On 30/06/2004, at 4:40 PM, Chris Zumbrunn wrote:
On 30. Jun 2004, at 3:01, Alasdair Lumsden wrote:
While Mach is derived from 4.3BSD (circa 1986~1988), there's been about
15 years worth of divergence since then. For example, FreeBSD is
monolithic while Mach is more micro-kernel based. Also the driver models
are quite different, eg Darwin uses IOKit (Object Oriented driver
interface model).
From Apple's webpages previewing Tiger:
"The upgraded kernel, based on FreeBSD 5.x, provides optimised resource locking for better scalability across multiple processors, support for 64-bit memory pointers through the System library and standards-based access control lists."
http://www.apple.com.au/macosx/tiger/unix.html
Some of the newer code in Darwin is "based on FreeBSD 5.x" yes, but the monolithic FreeBSD kernel (as a whole) is not one of them. Instead apple has targeted the "interesting" bits and imported these pieces of the kernel as discrete components into Darwin (they are implemented this way anyway).
Darwin still uses a Mach kernel design, although Apple has made some significant modifications to its implementation to reduce message passing overhead and latency etc, making it something of a hybrid and no longer a pure micro-kernel. As a result the Darwin Mach kernel is not the traditional Mach mix of userspace/kernelspace RPC connected components, instead the kernel is linked into a single address space, using kernel extensions (loadable modules) in a similar way FreeBSD does. However these extensions are implemented using a highly object oriented API (IOKit) for interacting with the kernel, instead of the traditional struct passing procedural approach used in FreeBSD.
The portions of the FreeBSD kernel that Apple have adopted can be found as part of the XNU project (the darwin kernel) from Apple's Opensource website
http://www.opensource.apple.com/darwinsource/
The CVS tags should still be intact on the files in question.
While FreeBSD provides a sizable chunk of Darwin's BSDness, it still has a decent amount of legacy NeXT/BSD code in it as well.
Some of the things that have been adopted from FreeBSD/NetBSD in the Darwin kernel include:
Crypto support
Filesystem support for CD9660, DEVFS, NFS, VFS, MEMDEV (Curiously this doesn't include UFS/FFS support)
IP & IPV6 TCP stack support including BPF & IPFW
Most of the BSD/Posix/SYSV system calls (sysctl, fork, exec, ktrace, mmap, etc) and corresponding MAN pages.
-- Seeya...Q
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