1/* Copyright (C) 1998-2020 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <assert.h>
19#include <stdlib.h>
20#include <stdio.h>
21#include <unistd.h>
22#include <ldsodefs.h>
23#include <exit-thread.h>
24#include <libc-internal.h>
25#include <elf/libc-early-init.h>
26#include <stdbool.h>
27
28#include <elf/dl-tunables.h>
29
30extern void __libc_init_first (int argc, char **argv, char **envp);
31
32#include <tls.h>
33#ifndef SHARED
34# include <dl-osinfo.h>
35# ifndef THREAD_SET_STACK_GUARD
36/* Only exported for architectures that don't store the stack guard canary
37 in thread local area. */
38uintptr_t __stack_chk_guard attribute_relro;
39# endif
40# ifndef THREAD_SET_POINTER_GUARD
41/* Only exported for architectures that don't store the pointer guard
42 value in thread local area. */
43uintptr_t __pointer_chk_guard_local
44 attribute_relro attribute_hidden __attribute__ ((nocommon));
45# endif
46#endif
47
48#ifdef HAVE_PTR_NTHREADS
49/* We need atomic operations. */
50# include <atomic.h>
51#endif
52
53
54#ifndef SHARED
55# include <link.h>
56# include <dl-irel.h>
57
58# ifdef ELF_MACHINE_IRELA
59# define IREL_T ElfW(Rela)
60# define IPLT_START __rela_iplt_start
61# define IPLT_END __rela_iplt_end
62# define IREL elf_irela
63# elif defined ELF_MACHINE_IREL
64# define IREL_T ElfW(Rel)
65# define IPLT_START __rel_iplt_start
66# define IPLT_END __rel_iplt_end
67# define IREL elf_irel
68# endif
69
70static void
71apply_irel (void)
72{
73# ifdef IREL
74 /* We use weak references for these so that we'll still work with a linker
75 that doesn't define them. Such a linker doesn't support IFUNC at all
76 and so uses won't work, but a statically-linked program that doesn't
77 use any IFUNC symbols won't have a problem. */
78 extern const IREL_T IPLT_START[] __attribute__ ((weak));
79 extern const IREL_T IPLT_END[] __attribute__ ((weak));
80 for (const IREL_T *ipltent = IPLT_START; ipltent < IPLT_END; ++ipltent)
81 IREL (ipltent);
82# endif
83}
84#endif
85
86
87#ifdef LIBC_START_MAIN
88# ifdef LIBC_START_DISABLE_INLINE
89# define STATIC static
90# else
91# define STATIC static inline __attribute__ ((always_inline))
92# endif
93#else
94# define STATIC
95# define LIBC_START_MAIN __libc_start_main
96#endif
97
98#ifdef MAIN_AUXVEC_ARG
99/* main gets passed a pointer to the auxiliary. */
100# define MAIN_AUXVEC_DECL , void *
101# define MAIN_AUXVEC_PARAM , auxvec
102#else
103# define MAIN_AUXVEC_DECL
104# define MAIN_AUXVEC_PARAM
105#endif
106
107#ifndef ARCH_INIT_CPU_FEATURES
108# define ARCH_INIT_CPU_FEATURES()
109#endif
110
111#include <libc-start.h>
112
113STATIC int LIBC_START_MAIN (int (*main) (int, char **, char **
114 MAIN_AUXVEC_DECL),
115 int argc,
116 char **argv,
117#ifdef LIBC_START_MAIN_AUXVEC_ARG
118 ElfW(auxv_t) *auxvec,
119#endif
120 __typeof (main) init,
121 void (*fini) (void),
122 void (*rtld_fini) (void),
123 void *stack_end)
124 __attribute__ ((noreturn));
125
126
127/* Note: the fini parameter is ignored here for shared library. It
128 is registered with __cxa_atexit. This had the disadvantage that
129 finalizers were called in more than one place. */
130STATIC int
131LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
132 int argc, char **argv,
133#ifdef LIBC_START_MAIN_AUXVEC_ARG
134 ElfW(auxv_t) *auxvec,
135#endif
136 __typeof (main) init,
137 void (*fini) (void),
138 void (*rtld_fini) (void), void *stack_end)
139{
140 /* Result of the 'main' function. */
141 int result;
142
143 __libc_multiple_libcs = &_dl_starting_up && !_dl_starting_up;
144
145#ifndef SHARED
146 _dl_relocate_static_pie ();
147
148 char **ev = &argv[argc + 1];
149
150 __environ = ev;
151
152 /* Store the lowest stack address. This is done in ld.so if this is
153 the code for the DSO. */
154 __libc_stack_end = stack_end;
155
156# ifdef HAVE_AUX_VECTOR
157 /* First process the auxiliary vector since we need to find the
158 program header to locate an eventually present PT_TLS entry. */
159# ifndef LIBC_START_MAIN_AUXVEC_ARG
160 ElfW(auxv_t) *auxvec;
161 {
162 char **evp = ev;
163 while (*evp++ != NULL)
164 ;
165 auxvec = (ElfW(auxv_t) *) evp;
166 }
167# endif
168 _dl_aux_init (auxvec);
169 if (GL(dl_phdr) == NULL)
170# endif
171 {
172 /* Starting from binutils-2.23, the linker will define the
173 magic symbol __ehdr_start to point to our own ELF header
174 if it is visible in a segment that also includes the phdrs.
175 So we can set up _dl_phdr and _dl_phnum even without any
176 information from auxv. */
177
178 extern const ElfW(Ehdr) __ehdr_start
179 __attribute__ ((weak, visibility ("hidden")));
180 if (&__ehdr_start != NULL)
181 {
182 assert (__ehdr_start.e_phentsize == sizeof *GL(dl_phdr));
183 GL(dl_phdr) = (const void *) &__ehdr_start + __ehdr_start.e_phoff;
184 GL(dl_phnum) = __ehdr_start.e_phnum;
185 }
186 }
187
188 /* Initialize very early so that tunables can use it. */
189 __libc_init_secure ();
190
191 __tunables_init (__environ);
192
193 ARCH_INIT_CPU_FEATURES ();
194
195 /* Perform IREL{,A} relocations. */
196 ARCH_SETUP_IREL ();
197
198 /* The stack guard goes into the TCB, so initialize it early. */
199 ARCH_SETUP_TLS ();
200
201 /* In some architectures, IREL{,A} relocations happen after TLS setup in
202 order to let IFUNC resolvers benefit from TCB information, e.g. powerpc's
203 hwcap and platform fields available in the TCB. */
204 ARCH_APPLY_IREL ();
205
206 /* Set up the stack checker's canary. */
207 uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
208# ifdef THREAD_SET_STACK_GUARD
209 THREAD_SET_STACK_GUARD (stack_chk_guard);
210# else
211 __stack_chk_guard = stack_chk_guard;
212# endif
213
214# ifdef DL_SYSDEP_OSCHECK
215 if (!__libc_multiple_libcs)
216 {
217 /* This needs to run to initiliaze _dl_osversion before TLS
218 setup might check it. */
219 DL_SYSDEP_OSCHECK (__libc_fatal);
220 }
221# endif
222
223 /* Initialize libpthread if linked in. */
224 if (__pthread_initialize_minimal != NULL)
225 __pthread_initialize_minimal ();
226
227 /* Set up the pointer guard value. */
228 uintptr_t pointer_chk_guard = _dl_setup_pointer_guard (_dl_random,
229 stack_chk_guard);
230# ifdef THREAD_SET_POINTER_GUARD
231 THREAD_SET_POINTER_GUARD (pointer_chk_guard);
232# else
233 __pointer_chk_guard_local = pointer_chk_guard;
234# endif
235
236#endif /* !SHARED */
237
238 /* Register the destructor of the dynamic linker if there is any. */
239 if (__glibc_likely (rtld_fini != NULL))
240 __cxa_atexit ((void (*) (void *)) rtld_fini, NULL, NULL);
241
242#ifndef SHARED
243 /* Perform early initialization. In the shared case, this function
244 is called from the dynamic loader as early as possible. */
245 __libc_early_init (true);
246
247 /* Call the initializer of the libc. This is only needed here if we
248 are compiling for the static library in which case we haven't
249 run the constructors in `_dl_start_user'. */
250 __libc_init_first (argc, argv, __environ);
251
252 /* Register the destructor of the program, if any. */
253 if (fini)
254 __cxa_atexit ((void (*) (void *)) fini, NULL, NULL);
255
256 /* Some security at this point. Prevent starting a SUID binary where
257 the standard file descriptors are not opened. We have to do this
258 only for statically linked applications since otherwise the dynamic
259 loader did the work already. */
260 if (__builtin_expect (__libc_enable_secure, 0))
261 __libc_check_standard_fds ();
262#endif
263
264 /* Call the initializer of the program, if any. */
265#ifdef SHARED
266 if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS, 0))
267 GLRO(dl_debug_printf) ("\ninitialize program: %s\n\n", argv[0]);
268#endif
269 if (init)
270 (*init) (argc, argv, __environ MAIN_AUXVEC_PARAM);
271
272#ifdef SHARED
273 /* Auditing checkpoint: we have a new object. */
274 if (__glibc_unlikely (GLRO(dl_naudit) > 0))
275 {
276 struct audit_ifaces *afct = GLRO(dl_audit);
277 struct link_map *head = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
278 for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
279 {
280 if (afct->preinit != NULL)
281 afct->preinit (&link_map_audit_state (head, cnt)->cookie);
282
283 afct = afct->next;
284 }
285 }
286#endif
287
288#ifdef SHARED
289 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
290 GLRO(dl_debug_printf) ("\ntransferring control: %s\n\n", argv[0]);
291#endif
292
293#ifndef SHARED
294 _dl_debug_initialize (0, LM_ID_BASE);
295#endif
296#ifdef HAVE_CLEANUP_JMP_BUF
297 /* Memory for the cancellation buffer. */
298 struct pthread_unwind_buf unwind_buf;
299
300 int not_first_call;
301 not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
302 if (__glibc_likely (! not_first_call))
303 {
304 struct pthread *self = THREAD_SELF;
305
306 /* Store old info. */
307 unwind_buf.priv.data.prev = THREAD_GETMEM (self, cleanup_jmp_buf);
308 unwind_buf.priv.data.cleanup = THREAD_GETMEM (self, cleanup);
309
310 /* Store the new cleanup handler info. */
311 THREAD_SETMEM (self, cleanup_jmp_buf, &unwind_buf);
312
313 /* Run the program. */
314 result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
315 }
316 else
317 {
318 /* Remove the thread-local data. */
319# ifdef SHARED
320 PTHFCT_CALL (ptr__nptl_deallocate_tsd, ());
321# else
322 extern void __nptl_deallocate_tsd (void) __attribute ((weak));
323 __nptl_deallocate_tsd ();
324# endif
325
326 /* One less thread. Decrement the counter. If it is zero we
327 terminate the entire process. */
328 result = 0;
329# ifdef SHARED
330 unsigned int *ptr = __libc_pthread_functions.ptr_nthreads;
331# ifdef PTR_DEMANGLE
332 PTR_DEMANGLE (ptr);
333# endif
334# else
335 extern unsigned int __nptl_nthreads __attribute ((weak));
336 unsigned int *const ptr = &__nptl_nthreads;
337# endif
338
339 if (! atomic_decrement_and_test (ptr))
340 /* Not much left to do but to exit the thread, not the process. */
341 __exit_thread ();
342 }
343#else
344 /* Nothing fancy, just call the function. */
345 result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
346#endif
347
348 exit (result);
349}
350