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) 1995-2017 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 | <http://www.gnu.org/licenses/>. */ |
19 | |
20 | #ifndef _LIBC_SYMBOLS_H |
21 | #define _LIBC_SYMBOLS_H 1 |
22 | |
23 | #define IN_MODULE PASTE_NAME (MODULE_, MODULE_NAME) |
24 | #define IS_IN(lib) (IN_MODULE == MODULE_##lib) |
25 | |
26 | /* Returns true if the current module is a versioned library. Versioned |
27 | library names culled from shlib-versions files are assigned a MODULE_* |
28 | value lower than MODULE_LIBS_BEGIN. */ |
29 | #define IS_IN_LIB (IN_MODULE > MODULE_LIBS_BEGIN) |
30 | |
31 | #define PASTE_NAME(a,b) PASTE_NAME1 (a,b) |
32 | #define PASTE_NAME1(a,b) a##b |
33 | |
34 | /* This file's macros are included implicitly in the compilation of every |
35 | file in the C library by -imacros. |
36 | |
37 | We include config.h which is generated by configure. |
38 | It should define for us the following symbol: |
39 | |
40 | * HAVE_ASM_SET_DIRECTIVE if we have `.set B, A' instead of `A = B'. |
41 | |
42 | */ |
43 | |
44 | /* This is defined for the compilation of all C library code. features.h |
45 | tests this to avoid inclusion of stubs.h while compiling the library, |
46 | before stubs.h has been generated. Some library code that is shared |
47 | with other packages also tests this symbol to see if it is being |
48 | compiled as part of the C library. We must define this before including |
49 | config.h, because it makes some definitions conditional on whether libc |
50 | itself is being compiled, or just some generator program. */ |
51 | #define _LIBC 1 |
52 | |
53 | /* Enable declarations of GNU extensions, since we are compiling them. */ |
54 | #define _GNU_SOURCE 1 |
55 | |
56 | #include <config.h> |
57 | |
58 | /* Define this for the benefit of portable GNU code that wants to check it. |
59 | Code that checks with #if will not #include <config.h> again, since we've |
60 | already done it (and this file is implicitly included in every compile, |
61 | via -include). Code that checks with #ifdef will #include <config.h>, |
62 | but that file should always be idempotent (i.e., it's just #define/#undef |
63 | and nothing else anywhere should be changing the macro state it touches), |
64 | so it's harmless. */ |
65 | #define HAVE_CONFIG_H 0 |
66 | |
67 | /* Define these macros for the benefit of portable GNU code that wants to check |
68 | them. Of course, STDC_HEADERS is never false when building libc! */ |
69 | #define 1 |
70 | #define HAVE_MBSTATE_T 1 |
71 | #define HAVE_MBSRTOWCS 1 |
72 | #define HAVE_LIBINTL_H 1 |
73 | #define HAVE_WCTYPE_H 1 |
74 | #define HAVE_ISWCTYPE 1 |
75 | #define ENABLE_NLS 1 |
76 | |
77 | /* The symbols in all the user (non-_) macros are C symbols. */ |
78 | |
79 | #ifndef __SYMBOL_PREFIX |
80 | # define __SYMBOL_PREFIX |
81 | #endif |
82 | |
83 | #ifndef C_SYMBOL_NAME |
84 | # define C_SYMBOL_NAME(name) name |
85 | #endif |
86 | |
87 | #ifndef ASM_LINE_SEP |
88 | # define ASM_LINE_SEP ; |
89 | #endif |
90 | |
91 | #ifndef __ASSEMBLER__ |
92 | /* GCC understands weak symbols and aliases; use its interface where |
93 | possible, instead of embedded assembly language. */ |
94 | |
95 | /* Define ALIASNAME as a strong alias for NAME. */ |
96 | # define strong_alias(name, aliasname) _strong_alias(name, aliasname) |
97 | # define _strong_alias(name, aliasname) \ |
98 | extern __typeof (name) aliasname __attribute__ ((alias (#name))); |
99 | |
100 | /* This comes between the return type and function name in |
101 | a function definition to make that definition weak. */ |
102 | # define weak_function __attribute__ ((weak)) |
103 | # define weak_const_function __attribute__ ((weak, __const__)) |
104 | |
105 | /* Define ALIASNAME as a weak alias for NAME. |
106 | If weak aliases are not available, this defines a strong alias. */ |
107 | # define weak_alias(name, aliasname) _weak_alias (name, aliasname) |
108 | # define _weak_alias(name, aliasname) \ |
109 | extern __typeof (name) aliasname __attribute__ ((weak, alias (#name))); |
110 | |
111 | /* Same as WEAK_ALIAS, but mark symbol as hidden. */ |
112 | # define weak_hidden_alias(name, aliasname) \ |
113 | _weak_hidden_alias (name, aliasname) |
114 | # define _weak_hidden_alias(name, aliasname) \ |
115 | extern __typeof (name) aliasname \ |
116 | __attribute__ ((weak, alias (#name), __visibility__ ("hidden"))); |
117 | |
118 | /* Declare SYMBOL as weak undefined symbol (resolved to 0 if not defined). */ |
119 | # define weak_extern(symbol) _weak_extern (weak symbol) |
120 | # define _weak_extern(expr) _Pragma (#expr) |
121 | |
122 | /* In shared builds, the expression call_function_static_weak |
123 | (FUNCTION-SYMBOL, ARGUMENTS) invokes FUNCTION-SYMBOL (an |
124 | identifier) unconditionally, with the (potentially empty) argument |
125 | list ARGUMENTS. In static builds, if FUNCTION-SYMBOL has a |
126 | definition, the function is invoked as before; if FUNCTION-SYMBOL |
127 | is NULL, no call is performed. */ |
128 | # ifdef SHARED |
129 | # define call_function_static_weak(func, ...) func (__VA_ARGS__) |
130 | # else /* !SHARED */ |
131 | # define call_function_static_weak(func, ...) \ |
132 | ({ \ |
133 | extern __typeof__ (func) func weak_function; \ |
134 | (func != NULL ? func (__VA_ARGS__) : (void)0); \ |
135 | }) |
136 | # endif |
137 | |
138 | #else /* __ASSEMBLER__ */ |
139 | |
140 | # ifdef HAVE_ASM_SET_DIRECTIVE |
141 | # define strong_alias(original, alias) \ |
142 | .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP \ |
143 | .set C_SYMBOL_NAME (alias),C_SYMBOL_NAME (original) |
144 | # define strong_data_alias(original, alias) strong_alias(original, alias) |
145 | # else |
146 | # define strong_alias(original, alias) \ |
147 | .globl C_SYMBOL_NAME (alias) ASM_LINE_SEP \ |
148 | C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) |
149 | # define strong_data_alias(original, alias) strong_alias(original, alias) |
150 | # endif |
151 | |
152 | # define weak_alias(original, alias) \ |
153 | .weak C_SYMBOL_NAME (alias) ASM_LINE_SEP \ |
154 | C_SYMBOL_NAME (alias) = C_SYMBOL_NAME (original) |
155 | |
156 | # define weak_extern(symbol) \ |
157 | .weak C_SYMBOL_NAME (symbol) |
158 | |
159 | #endif /* __ASSEMBLER__ */ |
160 | |
161 | /* On some platforms we can make internal function calls (i.e., calls of |
162 | functions not exported) a bit faster by using a different calling |
163 | convention. */ |
164 | #ifndef internal_function |
165 | # define internal_function /* empty */ |
166 | #endif |
167 | |
168 | /* Determine the return address. */ |
169 | #define RETURN_ADDRESS(nr) \ |
170 | __builtin_extract_return_addr (__builtin_return_address (nr)) |
171 | |
172 | /* When a reference to SYMBOL is encountered, the linker will emit a |
173 | warning message MSG. */ |
174 | /* We want the .gnu.warning.SYMBOL section to be unallocated. */ |
175 | #define __make_section_unallocated(section_string) \ |
176 | asm (".section " section_string "\n\t.previous"); |
177 | |
178 | /* Tacking on "\n\t#" to the section name makes gcc put it's bogus |
179 | section attributes on what looks like a comment to the assembler. */ |
180 | #ifdef HAVE_SECTION_QUOTES |
181 | # define __sec_comment "\"\n\t#\"" |
182 | #else |
183 | # define "\n\t#" |
184 | #endif |
185 | #define link_warning(symbol, msg) \ |
186 | __make_section_unallocated (".gnu.warning." #symbol) \ |
187 | static const char __evoke_link_warning_##symbol[] \ |
188 | __attribute__ ((used, section (".gnu.warning." #symbol __sec_comment))) \ |
189 | = msg; |
190 | #define libc_freeres_ptr(decl) \ |
191 | __make_section_unallocated ("__libc_freeres_ptrs, \"aw\", %nobits") \ |
192 | decl __attribute__ ((section ("__libc_freeres_ptrs" __sec_comment))) |
193 | #define __libc_freeres_fn_section \ |
194 | __attribute__ ((section ("__libc_freeres_fn"))) |
195 | |
196 | #define libc_freeres_fn(name) \ |
197 | static void name (void) __attribute_used__ __libc_freeres_fn_section; \ |
198 | text_set_element (__libc_subfreeres, name); \ |
199 | static void name (void) |
200 | |
201 | /* A canned warning for sysdeps/stub functions. */ |
202 | #define stub_warning(name) \ |
203 | __make_section_unallocated (".gnu.glibc-stub." #name) \ |
204 | link_warning (name, #name " is not implemented and will always fail") |
205 | |
206 | /* Warning for linking functions calling dlopen into static binaries. */ |
207 | #ifdef SHARED |
208 | #define static_link_warning(name) |
209 | #else |
210 | #define static_link_warning(name) static_link_warning1(name) |
211 | #define static_link_warning1(name) \ |
212 | link_warning(name, "Using '" #name "' in statically linked applications \ |
213 | requires at runtime the shared libraries from the glibc version used \ |
214 | for linking") |
215 | #endif |
216 | |
217 | /* Declare SYMBOL to be TYPE (`function' or `object') of SIZE bytes |
218 | alias to ORIGINAL, when the assembler supports such declarations |
219 | (such as in ELF). |
220 | This is only necessary when defining something in assembly, or playing |
221 | funny alias games where the size should be other than what the compiler |
222 | thinks it is. */ |
223 | #define declare_symbol_alias(symbol, original, type, size) \ |
224 | declare_symbol_alias_1 (symbol, original, type, size) |
225 | #ifdef __ASSEMBLER__ |
226 | # define declare_symbol_alias_1(symbol, original, type, size) \ |
227 | strong_alias (original, symbol); \ |
228 | .type C_SYMBOL_NAME (symbol), %##type; \ |
229 | .size C_SYMBOL_NAME (symbol), size |
230 | #else /* Not __ASSEMBLER__. */ |
231 | # define declare_symbol_alias_1(symbol, original, type, size) \ |
232 | asm (".globl " __SYMBOL_PREFIX #symbol \ |
233 | "\n\t" declare_symbol_alias_1_alias (symbol, original) \ |
234 | "\n\t.type " __SYMBOL_PREFIX #symbol ", " \ |
235 | "%" #type \ |
236 | "\n\t.size " __SYMBOL_PREFIX #symbol ", " #size); |
237 | # ifdef HAVE_ASM_SET_DIRECTIVE |
238 | # define declare_symbol_alias_1_alias(symbol, original) \ |
239 | ".set " __SYMBOL_PREFIX #symbol ", " __SYMBOL_PREFIX #original |
240 | # else |
241 | # define declare_symbol_alias_1_alias(symbol, original) \ |
242 | __SYMBOL_PREFIX #symbol " = " __SYMBOL_PREFIX #original |
243 | # endif /* HAVE_ASM_SET_DIRECTIVE */ |
244 | #endif /* __ASSEMBLER__ */ |
245 | |
246 | |
247 | /* |
248 | |
249 | */ |
250 | |
251 | /* Symbol set support macros. */ |
252 | |
253 | /* Make SYMBOL, which is in the text segment, an element of SET. */ |
254 | #define text_set_element(set, symbol) _elf_set_element(set, symbol) |
255 | /* Make SYMBOL, which is in the data segment, an element of SET. */ |
256 | #define data_set_element(set, symbol) _elf_set_element(set, symbol) |
257 | /* Make SYMBOL, which is in the bss segment, an element of SET. */ |
258 | #define bss_set_element(set, symbol) _elf_set_element(set, symbol) |
259 | |
260 | /* These are all done the same way in ELF. |
261 | There is a new section created for each set. */ |
262 | #ifdef SHARED |
263 | /* When building a shared library, make the set section writable, |
264 | because it will need to be relocated at run time anyway. */ |
265 | # define _elf_set_element(set, symbol) \ |
266 | static const void *__elf_set_##set##_element_##symbol##__ \ |
267 | __attribute__ ((used, section (#set))) = &(symbol) |
268 | #else |
269 | # define _elf_set_element(set, symbol) \ |
270 | static const void *const __elf_set_##set##_element_##symbol##__ \ |
271 | __attribute__ ((used, section (#set))) = &(symbol) |
272 | #endif |
273 | |
274 | /* Define SET as a symbol set. This may be required (it is in a.out) to |
275 | be able to use the set's contents. */ |
276 | #define symbol_set_define(set) symbol_set_declare(set) |
277 | |
278 | /* Declare SET for use in this module, if defined in another module. |
279 | In a shared library, this is always local to that shared object. |
280 | For static linking, the set might be wholly absent and so we use |
281 | weak references. */ |
282 | #define symbol_set_declare(set) \ |
283 | extern char const __start_##set[] __symbol_set_attribute; \ |
284 | extern char const __stop_##set[] __symbol_set_attribute; |
285 | #ifdef SHARED |
286 | # define __symbol_set_attribute attribute_hidden |
287 | #else |
288 | # define __symbol_set_attribute __attribute__ ((weak)) |
289 | #endif |
290 | |
291 | /* Return a pointer (void *const *) to the first element of SET. */ |
292 | #define symbol_set_first_element(set) ((void *const *) (&__start_##set)) |
293 | |
294 | /* Return true iff PTR (a void *const *) has been incremented |
295 | past the last element in SET. */ |
296 | #define symbol_set_end_p(set, ptr) ((ptr) >= (void *const *) &__stop_##set) |
297 | |
298 | /* Use symbol_version_reference to specify the version a symbol |
299 | reference should link to. Use symbol_version or |
300 | default_symbol_version for the definition of a versioned symbol. |
301 | The difference is that the latter is a no-op in non-shared |
302 | builds. */ |
303 | #ifdef __ASSEMBLER__ |
304 | # define symbol_version_reference(real, name, version) \ |
305 | .symver real, name##@##version |
306 | #else /* !__ASSEMBLER__ */ |
307 | # define symbol_version_reference(real, name, version) \ |
308 | __asm__ (".symver " #real "," #name "@" #version) |
309 | #endif |
310 | |
311 | #ifdef SHARED |
312 | # define symbol_version(real, name, version) \ |
313 | symbol_version_reference(real, name, version) |
314 | # define default_symbol_version(real, name, version) \ |
315 | _default_symbol_version(real, name, version) |
316 | # ifdef __ASSEMBLER__ |
317 | # define _default_symbol_version(real, name, version) \ |
318 | .symver real, name##@##@##version |
319 | # else |
320 | # define _default_symbol_version(real, name, version) \ |
321 | __asm__ (".symver " #real "," #name "@@" #version) |
322 | # endif |
323 | #else |
324 | # define symbol_version(real, name, version) |
325 | # define default_symbol_version(real, name, version) \ |
326 | strong_alias(real, name) |
327 | #endif |
328 | |
329 | #if defined SHARED || defined LIBC_NONSHARED |
330 | # define attribute_hidden __attribute__ ((visibility ("hidden"))) |
331 | #else |
332 | # define attribute_hidden |
333 | #endif |
334 | |
335 | #define attribute_tls_model_ie __attribute__ ((tls_model ("initial-exec"))) |
336 | |
337 | #define attribute_relro __attribute__ ((section (".data.rel.ro"))) |
338 | |
339 | |
340 | /* Used to disable stack protection in sensitive places, like ifunc |
341 | resolvers and early static TLS init. */ |
342 | #ifdef HAVE_CC_NO_STACK_PROTECTOR |
343 | # define inhibit_stack_protector \ |
344 | __attribute__ ((__optimize__ ("-fno-stack-protector"))) |
345 | #else |
346 | # define inhibit_stack_protector |
347 | #endif |
348 | |
349 | /* The following macros are used for PLT bypassing within libc.so |
350 | (and if needed other libraries similarly). |
351 | First of all, you need to have the function prototyped somewhere, |
352 | say in foo/foo.h: |
353 | |
354 | int foo (int __bar); |
355 | |
356 | If calls to foo within libc.so should always go to foo defined in libc.so, |
357 | then in include/foo.h you add: |
358 | |
359 | libc_hidden_proto (foo) |
360 | |
361 | line and after the foo function definition: |
362 | |
363 | int foo (int __bar) |
364 | { |
365 | return __bar; |
366 | } |
367 | libc_hidden_def (foo) |
368 | |
369 | or |
370 | |
371 | int foo (int __bar) |
372 | { |
373 | return __bar; |
374 | } |
375 | libc_hidden_weak (foo) |
376 | |
377 | Similarly for global data. If references to foo within libc.so should |
378 | always go to foo defined in libc.so, then in include/foo.h you add: |
379 | |
380 | libc_hidden_proto (foo) |
381 | |
382 | line and after foo's definition: |
383 | |
384 | int foo = INITIAL_FOO_VALUE; |
385 | libc_hidden_data_def (foo) |
386 | |
387 | or |
388 | |
389 | int foo = INITIAL_FOO_VALUE; |
390 | libc_hidden_data_weak (foo) |
391 | |
392 | If foo is normally just an alias (strong or weak) to some other function, |
393 | you should use the normal strong_alias first, then add libc_hidden_def |
394 | or libc_hidden_weak: |
395 | |
396 | int baz (int __bar) |
397 | { |
398 | return __bar; |
399 | } |
400 | strong_alias (baz, foo) |
401 | libc_hidden_weak (foo) |
402 | |
403 | If the function should be internal to multiple objects, say ld.so and |
404 | libc.so, the best way is to use: |
405 | |
406 | #if IS_IN (libc) || IS_IN (rtld) |
407 | hidden_proto (foo) |
408 | #endif |
409 | |
410 | in include/foo.h and the normal macros at all function definitions |
411 | depending on what DSO they belong to. |
412 | |
413 | If versioned_symbol macro is used to define foo, |
414 | libc_hidden_ver macro should be used, as in: |
415 | |
416 | int __real_foo (int __bar) |
417 | { |
418 | return __bar; |
419 | } |
420 | versioned_symbol (libc, __real_foo, foo, GLIBC_2_1); |
421 | libc_hidden_ver (__real_foo, foo) */ |
422 | |
423 | #if defined SHARED && !defined NO_HIDDEN |
424 | # ifndef __ASSEMBLER__ |
425 | # define __hidden_proto_hiddenattr(attrs...) \ |
426 | __attribute__ ((visibility ("hidden"), ##attrs)) |
427 | # define hidden_proto(name, attrs...) \ |
428 | __hidden_proto (name, , __GI_##name, ##attrs) |
429 | # define hidden_tls_proto(name, attrs...) \ |
430 | __hidden_proto (name, __thread, __GI_##name, ##attrs) |
431 | # define __hidden_proto(name, thread, internal, attrs...) \ |
432 | extern thread __typeof (name) name __asm__ (__hidden_asmname (#internal)) \ |
433 | __hidden_proto_hiddenattr (attrs); |
434 | # define __hidden_asmname(name) \ |
435 | __hidden_asmname1 (__USER_LABEL_PREFIX__, name) |
436 | # define __hidden_asmname1(prefix, name) __hidden_asmname2(prefix, name) |
437 | # define __hidden_asmname2(prefix, name) #prefix name |
438 | # define __hidden_ver1(local, internal, name) \ |
439 | extern __typeof (name) __EI_##name __asm__(__hidden_asmname (#internal)); \ |
440 | extern __typeof (name) __EI_##name \ |
441 | __attribute__((alias (__hidden_asmname (#local)))) |
442 | # define hidden_ver(local, name) __hidden_ver1(local, __GI_##name, name); |
443 | # define hidden_data_ver(local, name) hidden_ver(local, name) |
444 | # define hidden_def(name) __hidden_ver1(__GI_##name, name, name); |
445 | # define hidden_data_def(name) hidden_def(name) |
446 | # define hidden_weak(name) \ |
447 | __hidden_ver1(__GI_##name, name, name) __attribute__((weak)); |
448 | # define hidden_data_weak(name) hidden_weak(name) |
449 | # define hidden_nolink(name, lib, version) \ |
450 | __hidden_nolink1 (__GI_##name, __EI_##name, name, VERSION_##lib##_##version) |
451 | # define __hidden_nolink1(local, internal, name, version) \ |
452 | __hidden_nolink2 (local, internal, name, version) |
453 | # define __hidden_nolink2(local, internal, name, version) \ |
454 | extern __typeof (name) internal __attribute__ ((alias (#local))); \ |
455 | __hidden_nolink3 (local, internal, #name "@" #version) |
456 | # define __hidden_nolink3(local, internal, vername) \ |
457 | __asm__ (".symver " #internal ", " vername); |
458 | # else |
459 | /* For assembly, we need to do the opposite of what we do in C: |
460 | in assembly gcc __REDIRECT stuff is not in place, so functions |
461 | are defined by its normal name and we need to create the |
462 | __GI_* alias to it, in C __REDIRECT causes the function definition |
463 | to use __GI_* name and we need to add alias to the real name. |
464 | There is no reason to use hidden_weak over hidden_def in assembly, |
465 | but we provide it for consistency with the C usage. |
466 | hidden_proto doesn't make sense for assembly but the equivalent |
467 | is to call via the HIDDEN_JUMPTARGET macro instead of JUMPTARGET. */ |
468 | # define hidden_def(name) strong_alias (name, __GI_##name) |
469 | # define hidden_weak(name) hidden_def (name) |
470 | # define hidden_ver(local, name) strong_alias (local, __GI_##name) |
471 | # define hidden_data_def(name) strong_data_alias (name, __GI_##name) |
472 | # define hidden_data_weak(name) hidden_data_def (name) |
473 | # define hidden_data_ver(local, name) strong_data_alias (local, __GI_##name) |
474 | # define HIDDEN_JUMPTARGET(name) __GI_##name |
475 | # endif |
476 | #else |
477 | # ifndef __ASSEMBLER__ |
478 | # define hidden_proto(name, attrs...) |
479 | # define hidden_tls_proto(name, attrs...) |
480 | # else |
481 | # define HIDDEN_JUMPTARGET(name) JUMPTARGET(name) |
482 | # endif /* Not __ASSEMBLER__ */ |
483 | # define hidden_weak(name) |
484 | # define hidden_def(name) |
485 | # define hidden_ver(local, name) |
486 | # define hidden_data_weak(name) |
487 | # define hidden_data_def(name) |
488 | # define hidden_data_ver(local, name) |
489 | # define hidden_nolink(name, lib, version) |
490 | #endif |
491 | |
492 | #if IS_IN (libc) |
493 | # define libc_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) |
494 | # define libc_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs) |
495 | # define libc_hidden_def(name) hidden_def (name) |
496 | # define libc_hidden_weak(name) hidden_weak (name) |
497 | # ifdef LINK_OBSOLETE_RPC |
498 | /* libc_hidden_nolink_sunrpc should only get used in sunrpc code. */ |
499 | # define libc_hidden_nolink_sunrpc(name, version) hidden_def (name) |
500 | # else |
501 | # define libc_hidden_nolink_sunrpc(name, version) hidden_nolink (name, libc, version) |
502 | # endif |
503 | # define libc_hidden_ver(local, name) hidden_ver (local, name) |
504 | # define libc_hidden_data_def(name) hidden_data_def (name) |
505 | # define libc_hidden_data_weak(name) hidden_data_weak (name) |
506 | # define libc_hidden_data_ver(local, name) hidden_data_ver (local, name) |
507 | #else |
508 | # define libc_hidden_proto(name, attrs...) |
509 | # define libc_hidden_tls_proto(name, attrs...) |
510 | # define libc_hidden_def(name) |
511 | # define libc_hidden_weak(name) |
512 | # define libc_hidden_ver(local, name) |
513 | # define libc_hidden_data_def(name) |
514 | # define libc_hidden_data_weak(name) |
515 | # define libc_hidden_data_ver(local, name) |
516 | #endif |
517 | |
518 | #if IS_IN (rtld) |
519 | # define rtld_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) |
520 | # define rtld_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs) |
521 | # define rtld_hidden_def(name) hidden_def (name) |
522 | # define rtld_hidden_weak(name) hidden_weak (name) |
523 | # define rtld_hidden_ver(local, name) hidden_ver (local, name) |
524 | # define rtld_hidden_data_def(name) hidden_data_def (name) |
525 | # define rtld_hidden_data_weak(name) hidden_data_weak (name) |
526 | # define rtld_hidden_data_ver(local, name) hidden_data_ver (local, name) |
527 | #else |
528 | # define rtld_hidden_proto(name, attrs...) |
529 | # define rtld_hidden_tls_proto(name, attrs...) |
530 | # define rtld_hidden_def(name) |
531 | # define rtld_hidden_weak(name) |
532 | # define rtld_hidden_ver(local, name) |
533 | # define rtld_hidden_data_def(name) |
534 | # define rtld_hidden_data_weak(name) |
535 | # define rtld_hidden_data_ver(local, name) |
536 | #endif |
537 | |
538 | #if IS_IN (libm) |
539 | # define libm_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) |
540 | # define libm_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs) |
541 | # define libm_hidden_def(name) hidden_def (name) |
542 | # define libm_hidden_weak(name) hidden_weak (name) |
543 | # define libm_hidden_ver(local, name) hidden_ver (local, name) |
544 | # define libm_hidden_data_def(name) hidden_data_def (name) |
545 | # define libm_hidden_data_weak(name) hidden_data_weak (name) |
546 | # define libm_hidden_data_ver(local, name) hidden_data_ver (local, name) |
547 | #else |
548 | # define libm_hidden_proto(name, attrs...) |
549 | # define libm_hidden_tls_proto(name, attrs...) |
550 | # define libm_hidden_def(name) |
551 | # define libm_hidden_weak(name) |
552 | # define libm_hidden_ver(local, name) |
553 | # define libm_hidden_data_def(name) |
554 | # define libm_hidden_data_weak(name) |
555 | # define libm_hidden_data_ver(local, name) |
556 | #endif |
557 | |
558 | #if IS_IN (libmvec) |
559 | # define libmvec_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) |
560 | # define libmvec_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs) |
561 | # define libmvec_hidden_def(name) hidden_def (name) |
562 | # define libmvec_hidden_weak(name) hidden_weak (name) |
563 | # define libmvec_hidden_ver(local, name) hidden_ver (local, name) |
564 | # define libmvec_hidden_data_def(name) hidden_data_def (name) |
565 | # define libmvec_hidden_data_weak(name) hidden_data_weak (name) |
566 | # define libmvec_hidden_data_ver(local, name) hidden_data_ver (local, name) |
567 | #else |
568 | # define libmvec_hidden_proto(name, attrs...) |
569 | # define libmvec_hidden_tls_proto(name, attrs...) |
570 | # define libmvec_hidden_def(name) |
571 | # define libmvec_hidden_weak(name) |
572 | # define libmvec_hidden_ver(local, name) |
573 | # define libmvec_hidden_data_def(name) |
574 | # define libmvec_hidden_data_weak(name) |
575 | # define libmvec_hidden_data_ver(local, name) |
576 | #endif |
577 | |
578 | #if IS_IN (libresolv) |
579 | # define libresolv_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) |
580 | # define libresolv_hidden_tls_proto(name, attrs...) \ |
581 | hidden_tls_proto (name, ##attrs) |
582 | # define libresolv_hidden_def(name) hidden_def (name) |
583 | # define libresolv_hidden_weak(name) hidden_weak (name) |
584 | # define libresolv_hidden_ver(local, name) hidden_ver (local, name) |
585 | # define libresolv_hidden_data_def(name) hidden_data_def (name) |
586 | # define libresolv_hidden_data_weak(name) hidden_data_weak (name) |
587 | # define libresolv_hidden_data_ver(local, name) hidden_data_ver (local, name) |
588 | #else |
589 | # define libresolv_hidden_proto(name, attrs...) |
590 | # define libresolv_hidden_tls_proto(name, attrs...) |
591 | # define libresolv_hidden_def(name) |
592 | # define libresolv_hidden_weak(name) |
593 | # define libresolv_hidden_ver(local, name) |
594 | # define libresolv_hidden_data_def(name) |
595 | # define libresolv_hidden_data_weak(name) |
596 | # define libresolv_hidden_data_ver(local, name) |
597 | #endif |
598 | |
599 | #if IS_IN (librt) |
600 | # define librt_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) |
601 | # define librt_hidden_tls_proto(name, attrs...) \ |
602 | hidden_tls_proto (name, ##attrs) |
603 | # define librt_hidden_def(name) hidden_def (name) |
604 | # define librt_hidden_weak(name) hidden_weak (name) |
605 | # define librt_hidden_ver(local, name) hidden_ver (local, name) |
606 | # define librt_hidden_data_def(name) hidden_data_def (name) |
607 | # define librt_hidden_data_weak(name) hidden_data_weak (name) |
608 | # define librt_hidden_data_ver(local, name) hidden_data_ver (local, name) |
609 | #else |
610 | # define librt_hidden_proto(name, attrs...) |
611 | # define librt_hidden_tls_proto(name, attrs...) |
612 | # define librt_hidden_def(name) |
613 | # define librt_hidden_weak(name) |
614 | # define librt_hidden_ver(local, name) |
615 | # define librt_hidden_data_def(name) |
616 | # define librt_hidden_data_weak(name) |
617 | # define librt_hidden_data_ver(local, name) |
618 | #endif |
619 | |
620 | #if IS_IN (libdl) |
621 | # define libdl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) |
622 | # define libdl_hidden_tls_proto(name, attrs...) \ |
623 | hidden_tls_proto (name, ##attrs) |
624 | # define libdl_hidden_def(name) hidden_def (name) |
625 | # define libdl_hidden_weak(name) hidden_weak (name) |
626 | # define libdl_hidden_ver(local, name) hidden_ver (local, name) |
627 | # define libdl_hidden_data_def(name) hidden_data_def (name) |
628 | # define libdl_hidden_data_weak(name) hidden_data_weak (name) |
629 | # define libdl_hidden_data_ver(local, name) hidden_data_ver (local, name) |
630 | #else |
631 | # define libdl_hidden_proto(name, attrs...) |
632 | # define libdl_hidden_tls_proto(name, attrs...) |
633 | # define libdl_hidden_def(name) |
634 | # define libdl_hidden_weak(name) |
635 | # define libdl_hidden_ver(local, name) |
636 | # define libdl_hidden_data_def(name) |
637 | # define libdl_hidden_data_weak(name) |
638 | # define libdl_hidden_data_ver(local, name) |
639 | #endif |
640 | |
641 | #if IS_IN (libnss_files) |
642 | # define libnss_files_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) |
643 | # define libnss_files_hidden_tls_proto(name, attrs...) \ |
644 | hidden_tls_proto (name, ##attrs) |
645 | # define libnss_files_hidden_def(name) hidden_def (name) |
646 | # define libnss_files_hidden_weak(name) hidden_weak (name) |
647 | # define libnss_files_hidden_ver(local, name) hidden_ver (local, name) |
648 | # define libnss_files_hidden_data_def(name) hidden_data_def (name) |
649 | # define libnss_files_hidden_data_weak(name) hidden_data_weak (name) |
650 | # define libnss_files_hidden_data_ver(local, name) hidden_data_ver(local, name) |
651 | #else |
652 | # define libnss_files_hidden_proto(name, attrs...) |
653 | # define libnss_files_hidden_tls_proto(name, attrs...) |
654 | # define libnss_files_hidden_def(name) |
655 | # define libnss_files_hidden_weak(name) |
656 | # define libnss_files_hidden_ver(local, name) |
657 | # define libnss_files_hidden_data_def(name) |
658 | # define libnss_files_hidden_data_weak(name) |
659 | # define libnss_files_hidden_data_ver(local, name) |
660 | #endif |
661 | |
662 | #if IS_IN (libnsl) |
663 | # define libnsl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) |
664 | # define libnsl_hidden_tls_proto(name, attrs...) \ |
665 | hidden_tls_proto (name, ##attrs) |
666 | # define libnsl_hidden_def(name) hidden_def (name) |
667 | # define libnsl_hidden_weak(name) hidden_weak (name) |
668 | # define libnsl_hidden_ver(local, name) hidden_ver (local, name) |
669 | # define libnsl_hidden_data_def(name) hidden_data_def (name) |
670 | # define libnsl_hidden_data_weak(name) hidden_data_weak (name) |
671 | # define libnsl_hidden_data_ver(local, name) hidden_data_ver (local, name) |
672 | #else |
673 | # define libnsl_hidden_proto(name, attrs...) |
674 | # define libnsl_hidden_tls_proto(name, attrs...) |
675 | # define libnsl_hidden_def(name) |
676 | # define libnsl_hidden_weak(name) |
677 | # define libnsl_hidden_ver(local, name) |
678 | # define libnsl_hidden_data_def(name) |
679 | # define libnsl_hidden_data_weak(name) |
680 | # define libnsl_hidden_data_ver(local, name) |
681 | #endif |
682 | |
683 | #if IS_IN (libnss_nisplus) |
684 | # define libnss_nisplus_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) |
685 | # define libnss_nisplus_hidden_tls_proto(name, attrs...) \ |
686 | hidden_tls_proto (name, ##attrs) |
687 | # define libnss_nisplus_hidden_def(name) hidden_def (name) |
688 | # define libnss_nisplus_hidden_weak(name) hidden_weak (name) |
689 | # define libnss_nisplus_hidden_ver(local, name) hidden_ver (local, name) |
690 | # define libnss_nisplus_hidden_data_def(name) hidden_data_def (name) |
691 | # define libnss_nisplus_hidden_data_weak(name) hidden_data_weak (name) |
692 | # define libnss_nisplus_hidden_data_ver(local, name) hidden_data_ver (local, name) |
693 | #else |
694 | # define libnss_nisplus_hidden_proto(name, attrs...) |
695 | # define libnss_nisplus_hidden_tls_proto(name, attrs...) |
696 | # define libnss_nisplus_hidden_def(name) |
697 | # define libnss_nisplus_hidden_weak(name) |
698 | # define libnss_nisplus_hidden_ver(local, name) |
699 | # define libnss_nisplus_hidden_data_def(name) |
700 | # define libnss_nisplus_hidden_data_weak(name) |
701 | # define libnss_nisplus_hidden_data_ver(local, name) |
702 | #endif |
703 | |
704 | #define libc_hidden_builtin_proto(name, attrs...) libc_hidden_proto (name, ##attrs) |
705 | #define libc_hidden_builtin_def(name) libc_hidden_def (name) |
706 | #define libc_hidden_builtin_weak(name) libc_hidden_weak (name) |
707 | #define libc_hidden_builtin_ver(local, name) libc_hidden_ver (local, name) |
708 | #ifdef __ASSEMBLER__ |
709 | # define HIDDEN_BUILTIN_JUMPTARGET(name) HIDDEN_JUMPTARGET(name) |
710 | #endif |
711 | |
712 | #if IS_IN (libutil) |
713 | # define libutil_hidden_proto(name, attrs...) hidden_proto (name, ##attrs) |
714 | # define libutil_hidden_tls_proto(name, attrs...) \ |
715 | hidden_tls_proto (name, ##attrs) |
716 | # define libutil_hidden_def(name) hidden_def (name) |
717 | # define libutil_hidden_weak(name) hidden_weak (name) |
718 | # define libutil_hidden_ver(local, name) hidden_ver (local, name) |
719 | # define libutil_hidden_data_def(name) hidden_data_def (name) |
720 | # define libutil_hidden_data_weak(name) hidden_data_weak (name) |
721 | # define libutil_hidden_data_ver(local, name) hidden_data_ver (local, name) |
722 | #else |
723 | # define libutil_hidden_proto(name, attrs...) |
724 | # define libutil_hidden_tls_proto(name, attrs...) |
725 | # define libutil_hidden_def(name) |
726 | # define libutil_hidden_weak(name) |
727 | # define libutil_hidden_ver(local, name) |
728 | # define libutil_hidden_data_def(name) |
729 | # define libutil_hidden_data_weak(name) |
730 | # define libutil_hidden_data_ver(local, name) |
731 | #endif |
732 | |
733 | /* Get some dirty hacks. */ |
734 | #include <symbol-hacks.h> |
735 | |
736 | /* Move compatibility symbols out of the way by placing them all in a |
737 | special section. */ |
738 | #ifndef __ASSEMBLER__ |
739 | # define attribute_compat_text_section \ |
740 | __attribute__ ((section (".text.compat"))) |
741 | # define attribute_compat_data_section \ |
742 | __attribute__ ((section (".data.compat"))) |
743 | #else |
744 | # define compat_text_section .section ".text.compat", "ax"; |
745 | # define compat_data_section .section ".data.compat", "aw"; |
746 | #endif |
747 | |
748 | /* Helper / base macros for indirect function symbols. */ |
749 | #define __ifunc_resolver(type_name, name, expr, arg, init, classifier) \ |
750 | classifier inhibit_stack_protector void *name##_ifunc (arg) \ |
751 | { \ |
752 | init (); \ |
753 | __typeof (type_name) *res = expr; \ |
754 | return res; \ |
755 | } |
756 | |
757 | #ifdef HAVE_GCC_IFUNC |
758 | # define __ifunc(type_name, name, expr, arg, init) \ |
759 | extern __typeof (type_name) name __attribute__ \ |
760 | ((ifunc (#name "_ifunc"))); \ |
761 | __ifunc_resolver (type_name, name, expr, arg, init, static) |
762 | |
763 | # define __ifunc_hidden(type_name, name, expr, arg, init) \ |
764 | __ifunc (type_name, name, expr, arg, init) |
765 | #else |
766 | /* Gcc does not support __attribute__ ((ifunc (...))). Use the old behaviour |
767 | as fallback. But keep in mind that the debug information for the ifunc |
768 | resolver functions is not correct. It contains the ifunc'ed function as |
769 | DW_AT_linkage_name. E.g. lldb uses this field and an inferior function |
770 | call of the ifunc'ed function will fail due to "no matching function for |
771 | call to ..." because the ifunc'ed function and the resolver function have |
772 | different signatures. (Gcc support is disabled at least on a ppc64le |
773 | Ubuntu 14.04 system.) */ |
774 | |
775 | # define __ifunc(type_name, name, expr, arg, init) \ |
776 | extern __typeof (type_name) name; \ |
777 | void *name##_ifunc (arg) __asm__ (#name); \ |
778 | __ifunc_resolver (type_name, name, expr, arg, init,) \ |
779 | __asm__ (".type " #name ", %gnu_indirect_function"); |
780 | |
781 | # define __ifunc_hidden(type_name, name, expr, arg, init) \ |
782 | extern __typeof (type_name) __libc_##name; \ |
783 | __ifunc (type_name, __libc_##name, expr, arg, init) \ |
784 | strong_alias (__libc_##name, name); |
785 | #endif /* !HAVE_GCC_IFUNC */ |
786 | |
787 | /* The following macros are used for indirect function symbols in libc.so. |
788 | First of all, you need to have the function prototyped somewhere, |
789 | say in foo.h: |
790 | |
791 | int foo (int __bar); |
792 | |
793 | If you have an implementation for foo which e.g. uses a special hardware |
794 | feature which isn't available on all machines where this libc.so will be |
795 | used but decideable if available at runtime e.g. via hwcaps, you can provide |
796 | two or multiple implementations of foo: |
797 | |
798 | int __foo_default (int __bar) |
799 | { |
800 | return __bar; |
801 | } |
802 | |
803 | int __foo_special (int __bar) |
804 | { |
805 | return __bar; |
806 | } |
807 | |
808 | If your function foo has no libc_hidden_proto (foo) defined for PLT |
809 | bypassing, you can use: |
810 | |
811 | #define INIT_ARCH() unsigned long int hwcap = __GLRO(dl_hwcap); |
812 | |
813 | libc_ifunc (foo, (hwcap & HWCAP_SPECIAL) ? __foo_special : __foo_default); |
814 | |
815 | This will define a resolver function for foo which returns __foo_special or |
816 | __foo_default depending on your specified expression. Please note that you |
817 | have to define a macro function INIT_ARCH before using libc_ifunc macro as |
818 | it is called by the resolver function before evaluating the specified |
819 | expression. In this example it is used to prepare the hwcap variable. |
820 | The resolver function is assigned to an ifunc'ed symbol foo. Calls to foo |
821 | from inside or outside of libc.so will be indirected by a PLT call. |
822 | |
823 | If your function foo has a libc_hidden_proto (foo) defined for PLT bypassing |
824 | and calls to foo within libc.so should always go to one specific |
825 | implementation of foo e.g. __foo_default then you have to add: |
826 | |
827 | __hidden_ver1 (__foo_default, __GI_foo, __foo_default); |
828 | |
829 | or a tweaked definition of libc_hidden_def macro after the __foo_default |
830 | function definition. Calls to foo within libc.so will always go directly to |
831 | __foo_default. Calls to foo from outside libc.so will be indirected by a |
832 | PLT call to ifunc'ed symbol foo which you have to define in a separate |
833 | compile unit: |
834 | |
835 | #define foo __redirect_foo |
836 | #include <foo.h> |
837 | #undef foo |
838 | |
839 | extern __typeof (__redirect_foo) __foo_default attribute_hidden; |
840 | extern __typeof (__redirect_foo) __foo_special attribute_hidden; |
841 | |
842 | libc_ifunc_redirected (__redirect_foo, foo, |
843 | (hwcap & HWCAP_SPECIAL) |
844 | ? __foo_special |
845 | : __foo_default); |
846 | |
847 | This will define the ifunc'ed symbol foo like above. The redirection of foo |
848 | in header file is needed to omit an additional defintion of __GI_foo which |
849 | would end in a linker error while linking libc.so. You have to specify |
850 | __redirect_foo as first parameter which is used within libc_ifunc_redirected |
851 | macro in conjunction with typeof to define the ifunc'ed symbol foo. |
852 | |
853 | If your function foo has a libc_hidden_proto (foo) defined and calls to foo |
854 | within or from outside libc.so should go via ifunc'ed symbol, then you have |
855 | to use: |
856 | |
857 | libc_ifunc_hidden (foo, foo, |
858 | (hwcap & HWCAP_SPECIAL) |
859 | ? __foo_special |
860 | : __foo_default); |
861 | libc_hidden_def (foo) |
862 | |
863 | The first parameter foo of libc_ifunc_hidden macro is used in the same way |
864 | as for libc_ifunc_redirected macro. */ |
865 | |
866 | #define libc_ifunc(name, expr) __ifunc (name, name, expr, void, INIT_ARCH) |
867 | |
868 | #define libc_ifunc_redirected(redirected_name, name, expr) \ |
869 | __ifunc (redirected_name, name, expr, void, INIT_ARCH) |
870 | |
871 | #define libc_ifunc_hidden(redirected_name, name, expr) \ |
872 | __ifunc_hidden (redirected_name, name, expr, void, INIT_ARCH) |
873 | |
874 | /* The body of the function is supposed to use __get_cpu_features |
875 | which will, if necessary, initialize the data first. */ |
876 | #define libm_ifunc_init() |
877 | #define libm_ifunc(name, expr) \ |
878 | __ifunc (name, name, expr, void, libm_ifunc_init) |
879 | |
880 | /* Add the compiler optimization to inhibit loop transformation to library |
881 | calls. This is used to avoid recursive calls in memset and memmove |
882 | default implementations. */ |
883 | #ifdef HAVE_CC_INHIBIT_LOOP_TO_LIBCALL |
884 | # define inhibit_loop_to_libcall \ |
885 | __attribute__ ((__optimize__ ("-fno-tree-loop-distribute-patterns"))) |
886 | #else |
887 | # define inhibit_loop_to_libcall |
888 | #endif |
889 | |
890 | #endif /* libc-symbols.h */ |
891 | |