gdbsupport/alt-stack.h

   1 /* Temporarily install an alternate signal stack
   2
   3    Copyright (C) 2019-2023 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef GDBSUPPORT_ALT_STACK_H
  21 #define GDBSUPPORT_ALT_STACK_H
  22
  23 #include <signal.h>
  24
  25 namespace gdb
  26 {
  27
  28 /* Try to set up an alternate signal stack for SIGSEGV handlers.
  29    This allows us to handle SIGSEGV signals generated when the
  30    normal process stack is exhausted.  If this stack is not set
  31    up (sigaltstack is unavailable or fails) and a SIGSEGV is
  32    generated when the normal stack is exhausted then the program
  33    will behave as though no SIGSEGV handler was installed.  */
  34 class alternate_signal_stack
  35 {
  36 public:
  37   alternate_signal_stack ()
  38   {
  39 #ifdef HAVE_SIGALTSTACK
  40     m_stack.reset ((char *) xmalloc (SIGSTKSZ));
  41
  42     stack_t stack;
  43     stack.ss_sp = m_stack.get ();
  44     stack.ss_size = SIGSTKSZ;
  45     stack.ss_flags = 0;
  46
  47     sigaltstack (&stack, &m_old_stack);
  48 #endif
  49   }
  50
  51   ~alternate_signal_stack ()
  52   {
  53 #ifdef HAVE_SIGALTSTACK
  54     sigaltstack (&m_old_stack, nullptr);
  55 #endif
  56   }
  57
  58   DISABLE_COPY_AND_ASSIGN (alternate_signal_stack);
  59
  60 private:
  61
  62 #ifdef HAVE_SIGALTSTACK
  63   gdb::unique_xmalloc_ptr<char> m_stack;
  64   stack_t m_old_stack;
  65 #endif
  66 };
  67
  68 }
  69
  70 #endif /* GDBSUPPORT_ALT_STACK_H */