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 2.17–2.44 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. The 2.19 provider uses the same builder; it adds no new versioned interfaces on x86_64, so it reuses the existing boundary tests. The 2.20 provider also builds unchanged; it adds no interfaces but records measured default and IFUNC changes, such as libpthread's vfork becoming compatibility-only. The 2.21 provider completes 2.17–2.22; its new fixture checks that sigvec, compatibility-only from 2.21, no longer links for new code. Every release in the pinned ABI lists now has a provider: see the provider index for each release's builder, exhaustive results, and what changes for users (for example, every executable built with a 2.34 or later provider requires glibc 2.34).

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 is the Cargo subcommand built on these crates: it prepares the 2.17–2.44 providers itself (see its user guide).

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. The default provider-sources feature adds glibc-provider-sources (glibc's sources and headers, LGPL-2.1-or-later, and Linux UAPI headers) for source mode. Build and tests require no Zig; the only dependencies are those two crates.

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
libc-abi libgcc stub --output /path/to/new-dir   # link-only libgcc_s.so.1 sources, GCC 4.8.5's interface
libc-abi glibc libraries --release 2.28 --input /path/to/lib64 > libraries.tsv
libc-abi provider prepare --glibc 2.28          # a link provider, built locally; prints its descriptor
libc-abi provider list

libc-abi provider prepares glibc link providers (stubs, startup objects, nonshared archives, headers) for cargo-libc's --provider in a cache. The default source mode compiles the recorded glibc sources of glibc-provider-sources with the host's GCC, offline, and verifies every object against the qualified container build; container mode runs that build locally. Using glibc providers explains when to choose each mode, the cache, and offline and air-gapped use; the design is in PROVIDER-DELIVERY.md.

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.