reactos/freeldr/bootsect/ext2.asm
Brian Palmer 367cfa7085 Changes in v1.7.4 (8/20/2002) (brianp)
- Boot sector code now reports to freeldr.sys the partition
  that it was installed on. This is specified by a byte
  value in the boot sector code. By default the boot partition
  is set to zero which indicates the active (bootable)
  partition, unless the installer sets the value to non-zero.
  If FreeLoader is installed on a partition other than
  the active (bootable) partition then the installer must
  set this byte to that partition number. Otherwise
  FreeLoader will not be able to find freeldr.ini.
- i386trap.S: Added debug macros BREAKPOINT(),
  INSTRUCTION_BREAKPOINTX(), MEMORY_READWRITE_BREAKPOINTX(), &
  MEMORY_WRITE_BREAKPOINTX().
- partition.c (DiskGetPartitionEntry): Add the relative offset
  of the extended partition to the partitions start sector.
- ext2.c (Ext2ReadBlockPointerList, Ext2CopyIndirectBlockPointers,
  Ext2CopyDoubleIndirectBlockPointers, Ext2CopyTripleIndirectBlockPointers):
  Rewrote the block pointer functions so they actually work.
- ini_init.c (IniFileInitialize, IniOpenIniFile): Looks for freeldr.ini
  on both the active (bootable) partition and the partition
  passed in from the boot sector code.
- meminit.c (MmInitializeMemoryManager, MmFixupSystemMemoryMap,
  MmGetEndAddressOfAnyMemory, MmGetAddressablePageCountIncludingHoles,
  MmInitPageLookupTable): Fixed bug that would cause FreeLoader to
  have an off-by-one error when accessing the last entry in the
  page lookup table on systems with 4GB of memory (or memory mapped
  at the end of the address space).

svn path=/trunk/; revision=3372
2002-08-21 03:32:49 +00:00

653 lines
21 KiB
NASM

; EXT2.ASM
; EXT2 Boot Sector
; Copyright (c) 2002 Brian Palmer
; [bp-0x04] Here we will store the number of sectors per track
; [bp-0x08] Here we will store the number of heads
; [bp-0x0c] Here we will store the size of the disk as the BIOS reports in CHS form
; [bp-0x10] Here we will store the number of LBA sectors read
SECTORS_PER_TRACK equ 0x04
NUMBER_OF_HEADS equ 0x08
BIOS_CHS_DRIVE_SIZE equ 0x0C
LBA_SECTORS_READ equ 0x10
EXT2_ROOT_INO equ 2
EXT2_S_IFMT equ 0f0h
EXT2_S_IFREG equ 080h
org 7c00h
segment .text
bits 16
start:
jmp short main
nop
BootDrive db 0x80
BootPartition db 0
;SectorsPerTrack db 63 ; Moved to [bp-SECTORS_PER_TRACK]
;NumberOfHeads dw 16 ; Moved to [bp-NUMBER_OF_HEADS]
;BiosCHSDriveSize dd (1024 * 1024 * 63) ; Moved to [bp-BIOS_CHS_DRIVE_SIZE]
;LBASectorsRead dd 0 ; Moved to [bp-LBA_SECTORS_READ]
Ext2VolumeStartSector dd 263088 ; Start sector of the ext2 volume
Ext2BlockSize dd 2 ; Block size in sectors
Ext2BlockSizeInBytes dd 1024 ; Block size in bytes
Ext2PointersPerBlock dd 256 ; Number of block pointers that can be contained in one block
Ext2GroupDescPerBlock dd 32 ; Number of group descriptors per block
Ext2FirstDataBlock dd 1 ; First data block (1 for 1024-byte blocks, 0 for bigger sizes)
Ext2InodesPerGroup dd 2048 ; Number of inodes per group
Ext2InodesPerBlock dd 8 ; Number of inodes per block
Ext2ReadEntireFileLoadSegment:
dw 0
Ext2InodeIndirectPointer:
dd 0
Ext2InodeDoubleIndirectPointer:
dd 0
Ext2BlocksLeftToRead:
dd 0
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,7b00h ; Setup a stack
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
mov [BYTE bp-NUMBER_OF_HEADS],eax ; Save number of heads
mov [BYTE bp-SECTORS_PER_TRACK],ecx ; Save number of sectors per track
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 [BYTE bp-BIOS_CHS_DRIVE_SIZE],eax
LoadExtraBootCode:
; First we have to load our extra boot code at
; sector 1 into memory at [0000:7e00h]
;mov eax,01h
xor eax,eax
inc eax ; Read logical sector 1, EAX now = 1
mov cx,1 ; Read one sector
mov bx,7e00h ; Read sector to [0000:7e00h]
call ReadSectors
jmp LoadRootDirectory
; Reads ext2 group descriptor into [7000:8000]
; We read it to this arbitrary location so
; it will not cross a 64k boundary
; EAX has group descriptor number to read
Ext2ReadGroupDesc:
shl eax,5 ; Group = (Group * sizeof(GROUP_DESCRIPTOR) /* 32 */)
xor edx,edx
div DWORD [BYTE bp+Ext2GroupDescPerBlock] ; Group = (Group / Ext2GroupDescPerBlock)
add eax,DWORD [BYTE bp+Ext2FirstDataBlock] ; Group = Group + Ext2FirstDataBlock + 1
inc eax ; EAX now has the group descriptor block number
; EDX now has the group descriptor offset in the block
; Adjust the read offset so that the
; group descriptor is read to 7000:8000
mov ebx,78000h
sub ebx,edx
shr ebx,4
mov es,bx
xor bx,bx
; Everything is now setup to call Ext2ReadBlock
; Instead of using the call instruction we will
; just put Ext2ReadBlock right after this routine
; Reads ext2 block into [ES:BX]
; EAX has logical block number to read
Ext2ReadBlock:
mov ecx,DWORD [BYTE bp+Ext2BlockSize]
mul ecx
jmp ReadSectors
; Reads ext2 inode into [6000:8000]
; We read it to this arbitrary location so
; it will not cross a 64k boundary
; EAX has inode number to read
Ext2ReadInode:
dec eax ; Inode = Inode - 1
xor edx,edx
div DWORD [BYTE bp+Ext2InodesPerGroup] ; Inode = (Inode / Ext2InodesPerGroup)
mov ebx,eax ; EBX now has the inode group number
mov eax,edx
xor edx,edx
div DWORD [BYTE bp+Ext2InodesPerBlock] ; Inode = (Inode / Ext2InodesPerBlock)
shl edx,7 ; FIXME: InodeOffset *= 128 (make the array index a byte offset)
; EAX now has the inode offset block number from inode table
; EDX now has the inode offset in the block
; Save the inode values and put the group
; descriptor number in EAX and read it in
push edx
push eax
mov eax,ebx
call Ext2ReadGroupDesc
; Group descriptor has been read, now
; grab the inode table block number from it
push WORD 7000h
pop es
mov di,8008h
pop eax ; Restore inode offset block number from stack
add eax,DWORD [es:di] ; Add the inode table start block
; Adjust the read offset so that the
; inode we want is read to 6000:8000
pop edx ; Restore inode offset in the block from stack
mov ebx,68000h
sub ebx,edx
shr ebx,4
mov es,bx
xor bx,bx
call Ext2ReadBlock
ret
; Reads logical sectors into [ES:BX]
; EAX has logical sector number to read
; CX has number of sectors to read
ReadSectors:
add eax,DWORD [BYTE bp+Ext2VolumeStartSector] ; Add the start of the volume
cmp eax,DWORD [BYTE bp-BIOS_CHS_DRIVE_SIZE] ; 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,byte 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 [BYTE bp-LBA_SECTORS_READ],cx
mov WORD [BYTE bp-LBA_SECTORS_READ+2],0
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 [BYTE bp-LBA_SECTORS_READ]
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,[BYTE bp-LBA_SECTORS_READ]
jnz ReadSectorsLBA ; Read next sector
ret
; 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
mov ecx,DWORD [BYTE bp-SECTORS_PER_TRACK]
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-NUMBER_OF_HEADS] ; 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
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
call PutCharsCallBios
jmp short PutChars
PutCharsCallBios:
mov ah,0eh
mov bx,07h
int 10h
retn
Done:
mov al,0dh
call PutCharsCallBios
mov al,0ah
call PutCharsCallBios
retn
msgDiskError db 'Disk error',0
msgAnyKey db 'Press any key to restart',0
times 510-($-$$) db 0 ; Pad to 510 bytes
dw 0aa55h ; BootSector signature
; End of bootsector
;
; Now starts the extra boot code that we will store
; at sector 1 on a EXT2 volume
LoadRootDirectory:
mov eax,EXT2_ROOT_INO ; Put the root directory inode number in EAX
call Ext2ReadInode ; Read in the inode
; Point ES:DI to the inode structure at 6000:8000
push WORD 6000h
pop es
mov di,8000h
push di
push es ; Save these for later
; Get root directory size from inode structure
mov eax,DWORD [es:di+4]
push eax
; Now that the inode has been read in load
; the root directory file data to 0000:8000
call Ext2ReadEntireFile
; Since the root directory was loaded to 0000:8000
; then add 8000h to the root directory's size
pop eax
mov edx,8000h ; Set EDX to the current offset in the root directory
add eax,edx ; Initially add 8000h to the size of the root directory
SearchRootDirectory:
push edx ; Save current offset in root directory
push eax ; Save the size of the root directory
; Now we have to convert the current offset
; in the root directory to a SEGMENT:OFFSET pair
mov eax,edx
xor edx,edx
mov ecx,16
div ecx ; Now AX:DX has segment & offset
mov es,ax
mov di,dx
push di ; Save the start of the directory entry
add di,byte 8 ; Add the offset to the filename
mov si,filename
mov cl,11
rep cmpsb ; Compare the file names
pop di
pop eax
pop edx
jz FoundFile
; Nope, didn't find it in this entry, keep looking
movzx ecx,WORD [es:di+4]
add edx,ecx
; Check to see if we have reached the
; end of the root directory
cmp edx,eax
jb SearchRootDirectory
jmp PrintFileNotFound
FoundFile:
mov eax,[es:di] ; Get inode number from directory entry
call Ext2ReadInode ; Read in the inode
; Point ES:DI to the inode structure at 6000:8000
pop es
pop di ; These were saved earlier
mov cx,[es:di] ; Get the file mode so we can make sure it's a regular file
and ch,EXT2_S_IFMT ; Mask off everything but the file type
cmp ch,EXT2_S_IFREG ; Make sure it's a regular file
je LoadFreeLoader
jmp PrintRegFileError
LoadFreeLoader:
mov si,msgLoading ; "Loading FreeLoader..." message
call PutChars ; Display it
call Ext2ReadEntireFile ; Read freeldr.sys to 0000:8000
mov dl,[BYTE bp+BootDrive]
mov dh,[BYTE bp+BootPartition]
push byte 0 ; We loaded at 0000:8000
push WORD 8000h ; We will do a far return to 0000:8000h
retf ; Transfer control to FreeLoader
; Reads ext2 file data into [0000:8000]
; This function assumes that the file's
; inode has been read in to 6000:8000 *and*
; ES:DI points to 6000:8000
; This will load all the blocks up to
; and including the double-indirect pointers.
; This should be sufficient because it
; allows for ~64MB which is much bigger
; than we need for a boot loader.
Ext2ReadEntireFile:
; Reset the load segment
mov WORD [BYTE bp+Ext2ReadEntireFileLoadSegment],800h
; Now we must calculate how
; many blocks to read in
; We will do this by rounding the
; file size up to the next block
; size and then dividing by the block size
mov eax,DWORD [BYTE bp+Ext2BlockSizeInBytes] ; Get the block size in bytes
push eax
dec eax ; Ext2BlockSizeInBytes -= 1
add eax,DWORD [es:di+4] ; Add the file size
xor edx,edx
pop ecx ; Divide by the block size in bytes
div ecx ; EAX now contains the number of blocks to load
push eax
; Make sure the file size isn't zero
cmp eax,byte 0
jnz Ext2ReadEntireFile2
jmp PrintFileSizeError
Ext2ReadEntireFile2:
; Save the indirect & double indirect pointers
mov edx,DWORD [es:di+0x58] ; Get indirect pointer
mov [BYTE bp+Ext2InodeIndirectPointer],edx ; Save indirect pointer
mov edx,DWORD [es:di+0x5c] ; Get double indirect pointer
mov [BYTE bp+Ext2InodeDoubleIndirectPointer],edx ; Save double indirect pointer
; Now copy the direct pointers to 7000:0000
; so that we can call Ext2ReadDirectBlocks
push ds ; Save DS
push es
push WORD 7000h
pop es
pop ds
mov si,8028h
xor di,di ; DS:SI = 6000:8028 ES:DI = 7000:0000
mov cx,24 ; Moving 24 words of data
rep movsw
pop ds ; Restore DS
; Now we have all the block pointers in the
; right location so read them in
pop eax ; Restore the total number of blocks in this file
xor ecx,ecx ; Set the max count of blocks to read to 12
mov cl,12 ; which is the number of direct block pointers in the inode
call Ext2ReadDirectBlockList
; Check to see if we actually have
; blocks left to read
cmp eax,byte 0
jz Ext2ReadEntireFileDone
; Now we have read all the direct blocks in
; the inode. So now we have to read the indirect
; block and read all it's direct blocks
push eax ; Save the total block count
mov eax,DWORD [BYTE bp+Ext2InodeIndirectPointer] ; Get the indirect block pointer
push WORD 7000h
pop es
xor bx,bx ; Set the load address to 7000:0000
call Ext2ReadBlock ; Read the block
; Now we have all the block pointers from the
; indirect block in the right location so read them in
pop eax ; Restore the total block count
mov ecx,DWORD [BYTE bp+Ext2PointersPerBlock] ; Get the number of block pointers that one block contains
call Ext2ReadDirectBlockList
; Check to see if we actually have
; blocks left to read
cmp eax,byte 0
jz Ext2ReadEntireFileDone
; Now we have read all the direct blocks from
; the inode's indirect block pointer. So now
; we have to read the double indirect block
; and read all it's indirect blocks
; (whew, it's a good thing I don't support triple indirect blocks)
mov [BYTE bp+Ext2BlocksLeftToRead],eax ; Save the total block count
mov eax,DWORD [BYTE bp+Ext2InodeDoubleIndirectPointer] ; Get the double indirect block pointer
push WORD 7800h
pop es
push es ; Save an extra copy of this value on the stack
xor bx,bx ; Set the load address to 7000:8000
call Ext2ReadBlock ; Read the block
pop es ; Put 7800h into ES (saved on the stack already)
xor di,di
Ext2ReadIndirectBlock:
mov eax,DWORD [es:di] ; Get indirect block pointer
add di,BYTE 4 ; Update DI for next array index
push es
push di
push WORD 7000h
pop es
xor bx,bx ; Set the load address to 7000:0000
call Ext2ReadBlock ; Read the indirect block
; Now we have all the block pointers from the
; indirect block in the right location so read them in
mov eax,DWORD [BYTE bp+Ext2BlocksLeftToRead] ; Restore the total block count
mov ecx,DWORD [BYTE bp+Ext2PointersPerBlock] ; Get the number of block pointers that one block contains
call Ext2ReadDirectBlockList
mov [BYTE bp+Ext2BlocksLeftToRead],eax ; Save the total block count
pop di
pop es
; Check to see if we actually have
; blocks left to read
cmp eax,byte 0
jnz Ext2ReadIndirectBlock
Ext2ReadEntireFileDone:
ret
; Reads a maximum number of blocks
; from an array at 7000:0000
; and updates the total count
; ECX contains the max number of blocks to read
; EAX contains the number of blocks left to read
; On return:
; EAX contians the new number of blocks left to read
Ext2ReadDirectBlockList:
cmp eax,ecx ; Compare it to the maximum number of blocks to read
ja CallExt2ReadDirectBlocks ; If it will take more blocks then just read all of the blocks
mov cx,ax ; Otherwise adjust the block count accordingly
CallExt2ReadDirectBlocks:
sub eax,ecx ; Subtract the number of blocks being read from the total count
push eax ; Save the new total count
call Ext2ReadDirectBlocks
pop eax ; Restore the total count
ret
; Reads a specified number of blocks
; from an array at 7000:0000
; CX contains the number of blocks to read
Ext2ReadDirectBlocks:
push WORD 7000h
pop es
xor di,di ; Set ES:DI = 7000:0000
Ext2ReadDirectBlocksLoop:
mov eax,[es:di] ; Get direct block pointer from array
add di,BYTE 4 ; Update DI for next array index
push cx ; Save number of direct blocks left
push es ; Save array segment
push di ; Save array offset
mov es,[BYTE bp+Ext2ReadEntireFileLoadSegment]
xor bx,bx ; Setup load address for next read
call Ext2ReadBlock ; Read the block (this updates ES for the next read)
mov [BYTE bp+Ext2ReadEntireFileLoadSegment],es ; Save updated ES
pop di ; Restore the array offset
pop es ; Restore the array segment
pop cx ; Restore the number of blocks left
loop Ext2ReadDirectBlocksLoop
; At this point all the direct blocks should
; be loaded and ES (Ext2ReadEntireFileLoadSegment)
; should be ready for the next read.
ret
; Displays a file not found error message
; And reboots
PrintFileNotFound:
mov si,msgFreeLdr ; FreeLdr not found message
jmp short DisplayAndRebootIt
; Displays a file size is 0 error
; And reboots
PrintFileSizeError:
mov si,msgFileSize ; Error message
jmp short DisplayAndRebootIt
; Displays a file is not a regular file error
; And reboots
PrintRegFileError:
mov si,msgRegFile ; Error message
DisplayAndRebootIt:
call PutChars ; Display it
jmp Reboot
msgFreeLdr db 'freeldr.sys not found',0
msgFileSize db 'File size is 0',0
msgRegFile db 'freeldr.sys isnt a regular file',0
filename db 'freeldr.sys'
msgLoading db 'Loading FreeLoader...',0
times 1022-($-$$) db 0 ; Pad to 1022 bytes
dw 0aa55h ; BootSector signature