nptl/libc_pthread_init.c

   1 /* Copyright (C) 2002-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <unistd.h>
  20 #include <list.h>
  21 #include <fork.h>
  22 #include <dl-sysdep.h>
  23 #include <tls.h>
  24 #include <string.h>
  25 #include <pthreadP.h>
  26 #include <libc-lock.h>
  27 #include <sysdep.h>
  28 #include <ldsodefs.h>
  29
  30
  31 unsigned long int *__fork_generation_pointer;
  32
  33
  34 #ifdef TLS_MULTIPLE_THREADS_IN_TCB
  35 void
  36 #else
  37 extern int __libc_multiple_threads attribute_hidden;
  38
  39 int *
  40 #endif
  41 internal_function
  42 __libc_pthread_init (unsigned long int *ptr, void (*reclaim) (void),
  43                      const struct pthread_functions *functions)
  44 {
  45   /* Remember the pointer to the generation counter in libpthread.  */
  46   __fork_generation_pointer = ptr;
  47
  48   /* Called by a child after fork.  */
  49   __register_atfork (NULL, NULL, reclaim, NULL);
  50
  51 #ifdef SHARED
  52   /* Copy the function pointers into an array in libc.  This enables
  53      access with just one memory reference but moreso, it prevents
  54      hijacking the function pointers with just one pointer change.  We
  55      "encrypt" the function pointers since we cannot write-protect the
  56      array easily enough.  */
  57   union ptrhack
  58   {
  59     struct pthread_functions pf;
  60 # define NPTRS (sizeof (struct pthread_functions) / sizeof (void *))
  61     void *parr[NPTRS];
  62   } __attribute__ ((may_alias)) const *src;
  63   union ptrhack *dest;
  64
  65   src = (const void *) functions;
  66   dest = (void *) &__libc_pthread_functions;
  67
  68   for (size_t cnt = 0; cnt < NPTRS; ++cnt)
  69     {
  70       void *p = src->parr[cnt];
  71       PTR_MANGLE (p);
  72       dest->parr[cnt] = p;
  73     }
  74   __libc_pthread_functions_init = 1;
  75 #endif
  76
  77 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
  78   return &__libc_multiple_threads;
  79 #endif
  80 }
  81
  82 #ifdef SHARED
  83 libc_freeres_fn (freeres_libptread)
  84 {
  85   if (__libc_pthread_functions_init)
  86     PTHFCT_CALL (ptr_freeres, ());
  87 }
  88 #endif