linux-abi-tools

ABI data and tools for targeting older Linux systems from Rust: which libc interfaces and which kernel syscalls a selected target provides. Formerly libc-abi-tools; renamed on 2026-10-10 when kernel-abi-tools joined it.

Workflows explains which tool answers which question: building against an older glibc, inspecting a binary, and running it under an older kernel with a local seccomp filter (no root) or in a container. It also shows how each maps onto cargo-libc. The crates are published to crates.io only; see Releasing.

Each crate is std-only. cargo in the root acts on libc-abi-tools unless given --workspace or -p.

libc-abi-tools

Current glibc coverage lists each library, test stage, qualified input profile, and remaining runtime/architecture work. See CI and release artifacts for Rust/Clang roles, the shared preparation stage, and planned version-suffixed target selection.

Browse versioned glibc interfaces, release differences, and the history/conformance plan. These references distinguish new defaults from retained compatibility interfaces and link to input provenance.

The experimental glibc 2.17/2.18/2.22 provider contract connects all eight generated stub libraries to the companion cargo-libc coordinator. CI targets Rust 1.99.0 and Clang 21/24; the roadmap tracks each vendored version's remaining real input and runtime setup. The 2.22 experiment includes a source-built GNU runtime and an explicit 2.22 symbol test; SLES qualification remains separate. The 2.18 provider fills the first gap with pinned source inputs, exhaustive linking, and pthread default-attribute boundary tests.

Target libc versions beyond your host.

Rust tools for collecting and inspecting libc ABI metadata, starting with x86_64 Linux glibc 2.17+. The ABI lists come from the GNU C Library itself, collected from glibc's signed release tags by glibc-abilists. The project was inspired by, and parts of its code adapted from, Zig's libc ABI tools; credit to the Zig contributors for the idea and design. See NOTICE.md for complete attribution and the separate code and data licenses.

The companion cargo-libc coordinates Cargo builds with an existing sysroot or the experimental 2.17/2.18/2.22 providers.

What works today

• Parse historical grouped ABI lists and modern per-line versioned lists.
• Load exact release snapshots for eight libraries: m, c, ld, resolv, pthread, dl, rt, and util.
• Export deterministic TSV or query one symbol across those libraries.
• Preserve historical symbol versions and object sizes; recognize explicit TLS entries when present. Absolute version-node markers and GCC_* entries are skipped.
• Collect the selected ABI files from a clean glibc source checkout at an exact glibc-MAJOR.MINOR tag, with source commit and license files.
• Collect defined dynamic-symbol evidence directly from ELF64 x86_64 shared libraries: SONAME, versions/defaults, binding, visibility, IFUNC/TLS kinds, 64-bit sizes, and observed shared ranges. See ELF metadata.

The ABI lists for glibc 2.17 through 2.44 are compiled in from the glibc-abilists crate (default bundled-glibc-data feature; LGPL-2.1-or-later). Each comes unmodified from glibc's release tag, with the tag's signature check and the file's blob id and SHA-256 recorded there. A release label is not a claim of tested runtime compatibility. Every release is covered by parser tests. To leave the LGPL data out, build with default-features = false and pass --data DIR. Build and tests require no Zig; the only dependency is glibc-abilists.

Build and try it

Requires Rust/Cargo 1.90+; collection also requires Git. Run from this repository:

cargo test --locked
cargo run --locked -- glibc snapshot --release 2.22 --symbol memcpy

Output:

release target                   library symbol version       kind size
2.22    x86_64-unknown-linux-gnu   c       memcpy GLIBC_2.2.5   F    -
2.22    x86_64-unknown-linux-gnu   c       memcpy GLIBC_2.14    F    -

The real output uses tabs. Omit --symbol to export the whole release. No matching symbol produces a header-only result. Unknown/missing releases fail; the tool never substitutes a newer release.

cargo install --path . --locked
libc-abi glibc snapshot --release 2.17 > glibc-2.17.tsv
libc-abi glibc export-data --output /path/to/glibc-data       # files + SOURCE.tsv + COPYING.LIB
libc-abi glibc snapshot --data /path/to/glibc-data --release 2.17
libc-abi glibc collect --source /path/to/glibc-checkout --output /path/to/new-data
libc-abi glibc elf --input /path/to/target/libc.so.6 > libc-elf.tsv

The installed executable carries the ABI lists; --data reads a directory with the same layout instead (required when built without bundled-glibc-data). Collection refuses an existing output release and validates the inputs before writing. An I/O failure during writing can leave a partial new directory; inspect it before retrying. Source tags identify a checkout, not its authenticity: use a trusted source repository.

Why exact release snapshots?

Symbols can move between libraries. The newer file may retain an old symbol version while moving its library membership; inferring all history from the latest file would put it in the wrong library for older targets. Tests cover pthread_sigmask moving to libc in 2.32 and startup changes in 2.34.

glibc 2.17 is a target release floor, not a symbol-version filter. GLIBC_2.2.5 still belongs in a 2.17 or 2.22 snapshot.

What comes next

Compact cross-release consolidation, Zig abilists binary interoperability, a packaged release SDK and additional provider versions are future work. ABI lists alone do not identify every default-version alias, binding/visibility detail, or TLS property needed for a complete generator. Headers, startup code, nonshared objects, compiler runtimes, and oldest-target runtime tests are separate requirements. No glibc implementation is included.

See ROADMAP.md, ARCHITECTURE.md, and VALIDATION.md.

For a hands-on comparison of obtaining real glibc inputs versus building them from source, and a verified two-function generated libc experiment, see the two-path C example. The expanded emitter experiment additionally tests both memcpy versions, object copy-relocation, IFUNC, TLS, and observed alias storage. The full-library follow-up generates all pinned public glibc 2.17 exports in the eight selected libraries and passes C/Rust runtime checks.