Quoting Urban Boquist,

> As I get the messages, programs start dumping core, like sendmail and
> syslogd, other programs complain about "input/output error" and all
> sorts of weird stuff happens.

> This all began when I supped and rebuilt everything last week to get
> COMPAT_LINUX.

Whatever it is, it is almost impossible that it's related to the linux
compat code. Especially since it also happens when you are running
native NetBSD binaries.

The fact that sendmail and syslogd dump core, could well be due to a bug
that appeared in libc last week, and was fixed shortly thereafter; you may
have supped just when that bug was in the tree.

- Frank