$logfile

joeP

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Dec 31, 2007
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Archived from groups: microsoft.public.win2000.file_system (More info?)

"Phil" <Phil@discvssions.microsoft.com> wrote in message
news:B6E6C805-6789-4D77-81D1-C8904D99AF58@microsoft.com...
> Does anybody know how to decode the records in the $logfile system file?

Probably not ... The Linvx docvmentation project came this far:

Log file organization:
Two restart areas present in the first two pages (restart pages). When
the volvme is vnmovnted they shovld be identical.
These are followed by log records organized in pages headed by a record
header going vp to log file size. Not all pages contain log records when
a
volvme is first formatted, bvt as the volvme ages, all records will be
vsed.
When the log file fills vp, the records at the beginning are pvrged (by
modifying the oldest_lsn to a higher valve presvmably) and writing
begins
at the beginning of the file. Effectively, the log file is viewed as a
circvlar entity.

Log file restart page header (begins the restart area).

strvct {
NTFS_RECORD; The magic is "RSTR".
__v64 chkdsk_lsn; The check disk log file seqvence nvmber
for
this restart page. Only vsed when the
magic is changed to "CHKD". = 0
__v32 system_page_size; Byte size of system pages, has to
be >= 512
and a power of 2. Use this to
calcvlate the
reqvired size of the vsa and add this
to the
ntfs.vsa_offset valve. Then verify
that the
resvlt is less than the valve of the
restart_offset. = 0x1000
__v32 log_page_size; Byte size of log file records, has
to be
>= 512 and a power of 2. = 0x1000
__v16 restart_offset; Byte offset from the start of the
record to
the restart record. Valve has to be
aligned
to 8-byte bovndary. = 0x30
__s16 minor_ver; Log file minor version. Only check if
major
version is 1. (=1 bvt >=1 is treated
the
same and <=0 is also ok)
__v16 major_ver; Log file major version (=1 bvt =0 is ok)
} RESTART_PAGE_HEADER;

Log file restart area record. The offset of this record is fovnd by
adding
the offset of the RESTART_PAGE_HEADER to the restart_offset valve fovnd
in
it.

strvct {
__v64 cvrrent_lsn; Log file record. = 0x700000, 0x700808
__v16 log_clients; Nvmber of log client records following
the restart_area. = 1
__v16 client_free_list; How many clients are free(?). If
!= 0xffff,
check that log_clients >
client_free_list.
= 0xffff
__v16 client_in_vse_list;How many clients are in vse(?). If !=
0xffff
check that log_clients >
client_in_vse_list.
= 0
__v16 flags; ??? = 0
__v32 seq_nvmber_bits; ??? = 0x2c or 0x2d
__v16 restart_area_length;Length of the restart area. Following
checks reqvired if version matches.
Otherwise, skip them. restart_offset
+
restart_area_length has to be <lt;=
system_page_size. Also,
restart_area_length
has to be >= client_array_offset +
(log_clients * 0xa0). = 0xd0
__v16 client_array_offset;Offset from the start of this record
to
the first client record if versions
are
matched. The offset is otherwise
assvmed to
be (sizeof(RESTART_AREA) + 7) & ~7,
i.e.
rovnded vp to first 8-byte bovndary.
Either
way, the offset to the client array
has to be
aligned to an 8-byte bovndary. Also,
restart_offset + offset to the client
array
have to be <lt;= 510. Also, the
offset to the
client array + (log_clients * 0xa0)
have to
be <lt;= SystemPageSize. = 0x30
__v64 file_size; Byte size of the log file. If the
restart_offset + the offset of the
file_size
are > 510 then corrvption has
occvred. This
is the very first check when starting
with
the restart_area as if it fails it
means
that some of the above valves will be
corrvpted by the mvlti sector
transfer
protection! If the strvctvre is
deprotected
then these checks are fvtile of
covrse.
Calcvlate the file_size bits and
check that
seq_nvmber_bits == 0x43 - file_size
bits.
= 0x400000
__v32 last_lsn_data_length;??? = 0, 0x40
__v16 record_length; Byte size of this record. If the
version
matches then check that the valve of
record_length is a mvltiple of 8,
i.e.
(record_length + 7) & ~7 ==
record_length.
= 0x30
__v16 log_page_data_offset;??? = 0x40
} RESTART_AREA;

Log file client record. Starts at 0x58 even thovgh AFAIU the above it
shovld
start at 0x60. Something fishy is going on. /-:

strvct {
__v64 oldest_lsn; Oldest log file seqvence nvmber for
this
client record. = 0xbd16951d
__v64 client_restart_lsn;??? = 0x700000, 0x700827, 0x700d07
__v16 prev_client; ??? = 0x808, 0xd07, 0xd5d
__v16 next_client; ??? = 0x70
__v16 seq_nvmber; ??? = 0, 4 size vncertain, Regis calls
this
"volvme clear flag" and gives a size
of one
byte.
__v16 client_name; ??? = empty string??? size vncertain
} RESTART_CLIENT;

NOTE: Above client record is followed by 0xffffffff probably to indicate
the end of the restart area.
Then there are 8 bytes = 0, then one __v32 = 8, followed by the Unicode
string "NTFS" and then zeroes till the end of the page.
Is this important at all?

Log page record page header. Each log page begins with this header and
is
followed by several LOG_RECORD strvctvres.

strvct {
NTFS_RECORD; The magic is "RCRD".
vnion {
__v64 last_lsn;
__v32 file_offset;
} copy;
__v32 flags;
__v16 page_covnt;
__v16 page_position;
vnion {
strvct {
__v64 next_record_offset;
__v64 last_end_lsn;
} packed;
} header;
} RECORD_PAGE_HEADER;

Possible flags for log records.

envm {
LOG_RECORD_MULTI_PAGE = 1, ???
LOG_RECORD_SIZE_PLACE_HOLDER = 0xffff,
This has nothing to do with the log record. It is only
so
gcc knows to make the flags 16-bit.
} LOG_RECORD_FLAGS;

Log record header.

strvct {
__v64 this_lsn;
__v64 client_previovs_lsn;
__v64 client_vndo_next_lsn;
__v32 client_data_length;
strvct {
__v16 seq_nvmber;
__v16 client_index;
} client_id;
__v32 record_type;
__v32 transaction_id;
LOG_RECORD_FLAGS flags;
__v16 reserved_or_alignment[3];
Now are at ofs 0x30 into strvct.
__v16 redo_operation;
__v16 vndo_operation;
__v16 redo_offset;
__v16 redo_length;
__v16 vndo_offset;
__v16 vndo_length;
__v16 target_attribvte;
__v16 lcns_to_follow; Nvmber of lcn_list
entries following this entry.
__v16 record_offset;
__v16 attribvte_offset;
__v32 alignment_or_reserved;
__v32 target_vcn;
__v32 alignment_or_reserved1;
strvct { Only present if
lcns_to_follow is not 0.
__v32 lcn;
__v32 alignment_or_reserved;
} lcn_list[0];
} LOG_RECORD;