debian/README.source

   1 Document by Ximin Luo, Luca Bruno & Sylvestre Ledru
   2
   3 This source package is unfortunately quite tricky and with several cutting
   4 edges, due to the complexity of rust-lang bootstrapping system and the high
   5 rate of language changes still ongoing.
   6
   7 We try to describe here inner packaging details and the reasons behind them.
   8
   9 If you are looking to help maintain this package, be sure to read the "Notes
  10 for package maintainers" section further below.
  11
  12
  13 Embedded libraries
  14 ==================
  15
  16 This source package embeds several external libraries (foeked and managed
  17 by rust upstream as git submodules).
  18 In early stages, many more libraries were forked/emebedded but we are steadily
  19 progressing in splitting them out.
  20
  21 Here below the remaining ones, with the technical reasons.
  22
  23  * binaryen from https://github.com/alexcrichton/binaryen.git
  24    -> temporary until LLVM lld is available
  25    - see issue upstream: TODO waiting for alexcrichton to create one
  26
  27  * compiler-rt from https://github.com/rust-lang/compiler-rt
  28    -> system-wide compiler-rt fails during linkage
  29
  30    Bug reported upstream, still to be fixed, see:
  31     - https://github.com/rust-lang/rust/issues/15054
  32     - https://github.com/rust-lang/rust/issues/15708
  33
  34 As a summary, we plan to:
  35  * work with upstream to fix compiler-rt linkage soon.
  36
  37  -- Sylvestre Ledru <sylvestre@debian.org>  Sat, 06 May 2017 13:26:08 +0200
  38
  39
  40 Building from source
  41 ====================
  42
  43 The Debian rustc package will use the system rustc to bootstrap itself from.
  44 The system rustc has to be either the previous or the same version as the rustc
  45 being built; the build will fail if this is not the case.
  46
  47     sudo apt-get build-dep ./
  48     dpkg-buildpackage
  49     # Or, to directly use what's in the Debian FTP archive
  50     sudo apt-get build-dep rustc
  51     apt-get source --compile rustc
  52
  53 Alternatively, you may give the "pkg.rustc.dlstage0" DEB_BUILD_PROFILE to
  54 instead use the process defined by Rust upstream. This downloads the "official"
  55 stage0 compiler for the version being built from rust-lang.org. At the time of
  56 writing "official" means "the previous stable version".
  57
  58     sudo apt-get build-dep -P pkg.rustc.dlstage0 ./
  59     dpkg-buildpackage
  60     # Or, to directly use what's in the Debian FTP archive
  61     sudo apt-get build-dep -P pkg.rustc.dlstage0 rustc
  62     apt-get source --compile -P pkg.rustc.dlstage0 rustc
  63
  64 After [1] is fixed, both of these should in theory give identical results.
  65
  66 If neither of these options are acceptable to you, e.g. because your distro
  67 does not have rustc already and your build process cannot access the network,
  68 see "Bootstrapping" below.
  69
  70 [1] https://github.com/rust-lang/rust/issues/34902
  71
  72
  73 Bootstrapping
  74 =============
  75
  76 To bootstrap rustc on a distro that does not have it or cargo available on any
  77 architecture (so cross-compiling is not an option) you can run `debian/rules
  78 source_orig-stage0`. This creates a .dsc that does not Build-Depend on rustc or
  79 cargo. Instead, it includes an extra orig-stage0 source tarball that contains
  80 the official stage0 compiler, pre-downloaded from rust-lang.org so that your
  81 build daemons don't need to access the network during the build.
  82
  83     debian/rules source_orig-stage0
  84     # Follow the final manual instructions that it outputs. Then:
  85     sbuild ../rustc_*.dsc && dput ../rustc_*.dsc
  86
  87 To only bootstrap specific architectures, run this instead:
  88
  89     upstream_bootstrap_arch="arm64 armhf" debian/rules source_orig-stage0
  90
  91 This way, other architectures will be omitted from the orig-stage0 tarball. You
  92 might want to do this e.g. if these other architectures are already present in
  93 your distro, but the $upstream_bootstrap_arch ones are not yet present.
  94
  95 Notes
  96 -----
  97
  98 The approach bundles the upstream bootstrapping binaries inside the Debian
  99 source package. This is a nasty hack that stretches the definition of "source
 100 package", but has a few advantages explained below.
 101
 102 The traditional Debian way of bootstrapping compilers - and other distros have
 103 similar approaches - is some variant of the following:
 104
 105 1. A developer locally installs some upstream bootstrapping binaries.
 106 2. They locally build a Debian package, using these binaries as undeclared
 107    build dependencies.
 108 3. They upload these binary packages to Debian, which can be used as declared
 109    Build-Depends in the future, including by the same package.
 110
 111 The problem with this is, Debian does not have any policy nor infrastructure
 112 that can try to reproduce what this developer supposedly did.
 113
 114 Using bootstrapping binary blobs *at some point of the process* is unavoidable.
 115 Rather than pretending we didn't do this, it is better to record *which blobs*
 116 we used, so it can be audited later. If we bundle non-Debian build-dependencies
 117 inside the source package, then we can do a *source-only upload*, and the
 118 building of the binary packages can be done by the normal build infrastructure.
 119
 120 If the build process is reproducible [1] then we can be sure that *you* (as the
 121 developer that prepared the source-only upload) didn't backdoor the binaries,
 122 nor did the build daemons even if they were compromised during the build.
 123
 124 The bootstrapping binaries may still have been backdoored, but this is true in
 125 both scenarios. So our arrangement is still a strict improvement in security,
 126 because it reduces the set of "things that may have been backdoored". Also,
 127 more people use the upstream binaries than the "magical original Debian
 128 package", so backdoors have a greater chance of being detected in the former.
 129
 130 In the long run, this process is laying the foundations for doing Diverse
 131 Double-Compilation [2], where we use *many independent* bootstrapping binaries
 132 to reproduce bit-for-bit identical output compilers, giving confidence that
 133 nothing was backdoored along the way.
 134
 135 [1] The build process for rustc is currently *not* reproducible but we're
 136     working towards it. https://github.com/rust-lang/rust/issues/34902
 137 [2] http://www.dwheeler.com/trusting-trust/
 138
 139
 140 Maintaining this package
 141 ========================
 142
 143 Import of a new upstream version
 144 --------------------------------
 145
 146 # Make sure you apply the patch mentioned in #855464 to /usr/bin/mk-origtargz
 147
 148 $ sudo mk-build-deps -irt 'aptitude -R'
 149 $ uscan --verbose
 150 $ ver=UPDATE-ME # whatever it is, X.YY.0 or X.YY.0~beta probably
 151 $ tar xf ../rustc-${ver/\~/-}-src.tar.xz && ( cd rustc-${ver/*~*/beta}-src/ && ../debian/prune-unused-deps ) && rm -rf rustc-${ver/*~*/beta}-src/
 152 # ^ If this fails, you probably need to refresh patches or edit debian/prune-unused-deps
 153 $ git commit -m "Update Files-Excluded for new upstream version ${ver/\~/-}" debian/copyright
 154 $ uscan --verbose # yes, again, to pick up the new Files-Excluded stuff
 155
 156 # Keep running this and follow its instructions, until it gives no output:
 157 $ debian/check-orig-suspicious.sh $ver
 158 # When you are satisfied with the above, proceed:
 159
 160 $ gbp import-orig ../rustc_$ver+dfsg1.orig.tar.xz
 161 $ dch -v $ver+dfsg1-1 -m "New upstream release."
 162 $ debian/rules update-version
 163 # might also need to bump the version of the cargo Build-Depends
 164 # then refresh patches, etc etc
 165 # Use /usr/share/cargo/guess-crate-copyright to help update d/copyright quickly
 166
 167 # If you need to repack again, bump the 'repacksuffix' in d/watch then run
 168 $ uscan --verbose --force-download
 169 # This will do a local repack using the new Files-Excluded rules, without
 170 # redownloading the orig tarball (despite the slightly misleading flag).
 171
 172
 173 Proceeding after build failure
 174 ------------------------------
 175
 176 If your build fails, don't run `./x.py` directly as that will detect it's being
 177 run with different settings, and run the build from scratch all over again.
 178 overwriting all intermediate files. Instead, do:
 179
 180 $ debian/rules run_rustbuild X_CMD="build|test|install" X_FLAGS="whatever"
 181
 182 Hopefully, this will directly proceed to the step that failed, without
 183 rebuilding everything in between.
 184
 185
 186 Comparing Debian rustc vs upstream rustc
 187 ----------------------------------------
 188
 189 This package does things the Debian way, which differs significantly from
 190 upstream practices. If you find a bug, you might want to check if it is present
 191 in the upstream package. Run "debian/rules debian/config.toml" to generate our
 192 config.toml that you can then use in an unpacked upstream directory.
 193
 194 This will configure it in a "halfway" style between upstream and Debian.
 195 Specifically, it will not build LLVM nor download stuff from crates.io, yet
 196 Debian patches are *not* applied. These specific settings were chosen as a
 197 tradeoff between convenience vs being close to what upstream does - so that the
 198 chances of a bug here being a genuine upstream issue rather than a Debian bug,
 199 is much higher. Also, with the exception of LLVM, these are non-default modes
 200 *supported by* upstream so they would be happy to receive bug reports about it
 201 even if your issue only occurs here.
 202
 203 OTOH if you need to test a completely clean upstream build, including all the
 204 annoying stuff like building LLVM and downloading dependencies from crates.io,
 205 simply unpack the tarball and run `./configure && ./x.py build` etc as normal.
 206 This can be useful for confirming that an issue is caused by Debian's LLVM.
 207
 208 If you need to test a LLVM patch, do something like this:
 209
 210 # build your patched LLVM debs, then:
 211 $ mkdir -p llvm-destdir && cd llvm-destdir
 212 $ ver=4.0; VERSION=FIXME
 213 $ for i in llvm-$ver llvm-$ver-dev llvm-$ver-runtime llvm-$ver-tools libllvm$ver; do \
 214     dpkg -x ../"$i"_*${VERSION}_*.deb .; done
 215 $ cd ../rustc
 216 $ debian/rules LLVM_DESTDIR=$PWD/../llvm-destdir build
 217
 218 If you need to test a patch to the stage0 rustc, do something like this:
 219
 220 # build your patched rustc debs or upstream rustc, then:
 221 $ mkdir -p rust-destdir && cd rust-destdir
 222 $ ver=1.20; VERSION=FIXME;
 223 $ for i in rustc libstd-rust-$ver libstd-rust-dev; do \
 224     dpkg -x ../"$i"_*${VERSION}_*.deb .; done
 225 $ cd ../rustc
 226 $ debian/rules RUST_DESTDIR=$PWD/../rust-destdir build
 227
 228
 229 Useful links
 230 ------------
 231
 232 The Fedora rust team is more active than the Debian one. Here are their links:
 233
 234 Source code
 235 https://src.fedoraproject.org/cgit/rpms/rust.git/tree/
 236
 237 Binary packages and test logs
 238 https://kojipkgs.fedoraproject.org//packages/rust/
 239 If the same test fails both on Fedora and Debian it's a good indication that
 240 we're not Doing It Wrong and can file a valid bug upstream.
 241
 242 Package metadata
 243 https://admin.fedoraproject.org/pkgdb/package/rpms/rust/