1 /* Data structure for communication from the run-time dynamic linker for
2 loaded ELF shared objects.
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 _PRIVATE_LINK_H
21 #define _PRIVATE_LINK_H 1
22
23 #ifdef _LINK_H
24 # error this should be impossible
25 #endif
26
27 # ifndef _ISOMAC
28 /* Get most of the contents from the public header, but we define a
29 different `struct link_map' type for private use. The la_objopen
30 prototype uses the type, so we have to declare it separately. */
31 # define link_map link_map_public
32 # define la_objopen la_objopen_wrongproto
33 # endif
34
35 #include <elf/link.h>
36
37 # ifndef _ISOMAC
38
39 #undef link_map
40 #undef la_objopen
41
42 struct link_map;
43 extern unsigned int la_objopen (struct link_map *__map, Lmid_t __lmid,
44 uintptr_t *__cookie);
45
46 #include <stdint.h>
47 #include <stddef.h>
48 #include <linkmap.h>
49 #include <dl-fileid.h>
50 #include <dl-lookupcfg.h>
51 #include <tls.h>
52 #include <libc-lock.h>
53
54
55 /* Some internal data structures of the dynamic linker used in the
56 linker map. We only provide forward declarations. */
57 struct libname_list;
58 struct r_found_version;
59 struct r_search_path_elem;
60
61 /* Forward declaration. */
62 struct link_map;
63
64 /* Structure to describe a single list of scope elements. The lookup
65 functions get passed an array of pointers to such structures. */
66 struct r_scope_elem
67 {
68 /* Array of maps for the scope. */
69 struct link_map **r_list;
70 /* Number of entries in the scope. */
71 unsigned int r_nlist;
72 };
73
74
75 /* Structure to record search path and allocation mechanism. */
76 struct r_search_path_struct
77 {
78 struct r_search_path_elem **dirs;
79 int malloced;
80 };
81
82 /* Search path information computed by _dl_init_paths. */
83 extern struct r_search_path_struct __rtld_search_dirs attribute_hidden;
84 extern struct r_search_path_struct __rtld_env_path_list attribute_hidden;
85
86 /* Structure describing a loaded shared object. The `l_next' and `l_prev'
87 members form a chain of all the shared objects loaded at startup.
88
89 These data structures exist in space used by the run-time dynamic linker;
90 modifying them may have disastrous results.
91
92 This data structure might change in future, if necessary. User-level
93 programs must avoid defining objects of this type. */
94
95 struct link_map
96 {
97 /* These first few members are part of the protocol with the debugger.
98 This is the same format used in SVR4. */
99
100 ElfW(Addr) l_addr; /* Difference between the address in the ELF
101 file and the addresses in memory. */
102 char *l_name; /* Absolute file name object was found in. */
103 ElfW(Dyn) *l_ld; /* Dynamic section of the shared object. */
104 struct link_map *l_next, *l_prev; /* Chain of loaded objects. */
105
106 /* All following members are internal to the dynamic linker.
107 They may change without notice. */
108
109 /* This is an element which is only ever different from a pointer to
110 the very same copy of this type for ld.so when it is used in more
111 than one namespace. */
112 struct link_map *l_real;
113
114 /* Number of the namespace this link map belongs to. */
115 Lmid_t l_ns;
116
117 struct libname_list *l_libname;
118 /* Indexed pointers to dynamic section.
119 [0,DT_NUM) are indexed by the processor-independent tags.
120 [DT_NUM,DT_NUM+DT_THISPROCNUM) are indexed by the tag minus DT_LOPROC.
121 [DT_NUM+DT_THISPROCNUM,DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM) are
122 indexed by DT_VERSIONTAGIDX(tagvalue).
123 [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM,
124 DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM) are indexed by
125 DT_EXTRATAGIDX(tagvalue).
126 [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM,
127 DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM) are
128 indexed by DT_VALTAGIDX(tagvalue) and
129 [DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM,
130 DT_NUM+DT_THISPROCNUM+DT_VERSIONTAGNUM+DT_EXTRANUM+DT_VALNUM+DT_ADDRNUM)
131 are indexed by DT_ADDRTAGIDX(tagvalue), see <elf.h>. */
132
133 ElfW(Dyn) *l_info[DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGNUM
134 + DT_EXTRANUM + DT_VALNUM + DT_ADDRNUM];
135 const ElfW(Phdr) *l_phdr; /* Pointer to program header table in core. */
136 ElfW(Addr) l_entry; /* Entry point location. */
137 ElfW(Half) l_phnum; /* Number of program header entries. */
138 ElfW(Half) l_ldnum; /* Number of dynamic segment entries. */
139
140 /* Array of DT_NEEDED dependencies and their dependencies, in
141 dependency order for symbol lookup (with and without
142 duplicates). There is no entry before the dependencies have
143 been loaded. */
144 struct r_scope_elem l_searchlist;
145
146 /* We need a special searchlist to process objects marked with
147 DT_SYMBOLIC. */
148 struct r_scope_elem l_symbolic_searchlist;
149
150 /* Dependent object that first caused this object to be loaded. */
151 struct link_map *l_loader;
152
153 /* Array with version names. */
154 struct r_found_version *l_versions;
155 unsigned int l_nversions;
156
157 /* Symbol hash table. */
158 Elf_Symndx l_nbuckets;
159 Elf32_Word l_gnu_bitmask_idxbits;
160 Elf32_Word l_gnu_shift;
161 const ElfW(Addr) *l_gnu_bitmask;
162 union
163 {
164 const Elf32_Word *l_gnu_buckets;
165 const Elf_Symndx *l_chain;
166 };
167 union
168 {
169 const Elf32_Word *l_gnu_chain_zero;
170 const Elf_Symndx *l_buckets;
171 };
172
173 unsigned int l_direct_opencount; /* Reference count for dlopen/dlclose. */
174 enum /* Where this object came from. */
175 {
176 lt_executable, /* The main executable program. */
177 lt_library, /* Library needed by main executable. */
178 lt_loaded /* Extra run-time loaded shared object. */
179 } l_type:2;
180 unsigned int l_dt_relr_ref:1; /* Nonzero if GLIBC_ABI_DT_RELR is
181 referenced. */
182 unsigned int l_relocated:1; /* Nonzero if object's relocations done. */
183 unsigned int l_init_called:1; /* Nonzero if DT_INIT function called. */
184 unsigned int l_global:1; /* Nonzero if object in _dl_global_scope. */
185 unsigned int l_reserved:2; /* Reserved for internal use. */
186 unsigned int l_main_map:1; /* Nonzero for the map of the main program. */
187 unsigned int l_visited:1; /* Used internally for map dependency
188 graph traversal. */
189 unsigned int l_map_used:1; /* These two bits are used during traversal */
190 unsigned int l_map_done:1; /* of maps in _dl_close_worker. */
191 unsigned int l_phdr_allocated:1; /* Nonzero if the data structure pointed
192 to by `l_phdr' is allocated. */
193 unsigned int l_soname_added:1; /* Nonzero if the SONAME is for sure in
194 the l_libname list. */
195 unsigned int l_faked:1; /* Nonzero if this is a faked descriptor
196 without associated file. */
197 unsigned int l_need_tls_init:1; /* Nonzero if GL(dl_init_static_tls)
198 should be called on this link map
199 when relocation finishes. */
200 unsigned int l_auditing:1; /* Nonzero if the DSO is used in auditing. */
201 unsigned int l_audit_any_plt:1; /* Nonzero if at least one audit module
202 is interested in the PLT interception.*/
203 unsigned int l_removed:1; /* Nozero if the object cannot be used anymore
204 since it is removed. */
205 unsigned int l_contiguous:1; /* Nonzero if inter-segment holes are
206 mprotected or if no holes are present at
207 all. */
208 unsigned int l_free_initfini:1; /* Nonzero if l_initfini can be
209 freed, ie. not allocated with
210 the dummy malloc in ld.so. */
211 unsigned int l_ld_readonly:1; /* Nonzero if dynamic section is readonly. */
212 unsigned int l_find_object_processed:1; /* Zero if _dl_find_object_update
213 needs to process this
214 lt_library map. */
215
216 /* NODELETE status of the map. Only valid for maps of type
217 lt_loaded. Lazy binding sets l_nodelete_active directly,
218 potentially from signal handlers. Initial loading of an
219 DF_1_NODELETE object set l_nodelete_pending. Relocation may
220 set l_nodelete_pending as well. l_nodelete_pending maps are
221 promoted to l_nodelete_active status in the final stages of
222 dlopen, prior to calling ELF constructors. dlclose only
223 refuses to unload l_nodelete_active maps, the pending status is
224 ignored. */
225 bool l_nodelete_active;
226 bool l_nodelete_pending;
227
228 #include <link_map.h>
229
230 /* Collected information about own RPATH directories. */
231 struct r_search_path_struct l_rpath_dirs;
232
233 /* Collected results of relocation while profiling. */
234 struct reloc_result
235 {
236 DL_FIXUP_VALUE_TYPE addr;
237 struct link_map *bound;
238 unsigned int boundndx;
239 uint32_t enterexit;
240 unsigned int flags;
241 /* CONCURRENCY NOTE: This is used to guard the concurrent initialization
242 of the relocation result across multiple threads. See the more
243 detailed notes in elf/dl-runtime.c. */
244 unsigned int init;
245 } *l_reloc_result;
246
247 /* Pointer to the version information if available. */
248 ElfW(Versym) *l_versyms;
249
250 /* String specifying the path where this object was found. */
251 const char *l_origin;
252
253 /* Start and finish of memory map for this object. l_map_start
254 need not be the same as l_addr. */
255 ElfW(Addr) l_map_start, l_map_end;
256 /* End of the executable part of the mapping. */
257 ElfW(Addr) l_text_end;
258
259 /* Default array for 'l_scope'. */
260 struct r_scope_elem *l_scope_mem[4];
261 /* Size of array allocated for 'l_scope'. */
262 size_t l_scope_max;
263 /* This is an array defining the lookup scope for this link map.
264 There are initially at most three different scope lists. */
265 struct r_scope_elem **l_scope;
266
267 /* A similar array, this time only with the local scope. This is
268 used occasionally. */
269 struct r_scope_elem *l_local_scope[2];
270
271 /* This information is kept to check for sure whether a shared
272 object is the same as one already loaded. */
273 struct r_file_id l_file_id;
274
275 /* Collected information about own RUNPATH directories. */
276 struct r_search_path_struct l_runpath_dirs;
277
278 /* List of object in order of the init and fini calls. */
279 struct link_map **l_initfini;
280
281 /* List of the dependencies introduced through symbol binding. */
282 struct link_map_reldeps
283 {
284 unsigned int act;
285 struct link_map *list[];
286 } *l_reldeps;
287 unsigned int l_reldepsmax;
288
289 /* Nonzero if the DSO is used. */
290 unsigned int l_used;
291
292 /* Various flag words. */
293 ElfW(Word) l_feature_1;
294 ElfW(Word) l_flags_1;
295 ElfW(Word) l_flags;
296
297 /* Temporarily used in `dl_close'. */
298 int l_idx;
299
300 struct link_map_machine l_mach;
301
302 struct
303 {
304 const ElfW(Sym) *sym;
305 int type_class;
306 struct link_map *value;
307 const ElfW(Sym) *ret;
308 } l_lookup_cache;
309
310 /* Thread-local storage related info. */
311
312 /* Start of the initialization image. */
313 void *l_tls_initimage;
314 /* Size of the initialization image. */
315 size_t l_tls_initimage_size;
316 /* Size of the TLS block. */
317 size_t l_tls_blocksize;
318 /* Alignment requirement of the TLS block. */
319 size_t l_tls_align;
320 /* Offset of first byte module alignment. */
321 size_t l_tls_firstbyte_offset;
322 #ifndef NO_TLS_OFFSET
323 # define NO_TLS_OFFSET 0
324 #endif
325 #ifndef FORCED_DYNAMIC_TLS_OFFSET
326 # if NO_TLS_OFFSET == 0
327 # define FORCED_DYNAMIC_TLS_OFFSET -1
328 # elif NO_TLS_OFFSET == -1
329 # define FORCED_DYNAMIC_TLS_OFFSET -2
330 # else
331 # error "FORCED_DYNAMIC_TLS_OFFSET is not defined"
332 # endif
333 #endif
334 /* For objects present at startup time: offset in the static TLS block. */
335 ptrdiff_t l_tls_offset;
336 /* Index of the module in the dtv array. */
337 size_t l_tls_modid;
338
339 /* Number of thread_local objects constructed by this DSO. This is
340 atomically accessed and modified and is not always protected by the load
341 lock. See also: CONCURRENCY NOTES in cxa_thread_atexit_impl.c. */
342 size_t l_tls_dtor_count;
343
344 /* Information used to change permission after the relocations are
345 done. */
346 ElfW(Addr) l_relro_addr;
347 size_t l_relro_size;
348
349 unsigned long long int l_serial;
350 };
351
352 #include <dl-relocate-ld.h>
353
354 /* Information used by audit modules. For most link maps, this data
355 immediate follows the link map in memory. For the dynamic linker,
356 it is allocated separately. See link_map_audit_state in
357 <ldsodefs.h>. */
358 struct auditstate
359 {
360 uintptr_t cookie;
361 unsigned int bindflags;
362 };
363
364
365 /* This is the hidden instance of struct r_debug_extended used by the
366 dynamic linker. */
367 extern struct r_debug_extended _r_debug_extended attribute_hidden;
368
369 #if __ELF_NATIVE_CLASS == 32
370 # define symbind symbind32
371 # define LA_SYMBIND "la_symbind32"
372 #elif __ELF_NATIVE_CLASS == 64
373 # define symbind symbind64
374 # define LA_SYMBIND "la_symbind64"
375 #else
376 # error "__ELF_NATIVE_CLASS must be defined"
377 #endif
378
379 extern int __dl_iterate_phdr (int (*callback) (struct dl_phdr_info *info,
380 size_t size, void *data),
381 void *data);
382 hidden_proto (__dl_iterate_phdr)
383
384 /* We use this macro to refer to ELF macros independent of the native
385 wordsize. `ELFW(R_TYPE)' is used in place of `ELF32_R_TYPE' or
386 `ELF64_R_TYPE'. */
387 #define ELFW(type) _ElfW (ELF, __ELF_NATIVE_CLASS, type)
388
389 # endif /* !_ISOMAC */
390 #endif /* include/link.h */