How the operating system works
Computer three magic weapons:
1. stored program computer;
2. The function call stack mechanism;
3. interrupt mechanism;
Function call stack
The role of the stack
1. Record function call frame;
2. The transfer function parameters, methods: from left to right;
3. Save the value of the return address;
4. The function of the internal memory space to provide local variables;
Of registers and operations
ESP: stack pointer;
EBP: base pointer;
push: 4 bytes reduce stack address, and the operand stack into a storage unit;
pop: 4 bytes stack address is incremented, and the top of stack operand into the storage unit;
Stack is from high address to the low address increased.
Other key register
CS: EIP always point to the address of the next instruction.
Sequentially performed: consecutive addresses always points to the next instruction;
Jump / branch: performing such a command, CS: EIP values may need to be modified in accordance with a program;
call: the current CS: EIP values in onto stack, CS: EIP points to the entry address of the called function.
ret: pop from the stack to save the original CS: EIP value, and put CS: EIP in;
Inline assembly
Keyword
asm : GCC macro definition is asm keyword is a keyword inline assembly. asm _asm_ and can be used interchangeably, # DEFINE asm asm;
volatile : the volatile keyword is GCC macro definition, do not optimizing compiler code, assembly instructions intact. asm _asm_ and can be used interchangeably, # DEFINE volatile volatile;
grammar
asm volatile（
汇编语言模板：
输出部分：
输入部分:
破坏描述部分）
experiment
patch -pl < ../mykernel_for_linux3.9.4sc.patch4
qemu -kernel arch/x86/boot/bzImage
After the experimental platform kernel boot effect