rdos/kernel/debug.asm

; Names for words in debug frame
; Two characters per word, 14 words total
debug_frame_names:
  ; general-purpose registers
  db "AXBXCXDXSPBPSIDI"
  ; extra registers
  db "DSESSSIPCSFL"

; Names for bits in debug_frame+26 (FL/Flags register)
; One character per bit, 16 bits total
debug_frame_flags:
  db "++++ODIT"
  db "SZ+A+P+C"

; Print a single register from the frame
; in	SI	frame offset for register
debug_frame_register_print:
  mov bx, debug_frame_names
  mov al, [cs:bx+si] ; first name char load
  call putc
  mov al, [cs:bx+si+1] ; second name char load
  call putc
  mov al, '='
  call putc
  mov ax, [ss:bp+si] ; value load
  ; prepare call to print_number
  push bx
  push cx
  mov bx, 0x0010
  mov cx, 3
  call print_number_padded
  pop cx
  pop bx
  mov al, ' '
  call putc
  ret

debug_frame_print:
  mov si, 0
  mov cx, 8
.reg1loop:
  call debug_frame_register_print
  add si, 2
  loop .reg1loop

  mov dx, [ss:bp+26]
  mov di, debug_frame_flags
  mov cx, 0x0010
.flag_loop:
  mov al, [cs:di]
  inc di
  cmp al, '+'
  je .next
  test dx, 0x8000
  jnz .write
  mov al, '-'
.write:
  call putc
.next:
  sal dx, 1
  loop .flag_loop

  call printf
  db 0x0A, 0x0D, 0

  mov si, 16
  mov cx, 3
.reg2loop:
  call debug_frame_register_print
  add si, 2
  loop .reg2loop

  mov ax, [bp+24]
  mov bx, 0x0010
  mov cx, 3
  call print_number_padded

  mov al, ':'
  call putc

  mov ax, [bp+22]
  mov bx, 0x0010
  mov cx, 3
  call print_number_padded

  call printf
  db 0x0A, 0x0D, 0

  ret

; this prints registers
; expect to be called as interrupt routine
isr_debug:
  push ss
  push es
  push ds
  push di
  push si
  push bp
  push sp
  push dx
  push cx
  push bx
  push ax

  mov bp, sp
  mov [bp+08], bp
  add WORD [bp+08], 28

  call printf
  db 0x0A, 0x0D, 0

  call debug_frame_print

  pop ax
  pop bx
  pop cx
  pop dx
  pop bp ; sp to be ignored
  pop bp
  pop si
  pop di
  pop ds
  pop es
  pop ss
  iret