CMPT 295

• Unit - Machine-Level Programming
• Lecture 15
  • Assembly language
  • Program Control
  • Function Call and Stack
  • Passing Control – cont’d

Happy Lunar New Year!

• 新年快乐 / 新年快樂 – Xīnnián kuàile
• Cung Chúc Tân Xuân
• Chúc Mừng Năm Mới
• 새해 복 많이 받으세요 – saehae bog manh-i bad-euseyo
• 过年好 / 過年好 – Guò nián hǎo

Homework

Memory Allocation Example

Where does everything go?

Code:

#include ... //shared libraries
char hugeArray[1 << 31]; /* 231 = 2GB */// data
int global = 0; // data
int useless(){ return 0; } // text
int main ()
{
  void *ptr1, *ptr2; //stack
  int local = 0; //stack
  ptr1 = malloc(1 << 28); /* 228 = 256 MB*/ //heap
  ptr2 = malloc(1 << 8); /* 28 = 256 B*///heap

  /* Some print statements ... */
}

Stack in list form:

• Stack (down arrow)
• …
• Shared libraries
• …
• heap (up arrow)
• data
• Text
• …

Why 8?

• pushq src
  • Fetch value of operand src
  • Decrement %rsp by 8
  • Write value at address given by %rsp
• popq dest
  • Read value at %rsp (address) and store it in operand dest (must be register)
  • Increment %rsp by 8

1) %rsp contains the memory address 0x0018

2) %rsp contains the memory address ____

Last Lecture

• Function call mechanisms: 1) passing control, 2) passing data, 3) managing local data on memory (stack)
  • Memory layout
  • Stack (local variables …)
  • Heap (dynamically allocated data)
  • Data (statically allocated data)
  • Text / Shared Libraries (program code)
• A “stack” is the right data structure for function call / return
  • If multstore calls mult2, then mult2 returns before multstore returns
• x86-64 stack register and instructions: stack pointer %rsp, push and pop

(unless I’m missing something, this contains exactly the same slides as Lecture 14 here. Everything in the “example 1 steps X and Y” portion, read that for this section)

Summary

• Function call mechanisms: 1) passing control, 2) passing data, 3) managing local data on memory (stack)
• Memory layout
  • Stack (local variables …)
  • Heap (dynamically allocated data)
  • Data (statically allocated data)
  • Text / Shared Libraries (program code)
• A “stack” is the right data structure for function call / return
  • If multstore calls mult2, then mult2 returns before multstore returns
• x86-64 stack register and instructions: stack pointer %rsp, push and pop
• x86-64 function call instructions: call and ret

Next Lecture

• Introduction
  • C program -> assembly code -> machine level code
• Assembly language basics: data, move operation
  • Memory addressing modes
• Operation leaq and Arithmetic & logical operations
• Conditional Statement – Condition Code + cmovX
• Loops
• Function call – Stack – Recursion
  • Overview of Function Call
  • Memory Layout and Stack - x86-64 instructions and registers
  • Passing control
  • (highlighted) Passing data – Calling Conventions
  • Managing local data
  • Recursion
• Array
• Buffer Overflow
• Floating-point operations