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.
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-librecon.h>
39#include <dl-procinfo.h>
40#include <unsecvars.h>
41#include <hp-timing.h>
42#include <stackinfo.h>
43#include <dl-vdso.h>
44#include <dl-vdso-setup.h>
45#include <dl-auxv.h>
46
47extern char *__progname;
48char **_dl_argv = &__progname; /* This is checked for some error messages. */
49
50/* Name of the architecture. */
51const char *_dl_platform;
52size_t _dl_platformlen;
53
54int _dl_debug_mask;
55int _dl_lazy;
56ElfW(Addr) _dl_use_load_bias = -2;
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
147unsigned int _dl_osversion;
148
149/* All known directories in sorted order. */
150struct r_search_path_elem *_dl_all_dirs;
151
152/* All directories after startup. */
153struct r_search_path_elem *_dl_init_all_dirs;
154
155/* The object to be initialized first. */
156struct link_map *_dl_initfirst;
157
158/* Descriptor to write debug messages to. */
159int _dl_debug_fd = STDERR_FILENO;
160
161int _dl_correct_cache_id = _DL_CACHE_DEFAULT_ID;
162
163ElfW(auxv_t) *_dl_auxv;
164const ElfW(Phdr) *_dl_phdr;
165size_t _dl_phnum;
166uint64_t _dl_hwcap;
167uint64_t _dl_hwcap2;
168
169/* The value of the FPU control word the kernel will preset in hardware. */
170fpu_control_t _dl_fpu_control = _FPU_DEFAULT;
171
172#if !HAVE_TUNABLES
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. */
179uint64_t _dl_hwcap_mask;
180#endif
181
182/* Prevailing state of the stack. Generally this includes PF_X, indicating it's
183 * executable but this isn't true for all platforms. */
184ElfW(Word) _dl_stack_flags = DEFAULT_STACK_PERMS;
185
186#if THREAD_GSCOPE_IN_TCB
187list_t _dl_stack_used;
188list_t _dl_stack_user;
189list_t _dl_stack_cache;
190size_t _dl_stack_cache_actsize;
191uintptr_t _dl_in_flight_stack;
192int _dl_stack_cache_lock;
193#else
194/* If loading a shared object requires that we make the stack executable
195 when it was not, we do it by calling this function.
196 It returns an errno code or zero on success. */
197int (*_dl_make_stack_executable_hook) (void **) = _dl_make_stack_executable;
198int _dl_thread_gscope_count;
199void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
200#endif
201struct dl_scope_free_list *_dl_scope_free_list;
202
203#ifdef NEED_DL_SYSINFO
204/* Needed for improved syscall handling on at least x86/Linux. NB: Don't
205 initialize it here to avoid RELATIVE relocation in static PIE. */
206uintptr_t _dl_sysinfo;
207#endif
208#ifdef NEED_DL_SYSINFO_DSO
209/* Address of the ELF headers in the vsyscall page. */
210const ElfW(Ehdr) *_dl_sysinfo_dso;
211
212struct link_map *_dl_sysinfo_map;
213
214# include "get-dynamic-info.h"
215#endif
216#include "setup-vdso.h"
217/* Define the vDSO function pointers. */
218#include <dl-vdso-setup.c>
219
220/* During the program run we must not modify the global data of
221 loaded shared object simultanously in two threads. Therefore we
222 protect `_dl_open' and `_dl_close' in dl-close.c.
223
224 This must be a recursive lock since the initializer function of
225 the loaded object might as well require a call to this function.
226 At this time it is not anymore a problem to modify the tables. */
227__rtld_lock_define_initialized_recursive (, _dl_load_lock)
228/* This lock is used to keep __dl_iterate_phdr from inspecting the
229 list of loaded objects while an object is added to or removed from
230 that list. */
231__rtld_lock_define_initialized_recursive (, _dl_load_write_lock)
232
233
234#ifdef HAVE_AUX_VECTOR
235int _dl_clktck;
236
237void
238_dl_aux_init (ElfW(auxv_t) *av)
239{
240 int seen = 0;
241 uid_t uid = 0;
242 gid_t gid = 0;
243
244#ifdef NEED_DL_SYSINFO
245 /* NB: Avoid RELATIVE relocation in static PIE. */
246 GL(dl_sysinfo) = DL_SYSINFO_DEFAULT;
247#endif
248
249 _dl_auxv = av;
250 for (; av->a_type != AT_NULL; ++av)
251 switch (av->a_type)
252 {
253 case AT_PAGESZ:
254 if (av->a_un.a_val != 0)
255 GLRO(dl_pagesize) = av->a_un.a_val;
256 break;
257 case AT_CLKTCK:
258 GLRO(dl_clktck) = av->a_un.a_val;
259 break;
260 case AT_PHDR:
261 GL(dl_phdr) = (const void *) av->a_un.a_val;
262 break;
263 case AT_PHNUM:
264 GL(dl_phnum) = av->a_un.a_val;
265 break;
266 case AT_PLATFORM:
267 GLRO(dl_platform) = (void *) av->a_un.a_val;
268 break;
269 case AT_HWCAP:
270 GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
271 break;
272 case AT_HWCAP2:
273 GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
274 break;
275 case AT_FPUCW:
276 GLRO(dl_fpu_control) = av->a_un.a_val;
277 break;
278#ifdef NEED_DL_SYSINFO
279 case AT_SYSINFO:
280 GL(dl_sysinfo) = av->a_un.a_val;
281 break;
282#endif
283#ifdef NEED_DL_SYSINFO_DSO
284 case AT_SYSINFO_EHDR:
285 GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
286 break;
287#endif
288 case AT_UID:
289 uid ^= av->a_un.a_val;
290 seen |= 1;
291 break;
292 case AT_EUID:
293 uid ^= av->a_un.a_val;
294 seen |= 2;
295 break;
296 case AT_GID:
297 gid ^= av->a_un.a_val;
298 seen |= 4;
299 break;
300 case AT_EGID:
301 gid ^= av->a_un.a_val;
302 seen |= 8;
303 break;
304 case AT_SECURE:
305 seen = -1;
306 __libc_enable_secure = av->a_un.a_val;
307 __libc_enable_secure_decided = 1;
308 break;
309 case AT_RANDOM:
310 _dl_random = (void *) av->a_un.a_val;
311 break;
312 case AT_MINSIGSTKSZ:
313 _dl_minsigstacksize = av->a_un.a_val;
314 break;
315 DL_PLATFORM_AUXV
316 }
317 if (seen == 0xf)
318 {
319 __libc_enable_secure = uid != 0 || gid != 0;
320 __libc_enable_secure_decided = 1;
321 }
322}
323#endif
324
325
326void
327_dl_non_dynamic_init (void)
328{
329 _dl_main_map.l_origin = _dl_get_origin ();
330 _dl_main_map.l_phdr = GL(dl_phdr);
331 _dl_main_map.l_phnum = GL(dl_phnum);
332
333 _dl_verbose = *(getenv ("LD_WARN") ?: "") == '\0' ? 0 : 1;
334
335 /* Set up the data structures for the system-supplied DSO early,
336 so they can influence _dl_init_paths. */
337 setup_vdso (NULL, NULL);
338
339 /* With vDSO setup we can initialize the function pointers. */
340 setup_vdso_pointers ();
341
342 /* Initialize the data structures for the search paths for shared
343 objects. */
344 _dl_init_paths (getenv ("LD_LIBRARY_PATH"), "LD_LIBRARY_PATH",
345 /* No glibc-hwcaps selection support in statically
346 linked binaries. */
347 NULL, NULL);
348
349 /* Remember the last search directory added at startup. */
350 _dl_init_all_dirs = GL(dl_all_dirs);
351
352 _dl_lazy = *(getenv ("LD_BIND_NOW") ?: "") == '\0';
353
354 _dl_bind_not = *(getenv ("LD_BIND_NOT") ?: "") != '\0';
355
356 _dl_dynamic_weak = *(getenv ("LD_DYNAMIC_WEAK") ?: "") == '\0';
357
358 _dl_profile_output = getenv ("LD_PROFILE_OUTPUT");
359 if (_dl_profile_output == NULL || _dl_profile_output[0] == '\0')
360 _dl_profile_output
361 = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
362
363 if (__libc_enable_secure)
364 {
365 static const char unsecure_envvars[] =
366 UNSECURE_ENVVARS
367#ifdef EXTRA_UNSECURE_ENVVARS
368 EXTRA_UNSECURE_ENVVARS
369#endif
370 ;
371 const char *cp = unsecure_envvars;
372
373 while (cp < unsecure_envvars + sizeof (unsecure_envvars))
374 {
375 __unsetenv (cp);
376 cp = (const char *) __rawmemchr (cp, '\0') + 1;
377 }
378
379#if !HAVE_TUNABLES
380 if (__access ("/etc/suid-debug", F_OK) != 0)
381 __unsetenv ("MALLOC_CHECK_");
382#endif
383 }
384
385#ifdef DL_PLATFORM_INIT
386 DL_PLATFORM_INIT;
387#endif
388
389#ifdef DL_OSVERSION_INIT
390 DL_OSVERSION_INIT;
391#endif
392
393 /* Now determine the length of the platform string. */
394 if (_dl_platform != NULL)
395 _dl_platformlen = strlen (_dl_platform);
396
397 if (_dl_phdr != NULL)
398 for (const ElfW(Phdr) *ph = _dl_phdr; ph < &_dl_phdr[_dl_phnum]; ++ph)
399 switch (ph->p_type)
400 {
401 /* Check if the stack is nonexecutable. */
402 case PT_GNU_STACK:
403 _dl_stack_flags = ph->p_flags;
404 break;
405
406 case PT_GNU_RELRO:
407 _dl_main_map.l_relro_addr = ph->p_vaddr;
408 _dl_main_map.l_relro_size = ph->p_memsz;
409 break;
410 }
411
412 /* Setup relro on the binary itself. */
413 if (_dl_main_map.l_relro_size != 0)
414 _dl_protect_relro (&_dl_main_map);
415}
416
417#ifdef DL_SYSINFO_IMPLEMENTATION
418DL_SYSINFO_IMPLEMENTATION
419#endif
420
421#if ENABLE_STATIC_PIE
422/* Since relocation to hidden _dl_main_map causes relocation overflow on
423 aarch64, a function is used to get the address of _dl_main_map. */
424
425struct link_map *
426_dl_get_dl_main_map (void)
427{
428 return &_dl_main_map;
429}
430#endif
431