www.pudn.com > bootany.zip > BSTRAP.ASM
page 61,132
title Bstrap - update fixed disk bootstrap
subttl Code
page +
Code segment
assume cs:Code, ds:Code, es:Code, ss:Code
org 80h
parmLen db ?
parm db ?
org 100h
include bootany.inc
Bstrap proc far
mov SI,DS ; Get data segment
mov ES,SI ; Make sure the same
;
; Read current bootstrap record
;
mov AX,201h ; read 1 sector
lea BX,Boot ; buffer address
mov CX,1 ; cyl 0, sector 1
mov DX,80h ; head 0, drive 0
int 13h ; read fixed disk boot
jnc ReadOk ; Go on if ok
mov bx,2 ; write to stderr
mov cx,Err1l ; length of message
lea dx,Err1 ; message address
mov ah,40h ; write to stream
int 21h ; send message
jmp Exit ; Exit program
ReadOk:
;
; Read in file named as parm (boot program)
; First find the program name
;
sub CX,CX ; clear register
sub SI,SI ; clear register
mov CL,parmLen ; Get length of parm
cmp CL,0 ; Better be there
jbe NameError ; its not
lea DI,parm ; get name address
mov AL,' ' ; what we will ignore
repe scasb
jcxz NameError ; No parm - write msg
jmp NameThere ; it is
NameError:
mov bx,2 ; write to stderr
mov cx,NameErrl ; length of message
lea dx,NameErr ; message address
mov ah,40h ; write to stream
int 21h ; send message
jmp Exit
;
; Found the name - Open and Read the file
;
NameThere:
dec DI ; Point to first byte
inc CX ; Correct the count
mov BX,CX ; get bytes left
mov [BX+DI],BYTE PTR 0 ; move in terminator
mov DX,DI ; Get file name start
sub AL,AL ; Open for read
mov AH,3dh ; Open function
int 21h ; Call DOS
jc FileError
lea DX,Boot ; buffer address
mov CX,PartAddr ; maximum boot length
mov BX,AX ; read from file
mov AH,3fh ; read from stream
int 21h ; dos service
jnc FileOk ; continue if file ok
FileError:
mov AH,3Eh ; Close the file
int 21h ; dos service
mov BX,2 ; write to stderr
mov CX,Err2l ; length of message
lea DX,Err2 ; message address
mov AH,40h ; write to stream
int 21h ; send message
jmp Exit ; Exit program
;
; The new boot program is not in our "in-memory" copy of the
; boot sector
;
FileOk:
;
; Close the file
;
mov AH,3Eh ; Close the file
int 21h ; dos service
;
; Update the boot sector with User Data
; Put out first message
;
mov bx,2 ; write to stderr
mov cx,Msg1l ; length of message
lea dx,Msg1 ; message address
mov ah,40h ; write to stream
int 21h ; send message
mov CX,max_partitions ; get loop count
PartLoop:
;
; Find out what partition this Function Key will be for
;
mov Index,CX ; Save index
sub CL,max_partitions+1 ; get negative index
neg CL ; turn positive
add CL,Numeric ; make displayable
mov Q1FKey,CL ; move into message
mov Q2FKey,CL ; move into message
mov Q3FKey,CL ; move into message
mov AL,max_partitions ; get max value
add AL,Numeric ; make displayable
mov Q1Max,AL ; move into message
mov BX,2 ; write to stderr
mov CX,Q1l ; length of message
lea DX,Q1 ; message address
mov AH,40h ; write to stream
int 21h ; send message
call GetChar ; Get the number
cmp AL,'0' ; See if '0'
jne NoExit ; If not continue
jmp TestNumLock ; Exit loop
NoExit:
cmp AL,'1' ; See if valid value
jl PartError ; No - reprompt
cmp AL,Numeric+max_partitions ; Check max value
ja PartError ; Too big - reprompt
mov Q2Pnum,AL ; Save part number
mov Err3P,AL ; Save part number
sub AL,Numeric+1 ; Turn into index
push AX ; Save for later
mov AH,SIZE PartData ; Get entry size
mul AH ; Get offset into table
mov Data,AX ; Get data address
mov BX,AX ; Get data address
pop AX ; Restore value
mov AH,SIZE PartitionEntry ; Get entry size
mul AH ; Get offset into table
mov Entry,AX ; Get entry address
cmp part.partition[BX],0 ; Already in use?
je BootTest ; No - use it
mov BX,2 ; write to stderr
mov CX,Err3l ; length of message
lea DX,Err3 ; message address
mov AH,40h ; write to stream
int 21h ; send message
PartError:
mov CX,Index ; restore index
jmp Partloop
BootTest:
; Check to see if the partition is marked bootable -
; If not, see if it should be made bootable
;
mov BX,Entry ; Get Entry address
cmp partitionTable.BootIndicator[BX],0 ; Can partition boot
jne PartBoot ; Yes - use it
push AX ; Save for later
mov BX,2 ; write to stderr
mov CX,Q2l ; length of message
lea DX,Q2 ; message address
mov AH,40h ; write to stream
int 21h ; send message
call GetChar ; Get the number
pop CX ; Restore value
and AL,0DFh ; Convert to upper case
cmp AL,'Y' ; See if 'Y'
je MakeBoot ; Make it bootable
cmp AL,'N' ; See if 'N'
jne BootTest ; Bad reply
jmp PartError ; Don't make it boot
MakeBoot:
mov partitionTable.BootIndicator[BX],80h ; Turn on boot flag
mov AX,CX ; Restore part #
PartBoot:
mov BX,Data ; Get table offset
mov AL,Q2Pnum ; Get part number
sub AL,Numeric ; Convert to binary
mov part.partition[BX],AL ; Save partition #
PartBootLoop:
;
; Get partitition description from user
;
mov BX,2 ; write to stderr
mov CX,Q3l ; length of message
lea DX,Q3 ; message address
mov AH,40h ; write to stream
int 21h ; send message
mov CX,part_text_len ; set to text length
cld ; copy forward
lea DI,part.text ; Get base
add DI,Data ; Add entry offset
mov AL,' ' ; Get data start
rep stosb ; Copy the data
lea DX,TextBuffer ; get input area addr
mov AH,10 ; Buffered Input Code
int 21h ; Get data
sub CX,CX ; Clear register
mov CL,TextBuffer+1 ; Get length entered
jcxz PartBootLoop ; Reprompt if null
cld ; copy forward
lea DI,part.text ; Get base
add DI,Data ; Add entry offset
lea SI,TextBuffer+2 ; Get data start
rep movsb ; Copy the data
mov CX,Index ; Restore loop index
loop NextPart ; Set up next partition
jmp TestNumLock
NextPart:
jmp PartLoop
;
; See if Num Lock should be turned off
;
TestNumLock:
mov bx,2 ; write to stderr
mov cx,Q4l ; length of message
lea dx,Q4 ; message address
mov ah,40h ; write to stream
int 21h ; send message
call GetChar ; Get the number
and AL,0DFh ; Convert to upper case
cmp AL,'Y' ; See if 'Y'
je ResetTable ; Off is default
cmp AL,'N' ; See if 'N'
jne TestNumLock ; Bad reply
mov AL,NumLockOn ; Get NumLock on mask
mov bootOpts.numlockMask,AL ; Reset Mask
;
; Swap the BootIndicator with the System Id to insure that there
; will be only one bootable partition at a time.
;
ResetTable:
mov CX,max_partitions ; Get number of parts
sub BX,BX ; Clear index
ResetTableLoop:
mov AL,partitionTable.BootIndicator[BX] ; get indicator
cmp AL,80h ; bootable partition?
jne PartOk ; don't mess with it
mov AL,partitionTable.SystemId[BX] ; Get System ID
mov partitionTable.BootIndicator[BX],AL ; Save here
mov partitionTable.SystemId[BX],80h ; Make System ID inv.
PartOk:
add BX,SIZE PartitionEntry ; Next Entry
loop ResetTableLoop
;
; Rewrite the boot record
;
lea BX,Boot ; buffer address
mov CX,1 ; cyl 0, sector 1
mov DX,80h ; head 0, drive 0
mov AX,301h ; write 1 sector
int 13h ; update boot record
jc Exit ; exit if error
;
; Write out message
;
mov BX,2 ; write to stderr
mov CX,Msgl ; length of message
lea DX,Msg ; message address
mov AH,40h ; write to stream
int 21h ; send message
Exit:
int 20h ; exit program
TextBuffer db 16,0
db 16 dup(0)
Msg1 db 13,10,' may be used to end the install '
db 'at any time',10
Msg1l equ $-Msg1
Q1 db 13,10,'What partition should be assigned to F'
Q1Fkey db '#? (1-'
Q1Max db '#, 0 to end) '
Q1l equ $-Q1
Q2 db 13,10,'Partition '
Q2Pnum db '# is not bootable.',13,10
db ' Reply Y to make it bootable, '
db 'N to assign F'
Q2Fkey db '# to a new partition. '
Q2l equ $-Q2
Q3 db 13,10,'Enter partition description to be assigned to F'
Q3Fkey db '# (15 chars max) '
Q3l equ $-Q3
Q4 db 13,10,'Do you want Num Lock turned off at boot? '
db '(Y or N) '
Q4l equ $-Q4
Err1 db 13,10,'Error Reading Boot Sector'
Err1l equ $-Err1
NameErr db 13,10,'Invalid file name for new boot program'
NameErrl equ $-NameErr
Err2 db 13,10,'Error Reading New Boot Program'
Err2l equ $-Err2
Err3 db 13,10,'Partition '
Err3P db '# is already defined'
Err3l equ $-Err3
msg db 13,10,'Boot record updated.',13,10
msgl equ $-msg
Index dw 0
Entry dw 0
Data dw 0
Boot db DataAddr dup(?)
part PartData max_partitions dup(<>)
bootOpts BootData <>
partitionTable PartitionEntry 4 dup(<>)
Validation db 2 dup(0)
Bstrap endp
GetChar proc near
mov AH,1 ; Get keyboard input
int 21h
cmp AL,0
jne GetCharRet
mov AH,1 ; Get extended code
int 21h
sub AL,AL ; show bad, not ASCII
GetCharRet:
ret
GetChar endp
Code ends
end Bstrap