/* Copyright (C) 2001-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <errno.h>

#include <signal.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <ucontext.h>

#include <unistd.h>

static ucontext_t ctx[3];

static int was_in_f1;

static int was_in_f2;

static char st2[32768];

static void

f1 (int a0, int a1, int a2, int a3)

{

  printf ("start f1(a0=%x,a1=%x,a2=%x,a3=%x)\n", a0, a1, a2, a3);

  if (a0 != 1 || a1 != 2 || a2 != 3 || a3 != -4)

    {

      puts ("arg mismatch");

      exit (-1);

    }

  if (swapcontext (&ctx[1], &ctx[2]) != 0)

    {

      printf ("%s: swapcontext: %m\n", __FUNCTION__);

      exit (1);

    }

  puts ("finish f1");

  was_in_f1 = 1;

}

static void

f2 (void)

{

  char on_stack[1];

  puts ("start f2");

  printf ("&on_stack=%p\n", on_stack);

  if (on_stack < st2 || on_stack >= st2 + sizeof (st2))

    {

      printf ("%s: memory stack is not where it belongs!", __FUNCTION__);

      exit (1);

    }

  if (swapcontext (&ctx[2], &ctx[1]) != 0)

    {

      printf ("%s: swapcontext: %m\n", __FUNCTION__);

      exit (1);

    }

  puts ("finish f2");

  was_in_f2 = 1;

}

void

test_stack (volatile int a, volatile int b,

	    volatile int c, volatile int d)

{

  volatile int e = 5;

  volatile int f = 6;

  ucontext_t uc;

  /* Test for cases where getcontext is clobbering the callers

     stack, including parameters.  */

  getcontext (&uc);

  if (a != 1)

    {

      printf ("%s: getcontext clobbers parm a\n", __FUNCTION__);

      exit (1);

    }

  if (b != 2)

    {

      printf ("%s: getcontext clobbers parm b\n", __FUNCTION__);

      exit (1);

    }

  if (c != 3)

    {

      printf ("%s: getcontext clobbers parm c\n", __FUNCTION__);

      exit (1);

    }

  if (d != 4)

    {

      printf ("%s: getcontext clobbers parm d\n", __FUNCTION__);

      exit (1);

    }

  if (e != 5)

    {

      printf ("%s: getcontext clobbers varible e\n", __FUNCTION__);

      exit (1);

    }

  if (f != 6)

    {

      printf ("%s: getcontext clobbers variable f\n", __FUNCTION__);

      exit (1);

    }

}

volatile int global;

static int back_in_main;

static void

check_called (void)

{

  if (back_in_main == 0)

    {

      puts ("program did not reach main again");

      _exit (1);

    }

}

int

main (void)

{

  atexit (check_called);

  char st1[32768];

  stack_t stack_before, stack_after;

  sigaltstack (NULL, &stack_before);

  puts ("making contexts");

  if (getcontext (&ctx[1]) != 0)

    {

      if (errno == ENOSYS)

	{

	  back_in_main = 1;

	  exit (0);

	}

      printf ("%s: getcontext: %m\n", __FUNCTION__);

      exit (1);

    }

  test_stack (1, 2, 3, 4);

  /* Play some tricks with this context.  */

  if (++global == 1)

    if (setcontext (&ctx[1]) != 0)

      {

	printf ("%s: setcontext: %m\n", __FUNCTION__);

	exit (1);

      }

  if (global != 2)

    {

      printf ("%s: 'global' not incremented twice\n", __FUNCTION__);

      exit (1);

    }

  ctx[1].uc_stack.ss_sp = st1;

  ctx[1].uc_stack.ss_size = sizeof st1;

  ctx[1].uc_link = &ctx[0];

  {

    ucontext_t tempctx = ctx[1];

    makecontext (&ctx[1], (void (*) (void)) f1, 4, 1, 2, 3, -4);

    /* Without this check, a stub makecontext can make us spin forever.  */

    if (memcmp (&tempctx, &ctx[1], sizeof ctx[1]) == 0)

      {

	puts ("makecontext was a no-op, presuming not implemented");

	return 0;

      }

  }

  if (getcontext (&ctx[2]) != 0)

    {

      printf ("%s: second getcontext: %m\n", __FUNCTION__);

      exit (1);

    }

  ctx[2].uc_stack.ss_sp = st2;

  ctx[2].uc_stack.ss_size = sizeof st2;

  ctx[2].uc_link = &ctx[1];

  makecontext (&ctx[2], f2, 0);

  puts ("swapping contexts");

  if (swapcontext (&ctx[0], &ctx[2]) != 0)

    {

      printf ("%s: swapcontext: %m\n", __FUNCTION__);

      exit (1);

    }

  puts ("back at main program");

  back_in_main = 1;

  sigaltstack (NULL, &stack_after);

  if (was_in_f1 == 0)

    {

      puts ("didn't reach f1");

      exit (1);

    }

  if (was_in_f2 == 0)

    {

      puts ("didn't reach f2");

      exit (1);

    }

  /* Check sigaltstack state is not clobbered as in BZ #16629.  */

  if (stack_before.ss_sp != stack_after.ss_sp)

    {

      printf ("stack ss_sp mismatch: %p %p\n",

	      stack_before.ss_sp, stack_after.ss_sp);

      exit (1);

    }

  if (stack_before.ss_size != stack_after.ss_size)

    {

      printf ("stack ss_size mismatch: %zd %zd\n",

	      stack_before.ss_size, stack_after.ss_size);

      exit (1);

    }

  puts ("test succeeded");

  return 0;

}