File: tst-setcontext9.c

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/* Check setcontext on the context from makecontext.
   Copyright (C) 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 <stdio.h>
#include <stdlib.h>
#include <ucontext.h>
#include <unistd.h>
#include <stdatomic.h>

static ucontext_t ctx[5];
static atomic_int done;

static void
__attribute__((noinline, noclone))
f2 (void)
{
  done++;
  puts ("swap contexts in f2");
  if (swapcontext (&ctx[4], &ctx[2]) != 0)
    {
      printf ("%s: setcontext: %m\n", __FUNCTION__);
      exit (EXIT_FAILURE);
    }
  puts ("end f2");
  exit (done == 2 ? EXIT_SUCCESS : EXIT_FAILURE);
}

static void
f1b (void)
{
  if (done)
    {
      puts ("set context in f1b");
      if (setcontext (&ctx[3]) != 0)
	{
	  printf ("%s: setcontext: %m\n", __FUNCTION__);
	  exit (EXIT_FAILURE);
	}
    }
  exit (EXIT_FAILURE);
}

static void
f1a (void)
{
  static char st2[32768];
  puts ("start f1a");
  if (getcontext (&ctx[2]) != 0)
    {
      printf ("%s: getcontext: %m\n", __FUNCTION__);
      exit (EXIT_FAILURE);
    }
  ctx[2].uc_stack.ss_sp = st2;
  ctx[2].uc_stack.ss_size = sizeof st2;
  ctx[2].uc_link = &ctx[0];
  makecontext (&ctx[2], (void (*) (void)) f1b, 0);
  f2 ();
}

/* The execution path through the test looks like this:
   do_test (call)
   -> "making contexts"
   -> "swap contexts"
   f1a (via swapcontext to ctx[1], with alternate stack)
   -> "start f1a"
   f2 (call)
   -> "swap contexts in f2"
   f1b (via swapcontext to ctx[2], with alternate stack)
   -> "set context in f1b"
   do_test (via setcontext to ctx[3], main stack)
   -> "setcontext"
   f2 (via setcontext to ctx[4], with alternate stack)
   -> "end f2"

   We must use an alternate stack for f1b, because if we don't then the
   result of executing an earlier caller may overwrite registers
   spilled to the stack in f2.  */
static int
do_test (void)
{
  static char st1[32768];
  puts ("making contexts");
  if (getcontext (&ctx[0]) != 0)
    {
      printf ("%s: getcontext: %m\n", __FUNCTION__);
      exit (EXIT_FAILURE);
    }
  if (getcontext (&ctx[1]) != 0)
    {
      printf ("%s: getcontext: %m\n", __FUNCTION__);
      exit (EXIT_FAILURE);
    }
  ctx[1].uc_stack.ss_sp = st1;
  ctx[1].uc_stack.ss_size = sizeof st1;
  ctx[1].uc_link = &ctx[0];
  makecontext (&ctx[1], (void (*) (void)) f1a, 0);
  puts ("swap contexts");
  if (swapcontext (&ctx[3], &ctx[1]) != 0)
    {
      printf ("%s: setcontext: %m\n", __FUNCTION__);
      exit (EXIT_FAILURE);
    }
  if (done != 1)
    exit (EXIT_FAILURE);
  done++;
  puts ("set context");
  if (setcontext (&ctx[4]) != 0)
    {
      printf ("%s: setcontext: %m\n", __FUNCTION__);
      exit (EXIT_FAILURE);
    }
  exit (EXIT_FAILURE);
}

#include <support/test-driver.c>