From fc1aa47039da8e6abc7c9b5ddc7199cc460573e6 Mon Sep 17 00:00:00 2001
From: Ain <41307858+nero@users.noreply.github.com>
Date: Mon, 18 May 2020 20:05:06 +0200
Subject: [PATCH] debug: Implement parsing of register names

---
 Makefile        |   2 +-
 debug/names.asm |  10 ++++
 debug/parse.asm |  58 +++++++++++++++++++++
 rom/debug.asm   | 131 ++++++++++++++++++++++++++----------------------
 4 files changed, 140 insertions(+), 61 deletions(-)
 create mode 100644 debug/names.asm
 create mode 100644 debug/parse.asm

diff --git a/Makefile b/Makefile
index 38adf3a..1380c71 100644
--- a/Makefile
+++ b/Makefile
@@ -65,7 +65,7 @@ fate.bs: boot/fat.asm
 	$(NASM) $(NASM_ARGS) -DFAT16 -DLBA -DLARGE -o $@ $<
 
 # BIOS option roms
-%.rom: rom/%.asm utils/fix-rom
+%.rom: rom/%.asm %/*.asm utils/fix-rom
 	$(NASM) $(NASM_ARGS) -o $@ $< && utils/fix-rom $@
 
 fdimage.img: fat1.bs $(DISTFILES)
diff --git a/debug/names.asm b/debug/names.asm
new file mode 100644
index 0000000..8633faa
--- /dev/null
+++ b/debug/names.asm
@@ -0,0 +1,10 @@
+rnames:	; general purpose regs
+	db "AXCXDXBXSPBPSIDI"
+	; segment regs
+	db "ESCSSSDS"
+	; special regs
+	db "IPFL"
+fnames:	; control flags
+	db "++++ODIT"
+	; status flags
+	db "SZ+A+P+C"
diff --git a/debug/parse.asm b/debug/parse.asm
new file mode 100644
index 0000000..a99f9e4
--- /dev/null
+++ b/debug/parse.asm
@@ -0,0 +1,58 @@
+	; IN	DS:SI	remaining unparsed string
+	;	CS:DI	error message
+parse_error:
+	push si
+	mov si, di
+	call putcs
+	mov al, ':'
+	call putc
+	mov al, ' '
+	call putc
+	pop si
+	call putds
+	jmp crlf
+
+eat_whitespace:
+	; peek on next char
+	mov al, [si]
+	; ES := CS
+	push es
+	push cs
+	pop es
+	; string search
+	mov di, .chars
+	mov cx, 4
+	scasb
+	; restore bss segment
+	pop es
+	jne .ret
+	inc si
+	jmp eat_whitespace
+.chars:	db 0x09, 0x0A, 0x0D, 0x20
+.ret:	ret
+
+	; IN:	DS:SI	string to read
+	; OUT:	CF set	if no match
+	;	BX	register number * 2 if CF clear
+eat_register:
+	push si
+	push es
+	lodsw
+	and ax, 0xDFDF
+	; ES := CS
+	push cs
+	pop es
+	mov di, rnames
+	mov cx, 14
+	repne scasw
+	pop es
+	jne .fail
+	pop bx
+	mov bx, di
+	sub bx, (rnames+2)
+	clc
+	ret
+.fail:	pop si
+	stc
+	ret
+.emsg:	db "Not a register name", 0
diff --git a/rom/debug.asm b/rom/debug.asm
index 8424bb3..7d74f0e 100644
--- a/rom/debug.asm
+++ b/rom/debug.asm
@@ -6,8 +6,7 @@ bssvec:	equ 0xB6
 
 	db 0x55, 0xAA
 	db 0x00
-	jmp init
-	nop
+	jmp near init
 
 	times (0x18 - ($-$$)) db 0
 	dw 0
@@ -58,6 +57,8 @@ init:	push ds
 	pop ds
 	retf
 
+	%include "debug/parse.asm"
+
 	; Print AL
 space:	mov al, ' '
 putc:	xor bx, bx
@@ -65,17 +66,21 @@ putc:	xor bx, bx
 	int 0x10
 	ret
 
-	; Print CS:SI
-puts:	push ds
+	; Print code string CS:SI
+putcs:	push ds
 	push cs
 	pop ds
-.loop:	lodsb
+	call putds
+	pop ds
+	ret
+
+	; Print data string DS:SI
+putds:	lodsb
 	test al, al
 	jz .ret
 	call putc
-	jmp .loop
-.ret:	pop ds
-	ret
+	jmp putds
+.ret:	ret
 
 crlf:	mov al, 0x0A
 	call putc
@@ -106,6 +111,47 @@ print16:
 .noadj:	int 0x10
 	ret
 
+getc:	xor ax, ax
+	int 0x16
+	test al, al
+	jz getc
+	ret
+
+read:	mov di, cmdbuf
+.loop:	call getc
+	cmp al, 0x03
+	je .can
+	cmp al, 0x0D
+	je .enter
+	cmp al, 0x08
+	je .bs
+	cmp di, cmdbuf+cmdlen-1
+	jnc .loop
+	stosb
+	mov ah, 0x0e
+	xor bx, bx
+	int 0x10
+	jmp .loop
+	ret
+.bs:	cmp di, cmdbuf
+	jbe .loop
+	xor bx, bx
+	mov ax, 0x0e08
+	int 0x10
+	mov al, 0x20
+	int 0x10
+	mov al, 0x08
+	int 0x10
+	dec di
+	jmp .loop
+.can:	xor al, al
+	stosb
+	stc
+	ret
+.enter:	xor al, al
+	stosb
+	ret
+
 int3entry:
 	; save DS and load bss segment from IVT
 	push ds
@@ -143,7 +189,7 @@ int3entry:
 
 loop:	; show prompt
 	mov al, '-'
-	int 0x10
+	call putc
 	; read data
 	call read
 	pushf
@@ -179,54 +225,11 @@ return:	; restore stack pointer
 	; final jump back
 	iret
 
-names:	; general purpose regs
-	db "AXCXDXBXSPBPSIDI"
-	; segment regs
-	db "ESCSSSDS"
-	; special regs
-	db "IPFL"
-fnames:	; control flags
-	db "++++ODIT"
-	; status flags
-	db "SZ+A+P+C"
+	%include "debug/names.asm"
 
-getc:	xor ax, ax
-	int 0x16
-	test al, al
-	jz getc
-	ret
-
-read:	mov di, cmdbuf
-.loop:	call getc
-	cmp al, 0x03
-	je .can
-	cmp al, 0x0D
-	je .enter
-	cmp al, 0x08
-	je .bs
-	cmp di, cmdbuf+cmdlen
-	jnc .loop
-	stosb
-	mov ah, 0x0e
-	xor bx, bx
-	int 0x10
-	jmp .loop
-	ret
-.bs:	cmp di, cmdbuf
-	jbe .loop
-	xor bx, bx
-	mov ax, 0x0e08
-	int 0x10
-	mov al, 0x20
-	int 0x10
-	mov al, 0x08
-	int 0x10
-	dec di
-	jmp .loop
-.can:	stc
-.enter:	ret
-
-runcmd:	mov al, [cmdbuf]
+	; Expects DI to mark end of command
+runcmd:	mov si, cmdbuf
+	lodsb
 	cmp al, 'g'
 	je cmd_g
 	cmp al, 'r'
@@ -235,12 +238,12 @@ runcmd:	mov al, [cmdbuf]
 	je cmd_t
 	cmp al, '?'
 	je cmd_?
-	mov al, '?'
+cerr:	mov al, '?'
 	call putc
 	jmp crlf
 
 cmd_?:	mov si, .txt
-	jmp puts
+	jmp putcs
 .txt:	db "g       Go", 0x0A, 0x0D
 	db "r       Print register values", 0x0A, 0x0D
 	db "t       Single-Step", 0x0A, 0x0D
@@ -249,7 +252,15 @@ cmd_?:	mov si, .txt
 cmd_g:	and word [reg_fl+1], 0xfe
 	jmp return
 
-cmd_r:	jmp printregs
+cmd_r:	cmp di, si
+	je printregs
+	call eat_register
+	jc .err
+	mov dx, si
+	call print16
+	ret
+.err:	mov di, eat_register.emsg
+	jmp parse_error
 
 cmd_t:	or word [reg_fl+1], 0x03
 	jmp return
@@ -260,7 +271,7 @@ printregs:
 	mov ah, 0x0e
 	mov si, reg_ax
 .loop:	push cx
-	mov dx, [cs:si+names]
+	mov dx, [cs:si+rnames]
 	lodsw
 	call printreg
 	pop cx