Add hexdump for kernel

kernel/dump.asm

@@ -0,0 +1,85 @@
+; print a word
+; in: ax
+print16:
+  xchg ah,al
+  call print8
+  xchg ah,al
+
+; print a byte
+; in: al
+print8:
+  push ax ; avoid destroying ah
+  push bx
+  xor bx, bx
+  aam 16 ; high nibble moved into ah, low nibble into al
+  add ax, 0x3030
+  push ax
+  xchg al, ah
+  call .nib
+  pop ax
+  call .nib
+  pop bx
+  pop ax
+  ret
+.nib:
+  cmp al, 0x3a
+  jl .out
+  add al, 0x07
+.out:
+  mov dl, al
+  call console_output
+  ret
+
+dump:
+  push ax
+  push cx
+  push dx
+  push bx
+  mov dl, 0x0A
+  call console_output
+  mov dl, 0x0D
+  call console_output
+  mov cx, 4
+.loop_line:
+  push cx
+  push bx
+  mov ax, bx
+  call print16
+  mov dl, ':'
+  call console_output
+  mov dl, ' '
+  call console_output
+  mov cx, 0x8
+.loop_bin:
+  mov ax, [bx]
+  xchg al, ah
+  inc bx
+  inc bx
+  call print16
+  mov dl, ' '
+  call console_output
+  loop .loop_bin
+  pop bx
+  mov cx, 0x10
+.loop_ascii:
+  mov dl, '.'
+  cmp byte [bx], 0x20
+  jc .print
+  cmp byte [bx], 0x80
+  jnc .print
+  mov dl, [bx]
+.print:
+  inc bx
+  call console_output
+  loop .loop_ascii
+  pop cx
+  mov dl, 0x0A
+  call console_output
+  mov dl, 0x0D
+  call console_output
+  loop .loop_line
+  pop bx
+  pop dx
+  pop cx
+  pop ax
+  ret