Gain insights into using GDB for debugging in Linux. Explore disassembly, memory investigation, and register updates. Learn about pointers, stack, and function parameters in x64 architecture.

gdb.tar.gz

C2-LA

C4-L2

C4-L3

C4-L4

C4-L5

C6-L3

C8-L1

C9-L3

C10-L2

C10-L3

C11-L2

C13-L1

test

GNU Debugger (GDB) is used for debugging C/C++ programs in LINUX/UNIX environments. It is a good tool to investigate what is happening inside a program, and how the contents inside the memory are changed with the execution of the program.

The main focus of the course is the disassembly of the program, where we'll use simple operations in C. With the help of GDB, we'll examine the contents of the registers and memory. We'll also learn how they are changed while executing basic operations. We’ll then explore the use of pointers, stack, and function parameters, and analyze how different registers update their values. With the help of disassembly output, we’ll learn how a simple C program can be reconstructed. The disassembly output is important for debugging and core dump analysis. We’ll use assembly language for x64 architecture.

By the end of this course, you should be able to debug the programs and memory contents at assembly level when a program executes or probe into the problem when a program crashes.

Debugging, Disassembly & Reversing in Linux for x64 Architecture

# Conditional jumps
Consider these two C/C++ code fragments:


if (a == 0)             if (a != 0)
{                       {
    ++a;                    ++a;
}                       }
else                    else
{                       {
    --a;                    --a;
}                       }

CPU fetches instructions _sequentially_, so we must tell the CPU that we want to skip some instructions if some condition is met (or not met)—for example, if `a != 0`.

The `JNZ` (_jump if not zero_) and `JZ` (_jump if zero_) instructions test the `ZF` flag and change `%RIP` if the `ZF` bit is cleared for `JZN` or set for `JZ`. The following assembly language code is equivalent to the C/C++ code above:


Learn about different modes like conditional jumps, register structures, return values, and byte registers.

Introduction to the Course

Memory, Registers, and Simple Arithmetic

Code Optimization

Number Representations

Pointers

Bytes, Words, Double, and Quad Words

Pointers to Memory

Logical Instructions and RIP

Reconstructing a Program with Pointers

Memory and Stacks

Frame Pointer and Local Variables

Function Parameters

More Instructions

Function Pointer Parameters

Summary of Code Disassembly Patterns

x64 Debugging, Disassembly & Reversing Exam

Instructions II