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d66e34cd RM |
1 | /* Run time dynamic linker. |
2 | Copyright (C) 1995 Free Software Foundation, Inc. | |
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> | |
25 | ||
26 | ||
27 | #ifdef RTLD_START | |
28 | RTLD_START | |
29 | #else | |
30 | #error "sysdeps/MACHINE/dl-machine.h fails to define RTLD_START" | |
31 | #endif | |
32 | ||
33 | /* System-specific function to do initial startup for the dynamic linker. | |
34 | After this, file access calls and getenv must work. This is responsible | |
35 | for setting _dl_secure if we need to be secure (e.g. setuid), | |
36 | and for setting _dl_argc and _dl_argv, and then calling _dl_main. */ | |
37 | extern Elf32_Addr _dl_sysdep_start (void **start_argptr, | |
38 | void (*dl_main) (const Elf32_Phdr *phdr, | |
39 | Elf32_Word phent, | |
40 | Elf32_Addr *user_entry)); | |
41 | ||
42 | int _dl_secure; | |
43 | int _dl_argc; | |
44 | char **_dl_argv; | |
45 | ||
46 | struct r_debug dl_r_debug; | |
47 | ||
48 | static void dl_main (const Elf32_Phdr *phdr, | |
49 | Elf32_Word phent, | |
50 | Elf32_Addr *user_entry); | |
51 | ||
52 | Elf32_Addr | |
53 | _dl_start (void *arg) | |
54 | { | |
421f82e5 | 55 | struct link_map rtld_map; |
d66e34cd RM |
56 | |
57 | /* Figure out the run-time load address of the dynamic linker itself. */ | |
421f82e5 | 58 | rtld_map.l_addr = elf_machine_load_address (); |
d66e34cd RM |
59 | |
60 | /* Read our own dynamic section and fill in the info array. | |
61 | Conveniently, the first element of the GOT contains the | |
62 | offset of _DYNAMIC relative to the run-time load address. */ | |
421f82e5 RM |
63 | rtld_map.l_ld = (void *) rtld_map.l_addr + *elf_machine_got (); |
64 | elf_get_dynamic_info (rtld_map.l_ld, rtld_map.l_info); | |
d66e34cd RM |
65 | |
66 | #ifdef ELF_MACHINE_BEFORE_RTLD_RELOC | |
421f82e5 | 67 | ELF_MACHINE_BEFORE_RTLD_RELOC (rtld_map.l_info); |
d66e34cd RM |
68 | #endif |
69 | ||
70 | /* Relocate ourselves so we can do normal function calls and | |
71 | data access using the global offset table. */ | |
421f82e5 | 72 | |
ded29119 RM |
73 | /* We must initialize `l_type' to make sure it is not `lt_interpreter'. |
74 | That is the type to describe us, but not during bootstrapping--it | |
75 | indicates to elf_machine_rel{,a} that we were already relocated during | |
76 | bootstrapping, so it must anti-perform each bootstrapping relocation | |
77 | before applying the final relocation when ld.so is linked in as | |
78 | normal a shared library. */ | |
79 | rtld_map.l_type = lt_library; | |
421f82e5 RM |
80 | ELF_DYNAMIC_RELOCATE (&rtld_map, 0, NULL); |
81 | ||
d66e34cd RM |
82 | |
83 | /* Now life is sane; we can call functions and access global data. | |
84 | Set up to use the operating system facilities, and find out from | |
85 | the operating system's program loader where to find the program | |
86 | header table in core. */ | |
87 | ||
421f82e5 | 88 | dl_r_debug.r_ldbase = rtld_map.l_addr; /* Record our load address. */ |
d66e34cd RM |
89 | |
90 | /* Call the OS-dependent function to set up life so we can do things like | |
91 | file access. It will call `dl_main' (below) to do all the real work | |
92 | of the dynamic linker, and then unwind our frame and run the user | |
93 | entry point on the same stack we entered on. */ | |
94 | return _dl_sysdep_start (&arg, &dl_main); | |
95 | } | |
96 | ||
97 | ||
98 | /* Now life is peachy; we can do all normal operations. | |
99 | On to the real work. */ | |
100 | ||
101 | void _start (void); | |
102 | ||
a1a9d215 RM |
103 | static int rtld_command; /* Nonzero if we were run directly. */ |
104 | ||
d66e34cd RM |
105 | static void |
106 | dl_main (const Elf32_Phdr *phdr, | |
107 | Elf32_Word phent, | |
108 | Elf32_Addr *user_entry) | |
109 | { | |
110 | void doit (void) | |
111 | { | |
421f82e5 RM |
112 | const Elf32_Phdr *ph; |
113 | struct link_map *l; | |
114 | const char *interpreter_name; | |
115 | int lazy; | |
d66e34cd | 116 | |
421f82e5 RM |
117 | if (*user_entry == (Elf32_Addr) &_start) |
118 | { | |
119 | /* Ho ho. We are not the program interpreter! We are the program | |
120 | itself! This means someone ran ld.so as a command. Well, that | |
121 | might be convenient to do sometimes. We support it by | |
122 | interpreting the args like this: | |
123 | ||
124 | ld.so PROGRAM ARGS... | |
125 | ||
126 | The first argument is the name of a file containing an ELF | |
127 | executable we will load and run with the following arguments. | |
128 | To simplify life here, PROGRAM is searched for using the | |
129 | normal rules for shared objects, rather than $PATH or anything | |
130 | like that. We just load it and use its entry point; we don't | |
131 | pay attention to its PT_INTERP command (we are the interpreter | |
132 | ourselves). This is an easy way to test a new ld.so before | |
133 | installing it. */ | |
134 | if (_dl_argc < 2) | |
135 | _dl_sysdep_fatal ("\ | |
d66e34cd RM |
136 | Usage: ld.so EXECUTABLE-FILE [ARGS-FOR-PROGRAM...]\n\ |
137 | You have invoked `ld.so', the helper program for shared library executables.\n\ | |
138 | This program usually lives in the file `/lib/ld.so', and special directives\n\ | |
139 | in executable files using ELF shared libraries tell the system's program\n\ | |
140 | loader to load the helper program from this file. This helper program loads\n\ | |
141 | the shared libraries needed by the program executable, prepares the program\n\ | |
142 | to run, and runs it. You may invoke this helper program directly from the\n\ | |
143 | command line to load and run an ELF executable file; this is like executing\n\ | |
144 | that file itself, but always uses this helper program from the file you\n\ | |
145 | specified, instead of the helper program file specified in the executable\n\ | |
146 | file you run. This is mostly of use for maintainers to test new versions\n\ | |
147 | of this helper program; chances are you did not intend to run this program.\n" | |
421f82e5 RM |
148 | ); |
149 | ||
a1a9d215 | 150 | rtld_command = 1; |
421f82e5 RM |
151 | interpreter_name = _dl_argv[0]; |
152 | --_dl_argc; | |
153 | ++_dl_argv; | |
154 | l = _dl_map_object (NULL, _dl_argv[0], user_entry); | |
155 | phdr = l->l_phdr; | |
156 | phent = l->l_phnum; | |
157 | l->l_type = lt_executable; | |
158 | l->l_libname = (char *) ""; | |
159 | } | |
160 | else | |
161 | { | |
162 | /* Create a link_map for the executable itself. | |
163 | This will be what dlopen on "" returns. */ | |
164 | l = _dl_new_object ((char *) "", "", lt_executable); | |
165 | l->l_phdr = phdr; | |
166 | l->l_phnum = phent; | |
167 | interpreter_name = 0; | |
168 | } | |
d66e34cd | 169 | |
421f82e5 RM |
170 | /* Scan the program header table for the dynamic section. */ |
171 | for (ph = phdr; ph < &phdr[phent]; ++ph) | |
172 | switch (ph->p_type) | |
173 | { | |
174 | case PT_DYNAMIC: | |
175 | /* This tells us where to find the dynamic section, | |
176 | which tells us everything we need to do. */ | |
a1a9d215 | 177 | l->l_ld = (void *) l->l_addr + ph->p_vaddr; |
421f82e5 RM |
178 | break; |
179 | case PT_INTERP: | |
180 | /* This "interpreter segment" was used by the program loader to | |
181 | find the program interpreter, which is this program itself, the | |
182 | dynamic linker. We note what name finds us, so that a future | |
183 | dlopen call or DT_NEEDED entry, for something that wants to link | |
184 | against the dynamic linker as a shared library, will know that | |
185 | the shared object is already loaded. */ | |
a1a9d215 | 186 | interpreter_name = (void *) l->l_addr + ph->p_vaddr; |
421f82e5 RM |
187 | break; |
188 | } | |
189 | assert (interpreter_name); /* How else did we get here? */ | |
190 | ||
191 | /* Extract the contents of the dynamic section for easy access. */ | |
192 | elf_get_dynamic_info (l->l_ld, l->l_info); | |
193 | /* Set up our cache of pointers into the hash table. */ | |
194 | _dl_setup_hash (l); | |
195 | ||
196 | if (l->l_info[DT_DEBUG]) | |
197 | /* There is a DT_DEBUG entry in the dynamic section. Fill it in | |
198 | with the run-time address of the r_debug structure, which we | |
199 | will set up later to communicate with the debugger. */ | |
200 | l->l_info[DT_DEBUG]->d_un.d_ptr = (Elf32_Addr) &dl_r_debug; | |
201 | ||
202 | l = _dl_new_object ((char *) interpreter_name, interpreter_name, | |
203 | lt_interpreter); | |
204 | ||
205 | /* Now process all the DT_NEEDED entries and map in the objects. | |
206 | Each new link_map will go on the end of the chain, so we will | |
207 | come across it later in the loop to map in its dependencies. */ | |
208 | for (l = _dl_loaded; l; l = l->l_next) | |
d66e34cd | 209 | { |
421f82e5 RM |
210 | if (l->l_info[DT_NEEDED]) |
211 | { | |
212 | const char *strtab | |
213 | = (void *) l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr; | |
214 | const Elf32_Dyn *d; | |
215 | for (d = l->l_ld; d->d_tag != DT_NULL; ++d) | |
216 | if (d->d_tag == DT_NEEDED) | |
217 | _dl_map_object (l, strtab + d->d_un.d_val, NULL); | |
218 | } | |
219 | l->l_deps_loaded = 1; | |
d66e34cd | 220 | } |
d66e34cd | 221 | |
421f82e5 RM |
222 | l = _dl_loaded->l_next; |
223 | assert (l->l_type == lt_interpreter); | |
224 | if (l->l_opencount == 0) | |
225 | { | |
226 | /* No DT_NEEDED entry referred to the interpreter object itself. | |
227 | Remove it from the maps we will use for symbol resolution. */ | |
228 | l->l_prev->l_next = l->l_next; | |
229 | if (l->l_next) | |
230 | l->l_next->l_prev = l->l_prev; | |
231 | } | |
d66e34cd | 232 | |
a1a9d215 | 233 | lazy = !_dl_secure && *(getenv ("LD_BIND_NOW") ?: "") == '\0'; |
d66e34cd | 234 | |
421f82e5 RM |
235 | /* Now we have all the objects loaded. Relocate them all. |
236 | We do this in reverse order so that copy relocs of earlier | |
237 | objects overwrite the data written by later objects. */ | |
238 | l = _dl_loaded; | |
239 | while (l->l_next) | |
240 | l = l->l_next; | |
241 | do | |
242 | { | |
243 | _dl_relocate_object (l, lazy); | |
244 | l = l->l_prev; | |
245 | } while (l); | |
246 | ||
247 | /* Tell the debugger where to find the map of loaded objects. */ | |
248 | dl_r_debug.r_version = 1 /* R_DEBUG_VERSION XXX */; | |
249 | dl_r_debug.r_map = _dl_loaded; | |
250 | dl_r_debug.r_brk = (Elf32_Addr) &_dl_r_debug_state; | |
251 | } | |
d66e34cd | 252 | const char *errstring; |
421f82e5 | 253 | const char *errobj; |
d66e34cd RM |
254 | int err; |
255 | ||
421f82e5 | 256 | err = _dl_catch_error (&errstring, &errobj, &doit); |
d66e34cd RM |
257 | if (errstring) |
258 | _dl_sysdep_fatal (_dl_argv[0] ?: "<program name unknown>", | |
259 | ": error in loading shared libraries\n", | |
421f82e5 | 260 | errobj ?: "", errobj ? ": " : "", |
d66e34cd RM |
261 | errstring, err ? ": " : NULL, |
262 | err ? strerror (err) : NULL, NULL); | |
263 | ||
264 | /* Once we return, _dl_sysdep_start will invoke | |
265 | the DT_INIT functions and then *USER_ENTRY. */ | |
266 | } | |
267 | ||
268 | /* This function exists solely to have a breakpoint set on it by the | |
269 | debugger. */ | |
270 | void | |
271 | _dl_r_debug_state (void) | |
272 | { | |
273 | } | |
273d56ce RM |
274 | \f |
275 | #ifndef NDEBUG | |
276 | ||
277 | /* Define (weakly) our own assert failure function which doesn't use stdio. | |
278 | If we are linked into the user program (-ldl), the normal __assert_fail | |
279 | defn can override this one. */ | |
280 | ||
281 | #include "../stdio/_itoa.h" | |
282 | ||
283 | void | |
284 | __assert_fail (const char *assertion, | |
285 | const char *file, unsigned int line, const char *function) | |
286 | { | |
287 | char buf[64]; | |
288 | buf[sizeof buf - 1] = '\0'; | |
289 | _dl_sysdep_fatal ("BUG IN DYNAMIC LINKER ld.so: ", | |
290 | file, ": ", _itoa (line, buf + sizeof buf - 1, 10, 0), | |
291 | ": ", function ?: "", function ? ": " : "", | |
292 | "Assertion `", assertion, "' failed!\n"); | |
293 | ||
294 | } | |
295 | weak_symbol (__assert_fail) | |
296 | ||
297 | #endif |