1/* Copyright (C) 1998-2017 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 <http://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
26#include <elf/dl-tunables.h>
27
28extern void __libc_init_first (int argc, char **argv, char **envp);
29
30extern int __libc_multiple_libcs;
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 char **ev = &argv[argc + 1];
147
148 __environ = ev;
149
150 /* Store the lowest stack address. This is done in ld.so if this is
151 the code for the DSO. */
152 __libc_stack_end = stack_end;
153
154# ifdef HAVE_AUX_VECTOR
155 /* First process the auxiliary vector since we need to find the
156 program header to locate an eventually present PT_TLS entry. */
157# ifndef LIBC_START_MAIN_AUXVEC_ARG
158 ElfW(auxv_t) *auxvec;
159 {
160 char **evp = ev;
161 while (*evp++ != NULL)
162 ;
163 auxvec = (ElfW(auxv_t) *) evp;
164 }
165# endif
166 _dl_aux_init (auxvec);
167 if (GL(dl_phdr) == NULL)
168# endif
169 {
170 /* Starting from binutils-2.23, the linker will define the
171 magic symbol __ehdr_start to point to our own ELF header
172 if it is visible in a segment that also includes the phdrs.
173 So we can set up _dl_phdr and _dl_phnum even without any
174 information from auxv. */
175
176 extern const ElfW(Ehdr) __ehdr_start
177 __attribute__ ((weak, visibility ("hidden")));
178 if (&__ehdr_start != NULL)
179 {
180 assert (__ehdr_start.e_phentsize == sizeof *GL(dl_phdr));
181 GL(dl_phdr) = (const void *) &__ehdr_start + __ehdr_start.e_phoff;
182 GL(dl_phnum) = __ehdr_start.e_phnum;
183 }
184 }
185
186 /* Initialize very early so that tunables can use it. */
187 __libc_init_secure ();
188
189 __tunables_init (__environ);
190
191 ARCH_INIT_CPU_FEATURES ();
192
193 /* Perform IREL{,A} relocations. */
194 ARCH_SETUP_IREL ();
195
196 /* The stack guard goes into the TCB, so initialize it early. */
197 __libc_setup_tls ();
198
199 /* In some architectures, IREL{,A} relocations happen after TLS setup in
200 order to let IFUNC resolvers benefit from TCB information, e.g. powerpc's
201 hwcap and platform fields available in the TCB. */
202 ARCH_APPLY_IREL ();
203
204 /* Set up the stack checker's canary. */
205 uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
206# ifdef THREAD_SET_STACK_GUARD
207 THREAD_SET_STACK_GUARD (stack_chk_guard);
208# else
209 __stack_chk_guard = stack_chk_guard;
210# endif
211
212# ifdef DL_SYSDEP_OSCHECK
213 if (!__libc_multiple_libcs)
214 {
215 /* This needs to run to initiliaze _dl_osversion before TLS
216 setup might check it. */
217 DL_SYSDEP_OSCHECK (__libc_fatal);
218 }
219# endif
220
221 /* Initialize libpthread if linked in. */
222 if (__pthread_initialize_minimal != NULL)
223 __pthread_initialize_minimal ();
224
225 /* Set up the pointer guard value. */
226 uintptr_t pointer_chk_guard = _dl_setup_pointer_guard (_dl_random,
227 stack_chk_guard);
228# ifdef THREAD_SET_POINTER_GUARD
229 THREAD_SET_POINTER_GUARD (pointer_chk_guard);
230# else
231 __pointer_chk_guard_local = pointer_chk_guard;
232# endif
233
234#endif /* !SHARED */
235
236 /* Register the destructor of the dynamic linker if there is any. */
237 if (__glibc_likely (rtld_fini != NULL))
238 __cxa_atexit ((void (*) (void *)) rtld_fini, NULL, NULL);
239
240#ifndef SHARED
241 /* Call the initializer of the libc. This is only needed here if we
242 are compiling for the static library in which case we haven't
243 run the constructors in `_dl_start_user'. */
244 __libc_init_first (argc, argv, __environ);
245
246 /* Register the destructor of the program, if any. */
247 if (fini)
248 __cxa_atexit ((void (*) (void *)) fini, NULL, NULL);
249
250 /* Some security at this point. Prevent starting a SUID binary where
251 the standard file descriptors are not opened. We have to do this
252 only for statically linked applications since otherwise the dynamic
253 loader did the work already. */
254 if (__builtin_expect (__libc_enable_secure, 0))
255 __libc_check_standard_fds ();
256#endif
257
258 /* Call the initializer of the program, if any. */
259#ifdef SHARED
260 if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS, 0))
261 GLRO(dl_debug_printf) ("\ninitialize program: %s\n\n", argv[0]);
262#endif
263 if (init)
264 (*init) (argc, argv, __environ MAIN_AUXVEC_PARAM);
265
266#ifdef SHARED
267 /* Auditing checkpoint: we have a new object. */
268 if (__glibc_unlikely (GLRO(dl_naudit) > 0))
269 {
270 struct audit_ifaces *afct = GLRO(dl_audit);
271 struct link_map *head = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
272 for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
273 {
274 if (afct->preinit != NULL)
275 afct->preinit (&head->l_audit[cnt].cookie);
276
277 afct = afct->next;
278 }
279 }
280#endif
281
282#ifdef SHARED
283 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
284 GLRO(dl_debug_printf) ("\ntransferring control: %s\n\n", argv[0]);
285#endif
286
287#ifndef SHARED
288 _dl_debug_initialize (0, LM_ID_BASE);
289#endif
290#ifdef HAVE_CLEANUP_JMP_BUF
291 /* Memory for the cancellation buffer. */
292 struct pthread_unwind_buf unwind_buf;
293
294 int not_first_call;
295 not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
296 if (__glibc_likely (! not_first_call))
297 {
298 struct pthread *self = THREAD_SELF;
299
300 /* Store old info. */
301 unwind_buf.priv.data.prev = THREAD_GETMEM (self, cleanup_jmp_buf);
302 unwind_buf.priv.data.cleanup = THREAD_GETMEM (self, cleanup);
303
304 /* Store the new cleanup handler info. */
305 THREAD_SETMEM (self, cleanup_jmp_buf, &unwind_buf);
306
307 /* Run the program. */
308 result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
309 }
310 else
311 {
312 /* Remove the thread-local data. */
313# ifdef SHARED
314 PTHFCT_CALL (ptr__nptl_deallocate_tsd, ());
315# else
316 extern void __nptl_deallocate_tsd (void) __attribute ((weak));
317 __nptl_deallocate_tsd ();
318# endif
319
320 /* One less thread. Decrement the counter. If it is zero we
321 terminate the entire process. */
322 result = 0;
323# ifdef SHARED
324 unsigned int *ptr = __libc_pthread_functions.ptr_nthreads;
325# ifdef PTR_DEMANGLE
326 PTR_DEMANGLE (ptr);
327# endif
328# else
329 extern unsigned int __nptl_nthreads __attribute ((weak));
330 unsigned int *const ptr = &__nptl_nthreads;
331# endif
332
333 if (! atomic_decrement_and_test (ptr))
334 /* Not much left to do but to exit the thread, not the process. */
335 __exit_thread ();
336 }
337#else
338 /* Nothing fancy, just call the function. */
339 result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
340#endif
341
342 exit (result);
343}
344