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Questions and Answers
What is the primary function of the 'mov' instruction in x86 assembly?
What is the primary function of the 'mov' instruction in x86 assembly?
Which instruction is used to load an effective address into a register?
Which instruction is used to load an effective address into a register?
What does the instruction 'mov eax, [ebx+esi*4]' do?
What does the instruction 'mov eax, [ebx+esi*4]' do?
Why is 'mov eax, ebx+8' considered invalid in x86 assembly?
Why is 'mov eax, ebx+8' considered invalid in x86 assembly?
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If you want to copy a value from a memory address into a register, which instruction should you use?
If you want to copy a value from a memory address into a register, which instruction should you use?
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What does the instruction 'jg loc' do in assembly language?
What does the instruction 'jg loc' do in assembly language?
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Which instruction performs a jump if the destination operand is less than the source operand?
Which instruction performs a jump if the destination operand is less than the source operand?
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What is the effect of the instruction 'jge loc'?
What is the effect of the instruction 'jge loc'?
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What condition does 'jecxz loc' check before performing the jump?
What condition does 'jecxz loc' check before performing the jump?
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Which instruction should be used for an unsigned comparison to check if the destination is greater than the source?
Which instruction should be used for an unsigned comparison to check if the destination is greater than the source?
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What is a characteristic of the C programming language that makes it distinct from higher-level languages?
What is a characteristic of the C programming language that makes it distinct from higher-level languages?
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Which section of computer memory grows by making function calls?
Which section of computer memory grows by making function calls?
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What is the primary function of a disassembler?
What is the primary function of a disassembler?
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How does an assembler differ from a compiler?
How does an assembler differ from a compiler?
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Which of the following describes low-level languages?
Which of the following describes low-level languages?
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What is a key feature of interpreted languages?
What is a key feature of interpreted languages?
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In x86 architecture, what role does microcode play?
In x86 architecture, what role does microcode play?
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Which statement is true regarding assembly language?
Which statement is true regarding assembly language?
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What is the value of argc when the program is executed with the command 'filetestprogram.exe -r filename.txt'?
What is the value of argc when the program is executed with the command 'filetestprogram.exe -r filename.txt'?
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What does the statement 'strncmp(argv, "-r", 2) == 0' check for in the program?
What does the statement 'strncmp(argv, "-r", 2) == 0' check for in the program?
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What will happen if the condition 'argc != 3' evaluates to true?
What will happen if the condition 'argc != 3' evaluates to true?
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In the assembly code, which instruction is executed to compare argc with the value 3?
In the assembly code, which instruction is executed to compare argc with the value 3?
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What is likely to occur if the command 'filetestprogram.exe -r filename.txt' is altered to 'filetestprogram.exe filename.txt'?
What is likely to occur if the command 'filetestprogram.exe -r filename.txt' is altered to 'filetestprogram.exe filename.txt'?
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Which assembly syntax reverses the order of operands and uses a % before registers?
Which assembly syntax reverses the order of operands and uses a % before registers?
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What does EAX primarily serve as in the context of x86 registers?
What does EAX primarily serve as in the context of x86 registers?
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In a little-endian format, where is the low-order byte stored?
In a little-endian format, where is the low-order byte stored?
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Which of the following segment registers points to the code segment containing instructions?
Which of the following segment registers points to the code segment containing instructions?
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What is the role of the EIP register in the CPU?
What is the role of the EIP register in the CPU?
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What does the CF flag represent in the EFLAGS register?
What does the CF flag represent in the EFLAGS register?
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Which of the following registers is used primarily as a source index for string operations?
Which of the following registers is used primarily as a source index for string operations?
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Which general register is used for holding loop counts during iterative operations?
Which general register is used for holding loop counts during iterative operations?
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What is the purpose of the EBP register in x86 architecture?
What is the purpose of the EBP register in x86 architecture?
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Which statement best describes segment registers in x86 architecture?
Which statement best describes segment registers in x86 architecture?
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What happens to the EIP when a function is called?
What happens to the EIP when a function is called?
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Which instruction is equivalent to using 'sub' but only sets the Zero Flag and Carry Flag without modifying the operands?
Which instruction is equivalent to using 'sub' but only sets the Zero Flag and Carry Flag without modifying the operands?
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What does the 'jz' instruction do in a program's control flow?
What does the 'jz' instruction do in a program's control flow?
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What is the primary purpose of a function restoring local variables and EBP after execution?
What is the primary purpose of a function restoring local variables and EBP after execution?
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What do conditional jumps rely on to determine program control flow?
What do conditional jumps rely on to determine program control flow?
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What is the result of the 'test' instruction when used in a program?
What is the result of the 'test' instruction when used in a program?
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How many different types of conditional jumps are mentioned?
How many different types of conditional jumps are mentioned?
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In the context of stack operations, what must happen before a function call completes successfully?
In the context of stack operations, what must happen before a function call completes successfully?
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Study Notes
QUT Acknowledgement of Traditional Owners
- QUT recognizes the Turrbal and Yugara peoples as the First Nations owners of the land.
- Respect is paid to Elders, customs, lores, and creation spirits.
- The land has always been a place of learning, teaching, and research.
- QUT acknowledges the important role of Aboriginal and Torres Strait Islander people within their community.
Principles of Software Security (IFN657 Lecture 3)
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Key Points from Last Lecture (C and C#):
- C is efficient but error-prone, closely related to the machine model with flexible memory management.
- C# is type-safe, with built-in bounds and string checks, and automatic memory management.
- Computer memory is divided into sections (stack, heap).
- Stack grows as function calls are made.
- Heap grows dynamically as memory is allocated.
x86 Architecture - Assembly Basics
- x86 architecture and assembly basics
Machine vs. Assembly vs. C
- Shows the relationship between C code, compiled machine code, and assembly code.
- Demonstrates the translation process from a high-level language (C) to low-level machine code.
- Includes example C code, generated machine code (in hexadecimal format), and assembly instructions.
Levels of Abstraction
- Hardware: Basic electrical circuits implementing logical operations (XOR, AND, OR, NOT).
- Microcode (Firmware): Lower-level instructions.
- Machine code: Opcodes (hexadecimal digits) that tell the processor what to do.
- Low-level languages: Human-readable versions of an architecture's instruction set.
- High-level languages: Transformed into machine code at compilation (e.g., C/C++).
- Interpreted languages: Translated to bytecode, then executed.
Assembly Language
- Assembly is the highest-level language reliably recovered from machine code.
- Vulnerable code or malware is typically stored in binary at the machine code level.
- Disassemblers convert binary to assembly language code.
- Assembly language is a class of languages, with x86 as a specific focus (explained in more detail).
Assemblers and Linkers
- Assemblers and linkers are tools used in software development that manipulate object files and libraries in creating and managing executable code.
- Assembly files are transformed into object files by assemblers.
- Object files are linked into an executable file by a linker that also incorporates libraries.
Assembler vs. Compiler
- Compilers translate high-level languages to machine code in a single step.
- Assemblers translate assembly language to machine code in multiple steps.
- A compiler checks and converts the entire code simultaneously, whereas an assembler typically works in multiple passes.
- Compilers may include a lexical analyzer (scanning), syntax analyzer, semantic analyzer, code optimizer, code generator, and produce mnemonic versions.
AT&T vs. Intel Syntax (NASM)
- Two main assembly language syntax forms.
- NASM format uses a different order, and symbols before registers/literals.
- AT&T format, uses the reverse order, and includes % before registers and $ before literal values.
Fundamental Data Types
- Binary representations of data types (bytes).
Memory
- Memory addresses and their corresponding data.
Data in Memory (Little-Endian Format)
- How data is stored in memory using little-endian format
CPU Registers
- A small amount of data storage directly accessible by the CPU.
- Registers are faster accessible than memory.
x86 Registers
- Categorizes x86 registers into General, Segment, Status, and Instruction Pointer registers.
General Registers
- Storing data or memory addresses and functions like storing data.
x64 Registers
- A further division of x86 registers based on 64-bit architecture
Data Registers
- Functions of EAX, EBX, ECX, EDX registers (explained in more detail).
Index Registers
- Functions of ESI (source) and EDI (destination) registers.
Segment Registers
- Functions of CS (Code Segment), DS (Data Segment), SS (Stack Segment) for referencing code, global data and stack, respectively.
- ES, FS, and GS provide additional segments.
- Memory address are relative to the starting address of the segment.
Status Registers
- Functions of ZF, CF, SF, TF flags (zero, carry, sign, trap).
Instruction Pointer (EIP)
- Points to the next instruction to be executed.
- The complete address consists of a segment selector and offset.
Other Pointer Registers
- ESP (Stack Pointer) and EBP (Base Pointer) are described.
- ESP points to the top of the stack, while EBP points to the current stack frame or local variables in current functions.
Simple Instructions
- Functions and uses of various instructions like MOV, LEA, arithmetic instructions (e.g., ADD, SUB, INC, DEC, MUL, DIV), logic instructions(e.g., XOR, OR, SHR, ROR), and the 'nop' instruction.
Stack Layout
- Visual representation of the stack with multiple stack frames.
Function Calls
- Process of calling and returning from a function explained.
Conditionals
- Functions of test and cmp instructions and how they use flags (ZF, CF).
Branching
- Types of unconditional jumps (JMP) and conditional jumps (e.g., JZ, JNZ, JG, JGE).
Examples of Conditional Jumps
- A variety of conditional jumps.
C Main Method and Offsets
- How C programs organize arguments using the main method (argc, argv array).
A Simple C Program (and compiled form)
- C program demonstrating the usage of file operations.
- Shows assembly code after compilation.
Home Readings
- List of resources for additional learning about NASM Assembly.
Studying That Suits You
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Description
This quiz covers key points from Lecture 3 of Principles of Software Security. It focuses on the programming languages C and C#, highlighting their memory management differences and safety features. Additionally, it delves into foundational concepts essential for understanding assembly language in the context of x86 architecture.
