20230818 CHAPTER 5 Thanks for the Memories arm64汇编内存使用

标签：CHAPTER Memories mov write w3 Thanks x2 x0 内存

.data 段的内存引用实例

十进制数不要以0开头，否则会被认为是8进制数

一个数前面可以加-负号或者~取反符号；

 

申请一个内存块；

 

重复！

转义字符！

内存对齐

 

 

The offset from the PC has 19 bits in the instruction, which gives a range of +/-1MB. The offset address is in words

“ldr X1, #8” means 8 words from the current instruction. Any data that you want to modify should go in a .data section.

 

 

 

 

 

 

 　　updates X1 with the value calculated

 

 

 一个程序：把字符串转成大写

.global _start
_start:
	ldr x0,=instr
	ldr x1,=outstr

	mov x2,0
loop:
	ldrb w3,[x0,x2]
	cmp w3,0
	b.eq cout	//reach the end of instr
	cmp w3,'a'
	b.cc write
	cmp w3,'z'
	b.hi write
	sub w3,w3,'a'-'A'
write:
	strb w3,[x1,x2]
	add x2,x2,1	//next loop
	b loop
cout:
	mov x0,1	//stdout
	mov x8,64	//linux write system call
	svc 0

	mov x0,0
	mov x8,93
	svc 0
.data
instr:	.asciz	"a test string , convert To UPPER case.\n"
outstr:	.fill	255,1,0

　　 

 

ldp,stp,加载或保存128bits数据，使用2个64位寄存器；

 

 

 

 

 

 

 

 

 

标签：CHAPTER,Memories,mov,write,w3,Thanks,x2,x0,内存
From： https://www.cnblogs.com/yangdinshan/p/17641453.html