===========
XNU kernel is part of the Darwin operating system for use in macOS and iOS operating systems. XNU is an acronym for X is Not Unix.
-XNU is a hybrid kernel combining the Mach kernel developed at Carnegie Mellon University with components from FreeBSD and C++ API for writing drivers called IOKit.
+XNU is a hybrid kernel combining the Mach kernel developed at Carnegie Mellon University with components from FreeBSD and a C++ API for writing drivers called IOKit.
XNU runs on x86_64 for both single processor and multi-processor configurations.
XNU Source Tree
To build a kernelcache you can use the following mechanisms:
* Using automatic kernelcache generation with `kextd`.
- The kextd daemon keeps watching for changing in `/System/Library/Extensions` directory.
+ The kextd daemon keeps watching for changing in `/System/Library/Extensions` directory.
So you can setup new kernel as
$ cp BUILD/obj/DEVELOPMENT/X86_64/kernel.development /System/Library/Kernels/
$ make cscope # this will build cscope database
-Coding styles (Reindenting files)
-=================================
+Code Style
+==========
-Source files can be reindented using clang-format setup in .clang-format.
-XNU follows a variant of WebKit style for source code formatting.
-Please refer to format styles at [WebKit website](http://www.webkit.org/coding/coding-style.html).
-Further options about style options is available at [clang docs](http://clang.llvm.org/docs/ClangFormatStyleOptions.html)
+Source files can be reformatted to comply with the xnu code style using the "restyle" make target invoked from the
+top-level project directory.
- 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.
+ $ make restyle # re-format all source files to be xnu code style conformant.
+Compliance can be checked using the "checkstyle" make target.
+ $ make checkstyle # Check all relevant source files for xnu code style conformance.
How to install a new header file from XNU
=========================================
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
+ d. $(DSTROOT)/System/DriverKit/usr/include/
+ e. $(DSTROOT)/System/Library/Frameworks/System.framework/PrivateHeaders
`Kernel.framework` is used by kernel extensions.\
The `System.framework` and `/usr/include` are used by user level applications. \
+`/System/DriverKit/usr/include` is used by userspace drivers. \
The header files in framework's `PrivateHeaders` are only available for ** Apple Internal Development **.
The directory containing the header file should have a Makefile that
creates the list of files that should be installed at different locations.
-If you are adding first header file in a directory, you will need to
-create Makefile similar to xnu/bsd/sys/Makefile.
+If you are adding the first header file in a directory, you will need to
+create Makefile similar to `xnu/bsd/sys/Makefile`.
Add your header file to the correct file list depending on where you want
to install it. The default locations where the header files are installed
a. `DATAFILES` : To make header file available in user level -
`$(DSTROOT)/usr/include`
- b. `PRIVATE_DATAFILES` : To make header file available to Apple internal in
+ b. `DRIVERKIT_DATAFILES` : To make header file available to DriverKit userspace drivers -
+ `$(DSTROOT)/System/DriverKit/usr/include`
+
+ c. `PRIVATE_DATAFILES` : To make header file available to Apple internal in
user level -
`$(DSTROOT)/System/Library/Frameworks/System.framework/PrivateHeaders`
- c. `KERNELFILES` : To make header file available in kernel level -
+ d. `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
+ e. `PRIVATE_KERNELFILES` : To make header file available to Apple internal
for kernel extensions -
`$(DSTROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders`
The Makefile combines the file lists mentioned above into different
-install lists which are used by build system to install the header files.
+install lists which are used by build system to install the header files. There
+are two types of install lists: machine-dependent and machine-independent.
+These lists are indicated by the presence of `MD` and `MI` in the build
+setting, respectively. If your header is architecture-specific, then you should
+use a machine-dependent install list (e.g. `INSTALL_MD_LIST`). If your header
+should be installed for all architectures, then you should use a
+machine-independent install list (e.g. `INSTALL_MI_LIST`).
If the install list that you are interested does not exist, create it
by adding the appropriate file lists. The default install lists, its
Definition -
INSTALL_MI_LIST = ${DATAFILES}
- b. `INSTALL_MI_LCL_LIST` : Installs header file to a location that is available
+ b. `INSTALL_DRIVERKIT_MI_LIST` : Installs header file to a location that is
+ available to DriverKit userspace drivers.
+ Locations -
+ $(DSTROOT)/System/DriverKit/usr/include
+ Definition -
+ INSTALL_DRIVERKIT_MI_LIST = ${DRIVERKIT_DATAFILES}
+
+ c. `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
+ d. `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
+ e. `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}
- e. `EXPORT_MI_LIST` : Exports header file to all of xnu (bsd/, osfmk/, etc.)
+ f. `EXPORT_MI_LIST` : Exports header file to all of xnu (bsd/, osfmk/, etc.)
for compilation only. Does not install anything into the SDK.
Definition -
EXPORT_MI_LIST = ${KERNELFILES} ${PRIVATE_KERNELFILES}
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` : If true, code is available to all of the xnu kernel and Apple
- internal kernel extensions.
-
- 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
+ a. `PRIVATE` : If defined, enclosed definitions are considered System
+ Private Interfaces. These are visible within xnu and
+ exposed in user/kernel headers installed within the AppleInternal
+ "PrivateHeaders" sections of the System and Kernel frameworks.
+ b. `KERNEL_PRIVATE` : If defined, enclosed code is available to all of xnu
+ kernel and Apple internal kernel extensions and omitted from user
+ headers.
+ c. `BSD_KERNEL_PRIVATE` : If defined, enclosed code is visible exclusively
+ within the xnu/bsd module.
+ d. `MACH_KERNEL_PRIVATE`: If defined, enclosed code is visible exclusively
+ within the xnu/osfmk module.
+ e. `XNU_KERNEL_PRIVATE`: If defined, enclosed code is visible exclusively
+ within xnu.
+ f. `KERNEL` : If defined, enclosed code is available within xnu and kernel
+ extensions and is not visible in user level header files. Only the
header files installed in following paths will have the code -
$(DSTROOT)/System/Library/Frameworks/Kernel.framework/Headers
$(DSTROOT)/System/Library/Frameworks/Kernel.framework/PrivateHeaders
+ g. `DRIVERKIT`: If defined, enclosed code is visible exclusively in the
+ DriverKit SDK headers used by userspace drivers.
+
+Conditional compilation
+=======================
+
+`xnu` offers the following mechanisms for conditionally compiling code:
- you should check [Testing the kernel][] for details.
+ a. *CPU Characteristics* If the code you are guarding has specific
+ characterstics that will vary only based on the CPU architecture being
+ targeted, use this option. Prefer checking for features of the
+ architecture (e.g. `__LP64__`, `__LITTLE_ENDIAN__`, etc.).
+ b. *New Features* If the code you are guarding, when taken together,
+ implements a feature, you should define a new feature in `config/MASTER`
+ and use the resulting `CONFIG` preprocessor token (e.g. for a feature
+ named `config_virtual_memory`, check for `#if CONFIG_VIRTUAL_MEMORY`).
+ This practice ensures that existing features may be brought to other
+ platforms by simply changing a feature switch.
+ c. *Existing Features* You can use existing features if your code is
+ strongly tied to them (e.g. use `SECURE_KERNEL` if your code implements
+ new functionality that is exclusively relevant to the trusted kernel and
+ updates the definition/understanding of what being a trusted kernel means).
+It is recommended that you avoid compiling based on the target platform. `xnu`
+does not define the platform macros from `TargetConditionals.h`
+(`TARGET_OS_OSX`, `TARGET_OS_IOS`, etc.).
+
+
+There is a deprecated `TARGET_OS_EMBEDDED` macro, but this should be avoided
+as it is in general too broad a definition for most functionality.
+Please refer to TargetConditionals.h for a full picture.
How to add a new syscall
========================
To debug a panic'ed kernel, use llvm debugger (lldb) along with unstripped symbol rich kernel binary.
sh$ lldb kernel.development.unstripped
-
+
And then you can connect to panic'ed machine with `kdp_remote [ip addr]` or `gdb_remote [hostip : port]` commands.
Each kernel is packaged with kernel specific debug scripts as part of the build process. For security reasons these special commands
projects / apple / xnu.git / blobdiff