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🏃 Executables ​

The executable crate defines the native executable contract and the launcher used across Core.

Role ​

  • Defines ExecutableTrait and typed GET_MAIN_FUNCTION command contract.
  • Provides execute(...) orchestration: permission checks, task spawn, and standard stream propagation.

Boundaries ​

  • In scope: executable ABI contract, launch permission logic, standard stream helper type.
  • Out of scope: executable UI/business logic and shell-specific command parsing.

Internal structure ​

  • traits.rs: ExecutableTrait, ExecutableWrapper, mount_executables!, command definition.
  • lib.rs: launch path (execute) + execution permission helpers.
  • standard.rs: Standard abstraction (open, duplicate, read_line, close).
  • arguments_parser.rs: argument helper support for executable crates.
  • error.rs: launcher-level error type.

Runtime interaction ​

  1. Executables are mounted as character devices exposing GET_MAIN_FUNCTION.
  2. execute(path, args, standard, spawner) fetches VFS statistics and checks execute permissions.
  3. It opens executable file and requests main function via control command.
  4. It spawns a task and calls main with provided Standard and argument vector.
  5. It returns task::JoinHandle<isize> to allow join/wait by caller.

Dependency model ​

Failure semantics ​

  • Permission denial is explicit (Error::PermissionDenied).
  • Missing main entrypoint yields FailedToGetMainFunction.
  • Task spawn or VFS failures are mapped into crate error variants.
  • Executable runtime errors are converted to negative isize task return values in spawned task closure.

Extension points ​

  • New executable crates implement ExecutableTrait and mount through ExecutableWrapper or mount_executables!.
  • building feature gates additional build-time support without changing runtime core path.

Contract vs implementation ​

  • Contract: executable = mounted character device that answers GET_MAIN_FUNCTION and receives Standard + Vec<String>.
  • Current implementation: launcher uses VFS metadata + users/group checks and task spawn under current task context.

Limitations and trade-offs ​

  • Contract is intentionally narrow (main only), simplifying dispatch but leaving richer lifecycle hooks to higher layers.
  • setuid-style override logic is constrained and permission-checked at launch time.

References ​