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diff --git a/debian/README.source b/debian/README.source new file mode 100644 index 000000000..ef42add62 --- /dev/null +++ b/debian/README.source @@ -0,0 +1,240 @@ +Document by Ximin Luo, Luca Bruno & Sylvestre Ledru + +This source package is unfortunately quite tricky and with several cutting +edges, due to the complexity of rust-lang bootstrapping system and the high +rate of language changes still ongoing. + +We try to describe here inner packaging details and the reasons behind them. + +If you are looking to help maintain this package, be sure to read the "Notes +for package maintainers" section further below. + + +Embedded libraries +================== + +The upstream source package embeds many external libraries. We make a great +effort to remove them and use system versions where possible, but there are a +few more remaining: + + * vendor/dlmalloc, vendor/windows_*_gnu, vendor/windows_*_msvc + + These are small C libraries designed to be statically linked; their upstream + does not support building them as a shared library and they are too small to + justify their own Debian package. + + +Building from source +==================== + +The Debian rustc package will use the system rustc to bootstrap itself from. +The system rustc has to be either the previous or the same version as the rustc +being built; the build will fail if this is not the case. + + sudo apt-get build-dep ./ + dpkg-buildpackage + # Or, to directly use what's in the Debian FTP archive + sudo apt-get build-dep rustc + apt-get source --compile rustc + +Alternatively, you may give the "pkg.rustc.dlstage0" DEB_BUILD_PROFILE to +instead use the process defined by Rust upstream. This downloads the "official" +stage0 compiler for the version being built from rust-lang.org. At the time of +writing "official" means "the previous stable version". + + sudo apt-get build-dep -P pkg.rustc.dlstage0 ./ + dpkg-buildpackage -P pkg.rustc.dlstage0 + # Or, to directly use what's in the Debian FTP archive + sudo apt-get build-dep -P pkg.rustc.dlstage0 rustc + apt-get source --compile -P pkg.rustc.dlstage0 rustc + +After [1] is fixed, both of these should in theory give identical results. + +If neither of these options are acceptable to you, e.g. because your distro +does not have rustc already and your build process cannot access the network, +see "Bootstrapping" below. + +[1] https://github.com/rust-lang/rust/issues/34902 + + +Bootstrapping +============= + +To bootstrap rustc on a distro that does not have it or cargo available on any +architecture (so cross-compiling is not an option) you can run `debian/rules +source_orig-stage0`. This creates a .dsc that does not Build-Depend on rustc or +cargo. Instead, it includes an extra orig-stage0 source tarball that contains +the official stage0 compiler, pre-downloaded from rust-lang.org so that your +build daemons don't need to access the network during the build. + + debian/rules source_orig-stage0 + # Follow the final manual instructions that it outputs. Then: + sbuild ../rustc_*.dsc && dput ../rustc_*.dsc + +To only bootstrap specific architectures, run this instead: + + upstream_bootstrap_arch="arm64 armhf" debian/rules source_orig-stage0 + +This way, other architectures will be omitted from the orig-stage0 tarball. You +might want to do this e.g. if these other architectures are already present in +your distro, but the $upstream_bootstrap_arch ones are not yet present. + +Notes +----- + +The approach bundles the upstream bootstrapping binaries inside the Debian +source package. This is a nasty hack that stretches the definition of "source +package", but has a few advantages explained below. + +The traditional Debian way of bootstrapping compilers - and other distros have +similar approaches - is some variant of the following: + +1. A developer locally installs some upstream bootstrapping binaries. +2. They locally build a Debian package, using these binaries as undeclared + build dependencies. +3. They upload these binary packages to Debian, which can be used as declared + Build-Depends in the future, including by the same package. + +The problem with this is, Debian does not have any policy nor infrastructure +that can try to reproduce what this developer supposedly did. + +Using bootstrapping binary blobs *at some point of the process* is unavoidable. +Rather than pretending we didn't do this, it is better to record *which blobs* +we used, so it can be audited later. If we bundle non-Debian build-dependencies +inside the source package, then we can do a *source-only upload*, and the +building of the binary packages can be done by the normal build infrastructure. + +If the build process is reproducible [1] then we can be sure that *you* (as the +developer that prepared the source-only upload) didn't backdoor the binaries, +nor did the build daemons even if they were compromised during the build. + +The bootstrapping binaries may still have been backdoored, but this is true in +both scenarios. So our arrangement is still a strict improvement in security, +because it reduces the set of "things that may have been backdoored". Also, +more people use the upstream binaries than the "magical original Debian +package", so backdoors have a greater chance of being detected in the former. + +In the long run, this process is laying the foundations for doing Diverse +Double-Compilation [2], where we use *many independent* bootstrapping binaries +to reproduce bit-for-bit identical output compilers, giving confidence that +nothing was backdoored along the way. + +[1] The build process for rustc is currently *not* reproducible but we're + working towards it. https://github.com/rust-lang/rust/issues/34902 +[2] http://www.dwheeler.com/trusting-trust/ + + +Maintaining this package +======================== + +Import of a new upstream version +-------------------------------- + +$ apt install equivs python3-magic +$ sudo mk-build-deps -irt 'aptitude -R' +$ uscan --verbose # or debian/rules source_orig-beta, for beta +$ ver=UPDATE-ME # whatever it is, probably X.YY.Z or X.YY.Z~beta.N + +$ debian/refresh-early-patches.sh $ver +# This will require an understanding of how git-rebase and git-mergetool works +# We recommend either kdiff3 or p4merge (proprietary) as the git-mergetool. + +$ tar xf ../rustc-${ver/\~/-}-src.tar.xz && ( cd rustc-${ver/*~*/beta}-src/ && pwd && ../debian/prune-unused-deps ) && rm -rf rustc-${ver/*~*/beta}-src/ +$ git diff +# Review the diff. If it removes too much stuff, it could mean that rustc +# pulled in new unnecessary dependencies in this newer version. See if you can +# drop them by amending the patch "d-0000-ignore-removed-submodules.patch". +# Rerun the above "tar ..." commands again and check that your patch works. +# For example, there is absolutely no reason why rustc should need openssl. + +$ git commit -m "Update Files-Excluded for new upstream version ${ver/\~/-}" debian/copyright +$ uscan --verbose # yes, again, to pick up the new Files-Excluded stuff + # or debian/rules source_orig-beta, for beta + +# Keep running this and follow its instructions, until it gives no output: +$ debian/check-orig-suspicious.sh $ver +# When you are satisfied with the above, proceed: + +$ git checkout debian/experimental +$ gbp import-orig ../rustc_$ver+dfsg1.orig.tar.xz +$ dch -v $ver+dfsg1-1~exp1 "New upstream release." +$ debian/rules update-version +# might also need to bump the version of the cargo Build-Depends +# then refresh patches, etc etc +# Use /usr/share/cargo/scripts/guess-crate-copyright to help update d/copyright quickly + +# If you need to repack again, bump the 'repacksuffix' in d/watch then run +$ uscan --verbose --force-download +# This will do a local repack using the new Files-Excluded rules, without +# redownloading the orig tarball (despite the slightly misleading flag). + + +Proceeding after build failure +------------------------------ + +If your build fails, don't run `./x.py` directly as that will detect it's being +run with different settings, and run the build from scratch all over again. +overwriting all intermediate files. Instead, do: + +$ debian/rules run_rustbuild X_CMD="build|test|install" X_FLAGS="whatever" + +Hopefully, this will directly proceed to the step that failed, without +rebuilding everything in between. + + +Comparing Debian rustc vs upstream rustc +---------------------------------------- + +This package does things the Debian way, which differs significantly from +upstream practices. If you find a bug, you might want to check if it is present +in the upstream package. Run "debian/rules debian/config.toml" to generate our +config.toml that you can then use in an upstream directory **unpacked from the +release tarball*. (It is more complex to get this working with their git repo.) + +This will configure it in a "halfway" style between upstream and Debian. +Specifically, it will not build LLVM nor download stuff from crates.io, yet +Debian patches are *not* applied. These specific settings were chosen as a +tradeoff between convenience vs being close to what upstream does - so that the +chances of a bug here being a genuine upstream issue rather than a Debian bug, +is much higher. Also, with the exception of LLVM, these are non-default modes +*supported by* upstream so they would be happy to receive bug reports about it +even if your issue only occurs here. + +OTOH if you need to test a completely clean upstream build, including all the +annoying stuff like building LLVM and downloading dependencies from crates.io, +simply unpack the tarball and run `./configure && ./x.py build` etc as normal. +This can be useful for confirming that an issue is caused by Debian's LLVM. + +If you need to test a LLVM patch, do something like this: + +# build your patched LLVM debs, then: +$ mkdir -p llvm-destdir && cd llvm-destdir +$ ver=4.0; VERSION=FIXME +$ for i in llvm-$ver llvm-$ver-dev llvm-$ver-runtime llvm-$ver-tools libllvm$ver; do \ + dpkg -x ../"$i"_*${VERSION}_*.deb .; done +$ cd ../rustc +$ debian/rules LLVM_DESTDIR=$PWD/../llvm-destdir build + +If you need to test a patch to the stage0 rustc, do something like this: + +# build your patched rustc debs or upstream rustc, then: +$ mkdir -p rust-destdir && cd rust-destdir +$ ver=1.20; VERSION=FIXME; +$ for i in rustc libstd-rust-$ver libstd-rust-dev; do \ + dpkg -x ../"$i"_*${VERSION}_*.deb .; done +$ cd ../rustc +$ debian/rules RUST_DESTDIR=$PWD/../rust-destdir build + + +Useful links +------------ + +The Fedora rust team is more active than the Debian one. Here are their links: + +Source code +https://src.fedoraproject.org/rpms/rust/tree/ + +Binary packages and test logs +https://kojipkgs.fedoraproject.org//packages/rust/ +If the same test fails both on Fedora and Debian it's a good indication that +we're not Doing It Wrong and can file a valid bug upstream. |