1 /* Support for dynamic linking code in static libc.
2 Copyright (C) 1996-2021 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. */
23 /* Mark symbols hidden in static PIE for early self relocation to work.
24 Note: string.h may have ifuncs which cannot be hidden on i686. */
26 # pragma GCC visibility push(hidden)
32 #include <sys/param.h>
35 #include <dl-machine.h>
36 #include <libc-lock.h>
38 #include <dl-librecon.h>
39 #include <dl-procinfo.h>
40 #include <unsecvars.h>
41 #include <hp-timing.h>
42 #include <stackinfo.h>
44 #include <dl-vdso-setup.h>
47 extern char *__progname
;
48 char **_dl_argv
= &__progname
; /* This is checked for some error messages. */
50 /* Name of the architecture. */
51 const char *_dl_platform
;
52 size_t _dl_platformlen
;
56 ElfW(Addr
) _dl_use_load_bias
= -2;
59 /* If nonzero print warnings about problematic situations. */
62 /* We never do profiling. */
63 const char *_dl_profile
;
64 const char *_dl_profile_output
;
66 /* Names of shared object for which the RUNPATHs and RPATHs should be
68 const char *_dl_inhibit_rpath
;
70 /* The map for the object we will profile. */
71 struct link_map
*_dl_profile_map
;
73 /* This is the address of the last stack address ever used. */
74 void *__libc_stack_end
;
76 /* Path where the binary is found. */
77 const char *_dl_origin_path
;
79 /* Nonzero if runtime lookup should not update the .got/.plt. */
82 /* A dummy link map for the executable, used by dlopen to access the global
83 scope. We don't export any symbols ourselves, so this can be minimal. */
84 static struct link_map _dl_main_map
=
86 .l_name
= (char *) "",
87 .l_real
= &_dl_main_map
,
89 .l_libname
= &(struct libname_list
) { .name
= "", .dont_free
= 1 },
92 .r_list
= &(struct link_map
*) { &_dl_main_map
},
95 .l_symbolic_searchlist
= { .r_list
= &(struct link_map
*) { NULL
} },
96 .l_type
= lt_executable
,
97 .l_scope_mem
= { &_dl_main_map
.l_searchlist
},
98 .l_scope_max
= (sizeof (_dl_main_map
.l_scope_mem
)
99 / sizeof (_dl_main_map
.l_scope_mem
[0])),
100 .l_scope
= _dl_main_map
.l_scope_mem
,
101 .l_local_scope
= { &_dl_main_map
.l_searchlist
},
103 .l_tls_offset
= NO_TLS_OFFSET
,
107 /* Namespace information. */
108 struct link_namespaces _dl_ns
[DL_NNS
] =
112 ._ns_loaded
= &_dl_main_map
,
114 ._ns_main_searchlist
= &_dl_main_map
.l_searchlist
,
119 /* Incremented whenever something may have been added to dl_loaded. */
120 unsigned long long _dl_load_adds
= 1;
122 /* Fake scope of the main application. */
123 struct r_scope_elem _dl_initial_searchlist
=
125 .r_list
= &(struct link_map
*) { &_dl_main_map
},
129 #ifndef HAVE_INLINED_SYSCALLS
130 /* Nonzero during startup. */
131 int _dl_starting_up
= 1;
134 /* Random data provided by the kernel. */
137 /* Get architecture specific initializer. */
138 #include <dl-procruntime.c>
139 #include <dl-procinfo.c>
141 void (*_dl_init_static_tls
) (struct link_map
*) = &_dl_nothread_init_static_tls
;
143 size_t _dl_pagesize
= EXEC_PAGESIZE
;
145 int _dl_inhibit_cache
;
147 unsigned int _dl_osversion
;
149 /* All known directories in sorted order. */
150 struct r_search_path_elem
*_dl_all_dirs
;
152 /* All directories after startup. */
153 struct r_search_path_elem
*_dl_init_all_dirs
;
155 /* The object to be initialized first. */
156 struct link_map
*_dl_initfirst
;
158 /* Descriptor to write debug messages to. */
159 int _dl_debug_fd
= STDERR_FILENO
;
161 int _dl_correct_cache_id
= _DL_CACHE_DEFAULT_ID
;
163 ElfW(auxv_t
) *_dl_auxv
;
164 const ElfW(Phdr
) *_dl_phdr
;
166 uint64_t _dl_hwcap
__attribute__ ((nocommon
));
167 uint64_t _dl_hwcap2
__attribute__ ((nocommon
));
169 /* The value of the FPU control word the kernel will preset in hardware. */
170 fpu_control_t _dl_fpu_control
= _FPU_DEFAULT
;
173 /* This is not initialized to HWCAP_IMPORTANT, matching the definition
174 of _dl_important_hwcaps, below, where no hwcap strings are ever
175 used. This mask is still used to mediate the lookups in the cache
176 file. Since there is no way to set this nonzero (we don't grok the
177 LD_HWCAP_MASK environment variable here), there is no real point in
178 setting _dl_hwcap nonzero below, but we do anyway. */
179 uint64_t _dl_hwcap_mask
__attribute__ ((nocommon
));
182 /* Prevailing state of the stack. Generally this includes PF_X, indicating it's
183 * executable but this isn't true for all platforms. */
184 ElfW(Word
) _dl_stack_flags
= DEFAULT_STACK_PERMS
;
186 /* If loading a shared object requires that we make the stack executable
187 when it was not, we do it by calling this function.
188 It returns an errno code or zero on success. */
189 int (*_dl_make_stack_executable_hook
) (void **) = _dl_make_stack_executable
;
192 #if THREAD_GSCOPE_IN_TCB
193 list_t _dl_stack_used
;
194 list_t _dl_stack_user
;
195 int _dl_stack_cache_lock
;
197 int _dl_thread_gscope_count
;
199 struct dl_scope_free_list
*_dl_scope_free_list
;
201 #ifdef NEED_DL_SYSINFO
202 /* Needed for improved syscall handling on at least x86/Linux. NB: Don't
203 initialize it here to avoid RELATIVE relocation in static PIE. */
204 uintptr_t _dl_sysinfo
;
206 #ifdef NEED_DL_SYSINFO_DSO
207 /* Address of the ELF headers in the vsyscall page. */
208 const ElfW(Ehdr
) *_dl_sysinfo_dso
;
210 struct link_map
*_dl_sysinfo_map
;
212 # include "get-dynamic-info.h"
214 #include "setup-vdso.h"
215 /* Define the vDSO function pointers. */
216 #include <dl-vdso-setup.c>
218 /* During the program run we must not modify the global data of
219 loaded shared object simultanously in two threads. Therefore we
220 protect `_dl_open' and `_dl_close' in dl-close.c.
222 This must be a recursive lock since the initializer function of
223 the loaded object might as well require a call to this function.
224 At this time it is not anymore a problem to modify the tables. */
225 __rtld_lock_define_initialized_recursive (, _dl_load_lock
)
226 /* This lock is used to keep __dl_iterate_phdr from inspecting the
227 list of loaded objects while an object is added to or removed from
229 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock
)
232 #ifdef HAVE_AUX_VECTOR
236 _dl_aux_init (ElfW(auxv_t
) *av
)
242 #ifdef NEED_DL_SYSINFO
243 /* NB: Avoid RELATIVE relocation in static PIE. */
244 GL(dl_sysinfo
) = DL_SYSINFO_DEFAULT
;
248 for (; av
->a_type
!= AT_NULL
; ++av
)
252 if (av
->a_un
.a_val
!= 0)
253 GLRO(dl_pagesize
) = av
->a_un
.a_val
;
256 GLRO(dl_clktck
) = av
->a_un
.a_val
;
259 GL(dl_phdr
) = (const void *) av
->a_un
.a_val
;
262 GL(dl_phnum
) = av
->a_un
.a_val
;
265 GLRO(dl_platform
) = (void *) av
->a_un
.a_val
;
268 GLRO(dl_hwcap
) = (unsigned long int) av
->a_un
.a_val
;
271 GLRO(dl_hwcap2
) = (unsigned long int) av
->a_un
.a_val
;
274 GLRO(dl_fpu_control
) = av
->a_un
.a_val
;
276 #ifdef NEED_DL_SYSINFO
278 GL(dl_sysinfo
) = av
->a_un
.a_val
;
281 #ifdef NEED_DL_SYSINFO_DSO
282 case AT_SYSINFO_EHDR
:
283 GL(dl_sysinfo_dso
) = (void *) av
->a_un
.a_val
;
287 uid
^= av
->a_un
.a_val
;
291 uid
^= av
->a_un
.a_val
;
295 gid
^= av
->a_un
.a_val
;
299 gid
^= av
->a_un
.a_val
;
304 __libc_enable_secure
= av
->a_un
.a_val
;
305 __libc_enable_secure_decided
= 1;
308 _dl_random
= (void *) av
->a_un
.a_val
;
314 __libc_enable_secure
= uid
!= 0 || gid
!= 0;
315 __libc_enable_secure_decided
= 1;
322 _dl_non_dynamic_init (void)
324 _dl_main_map
.l_origin
= _dl_get_origin ();
325 _dl_main_map
.l_phdr
= GL(dl_phdr
);
326 _dl_main_map
.l_phnum
= GL(dl_phnum
);
328 _dl_verbose
= *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
330 /* Set up the data structures for the system-supplied DSO early,
331 so they can influence _dl_init_paths. */
332 setup_vdso (NULL
, NULL
);
334 /* With vDSO setup we can initialize the function pointers. */
335 setup_vdso_pointers ();
337 /* Initialize the data structures for the search paths for shared
339 _dl_init_paths (getenv ("LD_LIBRARY_PATH"), "LD_LIBRARY_PATH",
340 /* No glibc-hwcaps selection support in statically
344 /* Remember the last search directory added at startup. */
345 _dl_init_all_dirs
= GL(dl_all_dirs
);
347 _dl_lazy
= *(getenv ("LD_BIND_NOW") ?: "") == '\0';
349 _dl_bind_not
= *(getenv ("LD_BIND_NOT") ?: "") != '\0';
351 _dl_dynamic_weak
= *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
353 _dl_profile_output
= getenv ("LD_PROFILE_OUTPUT");
354 if (_dl_profile_output
== NULL
|| _dl_profile_output
[0] == '\0')
356 = &"/var/tmp\0/var/profile"[__libc_enable_secure
? 9 : 0];
358 if (__libc_enable_secure
)
360 static const char unsecure_envvars
[] =
362 #ifdef EXTRA_UNSECURE_ENVVARS
363 EXTRA_UNSECURE_ENVVARS
366 const char *cp
= unsecure_envvars
;
368 while (cp
< unsecure_envvars
+ sizeof (unsecure_envvars
))
371 cp
= (const char *) __rawmemchr (cp
, '\0') + 1;
375 if (__access ("/etc/suid-debug", F_OK
) != 0)
376 __unsetenv ("MALLOC_CHECK_");
380 #ifdef DL_PLATFORM_INIT
384 #ifdef DL_OSVERSION_INIT
388 /* Now determine the length of the platform string. */
389 if (_dl_platform
!= NULL
)
390 _dl_platformlen
= strlen (_dl_platform
);
392 if (_dl_phdr
!= NULL
)
393 for (const ElfW(Phdr
) *ph
= _dl_phdr
; ph
< &_dl_phdr
[_dl_phnum
]; ++ph
)
396 /* Check if the stack is nonexecutable. */
398 _dl_stack_flags
= ph
->p_flags
;
402 _dl_main_map
.l_relro_addr
= ph
->p_vaddr
;
403 _dl_main_map
.l_relro_size
= ph
->p_memsz
;
407 /* Setup relro on the binary itself. */
408 if (_dl_main_map
.l_relro_size
!= 0)
409 _dl_protect_relro (&_dl_main_map
);
412 #ifdef DL_SYSINFO_IMPLEMENTATION
413 DL_SYSINFO_IMPLEMENTATION
416 #if ENABLE_STATIC_PIE
417 /* Since relocation to hidden _dl_main_map causes relocation overflow on
418 aarch64, a function is used to get the address of _dl_main_map. */
421 _dl_get_dl_main_map (void)
423 return &_dl_main_map
;