[tkreuzer] 52147: [FAT32] Fix the "portable" version of the fat32 bootsector Its now mostly identical to the one we currently use, only a few encoding differences
Author: tkreuzer Date: Wed Jun 8 12:45:56 2011 New Revision: 52147
URL: http://svn.reactos.org/svn/reactos?rev=52147&view=rev Log: [FAT32] Fix the "portable" version of the fat32 bootsector Its now mostly identical to the one we currently use, only a few encoding differences
Modified: trunk/reactos/boot/freeldr/bootsect/fat32.S
Modified: trunk/reactos/boot/freeldr/bootsect/fat32.S URL: http://svn.reactos.org/svn/reactos/trunk/reactos/boot/freeldr/bootsect/fat32... ============================================================================== --- trunk/reactos/boot/freeldr/bootsect/fat32.S [iso-8859-1] (original) +++ trunk/reactos/boot/freeldr/bootsect/fat32.S [iso-8859-1] Wed Jun 8 12:45:56 2011 @@ -10,6 +10,8 @@
#include <asm.inc>
+#define BP_REL(x) [bp+x-offset start] + .code16
//ORG HEX(7c00) @@ -21,59 +23,59 @@ OEMName: .ASCII "FrLdr1.0" BytesPerSector: - dw 512 + .word 512 SectsPerCluster: - db 0 + .byte 0 ReservedSectors: - dw 32 + .word 32 NumberOfFats: - db 2 + .byte 2 MaxRootEntries: - dw 0 // Always zero for FAT32 volumes + .word 0 // Always zero for FAT32 volumes TotalSectors: - dw 0 // Always zero for FAT32 volumes + .word 0 // Always zero for FAT32 volumes MediaDescriptor: - db HEX(0f8) + .byte HEX(0f8) SectorsPerFat: - dw 0 // Always zero for FAT32 volumes + .word 0 // Always zero for FAT32 volumes SectorsPerTrack: - dw 0 + .word 0 NumberOfHeads: - dw 0 + .word 0 HiddenSectors: - dd 0 + .long 0 TotalSectorsBig: - dd 0 + .long 0
// FAT32 Inserted Info SectorsPerFatBig: - dd 0 + .long 0 ExtendedFlags: - dw 0 + .word 0 FSVersion: - dw 0 + .word 0 RootDirStartCluster: - dd 0 + .long 0 FSInfoSector: - dw 0 + .word 0 BackupBootSector: - dw 6 + .word 6 Reserved1: - db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 + .byte 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
// End FAT32 Inserted Info BootDrive: - db 0 + .byte 0 Reserved: - db 0 + .byte 0 ExtendSig: - db HEX(29) + .byte HEX(29) SerialNumber: - dd 0 + .long 0 VolumeLabel: - db "NO NAME " + .ascii "NO NAME " FileSystem: - db "FAT32 " + .ascii "FAT32 "
main: xor ax,ax // Setup segment registers @@ -83,27 +85,27 @@ mov bp, HEX(7c00) mov sp, HEX(7c00) // Setup a stack
- cmp byte ptr ds:[BootDrive], HEX(0ff) // If they have specified a boot drive then use it + cmp byte ptr BP_REL(BootDrive), HEX(0ff) // If they have specified a boot drive then use it jne CheckSectorsPerFat
- mov byte ptr ds:[BootDrive], dl // Save the boot drive + mov byte ptr BP_REL(BootDrive), dl // Save the boot drive
CheckSectorsPerFat:
- cmp word ptr [SectorsPerFat], 0 // Check the old 16-bit value of SectorsPerFat + cmp word ptr BP_REL(SectorsPerFat), 0 // 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 word ptr [MaxRootEntries], 0// by comparing the DWORD at offset MaxRootEntries to zero + cmp dword ptr BP_REL(MaxRootEntries), 0// by comparing the DWORD at offset MaxRootEntries to zero jnz CheckFailed // If it is non-zero then exit with an error CheckFileSystemVersion: - cmp word ptr [FSVersion], 0 // Check the file system version word + cmp word ptr BP_REL(FSVersion), 0 // 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, HEX(0800) - mov dl, byte ptr [BootDrive] // Get boot drive in dl + 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
@@ -137,7 +139,7 @@ // First we have to load our extra boot code at // sector 14 into memory at [0000:7e00h] mov eax, HEX(0e) - add eax, dword ptr ds:[HiddenSectors] // Add the number of hidden sectors + add eax, dword ptr BP_REL(HiddenSectors) // Add the number of hidden sectors mov cx, 1 xor bx, bx mov es, bx // Read sector to [0000:7e00h] @@ -160,7 +162,7 @@ CheckInt13hExtensions: // Now check if this computer supports extended reads mov ah, HEX(41) // AH = 41h mov bx, HEX(55aa) // BX = 55AAh - mov dl, byte ptr ds:[BootDrive] // DL = drive (80h-FFh) + mov dl, byte ptr BP_REL(BootDrive) // DL = drive (80h-FFh) int HEX(13) // IBM/MS INT 13 Extensions - INSTALLATION CHECK jc ReadSectorsCHS // CF set on error (extensions not supported) cmp bx, HEX(0aa55) // BX = AA55h if installed @@ -179,7 +181,7 @@
ReadSectorsSetupDiskAddressPacket: mov word ptr ds:[LBASectorsRead],cx - push 0 + push 0 // push large 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 @@ -187,7 +189,7 @@ push 16 // Set size of packet to 10h mov si, sp // Setup disk address packet on stack
- mov dl, byte ptr ds:[BootDrive] // Drive number + 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 PrintDiskError // If the read failed then abort @@ -211,7 +213,7 @@ ret
LBASectorsRead: - dd 0 + .long 0
// Reads logical sectors into [ES:BX] @@ -223,15 +225,15 @@ ReadSectorsCHSLoop: pushad xor edx, edx - movzx ecx, word ptr ds:[SectorsPerTrack] + movzx ecx, word ptr BP_REL(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 ptr ds:[NumberOfHeads] // Divide logical by number of heads + div word ptr BP_REL(NumberOfHeads) // Divide logical by number of heads mov dh, dl // Head in DH - mov dl, byte ptr ds:[BootDrive] // Drive number in DL + mov dl, byte ptr BP_REL(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 @@ -267,7 +269,7 @@ // Displays a file system error message // And reboots PrintFileSystemError: - mov si,msgFileSystemError // FreeLdr not found message + mov si, offset msgFileSystemError // FreeLdr not found message call PutChars // Display it
Reboot: @@ -286,27 +288,26 @@ int HEX(10) jmp short PutChars Done: - retn + ret
BiosCHSDriveSize: - dd 0 + .long 0
msgDiskError: - db "Disk error", 13, 10, 0 + .asciz "Disk error\r\n" msgFileSystemError: - db "File system error", 13, 10, 0 + .asciz "File system error\r\n" msgAnyKey: - db "Press any key to restart", 13, 10, 0 - -// times 509-($-$$) db 0 // Pad to 509 bytes + .asciz "Press any key to restart\r\n" + .org 509 // Pad to 509 bytes
BootPartition: - db 0 + .byte 0
BootSignature: - dw 0aa55h // BootSector signature + .word HEX(0aa55) // BootSector signature
// End of bootsector // @@ -323,7 +324,7 @@ StartSearch:
// Now we must get the first cluster of the root directory - mov eax, dword ptr ds:[RootDirStartCluster] + mov eax, dword ptr BP_REL(RootDirStartCluster) cmp eax, HEX(0ffffff8) // 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 @@ -336,7 +337,7 @@ // Now we have to find our way through the root directory to // The OSLOADER.SYS file xor bx,bx - mov bl, byte ptr ds:[SectsPerCluster] + mov bl, byte ptr BP_REL(SectsPerCluster) shl bx, 4 // BX = BX * 512 / 32 mov ax, HEX(2000) // We loaded at 2000:0000 mov es, ax @@ -362,9 +363,9 @@ jnz FindFile // Last entry?
// Get the next root dir cluster and try again until we run out of clusters - mov eax, dword ptr ds:[RootDirStartCluster] + mov eax, dword ptr BP_REL(RootDirStartCluster) call GetFatEntry - mov dword ptr ds:[RootDirStartCluster], eax + mov dword ptr BP_REL(RootDirStartCluster), eax jmp StartSearch
FoundFile: @@ -374,9 +375,9 @@
xor di, di // ES:DI has dir entry xor dx, dx - mov ax, word ptr es:[di+14h] // Get start cluster high word + mov ax, word ptr es:[di+20] // Get start cluster high word shl eax, 16 - mov ax, word ptr es:[di+1ah] // Get start cluster low word + mov ax, word ptr es:[di+26] // Get start cluster low word
CheckStartCluster: cmp eax, 2 // Check and see if the start cluster starts at cluster 2 or above @@ -401,7 +402,7 @@ pop es
xor bx, bx - mov bl, byte ptr ds:[SectsPerCluster] + mov bl, byte ptr BP_REL(SectsPerCluster) shl bx, 5 // BX = BX * 512 / 16 mov ax, es // Increment the load address by add ax, bx // The size of a cluster @@ -415,7 +416,7 @@ jmp LoadFile // Load the next cluster (if any)
LoadFileDone: - mov dl, byte ptr ds:[BootDrive] // Load boot drive into DL + mov dl, byte ptr BP_REL(BootDrive) // Load boot drive into DL mov dh, byte ptr ds:[BootPartition] // Load boot partition into DH
push 0 // push segment (0x0000) @@ -432,12 +433,12 @@ 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 ptr ds:[BytesPerSector] + movzx ebx, word ptr BP_REL(BytesPerSector) push ebx div ebx // FAT Sector Number = EAX / BytesPerSector - movzx ebx, word ptr ds:[ReservedSectors] + movzx ebx, word ptr BP_REL(ReservedSectors) add eax, ebx // FAT Sector Number += ReservedSectors - mov ebx, dword ptr ds:[HiddenSectors] + mov ebx, dword ptr BP_REL(HiddenSectors) add eax, ebx // FAT Sector Number += HiddenSectors pop ebx dec ebx @@ -449,15 +450,15 @@ // to see which FAT is the active one // and use it, or if they are mirrored then // no worries - movzx ebx, word ptr ds:[ExtendedFlags] // Get extended flags and put into ebx + movzx ebx, word ptr BP_REL(ExtendedFlags) // Get extended flags and put into ebx and bx, HEX(0f) // 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 ptr ds:[NumberOfFats] // Compare bl to number of fats + cmp bl, byte ptr BP_REL(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, dword ptr ds:[SectorsPerFatBig] // Get the number of sectors occupied by one fat in eax + mov eax, dword ptr BP_REL(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 @@ -486,7 +487,7 @@ 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 + .long HEX(0ffffffff) // There is no need to re-read the same sector if we don't have to
// Reads cluster number in EAX into [ES:0000] @@ -496,19 +497,19 @@ dec eax dec eax xor edx, edx - movzx ebx, byte ptr ds:[SectsPerCluster] + movzx ebx, byte ptr BP_REL(SectsPerCluster) mul ebx push eax xor edx, edx - movzx eax, byte ptr ds:[NumberOfFats] - mul dword ptr ds:[SectorsPerFatBig] - movzx ebx, word ptr ds:[ReservedSectors] + movzx eax, byte ptr BP_REL(NumberOfFats) + mul dword ptr BP_REL(SectorsPerFatBig) + movzx ebx, word ptr BP_REL(ReservedSectors) add eax, ebx - add eax, dword ptr ds:[HiddenSectors] + add eax, dword ptr BP_REL(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 ptr ds:[SectsPerCluster] + movzx cx, byte ptr BP_REL(SectsPerCluster) call ReadSectors ret
@@ -523,15 +524,15 @@ jmp Reboot
msgFreeLdr: - db "freeldr.sys not found", 13, 10, 0 + .asciz "freeldr.sys not found\r\n" filename: - db "FREELDR SYS" + .ascii "FREELDR SYS" msgLoading: - db "Loading FreeLoader...", 13, 10, 0 - - //times 1022-($-$$) db 0 // Pad to 1022 bytes - - dw 0aa55h // BootSector signature + .asciz "Loading FreeLoader...\r\n" + +.org 1022 // Pad to 1022 bytes + + .word HEX(0aa55) // BootSector signature
.endcode16
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tkreuzer＠svn.reactos.org