Re: RFC: ENOSYS vs SIGSYS for FreeBSD ABIs

On Mon, Apr 20, 2026 at 08:03:22AM +0000, Brooks Davis wrote:
> As a developer I've never found SIGSYS helpful.  That being said, I
> don't think a more nuanced approach would be all that hard.  One option
> I've pondered would to automatially flip kern.signosys to 0 (and
> probably kern.lognosys to > 0) if init gets a SIGSYS (maybe limited to
> before it forks successfully).  You'd probably want some pretty shouty
> logging to go with that, but it would let you survive a kernel roll-back
> with new syscalls in csu code.

I think by 'csu' you mean 'all code executed before main()'.
crt1.o is now very minimal, the real startup work is delegated to libc.

I think it is time to switch init to be dynamically linked.
At least this would make the job of fixing userspace (instead of kernel)
to be limited to rtld+libc, instead of rtld+libc+init.