timeit.asm

section .data
	OUTPUT_FMT: db "timeit: %ds %dus", 0x0a, 0x0

;引用的库函数与导出的符号
section .text
	global main 
	extern fork
	extern time
	extern sleep
	extern wait
	extern execvp
	extern printf 
	extern gettimeofday

main:
;{
	push rbp
	mov rbp, rsp
	push rdi
	push rsi 
	cmp rdi, 1
	je normal_end	

	;gettimeofday;
	sub rsp, 0x10
	mov rdi, rsp
	mov rsi, 0
	mov rax, 0 
	call gettimeofday wrt ..plt 

	;fork()
	mov rax, 0
	call fork wrt ..plt	
	cmp rax, 0 
	jne wait_child_process 
	
	add rsp, 0x10
	pop r8 
	add r8, 8
	;path -> argv[1]
	mov rdi, [r8] 
	;argv -> argv[1]...
	mov rsi, r8
	call execvp wrt ..plt 
	leave 
	ret 

wait_child_process:
	;wait()
	mov rax, 0
	call wait wrt ..plt	

	sub rsp, 0x10
	mov rdi, rsp
	mov rsi, 0
	mov rax, 0
	call gettimeofday wrt ..plt

	;s
	mov rsi, qword [rsp]
	sub rsi, qword [rsp+16] 
	;ms
	mov rdx, qword [rsp+8]
	sub rdx, qword [rsp+24] 
	cmp rdx, 0
	jl fix_tv_sec
	mov rdi, OUTPUT_FMT 
	mov rax, 0
	call printf wrt ..plt 
	jmp normal_end 

fix_tv_sec:		
	dec rsi
	neg rdx
	mov rdi, OUTPUT_FMT 
	mov rax, 0
	call printf wrt ..plt 

normal_end:
	mov rax, 0
	leave
	ret 
;}