Re: kernel stack challenge

[Timothy Miller <miller@techsource.com>]

Sergiy Lozovsky wrote:

> 
> 1. Give system administrator possibility to change
> security policy easy enough without C programminig
> inside the kernel (we should not expect system
> administartor to be a kernel guru). Language of higher
> lavel make code more compact (C - is too low level,
> that's why people use PERL for example or LISP). Lisp
> was chosen because of very compact VM - around 100K.

And you expect your sysadmins to know LISP?  I would hardly think of 
LISP as any kind of simplification to anything.

I mean, I like the language and all, but it is in no way "simpler" than 
C and it's definately not appropriate for in-kernel stuff.

> 
> 2. Protect system from bugs in security policy created
> by system administrator (user). LISP interpreter is a
> LISP Virtual Machine (as Java VM). So all bugs are
> incapsulated and don't affect kernel. Even severe bugs
> in this LISP kernel module can cause termination of
> user space application only (except of stack overflow
> - which I can address). LISP error message will be
> printed in the kernel log.

In theory, we could develop the kernel in a language that does all sorts 
of protection, garbage collection, run-time checking, etc.  Kernel 
developers choose not to because the performance hit would be HORRIBLE.


Now... that doesn't mean you can't do kernel-level stuff in LISP.  You 
just don't do it _in_ the kernel.  Given the absolutely MASSIVE overhead 
you're already incurring by using a LISP interpreter, having to 
context-switch into user space won't hurt in the least.  So, what you do 
is have a C-based stub in the kernel which passes stuff off to the 
user-space LISP daemon which calls back into the kernel for accessing 
devices, etc.

THAT would be a much better way of doing this.