Reverse Engineering Notes - Header.s

 What is Header.s?

Header.s is a file in the x86 architecture-specific directory (arch/x86/boot) of the Linux kernel source code. It contains assembly code that is executed by the boot loader (such as GRUB) to load the Linux kernel image into memory and transfer control to the kernel's entry point.

The header.s file performs several important tasks, including:

1. Setting up the initial stack pointer for the kernel.

2. Setting up the initial memory mappings for the kernel.

3. Loading the kernel image into memory from the boot device.

4. Setting up the boot parameters for the kernel.

5. Transferring control to the kernel's entry point.

The header.s file is called by the boot loader during the boot process of the system. When the system is powered on, the boot loader loads the header.s file into memory and begins executing its code. The header.s code then loads the kernel image into memory and transfers control to the kernel's entry point.

In summary, the header.s file is an assembly language file that is used to bootstrap the Linux kernel during the boot process. It is called by the boot loader and is responsible for setting up the initial environment for the kernel and transferring control to the kernel's entry point.