libc_hidden_weak(name)
574# define libc_hidden_ver(local, name)
575# define libc_hidden_data_def(name)
576# define libc_hidden_data_def_alias(name, alias)
577# define libc_hidden_tls_def(name)
578# define libc_hidden_data_weak(name)
579#endif
580
581#if IS_IN (rtld)
582# define rtld_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
583# define rtld_hidden_def(name) hidden_def (name)
584# define rtld_hidden_weak(name) hidden_weak (name)
585# define rtld_hidden_data_def(name) hidden_data_def (name)
586#else
587# define rtld_hidden_proto(name, attrs...)
588# define rtld_hidden_def(name)
589# define rtld_hidden_weak(name)
590# define rtld_hidden_data_def(name)
591#endif
592
593#if IS_IN (libm)
594# define libm_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
595# define libm_hidden_def(name) hidden_def (name)
596# define libm_hidden_weak(name) hidden_weak (name)
597# define libm_hidden_ver(local, name) hidden_ver (local, name)
598#else
599# define libm_hidden_proto(name, attrs...)
600# define libm_hidden_def(name)
601# define libm_hidden_weak(name)
602# define libm_hidden_ver(local, name)
603#endif
604
605#if IS_IN (libmvec)
606# define libmvec_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
607# define libmvec_hidden_def(name) hidden_def (name)
608#else
609# define libmvec_hidden_proto(name, attrs...)
610# define libmvec_hidden_def(name)
611#endif
612
613#if IS_IN (libresolv)
614# define libresolv_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
615# define libresolv_hidden_def(name) hidden_def (name)
616# define libresolv_hidden_data_def(name) hidden_data_def (name)
617#else
618# define libresolv_hidden_proto(name, attrs...)
619# define libresolv_hidden_def(name)
620# define libresolv_hidden_data_def(name)
621#endif
622
623#if IS_IN (libpthread)
624# define libpthread_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
625# define libpthread_hidden_def(name) hidden_def (name)
626#else
627# define libpthread_hidden_proto(name, attrs...)
628# define libpthread_hidden_def(name)
629#endif
630
631#if IS_IN (librt)
632# define librt_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
633# define librt_hidden_ver(local, name) hidden_ver (local, name)
634#else
635# define librt_hidden_proto(name, attrs...)
636# define librt_hidden_ver(local, name)
637#endif
638
639#if IS_IN (libnsl)
640# define libnsl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
641# define libnsl_hidden_nolink_def(name, version) hidden_nolink (name, libnsl, version)
642#else
643# define libnsl_hidden_proto(name, attrs...)
644#endif
645
646#define libc_hidden_builtin_proto(name, attrs...) libc_hidden_proto (name, ##attrs)
647#define libc_hidden_builtin_def(name) libc_hidden_def (name)
648
649#define libc_hidden_ldbl_proto(name, attrs...) libc_hidden_proto (name, ##attrs)
650#ifdef __ASSEMBLER__
651# define HIDDEN_BUILTIN_JUMPTARGET(name) HIDDEN_JUMPTARGET(name)
652#endif
653
654#if IS_IN (libanl)
655# define libanl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
656#else
657# define libanl_hidden_proto(name, attrs...)
658#endif
659
660/* Get some dirty hacks. */
661#include <symbol-hacks.h>
662
663/* Move compatibility symbols out of the way by placing them all in a
664 special section. */
665#ifndef __ASSEMBLER__
666# define attribute_compat_text_section \
667 __attribute__ ((section (".text.compat")))
668#else
669# define compat_text_section .section ".text.compat", "ax";
670#endif
671
672/* Helper / base macros for indirect function symbols. */
673#define __ifunc_resolver(type_name, name, expr, init, classifier, ...) \
674 classifier inhibit_stack_protector \
675 __typeof (type_name) *name##_ifunc (__VA_ARGS__) \
676 { \
677 init (); \
678 __typeof (type_name) *res = expr; \
679 return res; \
680 }
681
682#ifdef HAVE_GCC_IFUNC
683# define __ifunc_args(type_name, name, expr, init, ...) \
684 extern __typeof (type_name) name __attribute__ \
685 ((ifunc (#name "_ifunc"))); \
686 __ifunc_resolver (type_name, name, expr, init, static, __VA_ARGS__)
687
688# define __ifunc_args_hidden(type_name, name, expr, init, ...) \
689 __ifunc_args (type_name, name, expr, init, __VA_ARGS__)
690#else
691/* Gcc does not support __attribute__ ((ifunc (...))). Use the old behaviour
692 as fallback. But keep in mind that the debug information for the ifunc
693 resolver functions is not correct. It contains the ifunc'ed function as
694 DW_AT_linkage_name. E.g. lldb uses this field and an inferior function
695 call of the ifunc'ed function will fail due to "no matching function for
696 call to ..." because the ifunc'ed function and the resolver function have
697 different signatures. (Gcc support is disabled at least on a ppc64le
698 Ubuntu 14.04 system.) */
699
700# define __ifunc_args(type_name, name, expr, init, ...) \
701 extern __typeof (type_name) name; \
702 __typeof (type_name) *name##_ifunc (__VA_ARGS__) __asm__ (#name); \
703 __ifunc_resolver (type_name, name, expr, init, , __VA_ARGS__) \
704 __asm__ (".type " #name ", %gnu_indirect_function");
705
706# define __ifunc_args_hidden(type_name, name, expr, init, ...) \
707 extern __typeof (type_name) __libc_##name; \
708 __ifunc (type_name, __libc_##name, expr, __VA_ARGS__, init) \
709 strong_alias (__libc_##name, name);
710#endif /* !HAVE_GCC_IFUNC */
711
712#define __ifunc(type_name, name, expr, arg, init) \
713 __ifunc_args (type_name, name, expr, init, arg)
714
715#define __ifunc_hidden(type_name, name, expr, arg, init) \
716 __ifunc_args_hidden (type_name, name, expr, init, arg)
717
718/* The following macros are used for indirect function symbols in libc.so.
719 First of all, you need to have the function prototyped somewhere,
720 say in foo.h:
721
722 int foo (int __bar);
723
724 If you have an implementation for foo which e.g. uses a special hardware
725 feature which isn't available on all machines where this libc.so will be
726 used but decidable if available at runtime e.g. via hwcaps, you can provide
727 two or multiple implementations of foo:
728
729 int __foo_default (int __bar)
730 {
731 return __bar;
732 }
733
734 int __foo_special (int __bar)
735 {
736 return __bar;
737 }
738
739 If your function foo has no libc_hidden_proto (foo) defined for PLT
740 bypassing, you can use:
741
742 #define INIT_ARCH() unsigned long int hwcap = __GLRO(dl_hwcap);
743
744 libc_ifunc (foo, (hwcap & HWCAP_SPECIAL) ? __foo_special : __foo_default);
745
746 This will define a resolver function for foo which returns __foo_special or
747 __foo_default depending on your specified expression. Please note that you
748 have to define a macro function INIT_ARCH before using libc_ifunc macro as
749 it is called by the resolver function before evaluating the specified
750 expression. In this example it is used to prepare the hwcap variable.
751 The resolver function is assigned to an ifunc'ed symbol foo. Calls to foo
752 from inside or outside of libc.so will be indirected by a PLT call.
753
754 If your function foo has a libc_hidden_proto (foo) defined for PLT bypassing
755 and calls to foo within libc.so should always go to one specific
756 implementation of foo e.g. __foo_default then you have to add:
757
758 __hidden_ver1 (__foo_default, __GI_foo, __foo_default);
759
760 or a tweaked definition of libc_hidden_def macro after the __foo_default
761 function definition. Calls to foo within libc.so will always go directly to
762 __foo_default. Calls to foo from outside libc.so will be indirected by a
763 PLT call to ifunc'ed symbol foo which you have to define in a separate
764 compile unit:
765
766 #define foo __redirect_foo
767 #include <foo.h>
768 #undef foo
769
770 extern __typeof (__redirect_foo) __foo_default attribute_hidden;
771 extern __typeof (__redirect_foo) __foo_special attribute_hidden;
772
773 libc_ifunc_redirected (__redirect_foo, foo,
774 (hwcap & HWCAP_SPECIAL)
775 ? __foo_special
776 : __foo_default);
777
778 This will define the ifunc'ed symbol foo like above. The redirection of foo
779 in header file is needed to omit an additional definition of __GI_foo which
780 would end in a linker error while linking libc.so. You have to specify
781 __redirect_foo as first parameter which is used within libc_ifunc_redirected
782 macro in conjunction with typeof to define the ifunc'ed symbol foo.
783
784 If your function foo has a libc_hidden_proto (foo) defined and calls to foo
785 within or from outside libc.so should go via ifunc'ed symbol, then you have
786 to use:
787
788 libc_ifunc_hidden (foo, foo,
789 (hwcap & HWCAP_SPECIAL)
790 ? __foo_special
791 : __foo_default);
792 libc_hidden_def (foo)
793
794 The first parameter foo of libc_ifunc_hidden macro is used in the same way
795 as for libc_ifunc_redirected macro. */
796
797#define libc_ifunc(name, expr) __ifunc (name, name, expr, void, INIT_ARCH)
798
799#define libc_ifunc_redirected(redirected_name, name, expr) \
800 __ifunc (redirected_name, name, expr, void, INIT_ARCH)
801
802#define libc_ifunc_hidden(redirected_name, name, expr) \
803 __ifunc_hidden (redirected_name, name, expr, void, INIT_ARCH)
804
805/* The body of the function is supposed to use __get_cpu_features
806 which will, if necessary, initialize the data first. */
807#define libm_ifunc_init()
808#define libm_ifunc(name, expr) \
809 __ifunc (name, name, expr, void, libm_ifunc_init)
810
811/* These macros facilitate sharing source files with gnulib.
812
813 They are here instead of sys/cdefs.h because they should not be
814 used in public header files.
815
816 Their definitions should be kept consistent with the definitions in
817 gnulib-common.m4, but it is not necessary to cater to old non-GCC
818 compilers, since they will only be used while building glibc itself.
819 (Note that _GNUC_PREREQ cannot be used in this file.) */
820
821/* Define as a marker that can be attached to declarations that might not
822 be used. This helps to reduce warnings, such as from
823 GCC -Wunused-parameter. */
824#if __GNUC__ >= 3 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 7)
825# define _GL_UNUSED __attribute__ ((__unused__))
826#else
827# define _GL_UNUSED
828#endif
829
830/* gcc supports the "unused" attribute on possibly unused labels, and
831 g++ has since version 4.5. Note to support C++ as well as C,
832 _GL_UNUSED_LABEL should be used with a trailing ; */
833#if !defined __cplusplus || __GNUC__ > 4 \
834 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
835# define _GL_UNUSED_LABEL _GL_UNUSED
836#else
837# define _GL_UNUSED_LABEL
838#endif
839
840/* The __pure__ attribute was added in gcc 2.96. */
841#if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 96)
842# define _GL_ATTRIBUTE_PURE __attribute__ ((__pure__))
843#else
844# define _GL_ATTRIBUTE_PURE /* empty */
845#endif
846
847/* The __const__ attribute was added in gcc 2.95. */
848#if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 95)
849# define _GL_ATTRIBUTE_CONST __attribute__ ((__const__))
850#else
851# define _GL_ATTRIBUTE_CONST /* empty */
852#endif
853
854#endif /* !_ISOMAC */
855#endif /* libc-symbols.h */