Q: How do I tell whether a kernel function is part of a supported KPI?A: There are two basic criteria: Checking the first criterion is easy: use your favorite text search tool to see if the function is declared in the Kernel framework headers. There are two ways to check the second criterion. If you have already built a KEXT, you can use the kextlibs tool to determine the KPI symbol sets that it requires. See the man page for more details. If you haven't yet built a KEXT, you can use the FindKPI.py script to determine the KPI symbol set, if any, for a given symbol. Listing 1 shows an example of this.
Listing 1: Using FindKPI.py
$ ./FindKPI.py vnode_create lck_mtx_lock
vnode_create com.apple.kpi.bsd
lck_mtx_lock com.apple.kpi.libkern
$ # You can also supply C++ class names.
$ ./FindKPI.py OSDictionary IOMemoryDescriptor
OSDictionary com.apple.kpi.libkern
IOMemoryDescriptor com.apple.kpi.iokit
Of course, there are exceptions to every rule. For example: The header <sys/appleapiopts.h> defines a set of compile-time variables that are used to indicate the stability of a particular interface. Some of these—specifically __APPLE_API_EVOLVING, __APPLE_API_UNSTABLE, __APPLE_API_PRIVATE and __APPLE_API_OBSOLETE—are used to guard KPIs that are not 100% stable. You should try to avoid such KPIs where possible. To check whether you depend on such KPIs, define the compile-time variable __APPLE_API_STRICT_CONFORMANCE. Technical Q&A QA1574, 'Kernel's MAC framework' documents a bug that might mislead you into thinking that the kernel's MAC framework is a supported KPI. The com.apple.kpi.unsupported KPI is a compatibility measure intended for use by a limited number of Apple KEXTs. Your KEXT should not depend on this unsupported functionality.
DownloadablesBack to Top  Document Revision History| Date | Notes |
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| 2008-03-25 | First Version |
Posted: 2008-03-25
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