From f7d7f48026d7cb0ce7801ab2ffee6ed424bce45a Mon Sep 17 00:00:00 2001
From: Nero <41307858+nero@users.noreply.github.com>
Date: Sat, 1 Jan 2022 21:22:37 +0000
Subject: [PATCH] Implement syscall interface and version data

---
 src/@rdos.asm   | 145 +++++++++++++++++++++++++-----------------------
 src/farptr.inc  |  46 ---------------
 src/version.inc |   2 +
 3 files changed, 79 insertions(+), 114 deletions(-)
 delete mode 100644 src/farptr.inc
 create mode 100644 src/version.inc

diff --git a/src/@rdos.asm b/src/@rdos.asm
index cd96907..0afc174 100644
--- a/src/@rdos.asm
+++ b/src/@rdos.asm
@@ -1,6 +1,21 @@
 	org 0x700
 cseg	equ 0x0
-	jmp init
+
+%include "version.inc"
+
+	jmp _entry
+banner	db "RDOS KERNEL 1.0", 0x0A, 0x0D, '$', 0x1A
+_entry	call .l01
+.l01	pop ax
+	sub ax, .l01
+	mov cl, 4
+	shr ax, cl
+	mov cx, cs
+	add cx, ax
+	push cx
+	mov ax, start
+	push ax
+	retf
 
 ;;; Character I/O
 
@@ -138,10 +153,15 @@ gets	mov si, dx
 	call putc
 	ret
 
+;;; System functions
+
+	; Return OS version from version.inc
+ver	mov bx, bdosver | 0x1000
+	ret
+
 ;;; Disk i/o
 
 %include "bpb.inc"
-%include "farptr.inc"
 
 	; dflags bitfields
 DRVLOG	equ 0x01 ; bit 0 - drive logged in (see drvnum)
@@ -150,23 +170,8 @@ DRVEXT	equ 0x04 ; bit 2 - EBIOS supported
 DIRTY	equ 0x08 ; bit 3 - dskbuf dirty
 DRVCHS	equ 0x10 ; bit 4 - CHS geometry known
 
-	align 16
-	; IBM Interrupt Sharing Protocol structure
-i13isp	jmp short int13i
-	dw 0,0xFFFF
-	dw 0x424B
-	db 0
-	iret
-	align 16
-
-	; Entry point when user program calls int13h
-	; TODO: flush buffer and log out drive
-int13i	call int13
-	iret
-
 	; Wrapper around int 13h
-int13	pushf
-	call far [i13isp+2]
+int13	int 0x13
 	; TODO: on error: reset & retry
 	; TODO: record errors
 	; TODO: multi-track reading
@@ -209,10 +214,10 @@ getprm	test byte [dflags], DRVEXT
 	test ax, ax
 	jz .ret
 	; copy BIOS dpt table over ours
-	mov dx, dpt
-	mov bx, di
-	mov cx, 11
-	call lodfar
+	;mov dx, dpt
+	;mov bx, di
+	;mov cx, 11
+	;call lodfar
 .ret	ret
 
 	; select a drive for io
@@ -379,14 +384,13 @@ flush	test word [cs:dflags], DIRTY
 	; Sector number is read from [drvseek]
 diskio	mov cl, 1 ; read len
 	; DS := ES := CS
-	call rstseg
+	mov ds, [cs:dseg]
 	; check if ebios supported
 	test word [dflags], DRVEXT
 	jz .noext
 	; set up regs for ebios call
-	mov ax, cx
+	xchg ax, cx
 	or ah, 0x40
-	mov si, dap
 	jmp .do
 	; check if we can skip controller reset
 .noext	test word [dflags], DRVCTL
@@ -419,15 +423,19 @@ diskio	mov cl, 1 ; read len
 	; shuffle values around for bios
 	xchg ax, cx
 	xchg dh, dl
-	mov bx, dskbuf
 .do	mov dl, [biosnum]
 	; ah: subfunction selected via cx previously
 	; al: 1 = reading 1 sector
 	; cx: sector and cylinder number
 	; dh: head number
 	; dl: drive number
-	; bx: offset to disk buffer
+	push es
+	push si
+	mov si, dap
+	les bx, [si+4]
 	call int13
+	pop si
+	pop es
 	jc .err
 	; clear dirty flag on success
 	and word [dflags], ~DIRTY
@@ -439,39 +447,6 @@ diskio	mov cl, 1 ; read len
 	stc
 	ret
 
-init	mov ax, cs
-	; boot failure if loaded wrong
-	cmp ax, cseg
-	je $+4
-	int 0x18
-	call rstseg
-	; fetch current DPT
-	les bx, [4*0x1E]
-	mov dx, dpt
-	mov cx, 11
-	call lodfar
-	; set interrupt vector
-	mov word [4*0x1E], dpt
-	mov word [4*0x1E+2], ds
-	; save int 13 handler
-	les bx, [4*0x13]
-	mov [i13isp+2], bx
-	mov [i13isp+4], es
-	; install ours
-	mov word [4*0x13], int13i
-	mov [4*0x13+2], cs
-
-	; install int21h handler
-	mov word [4*0x21], int21h
-	mov [4*0x21+2], cs
-
-	mov dl, 0x36
-	mov ah, 2
-	int 0x21
-
-halt	hlt
-	jmp halt
-
 ;;; Export functions as syscalls
 ; SP, BP, SI, DI and ES must be preserved by kernel code
 ; DL, DX or DS:DX is input argument from prog
@@ -494,7 +469,9 @@ intE0h	push bx
 	; bx = syscall number
 	; stack must be -> BX IP CS FL
 	; for return to prog
-sysc	add bx, bx
+sysc	sti
+	cld
+	add bx, bx
 	mov bx, [cs:bx+stab]
 	test bh, srw >> 8 ; fork off bx returns
 	jnz .l02
@@ -537,6 +514,38 @@ sysc	add bx, bx
 	pop dx
 	ret
 
+start	xor ax, ax
+	mov ds, ax
+
+	; install int20h handler
+	mov word [4*0x20], start
+	mov [4*0x20+2], cs
+	; install int21h handler
+	mov word [4*0x21], int21h
+	mov [4*0x21+2], cs
+	; install intE0h handler
+	mov word [4*0xE0], intE0h
+	mov [4*0xE0+2], cs
+
+	mov ax, cs
+	mov ds, ax
+	mov [dseg], ax
+
+	; print banner
+	mov dx, banner
+	call puts
+
+	; read cmdline
+	mov dl, '>'
+	call putc
+	mov dx, inbuf
+	mov byte [inbuf], 72
+	call gets
+
+halt	sti
+	hlt
+	jmp halt
+
 section .rodata
 
 	; syscall table
@@ -549,10 +558,10 @@ stab	dw 0 ; 0 reboot
 	dw 0 ; 6 direct console i/o
 	dw 0 ; 7 read i/o byte
 	dw 0 ; 8 get i/o byte
-	dw 0 ; 9 string output
-	dw 0 ; 10 string input
+	dw puts ; 9 string output
+	dw gets ; 10 string input
 	dw 0 ; 11 console status
-	dw 0 ; 12 get version number
+	dw ver ; 12 get version number
 	dw 0 ; 13 reset disks
 	dw 0 ; 14 set drive
 	dw 0 ; 15 open file
@@ -587,7 +596,8 @@ section .data
 
 dap	db 0x10, 0
 	dw 1
-	dw dskbuf, cseg
+	dw dskbuf
+dseg	dw 0
 drvseek	dw 0,0,0,0
 
 	; bit 0 (1) - drive logged in (see drvnum)
@@ -603,9 +613,6 @@ drvnum	resb 1
 	; number, just for bios
 biosnum	resb 1
 
-	; DPT tables for 4 floppy drives
-dpt	resb 4*14
-
 ; Information for logged in drive
 drvss	resb 1 ; sector size, 2^(7+n) bytes
 drvcs	resb 1 ; cluster size, 2^(7+n) bytes
@@ -622,3 +629,5 @@ drvfn	resb 2 ; sectors per fat table
 	; disk buffer for I/O operations
 	alignb 2
 dskbuf	resb 1024
+
+inbuf	resb 128
diff --git a/src/farptr.inc b/src/farptr.inc
deleted file mode 100644
index b98729c..0000000
--- a/src/farptr.inc
+++ /dev/null
@@ -1,46 +0,0 @@
-	; reset segments
-rstseg	mov ax, cs
-	mov ds, ax
-	mov es, ax
-	ret
-
-	; copy to far memory
-	; IN	es:bx	far memory ptr (preserved)
-	;	ds:dx	local ptr (preserved)
-	;	cx	number of bytes to transfer
-	; OUT	cx	set to zero
-	;	si & di	trashed
-stofar	mov si, dx
-	mov di, bx
-	rep movsb
-	ret
-
-	; copy from far memory
-	; IN	es:bx	far memory ptr (preserved)
-	;	ds:dx	local ptr (preserved)
-	;	cx	number of bytes to copy
-	; OUT	cx	set to zero
-	;	si & di	trashed
-lodfar	call swpds
-	mov si, bx
-	mov di, dx
-	rep movsb
-
-	; exchange es and ds
-swpds	push ds
-	push es
-	pop ds
-	pop es
-	ret
-
-	; normalize ptr in ds:dx
-norm	mov ax, ds
-	mov cl, 4
-	push dx
-	ror dx, cl
-	and dh, 0xF
-	add ax, dx
-	mov ds, ax
-	pop dx
-	and dx, 0xF
-	ret
diff --git a/src/version.inc b/src/version.inc
new file mode 100644
index 0000000..9378088
--- /dev/null
+++ b/src/version.inc
@@ -0,0 +1,2 @@
+bdosver	equ 0x10 ; CP/M 1.0
+bdosrev	equ 0