COMPAT_43 users?

[Mark Johnston]

On Wed, Aug 01, 2018 at 10:55:12AM +0300, Konstantin Belousov wrote:
> On Tue, Jul 31, 2018 at 05:49:20PM -0400, Mark Johnston wrote:
> > The COMPAT_43 kernel option, which enables syscall support for 4.3BSD
> > binaries, hasn't been enabled in the standard kernel configs for well
> > over a decade, and doesn't appear to be a dependency of any other kernel
> > features.  Nonetheless, the kernel contains quite a bit of code to
> > support this option.  Does anyone use it in modern versions of FreeBSD
> > or have any arguments for keeping it?
> 
> COMPAT_43 means two things, the third part is a.out image activator.
> First thing is the lcall $7.$0 syscall emulator, both on amd64 and
> (surprisingly) i386, after 4/4 split.  Second thing is the syscalls
> compat shims.
> 
> Together, all three things allow to run pre-3.x binaries on the modern
> machines, including amd64. I think this is useful at least for 'waving
> the flag' about our ABI compatibility guarantees, and for the historic
> software reconstruction. I run 1.1.8 chroot and several old binaries
> sometimes, I know that bde does, and there was at least one more user
> some time ago.
> 
> What do you mean by a lot of code ?  Syscall compats is relatively easy.
> lcall $7,$0 emulation is very non-trivial but tiny.  I do maintain this
> code and do not want it to go away.

Thanks, fair enough.  The question was prompted by seeing lots of
COMPAT_OLDSOCK ifdefs while working on some socket code.