I’ve been playing with ARMv8 Assembly and NCurses the past couple days with decent success. The following code does exactly what it is supposed to. Centers a window and draws an ‘o’ inside.

.global main

.section .text
.align 2

main:
    ldr x0, =termtitle
    bl printf
    
    bl initscr
    mov x0, #0
    bl curs_set
    bl refresh
    
    adrp x9, court
    add x9, x9, :lo12:court
    
    mov x0, #1
    mov x1, #0x5413
    ldr x2, =termsize
    mov x8, #29
    svc #0
    
    ldr x19,=termsize
    
    mov x0, #10
    mov x1, #30 
    ldr w4, [x19,#0]
    mov x5, #2      
    udiv w2, w4, w5
    sub x2, x2, #5
    ldr w4, [x19,#2]
    mov x5, #2
    udiv w3, w4, w5
    sub x3, x3, #15
    bl newwin       
    str x0, [x9] 
    
    ldr x0, [x9]

    sub sp, sp, #16
    str x0, [sp]

    mov x1, #0
    mov x2, #0
    bl box

    
    adrp x9, court
    add x9, x9, :lo12:court
    
    ldr x0, [x9]
    mov x1, #5
    mov x2, #5
    ldr x3, =prototype
    bl mvwprintw
    
    
    ldr x0, [sp]
    add sp, sp, #16
    
    bl wrefresh

    bl getch
    bl endwin

    mov x8, 93
    mov x0, 0
    svc 0

    
    

.section .data
termsize: .skip 4
termtitle: .asciz "33]0;ARMv8 - Ncurses Bouncing Ball07"
court:  .quad 0
ball:
    .byte 0
    .byte 0
    .byte 0x4F
prototype: .asciz "o"

The problem comes as I try to tidy things up. When I place the following syscall into its own subroutine:

GetTermSize:
    mov x0, #1
    mov x1, #0x5413
    ldr x2, =termsize
    mov x8, #29
    svc #0

And then attempt to call it with bl, my program declares Illegal Instruction.