Fix build reproducibility regression from PR #2136 (musl-cross-make binutils bump) - #2174
Open
tlaurion wants to merge 4 commits into
Open
Fix build reproducibility regression from PR #2136 (musl-cross-make binutils bump)#2174tlaurion wants to merge 4 commits into
tlaurion wants to merge 4 commits into
Conversation
Five changes to make musl-cross-make produce deterministic output: 1. Override BUILD triplet (x86_64-pc-linux-gnu) via config.mak to prevent config.guess from probing the Docker host kernel. Docker shares the host kernel across CI runners; different runners produce different build-system triplets. No prior reproducibility-motivated BUILD pinning found in other musl-cross-make deployments — this is Heads-original. 2. Pass -Wa,--no-pad-sections via CFLAGS to prevent gas from padding section ends to alignment boundaries (gas NEWS 2.27, 2016). No other project uses this flag for reproducibility; the need is specific to gas 2.44 behavior in musl-cross-make. 3. Pass --with-debug-prefix-map=$(pwd)=. to normalize the build directory path embedded in the cross-compiler's debug info. Same technique used by Buildroot (gcc.mk, BR2_REPRODUCIBLE), rust-musl-cross (config.mak), Debian dpkg (-ffile-prefix-map), and Yocto (DEBUG_PREFIX_MAP). Ref: https://reproducible-builds.org/docs/build-path/ 4. Pass --enable-compressed-debug-sections=no to disable zlib debug-section compression (non-deterministic output). Used by Rust CI (crosstool-ng), Microsoft Azure Linux, Fedora binutils.spec, Chromium OS, and Frida. Ref: https://reproducible-builds.org/docs/deterministic-build-systems/ 5. Export SOURCE_DATE_EPOCH from the pinned commit epoch to prevent __DATE__/__TIME__ embedding during the GCC build. Follows the Buildroot fakedate pattern and the spec: https://reproducible-builds.org/specs/source-date-epoch/ Signed-off-by: Thierry Laurion <insurgo@riseup.net>
busybox's scripts/trylink passes -Wl,--gc-sections to ld.bfd. In ld.bfd 2.44 (and through 2.47), the --gc-sections mark-phase traversal depends on the ASLR layout of the linking process. No upstream binutils fix exists. Per the SOURCE_DATE_EPOCH convention, its presence signals that a reproducible build is requested: https://reproducible-builds.org/specs/source-date-epoch/ Changes: - patches/busybox-1.36.1/0004-trylink-reproducible.patch: Patch scripts/trylink to skip -Wl,--gc-sections when SOURCE_DATE_EPOCH is set. - modules/busybox: Pass SOURCE_DATE_EPOCH=0 in busybox_target. Replace 'make install' with direct binary copy + install.sh symlink generation. busybox's install target depends on busybox_unstripped which is FORCE, so 'make install' can trigger a re-link with no SOURCE_DATE_EPOCH. Copying the already-built binary and running applets/install.sh --symlinks avoids this entirely. Follows the same pattern used by Buildroot's fakedate (2016): SDE gates nondeterministic behavior off. No prior art found for SDE-gated --gc-sections disabling; OpenWrt offers per-package gc-sections opt-out but for size reduction, not reproducibility. With the musl-cross-make fix, 67 of 68 tools in tools.cpio are byte-identical. This fixes the last one. Signed-off-by: Thierry Laurion <insurgo@riseup.net>
There was a problem hiding this comment.
Pull request overview
This PR targets build reproducibility for the EOL_t480-hotp-maximized board by eliminating known sources of non-determinism in the musl-cross-make toolchain build and the BusyBox link/install flow, aligning local builds with CI artifacts.
Changes:
- Pin musl-cross-make build settings (BUILD triplet, assembler section padding, debug prefix mapping, debug-section compression) and propagate
SOURCE_DATE_EPOCHinto the toolchain build. - Patch BusyBox
scripts/trylinkto disable--gc-sectionswhenSOURCE_DATE_EPOCHis set to avoid nondeterministic ld.bfd behavior. - Avoid BusyBox re-link during install by copying the built binary and running
applets/install.shdirectly; setSOURCE_DATE_EPOCH=0for BusyBox builds.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| patches/busybox-1.36.1/0004-trylink-reproducible.patch | Disables BusyBox --gc-sections when SOURCE_DATE_EPOCH is set to avoid nondeterministic linking. |
| modules/musl-cross-make | Adds reproducibility-related config (pinned BUILD, no-pad-sections, debug prefix mapping, disables compressed debug sections) and exports SOURCE_DATE_EPOCH into the build. |
| modules/busybox | Forces SOURCE_DATE_EPOCH=0 and changes install to avoid re-linking by using direct copy + applets/install.sh. |
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
tlaurion
changed the title
Collaborator
Author
|
Damn we need StageX. |
tlaurion
force-pushed
the
reproducibility-fixes-v2
branch
2 times, most recently
from
August 3, 2026 02:05
ffb6cf5 to
c543c64
Compare
doc/reproducible-builds.md (new): - Reproducible build practices: musl-cross-make flags, heads_cc flags, kernel flags, prefix overrides, busybox trylink patch, openssl patch - hashes.txt structure: SHA256 of every file inside every cpio, cascade from innermost file -> cpio -> initrd.cpio.xz -> ROM - GIT_HASH in /etc/config explains why tools.cpio differs between commits (documentation-only changes expected to cascade) - Verification procedure: ROM -> payload -> cpio -> file top-down check doc/index.md: regrouped by subject, added missing BOARDS_AND_TESTERS.md, circleci.md, and reproducible-builds.md entries doc/modules.md: added Toolchain Modules section (MUSL_CROSS_ONCE guard, early include ordering, cross-ref to doc/circleci.md) Cross-references added from docker.md, architecture.md, and build-freshness.md to reproducible-builds.md Module comments added to musl-cross-make and busybox following the modules/gpg pattern Removed file:line references throughout — replaced with descriptive references that won't decay when source files change Corrected GIT_HASH documentation (git rev-parse HEAD, not git log --oneline) and --prefix override (modules use --prefix, not --exec-prefix) Signed-off-by: Thierry Laurion <insurgo@riseup.net>
tlaurion
force-pushed
the
reproducibility-fixes-v2
branch
from
August 3, 2026 02:07
c543c64 to
9648246
Compare
Three download improvements: - GNU_SITE = https://ftp.gnu.org/gnu overrides the unreliable ftpmirror.gnu.org (frequently returns 502 Bad Gateway). - DL_CMD = bin/musl-mirror-fetch.sh provides a multi-mirror download wrapper that tries ftp.gnu.org, mirrors.kernel.org, and mirror.math.princeton.edu in order for each GNU tarball. - HEADS_DISABLE_USB=1 + script -qec enables unattended docker builds (HEADS_DISABLE_USB=1 skips USB cleanup needing sudo, script -qec provides a pseudo-TTY for docker_repro.sh's -ti flag). No SOURCES = $(packages) override — packages/x86/ does not yet contain the component tarballs (gcc, binutils, gmp, mpc, mpfr, etc.). Add back once packages/ is seeded and Purism mirrors are populated. Signed-off-by: Thierry Laurion <insurgo@riseup.net>
tlaurion
force-pushed
the
reproducibility-fixes-v2
branch
from
August 3, 2026 02:25
9648246 to
1f6688d
Compare
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Fixes the build reproducibility regression introduced by PR #2136
(commit 3dfec51: musl-cross-make bump to 227df8b), which upgraded
binutils from 2.33.1 to 2.44.
Closes: #2168
Regression
PR #2136 bumped musl-cross-make for CVE fixes, upgrading binutils from
2.33.1 to 2.44. This introduced two independent reproducibility failures:
Cross-compiler (affected gpg-agent): gas 2.44 section
padding, config.guess host kernel probing, debug section compression, and
DATE/TIME embedding caused tools.cpio binaries to build
non-reproducibly between CI and local.
Busybox linker (affects busybox only): ld.bfd 2.44's --gc-sections uses
ASLR-influenced hash tables (no upstream fix through 2.47). Busybox's
scripts/trylink is the only Heads package using this flag.
Fixes
modules/musl-cross-make
modules/busybox + patches/
Documentation
Verification
CI and local builds produce byte-identical hashes for all artifacts
(verified across clean builds and cache-reuse rebuilds at multiple commits).