Linux® emulation in FreeBSD
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# 6 Conclusion

## 6.1 Results

As of April 2007 the Linux® emulation layer is capable of emulating the Linux 2.6.16 kernel quite well. The remaining problems concern futexes, unfinished *at family of syscalls, problematic signals delivery, missing `epoll` and `inotify` and probably some bugs we have not discovered yet. Despite this we are capable of running basically all the Linux programs included in FreeBSD Ports Collection with Fedora Core 4 at 2.6.16 and there are some rudimentary reports of success with Fedora Core 6 at 2.6.16. The Fedora Core 6 linux_base was recently commited enabling some further testing of the emulation layer and giving us some more hints where we should put our effort in implementing missing stuff.

We are able to run the most used applications like `www/linux-firefox`, `www/linux-opera`, `net-im/skype` and some games from the Ports Collection. Some of the programs exhibit bad behaviour under 2.6 emulation but this is currently under investigation and hopefully will be fixed soon. The only big application that is known not to work is the Linux Java™ Development Kit and this is because of the requirement of `epoll` facility which is not directly related to the Linux kernel 2.6.

We hope to enable 2.6.16 emulation by default some time after FreeBSD 7.0 is released at least to expose the 2.6 emulation parts for some wider testing. Once this is done we can switch to Fedora Core 6 linux_base, which is the ultimate plan.

## 6.2 Future work

Future work should focus on fixing the remaining issues with futexes, implement the rest of the *at family of syscalls, fix the signal delivery and possibly implement the `epoll` and `inotify` facilities.

We hope to be able to run the most important programs flawlessly soon, so we will be able to switch to the 2.6 emulation by default and make the Fedora Core 6 the default linux_base because our currently used Fedora Core 4 is not supported any more.

The other possible goal is to share our code with NetBSD and DragonflyBSD. NetBSD has some support for 2.6 emulation but its far from finished and not really tested. DragonflyBSD has expressed some interest in porting the 2.6 improvements.

Generally, as Linux develops we would like to keep up with their development, implementing newly added syscalls. Splice comes to mind first. Some already implemented syscalls are also heavily crippled, for example `mremap` and others. Some performance improvements can also be made, finer grained locking and others.

## 6.3 Team

I cooperated on this project with (in alphabetical order):

- John Baldwin `<jhb@FreeBSD.org>`

- Konstantin Belousov `<kib@FreeBSD.org>`

- Emmanuel Dreyfus

- Scot Hetzel

- Jung-uk Kim `<jkim@FreeBSD.org>`

- Alexander Leidinger `<netchild@FreeBSD.org>`

- Suleiman Souhlal `<ssouhlal@FreeBSD.org>`

- Li Xiao

- David Xu `<davidxu@FreeBSD.org>`

I would like to thank all those people for their advices, code reviews and general support.

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