Re: uaccess.h reimplementation, patch, 2.1.30 (WP detection)

Pavel Machek (
Tue, 1 Apr 1997 11:42:34 +0200 (MET DST)

On Mon, 31 Mar 1997, Paul Gortmaker wrote:

> Okay, as soon as I saw Linus mention the broken WP support, I realized why
> defining access_ok() to 1 was such a gain on i386. Since i386 requires the
> check to be done in software due to the broken write protect issue, of
> course access_ok() on i386 will be much more expensive (in both code size
> and speed). On i486 or better, the speed difference is next to nothing as
> seen below. There is still a size reduction win (20kB) though. Test is the
> same 270 page LaTeX doc, only this time run on an i486-66 box (but with the
> same NFS server). As before, I've discarded the timing data from the first
> run after a reboot for obvious reasons.

Hey! The detection whether WP bit is working is BROKEN in 2.1.X. I thought
that it is not important, but it looks like it is. (I tried to fix it but
was unable to). On my AMD486DX2/80, 2.0.X's used to say that WP bit is
working ok, with 2.1.X it no longer works. (BTW it would be nice to
*always* print Checking WP bit, not only if test succeeds like it is done