/* Test that stack overflow and SIGSEGV are correctly distinguished.
   Copyright (C) 2002-2021 Free Software Foundation, Inc.

   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 2 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 <https://www.gnu.org/licenses/>.  */

/* Written by Bruno Haible and Eric Blake.  */

#include <config.h>

/* Specification.  */
#include "sigsegv.h"

#include <stdint.h>
#include <stdio.h>
#include <limits.h>

#if HAVE_STACK_OVERFLOW_RECOVERY && HAVE_SIGSEGV_RECOVERY

# if defined _WIN32 && !defined __CYGWIN__
  /* Windows doesn't have sigset_t.  */
  typedef int sigset_t;
#  define sigemptyset(set)
#  define sigprocmask(how,set,oldset)
# endif

# include "mmap-anon-util.h"
# include <stddef.h> /* needed for NULL on SunOS4 */
# include <stdlib.h> /* for abort, exit */
# include <signal.h>
# include <setjmp.h>
# if HAVE_SETRLIMIT
#  include <sys/types.h>
#  include <sys/time.h>
#  include <sys/resource.h>
# endif
# include "altstack-util.h"

static jmp_buf mainloop;
static sigset_t mainsigset;

static volatile int pass = 0;
static uintptr_t page;
static volatile int *null_pointer_to_volatile_int /* = NULL */;

static void
stackoverflow_handler_continuation (void *arg1, void *arg2, void *arg3)
{
  int arg = (int) (long) arg1;
  longjmp (mainloop, arg);
}

static void
stackoverflow_handler (int emergency, stackoverflow_context_t scp)
{
  pass++;
  if (pass <= 2)
    printf ("Stack overflow %d caught.\n", pass);
  else
    {
      printf ("Segmentation violation misdetected as stack overflow.\n");
      exit (1);
    }
  sigprocmask (SIG_SETMASK, &mainsigset, NULL);
  sigsegv_leave_handler (stackoverflow_handler_continuation,
                         (void *) (long) (emergency ? -1 : pass), NULL, NULL);
}

static int
sigsegv_handler (void *address, int emergency)
{
  /* This test is necessary to distinguish stack overflow and SIGSEGV.  */
  if (!emergency)
    return 0;

  pass++;
  if (pass <= 2)
    {
      printf ("Stack overflow %d missed.\n", pass);
      exit (1);
    }
  else
    printf ("Segmentation violation correctly detected.\n");
  sigprocmask (SIG_SETMASK, &mainsigset, NULL);
  return sigsegv_leave_handler (stackoverflow_handler_continuation,
                                (void *) (long) pass, NULL, NULL);
}

static volatile int *
recurse_1 (int n, volatile int *p)
{
  if (n < INT_MAX)
    *recurse_1 (n + 1, p) += n;
  return p;
}

static int
recurse (volatile int n)
{
  return *recurse_1 (n, &n);
}

int
main ()
{
  int prot_unwritable;
  void *p;
  sigset_t emptyset;

# if HAVE_SETRLIMIT && defined RLIMIT_STACK
  /* Before starting the endless recursion, try to be friendly to the user's
     machine.  On some Linux 2.2.x systems, there is no stack limit for user
     processes at all.  We don't want to kill such systems.  */
  struct rlimit rl;
  rl.rlim_cur = rl.rlim_max = 0x100000; /* 1 MB */
  setrlimit (RLIMIT_STACK, &rl);
# endif

  /* Prepare the storage for the alternate stack.  */
  prepare_alternate_stack ();

  /* Install the stack overflow handler.  */
  if (stackoverflow_install_handler (&stackoverflow_handler,
                                     mystack, MYSTACK_SIZE)
      < 0)
    exit (2);

  /* Preparations.  */
# if !HAVE_MAP_ANONYMOUS
  zero_fd = open ("/dev/zero", O_RDONLY, 0644);
# endif

# if defined __linux__ && defined __sparc__
  /* On Linux 2.6.26/SPARC64, PROT_READ has the same effect as
     PROT_READ | PROT_WRITE.  */
  prot_unwritable = PROT_NONE;
# else
  prot_unwritable = PROT_READ;
# endif

  /* Setup some mmaped memory.  */
  p = mmap_zeromap ((void *) 0x12340000, 0x4000);
  if (p == (void *)(-1))
    {
      fprintf (stderr, "mmap_zeromap failed.\n");
      exit (2);
    }
  page = (uintptr_t) p;

  /* Make it read-only.  */
  if (mprotect ((void *) page, 0x4000, prot_unwritable) < 0)
    {
      fprintf (stderr, "mprotect failed.\n");
      exit (2);
    }

  /* Install the SIGSEGV handler.  */
  if (sigsegv_install_handler (&sigsegv_handler) < 0)
    exit (2);

  /* Save the current signal mask.  */
  sigemptyset (&emptyset);
  sigprocmask (SIG_BLOCK, &emptyset, &mainsigset);

  /* Provoke two stack overflows in a row.  */
  switch (setjmp (mainloop))
    {
    case -1:
      printf ("emergency exit\n"); exit (1);
    case 0: case 1:
      printf ("Starting recursion pass %d.\n", pass + 1);
      recurse (0);
      printf ("no endless recursion?!\n"); exit (1);
    case 2:
      *(volatile int *) (page + 0x678) = 42;
      break;
    case 3:
      *null_pointer_to_volatile_int = 42;
      break;
    case 4:
      break;
    default:
      abort ();
    }

  /* Validate that the alternate stack did not overflow.  */
  check_alternate_stack_no_overflow ();

  printf ("Test passed.\n");
  exit (0);
}

#else

int
main ()
{
  return 77;
}

#endif
