KEXTUTIL(8)

NAME
kextutil - load, diagnose problems with, and generate symbols for kernel extensions (kexts)

SYNOPSIS
kextutil [options] [--] [kext] ...

DESCRIPTION
The kextutil program is used to explicitly load kernel extensions (kexts), diagnose problems with kexts, and to generate symbol files for debugging kexts. In order to load a kext into the kernel kextutil must run as the superuser; for all other uses it can run as any user.

kextutil is the developer utility for kext loading in the Darwin OS and in Mac OS X. Software and installers should use kextload(8) instead of this program.

The arguments and options available are these:

kext
    The pathname of a kext bundle to load or otherwise use. Kexts can also be specified by CFBundleIdentifier with the -bundle-id option.

-a identifier@address, -address identifier@address
    Treat the kext whose CFBundleIdenfier is identifier as being loaded at address when generating symbol files and not loading. When generating symbols, any dependencies with unspecified addresses are skipped. Use this option repeatedly to name every nonkernel dependency for which you want symbols. This option implies the use of the -no-load option. See also -use-load-addresses and -no-load.

-arch
    Use the specified architecture for generating symbols and performing tests. If loading into the kernel or getting load addresses from the kernel, the specified arch must match that of the running kernel.

-A, -use-load-addresses
    When generating symbol files and not loading, look up all dependency kext addresses within the running kernel. This option implies the use of the -no-load option. See also -address and -no-load.

-b identifier, -bundle-id identifier
    Look up the kext whose CFBundleIdentifier is identifier within the set of known kexts and load it. The kext of the highest CFBundleVersion with the given identifier is used; in the case of version ties, the last such kext specified on the command line is used. See the -dependency, -no-system-extensions, and -repository options for more information.

-c, -no-caches
    Ignore any repository cache files and scan all kext bundles to gather information. If this option is not given, kextutil attempts to use cache files and (when running as root) to create them if they are out of date or don't exist.

-d kext, -dependency kext
    Add kext and its plugins to the set of known kexts for resolving dependencies. This is useful for adding a single kext from a directory. See “Explicitly Specifying Dependencies” for more information, as well as the -no-system-extensions and -repository options.

-e, -no-system-extensions
    Don't use the contents of /System/Library/Extensions/ or /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 -dependency and -repository options. See “Explicitly Specifying Dependencies” for more information.

-h, -help
    Print a help message describing each option flag and exit with a success result, regardless of any other options on the command line.

-i, -interactive
    Interactive mode; pause after loading each specified kext and wait for user input to start the kext and send its personalities to the kernel. This allows for debugger setup when the kext needs to be debugged during its earliest stages of running.

-I, -interactive-all
    Interactive mode, as described above, for each specified kext and all of their dependencies.

-k kernel_file, -kernel kernel_file
    Link against the given kernel_file. Allowed only with the -no-load option to generate debug symbols. By default kextutil attempts to get link symbols from the kernel at /System/Library/Kernels/kernel.

-l, -load-only
    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.

-m, -match-only
    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 -load-only and after setting up the debugger.

-n, -no-load
    Neither load the kext nor send personalities to the kernel. This option is for use when generating debug symbols only with the -symbols option, or when diagnosing kexts with the -print-diagnostics option. For convenience in development, this option implies the -no-authentication option. See also the -address and -use-load-addresses options.

-p personality, -personality personality
    Send only the named personalities from the kext to the kernel. Repeat for each personality desired, or use the -interactive option to have kextutil ask for each personality.

-q, -quiet
    Quiet mode; print no informational or error messages. If kextutil is run with -quiet in a way that might require user interaction, as with the -interactive and -interactive-all options, and some uses of -no-load, the program silently exits with an error status.

-r directory, -repository 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 -bundle-id option. This is not recursive; only the directory's immediate contents (and their plugins) are scanned. See “Explicitly Specifying Dependencies” for more information, as well as the -dependency and -no-system-extensions options.

-s directory, -symbols directory
    Write all generated symbol files into directory. The directory must already exist. Symbol files are named after the CFBundleIdentifier of each kext with a .sym suffix appended.

-t, -print-diagnostics
    Perform all possible tests on the specified kexts, even with options that implicitly disable some tests, 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 [0-6 | 0x####], -verbose [0-6 | 0x####]
    Verbose mode; print information about program operation. Higher levels of verbosity include all lower levels. By default kextutil prints only warnings and errors. You can specify a level from 0-6, or a hexadecimal log specification (as described in kext_logging(8)). The levels of verbose output are:

    0   Print only errors (that is, suppress warnings); see also -quiet.

    1 (or none)
        Print basic information about program operation.

    2   Print basic information about the link/load operation.

    3   Print more information about user-kernel interaction, link/load operation, and processing of I/O Kit Personalities.

    4   Print detailed information about module start and C++ class construction.

    5   Print internal debug information, including checks for loaded kexts.

    6   Identical to level 5 but for all kexts read by the program.

    To ease debug loading of kexts, the verbose levels 1-6 in kextutil implicitly set the OSBundleEnableKextLogging property for each kext specified on the command line to true. See kext_logging(8) for more information on verbose logging.

-x, -safe-boot
    Run kextutil as if 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 will not load. This option implies the use of the -no-caches option.

    Note that if the system has actually started up in safe boot mode, this option is redundant. There is no way to simulate non-safe boot mode for a system running in safe boot mode.

-z, -no-authentication
    Don't authenticate kexts. This option is for convenience during development, and is allowed only for operations that don't actually load a kext into the kernel (such as when generating symbols).

-Z, -no-resolve-dependencies
    Don't try to resolve dependencies. This option is allowed only when using the -no-load and -print-diagnostics options to test a kext for problems. It is not allowed with the -symbols 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 kextutil.

  Basic Loading
To load a kext you must run kextutil as the superuser and supply a kext bundle name; no options are required:

    kextutil TabletDriver.kext

Alternatively, you can use the -bundle-id (-b) option to specify a kext by its CFBundleIdentifier:

    kextutil -b com.mycompany.driver.TabletDriver

With no additional options kextutil looks in /System/Library/Extensions/ and /Library/Extensions/ for a kext with the given CFBundleIdentifier. Adding repository directories with the -repository (-r) option or individual kexts with the -dependency (-d) option expands the set of kexts that kextutil looks among:

    kextutil -r ${USER}/Library/Extensions TabletDriver.kext

  Diagnosing Kexts
kextutil prints diagnostic information about kexts by default, but some options cause certain tests to be skipped. The ensure that all tests are performed, use the -print-diagnostics (-t) option.

The -print-diagnostics option is typically used with -no-load (-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 -no-system-extensions (-e) and -no-resolve-dependencies (-Z) options to omit the /System/Library/Extensions/ and /Library/Extensions/ repositories and to suppress dependency resolution, respectively:

    kextutil -entZ PacketSniffer.kext

Only validation and authentication checks are performed.

  Generating Debug Symbols When Loading
To generate a symbol file for use with gdb when loading a kext, use the -symbols (-s) option to specify a directory where symbol files will be written for the kext being loaded and all its dependencies.

    kextutil -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 -symbols (-s) option along with the -no-load (-n) option. Since in this case addresses must be known for the kext and all its dependencies, though, you must specify them. If you don't indicate them on the command line, kextutil asks for the load address of each kext needed. To get these addresses you can use kextstat(8) on the machine you're generating symbols for, the showallkmods gdb(1) macro defined by the kgmacros file in the Kernel Development Kit, or consult a panic backtrace.

    kextutil -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 -address (-a) option for each kext (you needn't specify -no-load when using the -address option):

    kextutil -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 kextutil on the same machine as the loaded kext, is to use the -use-load-addresses (-A) option, which checks with the kernel for all loaded kexts and automatically gets their load addresses.

    kextutil -s ~/ksyms -A GrobbleEthernet.kext

  Explicitly Specifying Dependencies
Because kextutil resolves dependencies automatically, it's possible that a kext other than the one you intend might get used as a dependency (as when there are multiple copies of the same version, or if you're working with a different version of a kext that's already in /System/Library/Extensions/). By default, when loading a kext into the kernel, kextutil checks which versions of possible dependencies are already loaded in order to assure a successful load. When not loading and not using -use-load-addresses, however, it always chooses the highest versions of any dependencies, and in the case of a tie it chooses from kexts specified on the command line using the -dependency or -repository options, or as command line arguments (in decreasing order of priority).

For precise control over the set of extensions used to resolve dependencies, use the -no-system-extensions (-e) option along with the -dependency (-d), and -repository (-r) options. The -no-system-extensions option excludes the standard /System/Library/Extensions/ and /Library/Extensions/ directories, leaving the set of candidate extensions for dependency resolution entirely up to you. To specify candidate dependencies you use either -dependency (-d), which names a single kext as a candidate, or -repository (-r), which adds an entire directory of extensions.

    kextutil -n -s ~/ksyms -e \
        -d /System/Library/Extensions/System.kext \
        -r ~/TestKexts -d JoystickSupport.kext JoystickDriver.kext

Note also that if you use -no-system-extensions (-e), you must supply at least some version of System.kext 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 kextutil on; you can use the -kernel (-k) option to specify a different kernel file. You may also need to explicitly specify other library or family kexts.

  Debug Loading an I/O Kit Driver
Pure I/O Kit driver kexts have empty module-start routines, but trigger matching and driver instance creation on load. If you need to debug an I/O Kit driver's early startup code, you can load the driver on the target machine without starting matching by using the -load-only (-l) option:

    kextutil -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 kextutil again on the target machine with the -match-only (-m) option:

    kextutil -m DiskController.kext

You may wish to use the -personality (-p) option as well in order to send selected personalities to the kernel. Alternatively, you can use the -interactive (-i) option for the whole process, which causes kextutil to pause just before loading any personalities and then to ask you for each personality whether that one should be sent to the kernel:

    kextutil -i DiskController.kext
    DiskController.kext appears to be loadable (not including linkage
    for on-disk libraries).
    Load DiskController.kext and its dependencies into the kernel [Y/n]? y
    Loading DiskController.kext.
    DiskController.kext successfully loaded (or already loaded).
    DiskController.kext and its dependencies are now loaded,
    but not started (unless they were already running).
    You may now set breakpoints in the debugger before starting them.
    start DiskController.kext [Y/n]? y
    DiskController.kext started.
    send personalities for DiskController.kext [Y/n]? y
    send personality Test Match Personality [Y/n]? y

  Debug Loading a Kext with a Module-Start Routine
In order to debug a kext's module-start routine, you must use the -interactive (-i) or -interactive-all (-I) option, which pause after loading and before calling the module-start function, so that you can set up your debugging session as needed before proceeding.

FILES
/System/Library/Extensions/
    The standard system repository of kernel extensions.
/Library/Extensions/
    The standard repository of non Apple kernel extensions.
/System/Library/Caches/com.apple.kext.caches/*
    Contains all kext caches for a Mac OS X 10.6 (Snow Leopard) system: prelinked kernel, mkext, and system kext info caches.
/System/Library/Kernels/kernel
    The default kernel file.

DIAGNOSTICS
kextutil exits with a zero status upon success. Upon failure, it prints an error message and continues processing remaining kexts if possible, then exits with a nonzero status.

For a kext to be loadable, it must be valid, authentic, have all dependencies met (that is, all dependencies must be found and loadable). A valid kext has a well formed bundle, info dictionary, and executable. An authentic kext's component files are owned by root:wheel, with permissions nonwritable by group and other. If your kext fails to load, try using the -print-diagnostics (-t) option to print diagnostics related to validation and authentication.

BUGS
Many single-letter options are inconsistent in meaning with (or directly contradictory to) the same letter options in other kext tools.

SEE ALSO
kextcache(8), kextd(8), kextload(8), kextstat(8), kextunload(8), kext_logging(8)