alx-tools/hack-the-virtual-memory

This is a series of small articles / tutorials based around virtual memory. The goal is to learn some CS basics, but in a different and more practical way.

Hack the Virtual Memory

This is a series of small articles / tutorials based around virtual memory. The goal is to learn some CS basics, but in a different and more practical way.

TOC

00. C strings & /proc

For this first piece, we'll use /proc to find and modify variables (in this example, an ASCII string) contained inside the virtual memory of a running process, and learn some cool things along the way.

Status: Published

01. Python bytes

For this second piece, we'll do almost the same thing, but instead we will access the virtual memory of a running Python 3 script. It is not as straightfoward. Let's take this as an excuse to look at some Python 3 internals!

Status: Published

02. What's where in the virtual memory

Let's try to guess where things are in the virtual memory.

Status: Published

03. malloc, the heap and the program break

In this fourth chapter we will look at the heap and how malloc works in order to answer some of the questions we ended with at the end of the previous chapter.

Status: Published

04. The stack, registers and assembly code

Status: In progress

hack-the-virtual-memory's Issues

Why not sync to your website

Why not sync to your website:
https://blog.holbertonschool.com/hack-the-virtual-memory-malloc-the-heap-the-program-break/

Translate request

Hi, I want to translate the series articles of "Hack-The-Virtual-Memory" to Chinese and post on my blog for not commercial use, is it OK?

Actually, I've translated the first four articles last years without your permission, because I don't know I should ask who for permission.

Follow is my blog：http://blog.coderhuo.tech/2017/10/19/Virtual_Memory_summary/

Why not update it

Can I ask a question

I run 00. C strings & the proc filesystem success.
But I add some code to print pid of current process, then failed.
Then I move the code, it success again. I don't know why.

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
+ #include <unistd.h>
+ #include <sys/types.h>

/**
 * main - uses strdup to create a new string, and prints the
 * address of the new duplcated string
 *
 * Return: EXIT_FAILURE if malloc failed. Otherwise EXIT_SUCCESS
 */
int main(void)
{
	char *s;
+       pid_t pid = getpid();
+       printf("pid: %lun", pid);
	s = strdup("Holberton");

	if (s == NULL)
	{
		fprintf(stderr, "Can't allocate mem with malloc\n");
		return (EXIT_FAILURE);
	}
	printf("%p\n", (void *)s);
	return (EXIT_SUCCESS);
}

gcc main.c -o holberton 
./holbeton
./read_write_heap.py ${PID}  "Holberton" "hello,world" ## still output Holberton

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
+ #include <unistd.h>
+ #include <sys/types.h>

/**
 * main - uses strdup to create a new string, and prints the
 * address of the new duplcated string
 *
 * Return: EXIT_FAILURE if malloc failed. Otherwise EXIT_SUCCESS
 */
int main(void)
{
	char *s;
	s = strdup("Holberton");
+       pid_t pid = getpid();
+       printf("pid: %lun", pid);

	if (s == NULL)
	{
		fprintf(stderr, "Can't allocate mem with malloc\n");
		return (EXIT_FAILURE);
	}
	printf("%p\n", (void *)s);
	return (EXIT_SUCCESS);
}

gcc main.c -o holberton 
./holbeton
./read_write_heap.py ${PID}  "Holberton" "hello,world" ## output Holberton changed to hello,world

I don't understand why.

operating system

cmd error

In this article: 04. The Stack, registers and assembly code

Follow cmd error.
objdump without target file.

    holberton$ gcc 0-main.c
    holberton$ objdump -d -j .text -M intel