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1 /* Run time dynamic linker.
2 Copyright (C) 1995 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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.
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.
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. */
21 #include "dynamic-link.h"
25 #include "../stdio-common/_itoa.h"
31 #error "sysdeps/MACHINE/dl-machine.h fails to define RTLD_START"
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
,
41 Elf32_Addr
*user_entry
));
47 struct r_debug dl_r_debug
;
49 static void dl_main (const Elf32_Phdr
*phdr
,
51 Elf32_Addr
*user_entry
);
53 static struct link_map rtld_map
;
58 struct link_map bootstrap_map
;
60 /* Figure out the run-time load address of the dynamic linker itself. */
61 bootstrap_map
.l_addr
= elf_machine_load_address ();
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. */
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
);
69 #ifdef ELF_MACHINE_BEFORE_RTLD_RELOC
70 ELF_MACHINE_BEFORE_RTLD_RELOC (bootstrap_map
.l_info
);
73 /* Relocate ourselves so we can do normal function calls and
74 data access using the global offset table. */
76 /* We must initialize `l_type' to make sure it is not `lt_interpreter'.
77 That is the type to describe us, but not during bootstrapping--it
78 indicates to elf_machine_rel{,a} that we were already relocated during
79 bootstrapping, so it must anti-perform each bootstrapping relocation
80 before applying the final relocation when ld.so is linked in as
81 normal a shared library. */
82 bootstrap_map
.l_type
= lt_library
;
83 ELF_DYNAMIC_RELOCATE (&bootstrap_map
, 0, NULL
);
86 /* Now life is sane; we can call functions and access global data.
87 Set up to use the operating system facilities, and find out from
88 the operating system's program loader where to find the program
89 header table in core. */
92 /* Transfer data about ourselves to the permanent link_map structure. */
93 rtld_map
.l_addr
= bootstrap_map
.l_addr
;
94 rtld_map
.l_ld
= bootstrap_map
.l_ld
;
95 memcpy (rtld_map
.l_info
, bootstrap_map
.l_info
, sizeof rtld_map
.l_info
);
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. */
102 return _dl_sysdep_start (&arg
, &dl_main
);
106 /* Now life is peachy; we can do all normal operations.
107 On to the real work. */
111 unsigned int _dl_skip_args
; /* Nonzero if we were run directly. */
114 dl_main (const Elf32_Phdr
*phdr
,
116 Elf32_Addr
*user_entry
)
120 const Elf32_Phdr
*ph
;
122 const char *interpreter_name
;
126 if (*user_entry
== (Elf32_Addr
) &_start
)
128 /* Ho ho. We are not the program interpreter! We are the program
129 itself! This means someone ran ld.so as a command. Well, that
130 might be convenient to do sometimes. We support it by
131 interpreting the args like this:
133 ld.so PROGRAM ARGS...
135 The first argument is the name of a file containing an ELF
136 executable we will load and run with the following arguments.
137 To simplify life here, PROGRAM is searched for using the
138 normal rules for shared objects, rather than $PATH or anything
139 like that. We just load it and use its entry point; we don't
140 pay attention to its PT_INTERP command (we are the interpreter
141 ourselves). This is an easy way to test a new ld.so before
145 Usage: ld.so [--list] EXECUTABLE-FILE [ARGS-FOR-PROGRAM...]\n\
146 You have invoked `ld.so', the helper program for shared library executables.\n\
147 This program usually lives in the file `/lib/ld.so', and special directives\n\
148 in executable files using ELF shared libraries tell the system's program\n\
149 loader to load the helper program from this file. This helper program loads\n\
150 the shared libraries needed by the program executable, prepares the program\n\
151 to run, and runs it. You may invoke this helper program directly from the\n\
152 command line to load and run an ELF executable file; this is like executing\n\
153 that file itself, but always uses this helper program from the file you\n\
154 specified, instead of the helper program file specified in the executable\n\
155 file you run. This is mostly of use for maintainers to test new versions\n\
156 of this helper program; chances are you did not intend to run this program.\n",
159 interpreter_name
= _dl_argv
[0];
161 if (! strcmp (_dl_argv
[1], "--list"))
174 l
= _dl_map_object (NULL
, _dl_argv
[0]);
177 l
->l_type
= lt_executable
;
178 l
->l_libname
= (char *) "";
179 *user_entry
= l
->l_entry
;
183 /* Create a link_map for the executable itself.
184 This will be what dlopen on "" returns. */
185 l
= _dl_new_object ((char *) "", "", lt_executable
);
188 interpreter_name
= 0;
189 l
->l_entry
= *user_entry
;
194 /* GDB assumes that the first element on the chain is the
195 link_map for the executable itself, and always skips it.
196 Make sure the first one is indeed that one. */
197 l
->l_prev
->l_next
= l
->l_next
;
199 l
->l_next
->l_prev
= l
->l_prev
;
201 l
->l_next
= _dl_loaded
;
202 _dl_loaded
->l_prev
= l
;
206 /* Scan the program header table for the dynamic section. */
207 for (ph
= phdr
; ph
< &phdr
[phent
]; ++ph
)
211 /* This tells us where to find the dynamic section,
212 which tells us everything we need to do. */
213 l
->l_ld
= (void *) l
->l_addr
+ ph
->p_vaddr
;
216 /* This "interpreter segment" was used by the program loader to
217 find the program interpreter, which is this program itself, the
218 dynamic linker. We note what name finds us, so that a future
219 dlopen call or DT_NEEDED entry, for something that wants to link
220 against the dynamic linker as a shared library, will know that
221 the shared object is already loaded. */
222 interpreter_name
= (void *) l
->l_addr
+ ph
->p_vaddr
;
225 assert (interpreter_name
); /* How else did we get here? */
227 /* Extract the contents of the dynamic section for easy access. */
228 elf_get_dynamic_info (l
->l_ld
, l
->l_info
);
229 if (l
->l_info
[DT_HASH
])
230 /* Set up our cache of pointers into the hash table. */
233 if (l
->l_info
[DT_DEBUG
])
234 /* There is a DT_DEBUG entry in the dynamic section. Fill it in
235 with the run-time address of the r_debug structure, which we
236 will set up later to communicate with the debugger. */
237 l
->l_info
[DT_DEBUG
]->d_un
.d_ptr
= (Elf32_Addr
) &dl_r_debug
;
239 /* Put the link_map for ourselves on the chain so it can be found by
241 rtld_map
.l_name
= (char *) rtld_map
.l_libname
= interpreter_name
;
242 rtld_map
.l_type
= lt_interpreter
;
245 l
->l_next
= &rtld_map
;
248 /* Now process all the DT_NEEDED entries and map in the objects.
249 Each new link_map will go on the end of the chain, so we will
250 come across it later in the loop to map in its dependencies. */
251 for (l
= _dl_loaded
; l
; l
= l
->l_next
)
253 if (l
->l_info
[DT_NEEDED
])
256 = (void *) l
->l_addr
+ l
->l_info
[DT_STRTAB
]->d_un
.d_ptr
;
258 for (d
= l
->l_ld
; d
->d_tag
!= DT_NULL
; ++d
)
259 if (d
->d_tag
== DT_NEEDED
)
260 _dl_map_object (l
, strtab
+ d
->d_un
.d_val
);
262 l
->l_deps_loaded
= 1;
265 if (rtld_map
.l_opencount
== 0)
267 /* No DT_NEEDED entry referred to the interpreter object itself.
268 Remove it from the maps we will use for symbol resolution. */
269 rtld_map
.l_prev
->l_next
= rtld_map
.l_next
;
271 rtld_map
.l_next
->l_prev
= rtld_map
.l_prev
;
274 lazy
= !_dl_secure
&& *(getenv ("LD_BIND_NOW") ?: "") == '\0';
276 /* Now we have all the objects loaded. Relocate them all.
277 We do this in reverse order so that copy relocs of earlier
278 objects overwrite the data written by later objects. */
284 _dl_relocate_object (l
, lazy
);
288 /* Tell the debugger where to find the map of loaded objects. */
289 dl_r_debug
.r_version
= 1 /* R_DEBUG_VERSION XXX */;
290 dl_r_debug
.r_ldbase
= rtld_map
.l_addr
; /* Record our load address. */
291 dl_r_debug
.r_map
= _dl_loaded
;
292 dl_r_debug
.r_brk
= (Elf32_Addr
) &_dl_r_debug_state
;
296 if (! _dl_loaded
->l_info
[DT_NEEDED
])
298 _dl_sysdep_message (_dl_loaded
->l_name
, ": statically linked\n",
303 for (l
= _dl_loaded
->l_next
; l
; l
= l
->l_next
)
306 buf
[sizeof buf
- 1] = '\0';
307 bp
= _itoa (l
->l_addr
, &buf
[sizeof buf
- 1], 16, 0);
308 while (&buf
[sizeof buf
- 1] - bp
< sizeof l
->l_addr
* 2)
310 _dl_sysdep_message ("\t", l
->l_libname
, " => ", l
->l_name
,
311 " (0x", bp
, ")\n", NULL
);
317 if (rtld_map
.l_info
[DT_INIT
])
319 /* Call the initializer for the compatibility version of the
320 dynamic linker. There is no additional initialization
321 required for the ABI-compliant dynamic linker. */
323 (*(void (*) (void)) (rtld_map
.l_addr
+
324 rtld_map
.l_info
[DT_INIT
]->d_un
.d_ptr
)) ();
326 /* Clear the field so a future dlopen won't run it again. */
327 rtld_map
.l_info
[DT_INIT
] = NULL
;
330 const char *errstring
;
334 err
= _dl_catch_error (&errstring
, &errobj
, &doit
);
336 _dl_sysdep_fatal (_dl_argv
[0] ?: "<program name unknown>",
337 ": error in loading shared libraries\n",
338 errobj
?: "", errobj
? ": " : "",
339 errstring
, err
? ": " : "",
340 err
? strerror (err
) : "", "\n", NULL
);
342 /* Once we return, _dl_sysdep_start will invoke
343 the DT_INIT functions and then *USER_ENTRY. */
346 /* This function exists solely to have a breakpoint set on it by the
349 _dl_r_debug_state (void)
353 /* Define our own stub for the localization function used by strerror.
354 English-only in the dynamic linker keeps it smaller. */
357 __dgettext (const char *domainname
, const char *msgid
)
359 assert (domainname
== _libc_intl_domainname
);
360 return (char *) msgid
;
362 weak_symbol (__dgettext
)
363 weak_alias (__dgettext
, dgettext
)
367 /* Define (weakly) our own assert failure function which doesn't use stdio.
368 If we are linked into the user program (-ldl), the normal __assert_fail
369 defn can override this one. */
372 __assert_fail (const char *assertion
,
373 const char *file
, unsigned int line
, const char *function
)
376 buf
[sizeof buf
- 1] = '\0';
377 _dl_sysdep_fatal ("BUG IN DYNAMIC LINKER ld.so: ",
378 file
, ": ", _itoa (line
, buf
+ sizeof buf
- 1, 10, 0),
379 ": ", function
?: "", function
? ": " : "",
380 "Assertion `", assertion
, "' failed!\n",
384 weak_symbol (__assert_fail
)
387 __assert_perror_fail (int errnum
,
388 const char *file
, unsigned int line
,
389 const char *function
)
392 buf
[sizeof buf
- 1] = '\0';
393 _dl_sysdep_fatal ("BUG IN DYNAMIC LINKER ld.so: ",
394 file
, ": ", _itoa (line
, buf
+ sizeof buf
- 1, 10, 0),
395 ": ", function
?: "", function
? ": " : "",
396 "Unexpected error: ", strerror (errnum
), "\n", NULL
);
399 weak_symbol (__assert_perror_fail
)
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