Gain insights into debugging C/C++ programs on Linux ARM64, delve into program disassembly, probe memory/register changes using GDB, and discover techniques for core dump analysis and assembly-level debugging.

Practical-Foundations-ARM64 Linus Debugging- Disassembly-Reversing.png

arm.tar.gz

Codeoptmization

Pointers_to_assign

Pointers

MemoryPointers

PointersAsVariables

PointersAsVariables-optimization

SimpleStack

LocalVariables

FunctionParameters

FunctionParameters-14

solution

FunctionParameters-14-copy

RawStack

MemoryPointers-copy

The 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. You’ll use the Linux ARM64 which is a popular RISC architecture. You’ll use simple operations in C/C++ such as assignment, increment, addition, multiplication. With the help of the GDB, you will probe into the contents of the registers and memory. You'll learn how they are changed while executing basic operations. With the help of the disassembly output, you’ll learn how a simple C/C++ program can be reconstructed. The disassembly output is important for debugging and core dump analysis.

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.

Foundations of Linux ARM64: Debug, Disassemble, and Reverse

# Disassembly in the optimization mode
Let's review the disassembly generated by compiling the program in the optimization mode. We will revisit the source code first and review the flags needed to trigger the optimization.
## Source code
The source code of the arithmetic program is given below:

int a, b;

int main(int argc, char* argv[])
{
	a = 1;

	b = 1;

	b = b + a;

	++a;

	b = b * a;

	return 0;
}

The flowchart below shows the working of the source code:

## Compilation

We can add certain flags for optimizing the code while compiling our source file. A flag, `-O`, is used for the optimization of code, and `-O1` is an optimization flag that further optimizes the code size and execution time. There are other flags for optimization, such as `-O2`, and `-O3`, which reduce the size and execution time of the code even further.

We compile and link the program in optimization mode in the following way:



Learn how to compile, load, and execute the GDB disassembly program with code optimization. 

Introduction to the Course

Memory, Registers, and Simple Arithmetic

Code Optimization

Number Representations

Pointers

Bytes, Half Words, Words, and Double Words

Pointers to Memory

Logical Instructions and PC

Reconstructing a Program with Pointers

Memory and Stacks

Frame Pointer and Local Variables

Function Parameters

More Instructions

Function Pointer Parameters

Conclusion

ARM64 Linux Debugging, Disassembling, Reversing Exam

GDB Disassembly Output – Optimization

Disassembly in the optimization mode

Source code

Compilation