Leaked source code of windows server 2003
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BREAK <MFT Definitions>
;** MSDOS MFT definitions;; The Master File Table (MFT) associates the cannonicalized pathnames, lock; records and SFTs for all files open on this machine.;; The MFT implementation employs a single memory buffer which is used from; both ends. This gives the effect (at least until they run into each; other) of two independent buffers.;; MFT buffer; ==========; The MFT buffer contains MFT name records and free space. It uses a; classic heap architecture: freed name records are marked free and; conglomerated with any adjacent free space. When one is to create a name; entry the free list is searched first-fit. The list of name and free; records is always terminated by a single END record.;; LOCK buffer; ===========; The lock buffer contains fixed format records containing record locking; information. Since they are fixed format the space is handled as a series; of chains: one for each MFT name record and one for the free list. No; garbage collection is necessary.;; Space allocation; ================; The MFT is managed as a heap. Empty blocks are allocated on a first-fit; basis. If there is no single large enough empty block the list is garbage; collected.;; MFT name records:;; 8 16 8 16 32 16 n; |------|-----|-----|------|------|------|---------~~~~~~---------|; | FLAG | LEN | SUM | LPTR | SPTR | SERL | <.asciz string> |; --------------------------------------------------~~~~~~----------;; FLAG = record type flag; LEN = total byte length of record.; SUM = sum of bytes in asciz string. Used to speed; searches; LPTR= pointer to first record in lock chain segment; is MFT segment; SPTR= pointer to first sft in sft chain; SERL= serial number; <string> = name string, zero-byte terminated. There; may be garbage bytes following the 00 byte;; these are counted in the LEN field.;;; MFT free records;; 8 16; |------|-----|----~~~~~~~~~~~~~~~~~~~~~~~~~~~---------|; | FLAG | LEN | free |; ------------------~~~~~~~~~~~~~~~~~~~~~~~~~~~----------;; FLAG = record type flag; LEN = total byte length of record.;;; MFT END records;; 8; |------|; | FLAG |; --------;; FLAG = record type flag
;** MFT definitions;*;* NOTE: the flag and length fields are identical for all record types;* (except the END type has no length) This must remain so as;* some code depends upon it.;*;* NOTE: Many routines check for "n-1" of the N flag values and if no;* match is found assume the flag value must be the remaining;* possibility. If you add or remove flag values you must check;* all references to mft_flag.
MFT_entry STRUC
mft_flag DB ? ; flag/len fieldmft_len DW ?mft_sum DB ? ; string sum wordmft_lptr DW ? ; LCK pointermft_sptr DD ? ; sft pointermft_serl DW ? ; serial numbermft_name DB ? ; offset to start of name
MFT_entry ENDS
MFLG_NAM EQU 1 ; min value for name recordMFLG_FRE EQU 0 ; free recordMFLG_END EQU -1 ; end record
;* Record Lock Record (RLR):;; 16 32 32 32; |-------|--------|--------|--------|; | NEXT | FBA | LBA | SPTR |; | | lo hi | lo hi | |; ------------|--------|--------------;; CHAIN = pointer to next RLR. 0 if end; FBA = offset of 1st byte of locked region; LBA = offset of last byte of locked region; SPTR = pointer to SFT lock was issued on
RLR_entry STRUC
rlr_next DW ? ; chain to next RLR, 0 if endrlr_fba DW ? ; first byte addr (offset) of reigion DW ?rlr_lba DW ? ; last byte addr of region DW ?rlr_sptr DD ? ; SFT pointerrlr_pid dw ? ; process id of issuerrlr_type dw ? ; lock typeRLR_entry ENDS
rlr_lall equ 00h ; lock all opsrlr_lwr equ 01h ; lock write ops
;; A pictorial diagram for the linkages is as follows:;; +---sptr------+; V |; +---+<----------|---sptr------+------------+; |SFT+----+ | | |; +-+-+ | +-+-+ +--+-+ +--+-+; V +--->|MFT+-lptr->-|LOCK+-next->|LOCK+->0; +---+ | +---+ +----+ +----+; |SFT+----+ ^; +-+-+ |; | |; +-------------+;;
;**;; Interesting behavior should be noted:;; The sharer must maintain information on files in three forms:;; local/remote handles. These are normal handles and behave in no; strange manner. They are identified by SF_mode not having the; sfIsFCB flag nor by having the sf_mode = 70. No problems with; locking. No problems with open. No problems with close.; CloseByName will iterate closes until the mft disappears.; CloseUser will iterate closes until no SFT for the particular user; appears. CloseProcess will iterate closes until no SFT for the; particular user/process appears.;; local FCBs. There are no corresponding SFT's for these as the SFTs; are cached but will be valid for the particular file. There is; one SFT for each open on a file by a specific process. These are; identified the sfIsFCB flag in the sf_mode field. When multiple; opens occur, we merely find the sf pertinent to the file and; process. Close decrements the ref count. CloseByName, CloseUser,; CloseProcess will iterate closes until no more SFTs exist.;; handles with mode 70. These represent FCB's open across the network.; As such, identical sfts may have been collapsed by the $open code.; This results in a reuse of the same SFT. The $Open code must; correctly set the ref-count for the sft to reflect the number of; collapses that have occurred. These are identified by a 70 in the; SF_mode field. There can be no locking on these SFTs. Open must; scan the list of SFTs for the file and increment its ref count; appropriately.
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