#include <stdio.h>
#include <signal.h>
#include <sched.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/mman.h>
#include <sys/ptrace.h>
#include <asm/ptrace.h>
#include <unistd.h>
#include <asm/unistd.h>
#include <errno.h>

char childstack[ 8*1024];


int my_getpid()
{
	long res;
	__asm__ volatile ("	int $0x80\n\t"
				: "=a" (res)
				: "0" (__NR_getpid));
	return res;
}


void
parent_fn( pid_t child)
{
	int status;

	printf("Parent: childs PID is %d\n", child);

	if ( waitpid( child, &status, 0) != child ) {
			fprintf( stderr, "Parent: ");
			perror("waitpid");
			exit(1);
	}
	if ( !WIFSTOPPED(status) || WSTOPSIG(status) != SIGTRAP ) {
		printf("Unexpected status %04x received\n", status);
		exit(1);
	}

	*(char *)0x12345678 = 'A';
}


int
child_fn( void * unused)
{
	printf("Child: my PID is %d\n", my_getpid());

	if ( ptrace( PTRACE_TRACEME, 0, (void *)0, (void *)0) ) {
		fprintf( stderr, "        Child: ");
		perror("ptrace( PTRACE_TRACEME, 0, 0, 0)");
		exit(1);
	}
	kill( my_getpid(), SIGTRAP);

	printf("You should never read this text!!!!\n");

	return 0;
}


int
main( void)
{
	pid_t child;

	printf("Parent: my PID is %d\n", my_getpid());

	child = clone( child_fn, childstack+8*1024-4, CLONE_VM|SIGCHLD, (void *)NULL);

	if ( child < 0 ) {
		perror("clone");
		exit(1);
	}
	parent_fn( child);

	return 0;
}