From owner-freebsd-arch@freebsd.org Wed Jul 20 21:40:54 2016 Return-Path: Delivered-To: freebsd-arch@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 0C70AB9F153 for ; Wed, 20 Jul 2016 21:40:54 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from bigwig.baldwin.cx (bigwig.baldwin.cx [IPv6:2001:470:1f11:75::1]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id DB8D21726; Wed, 20 Jul 2016 21:40:53 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from ralph.baldwin.cx (c-73-231-226-104.hsd1.ca.comcast.net [73.231.226.104]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id B8189B923; Wed, 20 Jul 2016 17:40:52 -0400 (EDT) From: John Baldwin To: Warner Losh Cc: freebsd-arch@freebsd.org, Sean Bruno Subject: Re: Retiring in-tree GDB Date: Wed, 20 Jul 2016 14:30:01 -0700 Message-ID: <2386413.0UUCRd2KC2@ralph.baldwin.cx> User-Agent: KMail/4.14.3 (FreeBSD/10.3-STABLE; KDE/4.14.3; amd64; ; ) In-Reply-To: References: <2678091.es0AGJQ0Ou@ralph.baldwin.cx> <3871457.xzmrTRH8AM@ralph.baldwin.cx> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Wed, 20 Jul 2016 17:40:52 -0400 (EDT) X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 20 Jul 2016 21:40:54 -0000 On Wednesday, July 20, 2016 02:39:55 PM Warner Losh wrote: >=20 > > On Jul 20, 2016, at 2:19 PM, John Baldwin wrote: > >=20 > > On Wednesday, July 20, 2016 01:20:34 PM Sean Bruno wrote: > >>=20 > >> On 07/20/16 13:00, John Baldwin wrote: > >>> On Tuesday, October 20, 2015 01:36:28 PM John Baldwin wrote: > >>>> When this topic was last raised (by Warner I believe), the prima= ry objection > >>>> (certainly my main one) was that the in-tree kgdb was the only k= ernel debugger > >>>> available. kgdb is now available via the devel/gdb port in port= s (and as of > >>>> last week was enabled by default, so 'pkg install gdb' will get = you a kgdb > >>>> binary). The kgdb in ports is in general superior to the one in= the base > >>>> system. It is a cross debugger by default (and with my pending = patches to > >>>> libkvm it even supports cross debugging of vmcores). > >>>>=20 > >>>> There are some issues still with devel/gdb: namely it does not c= urrently > >>>> support some of the platforms supported by our in tree gdb such = as arm and > >>>> mips. For these platforms I think the in-tree gdb will need to = remain until > >>>> there is a suitable alternative. > >>>>=20 > >>>> However, I would like to propose that we retire the in-tree GDB = for some of > >>>> our platforms (namely x86) for 11. In particular, I think we sh= ould default > >>>> to enabling lldb and disabling gdb for platforms that meet the f= ollowing > >>>> criteria: > >>>>=20 > >>>> 1) devel/gdb works including thread and kgdb support > >>>> 2) lldb works > >>>>=20 > >>>> We could perhaps be more aggressive and handle lldb and gdb togg= les > >>>> independently, but I think we want to ship some sort of userland= debugger > >>>> out of the box on all of our platforms. The question I think mi= ght be if > >>>> we end up with platforms where 1) is true but 2) is not (such as= powerpc). > >>>>=20 > >>>> I believe that these conditions are only true for x86 currently.= > >>>>=20 > >>>> Comments? > >>>=20 > >>> I believe I've fixed the one last thing that was depending on /us= r/bin/gdb > >>> (crashinfo) to use devel/gdb if it is present. I'd either like t= o disable > >>> the base gdb on amd64 in the next week or so on HEAD, or perhaps = if people are > >>> really gutsy, disable it for all platforms on HEAD. We still don= 't have kgdb > >>> in ports for non-x86 (though for ppc at least kgdb in ports and b= ase is > >>> equally dysfunctional). > >>>=20 > >>> However, to start with: > >>>=20 > >>> 1) Does anyone have a reason to keep /usr/bin/gdb on amd64? > >>>=20 > >>> 2) Does anyone have a reason to keep /usr/bin/gdb on !amd64? > >>>=20 > >>=20 > >> I don't have an immediate use case in the mips/mips64 case. Shoul= d > >> ports "just work" here or do I need some kind of "cross gdb"? > >=20 > > ports gdb does not yet work on mips. Once it supports mips it will= work as > > both a native and cross debugger, but it just doesn't know about Fr= eeBSD/mips > > at all. Does /usr/bin/gdb work on mips? >=20 > It does, kinda. there=E2=80=99s a lot of stuff it gets right, so it c= an be useful. However, > there=E2=80=99s enough wrong that it=E2=80=99s super frustrating. So = there=E2=80=99s a low bar to > replacement. If I can build a new /bin/cat and debug it with a ports = gdb, > even if things are broken that kinda work now, I=E2=80=99m all for re= placement. >=20 > If /usr/bin/gdb were super duper cool on mips, I=E2=80=99d have a dif= ferent take, but > gdb on mips has never been stellar. Well, devel/gdb won't work at all on mips, so if we removed /usr/bin/gd= b on all platforms you'd be left with no debugger at all. Starting with amd64 i= s probably the most prudent for now. i386 is probably also a good candidate even = without working lldb. --=20 John Baldwin