Table of contents:
A. How to build XNU
B. How to install a new header file from XNU
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A. How to build XNU:
1) Type: "make"
This builds all the components for kernel, architecture, and machine
configurations defined in TARGET_CONFIGS. Additionally, we also support
architectures defined in ARCH_CONFIGS and kernel configurations defined in
KERNEL_CONFIGS. Note that TARGET_CONFIGS overrides any configurations defined
in ARCH_CONFIGS and KERNEL_CONFIGS.
By default, architecture defaults to the build machine
architecture, and the kernel configuration is set to build for DEVELOPMENT.
This will also create a bootable image, mach_kernel, and a kernel binary
with symbols, mach_kernel.sys.
/* this is all you need to do to build with RELEASE kernel configuration */
make TARGET_CONFIGS="release x86_64 default" SDKROOT=/path/to/SDK
or the following is equivalent (ommitted SDKROOT will use /)
make ARCH_CONFIGS=X86_64
2) Building DEBUG
Define kernel configuration to DEBUG in your environment or when running a
make command. Then, apply procedures 4, 5
$ make TARGET_CONFIGS="DEBUG X86_64 DEFAULT" all
or
$ make KERNEL_CONFIGS=DEBUG ARCH_CONFIGS=X86_64 all
or
$ export TARGET_CONFIGS="DEBUG X86_64 DEFAULT"
$ export SDKROOT=/path/to/SDK
$ make all
Example:
$(OBJROOT)/DEBUG_X86_64/osfmk/DEBUG/osfmk.filelist: list of objects in osfmk component
$(OBJROOT)/DEBUG_X86_64/mach_kernel: bootable image
3) Building fat
Define architectures in your environment or when running a make command.
Apply procedures 3, 4, 5
$ make TARGET_CONFIGS="RELEASE I386 DEFAULT RELEASE X86_64 DEFAULT" exporthdrs all
or
$ make ARCH_CONFIGS="I386 X86_64" exporthdrs all
or
$ export ARCH_CONFIGS="I386 X86_64"
$ make exporthdrs all
4) Verbose make
To display complete tool invocations rather than an abbreviated version,
$ make VERBOSE=YES
5) Debug information formats
By default, a DWARF debug information repository is created during the install phase; this is a "bundle" named mach_kernel.dSYM
To select the older STABS debug information format (where debug information is embedded in the mach_kernel.sys image), set the BUILD_STABS environment variable.
$ export BUILD_STABS=1
$ make
6) Build check before integration
From the top directory, run:
$ ~rc/bin/buildit . -arch i386 -arch x86_64 -arch armv7 -arch ppc -noinstallsrc -nosum
xnu supports a number of XBS build aliases, which allow B&I to build
the same source submission multiple times in different ways, to
produce different results. Each build alias supports the standard
"clean", "install", "installsrc", "installhdrs" targets, but
conditionalize their behavior on the RC_ProjectName make variable
which is passed as the -buildAlias argument to ~rc/bin/buildit, which
can be one of:
-buildAlias xnu # the default, builds /mach_kernel, kernel-space
# headers, user-space headers, man pages,
# symbol-set kexts
-buildAlias xnu_debug # a DEBUG kernel in /AppleInternal with dSYM
-buildAlias libkxld # user-space version of kernel linker
-buildAlias libkmod # static library automatically linked into kexts
-buildAlias Libsyscall # automatically generate BSD syscall stubs
-buildAlias xnu_quick_test # install xnu unit tests
7) Creating tags and cscope
Set up your build environment as per instructions in 2a
From the top directory, run:
$ make tags # this will build ctags and etags on a case-sensitive
# volume, only ctags on case-insensitive
$ make TAGS # this will build etags
$ make cscope # this will build cscope database
8) Reindenting files
Source files can be reindented using clang-format setup in .clang-format. XNU follow a variant of WebKit style for source code formatting. Please refer to format styles at http://www.webkit.org/coding/coding-style.html. Further options about style options is available at http://clang.llvm.org/docs/ClangFormatStyleOptions.html
Note: clang-format binary may not be part of base installation. It can be compiled from llvm clang sources and is reachable in $PATH.
From the top directory, run:
$ make reindent # reindent all source files using clang format.
9) Other makefile options
$ make MAKEJOBS=-j8 # this will use 8 processes during the build. The default is 2x the number of active CPUS.
$ make -j8 # the standard command-line option is also accepted
$ make -w # trace recursive make invocations. Useful in combination with VERBOSE=YES
$ make BUILD_LTO=0 # build without LLVM Link Time Optimization
$ make REMOTEBUILD=user@remotehost # perform build on remote host
$ make BUILD_JSON_COMPILATION_DATABASE=1 # Build Clang JSON Compilation Database
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B. How to install a new header file from XNU
[To install IOKit headers, see additional comments in iokit/IOKit/Makefile.]
1) XNU installs header files at the following locations -
a. $(DSTROOT)/System/Library/Frameworks/Kernel.framework/Headers
b. $(DSTROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders
c. $(DSTROOT)/usr/include/
d. $(DSTROOT)/System/Library/Frameworks/System.framework/PrivateHeaders
Kernel.framework is used by kernel extensions. System.framework
and /usr/include are used by user level applications. The header
files in framework's "PrivateHeaders" are only available for Apple
Internal development.
2) The directory containing the header file should have a Makefile that
creates the list of files that should be installed at different locations.
If you are adding first header file in a directory, you will need to
create Makefile similar to xnu/bsd/sys/Makefile.
Add your header file to the correct file list depending on where you want
to install it. The default locations where the header files are installed
from each file list are -
a. DATAFILES : To make header file available in user level -
$(DSTROOT)/usr/include
b. PRIVATE_DATAFILES : To make header file available to Apple internal in
user level -
$(DSTROOT)/System/Library/Frameworks/System.framework/PrivateHeaders
c. KERNELFILES : To make header file available in kernel level -
$(DSTROOT)/System/Library/Frameworks/Kernel.framework/Headers
$(DSTROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders
d. PRIVATE_KERNELFILES : To make header file available to Apple internal
for kernel extensions -
$(DSTROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders
3) The Makefile combines the file lists mentioned above into different
install lists which are used by build system to install the header files.
If the install list that you are interested does not exist, create it
by adding the appropriate file lists. The default install lists, its
member file lists and their default location are described below -
a. INSTALL_MI_LIST : Installs header file to a location that is available to
everyone in user level.
Locations -
$(DSTROOT)/usr/include
Definition -
INSTALL_MI_LIST = ${DATAFILES}
b. INSTALL_MI_LCL_LIST : Installs header file to a location that is available
for Apple internal in user level.
Locations -
$(DSTROOT)/System/Library/Frameworks/System.framework/PrivateHeaders
Definition -
INSTALL_MI_LCL_LIST = ${PRIVATE_DATAFILES}
c. INSTALL_KF_MI_LIST : Installs header file to location that is available
to everyone for kernel extensions.
Locations -
$(DSTROOT)/System/Library/Frameworks/Kernel.framework/Headers
Definition -
INSTALL_KF_MI_LIST = ${KERNELFILES}
d. INSTALL_KF_MI_LCL_LIST : Installs header file to location that is
available for Apple internal for kernel extensions.
Locations -
$(DSTROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders
Definition -
INSTALL_KF_MI_LCL_LIST = ${KERNELFILES} ${PRIVATE_KERNELFILES}
4) If you want to install the header file in a sub-directory of the paths
described in (1), specify the directory name using two variable
INSTALL_MI_DIR and EXPORT_MI_DIR as follows -
INSTALL_MI_DIR = dirname
EXPORT_MI_DIR = dirname
5) A single header file can exist at different locations using the steps
mentioned above. However it might not be desirable to make all the code
in the header file available at all the locations. For example, you
want to export a function only to kernel level but not user level.
You can use C language's pre-processor directive (#ifdef, #endif, #ifndef)
to control the text generated before a header file is installed. The kernel
only includes the code if the conditional macro is TRUE and strips out
code for FALSE conditions from the header file.
Some pre-defined macros and their descriptions are -
a. PRIVATE : If true, code is available to all of the xnu kernel and is
not available in kernel extensions and user level header files. The
header files installed in all the paths described above in (1) will not
have code enclosed within this macro.
b. KERNEL_PRIVATE : Same as PRIVATE
c. BSD_KERNEL_PRIVATE : If true, code is available to the xnu/bsd part of
the kernel and is not available to rest of the kernel, kernel extensions
and user level header files. The header files installed in all the
paths described above in (1) will not have code enclosed within this
macro.
d. KERNEL : If true, code is available only in kernel and kernel
extensions and is not available in user level header files. Only the
header files installed in following paths will have the code -
$(DSTROOT)/System/Library/Frameworks/Kernel.framework/Headers
$(DSTROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders