[Syllable-kernel] IO operations

[Jacek <xo...@o2...>]

Hello,
I'm writing here for the firs time. Sorry in advance if I'll make any
mistakes with my english. Please ignore them or you can tell me about them,
I would be grateful :)

I've been thinking about disallowing applications to make input/output
operations on processor's ports.
I've been looking at the kernel code and here is what I noticed, please tell
me if I'm right:
1. all kernel and application code currently runs on privilege level 0
2. syscalls are called via int 0x80
3. there are different addres spaces for kernel and user code (different
segment selectors)
4. appserver is also user program
5. appserver's drivers also run as user code and perform direct port
operations

The easiest way would be to dissallow all user applications making IO
operations by changing their privilege level to ie 3 and setting the
processor's IOPL in EFLAGS to ie 1. There is a problem if appservers uses
direct IO operations. If so either the appsever could run on different IOPL
or (better I think) the I/O Permission Bit Map could be used. There could be
even only one bit map for the appserver and all his drivers.
For now it could allow opperations on all ports. Later there could be
implemented some functions that would allow registering port ranges that
driver wants to use, etc.

What do you think about all this?

Regards
Jacek Kutzmann

PS: If there are any technical documents about Syllable kernel I'd also be
glad if someone told me about them.