forked from xt-sys/exectos
Add VBR stub
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@@ -3,3 +3,4 @@ PROJECT(BOOTSECT)
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# Compile boot sectors
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compile_bootsector(mbrboot ${BOOTSECT_SOURCE_DIR}/mbrboot.S 0x7C00 Start)
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compile_bootsector(espboot ${BOOTSECT_SOURCE_DIR}/espboot.S 0x7C00 Start)
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113
boot/bootsect/espboot.S
Normal file
113
boot/bootsect/espboot.S
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@@ -0,0 +1,113 @@
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/**
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* PROJECT: ExectOS
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* COPYRIGHT: See COPYING.md in the top level directory
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* FILE: boot/bootsect/espboot.S
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* DESCRIPTION: XT Boot Loader ESP boot code (FAT32)
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* DEVELOPERS: Aiken Harris <harraiken91@gmail.com>
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*/
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.text
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.code16
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.global Start
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Start:
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/* Jump to the real start to omit the BPB (BIOS Parameter Block) */
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jmp RealStart
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nop
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/* BIOS Parameter Block */
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OsName:
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.ascii "XTOS "
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OsVersion:
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.ascii "1.0"
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BytesPerSector:
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.word 512
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SectorsPerCluster:
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.byte 2
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ReservedSectors:
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.word 8
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FatCopies:
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.byte 1
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RootDirEntries:
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.word 1024
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TotalSectors:
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.word 0
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MediaType:
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.byte 0xF8
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SectorsPerFat:
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.word 0
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SectorsPerTrack:
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.word 17
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NumberOfHeads:
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.word 0
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HiddenSectors:
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.long 0
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TotalBigSectors:
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.long 0x200000
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BigSectorsPerFat:
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.long 0x1FE0
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ExtendedFlags:
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.word 0
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FsVersion:
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.word 0
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RootDirStartCluster:
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.long 0
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FSInfoSector:
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.word 0
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BackupBootSector:
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.word 6
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Reserved:
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.fill 12, 1, 0
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DriveNumber:
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.byte 0x80
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CurrentHead:
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.byte 0
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Signature:
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.byte 0x29
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SerialNumber:
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.long 0
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VolumeLabel:
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.ascii "NO NAME "
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FileSystem:
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.ascii "FAT32 "
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RealStart:
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/* Set segments and stack */
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cli
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cld
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xorw %ax, %ax
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movw %ax, %ds
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movw %ax, %es
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movw %ax, %ss
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movw $0x7C00, %bp
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leaw -16(%bp), %sp
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sti
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/* Print message */
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movw $msgUnavailable, %si
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call Print
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/* Wait for key press and reboot */
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xorw %ax, %ax
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int $0x16
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int $0x19
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Print:
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/* Simple routine to print messages */
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lodsb
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orb %al, %al
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jz DonePrint
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movb $0x0E, %ah
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movw $0x07, %bx
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int $0x10
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jmp Print
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DonePrint:
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retw
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msgUnavailable:
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.ascii "XTLDR requires EFI-based system!\r\nPress any key to restart\r\n"
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/* Fill the rest of the VBR with zeros and add VBR signature at the end */
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.fill (510 - (. - Start)), 1, 0
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.word 0xAA55
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