Inside the Mac OS X Kernel

Mac OS의 Kernel에 관한 문서입니다.

986_inside_the_mac_osx_kernel.pdf

Revisiting the Buzzwords

• The OS X kernel is not Mach.
  The OS X kernel is called “XNU”, which consists of Mach, BSD and I/O-Kit.

• The OS X kernel is not a microkernel.  
   Al-though Mach has been used as a microkernel in other projects, XNU is a very traditional monolithic kernel
   with BSD and (most) drivers in kernel mode.

• The OS X kernel is not based on FreeBSD. 

   The BSD part is based on 4.4BSD with some code from FreeBSD, NetBSD and others. 
   The OS X userland UNIX tools are mostly based on FreeBSD code, though.

• The OS X kernel is not written in C++.
   The I/O-Kit part  is written in a subset of C++, but Mach and BSD are written in C.

• The OS X  kernel is not 64 bit.
    It supports 64 bit user mode applications on a 64 bit PowerPC or Intel CPU, but the kernel itself runs in 32 bit
    mode and is bound to the 4 GB ad-dress space limit.

• The OS X kernel is Open Source, but there is no live source code repository visible
   outside of  Apple, and the released source does not necessarily contain all code,
   but can be compiled into a working system.
• The OS X kernel is UNIX, but only since OS X  10.5  Leopard, and only for 32 bit i386,
   since this is the configuration that passed the POSIX conformance test and may
   therefore use the OpenGroup's “UNIX” trademark.

 

References

• Singh, Amit: Mac OS X Internals. A Systems Approach; Addison-Wesley, 2006.

• http://kernel.macosforge.org/

• http://www.opensource.apple.com/darwinsource/