csu/libc-start.c

   1 /* Copyright (C) 1998-2013 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 <stdlib.h>
  19 #include <stdio.h>
  20 #include <unistd.h>
  21 #include <ldsodefs.h>
  22 #include <bp-sym.h>
  23
  24 extern void __libc_init_first (int argc, char **argv, char **envp);
  25 #ifndef SHARED
  26 extern void __libc_csu_irel (void);
  27 #endif
  28
  29 extern int __libc_multiple_libcs;
  30
  31 #include <tls.h>
  32 #ifndef SHARED
  33 # include <dl-osinfo.h>
  34 extern void __pthread_initialize_minimal (void);
  35 # ifndef THREAD_SET_STACK_GUARD
  36 /* Only exported for architectures that don't store the stack guard canary
  37    in thread local area.  */
  38 uintptr_t __stack_chk_guard attribute_relro;
  39 # endif
  40 #endif
  41
  42 #ifdef HAVE_PTR_NTHREADS
  43 /* We need atomic operations.  */
  44 # include <atomic.h>
  45 #endif
  46
  47
  48 #ifndef SHARED
  49 # include <link.h>
  50 # include <dl-irel.h>
  51
  52 # ifdef ELF_MACHINE_IRELA
  53 #  define IREL_T        ElfW(Rela)
  54 #  define IPLT_START    __rela_iplt_start
  55 #  define IPLT_END      __rela_iplt_end
  56 #  define IREL          elf_irela
  57 # elif defined ELF_MACHINE_IREL
  58 #  define IREL_T        ElfW(Rel)
  59 #  define IPLT_START    __rel_iplt_start
  60 #  define IPLT_END      __rel_iplt_end
  61 #  define IREL          elf_irel
  62 # endif
  63
  64 static void
  65 apply_irel (void)
  66 {
  67 # ifdef IREL
  68   /* We use weak references for these so that we'll still work with a linker
  69      that doesn't define them.  Such a linker doesn't support IFUNC at all
  70      and so uses won't work, but a statically-linked program that doesn't
  71      use any IFUNC symbols won't have a problem.  */
  72   extern const IREL_T IPLT_START[] __attribute__ ((weak));
  73   extern const IREL_T IPLT_END[] __attribute__ ((weak));
  74   for (const IREL_T *ipltent = IPLT_START; ipltent < IPLT_END; ++ipltent)
  75     IREL (ipltent);
  76 # endif
  77 }
  78 #endif
  79
  80
  81 #ifdef LIBC_START_MAIN
  82 # ifdef LIBC_START_DISABLE_INLINE
  83 #  define STATIC static
  84 # else
  85 #  define STATIC static inline __attribute__ ((always_inline))
  86 # endif
  87 #else
  88 # define STATIC
  89 # define LIBC_START_MAIN BP_SYM (__libc_start_main)
  90 #endif
  91
  92 #ifdef MAIN_AUXVEC_ARG
  93 /* main gets passed a pointer to the auxiliary.  */
  94 # define MAIN_AUXVEC_DECL       , void *
  95 # define MAIN_AUXVEC_PARAM      , auxvec
  96 #else
  97 # define MAIN_AUXVEC_DECL
  98 # define MAIN_AUXVEC_PARAM
  99 #endif
 100
 101 STATIC int LIBC_START_MAIN (int (*main) (int, char **, char **
 102                                          MAIN_AUXVEC_DECL),
 103                             int argc,
 104                             char *__unbounded *__unbounded ubp_av,
 105 #ifdef LIBC_START_MAIN_AUXVEC_ARG
 106                             ElfW(auxv_t) *__unbounded auxvec,
 107 #endif
 108                             __typeof (main) init,
 109                             void (*fini) (void),
 110                             void (*rtld_fini) (void),
 111                             void *__unbounded stack_end)
 112      __attribute__ ((noreturn));
 113
 114
 115 /* Note: the fini parameter is ignored here for shared library.  It
 116    is registered with __cxa_atexit.  This had the disadvantage that
 117    finalizers were called in more than one place.  */
 118 STATIC int
 119 LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
 120                  int argc, char *__unbounded *__unbounded ubp_av,
 121 #ifdef LIBC_START_MAIN_AUXVEC_ARG
 122                  ElfW(auxv_t) *__unbounded auxvec,
 123 #endif
 124                  __typeof (main) init,
 125                  void (*fini) (void),
 126                  void (*rtld_fini) (void), void *__unbounded stack_end)
 127 {
 128 #if __BOUNDED_POINTERS__
 129   char **argv;
 130 #else
 131 # define argv ubp_av
 132 #endif
 133
 134   /* Result of the 'main' function.  */
 135   int result;
 136
 137   __libc_multiple_libcs = &_dl_starting_up && !_dl_starting_up;
 138
 139 #ifndef SHARED
 140   char *__unbounded *__unbounded ubp_ev = &ubp_av[argc + 1];
 141
 142   __environ = ubp_ev;
 143
 144   /* Store the lowest stack address.  This is done in ld.so if this is
 145      the code for the DSO.  */
 146   __libc_stack_end = stack_end;
 147
 148 # ifdef HAVE_AUX_VECTOR
 149   /* First process the auxiliary vector since we need to find the
 150      program header to locate an eventually present PT_TLS entry.  */
 151 #  ifndef LIBC_START_MAIN_AUXVEC_ARG
 152   ElfW(auxv_t) *__unbounded auxvec;
 153   {
 154     char *__unbounded *__unbounded evp = ubp_ev;
 155     while (*evp++ != NULL)
 156       ;
 157     auxvec = (ElfW(auxv_t) *__unbounded) evp;
 158   }
 159 #  endif
 160   _dl_aux_init (auxvec);
 161 # endif
 162 # ifdef DL_SYSDEP_OSCHECK
 163   if (!__libc_multiple_libcs)
 164     {
 165       /* This needs to run to initiliaze _dl_osversion before TLS
 166          setup might check it.  */
 167       DL_SYSDEP_OSCHECK (__libc_fatal);
 168     }
 169 # endif
 170
 171   /* Perform IREL{,A} relocations.  */
 172   apply_irel ();
 173
 174   /* Initialize the thread library at least a bit since the libgcc
 175      functions are using thread functions if these are available and
 176      we need to setup errno.  */
 177   __pthread_initialize_minimal ();
 178
 179   /* Set up the stack checker's canary.  */
 180   uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
 181 # ifdef THREAD_SET_STACK_GUARD
 182   THREAD_SET_STACK_GUARD (stack_chk_guard);
 183 # else
 184   __stack_chk_guard = stack_chk_guard;
 185 # endif
 186 #endif
 187
 188   /* Register the destructor of the dynamic linker if there is any.  */
 189   if (__builtin_expect (rtld_fini != NULL, 1))
 190     __cxa_atexit ((void (*) (void *)) rtld_fini, NULL, NULL);
 191
 192 #ifndef SHARED
 193   /* Call the initializer of the libc.  This is only needed here if we
 194      are compiling for the static library in which case we haven't
 195      run the constructors in `_dl_start_user'.  */
 196   __libc_init_first (argc, argv, __environ);
 197
 198   /* Register the destructor of the program, if any.  */
 199   if (fini)
 200     __cxa_atexit ((void (*) (void *)) fini, NULL, NULL);
 201
 202   /* Some security at this point.  Prevent starting a SUID binary where
 203      the standard file descriptors are not opened.  We have to do this
 204      only for statically linked applications since otherwise the dynamic
 205      loader did the work already.  */
 206   if (__builtin_expect (__libc_enable_secure, 0))
 207     __libc_check_standard_fds ();
 208 #endif
 209
 210   /* Call the initializer of the program, if any.  */
 211 #ifdef SHARED
 212   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS, 0))
 213     GLRO(dl_debug_printf) ("\ninitialize program: %s\n\n", argv[0]);
 214 #endif
 215   if (init)
 216     (*init) (argc, argv, __environ MAIN_AUXVEC_PARAM);
 217
 218 #ifdef SHARED
 219   /* Auditing checkpoint: we have a new object.  */
 220   if (__builtin_expect (GLRO(dl_naudit) > 0, 0))
 221     {
 222       struct audit_ifaces *afct = GLRO(dl_audit);
 223       struct link_map *head = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
 224       for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 225         {
 226           if (afct->preinit != NULL)
 227             afct->preinit (&head->l_audit[cnt].cookie);
 228
 229           afct = afct->next;
 230         }
 231     }
 232 #endif
 233
 234 #ifdef SHARED
 235   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS, 0))
 236     GLRO(dl_debug_printf) ("\ntransferring control: %s\n\n", argv[0]);
 237 #endif
 238
 239 #ifdef HAVE_CLEANUP_JMP_BUF
 240   /* Memory for the cancellation buffer.  */
 241   struct pthread_unwind_buf unwind_buf;
 242
 243   int not_first_call;
 244   not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
 245   if (__builtin_expect (! not_first_call, 1))
 246     {
 247       struct pthread *self = THREAD_SELF;
 248
 249       /* Store old info.  */
 250       unwind_buf.priv.data.prev = THREAD_GETMEM (self, cleanup_jmp_buf);
 251       unwind_buf.priv.data.cleanup = THREAD_GETMEM (self, cleanup);
 252
 253       /* Store the new cleanup handler info.  */
 254       THREAD_SETMEM (self, cleanup_jmp_buf, &unwind_buf);
 255
 256       /* Run the program.  */
 257       result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
 258     }
 259   else
 260     {
 261       /* Remove the thread-local data.  */
 262 # ifdef SHARED
 263       PTHFCT_CALL (ptr__nptl_deallocate_tsd, ());
 264 # else
 265       extern void __nptl_deallocate_tsd (void) __attribute ((weak));
 266       __nptl_deallocate_tsd ();
 267 # endif
 268
 269       /* One less thread.  Decrement the counter.  If it is zero we
 270          terminate the entire process.  */
 271       result = 0;
 272 # ifdef SHARED
 273       unsigned int *ptr = __libc_pthread_functions.ptr_nthreads;
 274 #  ifdef PTR_DEMANGLE
 275       PTR_DEMANGLE (ptr);
 276 #  endif
 277 # else
 278       extern unsigned int __nptl_nthreads __attribute ((weak));
 279       unsigned int *const ptr = &__nptl_nthreads;
 280 # endif
 281
 282       if (! atomic_decrement_and_test (ptr))
 283         /* Not much left to do but to exit the thread, not the process.  */
 284         __exit_thread (0);
 285     }
 286 #else
 287   /* Nothing fancy, just call the function.  */
 288   result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
 289 #endif
 290
 291   exit (result);
 292 }