Table of Contents

Kernel Compilation Steps

This document outlines the complete build pipeline that transforms C# kernel code into a bootable ISO image using .NET NativeAOT compilation, custom IL patching, and native code generation.

Compilation Flow Chart

flowchart TD
    CS[C# Source Code] --> ROSLYN[Roslyn Compiler]
    PLUGS[Plug Definitions] --> ANALYZER[Cosmos.Build.Analyzer.Patcher]
    ANALYZER -.-> |Validates| ROSLYN
    ROSLYN --> IL[IL Assembly]

    subgraph "Cosmos.Build.Patcher"
        PATCHER[IL Patcher]
        PATCHER --> |cosmos.patcher| PATCHED[Patched Assemblies]
        PATCHED --> COSMOS_REF["$(IntermediateOutputPath)/cosmos/ref/"]
        PATCHED --> COSMOS_ROOT["$(IntermediateOutputPath)/cosmos/"]
    end
    IL --> PATCHER
    PLUGS --> PATCHER

    subgraph "Cosmos.Build.Ilc"
        ILC[NativeAOT Compiler]
        ILC --> |ilc| NATIVE["Native Object (.o)"]
        NATIVE --> COSMOS_NATIVE["$(IntermediateOutputPath)/cosmos/native/"]
    end
    COSMOS_REF --> ILC
    COSMOS_ROOT --> ILC

    subgraph "Cosmos.Build.Asm"
        ASM_BUILD[YASM Compiler]
        ASM_BUILD --> |yasm -felf64| ASM_OBJ["Assembly Objects (.obj)"]
        ASM_OBJ --> COSMOS_ASM["$(IntermediateOutputPath)/cosmos/asm/"]
    end
    ASM_SRC["Assembly Files (.asm)"] --> ASM_BUILD

    subgraph "Cosmos.Build.GCC"
        GCC_BUILD[GCC Compiler]
        GCC_BUILD --> |gcc/x86_64-elf-gcc| C_OBJ["C Objects (.obj)"]
        C_OBJ --> COSMOS_COBJ["$(IntermediateOutputPath)/cosmos/cobj/"]
    end
    C_SRC["C Source Files (.c)"] --> GCC_BUILD

    subgraph "Cosmos.Build.Common"
        LINK[Link Target]
        LINK --> |ld.lld| ELF["ELF Binary ($(OutputPath)/$(AssemblyName).elf)"]
        ELF --> FINAL_ISO[BuildISO Target]
        FINAL_ISO  --> |xorriso + Limine| ISO_OUT["$(OutputPath)/cosmos/$(AssemblyName).iso"]
        ISO_OUT --> |PublishISO| PUBLISH["$(PublishDir)/$(AssemblyName).iso"]
    end
    
    COSMOS_NATIVE --> LINK
    COSMOS_ASM --> LINK
    COSMOS_COBJ --> LINK
    LINKER_SCRIPT["linker.ld"] --> LINK
    LIMINE_CONF["limine.conf"] --> FINAL_ISO

    style CS fill:#e1f5e1
    style ASM_SRC fill:#e1f5e1
    style C_SRC fill:#e1f5e1
    style PLUGS fill:#e1f5e1
    style LINKER_SCRIPT fill:#e1f5e1
    style LIMINE_CONF fill:#e1f5e1
    
    style PUBLISH fill:#ffe1e1

Prerequisites

Tool Purpose Required Version
.NET SDK Core compilation 9.0.200+
YASM Assembly compilation Latest
ld.lld ELF linking LLVM toolchain
xorriso ISO creation Latest
gcc/x86_64-elf-gcc C compilation Cross-compiler on Windows

Key Components

Example Project

Reference implementation: examples/DevKernel/DevKernel.csproj

Output Summary

Stage Output Path Content
Patching $(IntermediateOutputPath)/cosmos/ Main patched assembly
Patching $(IntermediateOutputPath)/cosmos/ref/ Reference assemblies
NativeAOT $(IntermediateOutputPath)/cosmos/native/ Native object files (.o)
Assembly $(IntermediateOutputPath)/cosmos/asm/ YASM objects (.obj)
C Code $(IntermediateOutputPath)/cosmos/cobj/ GCC objects (.o/.obj)
Linking $(OutputPath)/$(AssemblyName).elf Linked ELF kernel
ISO $(OutputPath)/cosmos/$(AssemblyName).iso Bootable ISO image
Publish $(PublishDir)/$(AssemblyName).iso Published ISO
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