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 #include <tls.h>
  31 #ifndef SHARED
  32 # include <dl-osinfo.h>
  33 # ifndef THREAD_SET_STACK_GUARD
  34 /* Only exported for architectures that don't store the stack guard canary
  35    in thread local area.  */
  36 uintptr_t __stack_chk_guard attribute_relro;
  37 # endif
  38 # ifndef  THREAD_SET_POINTER_GUARD
  39 /* Only exported for architectures that don't store the pointer guard
  40    value in thread local area.  */
  41 uintptr_t __pointer_chk_guard_local
  42         attribute_relro attribute_hidden __attribute__ ((nocommon));
  43 # endif
  44 #endif
  45
  46 #ifdef HAVE_PTR_NTHREADS
  47 /* We need atomic operations.  */
  48 # include <atomic.h>
  49 #endif
  50
  51
  52 #ifndef SHARED
  53 # include <link.h>
  54 # include <dl-irel.h>
  55
  56 # ifdef ELF_MACHINE_IRELA
  57 #  define IREL_T        ElfW(Rela)
  58 #  define IPLT_START    __rela_iplt_start
  59 #  define IPLT_END      __rela_iplt_end
  60 #  define IREL          elf_irela
  61 # elif defined ELF_MACHINE_IREL
  62 #  define IREL_T        ElfW(Rel)
  63 #  define IPLT_START    __rel_iplt_start
  64 #  define IPLT_END      __rel_iplt_end
  65 #  define IREL          elf_irel
  66 # endif
  67
  68 static void
  69 apply_irel (void)
  70 {
  71 # ifdef IREL
  72   /* We use weak references for these so that we'll still work with a linker
  73      that doesn't define them.  Such a linker doesn't support IFUNC at all
  74      and so uses won't work, but a statically-linked program that doesn't
  75      use any IFUNC symbols won't have a problem.  */
  76   extern const IREL_T IPLT_START[] __attribute__ ((weak));
  77   extern const IREL_T IPLT_END[] __attribute__ ((weak));
  78   for (const IREL_T *ipltent = IPLT_START; ipltent < IPLT_END; ++ipltent)
  79     IREL (ipltent);
  80 # endif
  81 }
  82 #endif
  83
  84
  85 #ifdef LIBC_START_MAIN
  86 # ifdef LIBC_START_DISABLE_INLINE
  87 #  define STATIC static
  88 # else
  89 #  define STATIC static inline __attribute__ ((always_inline))
  90 # endif
  91 #else
  92 # define STATIC
  93 # define LIBC_START_MAIN __libc_start_main
  94 #endif
  95
  96 #ifdef MAIN_AUXVEC_ARG
  97 /* main gets passed a pointer to the auxiliary.  */
  98 # define MAIN_AUXVEC_DECL       , void *
  99 # define MAIN_AUXVEC_PARAM      , auxvec
 100 #else
 101 # define MAIN_AUXVEC_DECL
 102 # define MAIN_AUXVEC_PARAM
 103 #endif
 104
 105 #ifndef ARCH_INIT_CPU_FEATURES
 106 # define ARCH_INIT_CPU_FEATURES()
 107 #endif
 108
 109 #include <libc-start.h>
 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   ARCH_SETUP_IREL ();
 193
 194   /* The stack guard goes into the TCB, so initialize it early.  */
 195   __libc_setup_tls ();
 196
 197   /* In some architectures, IREL{,A} relocations happen after TLS setup in
 198      order to let IFUNC resolvers benefit from TCB information, e.g. powerpc's
 199      hwcap and platform fields available in the TCB.  */
 200   ARCH_APPLY_IREL ();
 201
 202   /* Set up the stack checker's canary.  */
 203   uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
 204 # ifdef THREAD_SET_STACK_GUARD
 205   THREAD_SET_STACK_GUARD (stack_chk_guard);
 206 # else
 207   __stack_chk_guard = stack_chk_guard;
 208 # endif
 209
 210 # ifdef DL_SYSDEP_OSCHECK
 211   if (!__libc_multiple_libcs)
 212     {
 213       /* This needs to run to initiliaze _dl_osversion before TLS
 214          setup might check it.  */
 215       DL_SYSDEP_OSCHECK (__libc_fatal);
 216     }
 217 # endif
 218
 219   /* Initialize libpthread if linked in.  */
 220   if (__pthread_initialize_minimal != NULL)
 221     __pthread_initialize_minimal ();
 222
 223   /* Set up the pointer guard value.  */
 224   uintptr_t pointer_chk_guard = _dl_setup_pointer_guard (_dl_random,
 225                                                          stack_chk_guard);
 226 # ifdef THREAD_SET_POINTER_GUARD
 227   THREAD_SET_POINTER_GUARD (pointer_chk_guard);
 228 # else
 229   __pointer_chk_guard_local = pointer_chk_guard;
 230 # endif
 231
 232 #endif /* !SHARED  */
 233
 234   /* Register the destructor of the dynamic linker if there is any.  */
 235   if (__glibc_likely (rtld_fini != NULL))
 236     __cxa_atexit ((void (*) (void *)) rtld_fini, NULL, NULL);
 237
 238 #ifndef SHARED
 239   /* Call the initializer of the libc.  This is only needed here if we
 240      are compiling for the static library in which case we haven't
 241      run the constructors in `_dl_start_user'.  */
 242   __libc_init_first (argc, argv, __environ);
 243
 244   /* Register the destructor of the program, if any.  */
 245   if (fini)
 246     __cxa_atexit ((void (*) (void *)) fini, NULL, NULL);
 247
 248   /* Some security at this point.  Prevent starting a SUID binary where
 249      the standard file descriptors are not opened.  We have to do this
 250      only for statically linked applications since otherwise the dynamic
 251      loader did the work already.  */
 252   if (__builtin_expect (__libc_enable_secure, 0))
 253     __libc_check_standard_fds ();
 254 #endif
 255
 256   /* Call the initializer of the program, if any.  */
 257 #ifdef SHARED
 258   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS, 0))
 259     GLRO(dl_debug_printf) ("\ninitialize program: %s\n\n", argv[0]);
 260 #endif
 261   if (init)
 262     (*init) (argc, argv, __environ MAIN_AUXVEC_PARAM);
 263
 264 #ifdef SHARED
 265   /* Auditing checkpoint: we have a new object.  */
 266   if (__glibc_unlikely (GLRO(dl_naudit) > 0))
 267     {
 268       struct audit_ifaces *afct = GLRO(dl_audit);
 269       struct link_map *head = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
 270       for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 271         {
 272           if (afct->preinit != NULL)
 273             afct->preinit (&head->l_audit[cnt].cookie);
 274
 275           afct = afct->next;
 276         }
 277     }
 278 #endif
 279
 280 #ifdef SHARED
 281   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
 282     GLRO(dl_debug_printf) ("\ntransferring control: %s\n\n", argv[0]);
 283 #endif
 284
 285 #ifndef SHARED
 286   _dl_debug_initialize (0, LM_ID_BASE);
 287 #endif
 288 #ifdef HAVE_CLEANUP_JMP_BUF
 289   /* Memory for the cancellation buffer.  */
 290   struct pthread_unwind_buf unwind_buf;
 291
 292   int not_first_call;
 293   not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
 294   if (__glibc_likely (! not_first_call))
 295     {
 296       struct pthread *self = THREAD_SELF;
 297
 298       /* Store old info.  */
 299       unwind_buf.priv.data.prev = THREAD_GETMEM (self, cleanup_jmp_buf);
 300       unwind_buf.priv.data.cleanup = THREAD_GETMEM (self, cleanup);
 301
 302       /* Store the new cleanup handler info.  */
 303       THREAD_SETMEM (self, cleanup_jmp_buf, &unwind_buf);
 304
 305       /* Run the program.  */
 306       result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
 307     }
 308   else
 309     {
 310       /* Remove the thread-local data.  */
 311 # ifdef SHARED
 312       PTHFCT_CALL (ptr__nptl_deallocate_tsd, ());
 313 # else
 314       extern void __nptl_deallocate_tsd (void) __attribute ((weak));
 315       __nptl_deallocate_tsd ();
 316 # endif
 317
 318       /* One less thread.  Decrement the counter.  If it is zero we
 319          terminate the entire process.  */
 320       result = 0;
 321 # ifdef SHARED
 322       unsigned int *ptr = __libc_pthread_functions.ptr_nthreads;
 323 #  ifdef PTR_DEMANGLE
 324       PTR_DEMANGLE (ptr);
 325 #  endif
 326 # else
 327       extern unsigned int __nptl_nthreads __attribute ((weak));
 328       unsigned int *const ptr = &__nptl_nthreads;
 329 # endif
 330
 331       if (! atomic_decrement_and_test (ptr))
 332         /* Not much left to do but to exit the thread, not the process.  */
 333         __exit_thread ();
 334     }
 335 #else
 336   /* Nothing fancy, just call the function.  */
 337   result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
 338 #endif
 339
 340   exit (result);
 341 }