xref: /xnu-11215/libkern/c++/OSMetaClass.cpp (revision bb611c8f)

/*
 * Copyright (c) 2000-2016 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/* OSMetaClass.cpp created by gvdl on Fri 1998-11-17 */

#include <string.h>

#include <libkern/OSReturn.h>

#include <libkern/c++/OSMetaClass.h>
#include <libkern/c++/OSObject.h>
#include <libkern/c++/OSKext.h>

#include <libkern/c++/OSCollectionIterator.h>
#include <libkern/c++/OSDictionary.h>
#include <libkern/c++/OSArray.h>
#include <libkern/c++/OSSet.h>
#include <libkern/c++/OSSymbol.h>
#include <libkern/c++/OSNumber.h>
#include <libkern/c++/OSSerialize.h>

#include <libkern/c++/OSLib.h>
#include <libkern/OSAtomic.h>

#include <IOKit/IOLib.h>

#include <IOKit/IOKitDebug.h>


__BEGIN_DECLS

#include <sys/systm.h>
#include <mach/mach_types.h>
#include <kern/locks.h>
#include <kern/clock.h>
#include <kern/thread_call.h>
#include <kern/host.h>
#include <mach/mach_interface.h>
#include <stddef.h>

#if PRAGMA_MARK
#pragma mark Macros
#endif /* PRAGMA_MARK */
/*********************************************************************
* Macros
*********************************************************************/
__END_DECLS

#if PRAGMA_MARK
#pragma mark Internal constants & data structs
#endif /* PRAGMA_MARK */
/*********************************************************************
* Internal constants & data structs
*********************************************************************/
OSKextLogSpec kOSMetaClassLogSpec =
    kOSKextLogErrorLevel |
    kOSKextLogLoadFlag |
    kOSKextLogKextBookkeepingFlag;

static enum {
	kCompletedBootstrap = 0,
	kNoDictionaries     = 1,
	kMakingDictionaries = 2
} sBootstrapState = kNoDictionaries;

static const int      kClassCapacityIncrement = 40;
static const int      kKModCapacityIncrement  = 10;
static OSDictionary * sAllClassesDict;
static unsigned int   sDeepestClass;
IOLock              * sAllClassesLock = NULL;
IOLock              * sInstancesLock  = NULL;

/*
 * While loading a kext and running all its constructors to register
 * all OSMetaClass classes, the classes are queued up here. Only one
 * kext can be in flight at a time, guarded by sStalledClassesLock
 */
static struct StalledData {
	const char   * kextIdentifier;
	OSReturn       result;
	unsigned int   capacity;
	unsigned int   count;
	OSMetaClass ** classes;
} * sStalled;
IOLock * sStalledClassesLock = NULL;

struct ExpansionData {
	OSOrderedSet    * instances;
	OSKext          * kext;
	uint32_t          retain;
#if IOTRACKING
	IOTrackingQueue * tracking;
#endif
};


#if PRAGMA_MARK
#pragma mark OSMetaClassBase
#endif /* PRAGMA_MARK */
/*********************************************************************
* OSMetaClassBase.
*********************************************************************/

#if APPLE_KEXT_VTABLE_PADDING
/*********************************************************************
* Reserved vtable functions.
*********************************************************************/
#if defined(__arm64__) || defined(__arm__)
void
OSMetaClassBase::_RESERVEDOSMetaClassBase0()
{
	panic("OSMetaClassBase::_RESERVEDOSMetaClassBase%d called.", 0);
}
void
OSMetaClassBase::_RESERVEDOSMetaClassBase1()
{
	panic("OSMetaClassBase::_RESERVEDOSMetaClassBase%d called.", 1);
}
void
OSMetaClassBase::_RESERVEDOSMetaClassBase2()
{
	panic("OSMetaClassBase::_RESERVEDOSMetaClassBase%d called.", 2);
}
void
OSMetaClassBase::_RESERVEDOSMetaClassBase3()
{
	panic("OSMetaClassBase::_RESERVEDOSMetaClassBase%d called.", 3);
}
#endif /* defined(__arm64__) || defined(__arm__) */

// As these slots are used move them up inside the #if above
void
OSMetaClassBase::_RESERVEDOSMetaClassBase4()
{
	panic("OSMetaClassBase::_RESERVEDOSMetaClassBase%d called.", 4);
}
void
OSMetaClassBase::_RESERVEDOSMetaClassBase5()
{
	panic("OSMetaClassBase::_RESERVEDOSMetaClassBase%d called.", 5);
}
void
OSMetaClassBase::_RESERVEDOSMetaClassBase6()
{
	panic("OSMetaClassBase::_RESERVEDOSMetaClassBase%d called.", 6);
}
#endif

/*********************************************************************
*********************************************************************/

#if defined(__arm__) || defined(__arm64__)

#if defined(HAS_APPLE_PAC)
#include <ptrauth.h>
#endif /* defined(HAS_APPLE_PAC) */

/*
 *  IHI0059A "C++ Application Binary Interface Standard for the ARM 64 - bit Architecture":
 *
 *  3.2.1 Representation of pointer to member function The generic C++ ABI [GC++ABI]
 *  specifies that a pointer to member function is a pair of words <ptr, adj>. The
 *  least significant bit of ptr discriminates between (0) the address of a non-
 *  virtual member function and (1) the offset in the class's virtual table of the
 *  address of a virtual function. This encoding cannot work for the AArch64
 *  instruction set where the architecture reserves all bits of code addresses. This
 *  ABI specifies that adj contains twice the this adjustment, plus 1 if the member
 *  function is virtual. The least significant bit of adj then makes exactly the
 *  same discrimination as the least significant bit of ptr does for Itanium. A
 *  pointer to member function is NULL when ptr = 0 and the least significant bit of
 *  adj is zero.
 */

OSMetaClassBase::_ptf_t
#if defined(HAS_APPLE_PAC) && \
        __has_feature(ptrauth_member_function_pointer_type_discrimination)
OSMetaClassBase::_ptmf2ptf(const OSMetaClassBase *self __attribute__((unused)),
    void (OSMetaClassBase::*func)(void))
#else
OSMetaClassBase::_ptmf2ptf(const OSMetaClassBase *self,
    void (OSMetaClassBase::*func)(void))
#endif
{
	struct ptmf_t {
		_ptf_t fPFN;
		ptrdiff_t delta;
	};
	union {
		void (OSMetaClassBase::*fIn)(void);
		struct ptmf_t pTMF;
	} map;
	_ptf_t pfn;

	map.fIn = func;
	pfn     = map.pTMF.fPFN;

#if defined(HAS_APPLE_PAC) && \
	__has_feature(ptrauth_member_function_pointer_type_discrimination)
	// Authenticate 'pfn' using the member function pointer type discriminator
	// and resign it as a C function pointer. 'pfn' can point to either a
	// non-virtual function or a virtual member function thunk.
	// It can also be NULL.
	if (pfn) {
		pfn = ptrauth_auth_and_resign(pfn, ptrauth_key_function_pointer,
		    ptrauth_type_discriminator(__typeof__(func)),
		    ptrauth_key_function_pointer,
		    ptrauth_function_pointer_type_discriminator(_ptf_t));
	}
	return pfn;
#else
	if (map.pTMF.delta & 1) {
		// virtual
		union {
			const OSMetaClassBase *fObj;
			_ptf_t **vtablep;
		} u;
		u.fObj = self;

		// Virtual member function so dereference table
#if defined(HAS_APPLE_PAC)
		// The entity hash is stored in the top 32-bits of the vtable offset of a
		// member function pointer.
		uint32_t entity_hash = ((uintptr_t)pfn) >> 32;
		pfn = (_ptf_t)(((uintptr_t) pfn) & 0xFFFFFFFF);

#if __has_builtin(__builtin_get_vtable_pointer)
		const _ptf_t *vtablep =
		    (const _ptf_t *)__builtin_get_vtable_pointer(u.fObj);
#else
		// Authenticate the vtable pointer.
		const _ptf_t *vtablep = ptrauth_auth_data(*u.vtablep,
		    ptrauth_key_cxx_vtable_pointer, 0);
#endif
		// Calculate the address of the vtable entry.
		_ptf_t *vtentryp = (_ptf_t *)(((uintptr_t)vtablep) + (uintptr_t)pfn);
		// Load the pointer from the vtable entry.
		pfn = *vtentryp;

		// Finally, resign the vtable entry as a function pointer.
		uintptr_t auth_data = ptrauth_blend_discriminator(vtentryp, entity_hash);
		pfn = ptrauth_auth_and_resign(pfn, ptrauth_key_function_pointer,
		    auth_data, ptrauth_key_function_pointer,
		    ptrauth_function_pointer_type_discriminator(_ptf_t));
#else /* defined(HAS_APPLE_PAC) */
		pfn = *(_ptf_t *)(((uintptr_t)*u.vtablep) + (uintptr_t)pfn);
#endif /* !defined(HAS_APPLE_PAC) */
		return pfn;
	} else {
		// Not virtual, i.e. plain member func
		return pfn;
	}
#endif
}

#endif /* defined(__arm__) || defined(__arm64__) */
/*********************************************************************
* These used to be inline in the header but gcc didn't believe us
* Now we MUST pull the inline out at least until the compiler is
* repaired.
*
* Helper inlines for runtime type preprocessor macros
*********************************************************************/

/*********************************************************************
*********************************************************************/
OSMetaClassBase *
OSMetaClassBase::safeMetaCast(
	const OSMetaClassBase * me,
	const OSMetaClass     * toType)
{
	return (me)? me->metaCast(toType) : NULL;
}

/// A helper function to crash with a kernel panic.
__attribute__((cold, not_tail_called, noreturn))
static inline void
panic_crash_fail_cast(const OSMetaClassBase *me,
    const OSMetaClass *toType)
{
	panic("Unexpected cast fail: from %p to %p", me, toType);
	__builtin_unreachable();
}

OSMetaClassBase *
OSMetaClassBase::requiredMetaCast(
	const OSMetaClassBase * me,
	const OSMetaClass     * toType)
{
	if (!me) {
		return NULL;
	}
	OSMetaClassBase *tmp = safeMetaCast(me, toType);
	if (!tmp) {
		panic_crash_fail_cast(me, toType);
	}
	return tmp;
}

/*********************************************************************
*********************************************************************/
bool
OSMetaClassBase::checkTypeInst(
	const OSMetaClassBase * inst,
	const OSMetaClassBase * typeinst)
{
	const OSMetaClass * toType = OSTypeIDInst(typeinst);
	return typeinst && inst && (NULL != inst->metaCast(toType));
}

/*********************************************************************
*********************************************************************/
void
OSMetaClassBase::
initialize()
{
	sAllClassesLock = IOLockAlloc();
	sStalledClassesLock = IOLockAlloc();
	sInstancesLock = IOLockAlloc();
}

#if APPLE_KEXT_VTABLE_PADDING
/*********************************************************************
* If you need this slot you had better setup an IOCTL style interface.
* 'Cause the whole kernel world depends on OSMetaClassBase and YOU
* CANT change the VTABLE size ever.
*********************************************************************/
void
OSMetaClassBase::_RESERVEDOSMetaClassBase7()
{
	panic("OSMetaClassBase::_RESERVEDOSMetaClassBase%d called.", 7);
}
#endif

/*********************************************************************
*********************************************************************/
OSMetaClassBase::OSMetaClassBase()
{
}

/*********************************************************************
*********************************************************************/
OSMetaClassBase::~OSMetaClassBase()
{
	void ** thisVTable;

	thisVTable = (void **) this;
	*thisVTable = (void *) -1UL;
}

/*********************************************************************
*********************************************************************/
bool
OSMetaClassBase::isEqualTo(const OSMetaClassBase * anObj) const
{
	return this == anObj;
}

/*********************************************************************
*********************************************************************/
OSMetaClassBase *
OSMetaClassBase::metaCast(const OSMetaClass * toMeta) const
{
	return toMeta->checkMetaCast(this);
}

/*********************************************************************
*********************************************************************/
OSMetaClassBase *
OSMetaClassBase::metaCast(const OSSymbol * toMetaSymb) const
{
	return OSMetaClass::checkMetaCastWithName(toMetaSymb, this);
}

/*********************************************************************
*********************************************************************/
OSMetaClassBase *
OSMetaClassBase::metaCast(const OSString * toMetaStr) const
{
	const OSSymbol  * tempSymb = OSSymbol::withString(toMetaStr);
	OSMetaClassBase * ret = NULL;
	if (tempSymb) {
		ret = metaCast(tempSymb);
		tempSymb->release();
	}
	return ret;
}

/*********************************************************************
*********************************************************************/
OSMetaClassBase *
OSMetaClassBase::metaCast(const char * toMetaCStr) const
{
	const OSSymbol  * tempSymb = OSSymbol::withCString(toMetaCStr);
	OSMetaClassBase * ret = NULL;
	if (tempSymb) {
		ret = metaCast(tempSymb);
		tempSymb->release();
	}
	return ret;
}

#if PRAGMA_MARK
#pragma mark OSMetaClassMeta
#endif /* PRAGMA_MARK */
/*********************************************************************
* OSMetaClassMeta - the bootstrap metaclass of OSMetaClass
*********************************************************************/
class OSMetaClassMeta : public OSMetaClass
{
public:
	OSMetaClassMeta();
	OSObject * alloc() const;
};
OSMetaClassMeta::OSMetaClassMeta()
	: OSMetaClass("OSMetaClass", NULL, sizeof(OSMetaClass))
{
}
OSObject *
OSMetaClassMeta::alloc() const
{
	return NULL;
}

static OSMetaClassMeta sOSMetaClassMeta;

const OSMetaClass * const OSMetaClass::metaClass = &sOSMetaClassMeta;
const OSMetaClass *
OSMetaClass::getMetaClass() const
{
	return &sOSMetaClassMeta;
}

#if PRAGMA_MARK
#pragma mark OSMetaClass
#endif /* PRAGMA_MARK */
/*********************************************************************
* OSMetaClass
*********************************************************************/

#if APPLE_KEXT_VTABLE_PADDING
/*********************************************************************
* Reserved functions.
*********************************************************************/
void
OSMetaClass::_RESERVEDOSMetaClass0()
{
	panic("OSMetaClass::_RESERVEDOSMetaClass%d called", 0);
}
void
OSMetaClass::_RESERVEDOSMetaClass1()
{
	panic("OSMetaClass::_RESERVEDOSMetaClass%d called", 1);
}
void
OSMetaClass::_RESERVEDOSMetaClass2()
{
	panic("OSMetaClass::_RESERVEDOSMetaClass%d called", 2);
}
void
OSMetaClass::_RESERVEDOSMetaClass3()
{
	panic("OSMetaClass::_RESERVEDOSMetaClass%d called", 3);
}
void
OSMetaClass::_RESERVEDOSMetaClass4()
{
	panic("OSMetaClass::_RESERVEDOSMetaClass%d called", 4);
}
void
OSMetaClass::_RESERVEDOSMetaClass5()
{
	panic("OSMetaClass::_RESERVEDOSMetaClass%d called", 5);
}
void
OSMetaClass::_RESERVEDOSMetaClass6()
{
	panic("OSMetaClass::_RESERVEDOSMetaClass%d called", 6);
}
void
OSMetaClass::_RESERVEDOSMetaClass7()
{
	panic("OSMetaClass::_RESERVEDOSMetaClass%d called", 7);
}
#endif

/*********************************************************************
*********************************************************************/
static void
OSMetaClassLogErrorForKext(
	OSReturn   error,
	OSKext   * aKext)
{
	const char * message = NULL;

	switch (error) {
	case kOSReturnSuccess:
		return;
	case kOSMetaClassNoInit: // xxx - never returned; logged at fail site
		message = "OSMetaClass: preModLoad() wasn't called (runtime internal error).";
		break;
	case kOSMetaClassNoDicts:
		message = "OSMetaClass: Allocation failure for OSMetaClass internal dictionaries.";
		break;
	case kOSMetaClassNoKModSet:
		message = "OSMetaClass: Allocation failure for internal kext recording set/set missing.";
		break;
	case kOSMetaClassNoInsKModSet:
		message = "OSMetaClass: Failed to record class in kext.";
		break;
	case kOSMetaClassDuplicateClass:
		message = "OSMetaClass: Duplicate class encountered.";
		break;
	case kOSMetaClassNoSuper: // xxx - never returned
		message = "OSMetaClass: Can't associate a class with its superclass.";
		break;
	case kOSMetaClassInstNoSuper: // xxx - never returned
		message = "OSMetaClass: Instance construction error; unknown superclass.";
		break;
	case kOSMetaClassNoKext:
		message = "OSMetaClass: Kext not found for metaclass.";
		break;
	case kOSMetaClassInternal:
	default:
		message = "OSMetaClass: Runtime internal error.";
		break;
	}

	if (message) {
		OSKextLog(aKext, kOSMetaClassLogSpec, "%s", message);
	}
	return;
}

void
OSMetaClass::logError(OSReturn error)
{
	OSMetaClassLogErrorForKext(error, NULL);
}

/*********************************************************************
* The core constructor for a MetaClass (defined with this name always
* but within the scope of its represented class).
*
* MetaClass constructors are invoked in OSRuntimeInitializeCPP(),
* in between calls to OSMetaClass::preModLoad(), which sets up for
* registration, and OSMetaClass::postModLoad(), which actually
* records all the class/kext relationships of the new MetaClasses.
*********************************************************************/

OSMetaClass::OSMetaClass(
	const char        * inClassName,
	const OSMetaClass * inSuperClass,
	unsigned int        inClassSize)
{
	instanceCount = 0;
	classSize = inClassSize;
	superClassLink = inSuperClass;

	reserved = IONew(ExpansionData, 1);
	bzero(reserved, sizeof(ExpansionData));
#if IOTRACKING
	uint32_t numSiteQs = 0;
	if ((this == &OSSymbol    ::gMetaClass)
	    || (this == &OSString    ::gMetaClass)
	    || (this == &OSNumber    ::gMetaClass)
	    || (this == &OSString    ::gMetaClass)
	    || (this == &OSData      ::gMetaClass)
	    || (this == &OSDictionary::gMetaClass)
	    || (this == &OSArray     ::gMetaClass)
	    || (this == &OSSet       ::gMetaClass)) {
		numSiteQs = 27;
	}

	reserved->tracking = IOTrackingQueueAlloc(inClassName, (uintptr_t) this,
	    inClassSize, 0, kIOTrackingQueueTypeAlloc,
	    numSiteQs);
#endif

	/* Hack alert: We are just casting inClassName and storing it in
	 * an OSString * instance variable. This may be because you can't
	 * create C++ objects in static constructors, but I really don't know!
	 */
	className = (const OSSymbol *)inClassName;

	// sStalledClassesLock taken in preModLoad
	if (!sStalled) {
		/* There's no way we can look up the kext here, unfortunately.
		 */
		OSKextLog(/* kext */ NULL, kOSMetaClassLogSpec,
		    "OSMetaClass: preModLoad() wasn't called for class %s "
		    "(runtime internal error).",
		    inClassName);
	} else if (!sStalled->result) {
		// Grow stalled array if neccessary
		if (sStalled->count >= sStalled->capacity) {
			OSMetaClass **oldStalled = sStalled->classes;
			int oldSize = sStalled->capacity * sizeof(OSMetaClass *);
			int newSize = oldSize
			    + kKModCapacityIncrement * sizeof(OSMetaClass *);

			sStalled->classes = (OSMetaClass **)kalloc_tag(newSize, VM_KERN_MEMORY_OSKEXT);
			if (!sStalled->classes) {
				sStalled->classes = oldStalled;
				sStalled->result = kOSMetaClassNoTempData;
				return;
			}

			sStalled->capacity += kKModCapacityIncrement;
			memmove(sStalled->classes, oldStalled, oldSize);
			kfree(oldStalled, oldSize);
			OSMETA_ACCUMSIZE(((size_t)newSize) - ((size_t)oldSize));
		}

		sStalled->classes[sStalled->count++] = this;
	}
}

OSMetaClass::OSMetaClass(
	const char        * inClassName,
	const OSMetaClass * inSuperClass,
	unsigned int        inClassSize,
	zone_t            * inZone,
	const char        * zone_name,
	zone_create_flags_t zflags) : OSMetaClass(inClassName, inSuperClass,
	    inClassSize)
{
	if (!(kIOTracking & gIOKitDebug)) {
		*inZone  = zone_create(zone_name, inClassSize,
		    (zone_create_flags_t) (ZC_ZFREE_CLEARMEM | zflags));
	}
}

/*********************************************************************
*********************************************************************/
OSMetaClass::~OSMetaClass()
{
	OSKext * myKext = reserved->kext; // do not release

	/* Hack alert: 'className' is a C string during early C++ init, and
	 * is converted to a real OSSymbol only when we record the OSKext in
	 * OSMetaClass::postModLoad(). So only do this bit if we have an OSKext.
	 * We can't safely cast or check 'className'.
	 *
	 * Also, release className *after* calling into the kext,
	 * as removeClass() may access className.
	 */
	IOLockLock(sAllClassesLock);
	if (sAllClassesDict) {
		if (myKext) {
			sAllClassesDict->removeObject(className);
		} else {
			sAllClassesDict->removeObject((const char *)className);
		}
	}
	IOLockUnlock(sAllClassesLock);

	if (myKext) {
		if (myKext->removeClass(this) != kOSReturnSuccess) {
			// xxx - what can we do?
		}
		className->release();
	}

	// sStalledClassesLock taken in preModLoad
	if (sStalled) {
		unsigned int i;

		/* First pass find class in stalled list. If we find it that means
		 * we started C++ init with constructors but now we're tearing down
		 * because of some failure.
		 */
		for (i = 0; i < sStalled->count; i++) {
			if (this == sStalled->classes[i]) {
				break;
			}
		}

		/* Remove this metaclass from the stalled list so postModLoad() doesn't
		 * try to register it.
		 */
		if (i < sStalled->count) {
			sStalled->count--;
			if (i < sStalled->count) {
				memmove(&sStalled->classes[i], &sStalled->classes[i + 1],
				    (sStalled->count - i) * sizeof(OSMetaClass *));
			}
		}
	}
#if IOTRACKING
	IOTrackingQueueFree(reserved->tracking);
#endif
	IODelete(reserved, ExpansionData, 1);
}

/*********************************************************************
* Empty overrides.
*********************************************************************/
void
OSMetaClass::retain() const
{
}
void
OSMetaClass::release() const
{
}
void
OSMetaClass::release(__unused int when) const
{
}
void
OSMetaClass::taggedRetain(__unused const void * tag) const
{
}
void
OSMetaClass::taggedRelease(__unused const void * tag) const
{
}
void
OSMetaClass::taggedRelease(__unused const void * tag, __unused const int when) const
{
}
int
OSMetaClass::getRetainCount() const
{
	return 0;
}

/*********************************************************************
*********************************************************************/
const char *
OSMetaClass::getClassName() const
{
	if (!className) {
		return NULL;
	}
	return className->getCStringNoCopy();
}
/*********************************************************************
*********************************************************************/
const OSSymbol *
OSMetaClass::getClassNameSymbol() const
{
	return className;
}
/*********************************************************************
*********************************************************************/
unsigned int
OSMetaClass::getClassSize() const
{
	return classSize;
}

/*********************************************************************
*********************************************************************/
void *
OSMetaClass::preModLoad(const char * kextIdentifier)
{
	IOLockLock(sStalledClassesLock);

	assert(sStalled == NULL);
	sStalled = (StalledData *)kalloc_tag(sizeof(*sStalled), VM_KERN_MEMORY_OSKEXT);
	if (sStalled) {
		sStalled->classes = (OSMetaClass **)
		    kalloc_tag(kKModCapacityIncrement * sizeof(OSMetaClass *), VM_KERN_MEMORY_OSKEXT);
		if (!sStalled->classes) {
			kfree(sStalled, sizeof(*sStalled));
			return NULL;
		}
		OSMETA_ACCUMSIZE((kKModCapacityIncrement * sizeof(OSMetaClass *)) +
		    sizeof(*sStalled));

		sStalled->result   = kOSReturnSuccess;
		sStalled->capacity = kKModCapacityIncrement;
		sStalled->count    = 0;
		sStalled->kextIdentifier = kextIdentifier;
		bzero(sStalled->classes, kKModCapacityIncrement * sizeof(OSMetaClass *));
	}

	// keep sStalledClassesLock locked until postModLoad

	return sStalled;
}

/*********************************************************************
*********************************************************************/
bool
OSMetaClass::checkModLoad(void * loadHandle)
{
	return sStalled && loadHandle == sStalled &&
	       sStalled->result == kOSReturnSuccess;
}

/*********************************************************************
*********************************************************************/
OSReturn
OSMetaClass::postModLoad(void * loadHandle)
{
	OSReturn         result     = kOSReturnSuccess;
	OSSymbol       * myKextName = NULL;// must release
	OSKext         * myKext     = NULL;// must release

	if (!sStalled || loadHandle != sStalled) {
		result = kOSMetaClassInternal;
		goto finish;
	}

	if (sStalled->result) {
		result = sStalled->result;
	} else {
		switch (sBootstrapState) {
		case kNoDictionaries:
			sBootstrapState = kMakingDictionaries;
			// No break; fall through
			[[clang::fallthrough]];

		case kMakingDictionaries:
			sAllClassesDict = OSDictionary::withCapacity(kClassCapacityIncrement);
			if (!sAllClassesDict) {
				result = kOSMetaClassNoDicts;
				break;
			}
			sAllClassesDict->setOptions(OSCollection::kSort, OSCollection::kSort);

			// No break; fall through
			[[clang::fallthrough]];

		case kCompletedBootstrap:
		{
			unsigned int i;
			myKextName = const_cast<OSSymbol *>(OSSymbol::withCStringNoCopy(
				    sStalled->kextIdentifier));

			if (!sStalled->count) {
				break; // Nothing to do so just get out
			}

			myKext = OSKext::lookupKextWithIdentifier(myKextName);
			if (!myKext) {
				result = kOSMetaClassNoKext;

				/* Log this error here so we can include the kext name.
				 */
				OSKextLog(/* kext */ NULL, kOSMetaClassLogSpec,
				    "OSMetaClass: Can't record classes for kext %s - kext not found.",
				    sStalled->kextIdentifier);
				break;
			}

			/* First pass checking classes aren't already loaded. If any already
			 * exist, we don't register any, and so we don't technically have
			 * to do any C++ teardown.
			 *
			 * Hack alert: me->className has been a C string until now.
			 * We only release the OSSymbol if we store the kext.
			 */
			IOLockLock(sAllClassesLock);
			for (i = 0; i < sStalled->count; i++) {
				const OSMetaClass * me = sStalled->classes[i];
				OSMetaClass * orig = OSDynamicCast(OSMetaClass,
				    sAllClassesDict->getObject((const char *)me->className));

				if (orig) {
					/* Log this error here so we can include the class name.
					 * xxx - we should look up the other kext that defines the class
					 */
#if defined(XNU_TARGET_OS_OSX)
					OSKextLog(myKext, kOSMetaClassLogSpec,
#else
					panic(
#endif /* defined(XNU_TARGET_OS_OSX) */
					    "OSMetaClass: Kext %s class %s is a duplicate;"
					    "kext %s already has a class by that name.",
					    sStalled->kextIdentifier, (const char *)me->className,
					    ((OSKext *)orig->reserved->kext)->getIdentifierCString());
					result = kOSMetaClassDuplicateClass;
					break;
				}
				unsigned int depth = 1;
				while ((me = me->superClassLink)) {
				        depth++;
				}
				if (depth > sDeepestClass) {
				        sDeepestClass = depth;
				}
			}
			IOLockUnlock(sAllClassesLock);

			/* Bail if we didn't go through the entire list of new classes
			 * (if we hit a duplicate).
			 */
			if (i != sStalled->count) {
			        break;
			}

			// Second pass symbolling strings and inserting classes in dictionary
			IOLockLock(sAllClassesLock);
			for (i = 0; i < sStalled->count; i++) {
			        OSMetaClass * me = sStalled->classes[i];

			        /* Hack alert: me->className has been a C string until now.
			         * We only release the OSSymbol in ~OSMetaClass()
			         * if we set the reference to the kext.
			         */
			        me->className =
			            OSSymbol::withCStringNoCopy((const char *)me->className);

			        // xxx - I suppose if these fail we're going to panic soon....
			        sAllClassesDict->setObject(me->className, me);

			        /* Do not retain the kext object here.
			         */
			        me->reserved->kext = myKext;
			        if (myKext) {
			                result = myKext->addClass(me, sStalled->count);
			                if (result != kOSReturnSuccess) {
			                        /* OSKext::addClass() logs with kOSMetaClassNoInsKModSet. */
			                        break;
					}
				}
			}
			IOLockUnlock(sAllClassesLock);
			sBootstrapState = kCompletedBootstrap;
			break;
		}

		default:
			result = kOSMetaClassInternal;
			break;
		}
	}

finish:
	/* Don't call logError() for success or the conditions logged above
	 * or by called function.
	 */
	if (result != kOSReturnSuccess &&
	    result != kOSMetaClassNoInsKModSet &&
	    result != kOSMetaClassDuplicateClass &&
	    result != kOSMetaClassNoKext) {
	        OSMetaClassLogErrorForKext(result, myKext);
	}

	OSSafeReleaseNULL(myKextName);
	OSSafeReleaseNULL(myKext);

	if (sStalled) {
	        OSMETA_ACCUMSIZE(-(sStalled->capacity * sizeof(OSMetaClass *) +
	            sizeof(*sStalled)));
	        kfree(sStalled->classes, sStalled->capacity * sizeof(OSMetaClass *));
	        kfree(sStalled, sizeof(*sStalled));
	        sStalled = NULL;
	}

	IOLockUnlock(sStalledClassesLock);

	return result;
}


/*********************************************************************
*********************************************************************/
void
OSMetaClass::instanceConstructed() const
{
        // if ((0 == OSIncrementAtomic(&(((OSMetaClass *) this)->instanceCount))) && superClassLink)
        if ((0 == OSIncrementAtomic(&instanceCount)) && superClassLink) {
                superClassLink->instanceConstructed();
	}
}

/*********************************************************************
*********************************************************************/
void
OSMetaClass::instanceDestructed() const
{
        if ((1 == OSDecrementAtomic(&instanceCount)) && superClassLink) {
                superClassLink->instanceDestructed();
	}

        if (((int)instanceCount) < 0) {
                OSKext * myKext = reserved->kext;

                OSKextLog(myKext, kOSMetaClassLogSpec,
                    // xxx - this phrasing is rather cryptic
                    "OSMetaClass: Class %s - bad retain (%d)",
                    getClassName(), instanceCount);
	}
}

/*********************************************************************
*********************************************************************/
bool
OSMetaClass::modHasInstance(const char * kextIdentifier)
{
        bool     result  = false;
        OSKext * theKext = NULL; // must release

        theKext = OSKext::lookupKextWithIdentifier(kextIdentifier);
        if (!theKext) {
                goto finish;
	}

        result = theKext->hasOSMetaClassInstances();

finish:
        OSSafeReleaseNULL(theKext);
        return result;
}

/*********************************************************************
*********************************************************************/
void
OSMetaClass::reportModInstances(const char * kextIdentifier)
{
        OSKext::reportOSMetaClassInstances(kextIdentifier,
            kOSKextLogExplicitLevel);
        return;
}
/*********************************************************************
*********************************************************************/

void
OSMetaClass::addInstance(const OSObject * instance, bool super) const
{
        if (!super) {
                IOLockLock(sInstancesLock);
	}

        if (!reserved->instances) {
                reserved->instances = OSOrderedSet::withCapacity(16);
                if (superClassLink) {
                        superClassLink->addInstance(reserved->instances, true);
		}
	}
        reserved->instances->setLastObject(instance);

        if (!super) {
                IOLockUnlock(sInstancesLock);
	}
}

void
OSMetaClass::removeInstance(const OSObject * instance, bool super) const
{
        if (!super) {
                IOLockLock(sInstancesLock);
	}

        if (reserved->instances) {
                reserved->instances->removeObject(instance);
                if (0 == reserved->instances->getCount()) {
                        if (superClassLink) {
                                superClassLink->removeInstance(reserved->instances, true);
			}
                        IOLockLock(sAllClassesLock);
                        reserved->instances->release();
                        reserved->instances = NULL;
                        IOLockUnlock(sAllClassesLock);
		}
	}

        if (!super) {
                IOLockUnlock(sInstancesLock);
	}
}

void
OSMetaClass::applyToInstances(OSOrderedSet * set,
    OSMetaClassInstanceApplierFunction  applier,
    void * context)
{
        enum {          kLocalDepth = 24 };
        unsigned int    _nextIndex[kLocalDepth];
        OSOrderedSet *  _sets[kLocalDepth];
        unsigned int *  nextIndex = &_nextIndex[0];
        OSOrderedSet ** sets      = &_sets[0];
        OSObject *      obj;
        OSOrderedSet *  childSet;
        unsigned int    maxDepth;
        unsigned int    idx;
        unsigned int    level;
        bool            done;

        maxDepth = sDeepestClass;
        if (maxDepth > kLocalDepth) {
                nextIndex = IONew(typeof(nextIndex[0]), maxDepth);
                sets      = IONew(typeof(sets[0]), maxDepth);
	}
        done = false;
        level = 0;
        idx = 0;
        do{
                while (!done && (obj = set->getObject(idx++))) {
                        if ((childSet = OSDynamicCast(OSOrderedSet, obj))) {
                                if (level >= maxDepth) {
                                        panic(">maxDepth");
				}
                                sets[level] = set;
                                nextIndex[level] = idx;
                                level++;
                                set = childSet;
                                idx = 0;
                                break;
			}
                        done = (*applier)(obj, context);
		}
                if (!obj) {
                        if (!done && level) {
                                level--;
                                set = sets[level];
                                idx = nextIndex[level];
			} else {
                                done = true;
			}
		}
	}while (!done);
        if (maxDepth > kLocalDepth) {
                IODelete(nextIndex, typeof(nextIndex[0]), maxDepth);
                IODelete(sets, typeof(sets[0]), maxDepth);
	}
}

void
OSMetaClass::applyToInstances(OSMetaClassInstanceApplierFunction applier,
    void * context) const
{
        IOLockLock(sInstancesLock);
        if (reserved->instances) {
                applyToInstances(reserved->instances, applier, context);
	}
        IOLockUnlock(sInstancesLock);
}

void
OSMetaClass::applyToInstancesOfClassName(
	const OSSymbol * name,
	OSMetaClassInstanceApplierFunction  applier,
	void * context)
{
        OSMetaClass  * meta;
        OSOrderedSet * set = NULL;

        IOLockLock(sAllClassesLock);
        if (sAllClassesDict
            && (meta = (OSMetaClass *) sAllClassesDict->getObject(name))
            && (set = meta->reserved->instances)) {
                set->retain();
	}
        IOLockUnlock(sAllClassesLock);

        if (!set) {
                return;
	}

        IOLockLock(sInstancesLock);
        applyToInstances(set, applier, context);
        IOLockUnlock(sInstancesLock);
        set->release();
}

/*********************************************************************
*********************************************************************/
void
OSMetaClass::considerUnloads()
{
        OSKext::considerUnloads();
}

/*********************************************************************
*********************************************************************/
bool
OSMetaClass::removeClasses(OSCollection * metaClasses)
{
        OSCollectionIterator * classIterator;
        OSMetaClass          * checkClass;
        bool                   result;

        classIterator = OSCollectionIterator::withCollection(metaClasses);
        if (!classIterator) {
                return false;
	}

        IOLockLock(sAllClassesLock);

        result = false;
        do{
                while ((checkClass = (OSMetaClass *)classIterator->getNextObject())
                    && !checkClass->getInstanceCount()
                    && !checkClass->reserved->retain) {
		}
                if (checkClass) {
                        break;
		}
                classIterator->reset();
                while ((checkClass = (OSMetaClass *)classIterator->getNextObject())) {
                        sAllClassesDict->removeObject(checkClass->className);
		}
                result = true;
	}while (false);

        IOLockUnlock(sAllClassesLock);
        OSSafeReleaseNULL(classIterator);

        return result;
}


/*********************************************************************
*********************************************************************/
const OSMetaClass *
OSMetaClass::getMetaClassWithName(const OSSymbol * name)
{
        OSMetaClass * retMeta = NULL;

        if (!name) {
                return NULL;
	}

        IOLockLock(sAllClassesLock);
        if (sAllClassesDict) {
                retMeta = (OSMetaClass *) sAllClassesDict->getObject(name);
	}
        IOLockUnlock(sAllClassesLock);

        return retMeta;
}

/*********************************************************************
*********************************************************************/
const OSMetaClass *
OSMetaClass::copyMetaClassWithName(const OSSymbol * name)
{
        const OSMetaClass * meta;

        if (!name) {
                return NULL;
	}

        meta = NULL;
        IOLockLock(sAllClassesLock);
        if (sAllClassesDict) {
                meta = (OSMetaClass *) sAllClassesDict->getObject(name);
                if (meta) {
                        OSIncrementAtomic(&meta->reserved->retain);
		}
	}
        IOLockUnlock(sAllClassesLock);

        return meta;
}

/*********************************************************************
*********************************************************************/
void
OSMetaClass::releaseMetaClass() const
{
        OSDecrementAtomic(&reserved->retain);
}

/*********************************************************************
*********************************************************************/
OSObject *
OSMetaClass::allocClassWithName(const OSSymbol * name)
{
        const OSMetaClass * meta;
        OSObject          * result;

        result = NULL;
        meta = copyMetaClassWithName(name);
        if (meta) {
                result = meta->alloc();
                meta->releaseMetaClass();
	}

        return result;
}

/*********************************************************************
*********************************************************************/
OSObject *
OSMetaClass::allocClassWithName(const OSString * name)
{
        const OSSymbol * tmpKey = OSSymbol::withString(name);
        OSObject * result = allocClassWithName(tmpKey);
        tmpKey->release();
        return result;
}

/*********************************************************************
*********************************************************************/
OSObject *
OSMetaClass::allocClassWithName(const char * name)
{
        const OSSymbol * tmpKey = OSSymbol::withCStringNoCopy(name);
        OSObject       * result = allocClassWithName(tmpKey);
        tmpKey->release();
        return result;
}


/*********************************************************************
*********************************************************************/
OSMetaClassBase *
OSMetaClass::checkMetaCastWithName(
	const OSSymbol        * name,
	const OSMetaClassBase * in)
{
        OSMetaClassBase * result = NULL;

        const OSMetaClass * const meta = getMetaClassWithName(name);

        if (meta) {
                result = meta->checkMetaCast(in);
	}

        return result;
}

/*********************************************************************
*********************************************************************/
OSMetaClassBase *
OSMetaClass::
checkMetaCastWithName(
	const OSString        * name,
	const OSMetaClassBase * in)
{
        const OSSymbol  * tmpKey = OSSymbol::withString(name);
        OSMetaClassBase * result = checkMetaCastWithName(tmpKey, in);

        tmpKey->release();
        return result;
}

/*********************************************************************
*********************************************************************/
OSMetaClassBase *
OSMetaClass::checkMetaCastWithName(
	const char            * name,
	const OSMetaClassBase * in)
{
        const OSSymbol  * tmpKey = OSSymbol::withCStringNoCopy(name);
        OSMetaClassBase * result = checkMetaCastWithName(tmpKey, in);

        tmpKey->release();
        return result;
}

/*********************************************************************
* OSMetaClass::checkMetaCast()
* Check to see if the 'check' object has this object in its metaclass chain.
* Returns check if it is indeed a kind of the current meta class, 0 otherwise.
*
* Generally this method is not invoked directly but is used to implement
* the OSMetaClassBase::metaCast member function.
*
* See also OSMetaClassBase::metaCast
*********************************************************************/
OSMetaClassBase *
OSMetaClass::checkMetaCast(
	const OSMetaClassBase * check) const
{
        const OSMetaClass * const toMeta   = this;
        const OSMetaClass *       fromMeta;

        for (fromMeta = check->getMetaClass();; fromMeta = fromMeta->superClassLink) {
                if (toMeta == fromMeta) {
                        return const_cast<OSMetaClassBase *>(check); // Discard const
		}
                if (!fromMeta->superClassLink) {
                        break;
		}
	}

        return NULL;
}

/*********************************************************************
*********************************************************************/
__dead2
void
OSMetaClass::reservedCalled(int ind) const
{
        const char * cname = className->getCStringNoCopy();
        panic("%s::_RESERVED%s%d called.", cname, cname, ind);
}

/*********************************************************************
*********************************************************************/
const
OSMetaClass *
OSMetaClass::getSuperClass() const
{
        return superClassLink;
}

/*********************************************************************
*********************************************************************/
const OSSymbol *
OSMetaClass::getKmodName() const
{
        OSKext * myKext = reserved ? reserved->kext : NULL;
        if (myKext) {
                return myKext->getIdentifier();
	}
        return OSSymbol::withCStringNoCopy("unknown");
}

/*********************************************************************
*********************************************************************/
OSKext *
OSMetaClass::getKext() const
{
        return reserved ? reserved->kext : NULL;
}

/*********************************************************************
*********************************************************************/
unsigned int
OSMetaClass::getInstanceCount() const
{
        return instanceCount;
}

/*********************************************************************
*********************************************************************/
/* static */
void
OSMetaClass::printInstanceCounts()
{
        OSCollectionIterator * classes;
        OSSymbol             * className;
        OSMetaClass          * meta;

        IOLockLock(sAllClassesLock);
        classes = OSCollectionIterator::withCollection(sAllClassesDict);
        assert(classes);

        while ((className = (OSSymbol *)classes->getNextObject())) {
                meta = (OSMetaClass *)sAllClassesDict->getObject(className);
                assert(meta);

                printf("%24s count: %03d x 0x%03x = 0x%06x\n",
                    className->getCStringNoCopy(),
                    meta->getInstanceCount(),
                    meta->getClassSize(),
                    meta->getInstanceCount() * meta->getClassSize());
	}
        printf("\n");
        classes->release();
        IOLockUnlock(sAllClassesLock);
        return;
}

/*********************************************************************
*********************************************************************/
OSDictionary *
OSMetaClass::getClassDictionary()
{
        panic("OSMetaClass::getClassDictionary() is obsoleted.\n");
        return NULL;
}

/*********************************************************************
*********************************************************************/
bool
OSMetaClass::serialize(__unused OSSerialize * s) const
{
        panic("OSMetaClass::serialize(): Obsoleted\n");
        return false;
}

/*********************************************************************
*********************************************************************/
/* static */
void
OSMetaClass::serializeClassDictionary(OSDictionary * serializeDictionary)
{
        OSDictionary * classDict = NULL;

        IOLockLock(sAllClassesLock);

        classDict = OSDictionary::withCapacity(sAllClassesDict->getCount());
        if (!classDict) {
                goto finish;
	}

        do {
                OSCollectionIterator * classes;
                const OSSymbol * className;

                classes = OSCollectionIterator::withCollection(sAllClassesDict);
                if (!classes) {
                        break;
		}

                while ((className = (const OSSymbol *)classes->getNextObject())) {
                        const OSMetaClass * meta;
                        OSNumber * count;

                        meta = (OSMetaClass *)sAllClassesDict->getObject(className);
                        count = OSNumber::withNumber(meta->getInstanceCount(), 32);
                        if (count) {
                                classDict->setObject(className, count);
                                count->release();
			}
		}
                classes->release();

                serializeDictionary->setObject("Classes", classDict);
	} while (0);

finish:
        OSSafeReleaseNULL(classDict);

        IOLockUnlock(sAllClassesLock);

        return;
}


/*********************************************************************
*********************************************************************/

#if IOTRACKING

void *
OSMetaClass::trackedNew(size_t size)
{
        IOTracking * mem;

        mem = (typeof(mem))kalloc_tag_bt(size + sizeof(IOTracking), VM_KERN_MEMORY_LIBKERN);
        assert(mem);
        if (!mem) {
                return mem;
	}

        memset(mem, 0, size + sizeof(IOTracking));
        mem++;

        OSIVAR_ACCUMSIZE(size);

        return mem;
}

void
OSMetaClass::trackedDelete(void * instance, size_t size)
{
        IOTracking * mem = (typeof(mem))instance; mem--;

        kfree(mem, size + sizeof(IOTracking));
        OSIVAR_ACCUMSIZE(-size);
}

void
OSMetaClass::trackedInstance(OSObject * instance) const
{
        IOTracking * mem = (typeof(mem))instance; mem--;

        return IOTrackingAdd(reserved->tracking, mem, classSize, false, VM_KERN_MEMORY_NONE);
}

void
OSMetaClass::trackedFree(OSObject * instance) const
{
        IOTracking * mem = (typeof(mem))instance; mem--;

        return IOTrackingRemove(reserved->tracking, mem, classSize);
}

void
OSMetaClass::trackedAccumSize(OSObject * instance, size_t size) const
{
        IOTracking * mem = (typeof(mem))instance; mem--;

        return IOTrackingAccumSize(reserved->tracking, mem, size);
}

IOTrackingQueue *
OSMetaClass::getTracking() const
{
        return reserved->tracking;
}

#endif /* IOTRACKING */