debug.rom: re-implement displaying flags and returning to code

rom/debug.asm

@@ -72,6 +72,18 @@ init:	push ds
 	pop ds
 	retf
 
+crlf:	xor bx, bx
+	mov ax, 0x0e0a
+	int 0x10
+	mov al, 0x0d
+	int 0x10
+	ret
+
+space:	xor bx, bx
+	mov ax, 0x0e20
+	int 0x10
+	ret
+
 print16:
 	; setup bx and ah for int 10h call
 	xor bx, bx
@@ -97,7 +109,7 @@ print16:
 	ret
 
 printregs:
-	mov cx, 14
+	mov cx, 13
 	xor bx, bx
 	mov ah, 0x0e
 	mov si, reg_ax
@@ -112,10 +124,24 @@ printregs:
 	lodsw
 	mov dx, ax
 	call print16
-	mov al, ' '
-	int 0x10
+	call space
 	pop cx
 	loop .loop
+
+	mov dx, [reg_fl]
+	mov si, fnames
+	mov cx, 16
+.floop:	lodsb
+	cmp al, '+'
+	je .fskip
+	test dx, 0x8000
+	jnz .fprnt
+	mov al, '-'
+.fprnt: int 0x10
+.fskip: shl dx, 1
+	loop .floop
+	call space
+	call crlf
 	ret
 
 int3entry:
@@ -147,15 +173,40 @@ int3entry:
 	mov es, ax
 	mov ss, ax
 	mov sp, (stack+stacksize)
+	call crlf
 
 	call printregs
 
-hlt:	hlt
-	jmp hlt
+return:	; restore stack pointer
+	mov ss, [reg_ss]
+	mov sp, [reg_sp]
+	; push flags, CS and IP
+	mov ax, [reg_fl]
+	push ax
+	mov ax, [reg_cs]
+	push ax
+	mov ax, [reg_ip]
+	push ax
+	; restore GPR
+	mov ax, [reg_ax]
+	mov cx, [reg_cx]
+	mov dx, [reg_dx]
+	mov bx, [reg_bx]
+	mov bp, [reg_bp]
+	mov si, [reg_si]
+	mov di, [reg_di]
+	; restore segment registers
+	mov es, [reg_es]
+	mov ds, [reg_ds]
+	; final jump back
+	iret
 
 names:	db "AXCXDXBXSPBPSIDI"
 	db "DSESSSCSIPFL"
 
+fnames:	db "++++ODIT"
+	db "SZ+A+P+C"
+
 codeend:
 
 reg_ax:	dw 0