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 #if THREAD_GSCOPE_IN_TCB
187 list_t _dl_stack_used
;
188 list_t _dl_stack_user
;
189 int _dl_stack_cache_lock
;
191 int _dl_thread_gscope_count
;
193 struct dl_scope_free_list
*_dl_scope_free_list
;
195 #ifdef NEED_DL_SYSINFO
196 /* Needed for improved syscall handling on at least x86/Linux. */
197 uintptr_t _dl_sysinfo
= DL_SYSINFO_DEFAULT
;
199 #ifdef NEED_DL_SYSINFO_DSO
200 /* Address of the ELF headers in the vsyscall page. */
201 const ElfW(Ehdr
) *_dl_sysinfo_dso
;
203 struct link_map
*_dl_sysinfo_map
;
205 # include "get-dynamic-info.h"
207 #include "setup-vdso.h"
208 /* Define the vDSO function pointers. */
209 #include <dl-vdso-setup.c>
211 /* During the program run we must not modify the global data of
212 loaded shared object simultanously in two threads. Therefore we
213 protect `_dl_open' and `_dl_close' in dl-close.c.
215 This must be a recursive lock since the initializer function of
216 the loaded object might as well require a call to this function.
217 At this time it is not anymore a problem to modify the tables. */
218 __rtld_lock_define_initialized_recursive (, _dl_load_lock
)
219 /* This lock is used to keep __dl_iterate_phdr from inspecting the
220 list of loaded objects while an object is added to or removed from
222 __rtld_lock_define_initialized_recursive (, _dl_load_write_lock
)
225 #ifdef HAVE_AUX_VECTOR
229 _dl_aux_init (ElfW(auxv_t
) *av
)
236 for (; av
->a_type
!= AT_NULL
; ++av
)
240 if (av
->a_un
.a_val
!= 0)
241 GLRO(dl_pagesize
) = av
->a_un
.a_val
;
244 GLRO(dl_clktck
) = av
->a_un
.a_val
;
247 GL(dl_phdr
) = (const void *) av
->a_un
.a_val
;
250 GL(dl_phnum
) = av
->a_un
.a_val
;
253 GLRO(dl_platform
) = (void *) av
->a_un
.a_val
;
256 GLRO(dl_hwcap
) = (unsigned long int) av
->a_un
.a_val
;
259 GLRO(dl_hwcap2
) = (unsigned long int) av
->a_un
.a_val
;
262 GLRO(dl_fpu_control
) = av
->a_un
.a_val
;
264 #ifdef NEED_DL_SYSINFO
266 GL(dl_sysinfo
) = av
->a_un
.a_val
;
269 #ifdef NEED_DL_SYSINFO_DSO
270 case AT_SYSINFO_EHDR
:
271 GL(dl_sysinfo_dso
) = (void *) av
->a_un
.a_val
;
275 uid
^= av
->a_un
.a_val
;
279 uid
^= av
->a_un
.a_val
;
283 gid
^= av
->a_un
.a_val
;
287 gid
^= av
->a_un
.a_val
;
292 __libc_enable_secure
= av
->a_un
.a_val
;
293 __libc_enable_secure_decided
= 1;
296 _dl_random
= (void *) av
->a_un
.a_val
;
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"), "LD_LIBRARY_PATH",
328 /* No glibc-hwcaps selection support in statically
332 /* Remember the last search directory added at startup. */
333 _dl_init_all_dirs
= GL(dl_all_dirs
);
335 _dl_lazy
= *(getenv ("LD_BIND_NOW") ?: "") == '\0';
337 _dl_bind_not
= *(getenv ("LD_BIND_NOT") ?: "") != '\0';
339 _dl_dynamic_weak
= *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
341 _dl_profile_output
= getenv ("LD_PROFILE_OUTPUT");
342 if (_dl_profile_output
== NULL
|| _dl_profile_output
[0] == '\0')
344 = &"/var/tmp\0/var/profile"[__libc_enable_secure
? 9 : 0];
346 if (__libc_enable_secure
)
348 static const char unsecure_envvars
[] =
350 #ifdef EXTRA_UNSECURE_ENVVARS
351 EXTRA_UNSECURE_ENVVARS
354 const char *cp
= unsecure_envvars
;
356 while (cp
< unsecure_envvars
+ sizeof (unsecure_envvars
))
359 cp
= (const char *) __rawmemchr (cp
, '\0') + 1;
363 if (__access ("/etc/suid-debug", F_OK
) != 0)
364 __unsetenv ("MALLOC_CHECK_");
368 #ifdef DL_PLATFORM_INIT
372 #ifdef DL_OSVERSION_INIT
376 /* Now determine the length of the platform string. */
377 if (_dl_platform
!= NULL
)
378 _dl_platformlen
= strlen (_dl_platform
);
380 if (_dl_phdr
!= NULL
)
381 for (const ElfW(Phdr
) *ph
= _dl_phdr
; ph
< &_dl_phdr
[_dl_phnum
]; ++ph
)
384 /* Check if the stack is nonexecutable. */
386 _dl_stack_flags
= ph
->p_flags
;
390 _dl_main_map
.l_relro_addr
= ph
->p_vaddr
;
391 _dl_main_map
.l_relro_size
= ph
->p_memsz
;
395 /* Setup relro on the binary itself. */
396 if (_dl_main_map
.l_relro_size
!= 0)
397 _dl_protect_relro (&_dl_main_map
);
400 #ifdef DL_SYSINFO_IMPLEMENTATION
401 DL_SYSINFO_IMPLEMENTATION
404 #if ENABLE_STATIC_PIE
405 /* Since relocation to hidden _dl_main_map causes relocation overflow on
406 aarch64, a function is used to get the address of _dl_main_map. */
409 _dl_get_dl_main_map (void)
411 return &_dl_main_map
;