mirror of
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[EXT2]
Convert comments to preprocessor format svn path=/trunk/; revision=53928
This commit is contained in:
Timo Kreuzer
parent
a4bc1ebf2b
commit
58e525b4b8
1 changed files with 326 additions and 326 deletions
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@ -1,11 +1,11 @@
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; EXT2.ASM
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; EXT2 Boot Sector
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; Copyright (c) 2002, 2003 Brian Palmer
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// EXT2.ASM
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// EXT2 Boot Sector
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// Copyright (c) 2002, 2003 Brian Palmer
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; [bp-0x04] Here we will store the number of sectors per track
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; [bp-0x08] Here we will store the number of heads
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; [bp-0x0c] Here we will store the size of the disk as the BIOS reports in CHS form
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; [bp-0x10] Here we will store the number of LBA sectors read
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// [bp-0x04] Here we will store the number of sectors per track
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// [bp-0x08] Here we will store the number of heads
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// [bp-0x0c] Here we will store the size of the disk as the BIOS reports in CHS form
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// [bp-0x10] Here we will store the number of LBA sectors read
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SECTORS_PER_TRACK equ 0x04
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NUMBER_OF_HEADS equ 0x08
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@ -29,20 +29,20 @@ start:
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nop
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BootDrive db 0x80
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;BootPartition db 0 ; Moved to end of boot sector to have a standard format across all boot sectors
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;SectorsPerTrack db 63 ; Moved to [bp-SECTORS_PER_TRACK]
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;NumberOfHeads dw 16 ; Moved to [bp-NUMBER_OF_HEADS]
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;BiosCHSDriveSize dd (1024 * 1024 * 63) ; Moved to [bp-BIOS_CHS_DRIVE_SIZE]
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;LBASectorsRead dd 0 ; Moved to [bp-LBA_SECTORS_READ]
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//BootPartition db 0 // Moved to end of boot sector to have a standard format across all boot sectors
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//SectorsPerTrack db 63 // Moved to [bp-SECTORS_PER_TRACK]
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//NumberOfHeads dw 16 // Moved to [bp-NUMBER_OF_HEADS]
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//BiosCHSDriveSize dd (1024 * 1024 * 63) // Moved to [bp-BIOS_CHS_DRIVE_SIZE]
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//LBASectorsRead dd 0 // Moved to [bp-LBA_SECTORS_READ]
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Ext2VolumeStartSector dd 263088 ; Start sector of the ext2 volume
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Ext2BlockSize dd 2 ; Block size in sectors
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Ext2BlockSizeInBytes dd 1024 ; Block size in bytes
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Ext2PointersPerBlock dd 256 ; Number of block pointers that can be contained in one block
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Ext2GroupDescPerBlock dd 32 ; Number of group descriptors per block
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Ext2FirstDataBlock dd 1 ; First data block (1 for 1024-byte blocks, 0 for bigger sizes)
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Ext2InodesPerGroup dd 2048 ; Number of inodes per group
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Ext2InodesPerBlock dd 8 ; Number of inodes per block
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Ext2VolumeStartSector dd 263088 // Start sector of the ext2 volume
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Ext2BlockSize dd 2 // Block size in sectors
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Ext2BlockSizeInBytes dd 1024 // Block size in bytes
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Ext2PointersPerBlock dd 256 // Number of block pointers that can be contained in one block
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Ext2GroupDescPerBlock dd 32 // Number of group descriptors per block
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Ext2FirstDataBlock dd 1 // First data block (1 for 1024-byte blocks, 0 for bigger sizes)
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Ext2InodesPerGroup dd 2048 // Number of inodes per group
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Ext2InodesPerBlock dd 8 // Number of inodes per block
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Ext2ReadEntireFileLoadSegment:
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dw 0
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@ -54,83 +54,83 @@ Ext2BlocksLeftToRead:
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dd 0
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main:
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xor ax,ax ; Setup segment registers
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mov ds,ax ; Make DS correct
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mov es,ax ; Make ES correct
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mov ss,ax ; Make SS correct
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xor ax,ax // Setup segment registers
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mov ds,ax // Make DS correct
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mov es,ax // Make ES correct
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mov ss,ax // Make SS correct
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mov bp,7c00h
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mov sp,7b00h ; Setup a stack
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mov sp,7b00h // Setup a stack
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cmp BYTE [BYTE bp+BootDrive],BYTE 0xff ; If they have specified a boot drive then use it
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cmp BYTE [BYTE bp+BootDrive],BYTE 0xff // If they have specified a boot drive then use it
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jne GetDriveParameters
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mov [BYTE bp+BootDrive],dl ; Save the boot drive
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mov [BYTE bp+BootDrive],dl // Save the boot drive
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GetDriveParameters:
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mov ah,08h
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mov dl,[BYTE bp+BootDrive] ; Get boot drive in dl
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int 13h ; Request drive parameters from the bios
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jnc CalcDriveSize ; If the call succeeded then calculate the drive size
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mov dl,[BYTE bp+BootDrive] // Get boot drive in dl
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int 13h // Request drive parameters from the bios
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jnc CalcDriveSize // If the call succeeded then calculate the drive size
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; If we get here then the call to the BIOS failed
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; so just set CHS equal to the maximum addressable
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; size
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// If we get here then the call to the BIOS failed
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// so just set CHS equal to the maximum addressable
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// size
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mov cx,0ffffh
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mov dh,cl
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CalcDriveSize:
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; Now that we have the drive geometry
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; lets calculate the drive size
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mov bl,ch ; Put the low 8-bits of the cylinder count into BL
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mov bh,cl ; Put the high 2-bits in BH
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shr bh,6 ; Shift them into position, now BX contains the cylinder count
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and cl,3fh ; Mask off cylinder bits from sector count
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; CL now contains sectors per track and DH contains head count
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movzx eax,dh ; Move the heads into EAX
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movzx ebx,bx ; Move the cylinders into EBX
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movzx ecx,cl ; Move the sectors per track into ECX
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inc eax ; Make it one based because the bios returns it zero based
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mov [BYTE bp-NUMBER_OF_HEADS],eax ; Save number of heads
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mov [BYTE bp-SECTORS_PER_TRACK],ecx ; Save number of sectors per track
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inc ebx ; Make the cylinder count one based also
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mul ecx ; Multiply heads with the sectors per track, result in edx:eax
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mul ebx ; Multiply the cylinders with (heads * sectors) [stored in edx:eax already]
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// Now that we have the drive geometry
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// lets calculate the drive size
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mov bl,ch // Put the low 8-bits of the cylinder count into BL
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mov bh,cl // Put the high 2-bits in BH
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shr bh,6 // Shift them into position, now BX contains the cylinder count
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and cl,3fh // Mask off cylinder bits from sector count
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// CL now contains sectors per track and DH contains head count
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movzx eax,dh // Move the heads into EAX
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movzx ebx,bx // Move the cylinders into EBX
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movzx ecx,cl // Move the sectors per track into ECX
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inc eax // Make it one based because the bios returns it zero based
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mov [BYTE bp-NUMBER_OF_HEADS],eax // Save number of heads
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mov [BYTE bp-SECTORS_PER_TRACK],ecx // Save number of sectors per track
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inc ebx // Make the cylinder count one based also
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mul ecx // Multiply heads with the sectors per track, result in edx:eax
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mul ebx // Multiply the cylinders with (heads * sectors) [stored in edx:eax already]
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; We now have the total number of sectors as reported
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; by the bios in eax, so store it in our variable
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// We now have the total number of sectors as reported
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// by the bios in eax, so store it in our variable
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mov [BYTE bp-BIOS_CHS_DRIVE_SIZE],eax
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LoadExtraBootCode:
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; First we have to load our extra boot code at
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; sector 1 into memory at [0000:7e00h]
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;mov eax,01h
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// First we have to load our extra boot code at
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// sector 1 into memory at [0000:7e00h]
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//mov eax,01h
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xor eax,eax
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inc eax ; Read logical sector 1, EAX now = 1
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mov cx,1 ; Read one sector
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mov bx,7e00h ; Read sector to [0000:7e00h]
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inc eax // Read logical sector 1, EAX now = 1
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mov cx,1 // Read one sector
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mov bx,7e00h // Read sector to [0000:7e00h]
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call ReadSectors
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jmp LoadRootDirectory
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; Reads ext2 group descriptor into [7000:8000]
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; We read it to this arbitrary location so
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; it will not cross a 64k boundary
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; EAX has group descriptor number to read
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// Reads ext2 group descriptor into [7000:8000]
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// We read it to this arbitrary location so
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// it will not cross a 64k boundary
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// EAX has group descriptor number to read
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Ext2ReadGroupDesc:
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shl eax,5 ; Group = (Group * sizeof(GROUP_DESCRIPTOR) /* 32 */)
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shl eax,5 // Group = (Group * sizeof(GROUP_DESCRIPTOR) /* 32 */)
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xor edx,edx
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div DWORD [BYTE bp+Ext2GroupDescPerBlock] ; Group = (Group / Ext2GroupDescPerBlock)
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add eax,DWORD [BYTE bp+Ext2FirstDataBlock] ; Group = Group + Ext2FirstDataBlock + 1
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inc eax ; EAX now has the group descriptor block number
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; EDX now has the group descriptor offset in the block
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div DWORD [BYTE bp+Ext2GroupDescPerBlock] // Group = (Group / Ext2GroupDescPerBlock)
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add eax,DWORD [BYTE bp+Ext2FirstDataBlock] // Group = Group + Ext2FirstDataBlock + 1
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inc eax // EAX now has the group descriptor block number
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// EDX now has the group descriptor offset in the block
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; Adjust the read offset so that the
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; group descriptor is read to 7000:8000
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// Adjust the read offset so that the
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// group descriptor is read to 7000:8000
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mov ebx,78000h
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sub ebx,edx
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shr ebx,4
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@ -138,51 +138,51 @@ Ext2ReadGroupDesc:
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xor bx,bx
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; Everything is now setup to call Ext2ReadBlock
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; Instead of using the call instruction we will
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; just put Ext2ReadBlock right after this routine
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// Everything is now setup to call Ext2ReadBlock
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// Instead of using the call instruction we will
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// just put Ext2ReadBlock right after this routine
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; Reads ext2 block into [ES:BX]
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; EAX has logical block number to read
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// Reads ext2 block into [ES:BX]
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// EAX has logical block number to read
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Ext2ReadBlock:
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mov ecx,DWORD [BYTE bp+Ext2BlockSize]
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mul ecx
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jmp ReadSectors
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; Reads ext2 inode into [6000:8000]
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; We read it to this arbitrary location so
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; it will not cross a 64k boundary
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; EAX has inode number to read
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// Reads ext2 inode into [6000:8000]
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// We read it to this arbitrary location so
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// it will not cross a 64k boundary
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// EAX has inode number to read
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Ext2ReadInode:
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dec eax ; Inode = Inode - 1
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dec eax // Inode = Inode - 1
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xor edx,edx
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div DWORD [BYTE bp+Ext2InodesPerGroup] ; Inode = (Inode / Ext2InodesPerGroup)
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mov ebx,eax ; EBX now has the inode group number
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div DWORD [BYTE bp+Ext2InodesPerGroup] // Inode = (Inode / Ext2InodesPerGroup)
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mov ebx,eax // EBX now has the inode group number
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mov eax,edx
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xor edx,edx
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div DWORD [BYTE bp+Ext2InodesPerBlock] ; Inode = (Inode / Ext2InodesPerBlock)
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shl edx,7 ; FIXME: InodeOffset *= 128 (make the array index a byte offset)
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; EAX now has the inode offset block number from inode table
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; EDX now has the inode offset in the block
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div DWORD [BYTE bp+Ext2InodesPerBlock] // Inode = (Inode / Ext2InodesPerBlock)
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shl edx,7 // FIXME: InodeOffset *= 128 (make the array index a byte offset)
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// EAX now has the inode offset block number from inode table
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// EDX now has the inode offset in the block
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; Save the inode values and put the group
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; descriptor number in EAX and read it in
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// Save the inode values and put the group
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// descriptor number in EAX and read it in
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push edx
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push eax
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mov eax,ebx
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call Ext2ReadGroupDesc
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; Group descriptor has been read, now
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; grab the inode table block number from it
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// Group descriptor has been read, now
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// grab the inode table block number from it
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push WORD 7000h
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pop es
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mov di,8008h
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pop eax ; Restore inode offset block number from stack
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add eax,DWORD [es:di] ; Add the inode table start block
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pop eax // Restore inode offset block number from stack
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add eax,DWORD [es:di] // Add the inode table start block
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; Adjust the read offset so that the
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; inode we want is read to 6000:8000
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pop edx ; Restore inode offset in the block from stack
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// Adjust the read offset so that the
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// inode we want is read to 6000:8000
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pop edx // Restore inode offset in the block from stack
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mov ebx,68000h
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sub ebx,edx
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shr ebx,4
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@ -193,131 +193,131 @@ Ext2ReadInode:
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ret
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; Reads logical sectors into [ES:BX]
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; EAX has logical sector number to read
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; CX has number of sectors to read
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// Reads logical sectors into [ES:BX]
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// EAX has logical sector number to read
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// CX has number of sectors to read
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ReadSectors:
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add eax,DWORD [BYTE bp+Ext2VolumeStartSector] ; Add the start of the volume
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cmp eax,DWORD [BYTE bp-BIOS_CHS_DRIVE_SIZE] ; Check if they are reading a sector outside CHS range
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jae ReadSectorsLBA ; Yes - go to the LBA routine
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; If at all possible we want to use LBA routines because
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; They are optimized to read more than 1 sector per read
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add eax,DWORD [BYTE bp+Ext2VolumeStartSector] // Add the start of the volume
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cmp eax,DWORD [BYTE bp-BIOS_CHS_DRIVE_SIZE] // Check if they are reading a sector outside CHS range
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jae ReadSectorsLBA // Yes - go to the LBA routine
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// If at all possible we want to use LBA routines because
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// They are optimized to read more than 1 sector per read
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pushad ; Save logical sector number & sector count
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pushad // Save logical sector number & sector count
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CheckInt13hExtensions: ; Now check if this computer supports extended reads
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mov ah,0x41 ; AH = 41h
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mov bx,0x55aa ; BX = 55AAh
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mov dl,[BYTE bp+BootDrive] ; DL = drive (80h-FFh)
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int 13h ; IBM/MS INT 13 Extensions - INSTALLATION CHECK
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jc ReadSectorsCHS ; CF set on error (extensions not supported)
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cmp bx,0xaa55 ; BX = AA55h if installed
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CheckInt13hExtensions: // Now check if this computer supports extended reads
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mov ah,0x41 // AH = 41h
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mov bx,0x55aa // BX = 55AAh
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mov dl,[BYTE bp+BootDrive] // DL = drive (80h-FFh)
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int 13h // IBM/MS INT 13 Extensions - INSTALLATION CHECK
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jc ReadSectorsCHS // CF set on error (extensions not supported)
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cmp bx,0xaa55 // BX = AA55h if installed
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jne ReadSectorsCHS
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test cl,1 ; CX = API subset support bitmap
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jz ReadSectorsCHS ; Bit 0, extended disk access functions (AH=42h-44h,47h,48h) supported
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test cl,1 // CX = API subset support bitmap
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jz ReadSectorsCHS // Bit 0, extended disk access functions (AH=42h-44h,47h,48h) supported
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popad ; Restore sector count & logical sector number
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popad // Restore sector count & logical sector number
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ReadSectorsLBA:
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pushad ; Save logical sector number & sector count
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pushad // Save logical sector number & sector count
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cmp cx,byte 64 ; Since the LBA calls only support 0x7F sectors at a time we will limit ourselves to 64
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jbe ReadSectorsSetupDiskAddressPacket ; If we are reading less than 65 sectors then just do the read
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mov cx,64 ; Otherwise read only 64 sectors on this loop iteration
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cmp cx,byte 64 // Since the LBA calls only support 0x7F sectors at a time we will limit ourselves to 64
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jbe ReadSectorsSetupDiskAddressPacket // If we are reading less than 65 sectors then just do the read
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mov cx,64 // Otherwise read only 64 sectors on this loop iteration
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ReadSectorsSetupDiskAddressPacket:
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mov [BYTE bp-LBA_SECTORS_READ],cx
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mov WORD [BYTE bp-LBA_SECTORS_READ+2],0
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o32 push byte 0
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push eax ; Put 64-bit logical block address on stack
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push es ; Put transfer segment on stack
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push bx ; Put transfer offset on stack
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push cx ; Set transfer count
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push byte 0x10 ; Set size of packet to 10h
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mov si,sp ; Setup disk address packet on stack
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push eax // Put 64-bit logical block address on stack
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push es // Put transfer segment on stack
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push bx // Put transfer offset on stack
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push cx // Set transfer count
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push byte 0x10 // Set size of packet to 10h
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mov si,sp // Setup disk address packet on stack
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mov dl,[BYTE bp+BootDrive] ; Drive number
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mov ah,42h ; Int 13h, AH = 42h - Extended Read
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int 13h ; Call BIOS
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jc PrintDiskError ; If the read failed then abort
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mov dl,[BYTE bp+BootDrive] // Drive number
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mov ah,42h // Int 13h, AH = 42h - Extended Read
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int 13h // Call BIOS
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jc PrintDiskError // If the read failed then abort
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add sp,byte 0x10 ; Remove disk address packet from stack
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add sp,byte 0x10 // Remove disk address packet from stack
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popad ; Restore sector count & logical sector number
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popad // Restore sector count & logical sector number
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push bx
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mov ebx,DWORD [BYTE bp-LBA_SECTORS_READ]
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add eax,ebx ; Increment sector to read
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add eax,ebx // Increment sector to read
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shl ebx,5
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mov dx,es
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add dx,bx ; Setup read buffer for next sector
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add dx,bx // Setup read buffer for next sector
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mov es,dx
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pop bx
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sub cx,[BYTE bp-LBA_SECTORS_READ]
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jnz ReadSectorsLBA ; Read next sector
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jnz ReadSectorsLBA // Read next sector
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ret
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; Reads logical sectors into [ES:BX]
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; EAX has logical sector number to read
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; CX has number of sectors to read
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// Reads logical sectors into [ES:BX]
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// EAX has logical sector number to read
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// CX has number of sectors to read
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ReadSectorsCHS:
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popad ; Get logical sector number & sector count off stack
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popad // Get logical sector number & sector count off stack
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ReadSectorsCHSLoop:
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pushad
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xor edx,edx
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mov ecx,DWORD [BYTE bp-SECTORS_PER_TRACK]
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div ecx ; Divide logical by SectorsPerTrack
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inc dl ; Sectors numbering starts at 1 not 0
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mov cl,dl ; Sector in CL
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div ecx // Divide logical by SectorsPerTrack
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inc dl // Sectors numbering starts at 1 not 0
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mov cl,dl // Sector in CL
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mov edx,eax
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shr edx,16
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div WORD [BYTE bp-NUMBER_OF_HEADS] ; Divide logical by number of heads
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mov dh,dl ; Head in DH
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mov dl,[BYTE bp+BootDrive] ; Drive number in DL
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mov ch,al ; Cylinder in CX
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ror ah,2 ; Low 8 bits of cylinder in CH, high 2 bits
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; in CL shifted to bits 6 & 7
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or cl,ah ; Or with sector number
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div WORD [BYTE bp-NUMBER_OF_HEADS] // Divide logical by number of heads
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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
|
||||
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
|
||||
jc PrintDiskError // If the read failed then abort
|
||||
|
||||
popad
|
||||
|
||||
inc eax ; Increment Sector to Read
|
||||
inc eax // Increment Sector to Read
|
||||
|
||||
mov dx,es
|
||||
add dx,byte 20h ; Increment read buffer for next sector
|
||||
add dx,byte 20h // Increment read buffer for next sector
|
||||
mov es,dx
|
||||
|
||||
loop ReadSectorsCHSLoop ; Read next sector
|
||||
loop ReadSectorsCHSLoop // Read next sector
|
||||
|
||||
ret
|
||||
ret
|
||||
|
||||
|
||||
|
||||
|
||||
; Displays a disk error message
|
||||
; And reboots
|
||||
// Displays a disk error message
|
||||
// And reboots
|
||||
PrintDiskError:
|
||||
mov si,msgDiskError ; Bad boot disk message
|
||||
call PutChars ; Display it
|
||||
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
|
||||
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
|
||||
|
|
@ -340,318 +340,318 @@ Done:
|
|||
|
||||
|
||||
msgDiskError db 'Disk error',0
|
||||
; Sorry, need the space...
|
||||
;msgAnyKey db 'Press any key to restart',0
|
||||
// Sorry, need the space...
|
||||
//msgAnyKey db 'Press any key to restart',0
|
||||
msgAnyKey db 'Press any key',0
|
||||
|
||||
times 509-($-$$) db 0 ; Pad to 509 bytes
|
||||
times 509-($-$$) db 0 // Pad to 509 bytes
|
||||
|
||||
BootPartition db 0
|
||||
|
||||
dw 0aa55h ; BootSector signature
|
||||
|
||||
dw 0aa55h // BootSector signature
|
||||
|
||||
; End of bootsector
|
||||
;
|
||||
; Now starts the extra boot code that we will store
|
||||
; at sector 1 on a EXT2 volume
|
||||
|
||||
// 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
|
||||
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
|
||||
// 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
|
||||
push es // Save these for later
|
||||
|
||||
; Get root directory size from inode structure
|
||||
// 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
|
||||
// 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
|
||||
// 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
|
||||
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
|
||||
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
|
||||
// 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
|
||||
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
|
||||
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
|
||||
rep cmpsb // Compare the file names
|
||||
pop di
|
||||
pop eax
|
||||
pop edx
|
||||
jz FoundFile
|
||||
|
||||
; Nope, didn't find it in this entry, keep looking
|
||||
// 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
|
||||
// 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
|
||||
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
|
||||
// Point ES:DI to the inode structure at 6000:8000
|
||||
pop es
|
||||
pop di ; These were saved earlier
|
||||
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
|
||||
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
|
||||
mov si,msgLoading // "Loading FreeLoader..." message
|
||||
call PutChars // Display it
|
||||
|
||||
call Ext2ReadEntireFile ; Read freeldr.sys to 0000:8000
|
||||
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
|
||||
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.
|
||||
// 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
|
||||
// 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
|
||||
// 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
|
||||
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
|
||||
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
|
||||
// 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
|
||||
// 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
|
||||
// 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
|
||||
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
|
||||
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
|
||||
// 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
|
||||
// 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
|
||||
// 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
|
||||
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
|
||||
// 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
|
||||
// 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
|
||||
// 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
|
||||
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)
|
||||
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
|
||||
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
|
||||
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
|
||||
// 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
|
||||
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
|
||||
// Check to see if we actually have
|
||||
// blocks left to read
|
||||
cmp eax,byte 0
|
||||
jnz Ext2ReadIndirectBlock
|
||||
|
||||
Ext2ReadEntireFileDone:
|
||||
ret
|
||||
|
||||
; Reads a maximum number of blocks
|
||||
; from an array at 7000:0000
|
||||
; and updates the total count
|
||||
; ECX contains the max number of blocks to read
|
||||
; EAX contains the number of blocks left to read
|
||||
; On return:
|
||||
; EAX contians the new number of blocks left to read
|
||||
// Reads a maximum number of blocks
|
||||
// from an array at 7000:0000
|
||||
// and updates the total count
|
||||
// ECX contains the max number of blocks to read
|
||||
// EAX contains the number of blocks left to read
|
||||
// On return:
|
||||
// EAX contians the new number of blocks left to read
|
||||
Ext2ReadDirectBlockList:
|
||||
cmp eax,ecx ; Compare it to the maximum number of blocks to read
|
||||
ja CallExt2ReadDirectBlocks ; If it will take more blocks then just read all of the blocks
|
||||
mov cx,ax ; Otherwise adjust the block count accordingly
|
||||
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
|
||||
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
|
||||
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
|
||||
// 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
|
||||
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
|
||||
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
|
||||
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
|
||||
xor bx,bx // Setup load address for next read
|
||||
|
||||
call Ext2ReadBlock ; Read the block (this updates ES for the next read)
|
||||
call Ext2ReadBlock // Read the block (this updates ES for the next read)
|
||||
|
||||
mov [BYTE bp+Ext2ReadEntireFileLoadSegment],es ; Save updated ES
|
||||
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
|
||||
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.
|
||||
// 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
|
||||
// Displays a file not found error message
|
||||
// And reboots
|
||||
PrintFileNotFound:
|
||||
mov si,msgFreeLdr ; FreeLdr not found message
|
||||
mov si,msgFreeLdr // FreeLdr not found message
|
||||
jmp short DisplayItAndReboot
|
||||
|
||||
; Displays a file size is 0 error
|
||||
; And reboots
|
||||
// Displays a file size is 0 error
|
||||
// And reboots
|
||||
PrintFileSizeError:
|
||||
mov si,msgFileSize ; Error message
|
||||
mov si,msgFileSize // Error message
|
||||
jmp short DisplayItAndReboot
|
||||
|
||||
; Displays a file is not a regular file error
|
||||
; And reboots
|
||||
// Displays a file is not a regular file error
|
||||
// And reboots
|
||||
PrintRegFileError:
|
||||
mov si,msgRegFile ; Error message
|
||||
mov si,msgRegFile // Error message
|
||||
DisplayItAndReboot:
|
||||
call PutChars ; Display it
|
||||
call PutChars // Display it
|
||||
jmp Reboot
|
||||
|
||||
msgFreeLdr db 'freeldr.sys not found',0
|
||||
|
|
@ -660,6 +660,6 @@ msgRegFile db 'freeldr.sys isnt a regular file',0
|
|||
filename db 'freeldr.sys'
|
||||
msgLoading db 'Loading FreeLoader...',0
|
||||
|
||||
times 1022-($-$$) db 0 ; Pad to 1022 bytes
|
||||
times 1022-($-$$) db 0 // Pad to 1022 bytes
|
||||
|
||||
dw 0aa55h ; BootSector signature
|
||||
dw 0aa55h // BootSector signature
|
||||
|
|
|
|||
Loading…
Reference in a new issue