Re: [Syllable-kernel] IO operations

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

Daniel wrote:
> On Tue, 2004-12-14 at 18:21 +0100, Jacek wrote:
>> 1. all kernel and application code currently runs on privilege level 0
>
>Nope.  User code runs at level 3.

That's great for me, half of work is done.

> I believe iopl is allowed (optionally) to root.  Anything not run as
> root does not have iopl access.

Unfortunately you're not right. You can make a simple test:

// this will disable your PS/2 mouse
int main() {
        asm("mov $0xA7, %al;out %al, $0x64");
}

sending 0xA8 to the same port will enable your mouse back

And the following code will reset your computer immediately (run it at your 
own risk)
int main() {
        asm("mov $0xFE, %al;out %al, $0x64");
}

What about other questions?