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