Write a simple program with Assembler language
Assembler Lab
I will write a simple program to show the output below:
1. This is my code for x86_64 processor with explanation:
.text
.globl _start
start = 0 /* starting value for the loop index */
max = 31 /* loop exits when loop condition is i<max */
_start:
mov $start,%r15 /* loop index */
loop:
mov $0,%rdx /* assign value 0 to rdx (refresh the rdx) */
mov %r15,%rax /* move the loop index to rax (for later divide operation) */
mov $10,%r10 /* move value 10 to r10 register */
div %r10 /* divide rax by r10 (10), places quotient into rax, */
/* remainder into rdx, rdx must be zero before this step */
mov %rax,%r14 /* move the quotient to r14 */
mov %rdx,%r13 /* move the remainder to r13 */
mov $'0',%r12 /* assign ascii '0' to r12 */
cmp $0,%r14 /* compare the quotient with zero */
je skip /* skip if equal */
add %r12,%r14 /* modify the quotient to become the ascii character, */
/* the character will be put into the msg later */
movq $high,%rsi /* location the quotient will be added into */
movb %r14b,(%rsi) /* move the quotient to msg */
skip:
add %r12,%r13 /* modify the remainder to become the ascii character */
movq $low,%rsi /* location the remainder will be added into */
movb %r13b,(%rsi) /* move the remainder to msg */
movq $len,%rdx /* message length */
movq $msg,%rsi /* message location */
movq $1,%rdi /* file descriptor stdout */
movq $1,%rax /* syscall sys_write */
syscall
inc %r15 /* increment index */
cmp $max,%r15 /* see if we're done */
jne loop /* loop if we're not */
mov $0,%rdi /* exit status */
mov $60,%rax /* syscall sys_exit */
syscall
.data
msg: .ascii "Loop: \n" /* the content of msg */
len = . - msg /* length of msg */
high = . - 3 /* define variable high */
low = . - 2 /* define variable low */
2. I also write codes for aarch64 processor:
.text
.globl _start
_start:
mov x28, 0 /* move 0 to x28, loop index */
loop:
mov x27,x28 /* move x28 to x27 for later use */
mov x26,'0' /* move ascii '0' to x26 */
mov x25,10 /* move 10 to x25 for division operation */
udiv x24, x27, x25 /* x27 (loop index) divides by x25 (10), */
/* quotient is in the x24 */
msub x23, x24, x25, x27 /* (x27 - x24 * x25) will be stored in x23, */
/*which is the remainder of x27 divides by x25 */
adr x20,msg /* get the location of msg */
cmp x24,0 /* compare the quotient with 0 */
beq skip /* go to skip if equal */
add x24, x24, x26 /* add x26 to x24, */
/* which make the quotient become ascii value */
strb w24,[x20,6] /* move the quotient ascii value to the msg offset 6 */
skip:
add x23, x23, x26 /* make the remainder become ascii value */
strb w23,[x20,7] /* move the remainder ascii value to msg offset 7 */
mov x0, 1 /* file descriptor: 1 is stdout */
adr x1, msg /* message location (memory address) */
mov x2, len /* message length (bytes) */
mov x8, 64 /* write is syscall #64 */
svc 1 /* invoke syscall */
add x28, x28, 1 /* add 1 to loop index */
cmp x28, 31 /* compare index with 31 */
bne loop /* go to loop if not equal */
mov x0, 0 /* status -> 0 */
mov x8, 93 /* exit is syscall #93 */
svc 0 /* invoke syscall */
.data
msg: .ascii "Loop: \n" /* define msg */
len = . - msg /* length of msg */
.globl _start
start = 0 /* starting value for the loop index */
max = 31 /* loop exits when loop condition is i<max */
_start:
mov $start,%r15 /* loop index */
loop:
mov $0,%rdx /* assign value 0 to rdx (refresh the rdx) */
mov %r15,%rax /* move the loop index to rax (for later divide operation) */
mov $10,%r10 /* move value 10 to r10 register */
div %r10 /* divide rax by r10 (10), places quotient into rax, */
/* remainder into rdx, rdx must be zero before this step */
mov %rax,%r14 /* move the quotient to r14 */
mov %rdx,%r13 /* move the remainder to r13 */
mov $'0',%r12 /* assign ascii '0' to r12 */
cmp $0,%r14 /* compare the quotient with zero */
je skip /* skip if equal */
add %r12,%r14 /* modify the quotient to become the ascii character, */
/* the character will be put into the msg later */
movq $high,%rsi /* location the quotient will be added into */
movb %r14b,(%rsi) /* move the quotient to msg */
skip:
add %r12,%r13 /* modify the remainder to become the ascii character */
movq $low,%rsi /* location the remainder will be added into */
movb %r13b,(%rsi) /* move the remainder to msg */
movq $len,%rdx /* message length */
movq $msg,%rsi /* message location */
movq $1,%rdi /* file descriptor stdout */
movq $1,%rax /* syscall sys_write */
syscall
inc %r15 /* increment index */
cmp $max,%r15 /* see if we're done */
jne loop /* loop if we're not */
mov $0,%rdi /* exit status */
mov $60,%rax /* syscall sys_exit */
syscall
.data
msg: .ascii "Loop: \n" /* the content of msg */
len = . - msg /* length of msg */
high = . - 3 /* define variable high */
low = . - 2 /* define variable low */
2. I also write codes for aarch64 processor:
.text
.globl _start
_start:
mov x28, 0 /* move 0 to x28, loop index */
loop:
mov x27,x28 /* move x28 to x27 for later use */
mov x26,'0' /* move ascii '0' to x26 */
mov x25,10 /* move 10 to x25 for division operation */
udiv x24, x27, x25 /* x27 (loop index) divides by x25 (10), */
/* quotient is in the x24 */
msub x23, x24, x25, x27 /* (x27 - x24 * x25) will be stored in x23, */
/*which is the remainder of x27 divides by x25 */
adr x20,msg /* get the location of msg */
cmp x24,0 /* compare the quotient with 0 */
beq skip /* go to skip if equal */
add x24, x24, x26 /* add x26 to x24, */
/* which make the quotient become ascii value */
strb w24,[x20,6] /* move the quotient ascii value to the msg offset 6 */
skip:
add x23, x23, x26 /* make the remainder become ascii value */
strb w23,[x20,7] /* move the remainder ascii value to msg offset 7 */
mov x0, 1 /* file descriptor: 1 is stdout */
adr x1, msg /* message location (memory address) */
mov x2, len /* message length (bytes) */
mov x8, 64 /* write is syscall #64 */
svc 1 /* invoke syscall */
add x28, x28, 1 /* add 1 to loop index */
cmp x28, 31 /* compare index with 31 */
bne loop /* go to loop if not equal */
mov x0, 0 /* status -> 0 */
mov x8, 93 /* exit is syscall #93 */
svc 0 /* invoke syscall */
.data
msg: .ascii "Loop: \n" /* define msg */
len = . - msg /* length of msg */
