OrlixKernel

OrlixKernel is the Linux-shaped runtime substrate for Orlix on iOS. It is a virtual kernel/runtime inside one iOS app sandbox whose job is to present Linux-oriented source and runtime semantics while keeping iOS host mediation private.

Status

This repository is under active virtualization and proof work. It is not public drop-in compatibility proof for arbitrary Linux userspace yet. Current proof in this repo is limited to:

• LinuxKernel syscall-facing semantic tests for selected subsystems
• HostBridge seam tests for private OrlixHostAdapter/internal/ios/** mediation
• Linux UAPI / ABI compile smoke tests for vendored headers
• canonical iOS Simulator build-for-testing and shared-scheme XCTest execution through XcodeGen + Xcodebuild

Build Truth

XcodeGen and the generated Xcode project are the only build truth.

Canonical flow:

rtk xcodegen generate --project .
rtk xcodebuild -list -project OrlixKernel.xcodeproj
rtk xcodebuild build-for-testing -project OrlixKernel.xcodeproj -scheme OrlixKernel-6.12-arm64 -sdk iphonesimulator -configuration Debug -destination 'platform=iOS Simulator,name=iPhone 17'
rtk xcodebuild test-without-building -project OrlixKernel.xcodeproj -scheme OrlixKernel-6.12-arm64 -sdk iphonesimulator -configuration Debug -destination 'platform=iOS Simulator,name=iPhone 17'

Canonical project surface:

• Targets:
  • OrlixKernel
  • OrlixHostAdapter
  • OrlixKernelTests
  • OrlixHostAdapterTests
• Scheme:
  • OrlixKernel-6.12-arm64

swift build, CMake, Make, package manifests, and ad hoc build flows are not authoritative for this repo.

Repository Layout

Current top-level ownership is organized around the implemented subsystems in this tree:

• OrlixKernel/kernel/ — process/task, signal, pid, wait, cred, time, sync, init, resource, random, sys, network ownership
• OrlixKernel/fs/ — VFS, fdtable, open/read/write, stat, fcntl, ioctl, exec, path, mount, inode, readdir, eventpoll ownership
• OrlixKernel/runtime/native/ — native command registry surface
• OrlixHostAdapter/internal/ios/ — private host mediation seams only
• OrlixKernelTests/ — Linux-facing syscall and contract proof
• OrlixHostAdapterTests/ — private host-bridge seam proof
• third_party/linux/6.12/arm64/uapi/include/ — vendored Linux UAPI truth
• project.yml — authoritative XcodeGen project specification

Architecture Direction

OrlixKernel does not define its Linux-facing contract by delegating host semantics directly. Its direction is a Linux-shaped virtual runtime with private iOS mediation. That includes:

• virtual task/process identity
• virtual process groups and sessions
• virtual credentials
• Linux-shaped signal ownership and semantics
• Linux-shaped VFS, fdtable, and exec ownership
• virtualization of unsupported host behavior where possible inside Orlix boundaries

Darwin and iOS APIs are private implementation details and must not define the Linux-facing contract.

Linux Header Policy

Vendored generated Linux headers from upstream Linux are the only Linux header truth in this repo.

Location:

• tuple root: third_party/linux/6.12/arm64/
• UAPI: third_party/linux/6.12/arm64/uapi/include

Allowed include forms:

• #include <linux/...>
• #include <asm/...>
• #include <asm-generic/...>

Forbidden include forms:

• path traversal into vendored headers
• includes containing third_party/linux/
• includes containing 6.12
• includes containing arm64

Test Layering

This repo currently contains two XCTest proof layers plus Linux UAPI compile smoke:

1. LinuxKernel proof

   • uses syscall-facing contracts and Linux-visible runtime assertions
   • keeps Linux semantics proof out of OrlixHostAdapter/internal/ios/**
   • is the primary subsystem proof for Linux-facing behavior

2. HostBridge proof

   • verifies private OrlixHostAdapter/internal/ios/** mediation seams only
   • may use host APIs to prove host-mechanics contracts
   • does not count as Linux semantics proof

3. Linux UAPI / ABI compile smoke

   • uses vendored Linux UAPI headers through canonical include paths
   • proves header/constants/types resolution only
   • does not prove runtime behavior

Current files:

• OrlixKernelTests/SignalTests.m — LinuxKernel semantic test
• OrlixKernelTests/TaskGroupTests.m — LinuxKernel semantic test
• OrlixKernelTests/CredentialTests.m — LinuxKernel semantic test
• OrlixKernelTests/LinuxUAPICompileSmoke.c — Linux UAPI / ABI compile smoke
• OrlixHostAdapterTests/HostBridgeSmokeTests.m — HostBridge seam test

True public drop-in Linux userspace compatibility proof is not part of this XCTest tranche.

Current Constraints

OrlixKernel runs inside one iOS app sandbox. Host limitations must be virtualized where possible rather than leaked into the Linux-facing contract. Some subsystems remain incomplete or partial; incomplete behavior should be treated as implementation work in progress, not as proof of finished Linux compatibility.

Primary References

• AGENTS.md — development rules for syscall ownership, _impl() usage, build proof, and error handling
• docs/SUBSTRATE_CONTRACT.md — current architecture and ownership contract