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