deepseek-harness/native/landlock-run/docs/cli-contract.md

CLI contract: landlock-run

This file pins the launcher's externally observable behavior — the cross-repo compatibility surface between the binaries and every consumer. Consumers interact with it only through the entry package (launcherPath/probe/grantArgs); changing anything below requires a version bump for the whole package family and a note in the release notes.

Invocation grammar

landlock-run [--ro <path>]... [--rw <path>]... -- <argv>...
landlock-run --probe

• --ro <path>: grant read + execute beneath <path>.
• --rw <path>: grant full filesystem access beneath <path> (every access the negotiated kernel ABI can govern).
• Everything not granted is denied — Landlock rulesets are allow-lists.
• A grant on a non-directory keeps only its file-compatible access bits (this is how a --rw /dev/null grant works).
• --: mandatory separator; everything after it is the command argv, exec'd via execvp with the launcher's environment unchanged.
• --probe: mutually exclusive with grants and a command.
• No other flags, no environment-variable inputs.

Exit codes

• 125 (LAUNCHER_FAILURE_EXIT): every launcher-level failure — usage error, kernel that cannot enforce Landlock, unopenable grant root, failed exec. The wrapped command was NOT run (fail-closed; the one exception is exec itself failing after restriction, which by definition never ran the command either).
• Any other status: the wrapped command's own exit status, passed through unchanged.
• --probe: 0 when the kernel enforces (fully or partially), 125 otherwise.

Report lines

• Probe success prints exactly one stdout line: landlock: fully enforced or landlock: partially enforced (older ABI). The entry package's probe() maps these to full/partial; a non-zero probe exit maps to unusable.
• A confined run under a partial-ABI kernel prints one stderr line landlock-run: partial enforcement (older Landlock ABI) and proceeds — still confined for everything the kernel supports.
• Every fatal error prints one stderr line prefixed landlock-run: before exiting 125.

Confinement semantics

The launcher sets no_new_privs, installs the ruleset on itself, and execs the command; the ruleset is inherited across execve, so every descendant process is equally confined. The ruleset governs the filesystem accesses of the kernel's negotiated Landlock ABI (up to ABI 5); accesses newer than the running ABI are not governed and are the difference between full and partial.