Date: Wed, 1 Aug 2018 11:28:53 -0400 From: Mark Johnston <markj@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: COMPAT_43 users? Message-ID: <20180801152853.GC97237@raichu> In-Reply-To: <20180801075512.GR40119@kib.kiev.ua> References: <20180731214920.GA95743@raichu> <20180801075512.GR40119@kib.kiev.ua>
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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.
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