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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. */ | |
38 | extern Elf32_Addr _dl_sysdep_start (void **start_argptr, | |
39 | void (*dl_main) (const Elf32_Phdr *phdr, | |
40 | Elf32_Word phent, | |
41 | Elf32_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 RM |
48 | |
49 | struct r_debug dl_r_debug; | |
50 | ||
51 | static void dl_main (const Elf32_Phdr *phdr, | |
52 | Elf32_Word phent, | |
53 | Elf32_Addr *user_entry); | |
54 | ||
ee188d55 | 55 | struct link_map _dl_rtld_map; |
86d2c878 | 56 | |
d66e34cd RM |
57 | Elf32_Addr |
58 | _dl_start (void *arg) | |
59 | { | |
86d2c878 | 60 | struct link_map bootstrap_map; |
d66e34cd RM |
61 | |
62 | /* Figure out the run-time load address of the dynamic linker itself. */ | |
86d2c878 | 63 | bootstrap_map.l_addr = elf_machine_load_address (); |
d66e34cd RM |
64 | |
65 | /* Read our own dynamic section and fill in the info array. | |
66 | Conveniently, the first element of the GOT contains the | |
67 | offset of _DYNAMIC relative to the run-time load address. */ | |
86d2c878 RM |
68 | bootstrap_map.l_ld = (void *) bootstrap_map.l_addr + *elf_machine_got (); |
69 | elf_get_dynamic_info (bootstrap_map.l_ld, bootstrap_map.l_info); | |
d66e34cd RM |
70 | |
71 | #ifdef ELF_MACHINE_BEFORE_RTLD_RELOC | |
86d2c878 | 72 | ELF_MACHINE_BEFORE_RTLD_RELOC (bootstrap_map.l_info); |
d66e34cd RM |
73 | #endif |
74 | ||
75 | /* Relocate ourselves so we can do normal function calls and | |
76 | data access using the global offset table. */ | |
421f82e5 | 77 | |
ded29119 RM |
78 | /* We must initialize `l_type' to make sure it is not `lt_interpreter'. |
79 | That is the type to describe us, but not during bootstrapping--it | |
80 | indicates to elf_machine_rel{,a} that we were already relocated during | |
81 | bootstrapping, so it must anti-perform each bootstrapping relocation | |
82 | before applying the final relocation when ld.so is linked in as | |
83 | normal a shared library. */ | |
86d2c878 RM |
84 | bootstrap_map.l_type = lt_library; |
85 | ELF_DYNAMIC_RELOCATE (&bootstrap_map, 0, NULL); | |
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. */ | |
111 | return _dl_sysdep_start (&arg, &dl_main); | |
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 RM |
122 | static void |
123 | dl_main (const Elf32_Phdr *phdr, | |
124 | Elf32_Word phent, | |
125 | Elf32_Addr *user_entry) | |
126 | { | |
0200214b | 127 | const Elf32_Phdr *ph; |
efec1d0c | 128 | struct link_map *l; |
0200214b RM |
129 | const char *interpreter_name; |
130 | int lazy; | |
131 | int list_only = 0; | |
d66e34cd | 132 | |
0200214b RM |
133 | if (*user_entry == (Elf32_Addr) &_start) |
134 | { | |
135 | /* Ho ho. We are not the program interpreter! We are the program | |
136 | itself! This means someone ran ld.so as a command. Well, that | |
137 | might be convenient to do sometimes. We support it by | |
138 | interpreting the args like this: | |
139 | ||
140 | ld.so PROGRAM ARGS... | |
141 | ||
142 | The first argument is the name of a file containing an ELF | |
143 | executable we will load and run with the following arguments. | |
144 | To simplify life here, PROGRAM is searched for using the | |
145 | normal rules for shared objects, rather than $PATH or anything | |
146 | like that. We just load it and use its entry point; we don't | |
147 | pay attention to its PT_INTERP command (we are the interpreter | |
148 | ourselves). This is an easy way to test a new ld.so before | |
149 | installing it. */ | |
150 | if (_dl_argc < 2) | |
151 | _dl_sysdep_fatal ("\ | |
6a76c115 | 152 | Usage: ld.so [--list] EXECUTABLE-FILE [ARGS-FOR-PROGRAM...]\n\ |
d66e34cd RM |
153 | You have invoked `ld.so', the helper program for shared library executables.\n\ |
154 | This program usually lives in the file `/lib/ld.so', and special directives\n\ | |
155 | in executable files using ELF shared libraries tell the system's program\n\ | |
156 | loader to load the helper program from this file. This helper program loads\n\ | |
157 | the shared libraries needed by the program executable, prepares the program\n\ | |
158 | to run, and runs it. You may invoke this helper program directly from the\n\ | |
159 | command line to load and run an ELF executable file; this is like executing\n\ | |
160 | that file itself, but always uses this helper program from the file you\n\ | |
161 | specified, instead of the helper program file specified in the executable\n\ | |
162 | file you run. This is mostly of use for maintainers to test new versions\n\ | |
5bf62f2d | 163 | of this helper program; chances are you did not intend to run this program.\n", |
0200214b | 164 | NULL); |
421f82e5 | 165 | |
0200214b | 166 | interpreter_name = _dl_argv[0]; |
6a76c115 | 167 | |
0200214b RM |
168 | if (! strcmp (_dl_argv[1], "--list")) |
169 | { | |
170 | list_only = 1; | |
6a76c115 RM |
171 | |
172 | ++_dl_skip_args; | |
421f82e5 RM |
173 | --_dl_argc; |
174 | ++_dl_argv; | |
421f82e5 | 175 | } |
d66e34cd | 176 | |
0200214b RM |
177 | ++_dl_skip_args; |
178 | --_dl_argc; | |
179 | ++_dl_argv; | |
91f62ce6 | 180 | |
0200214b RM |
181 | l = _dl_map_object (NULL, _dl_argv[0]); |
182 | phdr = l->l_phdr; | |
183 | phent = l->l_phnum; | |
184 | l->l_name = (char *) ""; | |
185 | *user_entry = l->l_entry; | |
186 | } | |
187 | else | |
188 | { | |
189 | /* Create a link_map for the executable itself. | |
190 | This will be what dlopen on "" returns. */ | |
191 | l = _dl_new_object ((char *) "", "", lt_executable); | |
192 | l->l_phdr = phdr; | |
193 | l->l_phnum = phent; | |
194 | interpreter_name = 0; | |
195 | l->l_entry = *user_entry; | |
196 | } | |
197 | ||
198 | if (l != _dl_loaded) | |
199 | { | |
200 | /* GDB assumes that the first element on the chain is the | |
201 | link_map for the executable itself, and always skips it. | |
202 | Make sure the first one is indeed that one. */ | |
203 | l->l_prev->l_next = l->l_next; | |
204 | if (l->l_next) | |
205 | l->l_next->l_prev = l->l_prev; | |
206 | l->l_prev = NULL; | |
207 | l->l_next = _dl_loaded; | |
208 | _dl_loaded->l_prev = l; | |
209 | _dl_loaded = l; | |
210 | } | |
211 | ||
212 | /* Scan the program header table for the dynamic section. */ | |
213 | for (ph = phdr; ph < &phdr[phent]; ++ph) | |
214 | switch (ph->p_type) | |
215 | { | |
216 | case PT_DYNAMIC: | |
217 | /* This tells us where to find the dynamic section, | |
218 | which tells us everything we need to do. */ | |
219 | l->l_ld = (void *) l->l_addr + ph->p_vaddr; | |
220 | break; | |
221 | case PT_INTERP: | |
222 | /* This "interpreter segment" was used by the program loader to | |
223 | find the program interpreter, which is this program itself, the | |
224 | dynamic linker. We note what name finds us, so that a future | |
225 | dlopen call or DT_NEEDED entry, for something that wants to link | |
226 | against the dynamic linker as a shared library, will know that | |
227 | the shared object is already loaded. */ | |
228 | interpreter_name = (void *) l->l_addr + ph->p_vaddr; | |
229 | break; | |
230 | } | |
231 | assert (interpreter_name); /* How else did we get here? */ | |
232 | ||
233 | /* Extract the contents of the dynamic section for easy access. */ | |
234 | elf_get_dynamic_info (l->l_ld, l->l_info); | |
235 | if (l->l_info[DT_HASH]) | |
236 | /* Set up our cache of pointers into the hash table. */ | |
237 | _dl_setup_hash (l); | |
238 | ||
239 | if (l->l_info[DT_DEBUG]) | |
240 | /* There is a DT_DEBUG entry in the dynamic section. Fill it in | |
241 | with the run-time address of the r_debug structure, which we | |
242 | will set up later to communicate with the debugger. */ | |
243 | l->l_info[DT_DEBUG]->d_un.d_ptr = (Elf32_Addr) &dl_r_debug; | |
244 | ||
245 | /* Put the link_map for ourselves on the chain so it can be found by | |
246 | name. */ | |
ee188d55 RM |
247 | _dl_rtld_map.l_name = (char *) _dl_rtld_map.l_libname = interpreter_name; |
248 | _dl_rtld_map.l_type = lt_interpreter; | |
0200214b RM |
249 | while (l->l_next) |
250 | l = l->l_next; | |
ee188d55 RM |
251 | l->l_next = &_dl_rtld_map; |
252 | _dl_rtld_map.l_prev = l; | |
0200214b | 253 | |
efec1d0c RM |
254 | /* Load all the libraries specified by DT_NEEDED entries. */ |
255 | _dl_map_object_deps (l); | |
d66e34cd | 256 | |
efec1d0c RM |
257 | /* XXX if kept, move it so l_next list is in dep order because |
258 | it will determine gdb's search order. | |
259 | Perhaps do this always, so later dlopen by name finds it? | |
260 | XXX But then gdb always considers it present. */ | |
ee188d55 | 261 | if (_dl_rtld_map.l_opencount == 0) |
0200214b | 262 | { |
efec1d0c RM |
263 | /* No DT_NEEDED entry referred to the interpreter object itself, |
264 | so remove it from the list of visible objects. */ | |
ee188d55 RM |
265 | _dl_rtld_map.l_prev->l_next = _dl_rtld_map.l_next; |
266 | _dl_rtld_map.l_next->l_prev = _dl_rtld_map.l_prev; | |
0200214b | 267 | } |
d66e34cd | 268 | |
0200214b RM |
269 | if (list_only) |
270 | { | |
271 | /* We were run just to list the shared libraries. It is | |
272 | important that we do this before real relocation, because the | |
273 | functions we call below for output may no longer work properly | |
274 | after relocation. */ | |
1a3a58fd | 275 | |
0200214b | 276 | int i; |
fd861379 | 277 | |
0200214b RM |
278 | if (! _dl_loaded->l_info[DT_NEEDED]) |
279 | _dl_sysdep_message ("\t", "statically linked\n", NULL); | |
280 | else | |
281 | for (l = _dl_loaded->l_next; l; l = l->l_next) | |
282 | { | |
283 | char buf[20], *bp; | |
284 | buf[sizeof buf - 1] = '\0'; | |
285 | bp = _itoa (l->l_addr, &buf[sizeof buf - 1], 16, 0); | |
286 | while (&buf[sizeof buf - 1] - bp < sizeof l->l_addr * 2) | |
287 | *--bp = '0'; | |
288 | _dl_sysdep_message ("\t", l->l_libname, " => ", l->l_name, | |
289 | " (0x", bp, ")\n", NULL); | |
290 | } | |
1a3a58fd | 291 | |
0200214b RM |
292 | for (i = 1; i < _dl_argc; ++i) |
293 | { | |
294 | const Elf32_Sym *ref = NULL; | |
efec1d0c RM |
295 | struct link_map *scope[2] ={ _dl_loaded, NULL }; |
296 | Elf32_Addr loadbase | |
297 | = _dl_lookup_symbol (_dl_argv[i], &ref, scope, "argument", 0, 0); | |
0200214b RM |
298 | char buf[20], *bp; |
299 | buf[sizeof buf - 1] = '\0'; | |
300 | bp = _itoa (ref->st_value, &buf[sizeof buf - 1], 16, 0); | |
301 | while (&buf[sizeof buf - 1] - bp < sizeof loadbase * 2) | |
302 | *--bp = '0'; | |
303 | _dl_sysdep_message (_dl_argv[i], " found at 0x", bp, NULL); | |
304 | buf[sizeof buf - 1] = '\0'; | |
305 | bp = _itoa (loadbase, &buf[sizeof buf - 1], 16, 0); | |
306 | while (&buf[sizeof buf - 1] - bp < sizeof loadbase * 2) | |
307 | *--bp = '0'; | |
308 | _dl_sysdep_message (" in object at 0x", bp, "\n", NULL); | |
1a3a58fd | 309 | } |
d66e34cd | 310 | |
0200214b RM |
311 | _exit (0); |
312 | } | |
86d2c878 | 313 | |
0200214b RM |
314 | lazy = !_dl_secure && *(getenv ("LD_BIND_NOW") ?: "") == '\0'; |
315 | ||
316 | /* Now we have all the objects loaded. Relocate them all except for | |
317 | the dynamic linker itself. We do this in reverse order so that | |
318 | copy relocs of earlier objects overwrite the data written by later | |
319 | objects. We do not re-relocate the dynamic linker itself in this | |
320 | loop because that could result in the GOT entries for functions we | |
321 | call being changed, and that would break us. It is safe to | |
322 | relocate the dynamic linker out of order because it has no copy | |
323 | relocs (we know that because it is self-contained). */ | |
324 | l = _dl_loaded; | |
325 | while (l->l_next) | |
326 | l = l->l_next; | |
327 | do | |
328 | { | |
ee188d55 | 329 | if (l != &_dl_rtld_map) |
0200214b RM |
330 | _dl_relocate_object (l, lazy); |
331 | l = l->l_prev; | |
332 | } while (l); | |
333 | ||
334 | /* Do any necessary cleanups for the startup OS interface code. | |
335 | We do these now so that no calls are made after rtld re-relocation | |
336 | which might be resolved to different functions than we expect. | |
337 | We cannot do this before relocating the other objects because | |
338 | _dl_relocate_object might need to call `mprotect' for DT_TEXTREL. */ | |
339 | _dl_sysdep_start_cleanup (); | |
340 | ||
ee188d55 | 341 | if (_dl_rtld_map.l_opencount > 0) |
0200214b RM |
342 | /* There was an explicit ref to the dynamic linker as a shared lib. |
343 | Re-relocate ourselves with user-controlled symbol definitions. */ | |
ee188d55 | 344 | _dl_relocate_object (&_dl_rtld_map, lazy); |
0200214b RM |
345 | |
346 | /* Tell the debugger where to find the map of loaded objects. */ | |
347 | dl_r_debug.r_version = 1 /* R_DEBUG_VERSION XXX */; | |
ee188d55 | 348 | dl_r_debug.r_ldbase = _dl_rtld_map.l_addr; /* Record our load address. */ |
0200214b RM |
349 | dl_r_debug.r_map = _dl_loaded; |
350 | dl_r_debug.r_brk = (Elf32_Addr) &_dl_r_debug_state; | |
351 | ||
ee188d55 | 352 | if (_dl_rtld_map.l_info[DT_INIT]) |
0200214b RM |
353 | { |
354 | /* Call the initializer for the compatibility version of the | |
355 | dynamic linker. There is no additional initialization | |
356 | required for the ABI-compliant dynamic linker. */ | |
86d2c878 | 357 | |
ee188d55 RM |
358 | (*(void (*) (void)) (_dl_rtld_map.l_addr + |
359 | _dl_rtld_map.l_info[DT_INIT]->d_un.d_ptr)) (); | |
0200214b RM |
360 | |
361 | /* Clear the field so a future dlopen won't run it again. */ | |
ee188d55 | 362 | _dl_rtld_map.l_info[DT_INIT] = NULL; |
421f82e5 | 363 | } |
d66e34cd RM |
364 | |
365 | /* Once we return, _dl_sysdep_start will invoke | |
366 | the DT_INIT functions and then *USER_ENTRY. */ | |
367 | } | |
368 | ||
86d2c878 | 369 | /* This function exists solely to have a breakpoint set on it by the |
d66e34cd RM |
370 | debugger. */ |
371 | void | |
372 | _dl_r_debug_state (void) | |
373 | { | |
374 | } |