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! The master boot sector will have setup a stack,
! this is normally at 0:7c00 down.
! DS, SS, CS and ES will all have value 0 so the execution address is 0:7c00
! On entry the register SI will be pointer to the partition entry that
! this sector was loaded from, DL is the drive.
! Also if it's a standard Master boot DH will be the head, CX will be the
! sector and cylinder, BX=7C00, AX=1, DI=7DFE, BP=SI. There's a reasonable
! chance that this isn't true though.
! The Master boot itself will have been loaded and run at $07c00
! The BIOS must have setup a stack because interrupts are enabled
! Little else can be assumed because DOS doesn`t assume anything either
sysboot_start:
j codestart
nop ! DOS appears to _require_ this to identify an MSDOS disk!!
.blkb sysboot_start+3-*
public dosfs_stat
dos_sysid: .ascii "LINUX" ! System ID
.byte 0,0,0
dosfs_stat:
dos_sect: .blkw 1 ! Sector size
dos_clust: .blkb 1 ! Cluster size
dos_resv: .blkw 1 ! Res-sector
dos_nfat: .blkb 1 ! FAT count
dos_nroot: .blkw 1 ! Root dir entries
dos_maxsect: .blkw 1 ! Sector count (=0 if large FS)
dos_media: .blkb 1 ! Media code
dos_fatlen: .blkw 1 ! FAT length
dos_spt: .blkw 1 ! Sect/Track
dos_heads: .blkw 1 ! Heads
dos_hidden: .blkw 2 ! Hidden sectors
! Here down is DOS 4+ and probably not needed for floppy boots.
dos4_maxsect: .blkw 2 ! Large FS sector count
dos4_phy_drive: .blkb 1 ! Phys drive
.blkb 1 ! Reserved
.blkb 1 ! DOS 4
floppy_temp:
dos4_serial: .blkw 2 ! Serial number
dos4_label: .blkb 11 ! Disk Label (DOS 4+)
dos4_fattype: .blkb 8 ! FAT type
!
! This is where the code will be overlaid, the default is a hang
! The 0x5A offset clears the FAT32 header.
.blkb sysboot_start+0x5A-*
public codestart
codestart:
j codestart
! Partition table
public bootblock_magic
.blkb sysboot_start+0x1BE-*
partition_1:
.blkb 8 ! IN,SH,SS,ST,OS,EH,ES,ET
.blkw 2 ! Linear position (0 based)
.blkw 2 ! Linear length
.blkb sysboot_start+0x1CE-*
partition_2:
.blkb 8 ! IN,SH,SS,ST,OS,EH,ES,ET
.blkw 2 ! Linear position (0 based)
.blkw 2 ! Linear length
.blkb sysboot_start+0x1DE-*
partition_3:
.blkb 8 ! IN,SH,SS,ST,OS,EH,ES,ET
.blkw 2 ! Linear position (0 based)
.blkw 2 ! Linear length
.blkb sysboot_start+0x1EE-*
partition_4:
.blkb 8 ! IN,SH,SS,ST,OS,EH,ES,ET
.blkw 2 ! Linear position (0 based)
.blkw 2 ! Linear length
.blkb sysboot_start+0x1FE-*
bootblock_magic:
.word 0xAA55
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