QuantumG's Blog

Recently, Greg K.H. made an offer to write free linux kernel drivers to any company that will provide him with docs to their hardware. Some BSD folks had a problem with Greg making this offer to people who would only give up their docs if the developer signed an NDA. Theo de Raadt chimed in declaring that "it is a fucking farce" , which is his usual way. As far as they are concerned, an open source driver without docs is not open at all. That may be so, but I still think having source code.. any source code.. which actually works, is better than having no docs or source code. It would be nice if companies would hand over docs without an NDA.. that is certainly preferable for everyone.. but some of them just won't, and getting them to hand over docs under an NDA with the ok for someone to write a free driver (be it GPL or BSD licensed) - that's something and it shouldn't be ignored. Now, if companies start doing this and drivers start showing up as GPL, but wi...

Argh. It's 2006, and I still don't have a good decompiler. All is not lost. Thankfully, there are still interesting things to decompile that are both small and contain lots of stuff that makes decompilation easy (e.g., symbols, relocations). So, let's do it manually using some trustworthy old fashioned tools: a disassembler, a text editor and some string processing tools. Let's choose a target. I'm going to go with a linux kernel module because they are small, contain symbols and relocations and because there exist GPL ones that I won't get in trouble for reverse engineering publicly. Just choosing something at random from /lib/modules on my Ubuntu linux box I come across new_wlan_acl.ko from the madwifi-ng drivers. Right, now we need a disassembly. No problem. Just do objdump -d --adjust-vma=0x8000000 new_wlan_acl.ko > out.dis . That almost gives me the object as it would look mapped into the linux kernel. Slight problem though, none of the reloca...

If you pop over to the NVIDIA web site and download the 3d card drivers for Linux, you'll note that there is a /usr/src/nv directory. In that directory is source code to the "thin layer" to the Linux kernel which NVIDIA links their binary blob. This, of course, makes no legal difference - NVIDIA are still extending the Linux kernel and therefore it is unlawful to distribute the Linux kernel along with the NVIDIA drivers, but NVIDIA doesn't do that, so it's not a problem - for them. Anyway, that's a side issue. I was thinking, recently, about the Linux kernel's "tainted" flag. Essentially, whenever you install a kernel module that isn't under some accepted open source license, the kernel sets a flag so that developers know there is a chance that any bugs you report might have been caused by code they can't fix. In general, this is not such a big deal as kernel modules are typically small and easy to isolate. The NVIDIA graphics driv...