Building the XNU kernel on macOS Sierra

XNU open source bits from Apple are always a tiny subset of the actual kernel code. Plus, long gone are the people who Apple hired from the FreeBSD world who believed in it enough to push internally for it. So who knows at this point what is filtered out at publish time.

Don't get me wrong, it's great to read how file drivers really work, and read how XNU manages virtual memory, but other than that, it's a pretty crappy drop.

mikalv10• 9 years ago

Yea personally I'm mostly fascinated with the semi microkernel architecture. I don't really mind that the rest is closed. And yea, I've suspected they lost some good people after seeing all the new security issues in the kernel the past years.

If only wayland was more mature, and the Linux world would have put down X11 once and for all, I would be back on Linux a long time ago :)

ori_b2• 9 years ago

If only wayland was more mature, and the Linux world would have put down X11 once and for all, I would be back on Linux a long time ago :)

I'm curious why Wayland changes things for you. X11 is warty as hell, but that's generally not something visible to the user. I don't go "Eww, they didn't bother framing the graphics message packets properly -- I'm going to use another OS".

pjmlp9• 9 years ago

I came to realize that for those of us that actually care about graphics programming, nice GUI tools and UI/UX, Linux world will never be the place to be.

The majority of devs are happy having a replicate of PDP-11 experience, maybe with twm and tools like xdvi or xv.

Those that try to improve the overall desktop experience closer to other desktop systems, get bashed as needless fluff.

nickpsecurity3• 9 years ago

The merging of Mach with UNIX was a mistake given it was one of the slowest, over-complicated microkernels. Far as I'm aware, they'd prefer to remove Mach but it's a big job at this point that might affect their ecosystem a lot. If you are interested in open microkernels, I encourage you to look into L4 family (eg OCL4 or OKL4) since they're far more advanced than Mach-based designs. Minix 3 does one with NetBSD userland and self-healing capabilities. GenodeOS is turning one into a desktop. IBM's K42 ran on NUMA machines. JX OS mixes one with a JVM to run the OS in Java. For security, GEMSOS was a security kernel w/ MAC. KeyKOS and EROS were examples of those doing capability-based security. Modern ones like Muen and seL4 just do separation w/ apps managing security policy.

EDIT: Windows is also a "semi-microkernel" with a microkernel inside of it on the bottom that seems to be used for consistent way of interfacing components more than anything. I'm not sure if it's still in there.

devin_lane• 9 years ago

The instructions end with where to copy it to boot off it -- does this just not work at all? Or is it just less performant/capable?

raimue• 9 years ago

Especially they are hiding everything about the ARM architecture. There have not been any code drops for iOS except WebKit.

As an example, you can see here how Apple removes whole files and even code in #ifdef sections before throwing it over the wall:

https://opensource.apple.com/source/hfs/hfs-366.50.19/make_o...

steeleduncan• 9 years ago

Is there a better approach for experimenting with filesystems than editing the kernel sources, recompiling and then running in a VM? e.g. A C library providing the necessary interface for the sources to drop into a kernel eventually, but also allowing you to run tests, set breakpoints, etc within an IDE.

Of course you can get a long way accessing a block device directly with FUSE, but ultimately you end up developing a FUSE library, not something you can use within the kernel.

zymhan• 9 years ago

OpenDNS in my office is blocking access to the site because of "malware".

I can't tell if that's a legitimate warning, or it being paranoid about what else is on the site.

mikalv10• 9 years ago

Hahaha, yes I just found out my own comany's firewall does the same. I suspect it's the hex domain :)

Online services says it's clean and I know how to secure my own webserver/services :) https://sitecheck.sucuri.net/results/0xcc.re

Building the XNU kernel on macOS Sierra

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