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;
; File:
; kernel.asm
; Description:
; kernel start-up code
;
; Copyright (c) 1995, 1996
; Pasquale J. Villani
; All Rights Reserved
;
; This file is part of DOS-C.
;
; DOS-C is free software; you can redistribute it and/or
; modify it under the terms of the GNU General Public License
; as published by the Free Software Foundation; either version
; 2, or (at your option) any later version.
;
; DOS-C is distributed in the hope that it will be useful, but
; WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
; the GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public
; License along with DOS-C; see the file COPYING. If not,
; write to the Free Software Foundation, 675 Mass Ave,
; Cambridge, MA 02139, USA.
;
; $Id: kernel.asm 1705 2012-02-07 08:10:33Z perditionc $
;
%include
"segs.inc"
%include
"stacks.inc"
%include
"ludivmul.inc"
segment PSP
extern
_ReqPktPtr
STACK_SIZE equ
384
/
2
; stack allocated in words
;************************************************************
; KERNEL BEGINS HERE, i.e. this is byte 0 of KERNEL.SYS
;************************************************************
%ifidn
__OUTPUT_FORMAT__
,
obj
..start:
%endif
bootloadunit:
; (byte of short jump re-used)
entry:
jmp
short realentry
;************************************************************
; KERNEL CONFIGURATION AREA
; this is copied up on the very beginning
; it's a good idea to keep this in sync with KConfig.h
;************************************************************
global
_LowKernelConfig
_LowKernelConfig:
config_signature:
db
'CONFIG'
; constant
dw
configend
-
configstart
; size of config area
; to be checked !!!
configstart:
DLASortByDriveNo db
0
; sort disks by drive order
InitDiskShowDriveAssignment db
1
;
SkipConfigSeconds db
2
;
ForceLBA db
0
;
GlobalEnableLBAsupport db
1
;
BootHarddiskSeconds db
0
;
; The following VERSION resource must be keep in sync with VERSION.H
Version_OemID db
0xFD
; OEM_ID
Version_Major db
2
Version_Revision dw
43
; REVISION_SEQ
Version_Release dw
1
; 0=release build, >0=svn#
CheckDebugger: db
0
; 0 = no check, 1 = check, 2 = assume present
Verbose db
0
; -1 = quiet, 0 = normal, 1 = verbose
PartitionMode db
0x1f
; bits 0-1: 01=GPT if found, 00=MBR if found, 11=Hybrid, GPT first then MBR, 10=Hybrid, MBR first then GPT
; in hybrid mode, EE partitions ignored, drives assigned by GPT or MBR first based on hybrid type
; bits 2-4: 001=mount ESP (usually FAT32) partition, 010=mount MS Basic partitions, 100=mount unknown partitions
; 111=attempt to mount all paritions, 110=attempt to mount all but ESP partitions
; bits 5-7: reserved, 0 else undefined behavior
configend:
kernel_config_size: equ configend
-
config_signature
; must be below-or-equal the size of struct _KernelConfig
; in the file kconfig.h !
times
(
32
-
4
)
-
($
-
$$) db
0
bootloadstack: dd
0
;************************************************************
; KERNEL CONFIGURATION AREA END
;************************************************************
;************************************************************
; KERNEL real entry (at ~60:20)
;
; moves the INIT part of kernel.sys to high memory (~9000:0)
; then jumps there
; to aid debugging, some '123' messages are output
; this area is discardable and used as temporary PSP for the
; init sequence
;************************************************************
cpu
8086
; (keep initial entry compatible)
global
realentry
realentry:
; execution continues here
push
cs
pop
ds
xor
di
,
di
mov
byte
[
di
+
bootloadunit
-
$$
],
bl
push
bp
mov
word
[
di
+
bootloadstack
-
$$
],
sp
mov
word
[
di
+
bootloadstack
+
2
-
$$
],
ss
jmp
entry_
common
times
0C0h
-
($
-
$$)
nop
; magic offset (used by exeflat)
entry_
common
:
%ifndef
QUIET
push
ax
push
bx
pushf
mov
ax
,
0e31h
; '1' Tracecode - kernel entered
mov
bx
,
00f0h
int
010h
popf
pop
bx
pop
ax
%endif
push
cs
pop
ds
jmp
IGROUP:kernel_start
beyond_entry: times
256
-
(beyond_entry
-
entry) db
0
; scratch area for data (DOS_PSP)
_master_env equ $
-
128
global
_master_env
segment INIT_TEXT
%ifdef
TEST_FILL_INIT_TEXT
%macro step
0
%if
_LFSR &
1
%assign
_LFSR (_LFSR >>
1
) ^
0x80200003
%else
%assign
_LFSR (_LFSR >>
1
)
%endif
%endmacro
align
16
%assign
_LFSR
1
%rep
1024
*
8
dd
_LFSR
step
%endrep
%endif
extern
_FreeDOSmain
extern
_query_
cpu
;
; kernel start-up
;
kernel_start:
cld
%ifndef
QUIET
push
bx
pushf
mov
ax
,
0e32h
; '2' Tracecode - kernel entered
mov
bx
,
00f0h
int
010h
popf
pop
bx
%endif
extern
_kernel_command_line
; INP: ds => entry section, with CONFIG block
; and compressed entry help data
; (actually always used now)
initialise_command_line_buffer:
mov
dx
,
I_GROUP
mov
es
,
dx
mov
bl
,
[
bootloadunit
]
lds
si
,
[
bootloadstack
]
; -> original ss:sp - 2
lea
ax
,
[
si
+
2
]
; ax = original sp
mov
si
,
word
[
si
]
; si = original bp
; Note that the kernel command line buffer in
; the init data segment is pre-initialised to
; hold 0x00 0xFF in the first two bytes. This
; is used to indicate no command line present,
; as opposed to an empty command line which
; will hold 0x00 0x00.
; If any of the branches to .none are taken then
; the buffer is not modified so it retains the
; 0x00 0xFF contents.
cmp
si
,
114h
; buffer fits below ss:bp ?
jb
.none
; no -->
cmp
word
[
si
-
14h
],
"CL"
; signature passed to us ?
jne
.none
; no -->
lea
si
,
[
si
-
114h
]
; -> command line buffer
cmp
ax
,
si
; stack top starts below-or-equal buffer ?
ja
.none
; no -->
mov
di
,
_kernel_command_line
; our buffer
mov
cx
,
255
xor
ax
,
ax
push
di
rep
movsb
; copy up to 255 bytes
stosb
; truncate
pop
di
mov
ch
,
1
; cx = 256
repne
scasb
; scan for terminator
rep
stosb
; clear remainder of buffer
; (make sure we do not have 0x00 0xFF
; even if the command line given is
; actually the empty string)
.none:
cli
mov
ss
,
dx
mov
sp
,
init_tos
int
12h
; move init text+data to higher memory
mov
cl
,
6
shl
ax
,
cl
; convert kb to para
mov
dx
,
15
+
INITSIZE
mov
cl
,
4
shr
dx
,
cl
sub
ax
,
dx
mov
es
,
ax
mov
dx
,
INITTEXTSIZE
; para aligned
shr
dx
,
cl
add
ax
,
dx
mov
ss
,
ax
; set SS to init data segment
sti
; now enable them
mov
ax
,
cs
mov
dx
,
__HMATextEnd
; para aligned
shr
dx
,
cl
%ifdef
WATCOM
add
ax
,
dx
%endif
mov
ds
,
ax
mov
si
,-
2
+
INITSIZE
; word aligned
lea
cx
,[
si
+
2
]
mov
di
,
si
shr
cx
,
1
std
; if there's overlap only std is safe
rep
movsw
; move HMA_TEXT to higher memory
sub
ax
,
dx
mov
ds
,
ax
; ds = HMA_TEXT
mov
ax
,
es
sub
ax
,
dx
mov
es
,
ax
; es = new HMA_TEXT
mov
si
,-
2
+
__HMATextEnd
lea
cx
,[
si
+
2
]
mov
di
,
si
shr
cx
,
1
rep
movsw
cld
%ifndef
WATCOM
; for WATCOM: CS equal for HMA and INIT
add
ax
,
dx
mov
es
,
ax
; otherwise CS -> init_text
%endif
push
es
mov
ax
,
cont
push
ax
retf
cont:
; Now set up call frame
mov
ds
,[
cs
:_INIT_DGROUP
]
mov
bp
,
sp
; and set up stack frame for c
%ifndef
QUIET
push
bx
pushf
mov
ax
,
0e33h
; '3' Tracecode - kernel entered
mov
bx
,
00f0h
int
010h
popf
pop
bx
%endif
mov
byte
[
_BootDrive
],
bl
; tell where we came from
;!! int 11h
;!! mov cl,6
;!! shr al,cl
;!! inc al
;!! mov byte [_NumFloppies],al ; and how many
call
_query_
cpu
%if
XCPU !=
86
%if
XCPU <
186
|| (X
CPU
%
100
) !=
86
|| (X
CPU
/
100
) >
9
%fatal
Unknown
CPU
level defined
%endif
cmp
al
,
(X
CPU
/
100
)
jb
cpu_abort
; if CPU not supported -->
cpu
XCPU
%endif
mov
[
_CPULevel
],
al
initialise_kernel_config:
extern
_InitKernelConfig
mov
ax
,
ss
; => init data segment
mov
si
,
60h
mov
ds
,
si
; => entry section
mov
si
,
_LowKernelConfig
; -> our CONFIG block
mov
es
,
ax
; => init data segment
mov
di
,
_InitKernelConfig
; -> init's CONFIG block buffer
mov
cx
,
kernel_config_size /
2
; size that we support
rep
movsw
; copy it over
%if
kernel_config_size &
1
movsb
; allow odd size
%endif
mov
ds
,
ax
; => init data segment
check_debugger_present:
extern
_debugger_present
mov
al
,
1
; assume debugger present
cmp
byte
[
di
-
kernel_config_size
+
(CheckDebugger
-
config_signature)
],
1
ja
.skip_ints_00_06
; 2 means assume present
jb
.absent
; 0 means assume absent
clc
; 1 means check
int3
; break to debugger
jc
.skip_ints_00_06
; The debugger should set CY here to indicate its
; presence. The flag set is checked later to skip
; overwriting the interrupt vectors 00h, 01h, 03h,
; and 06h. This logic is taken from lDOS init.
.absent:
xor
ax
,
ax
; no debugger present
.skip_ints_00_06:
mov
byte
[
_debugger_present
],
al
jmp
_FreeDOSmain
%if
XCPU !=
86
cpu
8086
cpu_abort:
mov
ah
,
0Fh
int
10h
; get video mode, bh = active page
call
.first
; print string that follows (address pushed by call)
%define
LOADNAME
"FreeDOS"
db
13
,
10
; (to emit a blank line after the tracecodes)
db
13
,
10
db
LOADNAME
,
" load error: An 80"
,
'0'
+
(X
CPU
/
100
)
db
"86 processor or higher is required by this build."
,
13
,
10
db
"To use "
,
LOADNAME
,
" on this processor please"
db
" obtain a compatible build."
,
13
,
10
db
13
,
10
db
"Press any key to reboot."
,
13
,
10
db
0
.display:
mov
ah
,
0Eh
mov
bl
,
07h
; page in bh, bl = colour for some modes
int
10h
; write character (may change bp!)
db
0A8h
; [test al,imm8] skip "pop si" [=imm8] after the first iteration
.first:
pop
si
; (first iteration only) get message address from stack
cs
lodsb
; get character
test
al
,
al
; zero ?
jnz
.display
; no, display and get next character -->
xor
ax
,
ax
xor
dx
,
dx
int
13h
; reset floppy disks
xor
ax
,
ax
mov
dl
,
80h
int
13h
; reset hard disks
; this "test ax, imm16" opcode is used to
db
0A9h
; skip "sti" \ "hlt" [=imm16] during first iteration
.
wait
:
sti
hlt
; idle while waiting for keystroke
mov
ah
,
01h
int
16h
; get keystroke
jz
.
wait
; none available, loop -->
mov
ah
,
00h
int
16h
; remove keystroke from buffer
int
19h
; reboot
jmp
short $
; (in case it returns, which it shouldn't)
cpu
XCPU
%endif
; XCPU != 86
segment INIT_TEXT_END
;************************************************************
; KERNEL CODE AREA END
; the NUL device
;************************************************************
segment CONST
;
; NUL device strategy
;
global
_nul_strtgy
extern
GenStrategy
_nul_strtgy:
jmp
LGROUP:GenStrategy
;
; NUL device interrupt
;
global
_nul_intr
_nul_intr:
push
es
push
bx
mov
bx
,
LGROUP
mov
es
,
bx
les
bx
,[
es
:_ReqPktPtr
]
;es:bx--> rqheadr
cmp
byte
[
es
:
bx
+
2
],
4
;if read, set 0 read
jne
no_nul_read
mov
word
[
es
:
bx
+
12h
],
0
no_nul_read:
or
word
[
es
:
bx
+
3
],
100h
;set "done" flag
pop
bx
pop
es
retf
segment _LOWTEXT
; low interrupt vectors 10h,13h,15h,19h,1Bh
; these need to be at 0070:0100 (see RBIL memory.lst)
global
_intvec_table
_intvec_table: db
10h
dd
0
; used by int13 handler and get/set via int 2f/13h
global
_BIOSInt13
; BIOS provided disk handler
global
_UserInt13
; actual disk handler used by kernel
db
13h
_BIOSInt13: dd
0
db
15h
dd
0
; used for cleanup on reboot
global
_BIOSInt19
db
19h
_BIOSInt19: dd
0
db
1Bh
dd
0
; default to using BIOS provided disk handler
db
13h
_UserInt13: dd
0
; floppy parameter table
global
_int1e_table
_int1e_table: times
0eh
db
0
;************************************************************
; KERNEL FIXED DATA AREA
;************************************************************
segment _FIXED_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.
global
DATASTART
DATASTART:
global
_DATASTART
_DATASTART:
dos_data db
0
dw
kernel_start
db
0
; padding
dw
1
; Hardcoded MS-DOS 4.0+ style
times
(
0eh
-
($
-
DATASTART)) db
0
global
_NetBios
_NetBios dw
0
; NetBios Number
times
(
26h
-
0ch
-
($
-
DATASTART)) db
0
; Globally referenced variables - WARNING: DO NOT CHANGE ORDER
; BECAUSE THEY ARE DOCUMENTED AS UNDOCUMENTED (?) AND HAVE
; MANY MULTIPLEX PROGRAMS AND TSRs ACCESSING THEM
global
_NetRetry
_NetRetry dw
3
;-000c network retry count
global
_NetDelay
_NetDelay dw
1
;-000a network delay count
global
_DskBuffer
_DskBuffer dd
-
1
;-0008 current dos disk buffer
global
_inputptr
_inputptr dw
0
;-0004 Unread con input
global
_first_mcb
_first_mcb dw
0
;-0002 Start of user memory
global
_DPBp
global
MARK0026H
; A reference seems to indicate that this should start at offset 26h.
MARK0026H equ $
_DPBp dd
-
1
; 0000 First drive Parameter Block
global
_sfthead
_sfthead dd
0
; 0004 System File Table head
global
_clock
_clock dd
0
; 0008 CLOCK$ device
global
_syscon
_syscon dw _con_dev
,
LGROUP
; 000c console device
global
_maxsecsize
_maxsecsize dw
512
; 0010 maximum bytes/sector of any block device
dd
0
; 0012 pointer to buffers info structure
global
_CDSp
_CDSp dd
0
; 0016 Current Directory Structure
global
_FCBp
_FCBp dd
0
; 001a FCB table pointer
global
_nprotfcb
_nprotfcb dw
0
; 001e number of protected fcbs
global
_nblkdev
_nblkdev db
0
; 0020 number of block devices
global
_lastdrive
_lastdrive db
0
; 0021 value of last drive
global
_nul_dev
_nul_dev:
; 0022 device chain root
extern
_con_dev
dw
_con_dev
,
LGROUP
; next is con_dev at init time.
dw
8004h
; attributes = char device, NUL bit set
dw
_nul_strtgy
dw
_nul_intr
db
'NUL '
global
_njoined
_njoined db
0
; 0034 number of joined devices
dw
0
; 0035 DOS 4 near pointer to special names (always zero in DOS 5) [setver precursor]
global
_setverPtr
_setverPtr dw
0
,
0
; 0037 setver list (far pointer, set by setver driver)
dw
0
; 003B cs offset for fix a20
dw
0
; 003D psp of last umb exec
global
_LoL_nbuffers
_LoL_nbuffers dw
1
; 003F number of buffers
dw
1
; 0041 size of pre-read buffer
global
_BootDrive
_BootDrive db
1
; 0043 drive we booted from
global
_CPULevel
_CPULevel db
0
; 0044 cpu type (MSDOS >0 indicates dword moves ok, ie 386+)
; unless compatibility issues arise FD uses
; 0=808x, 1=18x, 2=286, 3=386+
; see cpu.asm, use >= as may add checks for 486 ...
dw
0
; 0045 Extended memory in KBytes
buf_info:
global
_firstbuf
_firstbuf dd
0
; 0047 disk buffer chain
dw
0
; 004B Number of dirty buffers
dd
0
; 004D pre-read buffer
dw
0
; 0051 number of look-ahead buffers
global
_bufloc
_bufloc db
0
; 0053 00=conv 01=HMA
global
_deblock_buf
_deblock_buf dd
0
; 0054 deblock buffer
times
3
db
0
; 0058 unknown
dw
0
; 005B unknown
db
0
,
0FFh
,
0
; 005D unknown
global
_VgaSet
_VgaSet db
0
; 0060 unknown
dw
0
; 0061 unknown
global
_uppermem_link
_uppermem_link db
0
; 0063 upper memory link flag
_min_pars dw
0
; 0064 minimum paragraphs of memory
; required by program being EXECed
global
_uppermem_root
_uppermem_root dw
0ffffh
; 0066 dmd_upper_root (usually 9fff)
_last_para dw
0
; 0068 para of last mem search
SysVarEnd:
;; FreeDOS specific entries
;; all variables below this point are subject to relocation.
;; programs should not rely on any values below this point!!!
global
_os_setver_minor
_os_setver_minor db
0
global
_os_setver_major
_os_setver_major db
5
global
_os_minor
_os_minor db
0
global
_os_major
_os_major db
5
_rev_number db
0
global
_version_flags
_version_flags db
0
global
os_release
extern
_os_release
os_release dw _os_release
%IFDEF
WIN31SUPPORT
global
_winStartupInfo
,
_winInstanced
_winInstanced dw
0
; set to 1 on WinInit broadcast, 0 on WinExit broadcast
_winStartupInfo:
dw
0
; structure version (same as windows version)
dd
0
; next startup info structure, 0:0h marks end
dd
0
; far pointer to name virtual device file or 0:0h
dd
0
; far pointer, reference data for virtual device driver
%ifnidni
__OUTPUT_FORMAT__
,
elf
dw
instance_table
,
seg instance_table
; array of instance data
%else
dw
instance_table
; array of instance data
global
_winseg1
_winseg1: dw
0
%endif
instance_table:
; should include stacks, Win may auto determine SDA region
; we simply include whole DOS data segment
%ifnidni
__OUTPUT_FORMAT__
,
elf
dw
seg _DATASTART
,
0
; [SEG:OFF] address of region's base
dw
_markEndInstanceData wrt seg _DATASTART
; size in bytes
%else
global
_winseg2
_winseg2: dw
0
dw
0
; [SEG:OFF] address of region's base
global
_winseg3
_winseg3: dw
0
; size in bytes
%endif
dd
0
; 0 marks end of table
dw
0
; and 0 length for end of instance_table entry
global
_winPatchTable
_winPatchTable:
; returns offsets to various internal variables
dw
0x0006
; DOS version, major# in low byte, eg. 6.00
dw
save_DS
; where DS stored during int21h dispatch
dw
save_BX
; where BX stored during int21h dispatch
dw
_InDOS
; offset of InDOS flag
dw
_MachineId
; offset to variable containing MachineID
dw
_CritPatch
; offset of to array of offsets to patch
; NOTE: this points to a null terminated
; array of offsets of critical section bytes
; to patch, for now we can just point this
; to an empty table
; ie we just point to a 0 word to mark end
dw
_uppermem_root
; seg of last arena header in conv memory
; this matches MS DOS's location, but
; do we have the same meaning?
%ENDIF
; WIN31SUPPORT
;; The first 5 sft entries appear to have to be at DS:00cc
times
(
0cch
-
($
-
DATASTART)) db
0
global
_firstsftt
_firstsftt:
dd
-
1
; link to next
dw
5
; count
times
5
*
59
db
0
; reserve space for the 5 sft entries
db
0
; pad byte so next value on even boundary
; Some references seem to indicate that this data should start at 01fbh in
; order to maintain 100% MS-DOS compatibility.
times
(
01fbh
-
($
-
DATASTART)) db
0
global
MARK01FBH
MARK01FBH equ $
global
_local_buffer
; local_buffer is 256 bytes long
; so it overflows into kb_buf!!
; only when kb_buf is used, local_buffer is limited to 128 bytes.
_local_buffer: times
128
db
0
global
_kb_buf
_kb_buf db
128
,
0
; initialise buffer to empty
times
128
+
1
db
0
; 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
global
_PrinterEcho
_PrinterEcho db
0
;-34 - 0 = no printer echo, ~0 echo
global
_verify_ena
_verify_ena db
0
; ~0, write with verify
; this byte is used for TABs (shared by all char device writes??)
global
_scr_pos
_scr_pos db
0
; Current Cursor Column
global
_switchar
_switchar db
'/'
;-31 - switch char
global
_mem_access_mode
_mem_access_mode db
0
;-30 - memory allocation strategy
global
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)
global
_net_set_count
_net_set_count db
1
;-28 - count the name below was set
global
_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.
;
;
global
_ErrorMode
,
_InDOS
global
_CritErrLocus
,
_CritErrCode
global
_CritErrAction
,
_CritErrClass
global
_CritErrDev
,
_CritErrDrive
global
_dta
global
_cu_psp
,
_default_drive
global
_break_ena
global
_return_code
global
_internal_data
; ensure offset of critical patch table remains fixed, some programs hard code offset
times
(
0315h
-
($
-
DATASTART)) db
0
global
_CritPatch
_CritPatch dw
0
;-11 zero list of patched critical
dw
0
; section variables
dw
0
; DOS puts 0d0ch here but some
dw
0
; progs really write to that addr.
dw
0
;-03 - critical patch list terminator
db
90h
;-01 - unused, NOP pad byte
_internal_data:
; <-- Address returned by INT21/5D06
_ErrorMode 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
0
; 08 - Failing Device Address
_dta dd
0
; 0C - current DTA
_cu_psp dw
0
; 10 - Current PSP
break_sp dw
0
; 12 - used in int 23
_return_code dw
0
; 14 - return code from process
_default_drive db
0
; 16 - Current Drive
_break_ena db
1
; 17 - Break Flag (default TRUE)
db
0
; 18 - flag, code page switching
db
0
; 19 - flag, copy of 18 on int 24h abort
global
_swap_always
,
_swap_indos
_swap_always:
global
_Int21AX
_Int21AX dw
0
; 1A - AX from last Int 21
global
owning_psp
,
_MachineId
owning_psp dw
0
; 1C - owning psp
_MachineId 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
global
_break_flg
_break_flg db
0
; 2D - Program aborted by ^C
db
0
; 2E - unknown
db
0
; 2F - not referenced
global
_DayOfMonth
_DayOfMonth db
1
; 30 - day of month
global
_Month
_Month db
1
; 31 - month
global
_YearsSince1980
_YearsSince1980 dw
0
; 32 - year since 1980
daysSince1980 dw
0FFFFh
; 34 - number of days since epoch
; force rebuild on first clock read
global
_DayOfWeek
_DayOfWeek db
2
; 36 - day of week
_console_swap db
0
; 37 console swapped during read from dev
global
_dosidle_flag
_dosidle_flag db
1
; 38 - safe to call int28 if nonzero
global
_abort_progress
_abort_progress db
0
; 39 - abort in progress
global
_CharReqHdr
_CharReqHdr:
global
_ClkReqHdr
_ClkReqHdr times
30
db
0
; 3A - Device driver request header
dd
0
; 58 - pointer to driver entry
global
_MediaReqHdr
_MediaReqHdr times
22
db
0
; 5C - Device driver request header
global
_IoReqHdr
_IoReqHdr times
30
db
0
; 72 - Device driver request header
times
6
db
0
; 90 - unknown
global
_ClkRecord
_ClkRecord times
6
db
0
; 96 - CLOCK$ transfer record
dw
0
; 9C - unknown
global
__PriPathBuffer
__PriPathBuffer times
80h
db
0
; 9E - buffer for file name
global
__SecPathBuffer
__SecPathBuffer times
80h
db
0
;11E - buffer for file name
global
_sda_tmp_dm
_sda_tmp_dm times
21
db
0
;19E - 21 byte srch state
global
_SearchDir
_SearchDir times
32
db
0
;1B3 - 32 byte dir entry
global
_TempCDS
_TempCDS times
88
db
0
;1D3 - TemporaryCDS buffer
global
_DirEntBuffer
_DirEntBuffer times
32
db
0
;22B - space enough for 1 dir entry
global
_wAttr
_wAttr dw
0
;24B - extended FCB file attribute
global
_SAttr
_SAttr db
0
;24D - Attribute Mask for Dir Search
global
_OpenMode
_OpenMode db
0
;24E - File Open Attribute
times
3
db
0
global
_Server_Call
_Server_Call db
0
;252 - Server call Func 5D sub 0
db
0
; Pad to 05CCh
times
(
25ch
-
($
-
_internal_data)) db
0
global
_term_type
; used by break and critical error
_term_type db
0
;25C - handlers during termination
; ecm: 00h = normal terminate,
; 01h = control-c terminate,
; 02h = critical error abort,
; 03h = TSR terminate
db
0
;25D - padding
global
term_psp
term_psp dw
0
;25E - 0??
global
int24_esbp
int24_esbp times
2
dw
0
;260 - pointer to criticalerr DPB
global
_user_r
,
int21regs_off
,
int21regs_seg
_user_r:
int21regs_off dw
0
;264 - pointer to int21h stack frame
int21regs_seg dw
0
; i.e. points stack frame (SS:SP) with user registers when int21h called
global
critical_sp
critical_sp dw
0
;268 - critical error internal stack, store SP during int24h
global
current_ddsc
current_ddsc times
2
dw
0
;26A - pointer to DPB for ???
diskbuf_seg dw
0
;26E - segment of disk buffer
dd
0
;270 - saving partial cluster number??? - see https://faydoc.tripod.com/structures/16/1690.htm
dw
0
dw
0
;276 - temp word
db
0
;278 - media id returned by AH=1Bh,1Ch
db
0
;279 - unused
; Pad to 059ah
times
(
27ah
-
($
-
_internal_data)) db
0
global
current_device
current_device times
2
dw
0
;27A - point to device header if filename is character device
global
_lpCurSft
_lpCurSft times
2
dw
0
;27e - Current SFT
global
_current_ldt
_current_ldt times
2
dw
0
;282 - Current CDS (ThisCDS in published MSDOS sources)
global
_sda_lpFcb
_sda_lpFcb times
2
dw
0
;286 - pointer to callers FCB
global
_current_sft_idx
_current_sft_idx dw
0
;28A - SFT index for next open
; used by MS NET
dw
0
;28C - temp file handler
dd
0
;28E - pointer to JFT entry (for file being opened) in process handle table
; Pad to 05b2h
times
(
292h
-
($
-
_internal_data)) db
0
dw
__PriPathBuffer
; 292 - "sda_WFP_START" offset in DOS DS of first filename argument
dw
__SecPathBuffer
; 294 - "sda_REN_WFP" offset in DOS DS of second filename argument
dw
0ffffh
; 296 - 0xffff or offset of last component in filename
; Pad to 05ceh
times
(
2aeh
-
($
-
_internal_data)) db
0
global
_current_filepos
_current_filepos times
2
dw
0
;2AE - current offset in file
; Pad to 05eah
times
(
2cah
-
($
-
_internal_data)) db
0
;global _save_BX
;global _save_DS
save_BX dw
0
;2CA - unused by FreeDOS, for Win3.x
save_DS dw
0
; compatibility, match MS's positions
dw
0
; store DS,BX on entry to int21h (ie caller's values)
global
_prev_user_r
global
prev_int21regs_off
global
prev_int21regs_seg
_prev_user_r:
prev_int21regs_off dw
0
;2D0 - pointer to prev int 21 frame (see offset 264h)
prev_int21regs_seg dw
0
; Pad to 05fdh, 2D4 through 2E4 used for int21h/ax=6C00h
times
(
2ddh
-
($
-
_internal_data)) db
0
global
_ext_open_action
global
_ext_open_attrib
global
_ext_open_mode
_ext_open_action dw
0
;2DD - extended open action
_ext_open_attrib dw
0
;2DF - extended open attrib
_ext_open_mode dw
0
;2E1 - extended open mode
open_filename dd
0
;2E3 pointer to filename to open (see ax=6C00h)
; Pad to 0620h
times
(
300h
-
($
-
_internal_data)) db
0
global
apistk_bottom
apistk_bottom:
; use bottom of error stack as scratch buffer
; - only used during int 21 call
global
_sda_tmp_dm_ren
_sda_tmp_dm_ren:times
21
db
0x90
;300 - 21 byte srch state for rename
global
_SearchDir_ren
_SearchDir_ren: times
32
db
0x90
;315 - 32 byte dir entry for rename
; stacks are made to initialize to no-ops so that high-water
; testing can be performed
times
STACK_SIZE
*
2
-
($
-
apistk_bottom) db
0x90
; critical error stack 331 bytes?, disk stack 384 bytes, character i/o 384 bytes
;300 - Error Processing Stack
global
_error_tos
_error_tos:
times
STACK_SIZE dw
0x9090
;480 - Disk Function Stack
global
_disk_api_tos
_disk_api_tos:
times
STACK_SIZE dw
0x9090
;600 - Char Function Stack
global
_char_api_tos
_char_api_tos:
apistk_top:
db
0
;780 device driver look-ahead (printer), see ah=64h
_VolChange db
0
;781 - volume change
_VirtOpen db
0
;782 - virtual open flag
; 783h to 788h are fastseek drive, 1st cluster, logical cluster, returned logical cluster
; 78Ah dw ? temp location of SYSINIT
; controlled variables end at offset 78Ch so pad to end
times
(
78ch
-
($
-
_internal_data)) db
0
; MSDOS 7.1+ with FAT32 SDA extended
;78Ch - 47 bytes of ???
times
(
7bbh
-
($
-
_internal_data)) db
0
absrdwrflg db
0
;7bbh - 0=int 25h/26h absolute read/write, 1=int 21h/ax=7305h
times
12
dw
0
;7bch to 7d2h, high word of 32bit values, see offsets 0x 2a2, 29c, 2bc, 29a, 276, 244, & registers ebx,edx,edi,ecx
times
3
dw
0
; ???
;
; end of controlled variables
;
segment _BSS
;!! global _NumFloppies
;!!_NumFloppies resw 1
;!!intr_dos_stk resw 1
;!!intr_dos_seg resw 1
; mark front and end of bss area to clear
segment IB_B
global
__ib_start
__ib_start:
segment IB_E
global
__ib_end
__ib_end:
;; do not clear the other init BSS variables + STACK: too late.
; kernel startup stack
global
init_tos
resw
512
init_tos:
; the last paragraph of conventional memory might become an MCB
resb
16
global
__init_end
__init_end:
init_end:
segment _DATA
; blockdev private stack
global
blk_stk_top
times
256
dw
0
blk_stk_top:
; clockdev private stack
global
clk_stk_top
View remainder of file in raw view
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