Single out PSP management

boot/kernel.asm

@@ -3,7 +3,6 @@
 
 %include	"inc/bpb.asm"
 %include	"inc/mbr.asm"
-%include	"inc/fcb.asm"
 %include	"inc/dpt.asm"
 
 init:		cli
@@ -56,10 +55,6 @@ relinit:	; print banner
 		sub dl, (0x80-2)
 .k:		call setdd
 
-		mov ah, 2
-		mov dl, 0x37
-		int 0x21
-
 		mov dx, testfcb
 		mov ah, 0xF
 		int 0x21
@@ -68,6 +63,7 @@ restart:
 hlt:		hlt
 		jmp hlt
 
+%include	"kernel/psp.asm"
 %include	"kernel/syscall.asm"
 %include	"kernel/char.asm"
 %include	"kernel/fcb.asm"

inc/fcb.asm

@@ -1,2 +0,0 @@
-FCBDEN:	equ 23 ; directory entry
-FCBSIZ:	equ 30

kernel/fcb.asm

@@ -1,35 +1,27 @@
+
+; FCB layout
+; 1 byte drive (0=default, 1=A:, 2=B:, ...)
+; 8.3 filename
+; 8.3 filename for rename
+
+FCBDEN:	equ 23 ; WORD directory entry number
+FCBSIZ:	equ 30
+
 section .text
 
-		; set default drive for current process
-		; IN	dl	drive number
-setdd:		push ds
-		mov ds, [cs:curpsp]
-		mov [PSPDD], dl
-		pop ds
-		ret
-
-		; get default drive for current process
-		; OUT	al	drive number
-getdd:		push ds
-		mov ds, [cs:curpsp]
-		mov al, [PSPDD]
-		pop ds
-		ret
-
 		; auto-complete drive field in fcb
-		; IN	ds:dx	far ptr FCB
+		; IN	es:bx	far ptr FCB
-		; OUT	si	copy of dx
+		; OUT	si	copy of bx
-fixfcb:		mov si, dx
+fixfcb:		cmp byte [es:bx], 0
-		cmp byte [si], 0
 		jne .ret
 		call getdd
 		inc dl
-		mov byte [si], dl
+		mov byte [es:bx], dl
-.ret:		mov dx, si
+.ret:		ret
-		ret
 
 		; Load root directory entry
 		; IN	ax	number of directory entry
+		; OUT	cs:si	ptr to directory entry
 lddir:		push ax
 		mov cl, 4
 		shr ax, cl
@@ -43,33 +35,10 @@ lddir:		push ax
 		add si, dskbuf
 		ret
 
-		; find next file
+		; find first matching file
-fnfile:		mov ax, [es:bx+FCBDEN]
+		; IN	ES:BX	input fcb
-		inc word [es:bx+FCBDEN]
+fndfst:		
-		; bail out if we are at end of dir
-		cmp ax, [bpb+BPBRDE]
-		jnc .err
-		; load entry and first byte
-		push bx
-		call lddir
-		pop bx
-		; next if hidden, dir or vol label
-		test byte [si+0x0B], 0xDA
-		jnz fnfile
-		; bail out if end of dir
-		mov al, [si]
-		cmp al, 0
-		je .err
-		; next if deleted entry
-		cmp al, 0xE5
-		je fnfile
-		clc
-		ret
-.err:		stc
-		ret
 
-		; Open file using FCB
+
-		; IN	DS:DX	far ptr to FCB
+open:
-open:		call fixfcb
-		int 3
 		ret

kernel/psp.asm

@@ -0,0 +1,62 @@
+; Program segment prefix headers and constants
+
+section .bss
+
+curpsp:	resw 1
+
+absolute 0
+
+	resb 2 ; ret 0 exit
+	resb 2 ; next unusable segment
+PSPDD:	resb 1 ; BYTE default drive
+	; CP/M entry point
+	resb 1 ; instruction byte
+	resw 1 ; usable length of segment (needs to be here for compata)
+	resb 4 ; opcodes to call us
+
+	; saved userdata
+PSPAX:	resw 1
+PSPCX:	resw 1
+	; SS:SP
+PSPSP:	resw 1
+PSPSS:	resw 1
+	; DS:DX
+PSPDX:  resw 1
+PSPDS:	resw 1
+	; ES:BX
+PSPBX:	resw 1
+PSPES:	resw 1
+
+PSPDTA:	resd 1 ; DWORD ptr to disk transfer area
+
+section .text
+
+	; set default drive for current process
+	; IN	dl	drive number
+setdd:	push es
+	mov es, [curpsp]
+	mov [es:PSPDD], dl
+	pop es
+	ret
+
+	; get default drive for current process
+	; OUT	al	drive number
+getdd:	push es
+	mov es, [curpsp]
+	mov al, [es:PSPDD]
+	pop es
+	ret
+
+	; set DTA ptr
+	; IN	es:bx	far ptr
+setdta:	push es
+	mov ds, [curpsp]
+	mov [PSPDTA], bx
+	mov [PSPDTA+2], es
+	pop es
+
+	; get DTA ptr
+	; OUT	es:bx	far ptr
+getdta:	mov es, [curpsp]
+	les bx, [es:PSPDTA]
+	ret

kernel/syscall.asm

@@ -5,11 +5,7 @@
 ;  - exports a specified set of registers back to userspace
 ;
 ; The syscall table acts as a "export"-list for kernel near funcs.
-; Code invoked via it can reply on SS being zero.
+; Kernel code can expect CS = DS
-
-section .bss
-
-curpsp:	resw 1
 
 section .rodata
 
@@ -37,31 +33,6 @@ stab:	; syscall table
 
 section .text
 
-absolute 0
-
-	resb 2 ; ret 0 exit
-	resb 2 ; allocation length
-	resb 1
-	resb 5 ; CP/M entry point
-
-	; saved userdata
-PSPAX:	resw 1
-PSPCX:	resw 1
-	; SS:SP
-PSPSP:	resw 1
-PSPSS:	resw 1
-	; DS:DX
-PSPDX:  resw 1
-PSPDS:	resw 1
-	; ES:BX
-PSPBX:	resw 1
-PSPES:	resw 1
-
-	; default drive
-PSPDD:	resb 1
-
-section .text
-
 ; WARNING: BP, SI and DI are not saved
 ; If kernel code uses them, they need to be saved to the stack
 int21:	push ds
@@ -89,9 +60,12 @@ int21:	push ds
 	; load sysret and handler ptr
 	push word [cs:bx+2]
 	push word [cs:bx]
-	; restore user data and launch ret chain
+	; DS is always our segment
-	mov bx, [PSPBX]
+	push cs
-	mov ds, [PSPDS]
+	pop ds
+	; ES:BX is syscall argument
+	mov bx, [PSPDX]
+	mov es, [PSPDS]
 	ret
 
 err:	mov ah, 0xFF
@@ -107,6 +81,10 @@ sretw:	mov ds, [cs:curpsp]
 	mov es, [PSPES]
 	jmp sret.l02
 
+	; return carry flag in AL
+sretc:	mov ds, [cs:curpsp]
+	sbb al, al
+
 	; return AL to user
 sretb:	mov ds, [cs:curpsp]
 	mov ah, [PSPAX+1]