#define _GNU_SOURCE
#include <sys/ptrace.h>
#include <linux/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/syscall.h> 
#include <signal.h>

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

static void ptrace_child(void)
{
	if (ptrace(PTRACE_TRACEME, 0, 0, 0) < 0) {
		fprintf(stderr, "%s: PTRACE_TRACEME failed: %m\n", __func__);
		raise(SIGKILL);
	}
	raise(SIGSTOP);

	getpid();

	exit(0);
}

static int start_ptraced_child(void)
{
	int pid, ret, status;

	pid = fork();
	if (pid == 0)
		ptrace_child();
	else if (pid < 0)
		fprintf(stderr, "%s: fork() failed: %m\n", __func__);

	ret = waitpid(pid, &status, WUNTRACED);
	if (ret < 0)
		fprintf(stderr, "%s: wait() failed: %m\n", __func__);
	if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
		fprintf(stderr, "%s: expected SIGSTOP, got status:%#x\n", __func__, status);

	return pid;
}

static void stop_ptraced_child(int pid)
{
	if (ptrace(PTRACE_CONT, pid, 0, 0) < 0) {
		fprintf(stderr, "%s: PTRACE_CONT failed: %m\n", __func__);
		return;
	}

	waitpid(pid, NULL, 0);
}

int main(void)
{
	int pid, n, status, step_count = 0;

	pid = start_ptraced_child();

	if ((ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0))
		fprintf(stderr, "%s: PTRACE_OLDSETOPTIONS failed: %m\n", __func__);

	while (1) {
		if (ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
			exit(1);

		n = waitpid(pid, &status, WUNTRACED);
		if (n < 0)
			fprintf(stderr, "%s: wait() failed: %m\n", __func__);


		if (WIFSTOPPED(status) &&
		    (WSTOPSIG(status) == (SIGTRAP|0x80))) {
			if (!step_count) {
				fprintf(stderr, "SYSEMU_SINGLESTEP doesn't singlestep");
				exit(1);
			}

			/* syscall */

			break;
		} else if (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGTRAP)) {
			/* single step */
			step_count++;
		} else {
			fprintf(stderr, "expected SIGTRAP or (SIGTRAP | 0x80), got status = %d\n", status);
			exit(1);
		}
		step_count++;
	}
	stop_ptraced_child(pid);

	return 0;
}