Re: RFC: ENOSYS vs SIGSYS for FreeBSD ABIs

Hi Konstantin,

Am Mon, Apr 20, 2026 at 08:34:07PM +0300 schrieb Konstantin Belousov:
> 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.

A dynamically linked init means that if anything goes wrong with shared
library support, init doesn't get up and you end up with a nonbooting
system.  Is this really a good idea?

Yours,
Robert Clausecker

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