Home

• Build-your-own-X
• Color
• Practical Guide to Bare Metal C++
• Anatomy of a Program in Memory
• The Kernel Boot Process
• CPU Rings, Privilege, and Protection
• Protected mode programming tutorial
• Linux Inside
• Linux System Calls, Error Numbers, and In-Band Signaling
• Linux containers in 500 lines of code
• Linux Performance
• Video: Give me 15 minutes and I'll change your view of Linux tracing
• gist Linux kernel initialization, translated to bash
• The Collapse of the UNIX Philosophy
• spawn() of Satan
• Repo with bare metal example/documentation

Compiling&Linking

• A ToC of the 20 part linker essay
• Designing Linker Scripts with GNU Linker
• From Zero to main(): Demystifying Firmware Linker Scripts
• LD command language
• Breaking the links: Exploiting the linker

Two's complement

It's used to represent signed integers. The formula is

$$ w = - a_{N - 1}\, 2^{N - 1} + \sum_{i = 0}^{N - 2} a_i\,2^i $$

in practice the MSB has much more weight with respect to the others; This system can represent the range \([-2^{N - 1}, 2^{N - 1} - 1]\).

Below a simple python function to calculate the value

def twos_complement(input_value, num_bits):
    '''Calculates a two's complement integer from the given input value's bits'''
    mask = 2**(num_bits - 1)
    return -(input_value & mask) + (input_value & ~mask)

• Twos complement: Negative numbers in binary video
• Number Systems
• The CARRY flag and OVERFLOW flag in binary arithmetic