#include <sys/types.h>
#include <sys/ptrace.h>
#include <sys/wait.h>

#include <assert.h>
#include <signal.h>
#include <stdio.h>
#include <unistd.h>

int
main(void)
{
	int status;
	pid_t pid;
	struct reg regs;
	struct ptrace_lwpinfo lwpinfo;

	if ((pid = fork()) < 0) {
		perror("fork");
		return 1;
	}
	else if (!pid) { /* child */
		if (ptrace(PT_TRACE_ME, 0, NULL, 0) < 0) {
			perror("PT_TRACE_ME");
			_exit(1);
		}
		raise(SIGTRAP);
		for (;;) {
			getpid();
		}
	}
	else { /* parent */
		for (;;) {
			waitpid(pid, &status, 0);
			printf("status %x\n", status);
			assert(WIFSTOPPED(status));
			assert(WSTOPSIG(status) == SIGTRAP);

			if (ptrace(PT_GETREGS, pid, &regs, 0) < 0) {
				perror("PT_GETREGS");
				ptrace(PT_KILL, pid, NULL, 0);
				return (2);
			}
			printf("eip %p\n", regs.r_eip);

			if (ptrace(PT_STEP, pid, (caddr_t)1, 0) < 0) {
				perror("PT_STEP");
				ptrace(PT_KILL, pid, NULL, 0);
				return (2);
			}
		}
	}
}