csu/libc-start.c

   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
  28 extern void __libc_init_first (int argc, char **argv, char **envp);
  29
  30 extern 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.  */
  38 uintptr_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.  */
  43 uintptr_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
  70 static void
  71 apply_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 STATIC int LIBC_START_MAIN (int (*main) (int, char **, char **
 112                                          MAIN_AUXVEC_DECL),
 113                             int argc,
 114                             char **argv,
 115 #ifdef LIBC_START_MAIN_AUXVEC_ARG
 116                             ElfW(auxv_t) *auxvec,
 117 #endif
 118                             __typeof (main) init,
 119                             void (*fini) (void),
 120                             void (*rtld_fini) (void),
 121                             void *stack_end)
 122      __attribute__ ((noreturn));
 123
 124
 125 /* Note: the fini parameter is ignored here for shared library.  It
 126    is registered with __cxa_atexit.  This had the disadvantage that
 127    finalizers were called in more than one place.  */
 128 STATIC int
 129 LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
 130                  int argc, char **argv,
 131 #ifdef LIBC_START_MAIN_AUXVEC_ARG
 132                  ElfW(auxv_t) *auxvec,
 133 #endif
 134                  __typeof (main) init,
 135                  void (*fini) (void),
 136                  void (*rtld_fini) (void), void *stack_end)
 137 {
 138   /* Result of the 'main' function.  */
 139   int result;
 140
 141   __libc_multiple_libcs = &_dl_starting_up && !_dl_starting_up;
 142
 143 #ifndef SHARED
 144   char **ev = &argv[argc + 1];
 145
 146   __environ = ev;
 147
 148   /* Store the lowest stack address.  This is done in ld.so if this is
 149      the code for the DSO.  */
 150   __libc_stack_end = stack_end;
 151
 152 # ifdef HAVE_AUX_VECTOR
 153   /* First process the auxiliary vector since we need to find the
 154      program header to locate an eventually present PT_TLS entry.  */
 155 #  ifndef LIBC_START_MAIN_AUXVEC_ARG
 156   ElfW(auxv_t) *auxvec;
 157   {
 158     char **evp = ev;
 159     while (*evp++ != NULL)
 160       ;
 161     auxvec = (ElfW(auxv_t) *) evp;
 162   }
 163 #  endif
 164   _dl_aux_init (auxvec);
 165   if (GL(dl_phdr) == NULL)
 166 # endif
 167     {
 168       /* Starting from binutils-2.23, the linker will define the
 169          magic symbol __ehdr_start to point to our own ELF header
 170          if it is visible in a segment that also includes the phdrs.
 171          So we can set up _dl_phdr and _dl_phnum even without any
 172          information from auxv.  */
 173
 174       extern const ElfW(Ehdr) __ehdr_start
 175         __attribute__ ((weak, visibility ("hidden")));
 176       if (&__ehdr_start != NULL)
 177         {
 178           assert (__ehdr_start.e_phentsize == sizeof *GL(dl_phdr));
 179           GL(dl_phdr) = (const void *) &__ehdr_start + __ehdr_start.e_phoff;
 180           GL(dl_phnum) = __ehdr_start.e_phnum;
 181         }
 182     }
 183
 184   /* Initialize very early so that tunables can use it.  */
 185   __libc_init_secure ();
 186
 187   __tunables_init (__environ);
 188
 189   ARCH_INIT_CPU_FEATURES ();
 190
 191   /* Perform IREL{,A} relocations.  */
 192   apply_irel ();
 193
 194   /* The stack guard goes into the TCB, so initialize it early.  */
 195   __libc_setup_tls ();
 196
 197   /* Set up the stack checker's canary.  */
 198   uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
 199 # ifdef THREAD_SET_STACK_GUARD
 200   THREAD_SET_STACK_GUARD (stack_chk_guard);
 201 # else
 202   __stack_chk_guard = stack_chk_guard;
 203 # endif
 204
 205 # ifdef DL_SYSDEP_OSCHECK
 206   if (!__libc_multiple_libcs)
 207     {
 208       /* This needs to run to initiliaze _dl_osversion before TLS
 209          setup might check it.  */
 210       DL_SYSDEP_OSCHECK (__libc_fatal);
 211     }
 212 # endif
 213
 214   /* Initialize libpthread if linked in.  */
 215   if (__pthread_initialize_minimal != NULL)
 216     __pthread_initialize_minimal ();
 217
 218   /* Set up the pointer guard value.  */
 219   uintptr_t pointer_chk_guard = _dl_setup_pointer_guard (_dl_random,
 220                                                          stack_chk_guard);
 221 # ifdef THREAD_SET_POINTER_GUARD
 222   THREAD_SET_POINTER_GUARD (pointer_chk_guard);
 223 # else
 224   __pointer_chk_guard_local = pointer_chk_guard;
 225 # endif
 226
 227 #endif
 228
 229   /* Register the destructor of the dynamic linker if there is any.  */
 230   if (__glibc_likely (rtld_fini != NULL))
 231     __cxa_atexit ((void (*) (void *)) rtld_fini, NULL, NULL);
 232
 233 #ifndef SHARED
 234   /* Call the initializer of the libc.  This is only needed here if we
 235      are compiling for the static library in which case we haven't
 236      run the constructors in `_dl_start_user'.  */
 237   __libc_init_first (argc, argv, __environ);
 238
 239   /* Register the destructor of the program, if any.  */
 240   if (fini)
 241     __cxa_atexit ((void (*) (void *)) fini, NULL, NULL);
 242
 243   /* Some security at this point.  Prevent starting a SUID binary where
 244      the standard file descriptors are not opened.  We have to do this
 245      only for statically linked applications since otherwise the dynamic
 246      loader did the work already.  */
 247   if (__builtin_expect (__libc_enable_secure, 0))
 248     __libc_check_standard_fds ();
 249 #endif
 250
 251   /* Call the initializer of the program, if any.  */
 252 #ifdef SHARED
 253   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS, 0))
 254     GLRO(dl_debug_printf) ("\ninitialize program: %s\n\n", argv[0]);
 255 #endif
 256   if (init)
 257     (*init) (argc, argv, __environ MAIN_AUXVEC_PARAM);
 258
 259 #ifdef SHARED
 260   /* Auditing checkpoint: we have a new object.  */
 261   if (__glibc_unlikely (GLRO(dl_naudit) > 0))
 262     {
 263       struct audit_ifaces *afct = GLRO(dl_audit);
 264       struct link_map *head = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
 265       for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 266         {
 267           if (afct->preinit != NULL)
 268             afct->preinit (&head->l_audit[cnt].cookie);
 269
 270           afct = afct->next;
 271         }
 272     }
 273 #endif
 274
 275 #ifdef SHARED
 276   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
 277     GLRO(dl_debug_printf) ("\ntransferring control: %s\n\n", argv[0]);
 278 #endif
 279
 280 #ifndef SHARED
 281   _dl_debug_initialize (0, LM_ID_BASE);
 282 #endif
 283 #ifdef HAVE_CLEANUP_JMP_BUF
 284   /* Memory for the cancellation buffer.  */
 285   struct pthread_unwind_buf unwind_buf;
 286
 287   int not_first_call;
 288   not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
 289   if (__glibc_likely (! not_first_call))
 290     {
 291       struct pthread *self = THREAD_SELF;
 292
 293       /* Store old info.  */
 294       unwind_buf.priv.data.prev = THREAD_GETMEM (self, cleanup_jmp_buf);
 295       unwind_buf.priv.data.cleanup = THREAD_GETMEM (self, cleanup);
 296
 297       /* Store the new cleanup handler info.  */
 298       THREAD_SETMEM (self, cleanup_jmp_buf, &unwind_buf);
 299
 300       /* Run the program.  */
 301       result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
 302     }
 303   else
 304     {
 305       /* Remove the thread-local data.  */
 306 # ifdef SHARED
 307       PTHFCT_CALL (ptr__nptl_deallocate_tsd, ());
 308 # else
 309       extern void __nptl_deallocate_tsd (void) __attribute ((weak));
 310       __nptl_deallocate_tsd ();
 311 # endif
 312
 313       /* One less thread.  Decrement the counter.  If it is zero we
 314          terminate the entire process.  */
 315       result = 0;
 316 # ifdef SHARED
 317       unsigned int *ptr = __libc_pthread_functions.ptr_nthreads;
 318 #  ifdef PTR_DEMANGLE
 319       PTR_DEMANGLE (ptr);
 320 #  endif
 321 # else
 322       extern unsigned int __nptl_nthreads __attribute ((weak));
 323       unsigned int *const ptr = &__nptl_nthreads;
 324 # endif
 325
 326       if (! atomic_decrement_and_test (ptr))
 327         /* Not much left to do but to exit the thread, not the process.  */
 328         __exit_thread ();
 329     }
 330 #else
 331   /* Nothing fancy, just call the function.  */
 332   result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
 333 #endif
 334
 335   exit (result);
 336 }