From 8aafa98c6aa016f1fe53d45d0ba219f3dc8ea337 Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Sun, 5 May 2019 11:18:36 +0000
Subject: [PATCH] Revamp debugger, including support for printing padded
 numbers

---
 kernel/debug.asm | 119 ++++++++++++++++++++++++++++++++++++++---------
 lib/printf.inc   |  47 ++++++++++++++-----
 2 files changed, 132 insertions(+), 34 deletions(-)

diff --git a/kernel/debug.asm b/kernel/debug.asm
index 703e948..f5e6620 100644
--- a/kernel/debug.asm
+++ b/kernel/debug.asm
@@ -1,3 +1,93 @@
+; 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:
@@ -13,41 +103,24 @@ isr_debug:
   push bx
   push ax
 
-  call printf
-  db "AX=%X BX=%X CX=%X DX=%X", 0x20
-  db "SP=%X BP=%X SI=%X DI=%X", 0x0A, 0x0D
-  db "DS=%X ES=%X SS=%X IP=%X CS=%X", 0x20, 0
-
   mov bp, sp
-  mov bx, [ss:bp+26]
-  mov si, .flags
-  mov cx, 0x0010
-.loop:
-  mov al, [cs:si]
-  inc si
-  test bx, 0x8000
-  jnz .write
-  mov al, '-'
-.write:
-  sal bx, 1
-  call putc
-  loop .loop
+  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 sp
+  pop bp ; sp to be ignored
   pop bp
   pop si
   pop di
   pop ds
   pop es
   pop ss
-  iret
-.flags:
-  ; 16 letters for each bit in flags register
-  db "++++ODITSZ+A+P+C"
\ No newline at end of file
+  iret
\ No newline at end of file
diff --git a/lib/printf.inc b/lib/printf.inc
index f2b9ad4..9584c70 100644
--- a/lib/printf.inc
+++ b/lib/printf.inc
@@ -48,24 +48,46 @@ printf:
   call print_string
   jmp .loop
 
+; converts a integer to ascii
+; in    ax      input integer
+;       bx      base
+;	cx	minimum number of digits
+; out   bx      garbled
+;       dx      garbled
+print_number_padded:
+  xor dx, dx
+  div bx
+  push dx
+  dec cx
+  jz .nopad
+  call print_number_padded
+  jmp print_number.end
+.nopad:
+  call print_number
+  jmp print_number.end
+
+; converts a integer to ascii
+; in	ax	input integer
+;	bx	base
+; out	bx	garbled
+;	dx	garbled
 print_number:
   xor dx, dx
   div bx ; ax = dx:ax / 10, dx = dx:ax % 10
-  and ax, ax
-  jz .print
   push dx
+  and ax, ax
+  jz .end
   call print_number
-  pop dx
-.print:
-  mov al, dl
-  add al, 0x30
-  cmp al, 0x3A
-  jl .noadj
-  add al, 0x07
-.noadj:
+.end:
+  pop bx
+  xor bh, bh
+  add bx, print_chars
+  mov al, [cs:bx]
   call putc
   ret
 
+; putc's a string
+; in	DS:AX	null-terminated string
 print_string:
   push si
   mov si, ax
@@ -77,4 +99,7 @@ print_string:
   jmp .loop
 .end:
   pop si
-  ret
\ No newline at end of file
+  ret
+
+print_chars:
+  db "0123456789ABCDEF"
\ No newline at end of file