Re: subpage_prot() man page

[Paul Mackerras <paulus-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>]

On Sun, Oct 10, 2010 at 07:53:35AM +0200, Michael Kerrisk wrote:

> Paul, would you be willing to review this page for the system call
> that you added?

Thanks for doing this.  It looks fine, with just a couple of small
comments:

> .SH RETURN VALUE
> On success,
> .BR subpage_prot ()
> returns 0.
> Otherwise, one of the negated  error codes specified below is returned.

Actually, by the time it gets back out to userland, it follows the
usual convention for error codes on PowerPC: for an error, the
positive error code is returned (in r3) with the CR0.SO bit (bit 3 in
the condition code register) set to indicate error.  CR0.S0 is cleared
if there is no error.

So I would just remove the word "negated".

> .\" Perhaps we don't need to document this implementation detail:
> .\"
> .\" Implicit in this is that the regions of the address space that are
> .\" protected are switched to use 4k hardware pages rather than 64k
> .\" hardware pages (on machines with hardware 64k page support).
> .\" In fact the whole process is switched to use 4k hardware pages when the
> .\" subpage_prot system call is used, but this could be improved in future
> .\" to switch only the affected segments.

I'm pretty sure we now only switch the affected segment, not the whole
process.

Paul.
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