Several basic assembly instructions

Several basic assembly instructions in detail common registers

Register Device	16 Guests	32 Guests	64 Guests
Cumulative register	Ax	EAX	RAX
Base Address Register	Bx	EBX	RBX
Count Register	CX	Ecx	RCX
Data registers	Dx	EDX	Rdx
Stack base pointer	Bp	Ebp	RBP
Variable address register	SI	Esi	RSI
Stack top pointer	Sp	Esp	RSP
Instruction Register	Ip	Eip	Rip

Assembly Instructions MOV

• MOVB (8-bit), MOVW (16-bit), MOVL (32-bit), MOVQ (64-bit)

• Register addressing:
  
  movl%eax,%edx
  
  EAX-EdX

• Immediate number addressing:
  
  movl $0x123,%edx
  
  Digital Register

• Direct addressing:
  
  movl 0x123,%edx
  
  Direct access to memory address data, edx = * (int32_t *) 0x123;

• Indirect addressing:
  
  MOVL (%EBX),%edx
  
  %EBX is a memory address, (%EBX) refers to the data in that address, edx = * (int32_t*) ebx;

• Variable address addressing:
  
  MOVL 4 (%EBX),%edx
  
  edx = * (int32_t*) (ebx+4);

The Push & pull stack data structure introduces the role:

• Program Call Framework
• Passing parameters
• Save return address
• Provide local variables
• ......

Structure:

• Related registers: ESP, EBP

• Related actions: Pop, push

  //建立被调用者函数的堆栈框架pushl %ebpmovl %esp, %ebp//拆除框架movl %ebp, %esppopl %ebpret

Push: Press Stack

• Push%eax
  
  Equivalent:

  subl $4, %esp//栈顶指针减4movl %eax, (%esp)//%eax -> esp 地址

Pop: Out of the stack

• Pop%eax
  
  Equivalent:

  movl (%esp), %eaxaddl %4, %esp//栈顶指针加4

Call&retcall

• Call 0x12345
  
  Equivalent:

  pushl %eipmovl $0x12345, %eip//当前地址压栈，存入新地址

Ret

• Equivalent:

  popl %eip//栈 -> eip

Enter&leaveenter

    push %ebp    movl %esp, %ebp    //将堆栈置空（栈上重堆）

Leave

    movl %ebp, %esp    popl %ebp    //将堆栈置空（撤销堆栈）

Example: Analyzing a piece of assembly code

    pushl $8   ①    movl %esp, %ebp     ②    subl $4, %esp  ③    movl $8, (%esp)        ④

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Several basic assembly instructions