Ptrace child process without calling exec()

ptrace_without_exec.c

/* 
 * ptrace_without_exec: Ptrace child process without calling exec()
 *
 * Compile using:
 *     gcc -o ptrace_without_exec ptrace_without_exec.c -ggdb -Wall
 *
 * Ben Cohen, May 2018.
 */

#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>

long some_value = 0;

int main(int argc, char **argv)
{
	pid_t child_pid = fork();
	if (child_pid == 0)
	{
		/* CHILD PROCESS */

		pid_t parent = getppid();
		some_value = 0x1234abcd;

		ptrace(PTRACE_TRACEME, 0, NULL, NULL);

		/* Have the child send itself a signal */
		raise(SIGCONT);

		/* Hang around until the parent disappears */
		while (parent == getppid())
			sleep(1);
		exit(0);
	}
	else if (child_pid < 0)
	{
		perror("fork() didn't work");
		exit(1);
	}

	/* PARENT PROCESS */

	/* Wait for child to change state (should really check that the child
	 * hasn't exited) */
	wait(NULL);

	errno = 0;
	long ret = ptrace (PTRACE_PEEKDATA, child_pid, &some_value, NULL);
	if (ret == -1 && errno != 0)
	{
		perror("ptrace() didn't work");
		exit(1);
	}

	printf("Got %#lx\n", ret);

	exit(0);
}

/*
 *  vi:ts=8 sw=8 noet:
 */