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[BOOTSECTORS] Use the new header with SPDX license identifier for the ISO boot sector files I contributed to.

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Remove the unmaintained .asm files.

svn path=/trunk/; revision=75984
This commit is contained in:
Colin Finck 2017-09-28 20:21:45 +00:00
parent d20eaaf8ca
commit ea2806e13c
10 changed files with 13 additions and 4501 deletions
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179
reactos/boot/freeldr/bootsect/dosmbr.asm
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@ -1,179 +0,0 @@
;
; Normal DOS boot sector
;
; Ported to NASM from FreeDOS fdisk 1.2.0 by:
; Casper Hornstrup (chorns@users.sourceforge.net)
;
align 2, db 0
global _bootnormal_code
_bootnormal_code:
;-----------------------------------------------------------------------
; ENTRY (copied from freedos bootsector)
;
; IN: DL = boot drive
;OUT: DL = boot drive
;
;-----------------------------------------------------------------------
real_start: cli
cld
xor ax, ax
mov ss, ax ; initialize stack
mov ds, ax
mov bp, 0x7c00
lea sp, [bp-0x20]
sti
mov ax, 0x1FE0
mov es, ax
mov si, bp
mov di, bp
mov cx, 0x0100
rep movsw
jmp word 0x1FE0:0x7c00+ cont-real_start
cont: mov ds, ax
mov ss, ax
xor ax,ax
mov es,ax
; search for active partition
lea di, [bp+0x1be] ; start of partition table
test_next_for_active:
test byte [di],0x80
jne active_partition_found
add di,0x10 ; next table
cmp di, 07c00h+0x1fe; scanned beyond end of table ??
jb test_next_for_active
;*****************************************************************
call print
db 'No active partition found',0
WAIT_FOR_REBOOT:
jmp $
;*****************************************************************
trouble_reading_drive:
call print
db 'Read error while reading drive',0
jmp WAIT_FOR_REBOOT
;*****************************************************************
invalid_partition_code:
call print
db 'Partition signature != 55AA',0
jmp WAIT_FOR_REBOOT
;*****************************************************************
active_partition_found:
; call print
; db 'Loading active partition',0
call read_boot_sector
jc trouble_reading_drive
cmp word [es:0x7c00+0x1fe],0xaa55
jne invalid_partition_code
jmp word 0x0:0x7c00 ; and jump to boot sector code
;*****************************
; read_boot_sector
;
; IN: DI--> partition info
;OUT:CARRY
;*****************************
read_boot_sector:
; /* check for LBA support */
mov bx,0x55aa
mov ah,0x41
int 0x13
jc StandardBios ; if (regs.b.x != 0xaa55 || (regs.flags & 0x01))
cmp bx,0xaa55 ; goto StandardBios;
jne StandardBios
; /* if DAP cannot be used, don't use LBA */
; if ((regs.c.x & 1) == 0)
; goto StandardBios;
test cl,1
jz StandardBios
jmp short LBABios
_bios_LBA_address_packet:
db 0x10
db 0
db 4 ; read four sectors - why not
db 0
dw 0x7c00 ; fixed boot address for DOS sector
dw 0x0000
_bios_LBA_low dw 0
_bios_LBA_high dw 0
dw 0,0
LBABios:
; copy start address of partition to DAP
mov ax,[di+8]
mov [0x7c00+ (_bios_LBA_low-real_start)],ax
mov ax,[di+8+2]
mov [0x7c00+ (_bios_LBA_high-real_start)],ax
mov ax,0x4200 ; regs.a.x = LBA_READ;
mov si,0x7c00+ (_bios_LBA_address_packet-real_start); regs.si = FP_OFF(&dap);
int 0x13
ret
;*****************************************************************
; read disk, using standard BIOS
;
StandardBios:
mov ax,0x0204 ; regs.a.x = 0x0201;
mov bx,0x7c00 ; regs.b.x = FP_OFF(buffer);
mov cx,[di+2] ; regs.c.x =
; ((chs.Cylinder & 0xff) << 8) + ((chs.Cylinder & 0x300) >> 2) +
; chs.Sector;
; that was easy ;-)
mov dh,[di+1] ; regs.d.b.h = chs.Head;
; regs.es = FP_SEG(buffer);
int 0x13
ret
;****** PRINT
; prints text after call to this function.
print_1char:
xor bx, bx ; video page 0
mov ah, 0x0E ; else print it
int 0x10 ; via TTY mode
print: pop si ; this is the first character
print1: lodsb ; get token
push si ; stack up potential return address
cmp al, 0 ; end of string?
jne print_1char ; until done
ret ; and jump to it
times 0x1fe-$+$$ db 0
db 0x55,0xaa

665
reactos/boot/freeldr/bootsect/ext2.asm
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@ -1,665 +0,0 @@
; EXT2.ASM
; EXT2 Boot Sector
; Copyright (c) 2002, 2003 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 ; Moved to end of boot sector to have a standard format across all boot sectors
;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
cmp BYTE [BYTE bp+BootDrive],BYTE 0xff ; If they have specified a boot drive then use it
jne GetDriveParameters
mov [BYTE bp+BootDrive],dl ; Save the boot drive
GetDriveParameters:
mov ah,08h
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,2 ; Low 8 bits of cylinder in CH, high 2 bits
; 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
; Sorry, need the space...
;msgAnyKey db 'Press any key to restart',0
msgAnyKey db 'Press any key',0
times 509-($-$$) db 0 ; Pad to 509 bytes
BootPartition db 0
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 0 ; push segment (0x0000)
mov eax, [0x8000 + 0xA8] ; load the RVA of the EntryPoint into eax
add eax, 0x8000 ; RVA -> VA
push ax ; push offset
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 contains 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 DisplayItAndReboot
; Displays a file size is 0 error
; And reboots
PrintFileSizeError:
mov si,msgFileSize ; Error message
jmp short DisplayItAndReboot
; Displays a file is not a regular file error
; And reboots
PrintRegFileError:
mov si,msgRegFile ; Error message
DisplayItAndReboot:
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

404
reactos/boot/freeldr/bootsect/fat.asm
View file

@ -1,404 +0,0 @@
; FAT.ASM
; FAT12/16 Boot Sector
; Copyright (c) 1998, 2001, 2002 Brian Palmer
; This is a FAT12/16 file system boot sector
; that searches the entire root directory
; for the file freeldr.sys and loads it into
; memory.
;
; The stack is set to 0000:7BF2 so that the first
; WORD pushed will be placed at 0000:7BF0
;
; The DWORD at 0000:7BFC or BP-04h is the logical
; sector number of the start of the data area.
;
; The DWORD at 0000:7BF8 or BP-08h is the total
; sector count of the boot drive as reported by
; the computers bios.
;
; The WORD at 0000:7BF6 or BP-0ah is the offset
; of the ReadSectors function in the boot sector.
;
; The WORD at 0000:7BF4 or BP-0ch is the offset
; of the ReadCluster function in the boot sector.
;
; The WORD at 0000:7BF2 or BP-0eh is the offset
; of the PutChars function in the boot sector.
;
; When it locates freeldr.sys on the disk it will
; load the first sector of the file to 0000:F800
; With the help of this sector we should be able
; to load the entire file off the disk, no matter
; how fragmented it is.
;
; We load the entire FAT table into memory at
; 7000:0000. This improves the speed of floppy disk
; boots dramatically.
BootSectorStackTop equ 0x7bf2
DataAreaStartHigh equ 0x2
DataAreaStartLow equ 0x4
BiosCHSDriveSizeHigh equ 0x6
BiosCHSDriveSizeLow equ 0x8
BiosCHSDriveSize equ 0x8
ReadSectorsOffset equ 0xa
ReadClusterOffset equ 0xc
PutCharsOffset equ 0xe
org 7c00h
segment .text
bits 16
start:
jmp short main
nop
OEMName db 'FrLdr1.0'
BytesPerSector dw 512
SectsPerCluster db 1
ReservedSectors dw 1
NumberOfFats db 2
MaxRootEntries dw 224
TotalSectors dw 2880
MediaDescriptor db 0f0h
SectorsPerFat dw 9
SectorsPerTrack dw 18
NumberOfHeads dw 2
HiddenSectors dd 0
TotalSectorsBig dd 0
BootDrive db 0xff
Reserved db 0
ExtendSig db 29h
SerialNumber dd 00000000h
VolumeLabel db 'NO NAME '
FileSystem db 'FAT12 '
main:
xor ax,ax
mov ss,ax
mov bp,7c00h
mov sp,BootSectorStackTop ; Setup a stack
mov ds,ax ; Make DS correct
mov es,ax ; Make ES correct
cmp BYTE [BYTE bp+BootDrive],BYTE 0xff ; If they have specified a boot drive then use it
jne GetDriveParameters
mov [BYTE bp+BootDrive],dl ; Save the boot drive
GetDriveParameters:
mov ah,08h
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 [BYTE bp-BiosCHSDriveSize],eax
; Now we must find our way to the first sector of the root directory
xor ax,ax
xor cx,cx
mov al,[BYTE bp+NumberOfFats] ; Number of fats
mul WORD [BYTE bp+SectorsPerFat] ; Times sectors per fat
add ax,WORD [BYTE bp+HiddenSectors]
adc dx,WORD [BYTE bp+HiddenSectors+2] ; Add the number of hidden sectors
add ax,WORD [BYTE bp+ReservedSectors] ; Add the number of reserved sectors
adc dx,cx ; Add carry bit
mov WORD [BYTE bp-DataAreaStartLow],ax ; Save the starting sector of the root directory
mov WORD [BYTE bp-DataAreaStartHigh],dx ; Save it in the first 4 bytes before the boot sector
mov si,WORD [BYTE bp+MaxRootEntries] ; Get number of root dir entries in SI
pusha ; Save 32-bit logical start sector of root dir
; DX:AX now has the number of the starting sector of the root directory
; Now calculate the size of the root directory
xor dx,dx
mov ax,0020h ; Size of dir entry
mul si ; Times the number of entries
mov bx,[BYTE bp+BytesPerSector]
add ax,bx
dec ax
div bx ; Divided by the size of a sector
; AX now has the number of root directory sectors
add [BYTE bp-DataAreaStartLow],ax ; Add the number of sectors of the root directory to our other value
adc [BYTE bp-DataAreaStartHigh],cx ; Now the first 4 bytes before the boot sector contain the starting sector of the data area
popa ; Restore root dir logical sector start to DX:AX
LoadRootDirSector:
mov bx,7e0h ; We will load the root directory sector
mov es,bx ; Right after the boot sector in memory
xor bx,bx ; We will load it to [0000:7e00h]
xor cx,cx ; Zero out CX
inc cx ; Now increment it to 1, we are reading one sector
xor di,di ; Zero out di
push es ; Save ES because it will get incremented by 20h
call ReadSectors ; Read the first sector of the root directory
pop es ; Restore ES (ES:DI = 07E0:0000)
SearchRootDirSector:
cmp [es:di],ch ; If the first byte of the directory entry is zero then we have
jz ErrBoot ; reached the end of the directory and FREELDR.SYS is not here so reboot
pusha ; Save all registers
mov cl,0xb ; Put 11 in cl (length of filename in directory entry)
mov si,filename ; Put offset of filename string in DS:SI
repe cmpsb ; Compare this directory entry against 'FREELDR SYS'
popa ; Restore all the registers
jz FoundFreeLoader ; If we found it then jump
dec si ; SI holds MaxRootEntries, subtract one
jz ErrBoot ; If we are out of root dir entries then reboot
add di,BYTE +0x20 ; Increment DI by the size of a directory entry
cmp di,0200h ; Compare DI to 512 (DI has offset to next dir entry, make sure we haven't gone over one sector)
jc SearchRootDirSector ; If DI is less than 512 loop again
jmp short LoadRootDirSector ; Didn't find FREELDR.SYS in this directory sector, try again
FoundFreeLoader:
; We found freeldr.sys on the disk
; so we need to load the first 512
; bytes of it to 0000:F800
; ES:DI has dir entry (ES:DI == 07E0:XXXX)
mov ax,WORD [es:di+1ah] ; Get start cluster
push ax ; Save start cluster
push WORD 0F80h ; FREELDR_BASE / 16 ; Put load segment on the stack and load it
pop es ; Into ES so that we load the cluster at 0000:F800
call ReadCluster ; Read the cluster
pop ax ; Restore start cluster of FreeLoader
; Save the addresses of needed functions so
; the helper code will know where to call them.
mov WORD [BYTE bp-ReadSectorsOffset],ReadSectors ; Save the address of ReadSectors
mov WORD [BYTE bp-ReadClusterOffset],ReadCluster ; Save the address of ReadCluster
mov WORD [BYTE bp-PutCharsOffset],PutChars ; Save the address of PutChars
; Now AX has start cluster of FreeLoader and we
; have loaded the helper code in the first 512 bytes
; of FreeLoader to 0000:F800. Now transfer control
; to the helper code. Skip the first three bytes
; because they contain a jump instruction to skip
; over the helper code in the FreeLoader image.
;ljmp16 0, FREELDR_BASE + 3
db 0EAh
dw 0F803h
dw 0
; Displays an error message
; And reboots
ErrBoot:
mov si,msgFreeLdr ; 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
; Displays a bad boot message
; And reboots
BadBoot:
mov si,msgDiskError ; Bad boot disk message
call PutChars ; Display it
jmp short Reboot
; Reads cluster number in AX into [ES:0000]
ReadCluster:
; StartSector = ((Cluster - 2) * SectorsPerCluster) + ReservedSectors + HiddenSectors;
dec ax ; Adjust start cluster by 2
dec ax ; Because the data area starts on cluster 2
xor ch,ch
mov cl,BYTE [BYTE bp+SectsPerCluster]
mul cx ; Times sectors per cluster
add ax,[BYTE bp-DataAreaStartLow] ; Add start of data area
adc dx,[BYTE bp-DataAreaStartHigh] ; Now we have DX:AX with the logical start sector of FREELDR.SYS
xor bx,bx ; We will load it to [ES:0000], ES loaded before function call
;mov cl,BYTE [BYTE bp+SectsPerCluster]; Sectors per cluster still in CX
;call ReadSectors
;ret
; Reads logical sectors into [ES:BX]
; DX:AX has logical sector number to read
; CX has number of sectors to read
ReadSectors:
; We can't just check if the start sector is
; in the BIOS CHS range. We have to check if
; the start sector + length is in that range.
pusha
dec cx
add ax,cx
adc dx,byte 0
cmp dx,WORD [BYTE bp-BiosCHSDriveSizeHigh] ; Check if they are reading a sector within CHS range
ja ReadSectorsLBA ; No - go to the LBA routine
jb ReadSectorsCHS ; Yes - go to the old CHS routine
cmp ax,WORD [BYTE bp-BiosCHSDriveSizeLow] ; Check if they are reading a sector within CHS range
jbe ReadSectorsCHS ; Yes - go to the old CHS routine
ReadSectorsLBA:
popa
ReadSectorsLBALoop:
pusha ; Save logical sector number & sector count
o32 push byte 0
push dx ; Put 64-bit logical
push ax ; block address on stack
push es ; Put transfer segment on stack
push bx ; Put transfer offset on stack
push byte 1 ; Set transfer count to 1 sector
push byte 0x10 ; Set size of packet to 10h
mov si,sp ; Setup disk address packet on stack
; We are so totally out of space here that I am forced to
; comment out this very beautifully written piece of code
; It would have been nice to have had this check...
;CheckInt13hExtensions: ; Now make sure 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 PrintDiskError ; CF set on error (extensions not supported)
; cmp bx,0xaa55 ; BX = AA55h if installed
; jne PrintDiskError
; test cl,1 ; CX = API subset support bitmap
; jz PrintDiskError ; Bit 0, extended disk access functions (AH=42h-44h,47h,48h) supported
; Good, we're here so the computer supports LBA disk access
; So finish the extended read
mov dl,[BYTE bp+BootDrive] ; Drive number
mov ah,42h ; Int 13h, AH = 42h - Extended Read
int 13h ; Call BIOS
jc BadBoot ; If the read failed then abort
add sp,byte 0x10 ; Remove disk address packet from stack
popa ; Restore sector count & logical sector number
inc ax ; Increment Sector to Read
adc dx,byte 0
push bx
mov bx,es
add bx,byte 20h ; Increment read buffer for next sector
mov es,bx
pop bx
loop ReadSectorsLBALoop ; Read next sector
ret
; Reads logical sectors into [ES:BX]
; DX:AX has logical sector number to read
; CX has number of sectors to read
; CarryFlag set on error
ReadSectorsCHS:
popa
ReadSectorsCHSLoop:
pusha
xchg ax,cx
xchg ax,dx
xor dx,dx
div WORD [BYTE bp+SectorsPerTrack]
xchg ax,cx
div WORD [BYTE bp+SectorsPerTrack] ; Divide logical by SectorsPerTrack
inc dx ; Sectors numbering starts at 1 not 0
xchg cx,dx
div WORD [BYTE bp+NumberOfHeads] ; Number of heads
mov dh,dl ; Head to DH, drive to DL
mov dl,[BYTE bp+BootDrive] ; Drive number
mov ch,al ; Cylinder in CX
ror ah,2 ; Low 8 bits of cylinder in CH, high 2 bits
; 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 BadBoot
popa
inc ax ;Increment Sector to Read
jnz NoCarryCHS
inc dx
NoCarryCHS:
push bx
mov bx,es
add bx,byte 20h
mov es,bx
pop bx
; Increment read buffer for next sector
loop ReadSectorsCHSLoop ; Read next sector
ret
msgDiskError db 'Disk error',0dh,0ah,0
msgFreeLdr db 'Ldr not found',0dh,0ah,0
; Sorry, need the space...
;msgAnyKey db 'Press any key to restart',0dh,0ah,0
;msgAnyKey db 'Press a key',0dh,0ah,0
filename db 'FREELDR SYS'
times 509-($-$$) db 0 ; Pad to 509 bytes
BootPartition:
db 0
BootSignature:
dw 0aa55h ; BootSector signature

507
reactos/boot/freeldr/bootsect/fat32.asm
View file

@ -1,507 +0,0 @@
; 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:
push es
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
pop es
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 FREELDR.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,0F80h ; FREELDR_BASE / 16
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:F800h
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
; Transfer execution to the bootloader
;ljmp16 0, FREELDR_BASE
db 0EAh
dw 0F800h
dw 0
; 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
mov bx, 9000h ; We will load it to [9000:0000h]
mov es, bx
; EAX holds logical FAT sector number
; Check if we have already loaded it
cmp eax,DWORD [FatSectorInCache]
je LoadFatSectorAlreadyLoaded
mov DWORD [FatSectorInCache],eax
xor bx,bx
mov cx,1
call ReadSectors
LoadFatSectorAlreadyLoaded:
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

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reactos/boot/freeldr/bootsect/isoboot.S
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@ -1,31 +1,14 @@
/*
* PROJECT: ReactOS Boot Sector for ISO file system (based on ISOLINUX)
* LICENSE: GNU GPLv2 or any later version as published by the Free Software Foundation
* PROGRAMMERS: H. Peter Anvin
* Michael K. Ter Louw
* Eric Kohl
* Timo Kreuzer <timo.kreuzer@reactos.org>
* Colin Finck <colin@reactos.org>
*
*****************************************************************************
*
* isolinux.asm
*
* A program to boot Linux kernels off a CD-ROM using the El Torito
* boot standard in "no emulation" mode, making the entire filesystem
* available. It is based on the SYSLINUX boot loader for MS-DOS
* floppies.
*
* Copyright 1994-2009 H. Peter Anvin - All Rights Reserved
* Copyright 2009 Intel Corporation *author: H. Peter Anvin
*
* This program 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, Inc., 53 Temple Place Ste 330,
* Boston MA 02111-1307, USA *either version 2 of the License, or
* (at your option) any later version *incorporated herein by reference.
*
*****************************************************************************/
* PROJECT: ReactOS Boot Sector for ISO file system (based on ISOLINUX)
* LICENSE: GPL-2.0+ (https://spdx.org/licenses/GPL-2.0+)
* PURPOSE: Booting ReactOS off a CD-ROM using the El Torito boot standard in "no emulation mode"
* COPYRIGHT: Copyright 1994-2009 H. Peter Anvin
* Copyright 2002 Michael K. Ter Louw
* Copyright 2002 Eric Kohl
* Copyright 2009 Intel Corporation *author: H. Peter Anvin
* Copyright 2011 Timo Kreuzer (timo.kreuzer@reactos.org)
* Copyright 2017 Colin Finck (colin@reactos.org)
*/
/* INCLUDES ******************************************************************/
#include <asm.inc>

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reactos/boot/freeldr/bootsect/isobtrt.asm
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@ -1,984 +0,0 @@
; ****************************************************************************
;
; isolinux.asm
;
; A program to boot Linux kernels off a CD-ROM using the El Torito
; boot standard in "no emulation" mode, making the entire filesystem
; available. It is based on the SYSLINUX boot loader for MS-DOS
; floppies.
;
; Copyright (C) 1994-2001 H. Peter Anvin
;
; This program 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, Inc., 675 Mass Ave, Cambridge MA 02139,
; USA; either version 2 of the License, or (at your option) any later
; version; incorporated herein by reference.
;
; ****************************************************************************
;
; THIS FILE IS A MODIFIED VERSION OF ISOLINUX.ASM
; MODIFICATION DONE BY MICHAEL K TER LOUW
; LAST UPDATED 3-9-2002
; SEE "COPYING" FOR INFORMATION ABOUT THE LICENSE THAT APPLIES TO THIS RELEASE
;
; ****************************************************************************
;
; This file is a modified version of ISOLINUX.ASM.
; Modification done by Eric Kohl
; Last update 04-25-2002
;
; ****************************************************************************
;
; This file is a modified version of ISOLINUX.ASM.
; (for ReactOS regression testing)
; Modification done by Christoph von Wittich
; Last update 08-27-2006
;
; ****************************************************************************
; Note: The Makefile builds one version with DEBUG_MESSAGES automatically.
;%define DEBUG_MESSAGES ; Uncomment to get debugging messages
; ---------------------------------------------------------------------------
; BEGIN THE BIOS/CODE/DATA SEGMENT
; ---------------------------------------------------------------------------
absolute 0400h
serial_base resw 4 ; Base addresses for 4 serial ports
absolute 0413h
BIOS_fbm resw 1 ; Free Base Memory (kilobytes)
absolute 046Ch
BIOS_timer resw 1 ; Timer ticks
absolute 0472h
BIOS_magic resw 1 ; BIOS reset magic
absolute 0484h
BIOS_vidrows resb 1 ; Number of screen rows
;
; Memory below this point is reserved for the BIOS and the MBR
;
absolute 1000h
trackbuf resb 8192 ; Track buffer goes here
trackbufsize equ $-trackbuf
; trackbuf ends at 3000h
struc open_file_t
file_sector resd 1 ; Sector pointer (0 = structure free)
file_left resd 1 ; Number of sectors left
endstruc
struc dir_t
dir_lba resd 1 ; Directory start (LBA)
dir_len resd 1 ; Length in bytes
dir_clust resd 1 ; Length in clusters
endstruc
MAX_OPEN_LG2 equ 2 ; log2(Max number of open files)
MAX_OPEN equ (1 << MAX_OPEN_LG2)
SECTORSIZE_LG2 equ 11 ; 2048 bytes/sector (El Torito requirement)
SECTORSIZE equ (1 << SECTORSIZE_LG2)
CR equ 13 ; Carriage Return
LF equ 10 ; Line Feed
retry_count equ 6 ; How patient are we with the BIOS?
absolute 5000h ; Here we keep our BSS stuff
DriveNo resb 1 ; CD-ROM BIOS drive number
DiskError resb 1 ; Error code for disk I/O
RetryCount resb 1 ; Used for disk access retries
TimeoutCount resb 1 ; Timeout counter
ISOFlags resb 1 ; Flags for ISO directory search
RootDir resb dir_t_size ; Root directory
CurDir resb dir_t_size ; Current directory
ISOFileName resb 64 ; ISO filename canonicalization buffer
ISOFileNameEnd equ $
alignb open_file_t_size
Files resb MAX_OPEN*open_file_t_size
section .text
org 7000h
start:
cli ; Disable interrupts
xor ax, ax ; ax = segment zero
mov ss, ax ; Initialize stack segment
mov sp, start ; Set up stack
mov ds, ax ; Initialize other segment registers
mov es, ax
mov fs, ax
mov gs, ax
sti ; Enable interrupts
cld ; Increment pointers
mov cx, 2048 >> 2 ; Copy the bootsector
mov si, 0x7C00 ; from 0000:7C00
mov di, 0x7000 ; to 0000:7000
rep movsd ; copy the program
jmp 0:relocate ; jump into relocated code
relocate:
; Display the banner and copyright
%ifdef DEBUG_MESSAGES
mov si, isolinux_banner ; si points to hello message
call writestr ; display the message
mov si,copyright_str
call writestr
%endif
; check if there is a mbr on the hdd if so boot from it
pusha
mov ax, 0201h
mov dx, 0080h
mov cx, 0001h
mov bx, trackbuf
int 13h
popa
jc .boot_cdrom ; could not read hdd
push ax
mov ax, word [trackbuf+510]
cmp ax, 0
je .boot_cdrom ; no boot sector found (hopefully there are no weird bootsectors which begin with 0)
pop ax
.boot_harddisk:
call crlf
; Boot first harddisk (drive 0x80)
mov ax, 0201h
mov dx, 0080h
mov cx, 0001h
mov bx, 7C00h
int 13h
jnc .go_hd
jmp kaboom
.go_hd:
mov ax, cs
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov dx, 0080h
jmp 0:0x7C00
.boot_cdrom:
; Save and display the boot drive number
mov [DriveNo], dl
%ifdef DEBUG_MESSAGES
mov si, startup_msg
call writemsg
mov al, dl
call writehex2
call crlf
%endif
; Now figure out what we're actually doing
; Note: use passed-in DL value rather than 7Fh because
; at least some BIOSes will get the wrong value otherwise
mov ax, 4B01h ; Get disk emulation status
mov dl, [DriveNo]
mov si, spec_packet
int 13h
jc near spec_query_failed ; Shouldn't happen (BIOS bug)
mov dl, [DriveNo]
cmp [sp_drive], dl ; Should contain the drive number
jne near spec_query_failed
%ifdef DEBUG_MESSAGES
mov si, spec_ok_msg
call writemsg
mov al, byte [sp_drive]
call writehex2
call crlf
%endif
found_drive:
; Get drive information
mov ah, 48h
mov dl, [DriveNo]
mov si, drive_params
int 13h
jnc params_ok
; mov si, nosecsize_msg No use in reporting this
; call writemsg
params_ok:
; Check for the sector size (should be 2048, but
; some BIOSes apparently think we're 512-byte media)
;
; FIX: We need to check what the proper behaviour
; is for getlinsec when the BIOS thinks the sector
; size is 512!!! For that, we need such a BIOS, though...
%ifdef DEBUG_MESSAGES
mov si, secsize_msg
call writemsg
mov ax, [dp_secsize]
call writehex4
call crlf
%endif
;
; Clear Files structures
;
mov di, Files
mov cx, (MAX_OPEN*open_file_t_size)/4
xor eax, eax
rep stosd
;
; Now, we need to sniff out the actual filesystem data structures.
; mkisofs gave us a pointer to the primary volume descriptor
; (which will be at 16 only for a single-session disk!); from the PVD
; we should be able to find the rest of what we need to know.
;
get_fs_structures:
mov eax, 16 ; Primary Volume Descriptor (sector 16)
mov bx, trackbuf
call getonesec
mov eax, [trackbuf+156+2]
mov [RootDir+dir_lba],eax
mov [CurDir+dir_lba],eax
%ifdef DEBUG_MESSAGES
mov si, rootloc_msg
call writemsg
call writehex8
call crlf
%endif
mov eax,[trackbuf+156+10]
mov [RootDir+dir_len],eax
mov [CurDir+dir_len],eax
%ifdef DEBUG_MESSAGES
mov si, rootlen_msg
call writemsg
call writehex8
call crlf
%endif
add eax,SECTORSIZE-1
shr eax,SECTORSIZE_LG2
mov [RootDir+dir_clust],eax
mov [CurDir+dir_clust],eax
%ifdef DEBUG_MESSAGES
mov si, rootsect_msg
call writemsg
call writehex8
call crlf
%endif
; Look for the "REACTOS" directory, and if found,
; make it the current directory instead of the root
; directory.
mov di,isolinux_dir
mov al,02h ; Search for a directory
call searchdir_iso
jnz .dir_found
mov si,no_dir_msg
call writemsg
jmp kaboom
.dir_found:
mov [CurDir+dir_len],eax
mov eax,[si+file_left]
mov [CurDir+dir_clust],eax
xor eax,eax ; Free this file pointer entry
xchg eax,[si+file_sector]
mov [CurDir+dir_lba],eax
mov di, isolinux_bin ; di points to Isolinux filename
call searchdir ; look for the file
jnz .isolinux_opened ; got the file
mov si, no_isolinux_msg ; si points to error message
call writemsg ; display the message
jmp kaboom ; fail boot
.isolinux_opened:
mov di, si ; save file pointer
%ifdef DEBUG_MESSAGES
mov si, filelen_msg
call writemsg
call writehex8
call crlf
%endif
mov ecx, eax ; calculate sector count
shr ecx, 11
test eax, 0x7FF
jz .full_sector
inc ecx
.full_sector:
%ifdef DEBUG_MESSAGES
mov eax, ecx
mov si, filesect_msg
call writemsg
call writehex8
call crlf
%endif
; use high segment, as some bios can fail, when offset is too big
mov bx, 0x0F80 ; FREELDR_BASE / 16 ; es = load segment
mov es, bx
xor ebx, ebx ; bx = load offset
mov si, di ; restore file pointer
mov cx, 0xFFFF ; load the whole file
call getfssec ; get the whole file
%ifdef DEBUG_MESSAGES
mov si, startldr_msg
call writemsg
call crlf
%endif
mov dl, [DriveNo] ; dl = boot drive
mov dh, 0 ; dh = boot partition
; Transfer execution to the bootloader
;ljmp16 0, FREELDR_BASE
db 0xEA
dw 0xF800
dw 0
;
; searchdir:
;
; Open a file
;
; On entry:
; DS:DI = filename
; If successful:
; ZF clear
; SI = file pointer
; DX:AX or EAX = file length in bytes
; If unsuccessful
; ZF set
;
;
; searchdir_iso is a special entry point for ISOLINUX only. In addition
; to the above, searchdir_iso passes a file flag mask in AL. This is useful
; for searching for directories.
;
alloc_failure:
xor ax,ax ; ZF <- 1
ret
searchdir:
xor al,al
searchdir_iso:
mov [ISOFlags],al
call allocate_file ; Temporary file structure for directory
jnz alloc_failure
push es
push ds
pop es ; ES = DS
mov si,CurDir
cmp byte [di],'\' ; If filename begins with slash
jne .not_rooted
inc di ; Skip leading slash
mov si,RootDir ; Reference root directory instead
.not_rooted:
mov eax,[si+dir_clust]
mov [bx+file_left],eax
mov eax,[si+dir_lba]
mov [bx+file_sector],eax
mov edx,[si+dir_len]
.look_for_slash:
mov ax,di
.scan:
mov cl,[di]
inc di
and cl,cl
jz .isfile
cmp cl,'\'
jne .scan
mov [di-1],byte 0 ; Terminate at directory name
mov cl,02h ; Search for directory
xchg cl,[ISOFlags]
push di
push cx
push word .resume ; Where to "return" to
push es
.isfile:
xchg ax,di
.getsome:
; Get a chunk of the directory
mov si,trackbuf
pushad
xchg bx,si
mov cx,1 ; load one sector
call getfssec
popad
.compare:
movzx eax, byte [si] ; Length of directory entry
cmp al, 33
jb .next_sector
mov cl, [si+25]
xor cl, [ISOFlags]
test cl, byte 8Eh ; Unwanted file attributes!
jnz .not_file
pusha
movzx cx, byte [si+32] ; File identifier length
add si, byte 33 ; File identifier offset
call iso_compare_names
popa
je .success
.not_file:
sub edx, eax ; Decrease bytes left
jbe .failure
add si, ax ; Advance pointer
.check_overrun:
; Did we finish the buffer?
cmp si, trackbuf+trackbufsize
jb .compare ; No, keep going
jmp short .getsome ; Get some more directory
.next_sector:
; Advance to the beginning of next sector
lea ax, [si+SECTORSIZE-1]
and ax, ~(SECTORSIZE-1)
sub ax, si
jmp short .not_file ; We still need to do length checks
.failure:
%ifdef DEBUG_MESSAGES
mov si, findfail_msg
call writemsg
call crlf
%endif
xor eax, eax ; ZF = 1
mov [bx+file_sector], eax
pop es
ret
.success:
mov eax, [si+2] ; Location of extent
mov [bx+file_sector], eax
mov eax, [si+10] ; Data length
push eax
add eax, SECTORSIZE-1
shr eax, SECTORSIZE_LG2
mov [bx+file_left], eax
pop eax
mov edx, eax
shr edx, 16
and bx, bx ; ZF = 0
mov si, bx
pop es
ret
.resume:
; We get here if we were only doing part of a lookup
; This relies on the fact that .success returns bx == si
xchg edx, eax ; Directory length in edx
pop cx ; Old ISOFlags
pop di ; Next filename pointer
mov byte [di-1], '\' ; restore the backslash in the filename
mov [ISOFlags], cl ; Restore the flags
jz .failure ; Did we fail? If so fail for real!
jmp .look_for_slash ; Otherwise, next level
;
; allocate_file: Allocate a file structure
;
; If successful:
; ZF set
; BX = file pointer
; In unsuccessful:
; ZF clear
;
allocate_file:
push cx
mov bx, Files
mov cx, MAX_OPEN
.check:
cmp dword [bx], byte 0
je .found
add bx, open_file_t_size ; ZF = 0
loop .check
; ZF = 0 if we fell out of the loop
.found:
pop cx
ret
;
; iso_compare_names:
; Compare the names DS:SI and DS:DI and report if they are
; equal from an ISO 9660 perspective. SI is the name from
; the filesystem; CX indicates its length, and ';' terminates.
; DI is expected to end with a null.
;
; Note: clobbers AX, CX, SI, DI; assumes DS == ES == base segment
;
iso_compare_names:
; First, terminate and canonicalize input filename
push di
mov di, ISOFileName
.canon_loop:
jcxz .canon_end
lodsb
dec cx
cmp al, ';'
je .canon_end
and al, al
je .canon_end
stosb
cmp di, ISOFileNameEnd-1 ; Guard against buffer overrun
jb .canon_loop
.canon_end:
cmp di, ISOFileName
jbe .canon_done
cmp byte [di-1], '.' ; Remove terminal dots
jne .canon_done
dec di
jmp short .canon_end
.canon_done:
mov [di], byte 0 ; Null-terminate string
pop di
mov si, ISOFileName
.compare:
lodsb
mov ah, [di]
inc di
and ax, ax
jz .success ; End of string for both
and al, al ; Is either one end of string?
jz .failure ; If so, failure
and ah, ah
jz .failure
or ax, 2020h ; Convert to lower case
cmp al, ah
je .compare
.failure:
and ax, ax ; ZF = 0 (at least one will be nonzero)
.success:
ret
;
; getfssec: Get multiple clusters from a file, given the file pointer.
;
; On entry:
; ES:BX -> Buffer
; SI -> File pointer
; CX -> Cluster count; 0FFFFh = until end of file
; On exit:
; SI -> File pointer (or 0 on EOF)
; CF = 1 -> Hit EOF
;
getfssec:
cmp cx, [si+file_left]
jna .ok_size
mov cx, [si+file_left]
.ok_size:
mov bp, cx
push cx
push si
mov eax, [si+file_sector]
call getlinsec
xor ecx, ecx
pop si
pop cx
add [si+file_sector], ecx
sub [si+file_left], ecx
ja .not_eof ; CF = 0
xor ecx, ecx
mov [si+file_sector], ecx ; Mark as unused
xor si,si
stc
.not_eof:
ret
; INT 13h, AX=4B01h, DL=<passed in value> failed.
; Try to scan the entire 80h-FFh from the end.
spec_query_failed:
mov si,spec_err_msg
call writemsg
mov dl, 0FFh
.test_loop:
pusha
mov ax, 4B01h
mov si, spec_packet
mov byte [si], 13 ; Size of buffer
int 13h
popa
jc .still_broken
mov si, maybe_msg
call writemsg
mov al, dl
call writehex2
call crlf
cmp byte [sp_drive], dl
jne .maybe_broken
; Okay, good enough...
mov si, alright_msg
call writemsg
mov [DriveNo], dl
.found_drive:
jmp found_drive
; Award BIOS 4.51 apparently passes garbage in sp_drive,
; but if this was the drive number originally passed in
; DL then consider it "good enough"
.maybe_broken:
cmp byte [DriveNo], dl
je .found_drive
.still_broken:
dec dx
cmp dl, 80h
jnb .test_loop
fatal_error:
mov si, nothing_msg
call writemsg
.norge:
jmp short .norge
; Information message (DS:SI) output
; Prefix with "isolinux: "
;
writemsg:
push ax
push si
mov si, isolinux_str
call writestr
pop si
call writestr
pop ax
ret
;
; crlf: Print a newline
;
crlf:
mov si, crlf_msg
; Fall through
;
; writestr: write a null-terminated string to the console, saving
; registers on entry.
;
writestr:
pushfd
pushad
.top:
lodsb
and al, al
jz .end
call writechr
jmp short .top
.end:
popad
popfd
ret
;
; writehex[248]: Write a hex number in (AL, AX, EAX) to the console
;
writehex2:
pushfd
pushad
shl eax, 24
mov cx, 2
jmp short writehex_common
writehex4:
pushfd
pushad
shl eax, 16
mov cx, 4
jmp short writehex_common
writehex8:
pushfd
pushad
mov cx, 8
writehex_common:
.loop:
rol eax, 4
push eax
and al, 0Fh
cmp al, 10
jae .high
.low:
add al, '0'
jmp short .ischar
.high:
add al, 'A'-10
.ischar:
call writechr
pop eax
loop .loop
popad
popfd
ret
;
; Write a character to the screen. There is a more "sophisticated"
; version of this in the subsequent code, so we patch the pointer
; when appropriate.
;
writechr:
pushfd
pushad
mov ah, 0Eh
xor bx, bx
int 10h
popad
popfd
ret
;
; Get one sector. Convenience entry point.
;
getonesec:
mov bp, 1
; Fall through to getlinsec
;
; Get linear sectors - EBIOS LBA addressing, 2048-byte sectors.
;
; Note that we can't always do this as a single request, because at least
; Phoenix BIOSes has a 127-sector limit. To be on the safe side, stick
; to 32 sectors (64K) per request.
;
; Input:
; EAX - Linear sector number
; ES:BX - Target buffer
; BP - Sector count
;
getlinsec:
mov si,dapa ; Load up the DAPA
mov [si+4],bx
mov bx,es
mov [si+6],bx
mov [si+8],eax
.loop2:
push bp ; Sectors left
cmp bp,[MaxTransfer]
jbe .bp_ok
mov bp,[MaxTransfer]
.bp_ok:
mov [si+2],bp
push si
mov dl,[DriveNo]
mov ah,42h ; Extended Read
call xint13
pop si
pop bp
movzx eax,word [si+2] ; Sectors we read
add [si+8],eax ; Advance sector pointer
sub bp,ax ; Sectors left
shl ax,SECTORSIZE_LG2-4 ; 2048-byte sectors -> segment
add [si+6],ax ; Advance buffer pointer
and bp,bp
jnz .loop2
mov eax,[si+8] ; Next sector
ret
; INT 13h with retry
xint13:
mov byte [RetryCount], retry_count
.try:
pushad
int 13h
jc .error
add sp, byte 8*4 ; Clean up stack
ret
.error:
mov [DiskError], ah ; Save error code
popad
dec byte [RetryCount]
jz .real_error
push ax
mov al,[RetryCount]
mov ah,[dapa+2] ; Sector transfer count
cmp al,2 ; Only 2 attempts left
ja .nodanger
mov ah,1 ; Drop transfer size to 1
jmp short .setsize
.nodanger:
cmp al,retry_count-2
ja .again ; First time, just try again
shr ah,1 ; Otherwise, try to reduce
adc ah,0 ; the max transfer size, but not to 0
.setsize:
mov [MaxTransfer],ah
mov [dapa+2],ah
.again:
pop ax
jmp .try
.real_error:
mov si, diskerr_msg
call writemsg
mov al, [DiskError]
call writehex2
mov si, ondrive_str
call writestr
mov al, dl
call writehex2
call crlf
; Fall through to kaboom
;
; kaboom: write a message and bail out. Wait for a user keypress,
; then do a hard reboot.
;
kaboom:
mov ax, cs
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
sti
mov si, err_bootfailed
call writestr
call getchar
cli
mov word [BIOS_magic], 0 ; Cold reboot
jmp 0F000h:0FFF0h ; Reset vector address
getchar:
.again:
mov ah, 1 ; Poll keyboard
int 16h
jz .again
.kbd:
xor ax, ax ; Get keyboard input
int 16h
.func_key:
ret
isolinux_banner db CR, LF, 'Loading IsoBoot...', CR, LF, 0
copyright_str db ' (C) 1994-2002 H. Peter Anvin', CR, LF, 0
presskey_msg db 'Press any key to boot from CD', 0
dot_msg db '.',0
%ifdef DEBUG_MESSAGES
startup_msg: db 'Starting up, DL = ', 0
spec_ok_msg: db 'Loaded spec packet OK, drive = ', 0
secsize_msg: db 'Sector size appears to be ', 0
rootloc_msg: db 'Root directory location: ', 0
rootlen_msg: db 'Root directory length: ', 0
rootsect_msg: db 'Root directory length(sectors): ', 0
fileloc_msg: db 'SETUPLDR.SYS location: ', 0
filelen_msg: db 'SETUPLDR.SYS length: ', 0
filesect_msg: db 'SETUPLDR.SYS length(sectors): ', 0
findfail_msg: db 'Failed to find file!', 0
startldr_msg: db 'Starting SETUPLDR.SYS', 0
%endif
; nosecsize_msg: db 'Failed to get sector size, assuming 0800', CR, LF, 0
spec_err_msg: db 'Loading spec packet failed, trying to wing it...', CR, LF, 0
maybe_msg: db 'Found something at drive = ', 0
alright_msg: db 'Looks like it might be right, continuing...', CR, LF, 0
nothing_msg: db 'Failed to locate CD-ROM device; boot failed.', CR, LF, 0
isolinux_str db 'IsoBoot: ', 0
crlf_msg db CR, LF, 0
diskerr_msg: db 'Disk error ', 0
ondrive_str: db ', drive ', 0
err_bootfailed db CR, LF, 'Boot failed: press a key to retry...'
isolinux_dir db '\LOADER', 0
no_dir_msg db 'Could not find the LOADER directory.', CR, LF, 0
isolinux_bin db 'SETUPLDR.SYS', 0
no_isolinux_msg db 'Could not find SETUPLDR.SYS.', CR, LF, 0
;
; El Torito spec packet
;
align 8, db 0
spec_packet: db 13h ; Size of packet
sp_media: db 0 ; Media type
sp_drive: db 0 ; Drive number
sp_controller: db 0 ; Controller index
sp_lba: dd 0 ; LBA for emulated disk image
sp_devspec: dw 0 ; IDE/SCSI information
sp_buffer: dw 0 ; User-provided buffer
sp_loadseg: dw 0 ; Load segment
sp_sectors: dw 0 ; Sector count
sp_chs: db 0,0,0 ; Simulated CHS geometry
sp_dummy: db 0 ; Scratch, safe to overwrite
;
; EBIOS drive parameter packet
;
align 8, db 0
drive_params: dw 30 ; Buffer size
dp_flags: dw 0 ; Information flags
dp_cyl: dd 0 ; Physical cylinders
dp_head: dd 0 ; Physical heads
dp_sec: dd 0 ; Physical sectors/track
dp_totalsec: dd 0,0 ; Total sectors
dp_secsize: dw 0 ; Bytes per sector
dp_dpte: dd 0 ; Device Parameter Table
dp_dpi_key: dw 0 ; 0BEDDh if rest valid
dp_dpi_len: db 0 ; DPI len
db 0
dw 0
dp_bus: times 4 db 0 ; Host bus type
dp_interface: times 8 db 0 ; Interface type
db_i_path: dd 0,0 ; Interface path
db_d_path: dd 0,0 ; Device path
db 0
db_dpi_csum: db 0 ; Checksum for DPI info
;
; EBIOS disk address packet
;
align 8, db 0
dapa: dw 16 ; Packet size
.count: dw 0 ; Block count
.off: dw 0 ; Offset of buffer
.seg: dw 0 ; Segment of buffer
.lba: dd 0 ; LBA (LSW)
dd 0 ; LBA (MSW)
alignb 4, db 0
MaxTransfer dw 2 ;32 ; Max sectors per transfer
times 2046-($-$$) db 0 ; Pad to file offset 2046
dw 0aa55h ; BootSector signature

5
reactos/boot/freeldr/bootsect/isombr.S
View file

@ -1,7 +1,8 @@
/*
* PROJECT: ReactOS MBR Boot Sector for ISO file system ("isohybrid mode")
* LICENSE: GNU GPLv2 or any later version as published by the Free Software Foundation
* COPYRIGHT: Copyright 2017 Colin Finck <colin@reactos.org>
* LICENSE: GPL-2.0+ (https://spdx.org/licenses/GPL-2.0+)
* PURPOSE: Providing an MBR Boot Sector that enables an ISO to be booted from a disk
* COPYRIGHT: Copyright 2017 Colin Finck (colin@reactos.org)
*/
#include <asm.inc>

466
reactos/boot/freeldr/bootsect/win2k.asm
View file

@ -1,466 +0,0 @@
;
; Win2k FAT32 Boot Sector
;
; Brian Palmer <brianp@sginet.com>
;
;
; The BP register is initialized to 0x7c00, the start of
; the boot sector. The SP register is initialized to
; 0x7bf4, leaving 12 bytes of data storage space above
; the stack.
;
; The DWORD that gets stored at 0x7bf4 is 0xffffffff ??
;
; The DWORD that gets stored at 0x7bf8 is the count of
; total sectors of the volume, calculated from the BPB.
;
; The DWORD that gets stored at 0x7bfc is the logical
; sector number of the start of the data area.
;
org 7c00h
segment .text
bits 16
start:
jmp short main
nop
OEMName db 'MSWIN4.0'
BytesPerSector dw 512
SectsPerCluster db 1
ReservedSectors dw 1
NumberOfFats db 2
MaxRootEntries dw 0 ;512 - Always zero for FAT32 volumes
TotalSectors dw 0 ;2880 - Always zero for FAT32 volumes
MediaDescriptor db 0f8h
SectorsPerFat dw 0 ;9 - Always zero for FAT32 volumes
SectorsPerTrack dw 18
NumberOfHeads dw 2
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 80h
Reserved db 0
ExtendSig db 29h
SerialNumber dd 00000000h
VolumeLabel db 'NO NAME '
FileSystem db 'FAT32 '
main:
00007C5A 33C9 xor cx,cx
00007C5C 8ED1 mov ss,cx ; Setup the stack
00007C5E BCF47B mov sp,0x7bf4 ; Give us 12 bytes of space above the stack
00007C61 8EC1 mov es,cx
00007C63 8ED9 mov ds,cx
00007C65 BD007C mov bp,0x7c00
00007C68 884E02 mov [bp+0x2],cl ; Zero out the nop instruction?? (3rd byte of the boot sector)
00007C6B 8A5640 mov dl,[bp+BootDrive]
00007C6E B408 mov ah,0x8
00007C70 CD13 int 0x13 ; Int 13, func 8 - Get Drive Parameters
00007C72 7305 jnc drive_param_ok ; If no error jmp
drive_param_error:
00007C74 B9FFFF mov cx,0xffff ; We couldn't determine the drive parameters
00007C77 8AF1 mov dh,cl ; So just set the CHS to 0xff
drive_param_ok:
00007C79 660FB6C6 movzx eax,dh ; Store the number of heads in eax
00007C7D 40 inc ax ; Make it one-based because the bios returns it zero-based
00007C7E 660FB6D1 movzx edx,cl ; Store the sectors per track in edx
00007C82 80E23F and dl,0x3f ; Mask off the cylinder bits
00007C85 F7E2 mul dx ; Multiply the sectors per track with the heads, result in dx:ax
00007C87 86CD xchg cl,ch ; Switch the cylinder with the sectors
00007C89 C0ED06 shr ch,0x6 ; Move the top two cylinder bits down where they should be
00007C8C 41 inc cx ; Make it one-based because the bios returns it zero-based
00007C8D 660FB7C9 movzx ecx,cx
00007C91 66F7E1 mul ecx ; Multiply the cylinders with (heads * sectors) [stored in dx:ax already]
00007C94 668946F8 mov [bp-0x8],eax ; This value is the number of total sectors on the disk, so save it for later
00007C98 837E1600 cmp word [bp+TotalSectors],byte +0x0 ; Check the old 16-bit value of TotalSectors
00007C9C 7538 jnz print_ntldr_error_message ; If it is non-zero then exit with an error
00007C9E 837E2A00 cmp word [bp+FSVersion],byte +0x0 ; Check the file system version word
00007CA2 7732 ja print_ntldr_error_message ; If it is not zero then exit with an error
;
; We are now ready to load our second sector of boot code
; But first, a bit of undocumented information about how
; Win2k stores it's second sector of boot code.
;
; The FAT32 filesystem was designed so that you can store
; multiple sectors of boot code. The boot sector of a FAT32
; volume is actually three sectors long. Microsoft extended
; the BPB so much that you can't fit enough code in the
; boot sector to make it work. So they extended it. Sector 0
; is the traditional boot sector, sector 1 is the FSInfo sector,
; and sector 2 is used to store extra boot code to make up
; for the lost space the BPB takes.
;
; Now this creates an interesting problem. Suppose for example
; that the user has Win98 and Win2k installed. The Win2k
; boot sector is stored at sector 0 and the Win98 boot sector is
; stored as BOOTSECT.DOS on the file system. Now if Win2k were
; to store it's second sector of boot code in sector 2 like
; the fat spec says to do then when you try to dual boot back
; to Win98 the Win98 boot sector will load Win2k's second
; sector of boot code. Understand? ;-)
;
; To get around this problem Win2k stores it's second sector
; of boot code elsewhere. This sector is always stored at sector 13
; on the file system. Now don't ask me what happens when you don't
; have enough reserved sectors to store it, but I've never seen a
; FAT32 volume that didn't have at least 32 reserved sectors.
;
00007CA4 668B461C mov eax,[bp+HiddenSectors] ; Get the count of hidden sectors
00007CA8 6683C00C add eax,byte +0xc ; Add 12 to that value so that we are loading the 13th sector of the volume
00007CAC BB0080 mov bx,0x8000 ; Read the sector to address 0x8000
00007CAF B90100 mov cx,0x1 ; Read just one sector
00007CB2 E82B00 call read_sectors ; Read it
00007CB5 E94803 jmp 0x8000 ; Jump to the next sector of boot code
print_disk_error_message:
00007CB8 A0FA7D mov al,[DISK_ERR_offset_from_0x7d00]
putchars:
00007CBB B47D mov ah,0x7d
00007CBD 8BF0 mov si,ax
get_another_char:
00007CBF AC lodsb
00007CC0 84C0 test al,al
00007CC2 7417 jz reboot
00007CC4 3CFF cmp al,0xff
00007CC6 7409 jz print_reboot_message
00007CC8 B40E mov ah,0xe
00007CCA BB0700 mov bx,0x7
00007CCD CD10 int 0x10
00007CCF EBEE jmp short get_another_char
print_reboot_message:
00007CD1 A0FB7D mov al,[RESTART_ERR_offset_from_0x7d00]
00007CD4 EBE5 jmp short putchars
print_ntldr_error_message:
00007CD6 A0F97D mov al,[NTLDR_ERR_offset_from_0x7d00]
00007CD9 EBE0 jmp short putchars
reboot:
00007CDB 98 cbw
00007CDC CD16 int 0x16
00007CDE CD19 int 0x19
read_sectors:
00007CE0 6660 pushad
00007CE2 663B46F8 cmp eax,[bp-0x8]
00007CE6 0F824A00 jc near 0x7d34
00007CEA 666A00 o32 push byte +0x0
00007CED 6650 push eax
00007CEF 06 push es
00007CF0 53 push bx
00007CF1 666810000100 push dword 0x10010
00007CF7 807E0200 cmp byte [bp+0x2],0x0
00007CFB 0F852000 jnz near 0x7d1f
00007CFF B441 mov ah,0x41
00007D01 BBAA55 mov bx,0x55aa
00007D04 8A5640 mov dl,[bp+BootDrive]
00007D07 CD13 int 0x13
00007D09 0F821C00 jc near 0x7d29
00007D0D 81FB55AA cmp bx,0xaa55
00007D11 0F851400 jnz near 0x7d29
00007D15 F6C101 test cl,0x1
00007D18 0F840D00 jz near 0x7d29
00007D1C FE4602 inc byte [bp+0x2]
00007D1F B442 mov ah,0x42
00007D21 8A5640 mov dl,[bp+BootDrive]
00007D24 8BF4 mov si,sp
00007D26 CD13 int 0x13
00007D28 B0F9 mov al,0xf9
00007D2A 6658 pop eax
00007D2C 6658 pop eax
00007D2E 6658 pop eax
00007D30 6658 pop eax
00007D32 EB2A jmp short 0x7d5e
00007D34 6633D2 xor edx,edx
00007D37 660FB74E18 movzx ecx,word [bp+SectorsPerTrack]
00007D3C 66F7F1 div ecx
00007D3F FEC2 inc dl
00007D41 8ACA mov cl,dl
00007D43 668BD0 mov edx,eax
00007D46 66C1EA10 shr edx,0x10
00007D4A F7761A div word [bp+NumberOfHeads]
00007D4D 86D6 xchg dl,dh
00007D4F 8A5640 mov dl,[bp+BootDrive]
00007D52 8AE8 mov ch,al
00007D54 C0E406 shl ah,0x6
00007D57 0ACC or cl,ah
00007D59 B80102 mov ax,0x201
00007D5C CD13 int 0x13
00007D5E 6661 popad
00007D60 0F8254FF jc near print_disk_error_message
00007D64 81C30002 add bx,0x200
00007D68 6640 inc eax
00007D6A 49 dec cx
00007D6B 0F8571FF jnz near read_sectors
00007D6F C3 ret
NTLDR db 'NTLDR '
filler times 49 db 0
NTLDR_ERR db 0dh,0ah,'NTLDR is missing',0ffh
DISK_ERR db 0dh,0ah,'Disk error',0ffh
RESTART_ERR db 0dh,0ah,'Press any key to restart',0dh,0ah
more_filler times 16 db 0
NTLDR_offset_from_0x7d00 db 0
NTLDR_ERR_offset_from_0x7d00 db 0ach
DISK_ERR_offset_from_0x7d00 db 0bfh
RESTART_ERR_offset_from_0x7d00 db 0cch
dw 0
dw 0aa55h
;
; And that ends the code that makes up the traditional boot sector
; From here on out is a disassembly of the extra sector of boot
; code required for a FAT32 volume. Win2k stores this code at
; sector 13 on the file system.
;
00008000 660FB64610 movzx eax,byte [bp+NumberOfFats] ; Put the number of fats into eax
00008005 668B4E24 mov ecx,[bp+SectorsPerFatBig] ; Put the count of sectors per fat into ecx
00008009 66F7E1 mul ecx ; Multiply them, edx:eax = (eax * ecx)
0000800C 6603461C add eax,[bp+HiddenSectors] ; Add the hidden sectors to eax
00008010 660FB7560E movzx edx,word [bp+ReservedSectors] ; Put the count of reserved sectors into edx
00008015 6603C2 add eax,edx ; Add it to eax
00008018 668946FC mov [bp-0x4],eax ; eax now contains the start of the data area, so save it for later
0000801C 66C746F4FFFFFFFF mov dword [bp-0xc],0xffffffff ; Save 0xffffffff for later??
00008024 668B462C mov eax,[bp+RootDirStartCluster] ; Put the starting cluster of the root directory into eax
00008028 6683F802 cmp eax,byte +0x2 ; Check and see if the root directory starts at cluster 2 or above
0000802C 0F82A6FC jc near print_ntldr_error_message ; If not exit with error
00008030 663DF8FFFF0F cmp eax,0xffffff8 ; Check and see if the root directory start cluster is and end of cluster chain indicator
00008036 0F839CFC jnc near print_ntldr_error_message ; If so exit with error
search_root_directory_cluster:
0000803A 6650 push eax ; Save root directory start cluster on stack
0000803C 6683E802 sub eax,byte +0x2 ; Adjust it because the first two fat entries are unused so the third entry marks the first data area cluster
00008040 660FB65E0D movzx ebx,byte [bp+SectsPerCluster] ; Put the number of sectors per cluster in ebx
00008045 8BF3 mov si,bx ; Now store it also in si register
00008047 66F7E3 mul ebx ; Multiply sectors per cluster with root directory start cluster
0000804A 660346FC add eax,[bp-0x4] ; Add the start sector of the data area
read_directory_sector:
0000804E BB0082 mov bx,0x8200 ; We now have the start sector of the root directory, so load it to 0x8200
00008051 8BFB mov di,bx ; Put the address of the root directory sector in di also
00008053 B90100 mov cx,0x1 ; Read one sector
00008056 E887FC call read_sectors ; Perform the read
check_entry_for_ntldr:
00008059 382D cmp [di],ch ; Check the first byte of the root directory entry for zero
0000805B 741E jz ntldr_not_found ; If so then NTLDR is missing so exit with error
0000805D B10B mov cl,0xb ; Put the value 11 in cl so we can compare an 11-byte filename
0000805F 56 push si ; Save si (which contains the number of sectors per cluster)
00008060 BE707D mov si,NTLDR ;0x7d70 ; Check and see if "NTLDR" is the first file entry
00008063 F3A6 repe cmpsb ; Do the compare
00008065 5E pop si ; Restore sectors per cluster into si
00008066 741B jz ntldr_found ; If we found it then continue, else check next entry
00008068 03F9 add di,cx ; Add 0 to di? the next entry is 0x15 bytes away
0000806A 83C715 add di,byte +0x15 ; Add 0x15 to di
0000806D 3BFB cmp di,bx ; Check to see if we have reached the end of our sector we loaded, read_sectors sets bx = end address of data loaded
0000806F 72E8 jc check_entry_for_ntldr ; If we haven't reached the end then check the next entry
00008071 4E dec si ; decrement si, si holds the number of sectors per cluster
00008072 75DA jnz read_directory_sector ; If it's not zero then search the next sector for NTLDR
00008074 6658 pop eax ; If we got here that means we didn't find NTLDR in the previous root directory cluster, so restore eax with the start cluster
00008076 E86500 call get_fat_entry ; Get the next cluster in the fat chain
00008079 72BF jc search_root_directory_cluster ; If we reached end-of-file marker then don't jump, otherwise continue search
ntldr_not_found:
0000807B 83C404 add sp,byte +0x4
0000807E E955FC jmp print_ntldr_error_message
ntldr_load_segment_address dw 0x2000
ntldr_found:
00008083 83C404 add sp,byte +0x4 ; Adjust stack to remove root directory start cluster
00008086 8B7509 mov si,[di+0x9] ; Put start cluster high word in si
00008089 8B7D0F mov di,[di+0xf] ; Put start cluster low word in di
0000808C 8BC6 mov ax,si ; Put high word in ax
0000808E 66C1E010 shl eax,0x10 ; Shift it into position
00008092 8BC7 mov ax,di ; Put low word in ax, now eax contains start cluster of NTLDR
00008094 6683F802 cmp eax,byte +0x2 ; Check and see if the start cluster of NTLDR starts at cluster 2 or above
00008098 0F823AFC jc near print_ntldr_error_message ; If not exit with error
0000809C 663DF8FFFF0F cmp eax,0xffffff8 ; Check and see if the start cluster of NTLDR is and end of cluster chain indicator
000080A2 0F8330FC jnc near print_ntldr_error_message ; If so exit with error
load_next_ntldr_cluster:
000080A6 6650 push eax ; Save NTLDR start cluster for later
000080A8 6683E802 sub eax,byte +0x2 ; Adjust it because the first two fat entries are unused so the third entry marks the first data area cluster
000080AC 660FB64E0D movzx ecx,byte [bp+SectsPerCluster] ; Put the sectors per cluster into ecx
000080B1 66F7E1 mul ecx ; Multiply sectors per cluster by the start cluster, we now have the logical start sector
000080B4 660346FC add eax,[bp-0x4] ; Add the start of the data area logical sector
000080B8 BB0000 mov bx,0x0 ; Load NTLDR to offset zero
000080BB 06 push es ; Save es
000080BC 8E068180 mov es,[ntldr_load_segment_address] ; Get the segment address to load NTLDR to
000080C0 E81DFC call read_sectors ; Load the first cluster
000080C3 07 pop es ; Restore es
000080C4 6658 pop eax ; Restore eax to NTLDR start cluster
000080C6 C1EB04 shr bx,0x4 ; bx contains the amount of data we transferred, so divide it by 16
000080C9 011E8180 add [ntldr_load_segment_address],bx ; Add that value to the segment
000080CD E80E00 call get_fat_entry ; Get the next cluster in eax
000080D0 0F830200 jnc near jump_to_ntldr ; If we have reached the end of file then lets get to NTLDR
000080D4 72D0 jc load_next_ntldr_cluster ; If not, then load another cluster
jump_to_ntldr:
000080D6 8A5640 mov dl,[bp+BootDrive] ; Put the boot drive in dl
000080D9 EA00000020 jmp 0x2000:0x0 ; Jump to NTLDR
get_fat_entry:
000080DE 66C1E002 shl eax,0x2 ; Multiply cluster by 4
000080E2 E81100 call load_fat_sector ; Load the fat sector
000080E5 26668B01 mov eax,[es:bx+di] ; Get the fat entry
000080E9 6625FFFFFF0F and eax,0xfffffff ; Mask off the most significant 4 bits
000080EF 663DF8FFFF0F cmp eax,0xffffff8 ; Compare it to end of file marker to set the flags correctly
000080F5 C3 ret ; Return to caller
load_fat_sector:
000080F6 BF007E mov di,0x7e00 ; We will load the fat sector to 0x7e00
000080F9 660FB74E0B movzx ecx,word [bp+SectsPerCluster] ; Get the sectors per cluster
000080FE 6633D2 xor edx,edx ; We will divide (cluster * 4) / sectorspercluster
00008101 66F7F1 div ecx ; eax is already set before we get to this routine
00008104 663B46F4 cmp eax,[bp-0xc] ; Compare eax to 0xffffffff (initially, we set this value later)
00008108 743A jz load_fat_sector_end ; If it is the same return
0000810A 668946F4 mov [bp-0xc],eax ; Update that value
0000810E 6603461C add eax,[bp+HiddenSectors] ; Add the hidden sectors
00008112 660FB74E0E movzx ecx,word [bp+ReservedSectors] ; Add the reserved sectors
00008117 6603C1 add eax,ecx ; To the hidden sectors + the value we computed earlier
0000811A 660FB75E28 movzx ebx,word [bp+ExtendedFlags] ; Get extended flags and put into ebx
0000811F 83E30F and bx,byte +0xf ; Mask off upper 8 bits
00008122 7416 jz load_fat_sector_into_memory ; If fat is mirrored then skip fat calcs
00008124 3A5E10 cmp bl,[bp+NumberOfFats] ; Compare bl to number of fats
00008127 0F83ABFB jnc near print_ntldr_error_message ; If bl is bigger than numfats exit with error
0000812B 52 push dx ; Save dx
0000812C 668BC8 mov ecx,eax ; Put the current fat sector offset into ecx
0000812F 668B4624 mov eax,[bp+SectorsPerFatBig] ; Get the number of sectors occupied by one fat
00008133 66F7E3 mul ebx ; Multiplied by the active fat index
00008136 6603C1 add eax,ecx ; Add the current fat sector offset
00008139 5A pop dx ; Restore dx
load_fat_sector_into_memory:
0000813A 52 push dx ; Save dx, what is so important in dx??
0000813B 8BDF mov bx,di ; Put 0x7e00 in bx
0000813D B90100 mov cx,0x1 ; Load one sector
00008140 E89DFB call read_sectors ; Perform the read
00008143 5A pop dx ; Restore dx
load_fat_sector_end:
00008144 8BDA mov bx,dx ; Put it into bx, what is this value??
00008146 C3 ret ; Return
00008147 0000 add [bx+si],al
00008149 0000 add [bx+si],al
0000814B 0000 add [bx+si],al
0000814D 0000 add [bx+si],al
0000814F 0000 add [bx+si],al
00008151 0000 add [bx+si],al
00008153 0000 add [bx+si],al
00008155 0000 add [bx+si],al
00008157 0000 add [bx+si],al
00008159 0000 add [bx+si],al
0000815B 0000 add [bx+si],al
0000815D 0000 add [bx+si],al
0000815F 0000 add [bx+si],al
00008161 0000 add [bx+si],al
00008163 0000 add [bx+si],al
00008165 0000 add [bx+si],al
00008167 0000 add [bx+si],al
00008169 0000 add [bx+si],al
0000816B 0000 add [bx+si],al
0000816D 0000 add [bx+si],al
0000816F 0000 add [bx+si],al
00008171 0000 add [bx+si],al
00008173 0000 add [bx+si],al
00008175 0000 add [bx+si],al
00008177 0000 add [bx+si],al
00008179 0000 add [bx+si],al
0000817B 0000 add [bx+si],al
0000817D 0000 add [bx+si],al
0000817F 0000 add [bx+si],al
00008181 0000 add [bx+si],al
00008183 0000 add [bx+si],al
00008185 0000 add [bx+si],al
00008187 0000 add [bx+si],al
00008189 0000 add [bx+si],al
0000818B 0000 add [bx+si],al
0000818D 0000 add [bx+si],al
0000818F 0000 add [bx+si],al
00008191 0000 add [bx+si],al
00008193 0000 add [bx+si],al
00008195 0000 add [bx+si],al
00008197 0000 add [bx+si],al
00008199 0000 add [bx+si],al
0000819B 0000 add [bx+si],al
0000819D 0000 add [bx+si],al
0000819F 0000 add [bx+si],al
000081A1 0000 add [bx+si],al
000081A3 0000 add [bx+si],al
000081A5 0000 add [bx+si],al
000081A7 0000 add [bx+si],al
000081A9 0000 add [bx+si],al
000081AB 0000 add [bx+si],al
000081AD 0000 add [bx+si],al
000081AF 0000 add [bx+si],al
000081B1 0000 add [bx+si],al
000081B3 0000 add [bx+si],al
000081B5 0000 add [bx+si],al
000081B7 0000 add [bx+si],al
000081B9 0000 add [bx+si],al
000081BB 0000 add [bx+si],al
000081BD 0000 add [bx+si],al
000081BF 0000 add [bx+si],al
000081C1 0000 add [bx+si],al
000081C3 0000 add [bx+si],al
000081C5 0000 add [bx+si],al
000081C7 0000 add [bx+si],al
000081C9 0000 add [bx+si],al
000081CB 0000 add [bx+si],al
000081CD 0000 add [bx+si],al
000081CF 0000 add [bx+si],al
000081D1 0000 add [bx+si],al
000081D3 0000 add [bx+si],al
000081D5 0000 add [bx+si],al
000081D7 0000 add [bx+si],al
000081D9 0000 add [bx+si],al
000081DB 0000 add [bx+si],al
000081DD 0000 add [bx+si],al
000081DF 0000 add [bx+si],al
000081E1 0000 add [bx+si],al
000081E3 0000 add [bx+si],al
000081E5 0000 add [bx+si],al
000081E7 0000 add [bx+si],al
000081E9 0000 add [bx+si],al
000081EB 0000 add [bx+si],al
000081ED 0000 add [bx+si],al
000081EF 0000 add [bx+si],al
000081F1 0000 add [bx+si],al
000081F3 0000 add [bx+si],al
000081F5 0000 add [bx+si],al
000081F7 0000 add [bx+si],al
000081F9 0000 add [bx+si],al
000081FB 0000 add [bx+si],al
000081FD 0055AA add [di-0x56],dl ; We can't forget the infamous boot signature

249
reactos/boot/freeldr/bootsect/wxpfat16.asm
View file

@ -1,249 +0,0 @@
;
; The BP register is initialized to 0x7c00, the start of
; the boot sector. The SP register is initialized to
; 0x7bf0, leaving 16 bytes of data storage space above
; the stack.
;
; The DWORD that gets stored at 0x7bfc is the logical
; sector number of the start of the data area.
;
; The DWORD that gets stored at 0x7bf8 is ????????
;
; The DWORD that gets stored at 0x7bf4 is ????????
;
; The DWORD that gets stored at 0x7bf0 is ????????
;
org 7c00h
segment .text
bits 16
start:
jmp short main
nop
OEMName db 'MSWIN4.0'
BytesPerSector dw 512
SectsPerCluster db 1
ReservedSectors dw 1
NumberOfFats db 2
MaxRootEntries dw 0 ;512 - Always zero for FAT32 volumes
TotalSectors dw 0 ;2880 - Always zero for FAT32 volumes
MediaDescriptor db 0f8h
SectorsPerFat dw 0 ;9 - Always zero for FAT32 volumes
SectorsPerTrack dw 18
NumberOfHeads dw 2
HiddenSectors dd 0
TotalSectorsBig dd 0
BootDrive db 80h
Reserved db 0
ExtendSig db 29h
SerialNumber dd 00000000h
VolumeLabel db 'NO NAME '
FileSystem db 'FAT16 '
main:
00007C3E 33C9 xor cx,cx
00007C40 8ED1 mov ss,cx ; Setup stack
00007C42 BCF07B mov sp,0x7bf0 ; Give us 16 bytes (4 dwords) of space above stack
00007C45 8ED9 mov ds,cx
00007C47 B80020 mov ax,0x2000
00007C4A 8EC0 mov es,ax ; Setup ES:0000 == 2000:0000
00007C4C FC cld
00007C4D BD007C mov bp,0x7c00
00007C50 384E24 cmp [bp+BootDrive],cl ; Compare the boot drive to zero (I think they are testing for a hard disk drive number)
00007C53 7D24 jnl floppy_boot ; Nope, it's a floppy, skip partition table tests
00007C55 8BC1 mov ax,cx ; Move zero to AX
00007C57 99 cwd ; DX:AX now contains zero
00007C58 E83C01 call read_one_sector ; Try to read in the MBR sector
00007C5B 721C jc floppy_boot ; Read failed, continue
00007C5D 83EB3A sub bx,byte +0x3a ; BX comes back with 512, make it equal to 454 (offset of partition table in MBR)
00007C60 66A11C7C mov eax,[HiddenSectors] ; Put HiddenSectors in EAX
find_our_partition:
00007C64 26663B07 cmp eax,[es:bx] ; Compare partition table entry's start sector to HiddenSectors
00007C68 268A57FC mov dl,[es:bx-0x4] ; Get partition type byte for this entry
00007C6C 7506 jnz next_partition_entry ; If partition start sector != HiddenSectors then skip this entry
00007C6E 80CA02 or dl,0x2 ; Set the second bit in partition type?? I guess this makes types 4 & 6 identical
00007C71 885602 mov [bp+0x2],dl ; Save it on top of nop instruction (3rd byte of boot sector)
next_partition_entry:
00007C74 80C310 add bl,0x10 ; Add 16 to bl (offset of next entry in partition table)
00007C77 73EB jnc find_our_partition ; Jump back until we hit the end of the partition table
; We now have our partition type at 0000:7C02
; If the type was 4 or 6 then that byte is 6
; I can't imagine why the boot sector needs to store
; this information, but hopefully I will uncover it
; as I further disassemble this boot sector.
floppy_boot:
00007C79 33C9 xor cx,cx ; Zero out CX
00007C7B 8A4610 mov al,[bp+NumberOfFats] ; Get the number of FATs in AL (usually 2)
00007C7E 98 cbw ; Sign extend it into AX (AX == 2)
00007C7F F76616 mul word [bp+NumberOfFats] ; Multiply it with NumberOfFats PLUS the low byte of MaxRootEntries!!??
00007C82 03461C add ax,[bp+HiddenSectors] ; Result is in DX:AX
00007C85 13561E adc dx,[bp+HiddenSectors+2] ; Add HiddenSectors to DX:AX
00007C88 03460E add ax,[bp+ReservedSectors] ; Add ReservedSectors to DX:AX
00007C8B 13D1 adc dx,cx ; CX still contains zero
00007C8D 8B7611 mov si,[bp+MaxRootEntries] ; Get MaxRootEntries in SI
00007C90 60 pusha ; Save all registers (right now DX:AX has starting sector of root dir)
00007C91 8946FC mov [bp-0x4],ax ; Save the starting sector of the root directory
00007C94 8956FE mov [bp-0x2],dx ; Save it in the first 4 bytes before the boot sector
00007C97 B82000 mov ax,0x20 ; AX == 32 (size of a directory entry)
00007C9A F7E6 mul si ; Multiply it with MaxRootEntries (DX:AX == length in bytes of root directory)
00007C9C 8B5E0B mov bx,[bp+BytesPerSector] ; Get the BytesPerSector in BX
00007C9F 03C3 add ax,bx ; Add it to AX (what if this addition carries? MS should 'adc dx,0' shouldn't they?)
00007CA1 48 dec ax ; Subtract one (basically rounding up)
00007CA2 F7F3 div bx ; Divide DX:AX (length of root dir in bytes) by the size of a sector
00007CA4 0146FC add [bp-0x4],ax ; Add the number of sectors of the root directory to our other value
00007CA7 114EFE adc [bp-0x2],cx ; Now the first 4 bytes before the boot sector contain the starting sector of the data area
00007CAA 61 popa ; Restore all registers (DX:AX has start sector of root dir)
load_root_dir_sector:
00007CAB BF0000 mov di,0x0 ; Zero out di
00007CAE E8E600 call read_one_sector ; Read the first sector of the root directory
00007CB1 7239 jc print_disk_error_message ; Read failed, print disk error and reboot
search_directory:
00007CB3 26382D cmp [es:di],ch ; If the first byte of the directory entry is zero then we have reached the end
00007CB6 7417 jz print_ntldr_error_message; of the directory and NTLDR is not here so reboot
00007CB8 60 pusha ; Save all registers
00007CB9 B10B mov cl,0xb ; Put 11 in cl (length of filename in directory entry)
00007CBB BEA17D mov si,NTLDR ; Put offset of filename string in DS:SI
00007CBE F3A6 repe cmpsb ; Compare this directory entry against 'NTLDR '
00007CC0 61 popa ; Restore all the registers
00007CC1 7432 jz found_ntldr ; If we found NTLDR then jump
00007CC3 4E dec si ; SI holds MaxRootEntries, subtract one
00007CC4 7409 jz print_ntldr_error_message; If we are out of root dir entries then reboot
00007CC6 83C720 add di,byte +0x20 ; Increment DI by the size of a directory entry
00007CC9 3BFB cmp di,bx ; Compare DI to BX (DI has offset to next dir entry, BX has address of end of directory sector in memory)
00007CCB 72E6 jc search_directory ; If DI is less than BX loop again
00007CCD EBDC jmp short load_root_dir_sector ; Didn't find NTLDR in this directory sector, try again
print_ntldr_error_message:
00007CCF A0FB7D mov al,[NTLDR_ERR_offset_from_0x7d00]
putchars:
00007CD2 B47D mov ah,0x7d
00007CD4 8BF0 mov si,ax
get_another_char:
00007CD6 AC lodsb
00007CD7 98 cbw
00007CD8 40 inc ax
00007CD9 740C jz print_reboot_message
00007CDB 48 dec ax
00007CDC 7413 jz reboot
00007CDE B40E mov ah,0xe
00007CE0 BB0700 mov bx,0x7
00007CE3 CD10 int 0x10
00007CE5 EBEF jmp short get_another_char
print_reboot_message:
00007CE7 A0FD7D mov al,[RESTART_ERR_offset_from_0x7d00]
00007CEA EBE6 jmp short putchars
print_disk_error_message:
00007CEC A0FC7D mov al,[DISK_ERR_offset_from_0x7d00]
00007CEF EBE1 jmp short putchars
reboot:
00007CF1 CD16 int 0x16
00007CF3 CD19 int 0x19
found_ntldr:
00007CF5 268B551A mov dx,[es:di+0x1a] ; Get NTLDR start cluster in DX
00007CF9 52 push dx ; Save it on the stack
00007CFA B001 mov al,0x1 ; Read 1 cluster? Or is this one sector?
00007CFC BB0000 mov bx,0x0 ; ES:BX is the load address (2000:0000)
00007CFF E83B00 call read_cluster ; Do the read
00007D02 72E8 jc print_disk_error_message ; If it failed then reboot
00007D04 5B pop bx ; Get the start cluster of NTLDR in BX
00007D05 8A5624 mov dl,[bp+BootDrive] ; Get boot drive in DL
00007D08 BE0B7C mov si,0x7c0b
00007D0B 8BFC mov di,sp
00007D0D C746F03D7D mov word [bp-0x10],read_cluster
00007D12 C746F4297D mov word [bp-0xc],0x7d29
00007D17 8CD9 mov cx,ds
00007D19 894EF2 mov [bp-0xe],cx
00007D1C 894EF6 mov [bp-0xa],cx
00007D1F C606967DCB mov byte [0x7d96],0xcb
00007D24 EA03000020 jmp 0x2000:0x3
00007D29 0FB6C8 movzx cx,al
00007D2C 668B46F8 mov eax,[bp-0x8]
00007D30 6603461C add eax,[bp+HiddenSectors]
00007D34 668BD0 mov edx,eax
00007D37 66C1EA10 shr edx,0x10
00007D3B EB5E jmp short 0x7d9b
read_cluster:
00007D3D 0FB6C8 movzx cx,al
00007D40 4A dec dx
00007D41 4A dec dx
00007D42 8A460D mov al,[bp+SectsPerCluster]
00007D45 32E4 xor ah,ah
00007D47 F7E2 mul dx
00007D49 0346FC add ax,[bp-0x4]
00007D4C 1356FE adc dx,[bp-0x2]
00007D4F EB4A jmp short 0x7d9b
read_sectors:
00007D51 52 push dx
00007D52 50 push ax
00007D53 06 push es
00007D54 53 push bx
00007D55 6A01 push byte +0x1
00007D57 6A10 push byte +0x10
00007D59 91 xchg ax,cx
00007D5A 8B4618 mov ax,[bp+SectorsPerTrack]
00007D5D 96 xchg ax,si
00007D5E 92 xchg ax,dx
00007D5F 33D2 xor dx,dx
00007D61 F7F6 div si
00007D63 91 xchg ax,cx
00007D64 F7F6 div si
00007D66 42 inc dx
00007D67 87CA xchg cx,dx
00007D69 F7761A div word [bp+NumberOfHeads]
00007D6C 8AF2 mov dh,dl
00007D6E 8AE8 mov ch,al
00007D70 C0CC02 ror ah,0x2
00007D73 0ACC or cl,ah
00007D75 B80102 mov ax,0x201
00007D78 807E020E cmp byte [bp+0x2],0xe
00007D7C 7504 jnz 0x7d82
00007D7E B442 mov ah,0x42
00007D80 8BF4 mov si,sp
00007D82 8A5624 mov dl,[bp+BootDrive]
00007D85 CD13 int 0x13
00007D87 61 popa
00007D88 61 popa
00007D89 720B jc 0x7d96
00007D8B 40 inc ax
00007D8C 7501 jnz 0x7d8f
00007D8E 42 inc dx
00007D8F 035E0B add bx,[bp+BytesPerSector]
00007D92 49 dec cx
00007D93 7506 jnz 0x7d9b
00007D95 F8 clc
00007D96 C3 ret
read_one_sector:
00007D97 41 inc cx
00007D98 BB0000 mov bx,0x0
00007D9B 60 pusha
00007D9C 666A00 o32 push byte +0x0
00007D9F EBB0 jmp short 0x7d51
NTLDR db 'NTLDR '
NTLDR_ERR db 0dh,0ah,'NTLDR is missing',0ffh
DISK_ERR db 0dh,0ah,'Disk error',0ffh
RESTART_ERR db 0dh,0ah,'Press any key to restart',0dh,0ah
filler times 18 db 0
NTLDR_offset_from_0x7d00 db 0
NTLDR_ERR_offset_from_0x7d00 db 0ach
DISK_ERR_offset_from_0x7d00 db 0bfh
RESTART_ERR_offset_from_0x7d00 db 0cch
dw 0
dw 0aa55h