ARM Tutorial

Introduction

This reader introduces the basics of ARM v7 assembly. The primary goal is to help students who already know how to program in a high level language learn about the form their programs take after compiling - the kinds of instructions a computer really processes information. These materials provide examples of basic ARM instructions, assembly programming constructs, and how high level languages constructs are represented in assembly.

Things this reader is NOT: a standalone course - it is a resource for a class; focused on “real” ARM programming - the goal is to understand how assembly works, not become a working assembly developer.

Assumed background knowledge:

• High-level programming experience (preferably C++)

• Basic binary and data representation in binary

• Boolean logic - AND / OR/ XOR

Conventions:

Samples will sometimes end with an infinite loop:

end:     b  end

This is provided to prevent the simulator from running invalid instructions or data. Often times, this will be omitted for brevity, in which case the simulator will report an error after attempting to run past the last instruction.

All code should start with:

.text                @identifies this is code
.global _start       @declare _start symbol to be globally visible
_start:              @identify this location as entry point for the program

It is often omitted as the simulator will assume that it should start at the first line of code it encounters.

Topics

• 1. Basics
  • 1.1. Instruction format
  • 1.2. Data Movement
  • 1.3. Arithmetic
  • 1.4. Rotation
  • 1.5. Shifts
  • 1.6. Operand Shifts
  • 1.7. Multiply
  • 1.8. Immediate Values
• 2. Memory
  • 2.1. Directives and Identifiers
  • 2.2. Sections
  • 2.3. Data & Alignment
  • 2.4. Endianness and Address Numbering
  • 2.5. Loading & Storing
  • 2.6. Loading & Storing Bytes
• 3. Bitwise Operations
  • 3.1. Bitwise Logic 1
  • 3.2. Bitwise Logic 2
  • 3.3. Masking
  • 3.4. Clearing
• 4. Branches and Control Structures
  • 4.1. Branch
  • 4.2. Condition Codes
  • 4.3. Conditional Branches
  • 4.4. If Else Implementation
  • 4.5. Loops
  • 4.6. Doing Work in Loops
  • 4.7. ARM Trick - Conditional Execution
  • 4.8. ARM Trick - Set Bits
• 5. Arrays and Strings
  • 5.1. Array Basics
  • 5.2. Array Access
  • 5.3. Looping Through Arrays
  • 5.4. Array Loop Shifted Index
  • 5.5. Strings
• 6. Functions and the Stack
  • 6.1. The Stack
  • 6.2. Pushing and Popping
  • 6.3. Branch and Link
  • 6.4. Calling Conventions
  • 6.5. A Simple Function Call
  • 6.6. A Smarter Function Call
  • 6.7. Another Function
  • 6.8. Nested Function Calls
  • 6.9. Stack Frames
  • 6.10. Using the Stack Frame
  • 6.11. Final Calling Convention
• 7. Objects
  • 7.1. Objects in High Level Languages
  • 7.2. Objects Data
  • 7.3. Member Functions
  • 7.4. Calling Member Functions
  • 7.5. Jump Tables
  • 7.6. Virtual Functions
  • 7.7. Virtual Functions Sample

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