add two numbers in ARM assembly

add.s

.text
.equ inputBufferSize, 100
.global main
main:
    ldr r0, =inputString
    bl get_input
    bl parseNumber
    ldr r1, =number1
    str r0, [r1]

    ldr r0, =inputString
    bl get_input
    bl parseNumber
    ldr r1, =number2
    str r0, [r1]

    ldr r2, =number1
    ldr r2, [r2]
    ldr r3, =number2
    ldr r3, [r3]

    add r1, r2, r3
    ldr r0, =numberFormat
    bl printf

    mov r7, #1
    swi 0

parseNumber:
    push {r1-r4, lr}
    mov r3, r0
    bl length
    mov r2, r0
    sub r2, #1
    mov r1, r3
    mov r4, #1 @ place value
    mov r5, #0 @ value
    .parseNumber_loop:
        ldrb r0, [r1, r2]
        push {r1-r3}
        sub r1, r0, #'0'
        mul r2, r4, r1
        add r5, r2
        mov r1, #10
        mul r2, r4, r1
        mov r4, r2
        pop {r1-r3}
        sub r2, #1
        cmp r2, #0
        bge .parseNumber_loop
    mov r0, r5
    pop {r1-r4, lr}
    mov pc, lr

length:
    push {r1-r3, lr}
    mov r3, r0
    .length_loop:
        ldrb r1, [r0, #1]!
        cmp r1, #0
        bne .length_loop
    sub r0, r3
    pop {r1-r3, lr}
    mov pc, lr    


get_input:
    push {r0-r7, lr}
    mov r1, r0
    mov r0, #0
    mov r2, #inputBufferSize
    mov r7, #3
    swi 0

    mov r0, r1
    mov r2, r0
    bl length
    sub r1, r0, #1
    mov r0, #0
    strb r0, [r2, r1]

    pop {r0-r7, lr}
    mov pc, lr

.data
inputString: .space inputBufferSize
inputText: .asciz "12345"
numberFormat: .asciz "%d\n"

number1: .word 0
number2: .word 0