text: /* Copyright (C) 2001-2020 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
     <https://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;
  }
  