Buildroot:ReproducibleBuilds

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As part of a Google Summer of Code project, Atharva Lele works on reproducible builds.

Away time

Arnout is away on: 10/6; some time in July; 15-19/8.

Meetings

Weekly meetings on appear.in/buildroot every Tuesdays at 14:30 UTC.

  • 2019-W23
    • Initial round-up of autobuild scripts patches
      • Basically, look OK-ish
      • Not bisectable because reverse order
      • Re-spin in correct order, but still split for ease of review
      • Ultimately, to be committed squashed together
    • diffoscope is silent on success, and so is cmp -> diffoscope_result.txt can be used to determine if reason should be set to reproducible.
    • Atharva will evaluate the reprotest and disorderfs projects to see if they can be useful for our reproducible tests.
    • Atharva should add a journal (log) to this wiki page two or three times a week
  • 2019-W22
    • As discussed on IRC, diffoscope only needs to be done if cmp detects differences. However, it doesn't take long anyway, and it *will* report if there is a difference.
    • diffoscope must be done on output/target/ and target/images, but autobuilders don't enable any images. So when doing a reproducible test, a tarball must be generated.
      • Manually try this, to be sure that it also looks inside the generated images.
      • Enable one / all target filesystems to check this manually.
      • Disable BR2_REPRODUCIBLE for this test, so there actually are some differences.
    • diffoscope has a lot of dependencies, we don't want all of these on the autobuilders
      • Try what the output is if the external tools are not installed
      • autobuilder script should fall back on cmp if diffoscope is not installed
    • Start patching autobuilder script to do a reproducible test.
      • Randomly enable BR2_REPRODUCIBLE, e.g. 10% of the times
      • Do the same build a second time. Only variation is time.
      • Run diffoscope on the result.
  • 2019-W21
    • Confirmed that starting from next week, work is full-time on GSoC (end of exams)
    • Review of the Yocto implementation
      • differences: Yocto is a distribution, so has a cache of the output, while buildroot does not
      • SOURCE_DATE_EPOCH and TZ: already done (depends on BR2_REPRODUCIBLE)
    • Doing similar in Buildroot:
      • Do a first build with a successfull config from autobuilders, after enabling BR2_REPRODUCIBLE
      • Then mv $(O)/target to $(O)/target-1; make clean; make
      • And then run diffoscope target-1 target/
    • Identify diffoscope dependencies to run it in autobuilders (eventually)
      • How to save and present the result on autobuilder site?
  • 2019-W20
    • introductions
    • confirm overal actions and planning

Yocto's Implementation

  • Shared State Mechanism: If input metadata hashes are same, outputs are reused. If inputs have changed, tools from Reproducible-Builds to be used. Further development yet to be done.
  • At this stage, binary contents should be same. However file timestamps (due to package managers) may be different.
  • Static Timezone value: Bugzilla
  • Adapted SOURCE_DATE_EPOCH: Bugzilla, Source-Date-Epoch - Reproducible Builds
  • Archives generated with deterministic metadata (using archive tools' arguments)
  • Remove non-deterministic data from rootfs

Diffoscope Dependencies

  • Depends on: python3, PyPI modules: libarchive-c, python-magic
  • External tools requied: Rscript, abootimg, apktool, bsdtar, bzip2, cbfstool, cd-iccdump, cmp, compare, convert, db_dump, diff, docx2txt, dumpxsb, enjarify, fdtdump, ffprobe, getfacl, ghc, gifbuild, gpg, gzip, identify, img2txt, isoinfo, javap, js-beautify, lipo, llvm-bcanalyzer, llvm-dis, lsattr, lz4, msgunfmt, nm, objcopy, objdump, ocamlobjinfo, odt2txt, oggDump, otool, pdftotext, pedump, pgpdump, ppudump, procyon, ps2ascii, readelf, showttf, sng, sqlite3, ssconvert, ssh-keygen, stat, tcpdump, unsquashfs, wasm2wat, xxd, xz, zipinfo, zipnote
  • This has tools used to compare a lot of file formats that probably aren't generated (like android APKs, Windows/Mac executables) in a Buildroot run. We can exclude those.
  • APT packages (available in Ubuntu, Debian): abootimg, acl, apktool, binutils-multiarch, bzip2, caca-utils, colord, coreutils, db-util, default-jdk-headless | default-jdk | java-sdk, device-tree-compiler, diffutils, docx2txt, e2fsprogs, enjarify, ffmpeg, fontforge-extras, fp-utils, genisoimage, gettext, ghc, ghostscript, giflib-tools, gnumeric, gnupg, gzip, imagemagick, jsbeautifier, libarchive-tools, llvm, lz4 | liblz4-tool, mono-utils, ocaml-nox, odt2txt, oggvideotools, openssh-client, pgpdump, poppler-utils, procyon-decompiler, r-base-core, sng, sqlite3, squashfs-tools, tcpdump, unzip, xmlbeans, xxd | vim-common, xz-utils, zip

Sample Diffoscope Output

  • Minimal config build (make defconfig; make). Will run diffoscope on a build from Autobuilder config tomorrow.
  • Builds run about 10 minutes apart.
  • Moved first build to target, and rerun. Then run diffoscope target-1 target > diff.txt
  • diffoscope log: https://paste.ubuntu.com/p/VpMbW4qQQP/
  • Except for a time record in the busybox binary, all other differences seem to be only timestamps of file generation.

Planning

  • Week 20: study how yocto does it
  • Week 21: ...
  • Week 22: do two builds in autobuild-run script

Progress Journal

  • 06/06/2019:
    • Setup Gitlab account to track issues and progress
    • Pushed dev branch to Gitlab, as well as re-spun commits and pushed
  • 07/06/2019:
    • Submitted v2 patches to mailing list
    • Submitted patch to enable BR2_REPRODUCIBLE
    • Started evaluating reprotest and its working
  • 08/06/2019:

GSoC Proposal

The proposal PDF can be found here: PDF