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d66e34cd | 1 | /* Run-time dynamic linker data structures for loaded ELF shared objects. |
a2e1b046 | 2 | Copyright (C) 1995, 1996 Free Software Foundation, Inc. |
d66e34cd RM |
3 | This file is part of the GNU C Library. |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Library General Public License as | |
7 | published by the Free Software Foundation; either version 2 of the | |
8 | License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Library General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Library General Public | |
16 | License along with the GNU C Library; see the file COPYING.LIB. If | |
17 | not, write to the Free Software Foundation, Inc., 675 Mass Ave, | |
18 | Cambridge, MA 02139, USA. */ | |
19 | ||
20 | #ifndef _LINK_H | |
21 | #define _LINK_H 1 | |
22 | ||
266180eb RM |
23 | #define __need_size_t |
24 | #include <stddef.h> | |
25 | ||
d66e34cd RM |
26 | #include <elf.h> |
27 | ||
266180eb RM |
28 | /* We use this macro to refer to ELF types independent of the native wordsize. |
29 | `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'. */ | |
567c63af RM |
30 | #define ElfW(type) _ElfW (Elf, __ELF_NATIVE_CLASS, type) |
31 | #define ELFW(type) _ElfW (ELF, __ELF_NATIVE_CLASS, type) | |
266180eb RM |
32 | #define _ElfW(e,w,t) _ElfW_1 (e, w, _##t) |
33 | #define _ElfW_1(e,w,t) e##w##t | |
567c63af | 34 | #include <elfclass.h> /* Defines __ELF_NATIVE_CLASS. */ |
d66e34cd RM |
35 | |
36 | /* Rendezvous structure used by the run-time dynamic linker to communicate | |
37 | details of shared object loading to the debugger. If the executable's | |
38 | dynamic section has a DT_DEBUG element, the run-time linker sets that | |
39 | element's value to the address where this structure can be found. */ | |
40 | ||
41 | struct r_debug | |
42 | { | |
43 | int r_version; /* Version number for this protocol. */ | |
44 | ||
45 | struct link_map *r_map; /* Head of the chain of loaded objects. */ | |
46 | ||
47 | /* This is the address of a function internal to the run-time linker, | |
48 | that will always be called when the linker begins to map in a | |
49 | library or unmap it, and again when the mapping change is complete. | |
50 | The debugger can set a breakpoint at this address if it wants to | |
51 | notice shared object mapping changes. */ | |
266180eb | 52 | ElfW(Addr) r_brk; |
d66e34cd RM |
53 | enum |
54 | { | |
55 | /* This state value describes the mapping change taking place when | |
56 | the `r_brk' address is called. */ | |
57 | RT_CONSISTENT, /* Mapping change is complete. */ | |
58 | RT_ADD, /* Beginning to add a new object. */ | |
59 | RT_DELETE, /* Beginning to remove an object mapping. */ | |
60 | } r_state; | |
61 | ||
266180eb | 62 | ElfW(Addr) r_ldbase; /* Base address the linker is loaded at. */ |
d66e34cd RM |
63 | }; |
64 | ||
4d6acc61 RM |
65 | /* This is the instance of that structure used by the dynamic linker. */ |
66 | extern struct r_debug _r_debug; | |
67 | ||
d66e34cd RM |
68 | /* This symbol refers to the "dynamic structure" in the `.dynamic' section |
69 | of whatever module refers to `_DYNAMIC'. So, to find its own | |
70 | `struct r_debug', a program could do: | |
71 | for (dyn = _DYNAMIC; dyn->d_tag != DT_NULL) | |
72 | if (dyn->d_tag == DT_DEBUG) r_debug = (struct r_debug) dyn->d_un.d_ptr; | |
73 | */ | |
74 | ||
266180eb | 75 | extern ElfW(Dyn) _DYNAMIC[]; |
d66e34cd RM |
76 | |
77 | ||
78 | /* Structure describing a loaded shared object. The `l_next' and `l_prev' | |
79 | members form a chain of all the shared objects loaded at startup. | |
80 | ||
81 | These data structures exist in space used by the run-time dynamic linker; | |
82 | modifying them may have disastrous results. */ | |
83 | ||
84 | struct link_map | |
85 | { | |
86 | /* These first few members are part of the protocol with the debugger. | |
87 | This is the same format used in SVR4. */ | |
88 | ||
266180eb | 89 | ElfW(Addr) l_addr; /* Base address shared object is loaded at. */ |
d66e34cd | 90 | char *l_name; /* Absolute file name object was found in. */ |
266180eb | 91 | ElfW(Dyn) *l_ld; /* Dynamic section of the shared object. */ |
d66e34cd RM |
92 | struct link_map *l_next, *l_prev; /* Chain of loaded objects. */ |
93 | ||
94 | /* All following members are internal to the dynamic linker. | |
95 | They may change without notice. */ | |
96 | ||
97 | const char *l_libname; /* Name requested (before search). */ | |
a2e1b046 RM |
98 | /* Indexed pointers to dynamic section. |
99 | [0,DT_NUM) are indexed by the processor-independent tags. | |
100 | [DT_NUM,DT_NUM+DT_PROCNUM] are indexed by the tag minus DT_LOPROC. */ | |
266180eb RM |
101 | ElfW(Dyn) *l_info[DT_NUM + DT_PROCNUM]; |
102 | const ElfW(Phdr) *l_phdr; /* Pointer to program header table in core. */ | |
103 | ElfW(Addr) l_entry; /* Entry point location. */ | |
104 | ElfW(Half) l_phnum; /* Number of program header entries. */ | |
d66e34cd | 105 | |
efec1d0c RM |
106 | /* Array of DT_NEEDED dependencies and their dependencies, in |
107 | dependency order for symbol lookup. This is null before the | |
108 | dependencies have been loaded. */ | |
109 | struct link_map **l_searchlist; | |
110 | unsigned int l_nsearchlist; | |
111 | ||
ba79d61b RM |
112 | /* Dependent object that first caused this object to be loaded. */ |
113 | struct link_map *l_loader; | |
114 | ||
d66e34cd | 115 | /* Symbol hash table. */ |
8d6468d0 RM |
116 | ElfW(Symndx) l_nbuckets; |
117 | const ElfW(Symndx) *l_buckets, *l_chain; | |
d66e34cd RM |
118 | |
119 | unsigned int l_opencount; /* Reference count for dlopen/dlclose. */ | |
120 | enum /* Where this object came from. */ | |
121 | { | |
122 | lt_executable, /* The main executable program. */ | |
d66e34cd RM |
123 | lt_library, /* Library needed by main executable. */ |
124 | lt_loaded, /* Extra run-time loaded shared object. */ | |
125 | } l_type:2; | |
d66e34cd RM |
126 | unsigned int l_relocated:1; /* Nonzero if object's relocations done. */ |
127 | unsigned int l_init_called:1; /* Nonzero if DT_INIT function called. */ | |
128 | unsigned int l_init_running:1; /* Nonzero while DT_INIT function runs. */ | |
ba79d61b RM |
129 | unsigned int l_global:1; /* Nonzero if object in _dl_global_scope. */ |
130 | unsigned int l_reserved:2; /* Reserved for internal use. */ | |
d66e34cd RM |
131 | }; |
132 | \f | |
133 | /* Internal functions of the run-time dynamic linker. | |
134 | These can be accessed if you link again the dynamic linker | |
135 | as a shared library, as in `-lld' or `/lib/ld.so' explicitly; | |
136 | but are not normally of interest to user programs. | |
137 | ||
138 | The `-ldl' library functions in <dlfcn.h> provide a simple | |
139 | user interface to run-time dynamic linking. */ | |
140 | ||
141 | ||
266180eb RM |
142 | /* Cached value of `getpagesize ()'. */ |
143 | extern size_t _dl_pagesize; | |
144 | ||
d66e34cd RM |
145 | /* File descriptor referring to the zero-fill device. */ |
146 | extern int _dl_zerofd; | |
147 | ||
148 | /* OS-dependent function to open the zero-fill device. */ | |
149 | extern int _dl_sysdep_open_zero_fill (void); /* dl-sysdep.c */ | |
150 | ||
6a76c115 RM |
151 | /* OS-dependent function to write a message on the standard output. |
152 | All arguments are `const char *'; args until a null pointer | |
153 | are concatenated to form the message to print. */ | |
154 | extern void _dl_sysdep_message (const char *string, ...); | |
155 | ||
d66e34cd RM |
156 | /* OS-dependent function to give a fatal error message and exit |
157 | when the dynamic linker fails before the program is fully linked. | |
158 | All arguments are `const char *'; args until a null pointer | |
159 | are concatenated to form the message to print. */ | |
160 | extern void _dl_sysdep_fatal (const char *string, ...) | |
161 | __attribute__ ((__noreturn__)); | |
162 | ||
163 | /* Nonzero if the program should be "secure" (i.e. it's setuid or somesuch). | |
164 | This tells the dynamic linker to ignore environment variables. */ | |
165 | extern int _dl_secure; | |
166 | ||
167 | /* This function is called by all the internal dynamic linker functions | |
421f82e5 RM |
168 | when they encounter an error. ERRCODE is either an `errno' code or |
169 | zero; OBJECT is the name of the problematical shared object, or null if | |
170 | it is a general problem; ERRSTRING is a string describing the specific | |
171 | problem. */ | |
a2e1b046 | 172 | |
421f82e5 RM |
173 | extern void _dl_signal_error (int errcode, |
174 | const char *object, | |
175 | const char *errstring) | |
d66e34cd RM |
176 | __attribute__ ((__noreturn__)); |
177 | ||
178 | /* Call OPERATE, catching errors from `dl_signal_error'. If there is no | |
421f82e5 RM |
179 | error, *ERRSTRING is set to null. If there is an error, *ERRSTRING and |
180 | *OBJECT are set to the strings passed to _dl_signal_error, and the error | |
14bab8de UD |
181 | code passed is the return value. ERRSTRING if nonzero points to a |
182 | malloc'ed string which the caller has to free after use. */ | |
183 | extern int _dl_catch_error (char **errstring, | |
421f82e5 RM |
184 | const char **object, |
185 | void (*operate) (void)); | |
d66e34cd RM |
186 | |
187 | ||
188 | /* Helper function for <dlfcn.h> functions. Runs the OPERATE function via | |
189 | _dl_catch_error. Returns zero for success, nonzero for failure; and | |
190 | arranges for `dlerror' to return the error details. */ | |
191 | extern int _dlerror_run (void (*operate) (void)); | |
192 | ||
193 | ||
194 | /* Open the shared object NAME and map in its segments. | |
195 | LOADER's DT_RPATH is used in searching for NAME. | |
d66e34cd RM |
196 | If the object is already opened, returns its existing map. */ |
197 | extern struct link_map *_dl_map_object (struct link_map *loader, | |
ba79d61b | 198 | const char *name, int type); |
ea03559a | 199 | |
2064087b RM |
200 | /* Call _dl_map_object on the dependencies of MAP, and set up |
201 | MAP->l_searchlist. PRELOADS points to a vector of NPRELOADS previously | |
202 | loaded objects that will be inserted into MAP->l_searchlist after MAP | |
203 | but before its dependencies. */ | |
204 | extern void _dl_map_object_deps (struct link_map *map, | |
205 | struct link_map **preloads, | |
206 | unsigned int npreloads); | |
efec1d0c | 207 | |
d66e34cd RM |
208 | /* Cache the locations of MAP's hash table. */ |
209 | extern void _dl_setup_hash (struct link_map *map); | |
210 | ||
211 | ||
efec1d0c | 212 | /* Open the shared object NAME, relocate it, and run its initializer if it |
a23db8e4 RM |
213 | hasn't already been run. MODE is as for `dlopen' (see <dlfcn.h>). If |
214 | the object is already opened, returns its existing map. */ | |
215 | extern struct link_map *_dl_open (const char *name, int mode); | |
efec1d0c | 216 | |
ba79d61b RM |
217 | /* Close an object previously opened by _dl_open. */ |
218 | extern void _dl_close (struct link_map *map); | |
efec1d0c RM |
219 | |
220 | ||
d66e34cd RM |
221 | /* Search loaded objects' symbol tables for a definition of the symbol |
222 | referred to by UNDEF. *SYM is the symbol table entry containing the | |
223 | reference; it is replaced with the defining symbol, and the base load | |
ba79d61b RM |
224 | address of the defining object is returned. SYMBOL_SCOPE is a |
225 | null-terminated list of object scopes to search; each object's | |
226 | l_searchlist (i.e. the segment of the dependency tree starting at that | |
227 | object) is searched in turn. REFERENCE_NAME should name the object | |
706074a5 UD |
228 | containing the reference; it is used in error messages. FLAGS is a |
229 | set of flags: */ | |
230 | #define DL_LOOKUP_NOEXEC 1 /* Don't search the executable for a | |
231 | definition; this is used for copy | |
232 | relocs. */ | |
233 | #define DL_LOOKUP_NOPLT 2 /* The reference must not be resolved | |
234 | to a PLT entry. */ | |
266180eb RM |
235 | extern ElfW(Addr) _dl_lookup_symbol (const char *undef, |
236 | const ElfW(Sym) **sym, | |
ba79d61b | 237 | struct link_map *symbol_scope[], |
f2b0f935 | 238 | const char *reference_name, |
706074a5 | 239 | int flags); |
d66e34cd | 240 | |
ee188d55 | 241 | /* Look up symbol NAME in MAP's scope and return its run-time address. */ |
266180eb | 242 | extern ElfW(Addr) _dl_symbol_value (struct link_map *map, const char *name); |
ee188d55 RM |
243 | |
244 | ||
245 | /* Structure describing the dynamic linker itself. */ | |
246 | extern struct link_map _dl_rtld_map; | |
d66e34cd | 247 | |
ba79d61b RM |
248 | /* The list of objects currently loaded is the third element of the |
249 | `_dl_default_scope' array, and the fourth element is always null. | |
250 | This leaves two slots before it that are used when resolving | |
251 | DT_SYMBOLIC objects' references one after it for normal references | |
252 | (see below). */ | |
253 | #define _dl_loaded (_dl_default_scope[2]) | |
254 | extern struct link_map *_dl_default_scope[5]; | |
255 | ||
256 | /* Null-terminated list of objects in the dynamic `global scope'. The | |
257 | list starts at [2]; i.e. &_dl_global_scope[2] is the argument | |
258 | passed to _dl_lookup_symbol to search the global scope. To search | |
259 | a specific object and its dependencies in preference to the global | |
260 | scope, fill in the [1] slot and pass its address; for two specific | |
261 | object scopes, fill [0] and [1]. The list is double-terminated; to | |
262 | search the global scope and then a specific object and its | |
263 | dependencies, set *_dl_global_scope_end. This variable initially | |
264 | points to _dl_default_scope, and _dl_loaded is always kept in [2] | |
265 | of this list. A new list is malloc'd when new objects are loaded | |
266 | with RTLD_GLOBAL. */ | |
267 | extern struct link_map **_dl_global_scope, **_dl_global_scope_end; | |
268 | extern size_t _dl_global_scope_alloc; /* Number of slots malloc'd. */ | |
269 | ||
270 | /* Hack _dl_global_scope[0] and [1] as necessary, and return a pointer into | |
271 | _dl_global_scope that should be passed to _dl_lookup_symbol for symbol | |
272 | references made in the object MAP's relocations. */ | |
273 | extern struct link_map **_dl_object_relocation_scope (struct link_map *map); | |
d66e34cd | 274 | |
d66e34cd RM |
275 | |
276 | /* Allocate a `struct link_map' for a new object being loaded, | |
277 | and enter it into the _dl_loaded list. */ | |
278 | extern struct link_map *_dl_new_object (char *realname, const char *libname, | |
279 | int type); | |
280 | ||
281 | /* Relocate the given object (if it hasn't already been). | |
ba79d61b | 282 | SCOPE is passed to _dl_lookup_symbol in symbol lookups. |
d66e34cd | 283 | If LAZY is nonzero, don't relocate its PLT. */ |
ba79d61b RM |
284 | extern void _dl_relocate_object (struct link_map *map, |
285 | struct link_map *scope[], | |
286 | int lazy); | |
d66e34cd | 287 | |
f68b86cc RM |
288 | /* Return the address of the next initializer function for MAP or one of |
289 | its dependencies that has not yet been run. When there are no more | |
290 | initializers to be run, this returns zero. The functions are returned | |
291 | in the order they should be called. */ | |
266180eb | 292 | extern ElfW(Addr) _dl_init_next (struct link_map *map); |
d66e34cd RM |
293 | |
294 | /* Call the finalizer functions of all shared objects whose | |
295 | initializer functions have completed. */ | |
296 | extern void _dl_fini (void); | |
297 | ||
298 | /* The dynamic linker calls this function before and having changing | |
299 | any shared object mappings. The `r_state' member of `struct r_debug' | |
300 | says what change is taking place. This function's address is | |
301 | the value of the `r_brk' member. */ | |
4d6acc61 RM |
302 | extern void _dl_debug_state (void); |
303 | ||
304 | /* Initialize `struct r_debug' if it has not already been done. The | |
305 | argument is the run-time load address of the dynamic linker, to be put | |
306 | in the `r_ldbase' member. Returns the address of the structure. */ | |
307 | extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase); | |
d66e34cd RM |
308 | |
309 | ||
310 | #endif /* link.h */ |