kernel.asm

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		mov	ss,word ptr DGROUP:clk_dos_seg
		pop	es
		pop	ds
		pop	di
		pop	si
		pop	bp
		pop	dx
		pop	cx
		pop	bx
		pop	ax
		popf
		ret	
clk_entry	endp


		page
;
; special interrupt routine for break key handling
;


;
; i_save
;	save machine context on stack after an interrupt
;	does not save ss and sp
;
;	assumes flags and cs:ip are on stack from interrupt
;
i_save		proc	near
		public	i_save
		push	bp		; start saving bp
		mov	bp,sp		; and mark frame for exit
		push	di		; save the rest of the registers
		push	si
		push	bx
		push	cx
		push	dx
		push	ds
		push	es
		xchg	ax,[bp+2]	; swap return address with ax
		push	ax		; put it back
		mov	ax,[bp+2]	; recover ax from entry
		mov	bp,[bp]		; and bp
		ret
i_save		endp


;
; i_exit
;	recovers context from i_save and does interrupt return
;	must be jumped to
;
;	warning - make sure you're using the right stack
;
i_exit		proc	near
		public	i_exit
		pop	es		; recover context
		pop	ds
		pop	dx
		pop	cx
		pop	bx
		pop	si
		pop	di
		pop	bp
		pop	ax
		iret			; and make like a tree (leave)
i_exit		endp


	extrn	_break_handler:near

_break_key	proc	near
		public	_break_key
		call	i_save			; save context
		mov	ax,cs			; correct for segments
		mov	ds,ax			; ax to carry segment
		mov	word ptr DGROUP:intr_dos_stk,sp	; use internal stack
		mov	word ptr DGROUP:intr_dos_seg,ss
		pushf				; put flags in bx
		pop	bx
		cli				; no interrupts
		mov	ss,ax
		mov	sp,offset DGROUP:intr_stk_top
		push	bx
		popf				; restore interrupt flag
		mov	bp,sp			; make a c frame
		call	_break_handler		; call handler
		les	bx,dword ptr con_rp	; now return completion code
		pushf
		pop	bx
		cli				; no interrupts
		mov	sp,word ptr DGROUP:intr_dos_stk	; use dos stack
		mov	ss,word ptr DGROUP:intr_dos_seg
		push	bx
		popf
		jmp	i_exit			; and restore & exit
_break_key	endp

_TEXT		ends


_FIXED_DATA	segment para public 'DATA'

; Because of the following bytes of data, THIS MODULE MUST BE THE FIRST
; IN THE LINK SEQUENCE.  THE BYTE AT DS:0004 determines the SDA format in 
; use.  A 0 indicates MS-DOS 3.X style, a 1 indicates MS-DOS 4.0-6.X style.
		public	DATASTART
DATASTART	label	byte
dos_data	db	0
		dw	start
		db	(?)		; padding
		dw	1		; Hardcoded MS-DOS 4.0+ style

; A reference seems to indicate that this should start at offset 26h.
		db	(26h - (offset $ - DATASTART)) dup (?)
		public	MARK0026H
MARK0026H	equ	$

; Globally referenced variables - WARNING: DO NOT CHANGE ORDER
; BECAUSE THEY ARE DOCUMENTED AS UNDOCUMENTED (?) AND HAVE
; MANY MULTIPLEX PROGRAMS AND TSR'S ACCESSING THEM
		public	_NetRetry
_NetRetry	dw	3		;-000c network retry count
		public	_NetDelay
_NetDelay	dw	1		;-000a network delay count
		public	_DskBuffer
_DskBuffer	dd	-1		;-0008 current dos disk buffer
		dw	(?)		;-0004 Unread con input
		public	_first_mcb
_first_mcb	dw	(?)		;-0002 Start of user memory
		public	_DPBp
_DPBp		dd	(?)		; 0000 First drive Parameter Block
		public	_sfthead
_sfthead	dd	(?)		; 0004 System File Table head
		public	_clock
_clock		dd	(?)		; 0008 CLOCK$ device
		public	_syscon
_syscon		dd	(?)		; 000c console device
		public	_maxbksize
_maxbksize	dw	(?)		; 0010 Number of Drives in system
		public	_firstbuf;
_firstbuf	dd	(?)	    	; 0012 head of buffers linked list
		public	_CDSp
_CDSp		dd	(?)		; 0016 Current Directory Structure
		public	_FCBp
_FCBp		dd	(?)		; 001a FCB table pointer
		public	_nprotfcb
_nprotfcb	dw	(?)		; 001e number of protected fcbs
		public	_nblkdev
_nblkdev	db	(?)		; 0020 number of block devices
		public	_lastdrive
_lastdrive	db	(?)		; 0021 value of last drive
		public	_nul_dev
_nul_dev	label	dword		; 0022 device chain root
		dd	-1
		dw	8004h		; attributes = char device, NUL bit set
		dw	offset _nul_strtgy
		dw	offset _nul_intr
		db	'NUL     '
		public	_njoined
_njoined	db	(?)		; 0034 number of joined devices
		dw	0		; 0035 DOS 4 pointer to special names (always zero in DOS 5)
setverPtr	dw	0,0		; 0037 setver list
		dw	0		; 003B cs offset for fix a20
		dw	0		; 003D psp of last umb exec
		dw	1		; 003F number of buffers
		dw	1		; 0041 size of pre-read buffer
		public	_BootDrive
_BootDrive	dw	(?)		; 0043 drive we booted from
		db	0		; 0044 cpu type (1 if >=386)
		dw	0		; 0045 Extended memory in KBytes
buf_info	dd	(?)		; 0047 disk buffer chain
		dw	0		; 004B 0 (DOS 4 = # hashing chains)
		dd	(?)		; 004D pre-read buffer
		dw	0		; 0051 # of sectors
		db	0		; 0053 00=conv 01=HMA
		dw	0		; 0054 deblock buf in conv
deblock_seg	dw	0		; 0056 (offset always zero)
		db	3 dup (?)	; 0058 unknown
		dw	0		; 005B unknown
		db	0, 0FFh, 0	; 005D unknown
		db	0		; 0060 unknown
		dw	0		; 0061 unknown
dmd_upper_link	db	0		; 0063 upper memory link flag
		dw	0		; 0064 unknown
dmd_upper_root	dw	0FFFFh		; 0066 dmd_upper_root
		dw	0		; 0068 para of last mem search
SysVarEnd	label	byte


; Some references seem to indicate that this data should start at 01fbh in
; order to maintain 100% MS-DOS compatibility.
		db	(01fbh - (SysVarEnd - DATASTART)) dup (?)

		public	MARK01FBH
MARK01FBH	equ	$
		db	128 dup (?)
		public	_kb_buf
_kb_buf	db	129,0			; initialise buffer to empty
		db	128+1 dup (?)	; room for 128 byte readline + LF
;
; Variables that follow are documented as part of the DOS 4.0-6.X swappable
; data area in Ralf Browns Interrupt List #56
;
; this byte is used for ^P support
		public	_PrinterEcho
_PrinterEcho	db	0		;-34 -  0 = no printer echo, ~0 echo
		public	_verify_ena
_verify_ena	db	0		; ~0, write with verify

; this byte is used for TAB's
		public _scr_pos
_scr_pos	db	0		; Current Cursor Column
		public	_switchar
_switchar	db	'/'		;-31 - switch char
		public	_mem_access_mode
_mem_access_mode db	0		;-30 -  memory allocation strategy
		public	sharing_flag
sharing_flag	db	0		; 00 = sharing module not loaded
					; 01 = sharing module loaded, but
					;      open/close for block devices
					;      disabled
					; FF = sharing module loaded,
					;      open/close for block devices
					;      enabled (not implemented)
		public	net_set_count
net_set_count	db	1		;-28 -  count the name below was set
		public	net_name
net_name	db	'               ' ;-27 - 15 Character Network Name
		db	00		  ; Terminating 0 byte


;
;	Variables contained the the "STATE_DATA" segment contain
;	information about the STATE of the current DOS Process. These
;	variables must be preserved regardless of the state of the INDOS
;	flag.
;
;	All variables that appear in "STATE_DATA" **MUST** be declared
;	in this file as the offsets from the INTERNAL_DATA variable are
;	critical to the DOS applications that modify this data area.
;
;
		public	_CritErrFlag, _InDOS
		public	_CritErrLocus, _CritErrCode
		public	_CritErrAction, _CritErrClass
		public	_CritErrDev, _CritErrDrive
		public  _dta
		public	_cu_psp, _default_drive
		public	_break_ena
		public  _return_code, _return_mode
		public	_internal_data

		public	_CritPatch
_CritPatch	dw	0d0ch		;-11 zero list of patched critical
		dw	0d0ch		;    section variables
		dw	0d0ch
		dw	0d0ch
		dw	0d0ch
		db	(?)		;-01 - unknown
_internal_data	label byte		; <-- Address returned by INT21/5D06
_CritErrFlag	db	0		; 00 - Critical Error Flag
_InDOS		db	0		; 01 - Indos Flag
_CritErrDrive	db	0		; 02 - Drive on write protect error
_CritErrLocus	db	0		; 03 - Error Locus
_CritErrCode	dw	0		; 04 - DOS format error Code
_CritErrAction	db	0		; 06 - Error Action Code
_CritErrClass	db	0		; 07 - Error Class
_CritErrDev	dd	(?)		; 08 - Failing Device Address
_dta		dd	(?)		; 0C - current DTA
_cu_psp		dw	(?)		; 10 - Current PSP
break_sp	dw	(?)		; 12 - used in int 23
_return_code	db	0		; 14 - return code from process
_return_mode	db	0		; 15 - reason for process terminate
_default_drive	db	0		; 16 - Current Drive
_break_ena	db	0		; 17 - Break Flag
		dw	0		; 18 - unknown

		public	_swap_always, _swap_indos
_swap_always	label	byte

		public	_Int21AX
_Int21AX	dw	0		; 1A - AX from last Int 21

		public	owning_psp, machine_id
owning_psp	dw	0		; 1C - owning psp
machine_id	dw	0		; 1E - remote machine ID
		dw	0		; 20 - First usable mcb
		dw	0		; 22 - Best usable mcb
		dw	0		; 24 - Last usable mcb
		dw	0		; 26 - memory size in paragraphs
		dw	0		; 28 - unknown
		db	0		; 2A - unknown
		db	0		; 2B - unknown
		db	0		; 2C - unknown
		public	_break_flg
_break_flg	db	0		; 2D - Program aborted by ^C
		db	0		; 2E - unknown
		db	0		; 2F - not referenced
		public	_DayOfMonth
_DayOfMonth	db	1		; 30 - day of month
		public	_Month
_Month		db	1		; 31 - month
		public	_YearsSince1980
_YearsSince1980	dw	0		; 32 - year since 1980
daysSince1980	dw	0FFFFh		; 34 - number of days since epoch
					; force rebuild on first clock read
		public	_DayOfWeek
_DayOfWeek	db	2		; 36 - day of week
		public	_Year
_Year		dw	1980		; 37 - year
		db	0		; 39 - unknown
		public	_CharReqHdr
_CharReqHdr	label	byte
		public	_ClkReqHdr
_ClkReqHdr	db	30 dup (?)	; 3A - Device driver request header
		dd	0		; 58 - pointer to driver entry
		public	_MediaReqHdr
_MediaReqHdr	db	22 dup (?)	; 5C - Device driver request header
		public	_IoReqHdr
_IoReqHdr	db	30 dup (?)	; 72 - Device driver request header
		db	6 dup (?)	; 90 - unknown
		public	_ClkRecord
_ClkRecord	db	6 dup (?)	; 96 - CLOCK$ transfer record
		dw	(?)		; 9C - unknown
		public	__PriPathBuffer
__PriPathBuffer	db	80h dup (?)	; 9E - buffer for file name
		public	__SecPathBuffer
__SecPathBuffer	db	80h dup (?)	;11E - buffer for file name
		public	_TempBuffer
_TempBuffer	db	21 dup (?)	;19E - 21 byte srch state
		public	_SearchDir
_SearchDir	db	32 dup (?)	;1B3 - 32 byte dir entry
		public	_TempCDS
_TempCDS	db	88 dup (?)	;1D3 - TemporaryCDS buffer
		public	_DirEntBuffer
_DirEntBuffer	db	32 dup (?)	;22B - space enough for 1 dir entry
		public	_wAttr
_wAttr		dw	0		;24B - extended FCB file attribute


		; Pad to 057Ch
		db	(25ch - (offset $ - _internal_data)) dup (?)

		public	_tsr		; used by break and critical error
_tsr		db	0		;25C -  handlers during termination
		db	(?)		;25D - padding
		public	term_psp
term_psp    	dw  0       		;25E - ???
		public	int24_esbp
int24_esbp	dw	2 dup (?)	;260 - pointer to criticalerr DPB
		public	_user_r, int21regs_off, int21regs_seg
_user_r		label	dword
int21regs_off	dw	0		;264 - pointer to int21h stack frame
int21regs_seg	dw	0
		public	critical_sp
critical_sp	dw	0		;268 - critical error internal stack
		public	current_ddsc
current_ddsc	dw	2 dup (?)

		; Pad to 059ah 
		db	(27ah - (offset $ - _internal_data)) dup (?)
		public	current_device
current_device	dw	2 dup (?)	;27A - ???
		public	_lpCurSft
_lpCurSft	dw	2 dup (?)	;27e - Current SFT
		public	current_ldt
current_ldt	dw	2 dup (?)	;282 - Current CDS
		public	_lpFcb
_lpFcb		dw	2 dup (?)	;286 - pointer to callers FCB
		public	current_ifn
current_ifn	dw	0		;28A - SFT index for next open

		; Pad to 05ceh 
		db	(2aeh - (offset $ - _internal_data)) dup (?)
		public	current_filepos
current_filepos	dw	2 dup (?)	;2AE - current offset in file

		; Pad to 05f0h 
		db	(2d0h - (offset $ - _internal_data)) dup (?)
		public	_prev_user_r
		public	prev_int21regs_off
		public	prev_int21regs_seg
_prev_user_r	label	dword
prev_int21regs_off	dw	0	;2D0 - pointer to prev int 21 frame
prev_int21regs_seg	dw	0

		; Pad to 0620h 
		db	(300h - (offset $ - _internal_data)) dup (?)

		public	_FcbSearchBuffer	; during FCB search 1st/next use bottom
_FcbSearchBuffer	label byte		;  of error stack as scratch buffer
;		db	43 dup (?)		;  - only used during int 21 call
		public	_LocalPath
_LocalPath	label	byte			
;		db	67 dup (?)		
		; stacks are made to initialize to no-ops so that high-water
		; tesing can be performed
apistk_bottom	label	word
		dw	STACK_SIZE dup (?)	;300 - Error Processing Stack
		public	_error_tos
_error_tos	label	word
		dw	STACK_SIZE dup (?)	;480 - Disk Function Stack
		public	_disk_api_tos
_disk_api_tos	label	word
		dw	STACK_SIZE dup (?)	;600 - Char Function Stack
		public	_char_api_tos
_char_api_tos	label	word
apistk_top	label	word

_VolChange	db	0		;781 - volume change
_VirtOpen	db	0		;782 - virtual open flag

		; controlled variables end at offset 78Ch so pad to end
		db	(78ch - (offset $ - _internal_data)) dup (?)
_swap_indos	label	byte
;
; end of controlled variables
;
_FIXED_DATA	ends

_BSS		segment word public 'BSS'
		public	_NumFloppies
_NumFloppies	dw	(?)
rqhdr		dd	(?)
con_rp		dd	(?)
blk_rp		dd	(?)
clk_rp		dd	(?)
con_dos_stk	dw	(?)
con_dos_seg	dw	(?)
blk_dos_stk	dw	(?)
blk_dos_seg	dw	(?)
clk_dos_stk	dw	(?)
clk_dos_seg	dw	(?)
intr_dos_stk	dw	(?)
intr_dos_seg	dw	(?)


		public	_api_sp
_api_sp		dw	(?)		; api stacks - for context
		public	_api_ss
_api_ss		dw	(?)		; switching
		public	_usr_sp
_usr_sp		dw	(?)		; user stacks
		public	_usr_ss
_usr_ss		dw	(?)
		public	_ram_top
_ram_top	dw	(?)

_BSS		ends



_BSSEND		segment byte public 'STACK'
; condev private stack
		dw	256 dup (?)
con_stk_top	label	byte

; blockdev private stack
		dw	256 dup (?)
blk_stk_top	label	byte

; clockdev private stack
		dw	256 dup (?)
clk_stk_top	label	byte

; interrupt stack
		dw	256 dup (?)
intr_stk_top	label	byte

; int 21 api stack area
		public	stack_bottom
stack_bottom	label	word
;		dw	1024 dup (?)
;		public	_error_tos
;_error_tos	label	word
;		dw	4096 dup (?)
;		public	_char_api_tos
;_char_api_tos	label	word
;		dw	4096 dup (?)
;		public	_disk_api_tos
;_disk_api_tos	label	word
		public	last
		dw	512
tos		label	byte
last		label	word			; must always be end of stack area
		public	_last
_last		label	byte			; and c version

_BSSEND		ends


		end	entry