Messages in this thread | | | Date | Sat, 01 May 1999 03:47:53 -0700 | From | "H. Peter Anvin" <> | Subject | Re: 64bit port |
| |
David Miller wrote: > > Date: Sat, 01 May 1999 03:32:48 -0700 > From: "H. Peter Anvin" <hpa@transmeta.com> > > I'd be really curious to hear the details. Are you making it > illegal to map a page both writable and executable? > > This is the crux of it, see my other mail. When you have seperate, > software controlled, instruction and data TLBs you can pull all of > this off cleanly I believe. >
I actually think that you don't need either of those constraints. What you *do* need, however, are separate r, w and x permissions on each page. Also the instruction set needs to be amenable to these kinds of scans; most RISCs are. You only need to keep each page in one of two states: writable or executable. When you write to an executable page, you get a trap, and flip it to the other state; when you execute, you again get a trap, scan the page, and put it back in the executable state.
-hpa
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
| |