1/* Support for dynamic linking code in static libc.
2 Copyright (C) 1996-2022 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
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.
9
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.
14
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/>. */
18
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. */
21
22#include <string.h>
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. */
25#if BUILD_PIE_DEFAULT
26# pragma GCC visibility push(hidden)
27#endif
28#include <errno.h>
29#include <libintl.h>
30#include <stdlib.h>
31#include <unistd.h>
32#include <sys/param.h>
33#include <stdint.h>
34#include <ldsodefs.h>
35#include <dl-machine.h>
36#include <libc-lock.h>
37#include <dl-cache.h>
38#include <dl-procinfo.h>
39#include <unsecvars.h>
40#include <hp-timing.h>
41#include <stackinfo.h>
42#include <dl-vdso.h>
43#include <dl-vdso-setup.h>
44#include <dl-auxv.h>
45#include <dl-find_object.h>
46#include <array_length.h>
47
48extern char *__progname;
49char **_dl_argv = &__progname; /* This is checked for some error messages. */
50
51/* Name of the architecture. */
52const char *_dl_platform;
53size_t _dl_platformlen;
54
55int _dl_debug_mask;
56int _dl_lazy;
57int _dl_dynamic_weak;
58
59/* If nonzero print warnings about problematic situations. */
60int _dl_verbose;
61
62/* We never do profiling. */
63const char *_dl_profile;
64const char *_dl_profile_output;
65
66/* Names of shared object for which the RUNPATHs and RPATHs should be
67 ignored. */
68const char *_dl_inhibit_rpath;
69
70/* The map for the object we will profile. */
71struct link_map *_dl_profile_map;
72
73/* This is the address of the last stack address ever used. */
74void *__libc_stack_end;
75
76/* Path where the binary is found. */
77const char *_dl_origin_path;
78
79/* Nonzero if runtime lookup should not update the .got/.plt. */
80int _dl_bind_not;
81
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. */
84static struct link_map _dl_main_map =
85 {
86 .l_name = (char *) "",
87 .l_real = &_dl_main_map,
88 .l_ns = LM_ID_BASE,
89 .l_libname = &(struct libname_list) { .name = "", .dont_free = 1 },
90 .l_searchlist =
91 {
92 .r_list = &(struct link_map *) { &_dl_main_map },
93 .r_nlist = 1,
94 },
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 },
102 .l_used = 1,
103 .l_tls_offset = NO_TLS_OFFSET,
104 .l_serial = 1,
105 };
106
107/* Namespace information. */
108struct link_namespaces _dl_ns[DL_NNS] =
109 {
110 [LM_ID_BASE] =
111 {
112 ._ns_loaded = &_dl_main_map,
113 ._ns_nloaded = 1,
114 ._ns_main_searchlist = &_dl_main_map.l_searchlist,
115 }
116 };
117size_t _dl_nns = 1;
118
119/* Incremented whenever something may have been added to dl_loaded. */
120unsigned long long _dl_load_adds = 1;
121
122/* Fake scope of the main application. */
123struct r_scope_elem _dl_initial_searchlist =
124 {
125 .r_list = &(struct link_map *) { &_dl_main_map },
126 .r_nlist = 1,
127 };
128
129#ifndef HAVE_INLINED_SYSCALLS
130/* Nonzero during startup. */
131int _dl_starting_up = 1;
132#endif
133
134/* Random data provided by the kernel. */
135void *_dl_random;
136
137/* Get architecture specific initializer. */
138#include <dl-procruntime.c>
139#include <dl-procinfo.c>
140
141size_t _dl_pagesize = EXEC_PAGESIZE;
142
143size_t _dl_minsigstacksize = CONSTANT_MINSIGSTKSZ;
144
145int _dl_inhibit_cache;
146
147/* All known directories in sorted order. */
148struct r_search_path_elem *_dl_all_dirs;
149
150/* All directories after startup. */
151struct r_search_path_elem *_dl_init_all_dirs;
152
153/* The object to be initialized first. */
154struct link_map *_dl_initfirst;
155
156/* Descriptor to write debug messages to. */
157int _dl_debug_fd = STDERR_FILENO;
158
159ElfW(auxv_t) *_dl_auxv;
160const ElfW(Phdr) *_dl_phdr;
161size_t _dl_phnum;
162uint64_t _dl_hwcap;
163uint64_t _dl_hwcap2;
164
165enum dso_sort_algorithm _dl_dso_sort_algo;
166
167/* The value of the FPU control word the kernel will preset in hardware. */
168fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
169
170#if !HAVE_TUNABLES
171/* This is not initialized to HWCAP_IMPORTANT, matching the definition
172 of _dl_important_hwcaps, below, where no hwcap strings are ever
173 used. This mask is still used to mediate the lookups in the cache
174 file. Since there is no way to set this nonzero (we don't grok the
175 LD_HWCAP_MASK environment variable here), there is no real point in
176 setting _dl_hwcap nonzero below, but we do anyway. */
177uint64_t _dl_hwcap_mask;
178#endif
179
180/* Prevailing state of the stack. Generally this includes PF_X, indicating it's
181 * executable but this isn't true for all platforms. */
182ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
183
184#if PTHREAD_IN_LIBC
185list_t _dl_stack_used;
186list_t _dl_stack_user;
187list_t _dl_stack_cache;
188size_t _dl_stack_cache_actsize;
189uintptr_t _dl_in_flight_stack;
190int _dl_stack_cache_lock;
191#else
192/* If loading a shared object requires that we make the stack executable
193 when it was not, we do it by calling this function.
194 It returns an errno code or zero on success. */
195int (*_dl_make_stack_executable_hook) (void **) = _dl_make_stack_executable;
196void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
197#endif
198struct dl_scope_free_list *_dl_scope_free_list;
199
200#ifdef NEED_DL_SYSINFO
201/* Needed for improved syscall handling on at least x86/Linux. NB: Don't
202 initialize it here to avoid RELATIVE relocation in static PIE. */
203uintptr_t _dl_sysinfo;
204#endif
205#ifdef NEED_DL_SYSINFO_DSO
206/* Address of the ELF headers in the vsyscall page. */
207const ElfW(Ehdr) *_dl_sysinfo_dso;
208
209struct link_map *_dl_sysinfo_map;
210
211# include "get-dynamic-info.h"
212#endif
213#include "setup-vdso.h"
214/* Define the vDSO function pointers. */
215#include <dl-vdso-setup.c>
216
217/* During the program run we must not modify the global data of
218 loaded shared object simultanously in two threads. Therefore we
219 protect `_dl_open' and `_dl_close' in dl-close.c.
220
221 This must be a recursive lock since the initializer function of
222 the loaded object might as well require a call to this function.
223 At this time it is not anymore a problem to modify the tables. */
224__rtld_lock_define_initialized_recursive (, _dl_load_lock)
225/* This lock is used to keep __dl_iterate_phdr from inspecting the
226 list of loaded objects while an object is added to or removed from
227 that list. */
228__rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
229 /* This lock protects global and module specific TLS related data.
230 E.g. it is held in dlopen and dlclose when GL(dl_tls_generation),
231 GL(dl_tls_max_dtv_idx) or GL(dl_tls_dtv_slotinfo_list) are
232 accessed and when TLS related relocations are processed for a
233 module. It was introduced to keep pthread_create accessing TLS
234 state that is being set up. */
235__rtld_lock_define_initialized_recursive (, _dl_load_tls_lock)
236
237
238#ifdef HAVE_AUX_VECTOR
239#include <dl-parse_auxv.h>
240
241int _dl_clktck;
242
243void
244_dl_aux_init (ElfW(auxv_t) *av)
245{
246#ifdef NEED_DL_SYSINFO
247 /* NB: Avoid RELATIVE relocation in static PIE. */
248 GL(dl_sysinfo) = DL_SYSINFO_DEFAULT;
249#endif
250
251 _dl_auxv = av;
252 dl_parse_auxv_t auxv_values;
253 /* Use an explicit initialization loop here because memset may not
254 be available yet. */
255 for (int i = 0; i < array_length (auxv_values); ++i)
256 auxv_values[i] = 0;
257 _dl_parse_auxv (av, auxv_values);
258}
259#endif
260
261
262void
263_dl_non_dynamic_init (void)
264{
265 _dl_main_map.l_origin = _dl_get_origin ();
266 _dl_main_map.l_phdr = GL(dl_phdr);
267 _dl_main_map.l_phnum = GL(dl_phnum);
268
269 _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
270
271 /* Set up the data structures for the system-supplied DSO early,
272 so they can influence _dl_init_paths. */
273 setup_vdso (NULL, NULL);
274
275 /* With vDSO setup we can initialize the function pointers. */
276 setup_vdso_pointers ();
277
278 /* Initialize the data structures for the search paths for shared
279 objects. */
280 _dl_init_paths (getenv ("LD_LIBRARY_PATH"), "LD_LIBRARY_PATH",
281 /* No glibc-hwcaps selection support in statically
282 linked binaries. */
283 NULL, NULL);
284
285 /* Remember the last search directory added at startup. */
286 _dl_init_all_dirs = GL(dl_all_dirs);
287
288 _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
289
290 _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
291
292 _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
293
294 _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
295 if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
296 _dl_profile_output
297 = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
298
299 if (__libc_enable_secure)
300 {
301 static const char unsecure_envvars[] =
302 UNSECURE_ENVVARS
303 ;
304 const char *cp = unsecure_envvars;
305
306 while (cp < unsecure_envvars + sizeof (unsecure_envvars))
307 {
308 __unsetenv (cp);
309 cp = (const char *) __rawmemchr (cp, '\0') + 1;
310 }
311
312#if !HAVE_TUNABLES
313 if (__access ("/etc/suid-debug", F_OK) != 0)
314 __unsetenv ("MALLOC_CHECK_");
315#endif
316 }
317
318#ifdef DL_PLATFORM_INIT
319 DL_PLATFORM_INIT;
320#endif
321
322 /* Now determine the length of the platform string. */
323 if (_dl_platform != NULL)
324 _dl_platformlen = strlen (_dl_platform);
325
326 if (_dl_phdr != NULL)
327 for (const ElfW(Phdr) *ph = _dl_phdr; ph < &_dl_phdr[_dl_phnum]; ++ph)
328 switch (ph->p_type)
329 {
330 /* Check if the stack is nonexecutable. */
331 case PT_GNU_STACK:
332 _dl_stack_flags = ph->p_flags;
333 break;
334
335 case PT_GNU_RELRO:
336 _dl_main_map.l_relro_addr = ph->p_vaddr;
337 _dl_main_map.l_relro_size = ph->p_memsz;
338 break;
339 }
340
341 call_function_static_weak (_dl_find_object_init);
342
343 /* Setup relro on the binary itself. */
344 if (_dl_main_map.l_relro_size != 0)
345 _dl_protect_relro (&_dl_main_map);
346}
347
348#ifdef DL_SYSINFO_IMPLEMENTATION
349DL_SYSINFO_IMPLEMENTATION
350#endif
351
352#if ENABLE_STATIC_PIE
353/* Since relocation to hidden _dl_main_map causes relocation overflow on
354 aarch64, a function is used to get the address of _dl_main_map. */
355
356struct link_map *
357_dl_get_dl_main_map (void)
358{
359 return &_dl_main_map;
360}
361#endif
362
363/* This is used by _dl_runtime_profile, not used on static code. */
364void
365DL_ARCH_FIXUP_ATTRIBUTE
366_dl_audit_pltexit (struct link_map *l, ElfW(Word) reloc_arg,
367 const void *inregs, void *outregs)
368{
369}
370