I was trying to write a nested loop and print a 10×10 grid of dots. And the assembler throws error when I am trying to use PUSH and POP commands in _print subroutine. Is this the right way to do it or am I doing something wrong. Please Help

.equ WIDTH, 10
.equ HEIGHT, 10

.data
DOT: .ascii "."
BLOCK: .ascii "$"
NEW_LINE: .ascii "n"

.text
.global _start
_start:
_renderFrame:
    mov x0, HEIGHT
    mov x1, WIDTH
    bl _height

_height:
    cmp x0, 0
    beq _exit
    sub x0, x0, 1
    bl _width
    ldr x3, =NEW_LINE
    bl _print
    bl _height

_width:
    cmp x1, 0
    beq _height
    sub x1, x1, 1
    ldr x3, =DOT
    bl _print
    bl _width

_print:
    push {x0, x1, x2}
    mov x8, 0x40
    mov x0, 1
    mov x1, x3
    mov x2, 1
    svc 0
    pop {x0, x1, x2}
    ret

_exit:
    mov x8, 0x5d
    mov x0, 0
    svc 0

The error is as below

main.asm: Assembler messages:
main.asm:35: Error: unknown mnemonic `push' -- `push {x0,x1,x2}'
main.asm:41: Error: unknown mnemonic `pop' -- `pop {x0,x1,x2}'

Note: Before I tried to run assembly in macOS but it seems there is not much support articles online regarding macOS. So I am running this code in a Ubuntu Docker container with inbuilt assembler and linker. And the print and exit system calls are working fine.