1/* Copyright (C) 1998-2021 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/* Mark symbols hidden in static PIE for early self relocation to work. */
19#if BUILD_PIE_DEFAULT
20# pragma GCC visibility push(hidden)
21#endif
22#include <assert.h>
23#include <stdlib.h>
24#include <stdio.h>
25#include <unistd.h>
26#include <ldsodefs.h>
27#include <exit-thread.h>
28#include <libc-diag.h>
29#include <libc-internal.h>
30#include <elf/libc-early-init.h>
31#include <stdbool.h>
32
33#include <elf/dl-tunables.h>
34
35extern void __libc_init_first (int argc, char **argv, char **envp);
36
37#include <tls.h>
38#ifndef SHARED
39# include <dl-osinfo.h>
40# ifndef THREAD_SET_STACK_GUARD
41/* Only exported for architectures that don't store the stack guard canary
42 in thread local area. */
43uintptr_t __stack_chk_guard attribute_relro;
44# endif
45# ifndef THREAD_SET_POINTER_GUARD
46/* Only exported for architectures that don't store the pointer guard
47 value in thread local area. */
48uintptr_t __pointer_chk_guard_local
49 attribute_relro attribute_hidden __attribute__ ((nocommon));
50# endif
51#endif
52
53#ifdef HAVE_PTR_NTHREADS
54/* We need atomic operations. */
55# include <atomic.h>
56#endif
57
58
59#ifndef SHARED
60# include <link.h>
61# include <dl-irel.h>
62
63# ifdef ELF_MACHINE_IRELA
64# define IREL_T ElfW(Rela)
65# define IPLT_START __rela_iplt_start
66# define IPLT_END __rela_iplt_end
67# define IREL elf_irela
68# elif defined ELF_MACHINE_IREL
69# define IREL_T ElfW(Rel)
70# define IPLT_START __rel_iplt_start
71# define IPLT_END __rel_iplt_end
72# define IREL elf_irel
73# endif
74
75static void
76apply_irel (void)
77{
78# ifdef IREL
79 /* We use weak references for these so that we'll still work with a linker
80 that doesn't define them. Such a linker doesn't support IFUNC at all
81 and so uses won't work, but a statically-linked program that doesn't
82 use any IFUNC symbols won't have a problem. */
83 extern const IREL_T IPLT_START[] __attribute__ ((weak));
84 extern const IREL_T IPLT_END[] __attribute__ ((weak));
85 for (const IREL_T *ipltent = IPLT_START; ipltent < IPLT_END; ++ipltent)
86 IREL (ipltent);
87# endif
88}
89#endif
90
91
92#ifdef LIBC_START_MAIN
93# ifdef LIBC_START_DISABLE_INLINE
94# define STATIC static
95# else
96# define STATIC static inline __attribute__ ((always_inline))
97# endif
98#else
99# define STATIC
100# define LIBC_START_MAIN __libc_start_main
101#endif
102
103#ifdef MAIN_AUXVEC_ARG
104/* main gets passed a pointer to the auxiliary. */
105# define MAIN_AUXVEC_DECL , void *
106# define MAIN_AUXVEC_PARAM , auxvec
107#else
108# define MAIN_AUXVEC_DECL
109# define MAIN_AUXVEC_PARAM
110#endif
111
112#ifndef ARCH_INIT_CPU_FEATURES
113# define ARCH_INIT_CPU_FEATURES()
114#endif
115
116#include <libc-start.h>
117
118STATIC int LIBC_START_MAIN (int (*main) (int, char **, char **
119 MAIN_AUXVEC_DECL),
120 int argc,
121 char **argv,
122#ifdef LIBC_START_MAIN_AUXVEC_ARG
123 ElfW(auxv_t) *auxvec,
124#endif
125 __typeof (main) init,
126 void (*fini) (void),
127 void (*rtld_fini) (void),
128 void *stack_end)
129 __attribute__ ((noreturn));
130
131
132/* Note: the fini parameter is ignored here for shared library. It
133 is registered with __cxa_atexit. This had the disadvantage that
134 finalizers were called in more than one place. */
135STATIC int
136LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
137 int argc, char **argv,
138#ifdef LIBC_START_MAIN_AUXVEC_ARG
139 ElfW(auxv_t) *auxvec,
140#endif
141 __typeof (main) init,
142 void (*fini) (void),
143 void (*rtld_fini) (void), void *stack_end)
144{
145 /* Result of the 'main' function. */
146 int result;
147
148#ifndef SHARED
149 char **ev = &argv[argc + 1];
150
151 __environ = ev;
152
153 /* Store the lowest stack address. This is done in ld.so if this is
154 the code for the DSO. */
155 __libc_stack_end = stack_end;
156
157# ifdef HAVE_AUX_VECTOR
158 /* First process the auxiliary vector since we need to find the
159 program header to locate an eventually present PT_TLS entry. */
160# ifndef LIBC_START_MAIN_AUXVEC_ARG
161 ElfW(auxv_t) *auxvec;
162 {
163 char **evp = ev;
164 while (*evp++ != NULL)
165 ;
166 auxvec = (ElfW(auxv_t) *) evp;
167 }
168# endif
169 _dl_aux_init (auxvec);
170 if (GL(dl_phdr) == NULL)
171# endif
172 {
173 /* Starting from binutils-2.23, the linker will define the
174 magic symbol __ehdr_start to point to our own ELF header
175 if it is visible in a segment that also includes the phdrs.
176 So we can set up _dl_phdr and _dl_phnum even without any
177 information from auxv. */
178
179 extern const ElfW(Ehdr) __ehdr_start
180# if BUILD_PIE_DEFAULT
181 __attribute__ ((visibility ("hidden")));
182# else
183 __attribute__ ((weak, visibility ("hidden")));
184 if (&__ehdr_start != NULL)
185# endif
186 {
187 assert (__ehdr_start.e_phentsize == sizeof *GL(dl_phdr));
188 GL(dl_phdr) = (const void *) &__ehdr_start + __ehdr_start.e_phoff;
189 GL(dl_phnum) = __ehdr_start.e_phnum;
190 }
191 }
192
193 /* Initialize very early so that tunables can use it. */
194 __libc_init_secure ();
195
196 __tunables_init (__environ);
197
198 ARCH_INIT_CPU_FEATURES ();
199
200 /* Do static pie self relocation after tunables and cpu features
201 are setup for ifunc resolvers. Before this point relocations
202 must be avoided. */
203 _dl_relocate_static_pie ();
204
205 /* Perform IREL{,A} relocations. */
206 ARCH_SETUP_IREL ();
207
208 /* The stack guard goes into the TCB, so initialize it early. */
209 ARCH_SETUP_TLS ();
210
211 /* In some architectures, IREL{,A} relocations happen after TLS setup in
212 order to let IFUNC resolvers benefit from TCB information, e.g. powerpc's
213 hwcap and platform fields available in the TCB. */
214 ARCH_APPLY_IREL ();
215
216 /* Set up the stack checker's canary. */
217 uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
218# ifdef THREAD_SET_STACK_GUARD
219 THREAD_SET_STACK_GUARD (stack_chk_guard);
220# else
221 __stack_chk_guard = stack_chk_guard;
222# endif
223
224# ifdef DL_SYSDEP_OSCHECK
225 {
226 /* This needs to run to initiliaze _dl_osversion before TLS
227 setup might check it. */
228 DL_SYSDEP_OSCHECK (__libc_fatal);
229 }
230# endif
231
232 /* Initialize libpthread if linked in. */
233 if (__pthread_initialize_minimal != NULL)
234 __pthread_initialize_minimal ();
235
236 /* Set up the pointer guard value. */
237 uintptr_t pointer_chk_guard = _dl_setup_pointer_guard (_dl_random,
238 stack_chk_guard);
239# ifdef THREAD_SET_POINTER_GUARD
240 THREAD_SET_POINTER_GUARD (pointer_chk_guard);
241# else
242 __pointer_chk_guard_local = pointer_chk_guard;
243# endif
244
245#endif /* !SHARED */
246
247 /* Register the destructor of the dynamic linker if there is any. */
248 if (__glibc_likely (rtld_fini != NULL))
249 __cxa_atexit ((void (*) (void *)) rtld_fini, NULL, NULL);
250
251#ifndef SHARED
252 /* Perform early initialization. In the shared case, this function
253 is called from the dynamic loader as early as possible. */
254 __libc_early_init (true);
255
256 /* Call the initializer of the libc. This is only needed here if we
257 are compiling for the static library in which case we haven't
258 run the constructors in `_dl_start_user'. */
259 __libc_init_first (argc, argv, __environ);
260
261 /* Register the destructor of the program, if any. */
262 if (fini)
263 __cxa_atexit ((void (*) (void *)) fini, NULL, NULL);
264
265 /* Some security at this point. Prevent starting a SUID binary where
266 the standard file descriptors are not opened. We have to do this
267 only for statically linked applications since otherwise the dynamic
268 loader did the work already. */
269 if (__builtin_expect (__libc_enable_secure, 0))
270 __libc_check_standard_fds ();
271#endif
272
273 /* Call the initializer of the program, if any. */
274#ifdef SHARED
275 if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS, 0))
276 GLRO(dl_debug_printf) ("\ninitialize program: %s\n\n", argv[0]);
277#endif
278 if (init)
279 (*init) (argc, argv, __environ MAIN_AUXVEC_PARAM);
280
281#ifdef SHARED
282 /* Auditing checkpoint: we have a new object. */
283 if (__glibc_unlikely (GLRO(dl_naudit) > 0))
284 {
285 struct audit_ifaces *afct = GLRO(dl_audit);
286 struct link_map *head = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
287 for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
288 {
289 if (afct->preinit != NULL)
290 afct->preinit (&link_map_audit_state (head, cnt)->cookie);
291
292 afct = afct->next;
293 }
294 }
295#endif
296
297#ifdef SHARED
298 if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
299 GLRO(dl_debug_printf) ("\ntransferring control: %s\n\n", argv[0]);
300#endif
301
302#ifndef SHARED
303 _dl_debug_initialize (0, LM_ID_BASE);
304#endif
305#ifdef HAVE_CLEANUP_JMP_BUF
306 /* Memory for the cancellation buffer. */
307 struct pthread_unwind_buf unwind_buf;
308
309 int not_first_call;
310 DIAG_PUSH_NEEDS_COMMENT;
311#if __GNUC_PREREQ (7, 0)
312 /* This call results in a -Wstringop-overflow warning because struct
313 pthread_unwind_buf is smaller than jmp_buf. setjmp and longjmp
314 do not use anything beyond the common prefix (they never access
315 the saved signal mask), so that is a false positive. */
316 DIAG_IGNORE_NEEDS_COMMENT (11, "-Wstringop-overflow=");
317#endif
318 not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
319 DIAG_POP_NEEDS_COMMENT;
320 if (__glibc_likely (! not_first_call))
321 {
322 struct pthread *self = THREAD_SELF;
323
324 /* Store old info. */
325 unwind_buf.priv.data.prev = THREAD_GETMEM (self, cleanup_jmp_buf);
326 unwind_buf.priv.data.cleanup = THREAD_GETMEM (self, cleanup);
327
328 /* Store the new cleanup handler info. */
329 THREAD_SETMEM (self, cleanup_jmp_buf, &unwind_buf);
330
331 /* Run the program. */
332 result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
333 }
334 else
335 {
336 /* Remove the thread-local data. */
337# ifdef SHARED
338 PTHFCT_CALL (ptr__nptl_deallocate_tsd, ());
339# else
340 extern void __nptl_deallocate_tsd (void) __attribute ((weak));
341 __nptl_deallocate_tsd ();
342# endif
343
344 /* One less thread. Decrement the counter. If it is zero we
345 terminate the entire process. */
346 result = 0;
347# ifdef SHARED
348 unsigned int *ptr = __libc_pthread_functions.ptr_nthreads;
349# ifdef PTR_DEMANGLE
350 PTR_DEMANGLE (ptr);
351# endif
352# else
353 extern unsigned int __nptl_nthreads __attribute ((weak));
354 unsigned int *const ptr = &__nptl_nthreads;
355# endif
356
357 if (! atomic_decrement_and_test (ptr))
358 /* Not much left to do but to exit the thread, not the process. */
359 __exit_thread ();
360 }
361#else
362 /* Nothing fancy, just call the function. */
363 result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
364#endif
365
366 exit (result);
367}
368