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page ,132 title ntfsboot - NTFS boot loader name ntfsboot
; The ROM in the IBM PC starts the boot process by performing a hardware; initialization and a verification of all external devices. If all goes; well, it will then load from the boot drive the sector from track 0, head 0,; sector 1. This sector is placed at physical address 07C00h.;; The boot code's sole resposiblity is to find NTLDR, load it at; address 2000:0000, and then jump to it.;; The boot code understands the structure of the NTFS root directory,; and is capable of reading files. There is no contiguity restriction.;; DEBUG EQU 1MASM equ 1 .xlist .286
A_DEFINED EQU 1
include ntfs.inc
DoubleWord struclsw dw ?msw dw ?DoubleWord ends
;; The following are various segments used by the boot loader. The first; two are the segments where the boot sector is initially loaded and where; the boot sector is relocated to. The third is the static location; where the NTLDR is loaded.;
BootSeg segment at 07c0h ; this is where the MBR loads us initially.BootSeg ends
NewSeg segment at 0d00h ; this is where we'll relocate to.NewSeg ends ; enough for 16 boot sectors + ; 4-sector scratch ; below where we'll load NTLDR.
LdrSeg segment at 2000h ; we want to load the loader at 2000:0000LdrSeg ends
;/********************** START OF SPECIFICATIONS ************************/;/* */;/* SUBROUTINE NAME: ntfsboot */;/* */;/* DESCRIPTIVE NAME: Bootstrap loader */;/* */;/* FUNCTION: To load NTLDR into memory. */;/* */;/* NOTES: ntfsboot is loaded by the ROM BIOS (Int 19H) at */;/* physical memory location 0000:7C00H. */;/* ntfsboot runs in real mode. */;/* This boot record is for NTFS volumes only. */;/* */;/* ENTRY POINT: ntfsboot */;/* LINKAGE: Jump (far) from Int 19H */;/* */;/* INPUT: CS:IP = 0000:7C00H */;/* SS:SP = 0030:00FAH (CBIOS dependent) */;/* */;/* EXIT-NORMAL: DL = INT 13 drive number we booted from */;/* Jmp to main in NTLDR */;/* */;/* EXIT-ERROR: None */;/* */;/* EFFECTS: NTLDR is loaded into the physical memory */;/* location 00020000H */;/* */;/*********************** END OF SPECIFICATIONS *************************/BootCode segment ;would like to use BootSeg here, but LINK flips its lid assume cs:BootCode,ds:nothing,es:nothing,ss:nothing
org 0 ; start at beginning of segment, not 0100h.
public _ntfsboot_ntfsboot label near jmp start .errnz ($-_ntfsboot) GT (3) ;<FATAL PROBLEM: JMP is more than three bytes>
org 3
Version db "NTFS " ; Signature, must be "NTFS "BPB label byteBytesPerSector dw 512 ; Size of a physical sectorSectorsPerCluster db 1 ; Sectors per allocation unit
;; Traditionally the next 7 bytes were the reserved sector count, fat count,; root dir entry count, and the small volume sector count. However all of; these fields must be 0 on NTFS volumes.;; We use this space to store some temporary variables used by the boot code,; which avoids the need for separate space in sector 0 to store them.; We also take advantage of the free 0-initialization to save some space; by avoiding the code to initialize them.;; Note that ideally we'd want to use an unused field for the SectorCount; and initialize it to 16. This would let us save a few bytes by avoiding; code to explicitly initialize this value before we read the 16 boot sectors.; However setup and other code tends to preserve the entire bpb area when; it updates boot code, so we avoid a dependency here and initialize; the value explicitly to 16 in the first part of the boot code.;SectorCount dw 0 ; number of sectors to readSectorBase dd 0 ; start sector for read requestHaveXInt13 db 0 ; extended int13 available flag
Media db 0f8h ; Media byteFatSectors dw 0 ; (always 0 on NTFS)SectorsPerTrack dw 0 ; Sectors per trackHeads dw 0 ; Number of surfacesHiddenSectors dd 0 ; partition start LBA
;; The field below is traditionally the large sector count and is; always 0 on NTFS. We use it here for a value the boot code calculates,; namely the number of sectors visible on the drive via conventional int13.;Int13Sectors dd 0
DriveNumber db 80h ; int13 unit number
db 3 dup (?) ; alignment filler
;; The following is the rest of the NTFS Sector Zero information.; The offsets of most of these fields cannot be changed without changing; all code that validates, formats, recognizes, etc, NTFS volumes.; In other words, don't change it.;SectorsOnVolume db (size LARGE_INTEGER) dup (?)MftStartLcn db (size LARGE_INTEGER) dup (?)Mft2StartLcn db (size LARGE_INTEGER) dup (?)ClustersPerFrs dd ?DefClustersPerBuf dd ?SerialNumber db (size LARGE_INTEGER) dup (?)CheckSum dd ?
;; Make sure size of fields matches what fs_rec.sys thinks is should be; .errnz ($-_ntfsboot) NE (54h)
;****************************************************************************start:;; First of all, set up the segments we need (stack and data).; cli xor ax,ax ; Set up the stack to just before mov ss,ax ; this code. It'll be moved after mov sp,7c00h ; we relocate. sti
mov ax,Bootseg ; Address BPB with DS. mov ds,ax assume ds:BootCode
call Int13SecCnt ; determine range of regular int13
;; Read bootcode and jump to code in sector 1.; Assumes HaveXInt13 and SectorBase are initialized to 0,; which they are since they are stored in areas of the BPB; that must be 0 on NTFS volumes.; mov ax,NewSeg mov es,ax xor bx,bx ; es:bx = transfer address
mov byte ptr SectorCount,16 ; word field is 0 on-disk so byte init is OK call ReadSectors
push NewSeg push offset mainboot retf
;; Determine the number of sectors addressable via; conventional int13. If we can't get drive params for some reason; then something is very wrong -- we'll try to force the caller; to use conventional int13 by maxing out the sector count.;; Input: ds addresses start of first sector;; Output: in eax; also stored in Int13Sectors variable.;; Preserves: assume none.;Int13SecCnt proc near mov dl,DriveNumber ; int13 unit number mov ah,8 ; get drive params int 13h ; call BIOS jnc @f ; no error, procede mov cx,-1 ; strange case, fake registers to force mov dh,cl ; use of standard int13 (set all vals to max)@@:.386 movzx eax,dh ; eax = max head # (0-255) inc ax ; eax = heads (1-256) movzx edx,cl ; edx = sectors per track + cyl bits and dl,3fh ; edx = sectors per track (1-63) mul dx ; eax = sectors per cylinder, edx = 0 xchg cl,ch shr ch,6 ; cx = max cylinder # (0-1023) inc cx ; cx = cylinders (1-1024) movzx ecx,cx ; ecx = cylinders (1-1024) mul ecx ; eax = sectors visible via int13, edx = 0 mov Int13Sectors,eax ; save # sectors addressable via int13.286 retInt13SecCnt endp
;; Determine whether extended int13 services are available on the boot drive.;; Stores result (boolean) in HaveXInt13 variable.;; Preserves: assume none.;HaveInt13Ext proc near mov ah,41h mov bx,055aah mov dl,DriveNumber int 13h jc @f ; error from int13 means no xint13 cmp bx,0aa55h ; absence of sig means no xint13 jne @f test cl,1 ; bit 0 off means no xint13 jz @f inc byte ptr HaveXInt13 ; xint13 is available@@: retHaveInt13Ext endp
;; Read SectorCount sectors starting at logical sector SectorBase,; into es:bx, using extended int13 if necessary.;; Preserves all;ReadSectors proc near.386 pushad ; save registers push ds push es
read_loop: mov eax,SectorBase ; logical starting sector add eax,HiddenSectors ; eax = physical starting sector cmp eax,Int13Sectors ; determine if standard int13 is ok jb stdint13
push ds ; preserve ds
db 66h ; hand-coded 32-bit push of 8-bit immediate push 0 ; high 32 bits of sector # push eax ; low 32 bits of sector # push es push bx ; transfer address push dword ptr 10010h ; transfer 1 sector, packet size = 16
cmp byte ptr HaveXInt13,0 jne @f ; already know we have xint13 available call HaveInt13Ext ; see if we have it cmp byte ptr HaveXInt13,0
je BootErr$he ; need it but don't have it
@@: mov ah,42h ; extended read mov dl,DriveNumber ; dl = int13 unit # push ss pop ds mov si,sp ; ds:si -> param packet
int 13h
pop eax ; throw away first 4 bytes of param packet pop bx ; restore es:bx from param packet pop es pop eax ; throw away last 8 bytes of param packet pop eax ; without clobbering carry flag
pop ds ; restore ds
jmp short did_read
stdint13: xor edx,edx ; edx:eax = absolute sector number movzx ecx,SectorsPerTrack ; ecx = sectors per track div ecx ; eax = track, edx = sector within track (0-62) inc dl ; dl = sector within track (1-63) mov cl,dl ; cl = sector within track mov edx,eax shr edx,16 ; dx:ax = track div Heads ; ax = cylinder (0-1023), dx = head (0-255) xchg dl,dh ; dh = head mov dl,DriveNumber ; dl = int13 unit # mov ch,al ; ch = bits 0-7 of cylinder shl ah,6 or cl,ah ; bits 6-7 of cl = bits 8-9 of cylinder mov ax,201h ; read 1 sector int 13hdid_read: jc BootErr$he
read_next: mov ax,es ; advance transfer address add ax,20h ; by moving segment register along mov es,ax ; thus no 64K limit on transfer length
inc SectorBase ; advance sector number dec SectorCount ; see if done jnz read_loop ; not done
pop es pop ds popad ; restore registers.286 retReadSectors endp
BootErr$he:
mov al,byte ptr TXT_MSG_SYSINIT_BOOT_ERRORBootErr2:
call BootErr$print mov al,byte ptr TXT_MSG_SYSINIT_REBOOT call BootErr$print sti jmp $ ; Wait forever
BootErr$print:;; al is offset - 256 of message. Adjust to form real offset; and stick in si so lodsb below will work.; mov ah,1 mov si,ax
BootErr$print1: lodsb ; Get next character cmp al,0 je BootErr$Done mov ah,14 ; Write teletype mov bx,7 ; Attribute int 10h ; Print it jmp BootErr$print1BootErr$Done: ret
;****************************************************************************
;; Message table.;; We put English messages here as a placeholder only, so that in case; anyone uses bootntfs.h without patching new messages in, things will; still be correct (in English, but at least functional).;MSG_SYSINIT_BOOT_ERROR:
DB 13,10,'A disk read error occurred',0
MSG_SYSINIT_FILE_NOT_FD:
DB 13,10,'NTLDR is missing',0
MSG_SYSINIT_NTLDR_CMPRS:
DB 13,10,'NTLDR is compressed',0
MSG_SYSINIT_REBOOT:
DB 13,10,'Press Ctrl+Alt+Del to restart',13,10,0
;; Now build a table with the low byte of the offset to each message.; Code that patches the boot sector messages updates this table.; .errnz ($-_ntfsboot) GT (512-8) ORG 512 - 8TXT_MSG_SYSINIT_BOOT_ERROR: db OFFSET (MSG_SYSINIT_BOOT_ERROR - _ntfsboot) - 256TXT_MSG_SYSINIT_FILE_NOT_FD: db OFFSET (MSG_SYSINIT_FILE_NOT_FD - _ntfsboot) - 256TXT_MSG_SYSINIT_NTLDR_CMPRS: db OFFSET (MSG_SYSINIT_NTLDR_CMPRS - _ntfsboot) - 256TXT_MSG_SYSINIT_REBOOT: db OFFSET (MSG_SYSINIT_REBOOT - _ntfsboot) - 256
.errnz ($-_ntfsboot) NE (512-4) db 0,0,55h,0aah
; Name we look for. ntldr_length is the number of characters,; ntldr_name is the name itself. Note that it is not NULL; terminated, and doesn't need to be.;ntldr_name_length dw 5
ntldr_name dw 'N', 'T', 'L', 'D', 'R'
; Predefined name for index-related attributes associated with an; index over $FILE_NAME;index_name_length dw 4index_name dw '$', 'I', '3', '0'
; Global variables. These offsets are all relative to NewSeg.;AttrList dd 0e000h ; Offset of buffer to hold attribute listMftFrs dd 3000h ; Offset of general scratch buffer for FRSSegmentsInMft dd ? ; number of FRS's with MFT Data attribute recordsRootIndexFrs dd ? ; Offset of Root Index FRSAllocationIndexFrs dd ? ; Offset of Allocation Index FRS ; KPeeryBitmapIndexFrs dd ? ; Offset of Bitmap Index FRS ; KPeeryIndexRoot dd ? ; Offset of Root Index $INDEX_ROOT attributeIndexAllocation dd ? ; Offset of Root Index $INDEX_ALLOCATION attributeIndexBitmap dd ? ; Offset of Root Index $BITMAP attributeNtldrFrs dd ? ; Offset of NTLDR FRSNtldrData dd ? ; Offset of NTLDR $DATA attributeIndexBlockBuffer dd ? ; Offset of current index bufferIndexBitmapBuffer dd ? ; Offset of index bitmap bufferNextBuffer dd ? ; Offset of next free byte in buffer space
BytesPerCluster dd ? ; Bytes per clusterBytesPerFrs dd ? ; Bytes per File Record Segment
;; For floppyless booting, winnt32.exe creates c:\$win_nt$.~bt\bootsec.dat and; places an entry in boot.ini for it (the boot selection says something; like "Windows NT Setup or Upgrade"). When that is selected, the boot loader; loads 16 sectors worth of data from bootsect.dat into d000 (which is where; the first sector of this code would have loaded it) and jumps into it at; a known location of 256h. That was correct in earlier versions of NT; but is not correct now because the 4 fields below were added to this sector.;; Note that 0000 is "add [bx+si],al" which because of the way the boot loader; is written happens to be a benign add of 0 to something in segment 7c0,; which doesn't seem to hose anything but is still somewhat random.;; We code in a jump here so as this new code proliferates we get this; cleaned up.; .errnz $-_ntfsboot ne 256hSectorsPerFrs label dword ; Sectors per File Record Segment jmp short mainboot nop nop .errnz $-_ntfsboot ne 25ah
MftLcnFrs dd ? ; Offset scratch FRS buffer for LookupMftLcnBytesPerIndexBlock dd ? ; Bytes per index alloc block in root indexClustersPerIndexBlock dd ? ; Clusters per index alloc block in root indexSectorsPerIndexBlock dd ? ; Sectors per index block in root index
.386
SAVE_ALL macro
push es push ds pushad
endm
RESTORE_ALL macro
popad nop pop ds pop es
endm
;****************************************************************************;; mainboot - entry point after 16 boot sectors have been read in;;mainboot proc far
; Get the new ds and the new stack. Note that ss is zero.; mov ax, cs ; Set DS to CS mov ds, ax
shl ax, 4 ; convert to an offset. cli mov sp, ax ; load new stack, just before boot code. sti
;; Reinitialize xint13-related variables; call Int13SecCnt ; determine range of regular int13
; Set up the FRS buffers. The MFT buffer is in a fixed; location, and the other three come right after it. The; buffer for index allocation blocks comes after that.;
; Compute the useful constants associated with the volume; movzx eax, BytesPerSector ; eax = Bytes per Sector movzx ebx, SectorsPerCluster ; ebx = Sectors Per Cluster mul ebx ; eax = Bytes per Cluster mov BytesPerCluster, eax
mov ecx, ClustersPerFrs ; ecx = clusters per frs cmp cl, 0 ; is ClustersPerFrs less than zero? jg mainboot$1
; If the ClustersPerFrs field is negative, we calculate the number; of bytes per FRS by negating the value and using that as a shif count.;
neg cl mov eax, 1 shl eax, cl ; eax = bytes per frs jmp mainboot$2
mainboot$1:
; Otherwise if ClustersPerFrs was positive, we multiply by bytes; per cluster.
mov eax, BytesPerCluster mul ecx ; eax = bytes per frs
mainboot$2:
mov BytesPerFrs, eax movzx ebx, BytesPerSector xor edx, edx ; zero high part of dividend div ebx ; eax = sectors per frs mov SectorsPerFrs, eax
; Set up the MFT FRS's---this will read all the $DATA attribute; records for the MFT.;
call SetupMft
; Set up the remaining FRS buffers. The RootIndex FRS comes; directly after the last MFT FRS, followed by the NTLdr FRS; and the Index Block buffer.; mov ecx, NextBuffer mov RootIndexFrs, ecx
add ecx, BytesPerFrs ; AllocationFrs may be different mov AllocationIndexFrs, ecx ; from RootIndexFrs - KPeery
add ecx, BytesPerFrs ; BitmapFrs may be different mov BitmapIndexFrs, ecx ; from RootIndexFrs - KPeery
add ecx, BytesPerFrs mov NtldrFrs, ecx
add ecx, BytesPerFrs mov IndexBlockBuffer, ecx
;; Read the root index, allocation index and bitmap FRS's and locate; the interesting attributes.;
mov eax, $INDEX_ROOT mov ecx, RootIndexFrs call LoadIndexFrs
or eax, eax
jz BootErr$he
mov IndexRoot, eax ; offset in Frs buffer
mov eax, $INDEX_ALLOCATION ; Attribute type code mov ecx, AllocationIndexFrs ; FRS to search call LoadIndexFrs
mov IndexAllocation, eax
mov eax, $BITMAP ; Attribute type code mov ecx, BitmapIndexFrs ; FRS to search call LoadIndexFrs
mov IndexBitmap, eax
; Consistency check: the index root must exist, and it; must be resident.; mov eax, IndexRoot or eax, eax
jz BootErr$he
cmp [eax].ATTR_FormCode, RESIDENT_FORM
jne BootErr$he
; Determine the size of the index allocation buffer based; on information in the $INDEX_ROOT attribute. The index; bitmap buffer comes immediately after the index block buffer.;; eax -> $INDEX_ROOT attribute record; lea edx, [eax].ATTR_FormUnion ; edx -> resident info add ax, [edx].RES_ValueOffset ; eax -> value of $INDEX_ROOT
movzx ecx, [eax].IR_ClustersPerBuffer mov ClustersPerIndexBlock, ecx
mov ecx, [eax].IR_BytesPerBuffer mov BytesPerIndexBlock, ecx
mov eax, BytesPerIndexBlock movzx ecx, BytesPerSector xor edx, edx div ecx ; eax = sectors per index block mov SectorsPerIndexBlock, eax
mov eax, IndexBlockBuffer add eax, BytesPerIndexBlock mov IndexBitmapBuffer, eax
; Next consistency check: if the $INDEX_ALLOCATION attribute; exists, the $INDEX_BITMAP attribute must also exist.; cmp IndexAllocation, 0 je mainboot30
cmp IndexBitmap, 0 ; since IndexAllocation exists, the
je BootErr$he ; bitmap must exist, too.
; Since the bitmap exists, we need to read it into the bitmap; buffer. If it's resident, we can just copy the data.;
mov ebx, IndexBitmap ; ebx -> index bitmap attribute push ds pop es mov edi, IndexBitmapBuffer ; es:edi -> index bitmap buffer
call ReadWholeAttribute
mainboot30:;; OK, we've got the index-related attributes.; movzx ecx, ntldr_name_length ; ecx = name length in characters mov eax, offset ntldr_name ; eax -> name
call FindFile
or eax, eax jz BootErr$fnf
; Read the FRS for NTLDR and find its data attribute.;; eax -> Index Entry for NTLDR.; mov eax, [eax].IE_FileReference.REF_LowPart
push ds pop es ; es:edi = target buffer mov edi, NtldrFrs
call ReadFrs
mov eax, NtldrFrs ; pointer to FRS mov ebx, $DATA ; requested attribute type mov ecx, 0 ; attribute name length in characters mov edx, 0 ; attribute name (NULL if none)
call LocateAttributeRecord
; eax -> $DATA attribute for NTLDR; or eax, eax ; if eax is zero, attribute not found. jnz mainboot$FoundData
;; The ntldr $DATA segment is fragmented. Search the attribute list; for the $DATA member. And load it from there.; mov ecx, $DATA ; Attribute type code mov eax, NtldrFrs ; FRS to search
call SearchAttrList ; search attribute list for FRN ; of specified ($DATA)
or eax, eax ; if eax is zero, attribute not found. jz BootErr$fnf
;; We found the FRN of the $DATA attribute; load that into memory.; push ds pop es ; es:edi = target buffer mov edi, NtldrFrs
call ReadFrs
;; Determine the beginning offset of the $DATA in the FRS; mov eax, NtldrFrs ; pointer to FRS mov ebx, $DATA ; requested attribute type mov ecx, 0 ; attribute name length in characters mov edx, 0 ; attribute name (NULL if none)
call LocateAttributeRecord
; eax -> $DATA attribute for NTLDR; or eax, eax ; if eax is zero, attribute not found. jz BootErr$fnf
mainboot$FoundData:
; Get the attribute record header flags, and make sure none of the; `compressed' bits are set
movzx ebx, [eax].ATTR_Flags and ebx, ATTRIBUTE_FLAG_COMPRESSION_MASK jnz BootErr$ntc
mov ebx, eax ; ebx -> $DATA attribute for NTLDR
push LdrSeg pop es ; es = segment addres to read into sub edi, edi ; es:edi = buffer address
call ReadWholeAttribute
;; We've loaded NTLDR--jump to it.;; Before we go to NTLDR, set up the registers the way it wants them:; DL = INT 13 drive number we booted from; mov dl, DriveNumber mov ax,1000 mov es, ax ; we don't really need this lea si, BPB sub ax,ax push LdrSeg push ax retf ; "return" to NTLDR.
mainboot endp
.386;****************************************************************************;; ReadClusters - Reads a run of clusters from the disk.;; ENTRY: eax == LCN to read; edx == clusters to read; es:edi -> Target buffer;; USES: none (preserves all registers);ReadClusters proc near
SAVE_ALL
mov ebx, edx ; ebx = clusters to read. movzx ecx, SectorsPerCluster ; ecx = cluster factor
mul ecx ; Convert LCN to sectors (wipes out edx!) mov SectorBase, eax ; Store starting sector in SectorBase
mov eax, ebx ; eax = number of clusters mul ecx ; Convert EAX to sectors (wipes out edx!) mov SectorCount, ax ; Store number of sectors in SectorCount
;; Note that ReadClusters gets its target buffer in es:edi but calls; the ReadSectors worker function that takes a target in es:bx--we need; to normalize es:edi so that we don't overflow bx.; mov bx, di and bx, 0Fh mov ax, es shr edi, 4 add ax, di ; ax:bx -> target buffer
push ax pop es ; es:bx -> target buffer
call ReadSectors
RESTORE_ALL ret
ReadClusters endp
;;****************************************************************************;; LocateAttributeRecord -- Find an attribute record in an FRS.;; ENTRY: EAX -- pointer to FRS; EBX -- desired attribute type code; ECX -- length of attribute name in characters; EDX -- pointer to attribute name;; EXIT: EAX points at attribute record (0 indicates not found);; USES: All;LocateAttributeRecord proc near
; get the first attribute record.; add ax, word ptr[eax].FRS_FirstAttribute
; eax -> next attribute record to investigate.; ebx == desired type; ecx == name length; edx -> pointer to name;lar10: cmp [eax].ATTR_TypeCode, 0ffffffffh je lar99
cmp dword ptr[eax].ATTR_TypeCode, ebx jne lar80
; this record is a potential match. Compare the names:;; eax -> candidate record; ebx == desired type; ecx == name length; edx -> pointer to name; or ecx, ecx ; Did the caller pass in a name length? jnz lar20
; We want an attribute with no name--the current record is; a match if and only if it has no name.; cmp [eax].ATTR_NameLength, 0 jne lar80 ; Not a match.
; It's a match, and eax is set up correctly, so return.; ret
; We want a named attribute.;; eax -> candidate record; ebx == desired type; ecx == name length; edx -> pointer to name;lar20: cmp cl, [eax].ATTR_NameLength jne lar80 ; Not a match.
; Convert name in current record to uppercase.; mov esi, eax add si, word ptr[eax].ATTR_NameOffset
call UpcaseName
; eax -> candidate record; ebx == desired type; ecx == name length; edx -> pointer to name; esi -> Name in current record (upcased); push ecx ; save cx
push ds ; Copy data segment into es pop es mov edi, edx ; note that esi is already set up.
repe cmpsw ; zero flag is set if equal
pop ecx ; restore cx
jnz lar80 ; not a match
; eax points at a matching record.; ret
;; This record doesn't match; go on to the next.;; eax -> rejected candidate attribute record; ebx == desired type; ecx == Name length; edx -> desired name;lar80: cmp [eax].ATTR_RecordLength, 0 ; if the record length is zero je lar99 ; the FRS is corrupt.
add eax, [eax].ATTR_RecordLength; Go to next record jmp lar10 ; and try again
; Didn't find it.;lar99: sub eax, eax ret
LocateAttributeRecord endp
;****************************************************************************;; LocateIndexEntry -- Find an index entry in a file name index;; ENTRY: EAX -> pointer to index header; EBX -> file name to find; ECX == length of file name in characters;; EXIT: EAX points at index entry. NULL to indicate failure.;; USES: All;LocateIndexEntry proc near
; Convert the input name to upper-case;
mov esi, ebx call UpcaseName
ifdef DEBUG call PrintName call Debug2endif ; DEBUG
add eax, [eax].IH_FirstIndexEntry
; EAX -> current entry; EBX -> file name to find; ECX == length of file name in characters;lie10: test [eax].IE_Flags, INDEX_ENTRY_END ; Is it the end entry? jnz lie99
lea edx, [eax].IE_Value ; edx -> FILE_NAME attribute value
ifdef DEBUG; DEBUG CODE -- list file names as they are examined
SAVE_ALL
call Debug3 movzx ecx, [edx].FN_FileNameLength ; ecx = chars in name lea esi, [edx].FN_FileName ; esi -> name call PrintName
RESTORE_ALLendif ; DEBUG
; EAX -> current entry; EBX -> file name to find; ECX == length of file name in characters; EDX -> FILE_NAME attribute
cmp cl, [edx].FN_FileNameLength ; Is name the right length? jne lie80
lea esi, [edx].FN_FileName ; Get name from FILE_NAME structure
call UpcaseName
push ecx ; save ecx
push ds pop es ; copy data segment into es for cmpsw mov edi, ebx ; edi->search name (esi already set up) repe cmpsw ; zero flag is set if they're equal
pop ecx ; restore ecx
jnz lie80
; the current entry matches the search name, and eax points at it.; ret
; The current entry is not a match--get the next one.; EAX -> current entry; EBX -> file name to find; ECX == length of file name in characters;lie80: cmp [eax].IE_Length, 0 ; If the entry length is zero je lie99 ; then the index block is corrupt.
add ax, [eax].IE_Length ; Get the next entry.
jmp lie10
; Name not found in this block. Set eax to zero and return;lie99: xor eax, eax ret
LocateIndexEntry endp
;****************************************************************************;; ReadWholeAttribute - Read an entire attribute value;; ENTRY: ebx -> attribute; es:edi -> target buffer;; USES: ALL;ReadWholeAttribute proc near
cmp [ebx].ATTR_FormCode, RESIDENT_FORM jne rwa10
; The attribute is resident.; ebx -> attribute; es:edi -> target buffer;
SAVE_ALL
lea edx, [ebx].ATTR_FormUnion ; edx -> resident form info mov ecx, [edx].RES_ValueLength ; ecx = bytes in value mov esi, ebx ; esi -> attribute add si, [edx].RES_ValueOffset ; esi -> attribute value
rep movsb ; copy bytes from value to buffer
RESTORE_ALL
ret ; That's all!
rwa10:;; The attribute type is non-resident. Just call; ReadNonresidentAttribute starting at VCN 0 and; asking for the whole thing.;; ebx -> attribute; es:edi -> target buffer; lea edx, [ebx].ATTR_FormUnion ; edx -> nonresident form info mov ecx, [edx].NONRES_HighestVcn.LowPart; ecx = HighestVcn inc ecx ; ecx = clusters in attribute
sub eax, eax ; eax = 0 (first VCN to read)
call ReadNonresidentAttribute
ret
ReadWholeAttribute endp
;****************************************************************************;; ReadNonresidentAttribute - Read clusters from a nonresident attribute;; ENTRY: EAX == First VCN to read; EBX -> Attribute; ECX == Number of clusters to read; ES:EDI == Target of read;; EXIT: None.;; USES: None (preserves all registers with SAVE_ALL/RESTORE_ALL);ReadNonresidentAttribute proc near
SAVE_ALL
cmp [ebx].ATTR_FormCode, NONRESIDENT_FORM je ReadNR10
; This attribute is not resident--the disk is corrupt.
jmp BootErr$he
ReadNR10:; eax == Next VCN to read; ebx -> Attribute; ecx -> Remaining clusters to read; es:edi -> Target of read;
cmp ecx, 0 jne ReadNR20
; Nothing left to read--return success.; RESTORE_ALL ret
ReadNR20: push ebx ; pointer to attribute push eax ; Current VCN
push ecx push edi push es
call ComputeLcn ; eax = LCN to read, ecx = run length mov edx, ecx ; edx = remaining run length
pop es pop edi pop ecx
; eax == LCN to read; ecx == remaining clusters to read; edx == remaining clusters in current run; es:edi == Target of read; TOS == Current VCN; TOS + 4 == pointer to attribute; cmp ecx, edx jge ReadNR30
; Run length is greater than remaining request; only read; remaining request.; mov edx, ecx ; edx = Remaining request
ReadNR30:; eax == LCN to read; ecx == remaining clusters to read; edx == clusters to read in current run; es:edi == Target of read; TOS == Current VCN; TOS + == pointer to attribute;
call ReadClusters
sub ecx, edx ; Decrement clusters remaining in request mov ebx, edx ; ebx = clusters read
mov eax, edx ; eax = clusters read movzx edx, SectorsPerCluster mul edx ; eax = sectors read (wipes out edx!) movzx edx, BytesPerSector mul edx ; eax = bytes read (wipes out edx!)
add edi, eax ; Update target of read
pop eax ; eax = previous VCN add eax, ebx ; update VCN to read
pop ebx ; ebx -> attribute jmp ReadNR10
ReadNonresidentAttribute endp
;****************************************************************************;; ReadIndexBlockSectors - Read sectors from an index allocation attribute;; ENTRY: EAX == First VBN to read; EBX -> Attribute; ECX == Number of sectors to read; ES:EDI == Target of read;; EXIT: None.;; USES: None (preserves all registers with SAVE_ALL/RESTORE_ALL);ReadIndexBlockSectors proc near
SAVE_ALL
cmp [ebx].ATTR_FormCode, NONRESIDENT_FORM je ReadIBS_10
; This attribute is resident--the disk is corrupt.
jmp BootErr$he
ReadIBS_10:; eax == Next VBN to read; ebx -> Attribute; ecx -> Remaining sectors to read; es:edi -> Target of read;
cmp ecx, 0 jne ReadIBS_20
; Nothing left to read--return success.;
RESTORE_ALL ret
ReadIBS_20: push ebx ; pointer to attribute push eax ; Current VBN
push ecx push edi push es
; Convert eax from a VBN back to a VCN by dividing by SectorsPerCluster. ; The remainder of this division is the sector offset in the cluster we ; want. Then use the mapping information to get the LCN for this VCN, ; then multiply to get back to LBN. ;
push ecx ; save remaining sectors in request
xor edx, edx ; zero high part of dividend movzx ecx, SectorsPerCluster div ecx ; edx = remainder push edx ; save remainder
call ComputeLcn ; eax = LCN to read, ecx = remaining run length
movzx ebx, SectorsPerCluster mul ebx ; eax = LBN of cluster, edx = 0 pop edx ; edx = remainder add eax, edx ; eax = LBN we want push eax ; save LBN
movzx eax, SectorsPerCluster mul ecx ; eax = remaining run length in sectors, edx = 0 mov edx, eax ; edx = remaining run length
pop eax ; eax = LBN pop ecx ; ecx = remaining sectors in request
pop es pop edi pop ecx
; eax == LBN to read; ecx == remaining sectors to read; edx == remaining sectors in current run; es:edi == Target of read; TOS == Current VCN; TOS + 4 == pointer to attribute; cmp ecx, edx jge ReadIBS_30
; Run length is greater than remaining request; only read; remaining request.; mov edx, ecx ; edx = Remaining request
ReadIBS_30:; eax == LBN to read; ecx == remaining sectors to read; edx == sectors to read in current run; es:edi == Target of read; TOS == Current VCN; TOS + == pointer to attribute;
mov SectorBase, eax mov SectorCount, dx
; We have a pointer to the target buffer in es:edi, but we want that; in es:bx for ReadSectors.;
SAVE_ALL
mov bx, di and bx, 0Fh mov ax, es shr edi, 4 add ax, di ; ax:bx -> target buffer
push ax pop es ; es:bx -> target buffer
call ReadSectors
RESTORE_ALL
sub ecx, edx ; Decrement sectors remaining in request mov ebx, edx ; ebx = sectors read
mov eax, edx ; eax = sectors read movzx edx, BytesPerSector mul edx ; eax = bytes read (wipes out edx!)
add edi, eax ; Update target of read
pop eax ; eax = previous VBN add eax, ebx ; update VBN to read
pop ebx ; ebx -> attribute jmp ReadIBS_10
ReadIndexBlockSectors endp
;****************************************************************************;; MultiSectorFixup - fixup a structure read off the disk; to reflect Update Sequence Array.;; ENTRY: ES:EDI = Target buffer;; USES: none (preserves all registers with SAVE_ALL/RESTORE_ALL);; Note: ES:EDI must point at a structure which is protected; by an update sequence array, and which begins with; a multi-sector-header structure.;MultiSectorFixup proc near
SAVE_ALL
movzx ebx, es:[edi].MSH_UpdateArrayOfs ; ebx = update array offset movzx ecx, es:[edi].MSH_UpdateArraySize ; ecx = update array size
or ecx, ecx ; if the size of the update sequence array
jz BootErr$he ; is zero, this structure is corrupt.
add ebx, edi ; es:ebx -> update sequence array count word add ebx, 2 ; es:ebx -> 1st entry of update array
add edi, SEQUENCE_NUMBER_STRIDE - 2 ; es:edi->last word of first chunk dec ecx ; decrement to reflect count word
MSF10:
; ecx = number of entries remaining in update sequence array; es:ebx -> next entry in update sequence array; es:edi -> next target word for update sequence array
or ecx, ecx jz MSF30
mov ax, word ptr es:[ebx] ; copy next update sequence array entry mov word ptr es:[edi], ax ; to next target word
add ebx, 2 ; go on to next entry add edi, SEQUENCE_NUMBER_STRIDE ; go on to next target
dec ecx
jmp MSF10
MSF30:
RESTORE_ALL
ret
MultiSectorFixup endp
;****************************************************************************;; SetupMft - Reads MFT File Record Segments into the LBN array;; ENTRY: none.;; EXIT: NextBuffer is set to the free byte after the last MFT FRS; SegmentsInMft is initialized;;SetupMft proc near
SAVE_ALL
; Initialize SegmentsInMft and NextBuffer as if the MFT; had only one FRS.; mov eax, 1 mov SegmentsInMft, eax
mov eax, MftFrs ; this is the scratch mft buffer add eax, BytesPerFrs mov MftLcnFrs,eax ; this is the scratch mft buffer for lookup add eax, BytesPerFrs mov NextBuffer, eax
; Read FRS 0 into the first MFT FRS buffer, being sure; to resolve the Update Sequence Array. Remember the physical; location in the Lbn array.;
mov eax, MftStartLcn.LowPart movzx ebx, SectorsPerCluster mul ebx ; eax = mft starting sector
mov ebx, NextBuffer ; Store this location in the Lbn array mov [bx], eax mov SectorBase, eax ; SectorBase = mft starting sector for read add bx, 4 mov eax, SectorsPerFrs mov [bx], eax ; Store the sector count in the Lcn array mov SectorCount, ax ; SectorCount = SectorsPerFrs add bx, 4 mov NextBuffer, ebx ; Remember the next Lbn array location
mov ebx, MftFrs ; Read the sectors into the MftFrs scratch buffer
push ds pop es
call ReadSectors mov edi, ebx ; es:edi = buffer
call MultiSectorFixup
; Determine whether the MFT has an Attribute List attribute
mov eax, MftFrs mov ebx, $ATTRIBUTE_LIST mov ecx, 0 mov edx, 0
call LocateAttributeRecord
or eax, eax ; If there's no Attribute list, jz SetupMft99 ; we're done!
; Read the attribute list.; eax -> attribute list attribute; mov ebx, eax ; ebx -> attribute list attribute push ds pop es ; copy ds into es mov edi, AttrList ; ds:edi->attribute list buffer
call ReadWholeAttribute
mov ebx, AttrList ; ebx -> first attribute list entry
; Now, traverse the attribute list looking for the first; entry for the $DATA type. We know it must have at least; one.;; ebx -> first attribute list entry;
SetupMft10: cmp [bx].ATTRLIST_TypeCode, $DATA je SetupMft30
add bx,[bx].ATTRLIST_Length jmp SetupMft10
SetupMft20:; Scan forward through the attribute list entries for the; $DATA attribute, reading each referenced FRS. Note that; there will be at least one non-$DATA entry after the entries; for the $DATA attribute, since there's a $BITMAP.;; ebx -> Next attribute list entry; NextBuffer -> Target for next mapping information; MftFrs -> Target of next read; SegmentsInMft == number of MFT segments read so far;
; Find the physical sector and sector count for the runs for this; file record (max 2 runs). The mapping for this must already; be in a file record already visited. Find the Vcn and cluster; offset for this FRS. Use LookupMftLcn to find the Lcn.
push ebx ; Save the current position in the attribute list
; Convert from Frs to sectors, then to Vcn
mov eax, [bx].ATTRLIST_SegmentReference.REF_LowPart mul SectorsPerFrs push eax ; Remember the VBN xor edx, edx movzx ebx, SectorsPerCluster div ebx ; eax = VCN push edx ; save remainder, this is cluster offset
call ComputeMftLcn ; eax = LCN
or eax, eax ; LCN equal to zero?
jz BootErr$he ; zero is not a possible LCN
mov ecx, SectorsPerFrs ; ecx = Number of sectors remaining for this file record
; Change the LCN back into an LBN and add the remainder back in to get; the sector we want to read.
movzx ebx, SectorsPerCluster mul ebx ; eax = cluster first LBN pop edx ; edx = sector remainder add eax, edx ; eax = desired LBN
; Store this in the current Lcn array slot
mov ebx, NextBuffer mov [bx], eax ; Store the starting sector add bx, 4 movzx eax, SectorsPerCluster sub eax, edx
cmp eax, ecx ; Check if we have too many sectors jbe SetupMft60 mov eax, ecx ; Limit ourselves to the sectors remainingSetupMft60: mov [bx], eax ; Store the sector count
; If we have a complete file record skip to process the attribute entry
SetupMft70: sub ecx, eax ; Subtract these sectors from remaining sectors pop edx ; Get the previous starting VBN (restores stack also)
jz SetupMft50
; This may be a split file record. Go ahead and get the next piece.
add eax, edx ; Add the sector count for the last run to the start Vbn for the run ; This is the next Vbn to read push eax ; Save the Vbn
xor edx, edx ; Convert to Vcn, there should be no remainder this time movzx ebx, SectorsPerCluster div ebx ; eax = VCN
push ecx ; Save the remaining sectors call ComputeMftLcn ; eax = LCN pop ecx ; Restore the remaining sectors
or eax, eax ; LCN equal to zero? jz BootErr$he ; zero is not a possible LCN
; Change the LCN back into a LBN to get the starting sector we want to read.
movzx ebx, SectorsPerCluster mul ebx ; eax = cluster first LBN
; If this sector is the contiguous with the other half of the run; make it appear to be single longer run.
mov ebx, NextBuffer ; Recover the last run mov edx, [bx] add bx, 4 add edx, [bx] ; This is the next potential LBN
cmp edx, eax ; Check if we are at the contiguous LBN jne SetupMft80
; Append this to the previous run.
movzx eax, SectorsPerCluster cmp eax, ecx ; Check if have more sectors than we need jbe SetupMft90 mov eax, ecxSetupMft90:
add [bx], eax jmp SetupMft70 ; Loop to see if there more work to do
; This is multiple runs. Update the next entry.
SetupMft80: add bx, 4 mov NextBuffer, ebx ; advance our NextBuffer pointer
mov [bx], eax ; fill in the next run start sector add bx, 4
movzx eax, SectorsPerCluster cmp eax, ecx ; Check if have more sectors than we need jbe SetupMft100 mov eax, ecxSetupMft100: mov [bx], eax ; and count jmp SetupMft70 ; Loop to see if there is more work to do
SetupMft50:
; Advance the count of Frs segments and the NextBuffer pointer
add bx, 4 inc SegmentsInMft mov NextBuffer, ebx
pop ebx
; Go on to the next attribute list entry
SetupMft30: add bx,[bx].ATTRLIST_Length cmp [bx].ATTRLIST_TypeCode, $DATA je SetupMft20
SetupMft99:
RESTORE_ALL ret
SetupMft endp
;****************************************************************************;; ComputeMftLcn -- Computes the LCN for a cluster of the MFT;;; ENTRY: EAX == VCN;; EXIT: EAX == LCN;; USES: ALL;ComputeMftLcn proc near
mov edx, eax ; edx = VCN
mov ecx, SegmentsInMft ; ecx = # of FRS's to search
mov esi,MftLcnFrs add esi,BytesPerFrs ; si -> FRS LBN list
MftLcn10:; ECX == number of remaining FRS's to search; EDX == VCN; EBX == Buffer to read into; ESI == LBN array; EDI == Number of sectors to read; push edx ; save VCN push ecx ; save MFT segment count push edx ; save VCN again
; Read the sectors for the given FRS
mov ebx,MftLcnFrs mov edi,SectorsPerFrs
; Read these sectors
MftLcn40: mov eax,[si] ; Get the start sector and sector count mov SectorBase,eax add si,4 mov eax,[si] mov SectorCount,ax add si,4
push ds pop es
call ReadSectors
; Check if we have more data to read
sub edi, eax je MftLcn30
; Read the next run
mul BytesPerSector ; move forward in the buffer, results in ax:dx add bx,ax jmp MftLcn40
MftLcn30:
; Do the multi sector fixup
mov edi,MftLcnFrs push ds pop es
call MultiSectorFixup
mov eax, MftLcnFrs mov ebx, $DATA mov ecx, 0 mov edx, ecx
call LocateAttributeRecord
; EAX -> $DATA attribute; TOS == VCN; TOS + 4 == number of remaining FRS's to search; TOS + 8 -> FRS being searched; TOS +12 == VCN
or eax, eax
jz BootErr$he ; No $DATA attribute in this FRS!
mov ebx, eax ; ebx -> attribute pop eax ; eax = VCN
; EAX == VCN; EBX -> $DATA attribute; TOS number of remaining FRS's to search; TOS + 4 == FRS being searched; TOS + 8 == VCN
push esi call ComputeLcn pop esi
or eax, eax jz MftLcn20
; Found our LCN. Clean up the stack and return.;; EAX == LCN; TOS number of remaining FRS's to search; TOS + 4 == FRS being searched; TOS + 8 == VCN; pop ebx pop ebx ; clean up the stack
ret
MftLcn20:;; Didn't find the VCN in this FRS; try the next one.;; TOS number of remaining FRS's to search; TOS + 4 -> FRS being searched; TOS + 8 == VCN; pop ecx ; ecx = number of FRS's remaining, including current pop edx ; edx = VCN
loop MftLcn10 ; decrement cx and try next FRS
; This VCN was not found.; xor eax, eax ret
ComputeMftLcn endp
;****************************************************************************;; ReadMftSectors - Read sectors from the MFT;; ENTRY: EAX == starting VBN; ECX == number of sectors to read; ES:EDI == Target buffer;; USES: none (preserves all registers with SAVE_ALL/RESTORE_ALL);ReadMftSectors proc near
SAVE_ALL
RMS$Again:
push eax ; save starting VBN push ecx ; save sector count
; Divide the VBN by SectorsPerCluster to get the VCN
xor edx, edx ; zero high part of dividend movzx ebx, SectorsPerCluster div ebx ; eax = VCN push edx ; save remainder push edi ; save the target buffer
call ComputeMftLcn ; eax = LCN pop edi ; recover the buffer
or eax, eax ; LCN equal to zero?
jz BootErr$he ; zero is not a possible LCN
; Change the LCN back into a LBN and add the remainder back in to get; the sector we want to read, which goes into SectorBase.;
movzx ebx, SectorsPerCluster mul ebx ; eax = cluster first LBN pop edx ; edx = sector remainder add eax, edx ; eax = desired LBN
mov SectorBase, eax
;; Figure out how many sectors to read this time; we never attempt; to read more than one cluster at a time.;
pop ecx ; ecx = sectors to read
movzx ebx, SectorsPerCluster cmp ecx,ebx jle RMS10
;; Read only a single cluster at a time, to avoid problems with fragmented; runs in the mft.;
mov SectorCount, bx ; this time read 1 cluster sub ecx, ebx ; ecx = sectors remaining to read
pop eax ; eax = VBN add eax, ebx ; VBN += sectors this read
push eax ; save next VBN push ecx ; save remaining sector count
jmp RMS20
RMS10:
pop eax ; eax = VBN add eax, ecx ; VBN += sectors this read push eax ; save next VBN
mov SectorCount, cx mov ecx, 0 push ecx ; save remaining sector count (0)
RMS20:
; The target buffer was passed in es:edi, but we want it in es:bx.; Do the conversion.;
push es ; save buffer pointer push edi
mov bx, di and bx, 0Fh mov ax, es shr edi, 4 add ax, di ; ax:bx -> target buffer
push ax pop es ; es:bx -> target buffer
call ReadSectors
pop edi ; restore buffer pointer pop es
add edi, BytesPerCluster ; increment buf ptr by one cluster
pop ecx ; restore remaining sector count pop eax ; restore starting VBN
cmp ecx, 0 ; are we done? jg RMS$Again ; repeat until desired == 0
RESTORE_ALL ret
ReadMftSectors endp
;****************************************************************************;; ReadFrs - Read an FRS;; ENTRY: EAX == FRS number; ES:EDI == Target buffer;; USES: none (preserves all registers with SAVE_ALL/RESTORE_ALL);ReadFrs proc near
SAVE_ALL
mul SectorsPerFrs ; eax = sector number in MFT DATA attribute ; (note that mul wipes out edx!)
mov ecx, SectorsPerFrs ; number of sectors to read
call ReadMftSectors call MultiSectorFixup
RESTORE_ALL ret
ReadFrs endp
;****************************************************************************;; ReadIndexBlock - read an index block from the root index.;; ENTRY: EAX == Block number;; USES: none (preserves all registers with SAVE_ALL/RESTORE_ALL);ReadIndexBlock proc near
SAVE_ALL
mul SectorsPerIndexBlock ; eax = first VBN to read ; (note that mul wipes out edx!) mov ebx, IndexAllocation ; ebx -> $INDEX_ALLOCATION attribute mov ecx, SectorsPerIndexBlock ; ecx == Sectors to read
push ds pop es mov edi, IndexBlockBuffer ; es:edi -> index block buffer
call ReadIndexBlockSectors
call MultiSectorFixup
RESTORE_ALL ret
ReadIndexBlock endp
;****************************************************************************;; IsBlockInUse - Checks the index bitmap to see if an index; allocation block is in use.;; ENTRY: EAX == block number;; EXIT: Carry flag clear if block is in use; Carry flag set if block is not in use.;IsBlockInUse proc near
push eax push ebx push ecx
mov ebx, IndexBitmapBuffer
mov ecx, eax ; ecx = block number shr eax, 3 ; eax = byte number and ecx, 7 ; ecx = bit number in byte
add ebx, eax ; ebx -> byte to test
mov eax, 1 shl eax, cl ; eax = mask
test byte ptr[ebx], al
jz IBU10
clc ; Block is not in use. jmp IBU20
IBU10: stc ; Block is in use.
IBU20: pop ecx pop ebx pop eax ; restore registers
ret
IsBlockInUse endp
;****************************************************************************;; ComputeLcn - Converts a VCN into an LCN;; ENTRY: EAX -> VCN; EBX -> Attribute;; EXIT: EAX -> LCN (zero indicates not found); ECX -> Remaining run length;; USES: ALL.;ComputeLcn proc near
cmp [ebx].ATTR_FormCode, NONRESIDENT_FORM je clcn10
sub eax, eax ; This is a resident attribute. ret
clcn10: lea esi, [ebx].ATTR_FormUnion ; esi -> nonresident info of attrib
; eax -> VCN; ebx -> Attribute; esi -> Nonresident information of attribute record;; See if the desired VCN is in range.
mov edx, [esi].NONRES_HighestVcn.LowPart ; edx = HighestVcn cmp eax, edx ja clcn15 ; VCN is greater than HighestVcn
mov edx, [esi].NONRES_LowestVcn.LowPart ; edx = LowestVcn cmp eax, edx jae clcn20
clcn15: sub eax, eax ; VCN is not in range ret
clcn20:; eax -> VCN; ebx -> Attribute; esi -> Nonresident information of attribute record; edx -> LowestVcn; add bx, [esi].NONRES_MappingPairOffset ; ebx -> mapping pairs sub esi, esi ; esi = 0
clcn30:; eax == VCN to find; ebx -> Current mapping pair count byte; edx == Current VCN; esi == Current LCN; cmp byte ptr[ebx], 0 ; if count byte is zero... je clcn99 ; ... we're done (and didn't find it)
; Update CurrentLcn; call LcnFromMappingPair add esi, ecx ; esi = current lcn for this mapping pair
call VcnFromMappingPair
; eax == VCN to find; ebx -> Current mapping pair count byte; ecx == DeltaVcn for current mapping pair; edx == Current VCN; esi == Current LCN; add ecx, edx ; ecx = NextVcn
cmp eax, ecx ; If target < NextVcn ... jl clcn80 ; ... we found the right mapping pair.
; Go on to next mapping pair.; mov edx, ecx ; CurrentVcn = NextVcn
push eax
movzx ecx, byte ptr[ebx] ; ecx = count byte mov eax, ecx ; eax = count byte and eax, 0fh ; eax = number of vcn bytes shr ecx, 4 ; ecx = number of lcn bytes
add ebx, ecx add ebx, eax inc ebx ; ebx -> next count byte
pop eax jmp clcn30
clcn80:; We found the mapping pair we want.;; eax == target VCN; ebx -> mapping pair count byte; edx == Starting VCN of run; ecx == Next VCN (ie. start of next run); esi == starting LCN of run; sub ecx, eax ; ecx = remaining run length sub eax, edx ; eax = offset into run add eax, esi ; eax = LCN to return
ret
; The target VCN is not in this attribute.
clcn99: sub eax, eax ; Not found. ret
ComputeLcn endp
;****************************************************************************;; VcnFromMappingPair;; ENTRY: EBX -> Mapping Pair count byte;; EXIT: ECX == DeltaVcn from mapping pair;; USES: ECX;VcnFromMappingPair proc near
sub ecx, ecx ; ecx = 0 mov cl, byte ptr[ebx] ; ecx = count byte and cl, 0fh ; ecx = v
cmp ecx, 0 ; if ecx is zero, volume is corrupt. jne VFMP5
sub ecx, ecx ret
VFMP5: push ebx push edx
add ebx, ecx ; ebx -> last byte of compressed vcn
movsx edx, byte ptr[ebx] dec ecx dec ebx
; ebx -> Next byte to add in; ecx == Number of bytes remaining; edx == Accumulated value;VFMP10: cmp ecx, 0 ; When ecx == 0, we're done. je VFMP20
shl edx, 8 mov dl, byte ptr[ebx]
dec ebx ; Back up through bytes to process. dec ecx ; One less byte to process.
jmp VFMP10
VFMP20:; edx == Accumulated value to return
mov ecx, edx
pop edx pop ebx
ret
VcnFromMappingPair endp
;****************************************************************************;; LcnFromMappingPair;; ENTRY: EBX -> Mapping Pair count byte;; EXIT: ECX == DeltaLcn from mapping pair;; USES: ECX;LcnFromMappingPair proc near
push ebx push edx
sub edx, edx ; edx = 0 mov dl, byte ptr[ebx] ; edx = count byte and edx, 0fh ; edx = v
sub ecx, ecx ; ecx = 0 mov cl, byte ptr[ebx] ; ecx = count byte shr cl, 4 ; ecx = l
cmp ecx, 0 ; if ecx is zero, volume is corrupt. jne LFMP5
sub ecx, ecx
pop edx pop ebx ret
LFMP5:; ebx -> count byte; ecx == l; edx == v;
add ebx, edx ; ebx -> last byte of compressed vcn add ebx, ecx ; ebx -> last byte of compressed lcn
movsx edx, byte ptr[ebx] dec ecx dec ebx
; ebx -> Next byte to add in; ecx == Number of bytes remaining; edx == Accumulated value;LFMP10: cmp ecx, 0 ; When ecx == 0, we're done. je LFMP20
shl edx, 8 mov dl, byte ptr[ebx]
dec ebx ; Back up through bytes to process. dec ecx ; One less byte to process.
jmp LFMP10
LFMP20:; edx == Accumulated value to return
mov ecx, edx
pop edx pop ebx
ret
LcnFromMappingPair endp
;****************************************************************************;; UpcaseName - Converts the name of the file to all upper-case;; ENTRY: ESI -> Name; ECX -> Length of name;; USES: none;UpcaseName proc near
or ecx, ecx jnz UN5
ret
UN5: push ecx push esi
UN10: cmp word ptr[esi], 'a' ; if it's less than 'a' jl UN20 ; leave it alone
cmp word ptr[esi], 'z' ; if it's greater than 'z' jg UN20 ; leave it alone.
sub word ptr[esi], 'a'-'A' ; the letter is lower-case--convert it.UN20: add esi, 2 ; move on to next unicode character loop UN10
pop esi pop ecx
retUpcaseName endp
;****************************************************************************;; FindFile - Locates the index entry for a file in the root index.;; ENTRY: EAX -> name to find; ECX == length of file name in characters;; EXIT: EAX -> Index Entry. NULL to indicate failure.;; USES: ALL;FindFile proc near
push eax ; name address push ecx ; name length
; First, search the index root.;; eax -> name to find; ecx == name length; TOS == name length; TOS+4 -> name to find; mov edx, eax ; edx -> name to find mov eax, IndexRoot ; eax -> &INDEX_ROOT attribute lea ebx, [eax].ATTR_FormUnion ; ebx -> resident info add ax, [ebx].RES_ValueOffset ; eax -> Index Root value
lea eax, [eax].IR_IndexHeader ; eax -> Index Header
mov ebx, edx ; ebx -> name to find
call LocateIndexEntry
or eax, eax jz FindFile20
; Found it in the root! The result is already in eax.; Clean up the stack and return.; pop ecx pop ecx ret
FindFile20:;; We didn't find the index entry we want in the root, so we have to; crawl through the index allocation buffers.;; TOS == name length; TOS+4 -> name to find; mov eax, IndexAllocation or eax, eax jnz FindFile30
; There is no index allocation attribute; clean up; the stack and return failure.; pop ecx pop ecx xor eax, eax ret
FindFile30:;; Search the index allocation blocks for the name we want.; Instead of searching in tree order, we'll just start with; the last one and work our way backwards.;; TOS == name length; TOS+4 -> name to find; mov edx, IndexAllocation ; edx -> index allocation attr. lea edx, [edx].ATTR_FormUnion ; edx -> nonresident form info mov eax, [edx].NONRES_HighestVcn.LowPart; eax = HighestVcn inc eax ; eax = clusters in attribute
mov ebx, BytesPerCluster mul ebx ; eax = bytes in attribute
xor edx, edx div BytesPerIndexBlock ; convert bytes to index blocks
push eax ; number of blocks to process
FindFile40:;; TOS == remaining index blocks to search; TOS + 4 == name length; TOS + 8 -> name to find; pop eax ; eax == number of remaining blocks
or eax, eax jz FindFile90
dec eax ; eax == number of next block to process ; and number of remaining blocks
push eax
; eax == block number to process; TOS == remaining index blocks to search; TOS + 4 == name length; TOS + 8 -> name to find;; See if the block is in use; if not, go on to next.
call IsBlockInUse jc FindFile40 ; c set if not in use
; eax == block number to process; TOS == remaining index blocks to search; TOS + 4 == name length; TOS + 8 -> name to find;
call ReadIndexBlock
pop edx ; edx == remaining buffers to search pop ecx ; ecx == name length pop ebx ; ebx -> name
push ebx push ecx push edx
; ebx -> name to find; ecx == name length in characters; TOS == remaining blocks to process; TOS + 4 == name length; TOS + 8 -> name;; Index buffer to search is in index allocation block buffer.; mov eax, IndexBlockBuffer ; eax -> Index allocation block lea eax, [eax].IB_IndexHeader ; eax -> Index Header
call LocateIndexEntry ; eax -> found entry
or eax, eax jz FindFile40
; Found it!;; eax -> Found entry; TOS == remaining blocks to process; TOS + 4 == name length; TOS + 8 -> name; pop ecx pop ecx pop ecx ; clean up stack ret
FindFile90:;; Name not found.;; TOS == name length; TOS + 4 -> name to find; pop ecx pop ecx ; clean up stack. xor eax, eax ; zero out eax. ret
FindFile endp
ifdef DEBUG;****************************************************************************;; DumpIndexBlock - dumps the index block buffer;DumpIndexBlock proc near
SAVE_ALL
mov esi, IndexBlockBuffer
mov ecx, 20h ; dwords to dump
DIB10:
test ecx, 3 jnz DIB20 call DebugNewLine
DIB20:
lodsd call PrintNumber loop DIB10
RESTORE_ALL ret
DumpIndexBlock endp
;****************************************************************************;; DebugNewLine;DebugNewLine proc near
SAVE_ALL
xor eax, eax xor ebx, ebx
mov al, 0dh mov ah, 14 mov bx, 7 int 10h
mov al, 0ah mov ah, 14 mov bx, 7 int 10h
RESTORE_ALL ret
DebugNewLine endp
;****************************************************************************;; PrintName - Display a unicode name;; ENTRY: DS:ESI -> null-terminated string; ECX == characters in string;; USES: None.;PrintName proc near
SAVE_ALL
or ecx, ecx jnz PrintName10
call DebugNewLine
RESTORE_ALL
ret
PrintName10:
xor eax, eax xor ebx, ebx
lodsw
mov ah, 14 ; write teletype mov bx, 7 ; attribute int 10h ; print it loop PrintName10
call DebugNewLine
RESTORE_ALL ret
PrintName endp
;****************************************************************************;; DebugPrint - Display a debug string.;; ENTRY: DS:SI -> null-terminated string;; USES: None.;.286DebugPrint proc near
pusha
DbgPr20:
lodsb cmp al, 0 je DbgPr30
mov ah, 14 ; write teletype mov bx, 7 ; attribute int 10h ; print it jmp DbgPr20
DbgPr30:
popa nop ret
DebugPrint endp
;****************************************************************************;;; PrintNumber;; ENTRY: EAX == number to print;; PRESERVES ALL REGISTERS;.386PrintNumber proc near
SAVE_ALL
mov ecx, 8 ; number of digits in a DWORD
PrintNumber10:
mov edx, eax and edx, 0fh ; edx = lowest-order digit push edx ; put it on the stack shr eax, 4 ; drop low-order digit loop PrintNumber10
mov ecx, 8 ; number of digits on stack.
PrintNumber20:
pop eax ; eax = next digit to print cmp eax, 9 jg PrintNumber22
add eax, '0' jmp PrintNumber25
PrintNumber22:
sub eax, 10 add eax, 'A'
PrintNumber25:
xor ebx, ebx
mov ah, 14 mov bx, 7 int 10h loop PrintNumber20
; Print a space to separate numbers
mov al, ' ' mov ah, 14 mov bx, 7 int 10h
RESTORE_ALL
call Pause
ret
PrintNumber endp
;****************************************************************************;; Debug0 - Print debug string 0 -- used for checkpoints in mainboot;Debug0 proc near
SAVE_ALL
mov si, offset DbgString0 call BootErr$Print1
RESTORE_ALL
ret
Debug0 endp
;****************************************************************************;; Debug1 - Print debug string 1 --;Debug1 proc near
SAVE_ALL
mov si, offset DbgString1 call BootErr$Print1
RESTORE_ALL
ret
Debug1 endp
;****************************************************************************;; Debug2 - Print debug string 2;Debug2 proc near
SAVE_ALL
mov si, offset DbgString2 call BootErr$Print1
RESTORE_ALL
ret
Debug2 endp
;****************************************************************************;; Debug3 - Print debug string 3 --;Debug3 proc near
SAVE_ALL
mov si, offset DbgString3 call BootErr$Print1
RESTORE_ALL
ret
Debug3 endp
;****************************************************************************;; Debug4 - Print debug string 4;Debug4 proc near
SAVE_ALL
mov si, offset DbgString4 call BootErr$Print1
RESTORE_ALL
ret
Debug4 endp
;****************************************************************************;; Pause - Pause for about 1/2 a second. Simply count until you overlap; to zero.;Pause proc near
push eax mov eax, 0fff10000h
PauseLoopy: inc eax
or eax, eax jnz PauseLoopy
pop eax ret
Pause endp
endif ; DEBUG
;*************************************************************************;; LoadIndexFrs - For the requested index type code locate and; load the associated Frs.;; ENTRY: EAX - requested index type code; ECX - Points to empty Frs buffer;; EXIT: EAX - points to offset in Frs buffer of requested index type; code or Zero if not found.; USES: All;LoadIndexFrs proc near
push ecx ; save FRS buffer for later push eax ; save index type code for later
mov eax, ROOT_FILE_NAME_INDEX_NUMBER push ds pop es mov edi, ecx ; es:edi = target buffer
call ReadFrs
mov eax, ecx ; FRS to search
pop ebx ; Attribute type code push ebx movzx ecx, index_name_length ; Attribute name length mov edx, offset index_name ; Attribute name
call LocateAttributeRecord
pop ebx pop ecx
or eax, eax jnz LoadIndexFrs$Exit ; if found in root return
;; if not found in current Frs, search in attribute list; ; EBX - holds Attribute type code mov eax, ecx ; FRS to search mov ecx, ebx ; type code push eax ; save Frs push ebx ; save type code
call SearchAttrList ; search attribute list for FRN ; of specified ($INDEX_ROOT, ; $INDEX_ALLOCATION, or $BITMAP)
; EAX - holds FRN for Frs, or Zero
pop ebx ; Attribute type code (used later) pop edi ; es:edi = target buffer
or eax, eax ; if we cann't find it in attribute jz LoadIndexFrs$Exit ; list then we are hosed
; We should now have the File Record Number where the index for the; specified type code we are searching for is, load this into the; Frs target buffer.;; EAX - holds FRN; EBX - holds type code; EDI - holds target buffer
push ds pop es
call ReadFrs
;; Now determine the offset in the Frs of the index;
; EBX - holds type code
mov eax, edi ; Frs to search movzx ecx, index_name_length ; Attribute name length mov edx, offset index_name ; Attribute name
call LocateAttributeRecord
; EAX - holds offset or Zero.
LoadIndexFrs$Exit: ret
LoadIndexFrs endp
;****************************************************************************;; SearchAttrList;; Search the Frs for the attribute list. Then search the attribute list; for the specifed type code. When you find it return the FRN in the; attribute list entry found or Zero if no match found.;; ENTRY: ECX - type code to search attrib list for; EAX - Frs buffer holding head of attribute list; EXIT: EAX - FRN file record number to load, Zero if none.;; USES: All;SearchAttrList proc near
push ecx ; type code to search for in ; attrib list
; EAX - holds Frs to search mov ebx, $ATTRIBUTE_LIST ; Attribute type code mov ecx, 0 ; Attribute name length mov edx, 0 ; Attribute name
call LocateAttributeRecord
or eax, eax ; If there's no Attribute list, jz SearchAttrList$NotFoundIndex1 ; We are done
; Read the attribute list.; eax -> attribute list attribute
mov ebx, eax ; ebx -> attribute list attribute push ds pop es ; copy ds into es mov edi, AttrList ; ds:edi->attribute list buffer
call ReadWholeAttribute
push ds pop es mov ebx, AttrList ; es:ebx -> first attribute list entry
; Now, traverse the attribute list looking for the entry for; the Index type code.;; ebx -> first attribute list entry;
pop ecx ; Get Index Type code
SearchAttrList$LookingForIndex:
ifdef DEBUG SAVE_ALL
mov eax, es:[bx].ATTRLIST_TypeCode call PrintNumber movzx eax, es:[bx].ATTRLIST_Length call PrintNumber mov eax, es call PrintNumber mov eax, ebx call PrintNumber push es pop ds movzx ecx, es:[bx].ATTRLIST_NameLength ; ecx = chars in name lea esi, es:[bx].ATTRLIST_Name ; esi -> name call PrintName
RESTORE_ALLendif ; DEBUG
cmp es:[bx].ATTRLIST_TypeCode, ecx je SearchAttrList$FoundIndex
cmp es:[bx].ATTRLIST_TypeCode, $END ; reached invalid attribute je SearchAttrList$NotFoundIndex2 ; so must be at end
cmp es:[bx].ATTRLIST_Length, 0 je SearchAttrList$NotFoundIndex2 ; reached end of list and ; nothing found movzx eax, es:[bx].ATTRLIST_Length add bx, ax
mov ax, bx and ax, 08000h ; test for roll over jz SearchAttrList$LookingForIndex
; If we rolled over then increment to the next es 32K segment and ; zero off the high bits of bx
mov ax, es add ax, 800h mov es, ax
and bx, 07fffh
jmp SearchAttrList$LookingForIndex
SearchAttrList$FoundIndex:
; found the index, return the FRN
mov eax, es:[bx].ATTRLIST_SegmentReference.REF_LowPart ret
SearchAttrList$NotFoundIndex1: pop ecxSearchAttrList$NotFoundIndex2: xor eax, eax ret
SearchAttrList endp
;; Boot message printing, relocated from sector 0 to sace space;BootErr$fnf: mov al,byte ptr TXT_MSG_SYSINIT_FILE_NOT_FD jmp BootErr2BootErr$ntc: mov al,byte ptr TXT_MSG_SYSINIT_NTLDR_CMPRS jmp BootErr2
ifdef DEBUGDbgString0 db "Debug Point 0", 0Dh, 0Ah, 0DbgString1 db "Debug Point 1", 0Dh, 0Ah, 0DbgString2 db "Debug Point 2", 0Dh, 0Ah, 0DbgString3 db "Debug Point 3", 0Dh, 0Ah, 0DbgString4 db "Debug Point 4", 0Dh, 0Ah, 0
endif ; DEBUG
.errnz ($-_ntfsboot) GT 8192 ; <FATAL PROBLEM: main boot record exceeds available space>
org 8192
BootCode ends
end _ntfsboot
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