Date: Wed, 1 Aug 2018 10:55:12 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Mark Johnston <markj@freebsd.org> Cc: freebsd-hackers@freebsd.org Subject: Re: COMPAT_43 users? Message-ID: <20180801075512.GR40119@kib.kiev.ua> In-Reply-To: <20180731214920.GA95743@raichu> References: <20180731214920.GA95743@raichu>
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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.
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