Date: Wed, 1 Aug 2018 09:11:02 -0700 (PDT) From: "Rodney W. Grimes" <freebsd-rwg@pdx.rh.CN85.dnsmgr.net> To: Brooks Davis <brooks@freebsd.org> Cc: Mark Johnston <markj@freebsd.org>, Konstantin Belousov <kostikbel@gmail.com>, freebsd-hackers@freebsd.org Subject: Re: COMPAT_43 users? Message-ID: <201808011611.w71GB29F077911@pdx.rh.CN85.dnsmgr.net> In-Reply-To: <20180801155008.GC99632@spindle.one-eyed-alien.net>
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> On Wed, Aug 01, 2018 at 11:28:53AM -0400, Mark Johnston wrote: > > 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. > > I've had to figure out the COMPAT_OLDSOCK stuff a couple times in the > last few years. The way it's implementation is weird in that it seems > to change the system wide socket behavior in a few cases. It might be > a worthy endeavor to refactor this into alternate entry points for an > a.out compat layer (it's also patently absurd that you can invoke (e.g.) > cpuset_setdomain(2) from an a.out binary). I do not see what that would be absurd, a.out is a binary executable format, nothing should stop me from doing anything from an a.out that I can do from a elf. NOT being able to invoke foo(2) just because the binary was compiled to a.out would be absurd. -- Rod Grimes rgrimes@freebsd.org
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