On Monday 08 May 2017 23:18:11 Mario.Limonciello@dell.com wrote: > > -----Original Message----- > > From: Pali Rohár [mailto:pali.rohar@gmail.com] > > Sent: Monday, May 8, 2017 4:00 PM > > To: Limonciello, Mario > > Cc: dvhart@infradead.org; rjw@rjwysocki.net; luto@amacapital.net; > > len.brown@intel.com; corentin.chary@gmail.com; luto@kernel.org; > > andriy.shevchenko@linux.intel.com; linux-kernel@vger.kernel.org; > > platform- driver-x86@vger.kernel.org; linux-pm@vger.kernel.org > > Subject: Re: RFC: WMI Enhancements > > > > On Monday 08 May 2017 21:21:45 Mario.Limonciello@dell.com wrote: > > > > -----Original Message----- > > > > From: Pali Rohár [mailto:pali.rohar@gmail.com] > > > > Sent: Monday, May 8, 2017 12:18 PM > > > > To: Limonciello, Mario > > > > Cc: dvhart@infradead.org; rjw@rjwysocki.net; > > > > luto@amacapital.net; len.brown@intel.com; > > > > corentin.chary@gmail.com; luto@kernel.org; > > > > andriy.shevchenko@linux.intel.com; > > > > linux-kernel@vger.kernel.org; platform- > > > > driver-x86@vger.kernel.org; linux-pm@vger.kernel.org Subject: > > > > Re: RFC: WMI Enhancements > > > > > > > > On Friday 05 May 2017 23:55:46 Mario.Limonciello@dell.com wrote: > > > > > Unfortunately the MOF data that comes out of wmi-mof is so > > > > > called "Binary MOF" which has been pre-compiled to an > > > > > intermediate format with mofcomp.exe on Windows. The format > > > > > of binary MOF is not documented and the only known way to > > > > > get text mof back out is by using mofcomp.exe with some > > > > > esoteric arguments. > > > > > > > > > > mofcomp.exe -MOF:recovered.mof -MFL:ms_409.mof > > > > > -Amendment:MS_409 binary_mof_file > > > > > > > > Looks like that binary MOF file has "well-known" file extension > > > > .bmf. File itself starts with magic hader "FOMB" which is in > > > > reverse BMOF (binary mof). But I was not able to find any > > > > specification nor any other details. As this binary format is > > > > dated back to Win9x I guess data would compressed by some old > > > > MS compression algorithm (CAB?). > > > > > > Actually comparing a couple of binary MOF files the first 8 look > > > like the header to me. > > > > > > 0x46, 0x4f, 0x4d, 0x42, 0x01, 0x00, 0x00, 0x00 > > > > > > On a compiled Dell binary MOF the next are: > > > > > > 0xed, 0x04, 0x00, 0x00, > > > > > > This looks like the size of the remaining data after taking out > > > 16 for the headers 4ed = 1261 > > > Total size is 1277 > > > > > > 0xd8, 0x15, 0x00, 0x00 > > > Maybe a checksum? > > > > > > But that first 16 bytes does look like the header structure to > > > me. > > > > Good catch! Your observation for first 12 bytes passes also for my > > checks. > > > > Next 4 bytes (after possible checksum) at 0x10 are always same: > > 0x44 0x53 0x00 0x01. > > > > And I guess this should be compression header. In time of Win9x > > Microsoft had own non-standard compression for disks called > > DoubleSpace. IIRC it was some modification of LZ77 algorithm. And > > 0x44 0x53 0x00 0x01 is DS01. Maybe it is really DoubleSpace > > compression used for binary MOF? > > > > I'm going to find specification of that old compression > > algorithm... I found dmsdos implementation of that DS compression at: http://cmp.felk.cvut.cz/~pisa/dmsdos Then took relevant decompression code and it really decompressed that binary MOF WMI buffer. But still decompressed format is binary, but I now see all WMI GUID encoded in UTF-16. Decompressed BMF file has again "FOMB" magic header. I pushed my decompression utility here: https://github.com/pali/bmfdec So next step is to decode that decompressed binary MOF file. > 44 53 looks promising to be quantum compression. > https://en.wikipedia.org/wiki/Quantum_compression > > That’s also what 'file' magic detects from it too. > $ file mof.stripped > mof.stripped: Quantum archive data Hm... so that Quantum compression is also modification of LZ77. And probably it is same as DoubleSpace format (or use it). > > > > Moreover via tool wmiofck.exe it is possible to generate header > > > > file for > > > > > > > > WMI driver from binary mof file: > > > > wmiofck.exe -hfile.h -m -u file.bmf > > > > > > > > And what is interesting that in this file are also comments > > > > which looks like comes from that binary mof file. > > > > > > Ah interesting. The "comments" that come out of that are > > > actually what's mapped to the "Description" field in the WMI > > > repository when the binary MOF is loaded. > > > > > > They are not the developer comments that were placed in the > > > original MOF data. I would suppose those are lost when > > > compiling to binary MOF. > > > > Hm.. right they are present in decompiled MOF file in Description > > field. > > > > > > When I looked into output from mofcomp.exe with above args, > > > > that MOF output did not contain comments, so looks like we > > > > still can miss something. > > > > > > > > See: http://blog.nietrzeba.pl/2011/12/mof-decompilation.html > > > > > > Actually I see wmimofck output to be missing some important bits. > > > For example on a Dell system You'll get a class BFn declared from > > > mofcomp output, but nothing from wmimofck output. > > > > > > The most important thing that you're really getting out of this > > > MOF is the size, structure and format of the buffer that you > > > would be sending to ASL. > > > > > > Back to the point we were discussing of a potential filter, the > > > information in the MOF could possibly be very useful to declaring > > > what is going into the filter. > > > > In that header file generated by wmiofck.exe I see definitions for > > BFn. > > There is a definition but it's missing the format of the argument > from what I can tell. > > In any case, this will be tangential to this discussion, but useful > for reverse engineering the binary mof format. -- Pali Rohár pali.rohar@gmail.com