Generate Debug Symbols and Prepare Kexts for Loading

Use the kextutil utility to generate debug symbols for your kext, and to test whether your kext can be loaded. While you are debugging your kext, you should use kextutil to load your kext instead of kextload.

Commonly used kextutil options include:

-n / -no-load

Does not actually load the kext into the kernel. This option is useful when you only want to generate debug symbols or determine whether a kext can be loaded.

-s / -symbols

Generates debug symbols for the kext in the directory specified after this option.

-t / -print-diagnostics

Outputs whether or not the kext appears to be loadable, along with a diagnosis if the kext doesn’t seem to be loadable.

-e / -no-system-extensions and -r / -repository

Typically used together, these indicate that System/Library/Extensions should not be used as the default kext repository when resolving dependencies for your kext, and a specified folder should be used instead.

The kextutil utility includes additional options for simulating various load situations. See the kextutil man page for more information.

Output the Status of Loaded Kexts

Use the kextstat utility to output the following information for each kext loaded in the kernel:

  • The load index of the kext (used to track linkage references)

  • The number of references to the kext from other kexts

  • The kernel-space memory address of the kext

  • The size, in bytes, of the kext

  • The amount of wired memory, in bytes, occupied by the kext

  • The bundle identifier of the kext

  • The bundle version of the kext

  • The load indices of other kexts that the kext has a reference to

See kextstat for more information.

Determine Kext Dependencies

Use the kextlibs utility to determine which library kexts your kext must link against in order to resolve its symbols. You must list the bundle identifiers of these library kexts in the OSBundleLibraries dictionary of your kext’s information property list.

Commonly used kextlibs options include:

-xml

Produces XML output you can copy and paste for the OSBundleLibraries dictionary of your kext’s information property list.

-undef-symbols

Displays symbols that kextlibs could not locate. You may be able to locate these symbols by using the kextfind utility.

See kextlibs for more information.

Locate Kexts

Use the kextfind utility to search for kexts with custom queries. In addition to its query predicates, kextfind includes predicates for generating tab-delimited reports for further processing.

Commonly used kextfind query predicates include:

-dsym / -defines-symbol

Prints only kexts that define the symbol specified after this option. This predicate is useful for locating symbols in your kext that kextlibs can’t locate.

-lib / -library

Returns only library kexts that other kexts can link against.

The kextfind utility contains many more query predicates and report predicates you can use to fine-tune your search. See kextfind(8) for more information.

Obtain Instance Counts

Use the ioclasscount utility to obtain the current number of instances of any given subclass of the OSObject C++ class (which includes virtually all built-in kernel classes). The instance count returned for a class includes the number of instances of that class’s direct subclasses. You can use ioclasscount to discover leaked instances that you should have deallocated before your kext was unloaded.

See ioclasscount for more information.

View the I/O Kit Registry

Use the IORegistryExplorer application (located in /Developer/Applications/Utilities) to view the current state of the I/O Kit registry. IORegistryExplorer also includes several searching and browsing options to help you navigate the registry.