feat(qemu): provision Linux runtime libraries instead of requiring apt - #1352
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The Espressif QEMU tarballs ship only the emulator binary, its ROM blobs
and a static libfdt.a. The binaries carry no RPATH/RUNPATH and link five
non-glibc libraries: libpixman-1, libgcrypt, libSDL2, libz and libslirp.
A stock ubuntu-24.04 (what ubuntu-latest resolves to) has none of
libslirp/libSDL2/libpixman, so qemu-system-xtensa and
qemu-system-riscv32 die at exec with
error while loading shared libraries: libslirp.so.0
Until now the only fix was an apt-get install step outside fbuild —
exactly the kind of external bootstrap fbuild exists to remove, and the
cause of FastLED/FastLED's red QEMU badges.
fbuild now provisions the libraries itself:
- `ci/build_qemu_linux_runtime.py` walks `ldd` over both real QEMU
binaries in ubuntu:22.04 and archives the full transitive closure
minus the glibc family and the loader (52 libraries, 5.1 MB zstd).
Closure-walked rather than hand-listed: Ubuntu's SDL2 drags in X11,
Wayland and PulseAudio, and libslirp pulls glib — a curated list rots
the first time upstream adds a dependency. Built on 22.04 so the
bundle's glibc floor (2.35) covers every host fbuild targets.
- `esp_qemu_runtime` downloads that bundle from the
qemu-linux-runtime-v1 release, sha256-pinned, and exposes the lib dir.
- QEMU resolution probes `--version` first and only fetches the bundle
when the host genuinely cannot start QEMU, so hosts that already carry
the libraries download nothing and keep their own copies unshadowed.
- The emulator spawn path prepends the bundle to LD_LIBRARY_PATH, the
Linux twin of the existing Windows PATH hydration.
Also corrects `qemu_validate_bundled_libs`' doc comment, which claimed
the tarball ships lib/libslirp.so.0 with an $ORIGIN rpath. It does not —
`lib/` holds only a static libfdt.a, which is why that check passed
while QEMU could not start.
Tests: `crates/fbuild-toolchain/tests/qemu_linux_runtime.rs` resolves
both QEMU binaries and asserts they start during invocation, run by
`.github/workflows/qemu-linux-runtime.yml` on a stock ubuntu-latest with
deliberately no apt preinstall step. Unit tests cover the probe's exit-127
classification and that the bundle actually reaches LD_LIBRARY_PATH.
aarch64: the bundle must be built on an ubuntu-22.04-arm runner
(`qemu-runtime-bundle.yml`) because Docker Desktop's arm64 emulation
cannot run dpkg's maintainer scripts. Until it is published, linux-arm64
hosts get an explicit error naming the distro packages to install.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review. Important Approval pendingCodeRabbit has no unresolved comments, but it could not review the latest commit because the review limit was reached. Follow the review guidance in this comment to continue. 📝 WalkthroughWalkthroughChangesQEMU Linux runtime support
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🔵 Low · up to The PR changes Linux QEMU execution to use a lazily provisioned bundled runtime, but an incomplete cached bundle can still be accepted and leave QEMU unable to start when the remaining libraries are needed. This is a bounded runtime-availability risk that should have explicit owner follow-up, but it does not otherwise require blocking the merge. Sequence Diagram(s)sequenceDiagram
participant EspQemu
participant QemuLinuxRuntime
participant QEMU
EspQemu->>QemuLinuxRuntime: ensure_qemu_can_start(project_dir)
QemuLinuxRuntime->>QEMU: probe --version
QEMU-->>QemuLinuxRuntime: startup or missing-library result
QemuLinuxRuntime->>QemuLinuxRuntime: install and validate runtime bundle
QemuLinuxRuntime->>QEMU: probe --version with bundled libraries
QEMU-->>EspQemu: startup result
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
✨ Finishing Touches 💡 2📝 Generate docstrings 💡
🛠️ Fix failing CI checks 💡
🧪 Generate unit tests (beta)
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…edgers Keeps esp_qemu.rs under the 1000-LOC gate and puts the probe, the bundle-provisioning fallback and their tests next to the package they drive. Also registers the new target_os occurrences in both platform-boundary ledgers, and softens qemu_validate_bundled_libs' error text, which still read as "your cache is corrupt" for what is purely an extraction-completeness check. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Inline comments:
In @.github/workflows/qemu-linux-runtime.yml:
- Line 39: Update the test job using actions/checkout@v6 to set
persist-credentials to false, and add job-level permissions with contents: read
(or the minimum permissions required). Preserve the existing checkout and test
behavior.
In @.github/workflows/qemu-runtime-bundle.yml:
- Around line 6-8: Update the runtime bundle workflow’s build environment to
target glibc 2.17, matching the Linux wheels’ manylinux_2_17 compatibility
floor, and ensure the generated bundle does not require GLIBC_2.34.
Alternatively, explicitly define and enforce glibc 2.34 as the minimum runtime
version throughout the workflow.
In `@ci/build_qemu_linux_runtime.py`:
- Around line 109-159: Update the native build staging flow around the bundle
paths and OUT_NAME handling to create a private restrictive temporary directory
with mktemp -d, use that directory for all intermediate files and generated
outputs instead of predictable /tmp paths, and register trap cleanup so the
directory is removed on exit or failure. Preserve the manifest and final
artifact generation behavior while preventing symlink-controlled privileged
writes.
In `@crates/fbuild-daemon/src/handlers/emulator/tests_process.rs`:
- Line 220: Update the real-QEMU fixture setup around run_qemu_process to pass
Some(&project_dir) instead of None, matching QemuRunner so the resolved runtime
bundle directory can be used for library-path configuration.
In `@crates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rs`:
- Around line 103-105: Update EspQemuRuntime::is_installed to verify every
declared direct runtime-library dependency, rather than only SENTINEL_LIB,
before accepting the cached bundle. Ensure ensure_lib_dir reinstalls when any
required library is missing, and add a regression test covering libslirp.so.0
present with another required library absent.
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.github/workflows/qemu-linux-runtime.yml.github/workflows/qemu-runtime-bundle.ymlci/README.mdci/build_qemu_linux_runtime.pycrates/fbuild-daemon/src/handlers/emulator/qemu_deploy.rscrates/fbuild-daemon/src/handlers/emulator/runners.rscrates/fbuild-daemon/src/handlers/emulator/shared.rscrates/fbuild-daemon/src/handlers/emulator/tests_process.rscrates/fbuild-toolchain/src/toolchain/esp_qemu.rscrates/fbuild-toolchain/src/toolchain/esp_qemu_runtime.rscrates/fbuild-toolchain/src/toolchain/mod.rscrates/fbuild-toolchain/tests/README.mdcrates/fbuild-toolchain/tests/qemu_linux_runtime.rsdylints/enforce_platform_boundary/src/baseline.txt
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`ban_std_pathbuf` denies raw `std::path::PathBuf` in new files, so the runtime bundle exposes `NormalizedPath` and keeps its install/lookup methods inherent rather than implementing `Package` (whose signature is PathBuf-typed). Nothing consumed it as a `dyn Package`. Also regenerates ci/platform_boundary_research.tsv after the module split. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Review follow-ups on the runtime bundle: - Build the bundle in ubuntu:20.04 instead of 22.04. The bundled libraries inherit the build image's glibc floor, and 22.04 pushed it to GLIBC_2.34 — above the GLIBC_2.30 the Espressif QEMU binaries themselves need, so the bundle could lock out a host that could otherwise run QEMU. A 20.04 closure needs exactly GLIBC_2.30, making the bundle never the binding constraint. It is also smaller: 43 libraries / 4.2 MB, down from 52 / 5.1 MB. - Stage the build in a private `mktemp -d` with trap cleanup and hand the artifacts over through a fresh root-owned drop directory. The payload runs as root, so fixed /tmp names were pre-creatable as symlinks by a local attacker. - Drop `--native`: both arches now build in the container, and the runner only supplies the CPU architecture (aarch64 needs a native arm64 runner because dpkg's maintainer scripts fail under emulation). - Workflows: least-privilege `permissions:` and `persist-credentials: false`. - Pass the project dir in the real-QEMU fixture so the spawn exports the bundle on a host that needed provisioning. Re-verified on bare ubuntu:24.04: qemu-system-xtensa exits 127 without the bundle and 0 with it; max required symbol version is GLIBC_2.30. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The deterministic inventory records line numbers, so it drifts on any edit inside a file that carries a boundary occurrence. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The ledger row count is pinned in ci/test_enforce_platform_boundary.py. The QEMU runtime bundle adds three target_os gates in esp_qemu_runtime.rs plus the Linux-only integration test, and moves the two pre-existing target_os gates out of esp_qemu.rs. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
…bundle `is_installed()` checked one sentinel library, so a partially-restored cache (a CI cache saved mid-extract, say) counted as complete. The install was then never repaired, and the follow-up probe failed with "cannot start even with the bundle applied" — an unrecoverable error for a recoverable state. Both the cache check and the post-extract validation now require all five libraries the QEMU binaries link directly, and the error names the ones that are actually missing. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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…lf (#3981) The QEMU workflows installed libsdl2-2.0-0 and libslirp0 because the Espressif QEMU binaries link them and ubuntu-latest (24.04) ships neither, so the emulator died at exec with "error while loading shared libraries: libslirp.so.0". That apt step was a bootstrap outside fbuild for something fbuild owns. fbuild 2.5.20 provisions them itself: it probes the emulator and, only on a host that cannot start it, downloads a sha256-pinned bundle of the full non-glibc dependency closure and exports it on LD_LIBRARY_PATH (FastLED/fbuild#1352/#1355). Hosts that already have the libraries fetch nothing and keep their own. Removing the step is also what keeps the emulation lanes honest: with no apt preinstall, a regression in fbuild's provisioning path shows up here as a red badge instead of being masked. Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Problem
Espressif's QEMU tarballs ship the emulator binary, ROM blobs and a static
libfdt.a— no shared libraries — and the binaries carry no RPATH/RUNPATH. They dynamically link five non-glibc libraries:A stock
ubuntu-24.04(whatubuntu-latestresolves to) has none of libslirp / libSDL2 / libpixman, so bothqemu-system-xtensaandqemu-system-riscv32die at exec:This is what turned every FastLED QEMU badge red. The only fix available to callers was an
apt-get installstep outside fbuild — the kind of external bootstrap fbuild exists to remove.Note
qemu_validate_bundled_libs' doc comment claimed the tarball shipslib/libslirp.so.0with an$ORIGIN/../librpath. It does not —lib/holds only a staticlibfdt.a. That is why the check passed while QEMU could not start; the comment is corrected here.Fix
fbuild provisions the libraries itself:
ci/build_qemu_linux_runtime.py— walkslddover both real QEMU binaries insideubuntu:22.04and archives the full transitive closure minus the glibc family and the loader (52 libraries, 5.1 MB zstd). Mechanically closed rather than hand-listed: Ubuntu's SDL2 drags in X11/Wayland/PulseAudio and libslirp pulls glib, so a curated list rots on the first upstream dependency change. Built on 22.04 so the bundle's glibc floor (2.35) covers every host fbuild targets. The script self-tests by removing the apt packages and re-running both binaries against the bundle alone.esp_qemu_runtime— downloads that bundle from theqemu-linux-runtime-v1release, sha256-pinned, through the normalPackageBasestaged-install path.--versionfirst and only fetches the bundle when the host genuinely cannot start QEMU. Hosts that already carry the libraries download nothing and keep their own copies unshadowed.LD_LIBRARY_PATH, the Linux twin of the existing Windows PATH hydration.Tests
crates/fbuild-toolchain/tests/qemu_linux_runtime.rs— resolves both QEMU binaries and asserts they start during invocation..github/workflows/qemu-linux-runtime.ymlruns it on a stockubuntu-latestwith deliberately no apt preinstall step; the job logs which of the three libraries the runner is missing so the premise stays visible.LD_LIBRARY_PATH.Verified locally: on bare
ubuntu:24.04,qemu-system-xtensa --versionexits 127 without the bundle and exits 0 withLD_LIBRARY_PATH=<bundle>/lib.aarch64
qemu-runtime-bundle.ymlbuilds both arches; the aarch64 leg needs anubuntu-22.04-armrunner because Docker Desktop's arm64 emulation cannot run dpkg's maintainer scripts. Until that asset is published, linux-arm64 hosts get an explicit error naming the distro packages to install rather than a placeholder checksum.Coordinated with FastLED/FastLED#3964 (the interim apt-step fix, already merged); the FastLED-side follow-up bumps the fbuild pin and deletes that apt step.
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Summary by CodeRabbit
New Features
Bug Fixes
Documentation
Tests