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Installing Shutdown Hooks

Although Mac OS X does not have traditional BSD-style shutdown hooks, the I/O Kit provides equivalent functionality in recent versions. Since the I/O Kit provides this functionality, you must call it from C++ code.

To register for notification, you call registerSleepWakeInterest (described in IOKit/RootDomain.h) and register for sleep notification. If the system is about to be shut down, your handler is called with the message type kIOMessageSystemWillPowerOff. If the system is about to reboot, your handler gets the message type kIOMessageSystemWillRestart. If the system is about to reboot, your handler gets the message type kIOMessageSystemWillSleep.

If you no longer need to receive notification (for example, if your KEXT gets unloaded), be certain to release the notifier with IONofitier::release to avoid a kernel panic on shutdown.

For example, the following sample KEXT registers for sleep notifications, then logs a message with IOLog when a sleep notification occurs:

#include <IOKit/IOLib.h>

#include <IOKit/pwr_mgt/RootDomain.h>

#include <IOKit/pwr_mgt/IOPM.h>

#include <IOKit/IOService.h>

#include <IOKit/IONotifier.h>

#define ALLOW_SLEEP 1

IONotifier *notifier;

extern "C" {

IOReturn mySleepHandler( void * target, void * refCon,

    UInt32 messageType, IOService * provider,

    void * messageArgument, vm_size_t argSize )

{

    IOLog("Got sleep/wake notice.  Message type was %d\n", messageType);

#if ALLOW_SLEEP

    acknowledgeSleepWakeNotification(refCon);

#else

    vetoSleepWakeNotification(refCon);

#endif

    return 0;

}

kern_return_t sleepkext_start (kmod_info_t * ki, void * d) {

        void *myself = NULL; // Would pass the self pointer here if in a class instance

        notifier = registerPrioritySleepWakeInterest(

                &mySleepHandler, myself, NULL);

    return KERN_SUCCESS;

}

kern_return_t sleepkext_stop (kmod_info_t * ki, void * d) {

    notifier->remove();

    return KERN_SUCCESS;

}

} // extern "C"

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