Source Tree

A map of the repository. The short version: src/ is Darwin, nix/ is everything around it, and tools/ is what the host needs to build Darwin at all.

src/Kernel

src/Kernel/xnu is the kernel. Next to it are libkmod, libfirehose_kernel, fbsdkpi and src/Kernel/Extensions, which holds the kexts. They fall into groups:

• Platform: PDACPIPlatform (built on uACPI), AppleI386GenericPlatform, AppleAPIC, AppleI386PCI, IOACPIFamily, IOPCIFamily, PDEcamPCI, and for ARM and RISC-V PDArmPlatformExpert, PDArmPCI and PDRiscvPlatformExpert.
• Storage: IOStorageFamily, IOATAFamily and IOATABlockStorage, IONVMEFamily, RavynAHCIPort, IOVirtIOBlock, the SD card drivers for the boards, and the optical families.
• Filesystems: ext4 and Ext4FileSystemDriver, hfs with HFSEncodings, apfs and ApfsFileSystemDriver, msdosfs, cd9660 and AppleFileSystemDriver.
• Graphics: IOGraphicsFamily, IOGOPFramebuffer, IOVirtIOGPU, IONDRVSupport, PDIOSurface, and the DRM drivers PDDRMamdgpu, PDDRMi915 and PDDRMnouveau with PDDRMDri, which provides /dev/dri.
• Network: IONetworkingFamily, IO80211Family, IOVirtIONet, PDE1000, PDRealtek8111, PDRalinkUSB, and the FreeBSD drivers PDFBSDem, PDFBSDigc, PDFBSDrge, PDFBSDrtw89, PDFBSDrtwn and PDFBSDrun.
• Input, USB and audio: IOHIDFamily, ApplePS2Controller, IOUSBFamily, RavynXHCIPort, IOAudioFamily and RavynHDAudio.
• Support: corecrypto, pthread, Sandbox, amfi, GTrace and GMetric.

fbsdkpi is the FreeBSD compatibility layer. It builds on Haiku’s FreeBSD network and iflib compatibility code, adds FreeBSD’s net80211 and the LinuxKPI from FreeBSD, and lets the PDFBSD* and PDDRM* kexts run FreeBSD and drm-kmod drivers unmodified.

The corecrypto kext builds from the MPL-2.0 fork in external/corecrypto. The old GPL corecrypto in src/Libraries/libSystem/corecrypto is only compiled into Security.framework. See Licensing if you redistribute PureDarwin.

The ext4 driver is worth calling out. Darwin has no ext4, and PureDarwin uses it as the root filesystem, so it is entirely project code. It has been the source of a long list of subtle bugs (see Debugging).

src/Libraries

The userland foundation. Apple publishes some of it, and the rest is written here.

• The core: libSystem and its sub-libraries, dyld, libcxx, libcxxabi, libunwind, llvm-libc, libdarwin, architecture, AvailabilityVersions.
• Objective-C and system libraries: objc4, CoreServices, IOKit, DiskArbitration, Security with libDER, SystemConfiguration and libSystemConfiguration, CommonCrypto, libsandbox.
• Services: XPC (which includes launchd, launchctl and notifyd), syslog, libsystem_trace, mDNSResponder, libresolv, bootp, eap8021x, ppp.
• Graphics support: libdrm, libgbm, and the project’s own PDGOP, PDSurface and PDVirglShim.

src/Frameworks

The frameworks above the core: CoreFoundation, Foundation, AppKit, Cocoa, CoreGraphics and Onyx2D, CoreText, QuartzCore, CoreVideo, OpenGL, IOSurface, WindowServer, ApplicationServices and a growing list of others.

src/Userspace

The commands and apps that make the system usable.

• Commands: shell_cmds, text_cmds, system_cmds, diskdev_cmds, ps, ping, ioreg, sw_vers, netsetup, mdnsd, wifiutil, pdinstall, pdkext, pdpowerd, the ext4tool and ext4util maintenance tools, and tcc.
• The desktop: argon-session, MenuBar, Dock, Finder (shown as Files), Terminal, Settings, Calculator, SystemInformation, Installer and loginwindow.
• X11 support: startx and the two Xorg drivers xf86-video-puredarwingop and xf86-input-puredarwin.

src/ThirdParty

Upstream projects vendored because they needed real porting work: neuswc and neuwld (the compositor and drawing library under Argon), wayland, wayland-protocols, wlroots and sway.

projects/

libapfsrw, the APFS read and write library the apfs kext shares.

nix/

The ports under nix/pkgs/ are grouped by what they are:

ls nix/pkgs/<group> is the current answer for any of them.

tools/

Host-side build tools: cctools, mig, unifdef, dtrace_ctf, xar, iig-selfhost. See Host Tools and Toolchains.

cmake/

The CMake helper modules. See The CMake Tree.