From owner-freebsd-hackers@freebsd.org Wed Aug 1 07:55:28 2018 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 7D088105CD63 for ; Wed, 1 Aug 2018 07:55:28 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id F0E768718E; Wed, 1 Aug 2018 07:55:27 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.15.2/8.15.2) with ESMTPS id w717tClf067051 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 1 Aug 2018 10:55:15 +0300 (EEST) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua w717tClf067051 Received: (from kostik@localhost) by tom.home (8.15.2/8.15.2/Submit) id w717tC7f067049; Wed, 1 Aug 2018 10:55:12 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Wed, 1 Aug 2018 10:55:12 +0300 From: Konstantin Belousov To: Mark Johnston Cc: freebsd-hackers@freebsd.org Subject: Re: COMPAT_43 users? Message-ID: <20180801075512.GR40119@kib.kiev.ua> References: <20180731214920.GA95743@raichu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180731214920.GA95743@raichu> User-Agent: Mutt/1.10.1 (2018-07-13) X-Spam-Status: No, score=-2.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FROM,NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.1 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on tom.home X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.27 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 01 Aug 2018 07:55:28 -0000 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.