AppRuntime

Portable Cross-Platform Swift App Runtime.

A multi-architecture app bundle format and sandboxing launcher for Linux appliance systems (Buildroot). One bundle carries binaries for several architectures; the runtime picks the best one for the host — falling back to 32-bit compatibility or box64/box86 translation — and launches it isolated in its own namespaces.

Components

AppRuntime	Library: manifest model, architecture selection, bundle loading and resource lookup. Corelibs-free (FoundationEssentials only).
bundle-runtime	Launcher: resolves a bundle, selects an architecture, and execs it inside a sandbox.
CBundleRuntime	C shim for namespaces, mounts, pivot_root, prctl, and seccomp.

Bundle layout

com.example.myapp.app/
├── manifest.json
├── bin/<arch>/myapp        arm64, armv7, armv6, armv5, x86_64, i386
├── lib/<arch>/             optional: only libraries the OS lacks
├── resources/              optional
├── run.sh                  optional: launch without the runtime
└── icon.png

Bundles are authored as directories and shipped as squashfs images, optionally made self-executing like an AppImage.

Usage

bundle-runtime com.example.myapp        # by identifier
bundle-runtime /path/to/bundle.app      # by path

Run as root for the full sandbox with a per-app uid; unprivileged launches sandbox via user namespaces instead.

Documentation

• Bundle format specification — layout, manifest, architecture selection, packaging.
• Sandbox — isolation model, capabilities, seccomp, and how to verify it on hardware.

Examples

examples/ contains build scripts that package real apps as bundles, cross-compiled against a Swift SDK sysroot: Celeste Classic (ccleste) and Nanosaur 2.

Building

With SwiftPM, for development:

swift build
swift test

swift build --swift-sdk aarch64-unknown-linux-gnu -c release

CMake (cross-compile and install)

Use CMake to build for the target system and install: AppRuntime installs as a shared library (libAppRuntime.so) and bundle-runtime as an executable. The Swift language requires the Ninja generator.

cmake -B build -G Ninja \
  -DCMAKE_TOOLCHAIN_FILE=cmake/linux.toolchain.cmake \
  -DAPPRUNTIME_ARCH=arm64 \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_INSTALL_PREFIX=/usr

cmake --build build && DESTDIR=/path/to/rootfs cmake --install build

Option	Default	Meaning
APPRUNTIME_ARCH	arm64	Target: arm64, x86_64, armv7, i386
APPRUNTIME_SYSROOT	Swift SDK sysroot for the arch	Override the target sysroot
APPRUNTIME_TOOLCHAIN_BIN	~/.swiftly/bin	Directory holding clang/swiftc
APPRUNTIME_BUILD_LAUNCHER	ON	Build bundle-runtime (Linux only)
BUILD_SHARED_LIBS	ON	Build the library shared rather than static

Installed layout:

usr/bin/bundle-runtime
usr/lib/libAppRuntime.so -> libAppRuntime.so.1 -> libAppRuntime.so.1.0.0
usr/lib/swift/AppRuntime/AppRuntime.swiftmodule
usr/lib/cmake/AppRuntime/            find_package(AppRuntime) support

For Buildroot, point a package recipe at this CMakeLists with the target sysroot and DESTDIR set to the staging tree.