support/xsigstack.c

   1 /* sigaltstack wrappers.
   2    Copyright (C) 2019-2022 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <support/xsignal.h>
  20 #include <support/support.h>
  21 #include <support/xunistd.h>
  22 #include <support/check.h>
  23
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <sys/mman.h>
  27 #include <sys/param.h> /* roundup, MAX */
  28
  29 #ifndef MAP_NORESERVE
  30 # define MAP_NORESERVE 0
  31 #endif
  32 #ifndef MAP_STACK
  33 # define MAP_STACK 0
  34 #endif
  35
  36 /* The "cookie" returned by xalloc_sigstack points to one of these
  37    structures.  */
  38 struct sigstack_desc
  39 {
  40   struct support_stack stack;
  41   stack_t alt_stack; /* The address and size of the stack itself.  */
  42   stack_t old_stack; /* The previous signal stack.  */
  43 };
  44
  45 void *
  46 xalloc_sigstack (size_t size)
  47 {
  48   struct sigstack_desc *desc = xmalloc (sizeof (struct sigstack_desc));
  49   desc->stack = support_stack_alloc (size);
  50   desc->alt_stack.ss_sp    = desc->stack.stack;
  51   desc->alt_stack.ss_flags = 0;
  52   desc->alt_stack.ss_size  = desc->stack.size;
  53
  54   if (sigaltstack (&desc->alt_stack, &desc->old_stack))
  55     FAIL_EXIT1 ("sigaltstack (new stack: sp=%p, size=%zu, flags=%u): %m\n",
  56                 desc->alt_stack.ss_sp, desc->alt_stack.ss_size,
  57                 desc->alt_stack.ss_flags);
  58
  59   return desc;
  60 }
  61
  62 void
  63 xfree_sigstack (void *stack)
  64 {
  65   struct sigstack_desc *desc = stack;
  66
  67   if (sigaltstack (&desc->old_stack, 0))
  68     FAIL_EXIT1 ("sigaltstack (restore old stack: sp=%p, size=%zu, flags=%u): "
  69                 "%m\n", desc->old_stack.ss_sp, desc->old_stack.ss_size,
  70                 desc->old_stack.ss_flags);
  71   support_stack_free (&desc->stack);
  72   free (desc);
  73 }
  74
  75 void
  76 xget_sigstack_location (const void *stack, unsigned char **addrp, size_t *sizep)
  77 {
  78   const struct sigstack_desc *desc = stack;
  79   *addrp = desc->alt_stack.ss_sp;
  80   *sizep = desc->alt_stack.ss_size;
  81 }