sysdeps/unix/sysv/linux/dl-execstack.c

   1 /* Stack executability handling for GNU dynamic linker.  Linux version.
   2    Copyright (C) 2003-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   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 <ldsodefs.h>
  20 #include <sys/mman.h>
  21 #include <errno.h>
  22 #include <libintl.h>
  23 #include <stdbool.h>
  24 #include <stackinfo.h>
  25 #include <caller.h>
  26 #include <sysdep.h>
  27
  28 #include <kernel-features.h>
  29
  30
  31 extern int __stack_prot attribute_relro attribute_hidden;
  32
  33
  34 int
  35 internal_function
  36 _dl_make_stack_executable (void **stack_endp)
  37 {
  38   /* This gives us the highest/lowest page that needs to be changed.  */
  39   uintptr_t page = ((uintptr_t) *stack_endp
  40                     & -(intptr_t) GLRO(dl_pagesize));
  41   int result = 0;
  42
  43   /* Challenge the caller.  */
  44   if (__builtin_expect (__check_caller (RETURN_ADDRESS (0),
  45                                         allow_ldso|allow_libpthread) != 0, 0)
  46       || __builtin_expect (*stack_endp != __libc_stack_end, 0))
  47     return EPERM;
  48
  49   if (__builtin_expect (__mprotect ((void *) page, GLRO(dl_pagesize),
  50                                     __stack_prot) == 0, 1))
  51     goto return_success;
  52   result = errno;
  53   goto out;
  54
  55  return_success:
  56   /* Clear the address.  */
  57   *stack_endp = NULL;
  58
  59   /* Remember that we changed the permission.  */
  60   GL(dl_stack_flags) |= PF_X;
  61
  62  out:
  63 #ifdef check_consistency
  64   check_consistency ();
  65 #endif
  66
  67   return result;
  68 }
  69 rtld_hidden_def (_dl_make_stack_executable)