Liella

Liella is an innovative clean-room implementation of the GNU C library (glibc) 2.39 ABI tailored specifically for x86-64 Linux, developed using Rust. The project aims to deliver a library that accurately replicates glibc's symbols, calling conventions, data layouts, and versioning as outlined in over 3,900 names. This allows programs compiled against glibc to function seamlessly with Liella, all while adhering to a functional specification detailed in glibc-functional-spec.md.

Current Development Status

Liella is currently a public work in progress, meaning it is still under active development and not yet suitable for production use. Specific limitations include:

• Inability to run typical programs: The dynamic loader (ld-linux) has yet to be implemented, barring the execution of many dynamically linked programs on Linux.
• Not a direct glibc replacement: The project has yet to demonstrate the capability to run unmodified glibc-linked binaries, which is a key objective.
• Pending security audits: A security audit is planned following completion of project phase 15.
• Rapid changes: Ongoing modifications to interfaces, behavior, and build processes occur without prior notice, lacking release branches or compatibility guarantees.

Project Development Phases

The project operates through various phases, with the current implementation status as follows:

Repository Structure

The repository contains several essential components:

• glibc-functional-spec.md and spec/: Acts as the primary specification contract containing ABI data.
• csys/: Contains C syscall layer, system-call wrappers, and assembly primitives.
• crates/: The core Rust library, prohibiting unsafe code, with specifications for operations needing safe handling.
• implementation-plan.md and plan/: Outline the architectural development, phases, and decision-making styles employed.

Usage Example

For developers working with Liella, the following commands can be executed to manage the library effectively:

cargo xtask stubs             # Regenerate test stubs from the specification
cargo xtask so                # Build libc.a, libc.so.6, and liella-crt1.o into target/liella/
cargo xtask test              # Execute the full test suite
cargo xtask affected --list   # List affected tests based on changes

To delve deeper into customization and development tips, refer to the CONTRIBUTING.md file and the code map located in docs/codemap/README.md.

Clean-room Development Approach

Liella's development is grounded in a clean-room methodology, ensuring that the implementation originates entirely from derived documentation rather than from glibc's source code. This effort is documented thoroughly to maintain transparency and integrity throughout the project's evolution.

Additional Resources

To further explore the architecture of Liella, documentation is provided across multiple areas:

• docs/architecture.md: Overview of system architecture.
• docs/benchmarks.md: Insights on performance compared to glibc.
• docs/differences-from-glibc.md: Explanation of deliberate design choices and their implications.
• docs/interfaces.md: Details on various interaction methods with Liella.
• docs/toolchain.md: Comprehensive build parameters and commands.

Liella represents a significant step toward modernizing the implementation of core libraries while maintaining compatibility and performance benchmarks against established standards.