Re: SIGBUS + coredump

[David Holland <dholland-tech%netbsd.org@localhost>]

On Fri, Jan 18, 2019 at 09:50:38AM +0100, Martin Husemann wrote:
 > Sorry, I completely fail to parse this - can you start from scratch and
 > just describe the problem you think you are seeing?

My understanding is:

   - If you map a file such that part of the map is past EOF,
     accessing that part should cause SIGBUS.
   - It does.
   - However, you don't get a coredump because the coredump code fails
     on this region.
   - The proposed patch works around this by writing out a page of
     zeros when copyin_proc() returns EINVAL, instead of failing the
     dump.

This also implies that you can't get a coredump from a process that
has a file mapped past EOF, regardless of what triggers the coredump.

ISTM that it would better to skip the page than write out zeros...

-- 
David A. Holland
dholland%netbsd.org@localhost