Re: [PATCH 3/6] seccomp: Implement constant action bitmaps

On Thu, Sep 24, 2020 at 03:07:23AM -0500, YiFei Zhu wrote:

On Thu, Sep 24, 2020 at 2:37 AM Kees Cook [off-list ref] wrote:

quoted

quoted

This belongs over into patch 1.

Thanks! I was rushing to get this posted so YiFei Zhu wouldn't spend
time fighting with arch and Kconfig stuff. :) I'll clean this (and the
other random cruft) up.

Wait, what? I'm sorry. We have already begun fixing the mentioned
issues (mostly the split bitmaps for different arches). Although yes
it's nice to have another implementation to refer to so we get the
best of both worlds (and yes I'm already copying some of the code I
think are better here over there), don't you think it's not nice to
say "Hey I've worked on this in June, it needed rework but I didn't
send the newer version. Now you sent yours so I'll rush mine so your
work is redundant."?

I was trying to be helpful: you hadn't seen the RFC, and it was missing
the emulator piece, which I wanted to be small, so I put got it out the
door today. I didn't want you to think you needed to port the larger
emulator over, for example.

That said, I do think this should be configurable. Users would be free
to experiment with the bitmap on or off, just like users may turn
seccomp off entirely. A choice also allows users to select different
implementations, a few whom I work with have ideas on how to
accelerate / cache argument dependent syscalls, for example.

I'm open to ideas, but I want to have a non-optional performance
improvement as the first step. :) "seccomp is magically faster" was my
driving goal.

-- 
Kees Cook