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d66e34cd | 1 | /* Run time dynamic linker. |
948c3e72 | 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 | #include <link.h> | |
d66e34cd RM |
21 | #include <stddef.h> |
22 | #include <stdlib.h> | |
f51d1dfd | 23 | #include <string.h> |
d66e34cd | 24 | #include <unistd.h> |
2064087b | 25 | #include <sys/mman.h> /* Check if MAP_ANON is defined. */ |
21ee7166 | 26 | #include "../stdio-common/_itoa.h" |
b1dbbaa4 | 27 | #include <assert.h> |
f5348425 RM |
28 | #include "dynamic-link.h" |
29 | ||
30 | ||
d66e34cd RM |
31 | /* System-specific function to do initial startup for the dynamic linker. |
32 | After this, file access calls and getenv must work. This is responsible | |
33 | for setting _dl_secure if we need to be secure (e.g. setuid), | |
34 | and for setting _dl_argc and _dl_argv, and then calling _dl_main. */ | |
266180eb RM |
35 | extern ElfW(Addr) _dl_sysdep_start (void **start_argptr, |
36 | void (*dl_main) (const ElfW(Phdr) *phdr, | |
37 | ElfW(Half) phent, | |
38 | ElfW(Addr) *user_entry)); | |
4cb20290 | 39 | extern void _dl_sysdep_start_cleanup (void); |
d66e34cd RM |
40 | |
41 | int _dl_secure; | |
42 | int _dl_argc; | |
43 | char **_dl_argv; | |
4cb20290 | 44 | const char *_dl_rpath; |
d66e34cd | 45 | |
266180eb RM |
46 | static void dl_main (const ElfW(Phdr) *phdr, |
47 | ElfW(Half) phent, | |
48 | ElfW(Addr) *user_entry); | |
d66e34cd | 49 | |
ee188d55 | 50 | struct link_map _dl_rtld_map; |
86d2c878 | 51 | |
b1dbbaa4 RM |
52 | #ifdef RTLD_START |
53 | RTLD_START | |
54 | #else | |
55 | #error "sysdeps/MACHINE/dl-machine.h fails to define RTLD_START" | |
56 | #endif | |
57 | ||
266180eb | 58 | ElfW(Addr) |
d66e34cd RM |
59 | _dl_start (void *arg) |
60 | { | |
86d2c878 | 61 | struct link_map bootstrap_map; |
d66e34cd | 62 | |
b1dbbaa4 RM |
63 | /* This #define produces dynamic linking inline functions for |
64 | bootstrap relocation instead of general-purpose relocation. */ | |
65 | #define RTLD_BOOTSTRAP | |
66 | #define RESOLVE(sym, reloc_addr, noplt) bootstrap_map.l_addr | |
67 | #include "dynamic-link.h" | |
68 | ||
d66e34cd | 69 | /* Figure out the run-time load address of the dynamic linker itself. */ |
86d2c878 | 70 | bootstrap_map.l_addr = elf_machine_load_address (); |
d66e34cd RM |
71 | |
72 | /* Read our own dynamic section and fill in the info array. | |
73 | Conveniently, the first element of the GOT contains the | |
74 | offset of _DYNAMIC relative to the run-time load address. */ | |
86d2c878 RM |
75 | bootstrap_map.l_ld = (void *) bootstrap_map.l_addr + *elf_machine_got (); |
76 | elf_get_dynamic_info (bootstrap_map.l_ld, bootstrap_map.l_info); | |
d66e34cd RM |
77 | |
78 | #ifdef ELF_MACHINE_BEFORE_RTLD_RELOC | |
86d2c878 | 79 | ELF_MACHINE_BEFORE_RTLD_RELOC (bootstrap_map.l_info); |
d66e34cd RM |
80 | #endif |
81 | ||
82 | /* Relocate ourselves so we can do normal function calls and | |
83 | data access using the global offset table. */ | |
421f82e5 | 84 | |
f51d1dfd | 85 | ELF_DYNAMIC_RELOCATE (&bootstrap_map, 0); |
421f82e5 | 86 | |
d66e34cd RM |
87 | |
88 | /* Now life is sane; we can call functions and access global data. | |
89 | Set up to use the operating system facilities, and find out from | |
90 | the operating system's program loader where to find the program | |
91 | header table in core. */ | |
92 | ||
86d2c878 RM |
93 | |
94 | /* Transfer data about ourselves to the permanent link_map structure. */ | |
ee188d55 RM |
95 | _dl_rtld_map.l_addr = bootstrap_map.l_addr; |
96 | _dl_rtld_map.l_ld = bootstrap_map.l_ld; | |
97 | memcpy (_dl_rtld_map.l_info, bootstrap_map.l_info, | |
98 | sizeof _dl_rtld_map.l_info); | |
99 | _dl_setup_hash (&_dl_rtld_map); | |
86d2c878 | 100 | |
4cb20290 RM |
101 | /* Cache the DT_RPATH stored in ld.so itself; this will be |
102 | the default search path. */ | |
ee188d55 RM |
103 | _dl_rpath = (void *) (_dl_rtld_map.l_addr + |
104 | _dl_rtld_map.l_info[DT_STRTAB]->d_un.d_ptr + | |
105 | _dl_rtld_map.l_info[DT_RPATH]->d_un.d_val); | |
d66e34cd RM |
106 | |
107 | /* Call the OS-dependent function to set up life so we can do things like | |
108 | file access. It will call `dl_main' (below) to do all the real work | |
109 | of the dynamic linker, and then unwind our frame and run the user | |
110 | entry point on the same stack we entered on. */ | |
8d6468d0 | 111 | return _dl_sysdep_start (arg, &dl_main); |
d66e34cd RM |
112 | } |
113 | ||
114 | ||
115 | /* Now life is peachy; we can do all normal operations. | |
116 | On to the real work. */ | |
117 | ||
118 | void _start (void); | |
119 | ||
91f62ce6 | 120 | unsigned int _dl_skip_args; /* Nonzero if we were run directly. */ |
a1a9d215 | 121 | |
d66e34cd | 122 | static void |
266180eb RM |
123 | dl_main (const ElfW(Phdr) *phdr, |
124 | ElfW(Half) phent, | |
125 | ElfW(Addr) *user_entry) | |
d66e34cd | 126 | { |
266180eb | 127 | const ElfW(Phdr) *ph; |
efec1d0c | 128 | struct link_map *l; |
0200214b RM |
129 | int lazy; |
130 | int list_only = 0; | |
2064087b RM |
131 | struct link_map **preloads; |
132 | unsigned int npreloads; | |
d66e34cd | 133 | |
266180eb | 134 | if (*user_entry == (ElfW(Addr)) &_start) |
0200214b RM |
135 | { |
136 | /* Ho ho. We are not the program interpreter! We are the program | |
137 | itself! This means someone ran ld.so as a command. Well, that | |
138 | might be convenient to do sometimes. We support it by | |
139 | interpreting the args like this: | |
140 | ||
141 | ld.so PROGRAM ARGS... | |
142 | ||
143 | The first argument is the name of a file containing an ELF | |
144 | executable we will load and run with the following arguments. | |
145 | To simplify life here, PROGRAM is searched for using the | |
146 | normal rules for shared objects, rather than $PATH or anything | |
147 | like that. We just load it and use its entry point; we don't | |
148 | pay attention to its PT_INTERP command (we are the interpreter | |
149 | ourselves). This is an easy way to test a new ld.so before | |
150 | installing it. */ | |
151 | if (_dl_argc < 2) | |
152 | _dl_sysdep_fatal ("\ | |
6a76c115 | 153 | Usage: ld.so [--list] EXECUTABLE-FILE [ARGS-FOR-PROGRAM...]\n\ |
d66e34cd RM |
154 | You have invoked `ld.so', the helper program for shared library executables.\n\ |
155 | This program usually lives in the file `/lib/ld.so', and special directives\n\ | |
156 | in executable files using ELF shared libraries tell the system's program\n\ | |
157 | loader to load the helper program from this file. This helper program loads\n\ | |
158 | the shared libraries needed by the program executable, prepares the program\n\ | |
159 | to run, and runs it. You may invoke this helper program directly from the\n\ | |
160 | command line to load and run an ELF executable file; this is like executing\n\ | |
161 | that file itself, but always uses this helper program from the file you\n\ | |
162 | specified, instead of the helper program file specified in the executable\n\ | |
163 | file you run. This is mostly of use for maintainers to test new versions\n\ | |
5bf62f2d | 164 | of this helper program; chances are you did not intend to run this program.\n", |
0200214b | 165 | NULL); |
421f82e5 | 166 | |
ffee1316 RM |
167 | /* Note the place where the dynamic linker actually came from. */ |
168 | _dl_rtld_map.l_name = _dl_argv[0]; | |
6a76c115 | 169 | |
0200214b RM |
170 | if (! strcmp (_dl_argv[1], "--list")) |
171 | { | |
172 | list_only = 1; | |
6a76c115 RM |
173 | |
174 | ++_dl_skip_args; | |
421f82e5 RM |
175 | --_dl_argc; |
176 | ++_dl_argv; | |
421f82e5 | 177 | } |
d66e34cd | 178 | |
0200214b RM |
179 | ++_dl_skip_args; |
180 | --_dl_argc; | |
181 | ++_dl_argv; | |
91f62ce6 | 182 | |
ba79d61b | 183 | l = _dl_map_object (NULL, _dl_argv[0], lt_library); |
0200214b RM |
184 | phdr = l->l_phdr; |
185 | phent = l->l_phnum; | |
186 | l->l_name = (char *) ""; | |
187 | *user_entry = l->l_entry; | |
188 | } | |
189 | else | |
190 | { | |
191 | /* Create a link_map for the executable itself. | |
192 | This will be what dlopen on "" returns. */ | |
ba79d61b | 193 | l = _dl_new_object ((char *) "", "", lt_library); |
0200214b RM |
194 | l->l_phdr = phdr; |
195 | l->l_phnum = phent; | |
0200214b RM |
196 | l->l_entry = *user_entry; |
197 | } | |
198 | ||
199 | if (l != _dl_loaded) | |
200 | { | |
201 | /* GDB assumes that the first element on the chain is the | |
202 | link_map for the executable itself, and always skips it. | |
203 | Make sure the first one is indeed that one. */ | |
204 | l->l_prev->l_next = l->l_next; | |
205 | if (l->l_next) | |
206 | l->l_next->l_prev = l->l_prev; | |
207 | l->l_prev = NULL; | |
208 | l->l_next = _dl_loaded; | |
209 | _dl_loaded->l_prev = l; | |
210 | _dl_loaded = l; | |
211 | } | |
212 | ||
213 | /* Scan the program header table for the dynamic section. */ | |
214 | for (ph = phdr; ph < &phdr[phent]; ++ph) | |
215 | switch (ph->p_type) | |
216 | { | |
217 | case PT_DYNAMIC: | |
218 | /* This tells us where to find the dynamic section, | |
219 | which tells us everything we need to do. */ | |
220 | l->l_ld = (void *) l->l_addr + ph->p_vaddr; | |
221 | break; | |
222 | case PT_INTERP: | |
223 | /* This "interpreter segment" was used by the program loader to | |
224 | find the program interpreter, which is this program itself, the | |
225 | dynamic linker. We note what name finds us, so that a future | |
226 | dlopen call or DT_NEEDED entry, for something that wants to link | |
227 | against the dynamic linker as a shared library, will know that | |
228 | the shared object is already loaded. */ | |
ffee1316 | 229 | _dl_rtld_map.l_libname = (const char *) l->l_addr + ph->p_vaddr; |
0200214b RM |
230 | break; |
231 | } | |
ffee1316 RM |
232 | if (! _dl_rtld_map.l_libname && _dl_rtld_map.l_name) |
233 | /* We were invoked directly, so the program might not have a PT_INTERP. */ | |
234 | _dl_rtld_map.l_libname = _dl_rtld_map.l_name; | |
235 | else | |
236 | assert (_dl_rtld_map.l_libname); /* How else did we get here? */ | |
0200214b RM |
237 | |
238 | /* Extract the contents of the dynamic section for easy access. */ | |
239 | elf_get_dynamic_info (l->l_ld, l->l_info); | |
240 | if (l->l_info[DT_HASH]) | |
241 | /* Set up our cache of pointers into the hash table. */ | |
242 | _dl_setup_hash (l); | |
243 | ||
0200214b RM |
244 | /* Put the link_map for ourselves on the chain so it can be found by |
245 | name. */ | |
ffee1316 RM |
246 | if (! _dl_rtld_map.l_name) |
247 | /* If not invoked directly, the dynamic linker shared object file was | |
248 | found by the PT_INTERP name. */ | |
249 | _dl_rtld_map.l_name = (char *) _dl_rtld_map.l_libname; | |
ba79d61b | 250 | _dl_rtld_map.l_type = lt_library; |
0200214b RM |
251 | while (l->l_next) |
252 | l = l->l_next; | |
ee188d55 RM |
253 | l->l_next = &_dl_rtld_map; |
254 | _dl_rtld_map.l_prev = l; | |
0200214b | 255 | |
2064087b RM |
256 | preloads = NULL; |
257 | npreloads = 0; | |
258 | if (! _dl_secure) | |
259 | { | |
260 | const char *preloadlist = getenv ("LD_PRELOAD"); | |
261 | if (preloadlist) | |
262 | { | |
263 | /* The LD_PRELOAD environment variable gives a colon-separated | |
264 | list of libraries that are loaded before the executable's | |
265 | dependencies and prepended to the global scope list. */ | |
266 | char *list = strdupa (preloadlist); | |
267 | char *p; | |
268 | while ((p = strsep (&list, ":")) != NULL) | |
269 | { | |
270 | (void) _dl_map_object (NULL, p, lt_library); | |
271 | ++npreloads; | |
272 | } | |
273 | ||
274 | if (npreloads != 0) | |
275 | { | |
276 | /* Set up PRELOADS with a vector of the preloaded libraries. */ | |
277 | struct link_map *l; | |
278 | unsigned int i; | |
279 | preloads = __alloca (npreloads * sizeof preloads[0]); | |
280 | l = _dl_rtld_map.l_next; /* End of the chain before preloads. */ | |
281 | i = 0; | |
282 | do | |
283 | { | |
284 | preloads[i++] = l; | |
285 | l = l->l_next; | |
286 | } while (l); | |
287 | assert (i == npreloads); | |
288 | } | |
289 | } | |
290 | } | |
291 | ||
292 | /* Load all the libraries specified by DT_NEEDED entries. If LD_PRELOAD | |
293 | specified some libraries to load, these are inserted before the actual | |
294 | dependencies in the executable's searchlist for symbol resolution. */ | |
295 | _dl_map_object_deps (l, preloads, npreloads); | |
d66e34cd | 296 | |
2064087b | 297 | #ifndef MAP_ANON |
f332db02 RM |
298 | /* We are done mapping things, so close the zero-fill descriptor. */ |
299 | __close (_dl_zerofd); | |
300 | _dl_zerofd = -1; | |
2064087b | 301 | #endif |
f332db02 | 302 | |
f9496a7b RM |
303 | /* Remove _dl_rtld_map from the chain. */ |
304 | _dl_rtld_map.l_prev->l_next = _dl_rtld_map.l_next; | |
305 | if (_dl_rtld_map.l_next) | |
306 | _dl_rtld_map.l_next->l_prev = _dl_rtld_map.l_prev; | |
307 | ||
308 | if (_dl_rtld_map.l_opencount) | |
0200214b | 309 | { |
f9496a7b RM |
310 | /* Some DT_NEEDED entry referred to the interpreter object itself, so |
311 | put it back in the list of visible objects. We insert it into the | |
312 | chain in symbol search order because gdb uses the chain's order as | |
313 | its symbol search order. */ | |
314 | unsigned int i = 1; | |
315 | while (l->l_searchlist[i] != &_dl_rtld_map) | |
316 | ++i; | |
317 | _dl_rtld_map.l_prev = l->l_searchlist[i - 1]; | |
318 | _dl_rtld_map.l_next = (i + 1 < l->l_nsearchlist ? | |
319 | l->l_searchlist[i + 1] : NULL); | |
320 | assert (_dl_rtld_map.l_prev->l_next == _dl_rtld_map.l_next); | |
321 | _dl_rtld_map.l_prev->l_next = &_dl_rtld_map; | |
4d02a5b1 | 322 | if (_dl_rtld_map.l_next) |
f9496a7b RM |
323 | { |
324 | assert (_dl_rtld_map.l_next->l_prev == _dl_rtld_map.l_prev); | |
325 | _dl_rtld_map.l_next->l_prev = &_dl_rtld_map; | |
326 | } | |
0200214b | 327 | } |
d66e34cd | 328 | |
0200214b RM |
329 | if (list_only) |
330 | { | |
331 | /* We were run just to list the shared libraries. It is | |
332 | important that we do this before real relocation, because the | |
333 | functions we call below for output may no longer work properly | |
334 | after relocation. */ | |
1a3a58fd | 335 | |
0200214b | 336 | int i; |
fd861379 | 337 | |
0200214b RM |
338 | if (! _dl_loaded->l_info[DT_NEEDED]) |
339 | _dl_sysdep_message ("\t", "statically linked\n", NULL); | |
340 | else | |
341 | for (l = _dl_loaded->l_next; l; l = l->l_next) | |
342 | { | |
343 | char buf[20], *bp; | |
344 | buf[sizeof buf - 1] = '\0'; | |
345 | bp = _itoa (l->l_addr, &buf[sizeof buf - 1], 16, 0); | |
346 | while (&buf[sizeof buf - 1] - bp < sizeof l->l_addr * 2) | |
347 | *--bp = '0'; | |
348 | _dl_sysdep_message ("\t", l->l_libname, " => ", l->l_name, | |
349 | " (0x", bp, ")\n", NULL); | |
350 | } | |
1a3a58fd | 351 | |
0200214b RM |
352 | for (i = 1; i < _dl_argc; ++i) |
353 | { | |
266180eb | 354 | const ElfW(Sym) *ref = NULL; |
ba79d61b RM |
355 | ElfW(Addr) loadbase = _dl_lookup_symbol (_dl_argv[i], &ref, |
356 | &_dl_default_scope[2], | |
357 | "argument", 0, 0); | |
0200214b RM |
358 | char buf[20], *bp; |
359 | buf[sizeof buf - 1] = '\0'; | |
360 | bp = _itoa (ref->st_value, &buf[sizeof buf - 1], 16, 0); | |
361 | while (&buf[sizeof buf - 1] - bp < sizeof loadbase * 2) | |
362 | *--bp = '0'; | |
363 | _dl_sysdep_message (_dl_argv[i], " found at 0x", bp, NULL); | |
364 | buf[sizeof buf - 1] = '\0'; | |
365 | bp = _itoa (loadbase, &buf[sizeof buf - 1], 16, 0); | |
366 | while (&buf[sizeof buf - 1] - bp < sizeof loadbase * 2) | |
367 | *--bp = '0'; | |
368 | _dl_sysdep_message (" in object at 0x", bp, "\n", NULL); | |
1a3a58fd | 369 | } |
d66e34cd | 370 | |
0200214b RM |
371 | _exit (0); |
372 | } | |
86d2c878 | 373 | |
0200214b RM |
374 | lazy = !_dl_secure && *(getenv ("LD_BIND_NOW") ?: "") == '\0'; |
375 | ||
ba79d61b RM |
376 | { |
377 | /* Now we have all the objects loaded. Relocate them all except for | |
378 | the dynamic linker itself. We do this in reverse order so that copy | |
379 | relocs of earlier objects overwrite the data written by later | |
380 | objects. We do not re-relocate the dynamic linker itself in this | |
381 | loop because that could result in the GOT entries for functions we | |
382 | call being changed, and that would break us. It is safe to relocate | |
383 | the dynamic linker out of order because it has no copy relocs (we | |
384 | know that because it is self-contained). */ | |
385 | ||
386 | l = _dl_loaded; | |
387 | while (l->l_next) | |
388 | l = l->l_next; | |
389 | do | |
390 | { | |
391 | if (l != &_dl_rtld_map) | |
392 | { | |
393 | _dl_relocate_object (l, _dl_object_relocation_scope (l), lazy); | |
394 | *_dl_global_scope_end = NULL; | |
395 | } | |
396 | l = l->l_prev; | |
397 | } while (l); | |
398 | ||
399 | /* Do any necessary cleanups for the startup OS interface code. | |
400 | We do these now so that no calls are made after rtld re-relocation | |
401 | which might be resolved to different functions than we expect. | |
402 | We cannot do this before relocating the other objects because | |
403 | _dl_relocate_object might need to call `mprotect' for DT_TEXTREL. */ | |
404 | _dl_sysdep_start_cleanup (); | |
405 | ||
406 | if (_dl_rtld_map.l_opencount > 0) | |
407 | /* There was an explicit ref to the dynamic linker as a shared lib. | |
408 | Re-relocate ourselves with user-controlled symbol definitions. */ | |
409 | _dl_relocate_object (&_dl_rtld_map, &_dl_default_scope[2], 0); | |
410 | } | |
0200214b | 411 | |
4d6acc61 RM |
412 | { |
413 | /* Initialize _r_debug. */ | |
414 | struct r_debug *r = _dl_debug_initialize (_dl_rtld_map.l_addr); | |
415 | ||
416 | l = _dl_loaded; | |
ec42724d RM |
417 | |
418 | #ifdef ELF_MACHINE_DEBUG_SETUP | |
419 | ||
420 | /* Some machines (e.g. MIPS) don't use DT_DEBUG in this way. */ | |
421 | ||
422 | ELF_MACHINE_DEBUG_SETUP (l, r); | |
423 | ELF_MACHINE_DEBUG_SETUP (&_dl_rtld_map, r); | |
424 | ||
425 | #else | |
426 | ||
4d6acc61 RM |
427 | if (l->l_info[DT_DEBUG]) |
428 | /* There is a DT_DEBUG entry in the dynamic section. Fill it in | |
429 | with the run-time address of the r_debug structure */ | |
430 | l->l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) r; | |
431 | ||
d746b89c RM |
432 | /* Fill in the pointer in the dynamic linker's own dynamic section, in |
433 | case you run gdb on the dynamic linker directly. */ | |
434 | if (_dl_rtld_map.l_info[DT_DEBUG]) | |
435 | _dl_rtld_map.l_info[DT_DEBUG]->d_un.d_ptr = (ElfW(Addr)) r; | |
436 | ||
ec42724d RM |
437 | #endif |
438 | ||
4d6acc61 RM |
439 | /* Notify the debugger that all objects are now mapped in. */ |
440 | r->r_state = RT_ADD; | |
441 | _dl_debug_state (); | |
442 | } | |
0200214b | 443 | |
ee188d55 | 444 | if (_dl_rtld_map.l_info[DT_INIT]) |
0200214b RM |
445 | { |
446 | /* Call the initializer for the compatibility version of the | |
447 | dynamic linker. There is no additional initialization | |
448 | required for the ABI-compliant dynamic linker. */ | |
86d2c878 | 449 | |
ee188d55 RM |
450 | (*(void (*) (void)) (_dl_rtld_map.l_addr + |
451 | _dl_rtld_map.l_info[DT_INIT]->d_un.d_ptr)) (); | |
0200214b RM |
452 | |
453 | /* Clear the field so a future dlopen won't run it again. */ | |
ee188d55 | 454 | _dl_rtld_map.l_info[DT_INIT] = NULL; |
421f82e5 | 455 | } |
d66e34cd RM |
456 | |
457 | /* Once we return, _dl_sysdep_start will invoke | |
458 | the DT_INIT functions and then *USER_ENTRY. */ | |
459 | } |