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

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

int main(int argc, char **argv)
{
	if (argc < 3) {
		fprintf(stderr, "%s [pid] [address]\n", argv[0]);
		return 0;
	}
	pid_t proc_pid = strtol(argv[1], NULL, 0);
	off_t vm_addr = strtol(argv[2], NULL, 0);
	int proc_mem_fd = 0;
	char proc_mem_path[255];

	snprintf(proc_mem_path, sizeof(proc_mem_path) - 1, "/proc/%i/mem", proc_pid);
	if ((proc_mem_fd = open(proc_mem_path, O_RDWR)) < 0) { // open process memory
		perror("open");
		return 1;
	}
	if (ptrace(PTRACE_ATTACH, proc_pid, NULL, NULL) < 0) { // attach to process
		perror("ptrace");
		return 1;
	}
	waitpid(proc_pid, NULL, 0); // wait for the tracee to stop (SIGSTOP) completly

	uint64_t mem_val = 0;
	// a read unsigned 64 bit integer from the specified address
	if (pread(proc_mem_fd, &mem_val, sizeof(uint64_t), vm_addr) < 0) {
		perror("pread");
		return 1;
	}
	printf("value at 0x%lx:%lx\n", vm_addr, mem_val);

	if (ptrace(PTRACE_DETACH, proc_pid, NULL, NULL) < 0) { // detach from process
		perror("ptrace");
		return 1;
	}
	close(proc_mem_fd);
	return 0;
}