Re: NetBSD/usermode (Was: CVS commit: src)

[christos%astron.com@localhost (Christos Zoulas)]

In article <20111223013511.GA10564%panix.com@localhost>,
Thor Lancelot Simon  <tls%panix.com@localhost> wrote:
>On Thu, Dec 22, 2011 at 03:46:34PM -0500, Mouse wrote:
>> 
>> ptrace can support this too.  It can let sbrk/mmap through, but tell
>> the usermode kernel as it does so.  Or it can consult with the usermode
>> kernel first, and then let them through in a possibly modified form.
>
>I still don't see how this allows for regions shared between usermode,
>user-space processes.  The user-space code in the shared processes would
>have to periodically poll to see if any new shared regions were available
>to it, or something -- ugh.

There are many ways to achieve the result needed. One would be to
compile the usermode kernel process with a different emulation,
one where regular system calls do something else (notify the usermode
kernel), and the usermode kernel uses a different mechanism to do
syscalls. Another would be for the usermode kernel to translate
the syscall code during mapping. etc. A third one would be to add
kevent_syscall and enable it per lwp, and have usermode kernel
userland processes run in a different thread. They all have their
own sets of problems.

christos