Re: pentium 4MB pages question for you MMU hackers

Derrik Pates (dpates@Cavern.NMSU.Edu)
Fri, 3 Jan 1997 13:19:20 -0700 (MST)

On Fri, 3 Jan 1997, Morgan Sarges wrote:

> Id like to ask a dumb question here, before I say something really
> ignorant.

Sounds fine to me...

> What is ring0 code? How does it relate to linux/unix?

The Intel CPUs (and most other CPUs that do multitasking) have what are
called "rings" which describe what kind of access the process can get to
the CPU. The lowest ringlevel (ring 0) is your kernel and driver code.
Most other CPUs only have 2 ringlevels, but Intel 32-bit CPUs (the 386 and
up) have 4 ringlevels, but no one has ever put anything but rings 0 and 3
to use. Ring 3 (ring 1 on non Intel and clone CPUs) is where all
non-kernel code executes, so that it doesn't have free run of the system.

> What are GGI's?

GGI (General Graphics Interface, if memory serves) is a project to provide
a single unified display control method to Linux. Instead of having
SVGAlib and X running SUID root, they would be standard user processes
that access the GGI to write to the display device, and GGI would have a
device driver and some userspace libs to implement the services (the
intent is not to put too much of it into kernelspace).

> If ring0 is what I think it is, this could make 1997 very long and ugly.

I don't know what you think it is, but I don't think it's that bad. :)

Derrik Pates

"What'll you two lovable plush toys have?"
"How 'bout a root beer popsicle and an Orange Julius? What about you,
"Dishwater! And put it in a dirty glass!"
-Sam & Max
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