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Rebuilding Arti for Android

tools/arti-build/README.md

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Rebuilding Arti for Android

The four committed libarti_android.so files are built from the official Arti source plus the JNI wrapper in this directory. The supported build path is the pinned Linux container:

bash
tools/arti-build/rebuild-in-container.sh
tools/arti-build/verify-checksums.sh

The container builds all four Android ABIs, verifies the exported JNI symbols and rejects native binaries containing host-specific paths. It then rewrites tools/arti-build/SHA256SUMS; both that manifest and the rebuilt libraries are release inputs.

Pinned inputs

  • TOOLCHAIN.env: Arti tag and commit, stable build epoch, Rust, cargo-ndk, Android NDK, and immutable Debian snapshot
  • rust-toolchain.toml: Rust release and Android targets
  • Cargo.lock: complete Rust dependency graph
  • Dockerfile: digest-pinned Rust base image and checksum-verified NDK archive
  • Cargo.toml and src/lib.rs: JNI wrapper package and source

Rust source paths are remapped to stable virtual paths, incremental compilation is disabled, and SOURCE_DATE_EPOCH is pinned to the value used for the committed libraries.

Updating Arti or the native toolchain

  1. Update the tag, full source commit, stable build epoch, tool versions, archive name, and archive checksum in TOOLCHAIN.env.

  2. Update Cargo.toml if Arti changed its crate features or wrapper version.

  3. Regenerate Cargo.lock against the exact Arti checkout and review every dependency change:

    bash
    tools/arti-build/rebuild-in-container.sh --update-lockfile

  4. Update the digest-pinned base image and rust-toolchain.toml when changing Rust.

  5. Run tools/arti-build/rebuild-in-container.sh twice from clean generated state and confirm tools/arti-build/SHA256SUMS is unchanged.

  6. Run the Android tests and the two-build release comparison described in docs/reproducible-builds.md.

Do not build release native libraries with an unpinned local NDK or Rust toolchain. build-arti.sh deliberately rejects mismatched tool versions.

JNI surface

The wrapper exports the native methods used by ArtiNative:

  • getVersion
  • setLogCallback
  • initialize
  • startSocksProxy
  • stop

The build fails if any expected symbol is absent. The NDK readelf check also reports ELF load-segment alignment for Android's 16 KiB page-size requirement.

References