1 /* Support for dynamic linking code in static libc.
2 Copyright (C) 1996-2020 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 Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the 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 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
19 /* This file defines some things that for the dynamic linker are defined in
20 rtld.c and dl-sysdep.c in ways appropriate to bootstrap dynamic linking. */
26 #include <sys/param.h>
29 #include <dl-machine.h>
30 #include <libc-lock.h>
32 #include <dl-librecon.h>
33 #include <dl-procinfo.h>
34 #include <unsecvars.h>
35 #include <hp-timing.h>
36 #include <stackinfo.h>
38 #include <dl-vdso-setup.h>
40 extern char *__progname
;
41 char **_dl_argv
= &__progname
; /* This is checked for some error messages. */
43 /* Name of the architecture. */
44 const char *_dl_platform
;
45 size_t _dl_platformlen
;
49 ElfW(Addr
) _dl_use_load_bias
= -2;
52 /* If nonzero print warnings about problematic situations. */
55 /* We never do profiling. */
56 const char *_dl_profile
;
57 const char *_dl_profile_output
;
59 /* Names of shared object for which the RUNPATHs and RPATHs should be
61 const char *_dl_inhibit_rpath
;
63 /* The map for the object we will profile. */
64 struct link_map
*_dl_profile_map
;
66 /* This is the address of the last stack address ever used. */
67 void *__libc_stack_end
;
69 /* Path where the binary is found. */
70 const char *_dl_origin_path
;
72 /* Nonzero if runtime lookup should not update the .got/.plt. */
75 /* A dummy link map for the executable, used by dlopen to access the global
76 scope. We don't export any symbols ourselves, so this can be minimal. */
77 static struct link_map _dl_main_map
=
79 .l_name
= (char *) "",
80 .l_real
= &_dl_main_map
,
82 .l_libname
= &(struct libname_list
) { .name
= "", .dont_free
= 1 },
85 .r_list
= &(struct link_map
*) { &_dl_main_map
},
88 .l_symbolic_searchlist
= { .r_list
= &(struct link_map
*) { NULL
} },
89 .l_type
= lt_executable
,
90 .l_scope_mem
= { &_dl_main_map
.l_searchlist
},
91 .l_scope_max
= (sizeof (_dl_main_map
.l_scope_mem
)
92 / sizeof (_dl_main_map
.l_scope_mem
[0])),
93 .l_scope
= _dl_main_map
.l_scope_mem
,
94 .l_local_scope
= { &_dl_main_map
.l_searchlist
},
96 .l_tls_offset
= NO_TLS_OFFSET
,
100 /* Namespace information. */
101 struct link_namespaces _dl_ns
[DL_NNS
] =
105 ._ns_loaded
= &_dl_main_map
,
107 ._ns_main_searchlist
= &_dl_main_map
.l_searchlist
,
112 /* Incremented whenever something may have been added to dl_loaded. */
113 unsigned long long _dl_load_adds
= 1;
115 /* Fake scope of the main application. */
116 struct r_scope_elem _dl_initial_searchlist
=
118 .r_list
= &(struct link_map
*) { &_dl_main_map
},
122 #ifndef HAVE_INLINED_SYSCALLS
123 /* Nonzero during startup. */
124 int _dl_starting_up
= 1;
127 /* Random data provided by the kernel. */
130 /* Get architecture specific initializer. */
131 #include <dl-procruntime.c>
132 #include <dl-procinfo.c>
134 void (*_dl_init_static_tls
) (struct link_map
*) = &_dl_nothread_init_static_tls
;
136 size_t _dl_pagesize
= EXEC_PAGESIZE
;
138 int _dl_inhibit_cache
;
140 unsigned int _dl_osversion
;
142 /* All known directories in sorted order. */
143 struct r_search_path_elem
*_dl_all_dirs
;
145 /* All directories after startup. */
146 struct r_search_path_elem
*_dl_init_all_dirs
;
148 /* The object to be initialized first. */
149 struct link_map
*_dl_initfirst
;
151 /* Descriptor to write debug messages to. */
152 int _dl_debug_fd
= STDERR_FILENO
;
154 int _dl_correct_cache_id
= _DL_CACHE_DEFAULT_ID
;
156 ElfW(auxv_t
) *_dl_auxv
;
157 const ElfW(Phdr
) *_dl_phdr
;
159 uint64_t _dl_hwcap
__attribute__ ((nocommon
));
160 uint64_t _dl_hwcap2
__attribute__ ((nocommon
));
162 /* The value of the FPU control word the kernel will preset in hardware. */
163 fpu_control_t _dl_fpu_control
= _FPU_DEFAULT
;
166 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
167 of _dl_important_hwcaps, below, where no hwcap strings are ever
168 used. This mask is still used to mediate the lookups in the cache
169 file. Since there is no way to set this nonzero (we don't grok the
170 LD_HWCAP_MASK environment variable here), there is no real point in
171 setting _dl_hwcap nonzero below, but we do anyway. */
172 uint64_t _dl_hwcap_mask
__attribute__ ((nocommon
));
175 /* Prevailing state of the stack. Generally this includes PF_X, indicating it's
176 * executable but this isn't true for all platforms. */
177 ElfW(Word
) _dl_stack_flags
= DEFAULT_STACK_PERMS
;
179 /* If loading a shared object requires that we make the stack executable
180 when it was not, we do it by calling this function.
181 It returns an errno code or zero on success. */
182 int (*_dl_make_stack_executable_hook
) (void **) = _dl_make_stack_executable
;
185 /* Function in libpthread to wait for termination of lookups. */
186 void (*_dl_wait_lookup_done
) (void);
188 #if !THREAD_GSCOPE_IN_TCB
189 int _dl_thread_gscope_count
;
191 struct dl_scope_free_list
*_dl_scope_free_list
;
193 #ifdef NEED_DL_SYSINFO
194 /* Needed for improved syscall handling on at least x86/Linux. */
195 uintptr_t _dl_sysinfo
= DL_SYSINFO_DEFAULT
;
197 #ifdef NEED_DL_SYSINFO_DSO
198 /* Address of the ELF headers in the vsyscall page. */
199 const ElfW(Ehdr
) *_dl_sysinfo_dso
;
201 struct link_map
*_dl_sysinfo_map
;
203 # include "get-dynamic-info.h"
205 #include "setup-vdso.h"
206 /* Define the vDSO function pointers. */
207 #include <dl-vdso-setup.c>
209 /* During the program run we must not modify the global data of
210 loaded shared object simultanously in two threads. Therefore we
211 protect `_dl_open' and `_dl_close' in dl-close.c.
213 This must be a recursive lock since the initializer function of
214 the loaded object might as well require a call to this function.
215 At this time it is not anymore a problem to modify the tables. */
216 __rtld_lock_define_initialized_recursive (, _dl_load_lock
)
217 /* This lock is used to keep __dl_iterate_phdr from inspecting the
218 list of loaded objects while an object is added to or removed from
220 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock
)
223 #ifdef HAVE_AUX_VECTOR
227 _dl_aux_init (ElfW(auxv_t
) *av
)
234 for (; av
->a_type
!= AT_NULL
; ++av
)
238 if (av
->a_un
.a_val
!= 0)
239 GLRO(dl_pagesize
) = av
->a_un
.a_val
;
242 GLRO(dl_clktck
) = av
->a_un
.a_val
;
245 GL(dl_phdr
) = (const void *) av
->a_un
.a_val
;
248 GL(dl_phnum
) = av
->a_un
.a_val
;
251 GLRO(dl_platform
) = (void *) av
->a_un
.a_val
;
254 GLRO(dl_hwcap
) = (unsigned long int) av
->a_un
.a_val
;
257 GLRO(dl_hwcap2
) = (unsigned long int) av
->a_un
.a_val
;
260 GLRO(dl_fpu_control
) = av
->a_un
.a_val
;
262 #ifdef NEED_DL_SYSINFO
264 GL(dl_sysinfo
) = av
->a_un
.a_val
;
267 #ifdef NEED_DL_SYSINFO_DSO
268 case AT_SYSINFO_EHDR
:
269 GL(dl_sysinfo_dso
) = (void *) av
->a_un
.a_val
;
273 uid
^= av
->a_un
.a_val
;
277 uid
^= av
->a_un
.a_val
;
281 gid
^= av
->a_un
.a_val
;
285 gid
^= av
->a_un
.a_val
;
290 __libc_enable_secure
= av
->a_un
.a_val
;
291 __libc_enable_secure_decided
= 1;
294 _dl_random
= (void *) av
->a_un
.a_val
;
296 # ifdef DL_PLATFORM_AUXV
302 __libc_enable_secure
= uid
!= 0 || gid
!= 0;
303 __libc_enable_secure_decided
= 1;
310 _dl_non_dynamic_init (void)
312 _dl_main_map
.l_origin
= _dl_get_origin ();
313 _dl_main_map
.l_phdr
= GL(dl_phdr
);
314 _dl_main_map
.l_phnum
= GL(dl_phnum
);
316 _dl_verbose
= *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
318 /* Set up the data structures for the system-supplied DSO early,
319 so they can influence _dl_init_paths. */
320 setup_vdso (NULL
, NULL
);
322 /* With vDSO setup we can initialize the function pointers. */
323 setup_vdso_pointers ();
325 /* Initialize the data structures for the search paths for shared
327 _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
329 /* Remember the last search directory added at startup. */
330 _dl_init_all_dirs
= GL(dl_all_dirs
);
332 _dl_lazy
= *(getenv ("LD_BIND_NOW") ?: "") == '\0';
334 _dl_bind_not
= *(getenv ("LD_BIND_NOT") ?: "") != '\0';
336 _dl_dynamic_weak
= *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
338 _dl_profile_output
= getenv ("LD_PROFILE_OUTPUT");
339 if (_dl_profile_output
== NULL
|| _dl_profile_output
[0] == '\0')
341 = &"/var/tmp\0/var/profile"[__libc_enable_secure
? 9 : 0];
343 if (__libc_enable_secure
)
345 static const char unsecure_envvars
[] =
347 #ifdef EXTRA_UNSECURE_ENVVARS
348 EXTRA_UNSECURE_ENVVARS
351 const char *cp
= unsecure_envvars
;
353 while (cp
< unsecure_envvars
+ sizeof (unsecure_envvars
))
356 cp
= (const char *) __rawmemchr (cp
, '\0') + 1;
360 if (__access ("/etc/suid-debug", F_OK
) != 0)
361 __unsetenv ("MALLOC_CHECK_");
365 #ifdef DL_PLATFORM_INIT
369 #ifdef DL_OSVERSION_INIT
373 /* Now determine the length of the platform string. */
374 if (_dl_platform
!= NULL
)
375 _dl_platformlen
= strlen (_dl_platform
);
377 if (_dl_phdr
!= NULL
)
378 for (const ElfW(Phdr
) *ph
= _dl_phdr
; ph
< &_dl_phdr
[_dl_phnum
]; ++ph
)
381 /* Check if the stack is nonexecutable. */
383 _dl_stack_flags
= ph
->p_flags
;
387 _dl_main_map
.l_relro_addr
= ph
->p_vaddr
;
388 _dl_main_map
.l_relro_size
= ph
->p_memsz
;
392 /* Setup relro on the binary itself. */
393 if (_dl_main_map
.l_relro_size
!= 0)
394 _dl_protect_relro (&_dl_main_map
);
397 #ifdef DL_SYSINFO_IMPLEMENTATION
398 DL_SYSINFO_IMPLEMENTATION
401 #if ENABLE_STATIC_PIE
402 /* Since relocation to hidden _dl_main_map causes relocation overflow on
403 aarch64, a function is used to get the address of _dl_main_map. */
406 _dl_get_dl_main_map (void)
408 return &_dl_main_map
;