Re: Proposal: Remove filemon(4); switch make meta to ktrace

[christos%astron.com@localhost (Christos Zoulas)]

In article <20200112210449.ACCCA60BAC%jupiter.mumble.net@localhost>,
Taylor R Campbell  <riastradh%NetBSD.org@localhost> wrote:
>-=-=-=-=-=-
>
>[followups on tech-kern]
>
>I propose to remove the filemon(4) device.
>
>- Why?  filemon(4), which writes records of file-related system calls
>  to a file, is redundant with ktrace, except potentially for
>  performance concerns (but I don't know whether anyone has measured).
>  Our implementation raises some security and correctness concerns by
>  munging the syscall table, and doesn't compose well.
>
>  We could devote some engineering effort to fixing those issues, but
>  as far as I know, filemon(4) is not often exercised in NetBSD so it
>  doesn't seem that fixing filemon(4) is worth the effort.
>
>- What instead?  The attached patch (patch set make-meta-v2.patch;
>  combined diff make-meta-v2.diff) replaces make's use of /dev/filemon
>  by ktrace, in meta mode.  Other applications could use the same
>  logic verbatim; if it turns out that there are other applications we
>  could migrate the logic from usr.bin/make/filemon/filemon_*.c to a
>  library.
>
>  At sjg's request, there's a compile-time option -- setting the make
>  variable USE_FILEMON=ktrace vs USE_FILEMON=dev -- to switch between
>  filemon back ends, since Juniper still uses /dev/filemon on FreeBSD
>  which has seen more maintenance, security, and performance updates.
>  (This might also enable future strace, dtrace, &c., back ends.)
>
>  So this patch would still leave a small amount of unexercised code
>  in our tree, but it's much smaller than before and only in userland,
>  not in kernel.
>
>Do you use filemon(4)?  Objections?  Thoughts?

I am good with the proposal. Thanks for working on this.

christos