filemon: Reject FILEMON_SET_FD commands when the fd is a kqueue

[markj]

Summary

When FILEMON_SET_FD is used, the filemon handle effectively wraps the
passed file. In particular, the handle may be inherited by a child
process, or transferred over a unix domain socket, so we must verify
that the backing file permits this.

Reported by: [e-mail]

[emaste]

Looks reasonable. filemon.4 needs an update too?

[markj]

Document EINVAL and EBADF.

[pauamma_gundo.com]

Besides that unrelated nit, the manual page language LGTM. Can't speak to consistency with the code change.

share/man/man4/filemon.4

54–55

"binaries using an emulated ABI" maybe? Neither "of" and "foreign" look quite right.

[markj]

Unrelated fixups. Change "will" to "may" since filemon does at least
hook compat32 system calls.

[debdrup]

Manual page changes look good to me, can't comment on the code.

[emaste]

share/man/man4/filemon.4

54–55

"emulated" isn't quite right

Possibly "non-native" or "non-FreeBSD" ABIs

54–55

Oops this comment was stuck as a draft

[pauamma_gundo.com]

LGTM too.

[bdrewery]

+1