KEXTLOAD(8) System Manager's Manual KEXTLOAD(8)
NAME
kextload - loads, validates, and generates symbols for a kernel extension
(kext)
SYNOPSIS
kextload [-h] [-v [1-6]] [-t] [-i | -I] [-x] [-z] [-e] [-c] [-D]
[-k kernel_file] [-d extension] ... [-r directory] ... [ -l |
-m | -n | -A | -a kext_id@address ] ... [-s directory]
[-p personality] ... [-b -bundle_id] ... [--] [extension] ...
DESCRIPTION
The kextload program is used to explicitly load kernel extensions
(kexts), validate them to see that they can be loaded by other mecha-
nisms, such as kextd(8), and to generate symbol files for debugging the
kext in a running kernel. In order to load a kext into the kernel
kextload must be invoked as the superuser; for all other uses it can be
invoked by any user.
kextload is a formal interface for kext loading in the Darwin OS and in
Mac OS X. Software and installers can rely on its presence and invoke it
in order to load kexts.
kextload has many options, but most of them are rarely necessary. See
the EXAMPLES section for tips on common uses. The arguments and options
available are these:
extension
The pathname of a kext bundle to load or otherwise use. Kexts
can also be specified by CFBundleIdentifier with the -b option.
-a kext_id@address
Treat the kext whose CFBundleIdenfier is kext_id as being loaded
at address when generating symbol files and not loading. When
generating symbols only, all dependencies must have known
addresses. Use this option repeatedly for every nonkernel
dependency. This option implies the use of the -n option. See
also -A and -n.
-A When generating symbol files and not loading, look up all depen-
dency kext addresses within the running kernel. This option
implies the use of the -n option. See also -a and -n.
-b bundle_id
Look up the kext whose CFBundleIdentifier is bundle_id within
the set of known kexts and load it. See the -d, -e, and -r
options for more information.
-c Ignore any repository cache files and scan all kext bundles to
gather information. If this option is not given, kextload will
attempt to use cache files and to create them if they are out of
date or don't exist.
-d extension
Add extension to the set of known kexts for resolving dependen-
cies. This is useful for adding a single kext from a directory
while excluding the others. See the -e and -r options for more
information.
-D Don't check the kernel for already loaded kexts when resolving
dependencies. Note that this can result in load failures if a
different version of a dependency is already loaded. This
option is relevant only when loading a kext into the kernel.
The -A option overrides this option as it must check the kernel
for which kexts are loaded.
-e Don't use the contents of /System/Library/Extensions as the
default repository of kexts. If you use this option you will
have to explicitly specify all dependencies of the kext being
loaded or otherwise worked on using the -d and -r options.
-h Print a help message describing each option flag.
-i Interactive mode; pause at each stage of loading for user input
to continue. This allows for debugger setup when the kext needs
to be debugged during its earliest stages of running.
-I (capital i) Interactive mode as -i for the specified kext and
all of its dependencies.
-k kernel_file
Link against the given kernel_file (default is /mach). Allowed
only with the -n option to generate debug symbols.
-l Load and start the kext only; don't send I/O Kit personalities
to the kernel to begin matching. Matching may still occur if
the personalities are present from an earlier load operation.
You may want to use kextunload(8) before loading a kext with
this option.
-L Same as -r (remains for backward compatibility).
-m Don't load the kext, but do send its personalities to the kernel
to begin matching. Use this option after you have loaded a
driver with -l and after setting up the debugger.
-n Neither load the kext nor send personalities to the kernel.
This option is for use when generating debug symbols only with
the -s option, or when validating kexts with the -t option. See
also the -a and - A options.
-p personality
Send only the named personalities from the kext to the kernel.
Repeat for each personality desired, or use the -i option to
have kextload ask for each personality.
-r directory
Use directory as a repository of kexts. This adds to the set of
known kexts for resolving dependencies or looking up by
CFBundleIdentifier when using the -b option. This is not recur-
sive; only the directory's immediate contents are scanned. See
also the -c, -d, and -e options.
-s directory
Write all generated symbol files into directory. The directory
must already exist. Symbol files are named after the CFBundleI-
dentifier of each kexts with a .sym suffix appended.
-t Perform all possible tests on the named kext(s) and indicate
whether the kext is loadable, or if not, what problems it has.
Note that tests are performed in three stages, validation,
authentication, and dependency resolution; a failure at any
stage can make tests in further stages impossible. Thus, a kext
with validation failures may have unreported authentication
problems or missing dependencies.
-v [1-6]
Verbose mode; print information about the kext scanning and
loading process. Higher levels of verbosity include all lower
levels. The levels of verbose output are these:
1 prints basic kext scanning information
2 prints basic load information
3 prints detailed kext scanning information
4 prints basic information on every kext encountered
5 prints detailed information on every kext encountered
6 prints detailed load information
A kext can also specify verbose printing for just itself using
the OSBundleDebugLevel top-level info dictionary property. Its
values are 1 and 2, for basic and detailed information, respec-
tively.
-x Run kextload in safe boot mode (indicating startup with the
Shift key held down). Kexts that don't specify a proper value
for the OSBundleRequired info dictionary property, or those in
which every personality contains a nonzero IOKitDebug property,
will not load. This option implies the use of the -c option.
-z Don't authenticate kexts. This option is for convenience during
development, and is allowed only for operations that don't actu-
ally load a kext into the kernel (such as when generating sym-
bols).
-Z Don't try to resolve dependencies. This option is allowed only
when using the -n and -t options to test a kext for problems.
It is not allowed with the -s option as generating symbols
requires dependencies to be resolved.
-- End of all options. Only kext names follow.
EXAMPLES
Here are the common uses and usage patterns for kextload.
Basic loading
To load a kext you must run kextload as the superuser and supply a kext
bundle name; no options are required:
kextload TabletDriver.kext
Alternatively, you can use the -b option to specify a kext by its
CFBundleIdentifier:
kextload -b com.mycompany.driver.TabletDriver
With no additional options kextload will look in /System/Library/Exten-
sions for a kext with the given CFBundleIdentifier. Adding repository
directories with the -r option or individual kexts with the -d option
expands the set of kexts that kextload looks among:
kextload -r ${USER}/Library/Extensions TabletDriver.kext
If you're modifying system startup to load a kext, be sure to check
whether the system is starting up in safe boot mode (typically when the
user presses the Shift key) and use the -x option to indicate this. (The
various rc files in /etc can simply use the $SafeBoot shell variable on
the command line. It evaluates to an empty string during normal startup
and "-x" during safe boot mode.)
Validating Kexts
The -t option causes kextload to perform all possible validation and
authentication checks on the specified kexts and to attempt to resolve
their dependencies. If there are any problems with the specified kexts,
kextload prints a list of the problems.
The -t option is typically used with -n after a load failure to pinpoint
a problem. It can be used with any other set of options, however.
If you want to validate a kext in isolation, as in a build environment
where dependencies may not be available, you can use the -e and -Z
options to omit the /System/Library/Extensions repository and to suppress
dependency resolution, respectively:
kextload -entZ PacketSniffer.kext
Only validation and authentication checks will be performed.
Generating Debug Symbols When Loading
To generate a symbol file for use with gdb when loading a kext, use the
-s option to specify a directory where symbol files will be written for
the kext being loaded and all its dependencies.
kextload -s ~/ksyms PacketSniffer.kext
Generating Debug Symbols For an Already-Loaded Kext
If you want to generate symbols for a kext that's already loaded, whether
on the same system or on another, use the -s option along with the -n
option. Since in this case addresses must be known for the kext and all
its dependencies, though, you must specify these. If you don't indicate
them on the command line, kextload will ask you for the load address of
each kext needed. Use kextstat(8) on the machine you're generating sym-
bols for to get these addresses and enter them at each prompt.
kextload -n -s ~/ksyms GrobbleEthernet.kext
enter the hexadecimal load addresses for these modules:
com.apple.iokit.IONetworkingFamily: 0x1001000
...
Alternatively, if you know the CFBundleIdentifiers of all the kexts, you
can use the -a option for each kext (you needn't specify -n when using
the -a option):
kextload -s ~/ksyms \
-a com.apple.iokit.IONetworkingFamily@0x1001000 \
-a com.apple.iokit.IOPCIFamily@0x1004000 \
-a com.mycompany.driver.GrobbleEthernet@0x1007000 \
GrobbleEthernet.kext
Simplest of all, however, provided you can run kextload on the same
machine as the loaded kext, is to use the -A option, which checks with
the kernel for all loaded kexts and automatically gets their load
addresses.
kextload -s ~/ksyms -A GrobbleEthernet.kext
Explicitly Specifying Dependencies
Because kextload resolves dependencies automatically, it's possible that
a kext other than the one you intend might get used as a dependency (such
as when there are multiple versions, or if you're working on a new ver-
sion of a kext that's already installed in /System/Library/Extensions).
By default, when loading a kext into the kernel kextload checks which
versions of possible dependencies are already loaded in order to assure a
successful load. When not loading, however, it always chooses the most
recent versions of any dependencies.
If you want to have complete control over the set of extensions used to
resolve dependencies, use the -e, -d, and -r options. The -e option
excludes the standard /System/Library/Extensions folder, leaving the set
of candidate extensions for dependency resolution entirely up to you. To
specify candidate dependencies you use either -d, which names a single
kext as a candidate, or -r, which adds an entire directory of extensions.
kextload -n -s ~/ksyms -e \
-d /System/Library/Extensions/System.kext \
-r ~/TestKexts -d JoystickSupport.kext JoystickDriver.kext
Note also that if you use -e, you must supply some version of the Sys-
tem.kext bundle in order to supply information about the kernel. This
should always match the kernel you're linking against, which is by
default the installed kernel on the machine you're using kextload on; you
can use the -k option to indicate a different kernel file.
Debug-Loading an I/O Kit Driver
If you need to debug an I/O Kit driver's early startup code, you must
load the driver on the target machine without starting matching by using
the -l option:
kextload -l DiskController.kext
Once you have done this, you can use the generated symbol file in your
debug session to set breakpoints and then trigger matching by running
kextload again on the target machine with the -m option:
kextload -m DiskController.kext
You may wish to use the -p option as well in order to send selected per-
sonalities to the kernel. Alternatively, you can use the -i option for
the whole process, which causes kextload to pause just before loading any
personalities and then to ask you for each personality whether that one
should be sent to the kernel:
kextload -i DiskController.kext
Debug-Loading a non-I/O Kit Kext
A non-I/O Kit kext doesn't have a personality-matching phase of loading;
it just starts executing. In order to debug a non-I/O Kit kext's startup
code, you must use the -i or -I option, which pauses loading at each sig-
nificant stage so that you can set up your debugging session as needed
before proceeding.
FILES
/System/Library/Extensions The standard system repository of kernel
extensions
directoryname.kextcache A cache of all kext info dictionaries
(plists) for a given directory
DIAGNOSTICS
kextload exits with a zero status upon success. Upon failure, it prints
an error message and continues processing any kexts if possible, then
exits with a nonzero status.
SEE ALSO
kextd(8), kextunload(8)
BUGS
Upon encountering a kext with validation errors, kextload typically
prints an error message about that kext, even if it isn't involved in the
load request.
Darwin February 22, 2002 Darwin