[ros-diffs] [tkreuzer] 52197: [BOOTSECTOR] Convert fat bootsector to new syntax
tkreuzer at svn.reactos.org
tkreuzer at svn.reactos.org
Sun Jun 12 15:57:38 UTC 2011
Author: tkreuzer
Date: Sun Jun 12 15:57:36 2011
New Revision: 52197
URL: http://svn.reactos.org/svn/reactos?rev=52197&view=rev
Log:
[BOOTSECTOR]
Convert fat bootsector to new syntax
Added:
trunk/reactos/boot/freeldr/bootsect/fat.S (with props)
Modified:
trunk/reactos/boot/freeldr/bootsect/CMakeLists.txt
Modified: trunk/reactos/boot/freeldr/bootsect/CMakeLists.txt
URL: http://svn.reactos.org/svn/reactos/trunk/reactos/boot/freeldr/bootsect/CMakeLists.txt?rev=52197&r1=52196&r2=52197&view=diff
==============================================================================
--- trunk/reactos/boot/freeldr/bootsect/CMakeLists.txt [iso-8859-1] (original)
+++ trunk/reactos/boot/freeldr/bootsect/CMakeLists.txt [iso-8859-1] Sun Jun 12 15:57:36 2011
@@ -4,13 +4,12 @@
CreateBootSectorTarget2(dosmbr ${CMAKE_CURRENT_SOURCE_DIR}/dosmbr.S ${CMAKE_CURRENT_BINARY_DIR}/dosmbr.bin 7c00)
#CreateBootSectorTarget2(ext2 ${CMAKE_CURRENT_SOURCE_DIR}/ext2.S ${CMAKE_CURRENT_BINARY_DIR}/ext2.bin 0)
CreateBootSectorTarget2(fat32 ${CMAKE_CURRENT_SOURCE_DIR}/fat32.S ${CMAKE_CURRENT_BINARY_DIR}/fat32.bin 7c00)
-#CreateBootSectorTarget2(fat ${CMAKE_CURRENT_SOURCE_DIR}/fat.S ${CMAKE_CURRENT_BINARY_DIR}/fat.bin 0)
+CreateBootSectorTarget2(fat ${CMAKE_CURRENT_SOURCE_DIR}/fat.S ${CMAKE_CURRENT_BINARY_DIR}/fat.bin 7c00)
CreateBootSectorTarget2(isoboot ${CMAKE_CURRENT_SOURCE_DIR}/isoboot.S ${CMAKE_CURRENT_BINARY_DIR}/isoboot.bin 7000)
CreateBootSectorTarget2(isobtrt ${CMAKE_CURRENT_SOURCE_DIR}/isobtrt.S ${CMAKE_CURRENT_BINARY_DIR}/isobtrt.bin 7000)
if(NOT MSVC)
CreateBootSectorTarget(ext2 ${CMAKE_CURRENT_SOURCE_DIR}/ext2.asm ${CMAKE_CURRENT_BINARY_DIR}/ext2.bin 0)
-CreateBootSectorTarget(fat ${CMAKE_CURRENT_SOURCE_DIR}/fat.asm ${CMAKE_CURRENT_BINARY_DIR}/fat.bin 0)
endif()
add_cd_file(TARGET dosmbr DESTINATION loader NO_CAB FILE ${CMAKE_CURRENT_BINARY_DIR}/dosmbr.bin FOR all)
Added: trunk/reactos/boot/freeldr/bootsect/fat.S
URL: http://svn.reactos.org/svn/reactos/trunk/reactos/boot/freeldr/bootsect/fat.S?rev=52197&view=auto
==============================================================================
--- trunk/reactos/boot/freeldr/bootsect/fat.S (added)
+++ trunk/reactos/boot/freeldr/bootsect/fat.S [iso-8859-1] Sun Jun 12 15:57:36 2011
@@ -1,0 +1,433 @@
+// 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 0000:8000
+// 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.
+
+#include <asm.inc>
+
+#define BP_REL(x) [bp+x-offset start]
+
+DataAreaStartHigh = 2
+DataAreaStartLow = 4
+BiosCHSDriveSizeHigh = 6
+BiosCHSDriveSizeLow = 8
+BiosCHSDriveSize = 8
+ReadSectorsOffset = 10
+ReadClusterOffset = 12
+PutCharsOffset = 14
+BootSectorStackTop = HEX(7c00) - 16
+
+
+// org 7c00h
+
+.code16
+
+start:
+ jmp main
+ nop
+
+OEMName:
+ .ascii "FrLdr1.0"
+BytesPerSector:
+ .word 512
+SectsPerCluster:
+ .byte 1
+ReservedSectors:
+ .word 1
+NumberOfFats:
+ .byte 2
+MaxRootEntries:
+ .word 224
+TotalSectors:
+ .word 2880
+MediaDescriptor:
+ .byte HEX(0f0)
+SectorsPerFat:
+ .word 9
+SectorsPerTrack:
+ .word 18
+NumberOfHeads:
+ .word 2
+HiddenSectors:
+ .long 0
+TotalSectorsBig:
+ .long 0
+BootDrive:
+ .byte HEX(0ff)
+Reserved:
+ .byte 0
+ExtendSig:
+ .byte HEX(29)
+SerialNumber:
+ .long 00000000
+VolumeLabel:
+ .ascii "NO NAME "
+FileSystem:
+ .ascii "FAT12 "
+
+main:
+ xor ax, ax
+ mov ss, ax
+ mov bp, HEX(7c00)
+ mov sp, BootSectorStackTop // Setup a stack
+ mov ds, ax // Make DS correct
+ mov es, ax // Make ES correct
+
+ cmp byte ptr BP_REL(BootDrive), HEX(0ff) // If they have specified a boot drive then use it
+ jne GetDriveParameters
+
+ mov byte ptr BP_REL(BootDrive), dl // Save the boot drive
+
+
+GetDriveParameters:
+ mov ah, 8
+ mov dl, byte ptr BP_REL(BootDrive) // Get boot drive in dl
+ int HEX(13) // 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, HEX(0ffff)
+ 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, HEX(3f) // 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 dword ptr [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 ptr BP_REL(NumberOfFats) // Number of fats
+ mul word ptr BP_REL(SectorsPerFat) // Times sectors per fat
+ add ax, word ptr BP_REL(HiddenSectors)
+ adc dx, word ptr BP_REL(HiddenSectors+2) // Add the number of hidden sectors
+ add ax, word ptr BP_REL(ReservedSectors) // Add the number of reserved sectors
+ adc dx, cx // Add carry bit
+ mov word ptr [bp - DataAreaStartLow], ax // Save the starting sector of the root directory
+ mov word ptr [bp - DataAreaStartHigh], dx // Save it in the first 4 bytes before the boot sector
+ mov si, word ptr BP_REL(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, 32 // Size of dir entry
+ mul si // Times the number of entries
+ mov bx, word ptr BP_REL(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 word ptr [bp - DataAreaStartLow], ax // Add the number of sectors of the root directory to our other value
+ adc word ptr [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, HEX(7e0) // 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 byte ptr 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, 11 // Put 11 in cl (length of filename in directory entry)
+ mov si, offset 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, 32 // Increment DI by the size of a directory entry
+ cmp di, HEX(0200) // 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 0000:8000
+ // ES:DI has dir entry (ES:DI == 07E0:XXXX)
+ mov ax, word ptr es:[di + HEX(1a)] // Get start cluster
+ push ax // Save start cluster
+ push HEX(800) // Put 800h on the stack and load it
+ pop es // Into ES so that we load the cluster at 0000:8000
+ 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 ptr [bp-ReadSectorsOffset], offset ReadSectors // Save the address of ReadSectors
+ mov word ptr [bp-ReadClusterOffset], offset ReadCluster // Save the address of ReadCluster
+ mov word ptr [bp-PutCharsOffset], offset 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 0000:8000. 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.
+ //jmp 0000:9003h
+ push 0 // push segment (0x0000)
+ mov bx, [HEX(8000) + HEX(0A8)] // load the RVA of the EntryPoint into eax
+ add bx, HEX(8003) // RVA -> VA and skip 3 bytes (jump to fathelper code)
+ push bx // push offset
+ retf // Transfer control to FreeLoader
+
+
+
+
+// Displays an error message
+// And reboots
+ErrBoot:
+ mov si, offset msgFreeLdr // FreeLdr not found message
+ call PutChars // Display it
+
+Reboot:
+// mov si, offset msgAnyKey // Press any key message
+// call PutChars // Display it
+ xor ax, ax
+ int HEX(16) // Wait for a keypress
+ int HEX(19) // Reboot
+
+PutChars:
+ lodsb
+ or al,al
+ jz short Done
+ mov ah, HEX(0e)
+ mov bx, 7
+ int HEX(10)
+ jmp short PutChars
+Done:
+ ret
+
+// Displays a bad boot message
+// And reboots
+BadBoot:
+ mov si, offset 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 ptr BP_REL(SectsPerCluster)
+ mul cx // Times sectors per cluster
+ add ax, [bp-DataAreaStartLow] // Add start of data area
+ adc dx, [bp-DataAreaStartHigh] // Now we have DX:AX with the logical start sector of OSLOADER.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, 0
+
+ cmp dx, word ptr [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 ptr [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
+
+ push 0
+ push 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 1 // Set transfer count to 1 sector
+ push HEX(10) // 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 ptr BP_REL(BootDrive) // Drive number
+ mov ah, HEX(42) // Int 13h, AH = 42h - Extended Read
+ int HEX(13) // Call BIOS
+ jc BadBoot // If the read failed then abort
+
+ add sp, 16 // Remove disk address packet from stack
+
+ popa // Restore sector count & logical sector number
+
+ inc ax // Increment Sector to Read
+ adc dx, 0
+
+ push bx
+ mov bx, es
+ add bx, HEX(20) // 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 ptr BP_REL(SectorsPerTrack)
+ xchg ax, cx
+ div word ptr BP_REL(SectorsPerTrack) // Divide logical by SectorsPerTrack
+ inc dx // Sectors numbering starts at 1 not 0
+ xchg cx, dx
+ div word ptr BP_REL(NumberOfHeads) // Number of heads
+ mov dh, dl // Head to DH, drive to DL
+ mov dl, byte ptr BP_REL(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, HEX(0201)
+ int HEX(13) // 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, HEX(20)
+ mov es, bx
+ pop bx
+ // Increment read buffer for next sector
+ loop ReadSectorsCHSLoop // Read next sector
+
+ ret
+
+
+msgDiskError:
+ .asciz "Disk error\r\n"
+msgFreeLdr:
+ .asciz "ldr not found\r\n"
+// Sorry, need the space...
+//msgAnyKey:
+// .asciz "Press any key to restart\r\n"
+filename:
+ .ascii "FREELDR SYS"
+
+ .org 509 // Pad to 509 bytes
+
+BootPartition:
+ .byte 0
+
+BootSignature:
+ .word HEX(0aa55) // BootSector signature
+
+.endcode16
+
+END
Propchange: trunk/reactos/boot/freeldr/bootsect/fat.S
------------------------------------------------------------------------------
svn:eol-style = native
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