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>
41 extern char *__progname
;
42 char **_dl_argv
= &__progname
; /* This is checked for some error messages. */
44 /* Name of the architecture. */
45 const char *_dl_platform
;
46 size_t _dl_platformlen
;
50 ElfW(Addr
) _dl_use_load_bias
= -2;
53 /* If nonzero print warnings about problematic situations. */
56 /* We never do profiling. */
57 const char *_dl_profile
;
58 const char *_dl_profile_output
;
60 /* Names of shared object for which the RUNPATHs and RPATHs should be
62 const char *_dl_inhibit_rpath
;
64 /* The map for the object we will profile. */
65 struct link_map
*_dl_profile_map
;
67 /* This is the address of the last stack address ever used. */
68 void *__libc_stack_end
;
70 /* Path where the binary is found. */
71 const char *_dl_origin_path
;
73 /* Nonzero if runtime lookup should not update the .got/.plt. */
76 /* A dummy link map for the executable, used by dlopen to access the global
77 scope. We don't export any symbols ourselves, so this can be minimal. */
78 static struct link_map _dl_main_map
=
80 .l_name
= (char *) "",
81 .l_real
= &_dl_main_map
,
83 .l_libname
= &(struct libname_list
) { .name
= "", .dont_free
= 1 },
86 .r_list
= &(struct link_map
*) { &_dl_main_map
},
89 .l_symbolic_searchlist
= { .r_list
= &(struct link_map
*) { NULL
} },
90 .l_type
= lt_executable
,
91 .l_scope_mem
= { &_dl_main_map
.l_searchlist
},
92 .l_scope_max
= (sizeof (_dl_main_map
.l_scope_mem
)
93 / sizeof (_dl_main_map
.l_scope_mem
[0])),
94 .l_scope
= _dl_main_map
.l_scope_mem
,
95 .l_local_scope
= { &_dl_main_map
.l_searchlist
},
97 .l_tls_offset
= NO_TLS_OFFSET
,
101 /* Namespace information. */
102 struct link_namespaces _dl_ns
[DL_NNS
] =
106 ._ns_loaded
= &_dl_main_map
,
108 ._ns_main_searchlist
= &_dl_main_map
.l_searchlist
,
113 /* Incremented whenever something may have been added to dl_loaded. */
114 unsigned long long _dl_load_adds
= 1;
116 /* Fake scope of the main application. */
117 struct r_scope_elem _dl_initial_searchlist
=
119 .r_list
= &(struct link_map
*) { &_dl_main_map
},
123 #ifndef HAVE_INLINED_SYSCALLS
124 /* Nonzero during startup. */
125 int _dl_starting_up
= 1;
128 /* Random data provided by the kernel. */
131 /* Get architecture specific initializer. */
132 #include <dl-procruntime.c>
133 #include <dl-procinfo.c>
135 void (*_dl_init_static_tls
) (struct link_map
*) = &_dl_nothread_init_static_tls
;
137 size_t _dl_pagesize
= EXEC_PAGESIZE
;
139 int _dl_inhibit_cache
;
141 unsigned int _dl_osversion
;
143 /* All known directories in sorted order. */
144 struct r_search_path_elem
*_dl_all_dirs
;
146 /* All directories after startup. */
147 struct r_search_path_elem
*_dl_init_all_dirs
;
149 /* The object to be initialized first. */
150 struct link_map
*_dl_initfirst
;
152 /* Descriptor to write debug messages to. */
153 int _dl_debug_fd
= STDERR_FILENO
;
155 int _dl_correct_cache_id
= _DL_CACHE_DEFAULT_ID
;
157 ElfW(auxv_t
) *_dl_auxv
;
158 const ElfW(Phdr
) *_dl_phdr
;
160 uint64_t _dl_hwcap
__attribute__ ((nocommon
));
161 uint64_t _dl_hwcap2
__attribute__ ((nocommon
));
163 /* The value of the FPU control word the kernel will preset in hardware. */
164 fpu_control_t _dl_fpu_control
= _FPU_DEFAULT
;
167 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
168 of _dl_important_hwcaps, below, where no hwcap strings are ever
169 used. This mask is still used to mediate the lookups in the cache
170 file. Since there is no way to set this nonzero (we don't grok the
171 LD_HWCAP_MASK environment variable here), there is no real point in
172 setting _dl_hwcap nonzero below, but we do anyway. */
173 uint64_t _dl_hwcap_mask
__attribute__ ((nocommon
));
176 /* Prevailing state of the stack. Generally this includes PF_X, indicating it's
177 * executable but this isn't true for all platforms. */
178 ElfW(Word
) _dl_stack_flags
= DEFAULT_STACK_PERMS
;
180 /* If loading a shared object requires that we make the stack executable
181 when it was not, we do it by calling this function.
182 It returns an errno code or zero on success. */
183 int (*_dl_make_stack_executable_hook
) (void **) = _dl_make_stack_executable
;
186 /* Function in libpthread to wait for termination of lookups. */
187 void (*_dl_wait_lookup_done
) (void);
189 #if !THREAD_GSCOPE_IN_TCB
190 int _dl_thread_gscope_count
;
192 struct dl_scope_free_list
*_dl_scope_free_list
;
194 #ifdef NEED_DL_SYSINFO
195 /* Needed for improved syscall handling on at least x86/Linux. */
196 uintptr_t _dl_sysinfo
= DL_SYSINFO_DEFAULT
;
198 #ifdef NEED_DL_SYSINFO_DSO
199 /* Address of the ELF headers in the vsyscall page. */
200 const ElfW(Ehdr
) *_dl_sysinfo_dso
;
202 struct link_map
*_dl_sysinfo_map
;
204 # include "get-dynamic-info.h"
206 #include "setup-vdso.h"
207 /* Define the vDSO function pointers. */
208 #include <dl-vdso-setup.c>
210 /* During the program run we must not modify the global data of
211 loaded shared object simultanously in two threads. Therefore we
212 protect `_dl_open' and `_dl_close' in dl-close.c.
214 This must be a recursive lock since the initializer function of
215 the loaded object might as well require a call to this function.
216 At this time it is not anymore a problem to modify the tables. */
217 __rtld_lock_define_initialized_recursive (, _dl_load_lock
)
218 /* This lock is used to keep __dl_iterate_phdr from inspecting the
219 list of loaded objects while an object is added to or removed from
221 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock
)
224 #ifdef HAVE_AUX_VECTOR
228 _dl_aux_init (ElfW(auxv_t
) *av
)
235 for (; av
->a_type
!= AT_NULL
; ++av
)
239 if (av
->a_un
.a_val
!= 0)
240 GLRO(dl_pagesize
) = av
->a_un
.a_val
;
243 GLRO(dl_clktck
) = av
->a_un
.a_val
;
246 GL(dl_phdr
) = (const void *) av
->a_un
.a_val
;
249 GL(dl_phnum
) = av
->a_un
.a_val
;
252 GLRO(dl_platform
) = (void *) av
->a_un
.a_val
;
255 GLRO(dl_hwcap
) = (unsigned long int) av
->a_un
.a_val
;
258 GLRO(dl_hwcap2
) = (unsigned long int) av
->a_un
.a_val
;
261 GLRO(dl_fpu_control
) = av
->a_un
.a_val
;
263 #ifdef NEED_DL_SYSINFO
265 GL(dl_sysinfo
) = av
->a_un
.a_val
;
268 #ifdef NEED_DL_SYSINFO_DSO
269 case AT_SYSINFO_EHDR
:
270 GL(dl_sysinfo_dso
) = (void *) av
->a_un
.a_val
;
274 uid
^= av
->a_un
.a_val
;
278 uid
^= av
->a_un
.a_val
;
282 gid
^= av
->a_un
.a_val
;
286 gid
^= av
->a_un
.a_val
;
291 __libc_enable_secure
= av
->a_un
.a_val
;
292 __libc_enable_secure_decided
= 1;
295 _dl_random
= (void *) av
->a_un
.a_val
;
301 __libc_enable_secure
= uid
!= 0 || gid
!= 0;
302 __libc_enable_secure_decided
= 1;
309 _dl_non_dynamic_init (void)
311 _dl_main_map
.l_origin
= _dl_get_origin ();
312 _dl_main_map
.l_phdr
= GL(dl_phdr
);
313 _dl_main_map
.l_phnum
= GL(dl_phnum
);
315 _dl_verbose
= *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
317 /* Set up the data structures for the system-supplied DSO early,
318 so they can influence _dl_init_paths. */
319 setup_vdso (NULL
, NULL
);
321 /* With vDSO setup we can initialize the function pointers. */
322 setup_vdso_pointers ();
324 /* Initialize the data structures for the search paths for shared
326 _dl_init_paths (getenv ("LD_LIBRARY_PATH"));
328 /* Remember the last search directory added at startup. */
329 _dl_init_all_dirs
= GL(dl_all_dirs
);
331 _dl_lazy
= *(getenv ("LD_BIND_NOW") ?: "") == '\0';
333 _dl_bind_not
= *(getenv ("LD_BIND_NOT") ?: "") != '\0';
335 _dl_dynamic_weak
= *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
337 _dl_profile_output
= getenv ("LD_PROFILE_OUTPUT");
338 if (_dl_profile_output
== NULL
|| _dl_profile_output
[0] == '\0')
340 = &"/var/tmp\0/var/profile"[__libc_enable_secure
? 9 : 0];
342 if (__libc_enable_secure
)
344 static const char unsecure_envvars
[] =
346 #ifdef EXTRA_UNSECURE_ENVVARS
347 EXTRA_UNSECURE_ENVVARS
350 const char *cp
= unsecure_envvars
;
352 while (cp
< unsecure_envvars
+ sizeof (unsecure_envvars
))
355 cp
= (const char *) __rawmemchr (cp
, '\0') + 1;
359 if (__access ("/etc/suid-debug", F_OK
) != 0)
360 __unsetenv ("MALLOC_CHECK_");
364 #ifdef DL_PLATFORM_INIT
368 #ifdef DL_OSVERSION_INIT
372 /* Now determine the length of the platform string. */
373 if (_dl_platform
!= NULL
)
374 _dl_platformlen
= strlen (_dl_platform
);
376 if (_dl_phdr
!= NULL
)
377 for (const ElfW(Phdr
) *ph
= _dl_phdr
; ph
< &_dl_phdr
[_dl_phnum
]; ++ph
)
380 /* Check if the stack is nonexecutable. */
382 _dl_stack_flags
= ph
->p_flags
;
386 _dl_main_map
.l_relro_addr
= ph
->p_vaddr
;
387 _dl_main_map
.l_relro_size
= ph
->p_memsz
;
391 /* Setup relro on the binary itself. */
392 if (_dl_main_map
.l_relro_size
!= 0)
393 _dl_protect_relro (&_dl_main_map
);
396 #ifdef DL_SYSINFO_IMPLEMENTATION
397 DL_SYSINFO_IMPLEMENTATION
400 #if ENABLE_STATIC_PIE
401 /* Since relocation to hidden _dl_main_map causes relocation overflow on
402 aarch64, a function is used to get the address of _dl_main_map. */
405 _dl_get_dl_main_map (void)
407 return &_dl_main_map
;