csu/libc-start.c

   1 /* Copyright (C) 1998-2016 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
  25 extern void __libc_init_first (int argc, char **argv, char **envp);
  26 #ifndef SHARED
  27 extern void __libc_csu_irel (void);
  28 #endif
  29
  30 extern int __libc_multiple_libcs;
  31
  32 #include <tls.h>
  33 #ifndef SHARED
  34 # include <dl-osinfo.h>
  35 extern void __pthread_initialize_minimal (void);
  36 # ifndef THREAD_SET_STACK_GUARD
  37 /* Only exported for architectures that don't store the stack guard canary
  38    in thread local area.  */
  39 uintptr_t __stack_chk_guard attribute_relro;
  40 # endif
  41 # ifndef  THREAD_SET_POINTER_GUARD
  42 /* Only exported for architectures that don't store the pointer guard
  43    value in thread local area.  */
  44 uintptr_t __pointer_chk_guard_local
  45         attribute_relro attribute_hidden __attribute__ ((nocommon));
  46 # endif
  47 #endif
  48
  49 #ifdef HAVE_PTR_NTHREADS
  50 /* We need atomic operations.  */
  51 # include <atomic.h>
  52 #endif
  53
  54
  55 #ifndef SHARED
  56 # include <link.h>
  57 # include <dl-irel.h>
  58
  59 # ifdef ELF_MACHINE_IRELA
  60 #  define IREL_T        ElfW(Rela)
  61 #  define IPLT_START    __rela_iplt_start
  62 #  define IPLT_END      __rela_iplt_end
  63 #  define IREL          elf_irela
  64 # elif defined ELF_MACHINE_IREL
  65 #  define IREL_T        ElfW(Rel)
  66 #  define IPLT_START    __rel_iplt_start
  67 #  define IPLT_END      __rel_iplt_end
  68 #  define IREL          elf_irel
  69 # endif
  70
  71 static void
  72 apply_irel (void)
  73 {
  74 # ifdef IREL
  75   /* We use weak references for these so that we'll still work with a linker
  76      that doesn't define them.  Such a linker doesn't support IFUNC at all
  77      and so uses won't work, but a statically-linked program that doesn't
  78      use any IFUNC symbols won't have a problem.  */
  79   extern const IREL_T IPLT_START[] __attribute__ ((weak));
  80   extern const IREL_T IPLT_END[] __attribute__ ((weak));
  81   for (const IREL_T *ipltent = IPLT_START; ipltent < IPLT_END; ++ipltent)
  82     IREL (ipltent);
  83 # endif
  84 }
  85 #endif
  86
  87
  88 #ifdef LIBC_START_MAIN
  89 # ifdef LIBC_START_DISABLE_INLINE
  90 #  define STATIC static
  91 # else
  92 #  define STATIC static inline __attribute__ ((always_inline))
  93 # endif
  94 #else
  95 # define STATIC
  96 # define LIBC_START_MAIN __libc_start_main
  97 #endif
  98
  99 #ifdef MAIN_AUXVEC_ARG
 100 /* main gets passed a pointer to the auxiliary.  */
 101 # define MAIN_AUXVEC_DECL       , void *
 102 # define MAIN_AUXVEC_PARAM      , auxvec
 103 #else
 104 # define MAIN_AUXVEC_DECL
 105 # define MAIN_AUXVEC_PARAM
 106 #endif
 107
 108 STATIC int LIBC_START_MAIN (int (*main) (int, char **, char **
 109                                          MAIN_AUXVEC_DECL),
 110                             int argc,
 111                             char **argv,
 112 #ifdef LIBC_START_MAIN_AUXVEC_ARG
 113                             ElfW(auxv_t) *auxvec,
 114 #endif
 115                             __typeof (main) init,
 116                             void (*fini) (void),
 117                             void (*rtld_fini) (void),
 118                             void *stack_end)
 119      __attribute__ ((noreturn));
 120
 121
 122 /* Note: the fini parameter is ignored here for shared library.  It
 123    is registered with __cxa_atexit.  This had the disadvantage that
 124    finalizers were called in more than one place.  */
 125 STATIC int
 126 LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
 127                  int argc, char **argv,
 128 #ifdef LIBC_START_MAIN_AUXVEC_ARG
 129                  ElfW(auxv_t) *auxvec,
 130 #endif
 131                  __typeof (main) init,
 132                  void (*fini) (void),
 133                  void (*rtld_fini) (void), void *stack_end)
 134 {
 135   /* Result of the 'main' function.  */
 136   int result;
 137
 138   __libc_multiple_libcs = &_dl_starting_up && !_dl_starting_up;
 139
 140 #ifndef SHARED
 141   char **ev = &argv[argc + 1];
 142
 143   __environ = ev;
 144
 145   /* Store the lowest stack address.  This is done in ld.so if this is
 146      the code for the DSO.  */
 147   __libc_stack_end = stack_end;
 148
 149 # ifdef HAVE_AUX_VECTOR
 150   /* First process the auxiliary vector since we need to find the
 151      program header to locate an eventually present PT_TLS entry.  */
 152 #  ifndef LIBC_START_MAIN_AUXVEC_ARG
 153   ElfW(auxv_t) *auxvec;
 154   {
 155     char **evp = ev;
 156     while (*evp++ != NULL)
 157       ;
 158     auxvec = (ElfW(auxv_t) *) evp;
 159   }
 160 #  endif
 161   _dl_aux_init (auxvec);
 162   if (GL(dl_phdr) == NULL)
 163 # endif
 164     {
 165       /* Starting from binutils-2.23, the linker will define the
 166          magic symbol __ehdr_start to point to our own ELF header
 167          if it is visible in a segment that also includes the phdrs.
 168          So we can set up _dl_phdr and _dl_phnum even without any
 169          information from auxv.  */
 170
 171       extern const ElfW(Ehdr) __ehdr_start
 172         __attribute__ ((weak, visibility ("hidden")));
 173       if (&__ehdr_start != NULL)
 174         {
 175           assert (__ehdr_start.e_phentsize == sizeof *GL(dl_phdr));
 176           GL(dl_phdr) = (const void *) &__ehdr_start + __ehdr_start.e_phoff;
 177           GL(dl_phnum) = __ehdr_start.e_phnum;
 178         }
 179     }
 180
 181 # ifdef DL_SYSDEP_OSCHECK
 182   if (!__libc_multiple_libcs)
 183     {
 184       /* This needs to run to initiliaze _dl_osversion before TLS
 185          setup might check it.  */
 186       DL_SYSDEP_OSCHECK (__libc_fatal);
 187     }
 188 # endif
 189
 190   /* Perform IREL{,A} relocations.  */
 191   apply_irel ();
 192
 193   /* Initialize the thread library at least a bit since the libgcc
 194      functions are using thread functions if these are available and
 195      we need to setup errno.  */
 196   __pthread_initialize_minimal ();
 197
 198   /* Set up the stack checker's canary.  */
 199   uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
 200 # ifdef THREAD_SET_STACK_GUARD
 201   THREAD_SET_STACK_GUARD (stack_chk_guard);
 202 # else
 203   __stack_chk_guard = stack_chk_guard;
 204 # endif
 205
 206   /* Set up the pointer guard value.  */
 207   uintptr_t pointer_chk_guard = _dl_setup_pointer_guard (_dl_random,
 208                                                          stack_chk_guard);
 209 # ifdef THREAD_SET_POINTER_GUARD
 210   THREAD_SET_POINTER_GUARD (pointer_chk_guard);
 211 # else
 212   __pointer_chk_guard_local = pointer_chk_guard;
 213 # endif
 214
 215 #endif
 216
 217   /* Register the destructor of the dynamic linker if there is any.  */
 218   if (__glibc_likely (rtld_fini != NULL))
 219     __cxa_atexit ((void (*) (void *)) rtld_fini, NULL, NULL);
 220
 221 #ifndef SHARED
 222   /* Call the initializer of the libc.  This is only needed here if we
 223      are compiling for the static library in which case we haven't
 224      run the constructors in `_dl_start_user'.  */
 225   __libc_init_first (argc, argv, __environ);
 226
 227   /* Register the destructor of the program, if any.  */
 228   if (fini)
 229     __cxa_atexit ((void (*) (void *)) fini, NULL, NULL);
 230
 231   /* Some security at this point.  Prevent starting a SUID binary where
 232      the standard file descriptors are not opened.  We have to do this
 233      only for statically linked applications since otherwise the dynamic
 234      loader did the work already.  */
 235   if (__builtin_expect (__libc_enable_secure, 0))
 236     __libc_check_standard_fds ();
 237 #endif
 238
 239   /* Call the initializer of the program, if any.  */
 240 #ifdef SHARED
 241   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS, 0))
 242     GLRO(dl_debug_printf) ("\ninitialize program: %s\n\n", argv[0]);
 243 #endif
 244   if (init)
 245     (*init) (argc, argv, __environ MAIN_AUXVEC_PARAM);
 246
 247 #ifdef SHARED
 248   /* Auditing checkpoint: we have a new object.  */
 249   if (__glibc_unlikely (GLRO(dl_naudit) > 0))
 250     {
 251       struct audit_ifaces *afct = GLRO(dl_audit);
 252       struct link_map *head = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
 253       for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 254         {
 255           if (afct->preinit != NULL)
 256             afct->preinit (&head->l_audit[cnt].cookie);
 257
 258           afct = afct->next;
 259         }
 260     }
 261 #endif
 262
 263 #ifdef SHARED
 264   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
 265     GLRO(dl_debug_printf) ("\ntransferring control: %s\n\n", argv[0]);
 266 #endif
 267
 268 #ifndef SHARED
 269   _dl_debug_initialize (0, LM_ID_BASE);
 270 #endif
 271 #ifdef HAVE_CLEANUP_JMP_BUF
 272   /* Memory for the cancellation buffer.  */
 273   struct pthread_unwind_buf unwind_buf;
 274
 275   int not_first_call;
 276   not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
 277   if (__glibc_likely (! not_first_call))
 278     {
 279       struct pthread *self = THREAD_SELF;
 280
 281       /* Store old info.  */
 282       unwind_buf.priv.data.prev = THREAD_GETMEM (self, cleanup_jmp_buf);
 283       unwind_buf.priv.data.cleanup = THREAD_GETMEM (self, cleanup);
 284
 285       /* Store the new cleanup handler info.  */
 286       THREAD_SETMEM (self, cleanup_jmp_buf, &unwind_buf);
 287
 288       /* Run the program.  */
 289       result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
 290     }
 291   else
 292     {
 293       /* Remove the thread-local data.  */
 294 # ifdef SHARED
 295       PTHFCT_CALL (ptr__nptl_deallocate_tsd, ());
 296 # else
 297       extern void __nptl_deallocate_tsd (void) __attribute ((weak));
 298       __nptl_deallocate_tsd ();
 299 # endif
 300
 301       /* One less thread.  Decrement the counter.  If it is zero we
 302          terminate the entire process.  */
 303       result = 0;
 304 # ifdef SHARED
 305       unsigned int *ptr = __libc_pthread_functions.ptr_nthreads;
 306 #  ifdef PTR_DEMANGLE
 307       PTR_DEMANGLE (ptr);
 308 #  endif
 309 # else
 310       extern unsigned int __nptl_nthreads __attribute ((weak));
 311       unsigned int *const ptr = &__nptl_nthreads;
 312 # endif
 313
 314       if (! atomic_decrement_and_test (ptr))
 315         /* Not much left to do but to exit the thread, not the process.  */
 316         __exit_thread ();
 317     }
 318 #else
 319   /* Nothing fancy, just call the function.  */
 320   result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
 321 #endif
 322
 323   exit (result);
 324 }