[Computer Architecture] - Register

<레지스터 레이아웃>

• rax is the 64-bit, "long" size register.  It was added in 2003 during the transition to 64-bit processors.
• eax is the 32-bit, "int" size register.  It was added in 1985 during the transition to 32-bit processors with the 80386 CPU.  I'm in the habit of using this register size, since they also work in 32 bit mode, although I'm trying to use the longer rax registers for everything.
• ax is the 16-bit, "short" size register.  It was added in 1979 with the 8086 CPU, but is used in DOS or BIOS code to this day.
• al and ah are the 8-bit, "char" size registers.  al is the low 8 bits, ah is the high 8 bits.  They're pretty similar to the old 8-bit registers of the 8008 back in 1972.

레지스터의 종류

Name	Notes	Type	64-bit long	32-bit int	16-bit short	8-bit char
rax	Values are returned from functions in this register.  누산기(accumulator) 레지스터	scratch	rax	eax	ax	ah and al
rcx	Typical scratch register.  Some instructions also use it as a counter. 카운터(counter)  레지스터	scratch	rcx	ecx	cx	ch and cl
rdx	Scratch register. 데이터(data) 레지스터	scratch	rdx	edx	dx	dh and dl
rbx	Preserved register: don't use it without saving it! 베이스(base) 레지스터	preserved	rbx	ebx	bx	bh and bl
rsp	The stack pointer.  Points to the top of the stack (details coming soon!)	preserved	rsp	esp	sp	spl
rbp	Preserved register.  Sometimes used to store the old value of the stack pointer, or the "base".	preserved	rbp	ebp	bp	bpl
rsi	Scratch register.  Also used to pass function argument #2 in 64-bit Linux 근원지 인덱스(source index) 레지스터	scratch	rsi	esi	si	sil
rdi	Scratch register.  Function argument #1 in 64-bit Linux 목적지 인덱스(destination index) 레지스터	scratch	rdi	edi	di	dil
r8	Scratch register.  These were added in 64-bit mode, so they have numbers, not names.	scratch	r8	r8d	r8w	r8b
r9	Scratch register.	scratch	r9	r9d	r9w	r9b
r10	Scratch register.	scratch	r10	r10d	r10w	r10b
r11	Scratch register.	scratch	r11	r11d	r11w	r11b
r12	Preserved register.  You can use it, but you need to save and restore it.	preserved	r12	r12d	r12w	r12b
r13	Preserved register.	preserved	r13	r13d	r13w	r13b
r14	Preserved register.	preserved	r14	r14d	r14w	r14b
r15	Preserved register.	preserved	r15	r15d	r15w	r15b

 

Conditioion Code Register(상태 레지스터)

상태 레지스터, 플래그 레지스터 라고도 불리며 1비트 레지스터로 구성되어 있다. (t = a+b)

CF	Carry flag(올림수)	if carry out from most significant bit (unsigned overflow)
SF	Sign flag(부호)	t == 0
ZF	Zero flag	t < 0
OF	Overflow flag	two's complement (signed) overflow (a > 0 && b > 0 && t < 0) || (a < 0 && b < 0 && t > 0)

 

레지스터 인자 전달

 

-리눅스 ELF 환경에서는 다음과 같은 순서로 함수의 인자를 전달받는다

 

Parameter 1 - rdi

Parameter 2 - rsi

Parameter 3 - rdx

Parameter 4 - rcx

Parameter 5 - r8(범용레지스터)

Parameter 6 - r9(범용레지스터)

 

-인자가 7개 이상일경우 스택을 사용한다.

 

Parameter 7 - (%rsp)

Parameter 8 - 0x8(%rsp)

system call - %rax