mirror of
https://github.com/reactos/reactos.git
synced 2024-12-30 19:14:31 +00:00
425bbb1543
- Added assembler versions of memcmp() memcpy() memset() - Implemented Int386() so that real-mode interrupts can be called from C-code - Removed unnecessary call in DbgPrint() macro (freeldr.sys is ~16k smaller now) - 64-bit lba sector addressing for disk calls - Re-coded biosdisk.S as i386disk.c - Re-coded mem.S as i386mem.c - Re-coded rtlcode.S as i386rtl.c - Cleaned up i386trap.S so that it only saves the registers once. - Re-coded biosvid.S as i386vid.c - Video fade in/out - VESA text modes supported now - Offscreen buffering to remove flicker - Standardized format of boot sector so that BootPartition is stored right before 0xaa55 - Prefixed all file system functions with 'Fs' svn path=/trunk/; revision=3782
505 lines
16 KiB
NASM
505 lines
16 KiB
NASM
; FAT32.ASM
|
|
; FAT32 Boot Sector
|
|
; Copyright (c) 1998, 2000, 2001, 2002 Brian Palmer
|
|
|
|
org 7c00h
|
|
|
|
segment .text
|
|
|
|
bits 16
|
|
|
|
start:
|
|
jmp short main
|
|
nop
|
|
|
|
OEMName db 'FrLdr1.0'
|
|
BytesPerSector dw 512
|
|
SectsPerCluster db 0
|
|
ReservedSectors dw 32
|
|
NumberOfFats db 2
|
|
MaxRootEntries dw 0 ; Always zero for FAT32 volumes
|
|
TotalSectors dw 0 ; Always zero for FAT32 volumes
|
|
MediaDescriptor db 0f8h
|
|
SectorsPerFat dw 0 ; Always zero for FAT32 volumes
|
|
SectorsPerTrack dw 0
|
|
NumberOfHeads dw 0
|
|
HiddenSectors dd 0
|
|
TotalSectorsBig dd 0
|
|
; FAT32 Inserted Info
|
|
SectorsPerFatBig dd 0
|
|
ExtendedFlags dw 0
|
|
FSVersion dw 0
|
|
RootDirStartCluster dd 0
|
|
FSInfoSector dw 0
|
|
BackupBootSector dw 6
|
|
Reserved1 times 12 db 0
|
|
; End FAT32 Inserted Info
|
|
BootDrive db 0
|
|
Reserved db 0
|
|
ExtendSig db 29h
|
|
SerialNumber dd 00000000h
|
|
VolumeLabel db 'NO NAME '
|
|
FileSystem db 'FAT32 '
|
|
|
|
main:
|
|
xor ax,ax ; Setup segment registers
|
|
mov ds,ax ; Make DS correct
|
|
mov es,ax ; Make ES correct
|
|
mov ss,ax ; Make SS correct
|
|
mov bp,7c00h
|
|
mov sp,7c00h ; Setup a stack
|
|
|
|
|
|
|
|
cmp BYTE [BYTE bp+BootDrive],BYTE 0xff ; If they have specified a boot drive then use it
|
|
jne CheckSectorsPerFat
|
|
|
|
mov [BYTE bp+BootDrive],dl ; Save the boot drive
|
|
|
|
|
|
|
|
CheckSectorsPerFat:
|
|
cmp WORD [BYTE bp+SectorsPerFat],byte 0x00 ; Check the old 16-bit value of SectorsPerFat
|
|
jnz CheckFailed ; If it is non-zero then exit with an error
|
|
CheckTotalSectors: ; Check the old 16-bit value of TotalSectors & MaxRootEntries
|
|
cmp DWORD [BYTE bp+MaxRootEntries],byte 0x00; by comparing the DWORD at offset MaxRootEntries to zero
|
|
jnz CheckFailed ; If it is non-zero then exit with an error
|
|
CheckFileSystemVersion:
|
|
cmp WORD [BYTE bp+FSVersion],byte 0x00 ; Check the file system version word
|
|
jna GetDriveParameters ; It is zero, so continue
|
|
CheckFailed:
|
|
jmp PrintFileSystemError ; If it is not zero then exit with an error
|
|
|
|
|
|
GetDriveParameters:
|
|
mov ax,0800h
|
|
mov dl,[BYTE bp+BootDrive] ; Get boot drive in dl
|
|
int 13h ; Request drive parameters from the bios
|
|
jnc CalcDriveSize ; If the call succeeded then calculate the drive size
|
|
|
|
; If we get here then the call to the BIOS failed
|
|
; so just set CHS equal to the maximum addressable
|
|
; size
|
|
mov cx,0ffffh
|
|
mov dh,cl
|
|
|
|
CalcDriveSize:
|
|
; Now that we have the drive geometry
|
|
; lets calculate the drive size
|
|
mov bl,ch ; Put the low 8-bits of the cylinder count into BL
|
|
mov bh,cl ; Put the high 2-bits in BH
|
|
shr bh,6 ; Shift them into position, now BX contains the cylinder count
|
|
and cl,3fh ; Mask off cylinder bits from sector count
|
|
; CL now contains sectors per track and DH contains head count
|
|
movzx eax,dh ; Move the heads into EAX
|
|
movzx ebx,bx ; Move the cylinders into EBX
|
|
movzx ecx,cl ; Move the sectors per track into ECX
|
|
inc eax ; Make it one based because the bios returns it zero based
|
|
inc ebx ; Make the cylinder count one based also
|
|
mul ecx ; Multiply heads with the sectors per track, result in edx:eax
|
|
mul ebx ; Multiply the cylinders with (heads * sectors) [stored in edx:eax already]
|
|
|
|
; We now have the total number of sectors as reported
|
|
; by the bios in eax, so store it in our variable
|
|
mov [BiosCHSDriveSize],eax
|
|
|
|
|
|
LoadExtraBootCode:
|
|
; First we have to load our extra boot code at
|
|
; sector 14 into memory at [0000:7e00h]
|
|
mov eax,0eh
|
|
add eax,DWORD [BYTE bp+HiddenSectors] ; Add the number of hidden sectors
|
|
mov cx,1
|
|
xor bx,bx
|
|
mov es,bx ; Read sector to [0000:7e00h]
|
|
mov bx,7e00h
|
|
call ReadSectors
|
|
jmp StartSearch
|
|
|
|
|
|
|
|
; Reads logical sectors into [ES:BX]
|
|
; EAX has logical sector number to read
|
|
; CX has number of sectors to read
|
|
ReadSectors:
|
|
cmp eax,DWORD [BiosCHSDriveSize] ; Check if they are reading a sector outside CHS range
|
|
jae ReadSectorsLBA ; Yes - go to the LBA routine
|
|
; If at all possible we want to use LBA routines because
|
|
; They are optimized to read more than 1 sector per read
|
|
|
|
pushad ; Save logical sector number & sector count
|
|
|
|
CheckInt13hExtensions: ; Now check if this computer supports extended reads
|
|
mov ah,0x41 ; AH = 41h
|
|
mov bx,0x55aa ; BX = 55AAh
|
|
mov dl,[BYTE bp+BootDrive] ; DL = drive (80h-FFh)
|
|
int 13h ; IBM/MS INT 13 Extensions - INSTALLATION CHECK
|
|
jc ReadSectorsCHS ; CF set on error (extensions not supported)
|
|
cmp bx,0xaa55 ; BX = AA55h if installed
|
|
jne ReadSectorsCHS
|
|
test cl,1 ; CX = API subset support bitmap
|
|
jz ReadSectorsCHS ; Bit 0, extended disk access functions (AH=42h-44h,47h,48h) supported
|
|
|
|
popad ; Restore sector count & logical sector number
|
|
|
|
ReadSectorsLBA:
|
|
pushad ; Save logical sector number & sector count
|
|
|
|
cmp cx,64 ; Since the LBA calls only support 0x7F sectors at a time we will limit ourselves to 64
|
|
jbe ReadSectorsSetupDiskAddressPacket ; If we are reading less than 65 sectors then just do the read
|
|
mov cx,64 ; Otherwise read only 64 sectors on this loop iteration
|
|
|
|
ReadSectorsSetupDiskAddressPacket:
|
|
mov [LBASectorsRead],cx
|
|
o32 push byte 0
|
|
push eax ; Put 64-bit logical block address on stack
|
|
push es ; Put transfer segment on stack
|
|
push bx ; Put transfer offset on stack
|
|
push cx ; Set transfer count
|
|
push byte 0x10 ; Set size of packet to 10h
|
|
mov si,sp ; Setup disk address packet on stack
|
|
|
|
|
|
mov dl,[BYTE bp+BootDrive] ; Drive number
|
|
mov ah,42h ; Int 13h, AH = 42h - Extended Read
|
|
int 13h ; Call BIOS
|
|
jc PrintDiskError ; If the read failed then abort
|
|
|
|
add sp,byte 0x10 ; Remove disk address packet from stack
|
|
|
|
popad ; Restore sector count & logical sector number
|
|
|
|
push bx
|
|
mov ebx,DWORD [LBASectorsRead]
|
|
add eax,ebx ; Increment sector to read
|
|
shl ebx,5
|
|
mov dx,es
|
|
add dx,bx ; Setup read buffer for next sector
|
|
mov es,dx
|
|
pop bx
|
|
|
|
sub cx,[LBASectorsRead]
|
|
jnz ReadSectorsLBA ; Read next sector
|
|
|
|
ret
|
|
|
|
LBASectorsRead:
|
|
dd 0
|
|
|
|
|
|
; Reads logical sectors into [ES:BX]
|
|
; EAX has logical sector number to read
|
|
; CX has number of sectors to read
|
|
ReadSectorsCHS:
|
|
popad ; Get logical sector number & sector count off stack
|
|
|
|
ReadSectorsCHSLoop:
|
|
pushad
|
|
xor edx,edx
|
|
movzx ecx,WORD [BYTE bp+SectorsPerTrack]
|
|
div ecx ; Divide logical by SectorsPerTrack
|
|
inc dl ; Sectors numbering starts at 1 not 0
|
|
mov cl,dl ; Sector in CL
|
|
mov edx,eax
|
|
shr edx,16
|
|
div WORD [BYTE bp+NumberOfHeads] ; Divide logical by number of heads
|
|
mov dh,dl ; Head in DH
|
|
mov dl,[BYTE bp+BootDrive] ; Drive number in DL
|
|
mov ch,al ; Cylinder in CX
|
|
ror ah,1 ; Low 8 bits of cylinder in CH, high 2 bits
|
|
ror ah,1 ; in CL shifted to bits 6 & 7
|
|
or cl,ah ; Or with sector number
|
|
mov ax,0201h
|
|
int 13h ; DISK - READ SECTORS INTO MEMORY
|
|
; AL = number of sectors to read, CH = track, CL = sector
|
|
; DH = head, DL = drive, ES:BX -> buffer to fill
|
|
; Return: CF set on error, AH = status (see AH=01h), AL = number of sectors read
|
|
|
|
jc PrintDiskError ; If the read failed then abort
|
|
|
|
popad
|
|
|
|
inc eax ; Increment Sector to Read
|
|
|
|
mov dx,es
|
|
add dx,byte 20h ; Increment read buffer for next sector
|
|
mov es,dx
|
|
|
|
loop ReadSectorsCHSLoop ; Read next sector
|
|
|
|
ret
|
|
|
|
|
|
|
|
|
|
; Displays a disk error message
|
|
; And reboots
|
|
PrintDiskError:
|
|
mov si,msgDiskError ; Bad boot disk message
|
|
call PutChars ; Display it
|
|
|
|
jmp Reboot
|
|
|
|
; Displays a file system error message
|
|
; And reboots
|
|
PrintFileSystemError:
|
|
mov si,msgFileSystemError ; FreeLdr not found message
|
|
call PutChars ; Display it
|
|
|
|
Reboot:
|
|
mov si,msgAnyKey ; Press any key message
|
|
call PutChars ; Display it
|
|
xor ax,ax
|
|
int 16h ; Wait for a keypress
|
|
int 19h ; Reboot
|
|
|
|
PutChars:
|
|
lodsb
|
|
or al,al
|
|
jz short Done
|
|
mov ah,0eh
|
|
mov bx,07h
|
|
int 10h
|
|
jmp short PutChars
|
|
Done:
|
|
retn
|
|
|
|
|
|
|
|
BiosCHSDriveSize dd 0
|
|
|
|
msgDiskError db 'Disk error',0dh,0ah,0
|
|
msgFileSystemError db 'File system error',0dh,0ah,0
|
|
msgAnyKey db 'Press any key to restart',0dh,0ah,0
|
|
|
|
times 509-($-$$) db 0 ; Pad to 509 bytes
|
|
|
|
BootPartition:
|
|
db 0
|
|
|
|
BootSignature:
|
|
dw 0aa55h ; BootSector signature
|
|
|
|
|
|
; End of bootsector
|
|
;
|
|
; Now starts the extra boot code that we will store
|
|
; at sector 14 on a FAT32 volume
|
|
;
|
|
; To remain multi-boot compatible with other operating
|
|
; systems we must not overwrite anything other than
|
|
; the bootsector which means we will have to use
|
|
; a different sector like 14 to store our extra boot code
|
|
|
|
|
|
|
|
StartSearch:
|
|
; Now we must get the first cluster of the root directory
|
|
mov eax,DWORD [BYTE bp+RootDirStartCluster]
|
|
cmp eax,0ffffff8h ; Check to see if this is the last cluster in the chain
|
|
jb ContinueSearch ; If not continue, if so then we didn't find freeldr.sys
|
|
jmp PrintFileNotFound
|
|
ContinueSearch:
|
|
mov bx,2000h
|
|
mov es,bx ; Read cluster to [2000:0000h]
|
|
call ReadCluster ; Read the cluster
|
|
|
|
|
|
; Now we have to find our way through the root directory to
|
|
; The OSLOADER.SYS file
|
|
xor bx,bx
|
|
mov bl,[BYTE bp+SectsPerCluster]
|
|
shl bx,4 ; BX = BX * 512 / 32
|
|
mov ax,2000h ; We loaded at 2000:0000
|
|
mov es,ax
|
|
xor di,di
|
|
mov si,filename
|
|
mov cx,11
|
|
rep cmpsb ; Compare filenames
|
|
jz FoundFile ; If same we found it
|
|
dec bx
|
|
jnz FindFile
|
|
jmp PrintFileNotFound
|
|
|
|
FindFile:
|
|
mov ax,es ; We didn't find it in the previous dir entry
|
|
add ax,2 ; So lets move to the next one
|
|
mov es,ax ; And search again
|
|
xor di,di
|
|
mov si,filename
|
|
mov cx,11
|
|
rep cmpsb ; Compare filenames
|
|
jz FoundFile ; If same we found it
|
|
dec bx ; Keep searching till we run out of dir entries
|
|
jnz FindFile ; Last entry?
|
|
|
|
; Get the next root dir cluster and try again until we run out of clusters
|
|
mov eax,DWORD [BYTE bp+RootDirStartCluster]
|
|
call GetFatEntry
|
|
mov [BYTE bp+RootDirStartCluster],eax
|
|
jmp StartSearch
|
|
|
|
FoundFile:
|
|
|
|
; Display "Loading FreeLoader..." message
|
|
mov si,msgLoading ; Loading message
|
|
call PutChars ; Display it
|
|
|
|
xor di,di ; ES:DI has dir entry
|
|
xor dx,dx
|
|
mov ax,WORD [es:di+14h] ; Get start cluster high word
|
|
shl eax,16
|
|
mov ax,WORD [es:di+1ah] ; Get start cluster low word
|
|
|
|
CheckStartCluster:
|
|
cmp eax,2 ; Check and see if the start cluster starts at cluster 2 or above
|
|
jnb CheckEndCluster ; If so then continue
|
|
jmp PrintFileSystemError ; If not exit with error
|
|
CheckEndCluster:
|
|
cmp eax,0ffffff8h ; Check and see if the start cluster is and end of cluster chain indicator
|
|
jb InitializeLoadSegment ; If not then continue
|
|
jmp PrintFileSystemError ; If so exit with error
|
|
|
|
InitializeLoadSegment:
|
|
mov bx,800h
|
|
mov es,bx
|
|
|
|
LoadFile:
|
|
cmp eax,0ffffff8h ; Check to see if this is the last cluster in the chain
|
|
jae LoadFileDone ; If so continue, if not then read the next one
|
|
push eax
|
|
xor bx,bx ; Load ROSLDR starting at 0000:8000h
|
|
push es
|
|
call ReadCluster
|
|
pop es
|
|
|
|
xor bx,bx
|
|
mov bl,[BYTE bp+SectsPerCluster]
|
|
shl bx,5 ; BX = BX * 512 / 16
|
|
mov ax,es ; Increment the load address by
|
|
add ax,bx ; The size of a cluster
|
|
mov es,ax
|
|
|
|
pop eax
|
|
push es
|
|
call GetFatEntry ; Get the next entry
|
|
pop es
|
|
|
|
jmp LoadFile ; Load the next cluster (if any)
|
|
|
|
LoadFileDone:
|
|
mov dl,[BYTE bp+BootDrive] ; Load boot drive into DL
|
|
mov dh,[BootPartition] ; Load boot partition into DH
|
|
xor ax,ax
|
|
push ax ; We loaded at 0000:8000
|
|
push WORD 8000h ; We will do a far return to 0000:8000h
|
|
retf ; Transfer control to ROSLDR
|
|
|
|
|
|
; Returns the FAT entry for a given cluster number
|
|
; On entry EAX has cluster number
|
|
; On return EAX has FAT entry for that cluster
|
|
GetFatEntry:
|
|
|
|
shl eax,2 ; EAX = EAX * 4 (since FAT32 entries are 4 bytes)
|
|
mov ecx,eax ; Save this for later in ECX
|
|
xor edx,edx
|
|
movzx ebx,WORD [BYTE bp+BytesPerSector]
|
|
push ebx
|
|
div ebx ; FAT Sector Number = EAX / BytesPerSector
|
|
movzx ebx,WORD [BYTE bp+ReservedSectors]
|
|
add eax,ebx ; FAT Sector Number += ReservedSectors
|
|
mov ebx,DWORD [BYTE bp+HiddenSectors]
|
|
add eax,ebx ; FAT Sector Number += HiddenSectors
|
|
pop ebx
|
|
dec ebx
|
|
and ecx,ebx ; FAT Offset Within Sector = ECX % BytesPerSector
|
|
; EAX holds logical FAT sector number
|
|
; ECX holds FAT entry offset
|
|
|
|
; Now we have to check the extended flags
|
|
; to see which FAT is the active one
|
|
; and use it, or if they are mirrored then
|
|
; no worries
|
|
movzx ebx,WORD [BYTE bp+ExtendedFlags] ; Get extended flags and put into ebx
|
|
and bx,0x0f ; Mask off upper 8 bits, now we have active fat in bl
|
|
jz LoadFatSector ; If fat is mirrored then skip fat calcs
|
|
cmp bl,[BYTE bp+NumberOfFats] ; Compare bl to number of fats
|
|
jb GetActiveFatOffset
|
|
jmp PrintFileSystemError ; If bl is bigger than numfats exit with error
|
|
GetActiveFatOffset:
|
|
push eax ; Save logical FAT sector number
|
|
mov eax,[BYTE bp+SectorsPerFatBig] ; Get the number of sectors occupied by one fat in eax
|
|
mul ebx ; Multiplied by the active FAT index we have in ebx
|
|
pop edx ; Get logical FAT sector number
|
|
add eax,edx ; Add the current FAT sector offset
|
|
|
|
LoadFatSector:
|
|
push ecx
|
|
; EAX holds logical FAT sector number
|
|
; Check if we have already loaded it
|
|
cmp eax,DWORD [FatSectorInCache]
|
|
je LoadFatSectorAlreadyLoaded
|
|
|
|
mov DWORD [FatSectorInCache],eax
|
|
mov bx,7000h
|
|
mov es,bx
|
|
xor bx,bx ; We will load it to [7000:0000h]
|
|
mov cx,1
|
|
call ReadSectors
|
|
|
|
LoadFatSectorAlreadyLoaded:
|
|
mov bx,7000h
|
|
mov es,bx
|
|
pop ecx
|
|
mov eax,DWORD [es:ecx] ; Get FAT entry
|
|
and eax,0fffffffh ; Mask off reserved bits
|
|
|
|
ret
|
|
|
|
FatSectorInCache: ; This variable tells us which sector we currently have in memory
|
|
dd 0ffffffffh ; There is no need to re-read the same sector if we don't have to
|
|
|
|
|
|
; Reads cluster number in EAX into [ES:0000]
|
|
ReadCluster:
|
|
; StartSector = ((Cluster - 2) * SectorsPerCluster) + ReservedSectors + HiddenSectors;
|
|
|
|
dec eax
|
|
dec eax
|
|
xor edx,edx
|
|
movzx ebx,BYTE [BYTE bp+SectsPerCluster]
|
|
mul ebx
|
|
push eax
|
|
xor edx,edx
|
|
movzx eax,BYTE [BYTE bp+NumberOfFats]
|
|
mul DWORD [BYTE bp+SectorsPerFatBig]
|
|
movzx ebx,WORD [BYTE bp+ReservedSectors]
|
|
add eax,ebx
|
|
add eax,DWORD [BYTE bp+HiddenSectors]
|
|
pop ebx
|
|
add eax,ebx ; EAX now contains the logical sector number of the cluster
|
|
xor bx,bx ; We will load it to [ES:0000], ES loaded before function call
|
|
movzx cx,BYTE [BYTE bp+SectsPerCluster]
|
|
call ReadSectors
|
|
ret
|
|
|
|
|
|
; Displays a file not found error message
|
|
; And reboots
|
|
PrintFileNotFound:
|
|
mov si,msgFreeLdr ; FreeLdr not found message
|
|
call PutChars ; Display it
|
|
mov si,msgAnyKey ; Press any key message
|
|
call PutChars ; Display it
|
|
|
|
jmp Reboot
|
|
|
|
msgFreeLdr db 'freeldr.sys not found',0dh,0ah,0
|
|
filename db 'FREELDR SYS'
|
|
msgLoading db 'Loading FreeLoader...',0dh,0ah,0
|
|
|
|
|
|
times 1022-($-$$) db 0 ; Pad to 1022 bytes
|
|
|
|
dw 0aa55h ; BootSector signature
|