Re: error message for invalid mapping?

[Joshua Haberman]
> I spent the last several days tracking down a bug in my code.  I was
> trying to make my pager send a MapItem in response to a page fault,
> but the mapping would never take effect.  The page fault would keep
> re-occuring.

> I finally figured out the problem: I was trying to send an fpage of
> memory that wasn't mapped in my own address space (I hadn't
> requested it from sigma0).  I was checking the success code from my
> MapItem IPC and I had turned on all tracepoints.  Neither indicated
> what the problem was.  Do you think that this error condition could
> either:

> 1. make the IPC fail?

No.  Trying to map a non-existent page is a legal operation.  There's
also the question about semantics.  If you map a 16K region (i.e.,
four pages) does the IPC fail if 1) none of the pages are present, 2)
at least one of the pages are not present, or 3) the majority of pages
are not present?

> 2. log a tracepoint message about the failure?

This would in my opinion just add noise to the kernel debugger/tracing
facility.

	eSk