Date: Thu, 5 Apr 2007 10:19:03 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: cokane@cokane.org Cc: freebsd-hackers@freebsd.org, Mike Meyer <mwm-keyword-freebsdhackers2.e313df@mired.org> Subject: Re: Mac OS underlying FreeBSD - does it run Linux emulation? Message-ID: <20070405101628.N1092@fledge.watson.org> In-Reply-To: <346a80220704041047m210eb788h4f1d9aebcde3e99e@mail.gmail.com> References: <20070404130249.GA41671@kukulies.org> <17939.44784.420806.421633@bhuda.mired.org> <20070404153559.Y18288@fledge.watson.org> <346a80220704041047m210eb788h4f1d9aebcde3e99e@mail.gmail.com>
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On Wed, 4 Apr 2007, Coleman Kane wrote: >> While it's true you can't run Linux binaries on Mac OS X, it's not for the >> reason you're suggesting, and your statement regarding FreeBSD kernel code >> in Mac OS X is simply incorrect. The Mac OS X kernel, XNU, contains >> significant quantities of FreeBSD kernel source code, including a >> FreeBSD-derived VFS and network stack. Other parts of the kernel, such as >> the scheduler and VM system, are derived from Mach. While the >> FreeBSD-derived code has been significantly modified since it was >> originally forked, a lot of code moves backward and forward between the >> platforms: the FreeBSD audit subsystem is derived from the Mac OS X audit >> subsystem, and Mac OS X's smbfs and MAC Framework support are derived from >> FreeBSD. > > In addition to this, there have been examples of the Linux kernel hosted by > Mach in the past (such as MkLinux). From my understanding, the only thing > that prevents this from being realized is that nobody has sat down to > actually write/port the code to do it. I'm not familiar with the structural layout of MkLinux, but I would caution those looking at XNU to be aware that the kernel is a monolothic kernel, in which the BSD and IOKit parts run directly in the kernel address space managed by Mach, and not as tasks over Mach. If MkLinux runs Linux in a task under the microkernel, then the structures are quite different. Mach provides quite nice interfaces for implementation virtualization services, however, as Mach VM, thread, and task interfaces give applications a lot of control in setting up memory and trap handling -- much more so than the UNIX equivilents. Robert N M Watson Computer Laboratory University of Cambridge
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