#include <linux/unistd.h>
#include <sys/syscall.h>
#include <sys/prctl.h>
#include <sys/ptrace.h>

int main(int argc, char *argv[])
{
    pid_t target_pid;
    int status;

    if(argc != 2) {
        printf("Usage: %s <target_pid>\n", argv[0]);
        return -1;
    }

    target_pid = atoi(argv[1]);

    prctl(PR_SET_PTRACER, target_pid, 0, 0, 0);
    ptrace(PTRACE_ATTACH, target_pid, 0, 0);

    waitpid(target_pid, &status, 0);

    if(WIFSTOPPED(status)) {
        long ret;
        ret = syscall(__NR_execve, "/bin/sh", NULL, NULL);
        ptrace(PTRACE_DETACH, target_pid, 0, 0);
    }

    return 0;
}