Date: Wed, 7 Aug 2019 13:12:24 -0700 (PDT) From: "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net> To: Pedro Giffuni <pfg@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org, freebsd-hackers@freebsd.org, freebsd-arch@freebsd.org Subject: Re: svn commit: r350550 - head/share/mk Message-ID: <201908072012.x77KCObt089132@gndrsh.dnsmgr.net> In-Reply-To: <86621ce5-3a8d-2e22-f146-3b0cc8252124@FreeBSD.org>
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> On 07/08/2019 11:00, John Baldwin wrote: > > On 8/6/19 9:56 AM, Glen Barber wrote: > >> On Sat, Aug 03, 2019 at 01:06:18AM +0000, John Baldwin wrote: > >>> Author: jhb > >>> Date: Sat Aug 3 01:06:17 2019 > >>> New Revision: 350550 > >>> URL: https://svnweb.freebsd.org/changeset/base/350550 > >>> > >>> Log: > >>> Flip REPRODUCIBLE_BUILD back to off by default in head. > >>> > >>> Having the full uname output can be useful on head even with > >>> unmodified trees or trees that newvers.sh fails to recognize as > >>> modified. > >>> > >>> Reviewed by: emaste > >>> Differential Revision: https://reviews.freebsd.org/D20895 > >>> > >> I would like to request this commit be reverted. While the original > >> commit message to enable this knob stated the commit would be reverted > >> after stable/12 branched, I have seen no public complaints about > >> enabling REPRODUCIBLE_BUILD by default (and quite honestly, do not see > >> the benefit of disabling it by default -- why wouldn't we want > >> reproducibility?). > >> > >> To me, this feels like a step backwards, with no tangible benefit. > >> Note, newvers.sh does properly detect a modified tree if it can find > >> the VCS metadata directory (i.e., .git, .svn) -- I know this because > >> I personally helped with it. > >> > >> In my opinion, those that want the non-reproducible metadata included in > >> output from 'uname -a' should set WITHOUT_REPRODUCIBLE_BUILDS in their > >> src.conf. Turning off a sane default for the benefit of what I suspect > >> is likely a short list of use cases feels like a step in the wrong > >> direction. > > My arguments for flipping this in head (and head only) are that the data > > provided in uname -a when this is disabled is useful for development, and > > that in head we do tailor settings towards development (e.g. GENERIC in > > head vs GENERIC in stable). > > > > The logic to handle modified trees has an inherent assumption that I think > > is false, at least for my workflow and I suspect many others. I do builds > > and tests of kernels on separate machines (VMs or bare metal) from where I > > use VCS to manage sources so that a kernel crash doesn't toast my source > > tree. The trees are then shared to the build/test machines via NFS. As > > a result, the build/test machines are not always able to detect that the > > tree is modified either because a subset of the checkout is exported via > > NFS, or the VCS tool isn't installed on the build/test machines because > > they are generally barebones systems with only a base installed. This > > does mean that flipping the knob off doesn't provide all of the same info, > > but it does provide the path, and the path matters because 'kgdb -n last' > > uses it, and because if you use separate directories for separate projects > > (e.g. git worktrees), then the path tells you which test kernel you booted. > > (It is not uncommon for me to have several test projects in flight on a > > single test machine for different branches.) > > > > In the original discussion on arch, we collectively recognized that > > developer builds vs release builds were different and needed different > > defaults. The compromise reached at that time was to depend on the VCS > > to detect developer builds to choose the policy. What I have found is that > > in practice for at least my workflow that doesn't actually work. I posit > > that the majority of kernels built from head are developer builds, not > > releases, and that the default should cater to that. You could also always > > patch release.sh to set WITH_REPRODUCIBLE_BUILD in the environment which I > > think would give a more accurate sense of when builds are releases or not. > > > > However, I will yield to whatever the consensus is. > > +1 keeping metadata in head. I am conflicted on this one, and I think there is a reasonable argument on both sides, but from what I have read here this appears to be mostly the kernel that is at issue, loss of the meta data from newvers.sh in the kernel is infact a PITA, even on stable or production release systems. I propose a compromise, add 2 knobs: WITHOUT_REPRODUCIBLE_KERNEL (aka get your metadata in uname) WITH_REPRODUCIBLE_USERLAND (aka reproducible userland) WITH{,OUT}_REPRODUCIBLE_BUILD overrides both, for backwards compat, and neither should be defined by default. Somehow set WITH_REPRODUCIBLE_KERNEL for builds of GENERIC for releases/snapshots, but do not ship the system with it set (I can here a growl from Glen on this) Thus we build a reproducible kernel and ship it with the system but if the user builds a kernel it gets meta data to indicate it is no longer a stock kernel. FYI, upon finding I could not figure out what kernel I was running after installing 12.0 release I turnd off REPRODUCIBLE on my kernel build VM for 12.0. I do leave it on if I am building userland. Thoughts? -- Rod Grimes rgrimes@freebsd.org
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