/* Temporarily install an alternate signal stack

  Copyright (C) 2019-2024 Free Software Foundation, Inc.

  This file is part of GDB.

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#ifndef GDBSUPPORT_ALT_STACK_H
#define GDBSUPPORT_ALT_STACK_H

#include <signal.h>

namespace gdb
{

/* Try to set up an alternate signal stack for SIGSEGV handlers.
  This allows us to handle SIGSEGV signals generated when the
  normal process stack is exhausted.  If this stack is not set
  up (sigaltstack is unavailable or fails) and a SIGSEGV is
  generated when the normal stack is exhausted then the program
  will behave as though no SIGSEGV handler was installed.  */
class alternate_signal_stack
{
public:
 alternate_signal_stack ()
 {
#ifdef HAVE_SIGALTSTACK
   m_stack.reset ((char *) xmalloc (SIGSTKSZ));

   stack_t stack;
   stack.ss_sp = m_stack.get ();
   stack.ss_size = SIGSTKSZ;
   stack.ss_flags = 0;

   sigaltstack (&stack, &m_old_stack);
#endif
 }

 ~alternate_signal_stack ()
 {
#ifdef HAVE_SIGALTSTACK
   sigaltstack (&m_old_stack, nullptr);
#endif
 }

 DISABLE_COPY_AND_ASSIGN (alternate_signal_stack);

private:

#ifdef HAVE_SIGALTSTACK
 gdb::unique_xmalloc_ptr<char> m_stack;
 stack_t m_old_stack;
#endif
};

}

#endif /* GDBSUPPORT_ALT_STACK_H */