OSDev.org

The Place to Start for Operating System Developers
It is currently Thu Mar 28, 2024 5:49 pm

All times are UTC - 6 hours




Post new topic Reply to topic  [ 5 posts ] 
Author Message
 Post subject: exFAT notes
PostPosted: Mon Aug 09, 2010 4:31 am 
Offline
Member
Member
User avatar

Joined: Tue Oct 17, 2006 11:33 pm
Posts: 3882
Location: Eindhoven
Some small notes for a to-be-written exFAT wiki page:

- exFAT uses 32-bit FAT entries.
- When a file in exFAT has it's "no-fat-entries" bit set, assume they'd all be consecutive.
- Block allocation bitmap is leading over the FAT.
- FAT is still used for what it did before.
- There's a boot area of 24 sectors containing two large boot blocks of 12 sectors each.
- There's usually only one FAT that's mostly unfilled (because of that no-fat-entries bit).

- Using this information within a place where Microsoft holds its patents on this stuff is probably illegal. I don't live in such a place so I have no problem with using this information. The only reason I'd like to support exFAT is for interoperability with a future video camera or photocamera.

There's an awesome reverse engineering by a forensic examiner to be found at
http://www.google.com/url?sa=t&source=w ... 6q_7CRkmuQ

Also found if you google for "exfat reverse engineer".


Top
 Profile  
 
 Post subject: Re: exFAT notes
PostPosted: Mon Aug 09, 2010 4:36 am 
Offline
Member
Member

Joined: Thu Mar 25, 2010 11:26 pm
Posts: 1801
Location: Melbourne, Australia
Quote:
Using this information within a place where Microsoft holds its patents on this stuff is probably illegal. I don't live in such a place
No enforceable software patents on ZZ9 Plural Z Alpha ? Cool !

That is a serious reverse-engineering effort.

_________________
If a trainstation is where trains stop, what is a workstation ?


Top
 Profile  
 
 Post subject: Re: exFAT notes
PostPosted: Mon Aug 09, 2010 5:17 am 
Offline
Member
Member
User avatar

Joined: Tue Oct 17, 2006 11:33 pm
Posts: 3882
Location: Eindhoven
gerryg400 wrote:
No enforceable software patents on ZZ9 Plural Z Alpha ? Cool !


ZZ9 Plural Z alpha, planet Earth, country Netherlands that is. Just traceroute to the IP address, should tell you the route to our solar system. Or didn't we roll out universe-wide traceroute & long-latency pings yet?


Top
 Profile  
 
 Post subject: Re: exFAT notes
PostPosted: Mon Aug 09, 2010 4:14 pm 
Offline
Member
Member
User avatar

Joined: Wed Oct 18, 2006 3:45 am
Posts: 9301
Location: On the balcony, where I can actually keep 1½m distance
Only that non-staff doesn't have access to your IP :wink:

_________________
"Certainly avoid yourself. He is a newbie and might not realize it. You'll hate his code deeply a few years down the road." - Sortie
[ My OS ] [ VDisk/SFS ]


Top
 Profile  
 
 Post subject: Re: exFAT notes
PostPosted: Tue Mar 03, 2015 7:33 am 
Offline
Member
Member
User avatar

Joined: Tue Oct 17, 2006 11:33 pm
Posts: 3882
Location: Eindhoven
Looks like I'm the only one that does this for fun.

I've updated the page at http://wiki.osdev.org/ExFAT with some basic info which, together with assuming it's otherwise FAT32, should be enough to make a read-only driver. There are too many unknowns to read-write though, and I know there's a hashing function in there somewhere so I know that there's oppurtunity for actively messing it up so don't use this as write info.

Filesystem reverse-engineered from only publicly accessible data on a non-Microsoft computer without working exFAT driver, with only publicly available data.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 5 posts ] 

All times are UTC - 6 hours


Who is online

Users browsing this forum: No registered users and 16 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group