This is xnu-8019. See this file in:
/*
 * Copyright (c) 2008, 2013 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@
 */
#include <string.h>
#include <mach/vm_param.h>
#include <mach/vm_types.h>
#include <mach/kmod.h>
#include <mach-o/loader.h>
#include <mach-o/nlist.h>
#include <mach-o/reloc.h>
#include <sys/types.h>

#if KERNEL
    #include <libkern/kernel_mach_header.h>
    #include <libkern/OSKextLib.h>
    #include <libkern/OSKextLibPrivate.h>
    #include <mach/vm_param.h>
    #include <mach-o/fat.h>
#else /* !KERNEL */
    #include <architecture/byte_order.h>
    #include <mach/mach_init.h>
    #include <mach-o/arch.h>
    #include <mach-o/swap.h>

#endif /* KERNEL */

#define DEBUG_ASSERT_COMPONENT_NAME_STRING "kxld"
#include <AssertMacros.h>

#include "kxld_demangle.h"
#include "kxld_dict.h"
#include "kxld_kext.h"
#include "kxld_object.h"
#include "kxld_reloc.h"
#include "kxld_sect.h"
#include "kxld_seg.h"
#include "kxld_symtab.h"
#include "kxld_util.h"
#include "kxld_vtable.h"

extern boolean_t isSplitKext;

struct symtab_command;

struct kxld_kext {
	KXLDObject *kext;
	KXLDObject *interface;
	KXLDArray vtables;
	KXLDDict vtable_index;
	boolean_t vtables_created;
	boolean_t vtable_index_created;
};

/*******************************************************************************
* Prototypes
*******************************************************************************/

static kern_return_t export_symbols_through_interface(
	const KXLDObject *kext, const KXLDObject *interface,
	KXLDDict *defined_symbols_by_name,
	KXLDDict *defined_cxx_symbol_by_value,
	KXLDDict *obsolete_symbols_by_name);
static kern_return_t export_symbols(const KXLDObject *kext,
    KXLDDict *defined_symbols_by_name,
    KXLDDict *defined_cxx_symbols_by_value);

static kern_return_t create_vtables(KXLDKext *kext,
    const KXLDDict *defined_symbols, const KXLDDict *defined_cxx_symbols);
static kern_return_t get_vtable_syms_from_smcp(KXLDKext *kext,
    const KXLDDict *defined_symbols, KXLDSym *super_metaclass_ptr_sym,
    KXLDSym **vtable_sym_out, KXLDSym **meta_vtable_sym_out);

static kern_return_t resolve_symbols(KXLDKext *kext,
    const KXLDDict *defined_symbols, const KXLDDict *obsolete_symbols);

static kern_return_t patch_vtables(KXLDKext *kext, KXLDDict *patched_vtables,
    const KXLDDict *defined_symbols);
static kern_return_t create_vtable_index(KXLDKext *kext);
static const KXLDSym *get_metaclass_symbol_from_super_meta_class_pointer_symbol(
	KXLDKext *kext, KXLDSym *super_metaclass_pointer_sym);

static kern_return_t validate_symbols(KXLDKext *kext);

/*******************************************************************************
*******************************************************************************/
size_t
kxld_kext_sizeof(void)
{
	return sizeof(KXLDKext);
}

/*******************************************************************************
*******************************************************************************/
kern_return_t
kxld_kext_init(KXLDKext *kext, KXLDObject *kext_object,
    KXLDObject *interface_object)
{
	kern_return_t rval = KERN_FAILURE;

	check(kext);
	check(kext_object);

	kext->kext = kext_object;

	if (interface_object) {
		kext->interface = interface_object;

		rval = kxld_object_index_symbols_by_name(kext->kext);
		require_noerr(rval, finish);
	}

	rval = KERN_SUCCESS;
finish:
	return rval;
}

/*******************************************************************************
*******************************************************************************/
void
kxld_kext_clear(KXLDKext *kext)
{
	KXLDVTable *vtable = NULL;
	u_int i;

	check(kext);

	for (i = 0; i < kext->vtables.nitems; ++i) {
		vtable = kxld_array_get_item(&kext->vtables, i);
		kxld_vtable_clear(vtable);
	}
	kxld_array_reset(&kext->vtables);
	kxld_dict_clear(&kext->vtable_index);

	kext->kext = NULL;
	kext->interface = NULL;
	kext->vtables_created = FALSE;
	kext->vtable_index_created = FALSE;
}


/*******************************************************************************
*******************************************************************************/
void
kxld_kext_deinit(KXLDKext *kext)
{
	KXLDVTable *vtable = NULL;
	u_int i;

	check(kext);

	for (i = 0; i < kext->vtables.maxitems; ++i) {
		vtable = kxld_array_get_slot(&kext->vtables, i);
		kxld_vtable_deinit(vtable);
	}
	kxld_array_deinit(&kext->vtables);
	kxld_dict_deinit(&kext->vtable_index);

	bzero(kext, sizeof(*kext));
}

/*******************************************************************************
*******************************************************************************/
kern_return_t
kxld_kext_export_symbols(const KXLDKext *kext,
    KXLDDict *defined_symbols_by_name,
    KXLDDict *obsolete_symbols_by_name,
    KXLDDict *defined_cxx_symbols_by_value)
{
	kern_return_t rval = KERN_FAILURE;

	check(kext);

	if (kext->interface) {
		rval = export_symbols_through_interface(kext->kext, kext->interface,
		    defined_symbols_by_name, obsolete_symbols_by_name,
		    defined_cxx_symbols_by_value);
		require_noerr(rval, finish);
	} else {
		rval = export_symbols(kext->kext, defined_symbols_by_name,
		    defined_cxx_symbols_by_value);
		require_noerr(rval, finish);
	}

	rval = KERN_SUCCESS;
finish:
	return rval;
}

/*******************************************************************************
*******************************************************************************/
kern_return_t
export_symbols_through_interface(const KXLDObject *kext,
    const KXLDObject *interface, KXLDDict *defined_symbols_by_name,
    KXLDDict *obsolete_symbols_by_name, KXLDDict *defined_cxx_symbols_by_value)
{
	kern_return_t rval = KERN_FAILURE;
	KXLDSymtabIterator iter;
	const KXLDSymtab *kext_symtab = NULL;
	const KXLDSymtab *interface_symtab = NULL;
	KXLDSym *kext_sym = NULL;
	const KXLDSym *interface_sym = NULL;

	check(kext);
	check(interface);

	kext_symtab = kxld_object_get_symtab(kext);
	interface_symtab = kxld_object_get_symtab(interface);

	if (defined_symbols_by_name) {
		/* Add exported symbols */
		(void) kxld_symtab_iterator_init(&iter, interface_symtab,
		    kxld_sym_is_undefined, FALSE);
		while ((interface_sym = kxld_symtab_iterator_get_next(&iter))) {
			kext_sym = kxld_symtab_get_locally_defined_symbol_by_name(kext_symtab,
			    interface_sym->name);
			if (!kext_sym) {
				kxld_log(kKxldLogLinking, kKxldLogWarn,
				    "In interface %s of %s, couldn't find symbol %s\n",
				    kxld_object_get_name(interface), kxld_object_get_name(kext),
				    interface_sym->name);
				continue;
			}

			rval = kxld_dict_insert(defined_symbols_by_name,
			    kext_sym->name, kext_sym);
			require_noerr(rval, finish);
		}

		/* Add indirect symbols */
		(void) kxld_symtab_iterator_init(&iter, interface_symtab,
		    kxld_sym_is_indirect, FALSE);
		while ((interface_sym = kxld_symtab_iterator_get_next(&iter))) {
			kext_sym = kxld_symtab_get_locally_defined_symbol_by_name(kext_symtab,
			    interface_sym->alias);
			if (!kext_sym) {
				kxld_log(kKxldLogLinking, kKxldLogWarn,
				    "In interface %s of %s, couldn't find indirect symbol %s (%s)\n",
				    kxld_object_get_name(interface), kxld_object_get_name(kext),
				    interface_sym->alias, interface_sym->name);
				continue;
			}

			rval = kxld_dict_insert(defined_symbols_by_name,
			    interface_sym->name, kext_sym);
			require_noerr(rval, finish);
		}
	}

	/* Add obsolete symbols */
	if (obsolete_symbols_by_name) {
		(void) kxld_symtab_iterator_init(&iter, interface_symtab,
		    kxld_sym_is_obsolete, FALSE);
		while ((kext_sym = kxld_symtab_iterator_get_next(&iter))) {
			rval = kxld_dict_insert(obsolete_symbols_by_name,
			    kext_sym->name, kext_sym);
			require_noerr(rval, finish);
		}
	}

	/* Add C++ symbols */
	if (defined_cxx_symbols_by_value) {
		(void) kxld_symtab_iterator_init(&iter, kext_symtab,
		    kxld_sym_is_cxx, FALSE);
		while ((kext_sym = kxld_symtab_iterator_get_next(&iter))) {
			rval = kxld_dict_insert(defined_cxx_symbols_by_value,
			    &kext_sym->link_addr, kext_sym);
			require_noerr(rval, finish);
		}
	}

	rval = KERN_SUCCESS;
finish:
	return rval;
}

/*******************************************************************************
*******************************************************************************/
kern_return_t
export_symbols(const KXLDObject *kext, KXLDDict *defined_symbols_by_name,
    KXLDDict *defined_cxx_symbols_by_value)
{
	kern_return_t rval = KERN_FAILURE;
	KXLDSymtabIterator iter;
	KXLDSym *sym = NULL;

	(void) kxld_symtab_iterator_init(&iter, kxld_object_get_symtab(kext),
	    kxld_sym_is_exported, FALSE);
	while ((sym = kxld_symtab_iterator_get_next(&iter))) {
		if (defined_symbols_by_name) {
			rval = kxld_dict_insert(defined_symbols_by_name, sym->name, sym);
			require_noerr(rval, finish);
		}

		if (kxld_sym_is_cxx(sym) && defined_cxx_symbols_by_value) {
			rval = kxld_dict_insert(defined_cxx_symbols_by_value,
			    &sym->link_addr, sym);
			require_noerr(rval, finish);
		}
	}

	rval = KERN_SUCCESS;
finish:
	return rval;
}

/*******************************************************************************
*******************************************************************************/
kern_return_t
kxld_kext_export_vtables(KXLDKext *kext, const KXLDDict *defined_cxx_symbols,
    const KXLDDict *defined_symbols, KXLDDict *vtables)
{
	kern_return_t rval = KERN_FAILURE;
	KXLDVTable *vtable = NULL;
	u_int i = 0;

	check(kext);
	check(defined_symbols);
	check(defined_cxx_symbols);
	check(vtables);

	rval = create_vtables(kext, defined_cxx_symbols, defined_symbols);
	require_noerr(rval, finish);

	for (i = 0; i < kext->vtables.nitems; ++i) {
		vtable = kxld_array_get_item(&kext->vtables, i);

		rval = kxld_dict_insert(vtables, vtable->name, vtable);
		require_noerr(rval, finish);
	}

	rval = KERN_SUCCESS;
finish:
	return rval;
}

/*******************************************************************************
*******************************************************************************/
void
kxld_kext_get_vmsize_for_seg_by_name(const KXLDKext *kext,
    const char *segname,
    u_long *vmsize)
{
	(void) kxld_object_get_vmsize_for_seg_by_name(kext->kext, segname, vmsize);
}

/*******************************************************************************
*******************************************************************************/
void
kxld_kext_get_vmsize(const KXLDKext *kext,
    u_long *header_size, u_long *vmsize)
{
	(void) kxld_object_get_vmsize(kext->kext, header_size, vmsize);
}

/*******************************************************************************
*******************************************************************************/
void
kxld_kext_set_linked_object_size(KXLDKext *kext, u_long vmsize)
{
	(void) kxld_object_set_linked_object_size(kext->kext, vmsize);
}

/*******************************************************************************
*******************************************************************************/
kern_return_t
kxld_kext_export_linked_object(const KXLDKext *kext,
    void *linked_object,
    kxld_addr_t *kmod_info)
{
	kern_return_t rval = KERN_FAILURE;
	const KXLDSym *kmodsym = NULL;

	kmodsym = kxld_symtab_get_locally_defined_symbol_by_name(
		kxld_object_get_symtab(kext->kext), KXLD_KMOD_INFO_SYMBOL);

	require_action(kmodsym, finish, rval = KERN_FAILURE;
	    kxld_log(kKxldLogLinking, kKxldLogErr, kKxldLogNoKmodInfo));

	*kmod_info = kmodsym->link_addr;

	rval = kxld_object_export_linked_object(kext->kext, linked_object);
finish:
	return rval;
}

/*******************************************************************************
*******************************************************************************/
kern_return_t
kxld_kext_relocate(KXLDKext *kext,
    kxld_addr_t link_address,
    KXLDDict *patched_vtables,
    const KXLDDict *defined_symbols,
    const KXLDDict *obsolete_symbols,
    const KXLDDict *defined_cxx_symbols)
{
	kern_return_t rval = KERN_FAILURE;

	check(kext);
	check(patched_vtables);
	check(defined_symbols);
	check(obsolete_symbols);

	/* Kexts that are being relocated need symbols indexed by value for vtable
	 * creation and patching. Note that we don't need to index by value for
	 * dependencies that have already been linked because their symbols are
	 * already in the global cxx value table. It's important to index the
	 * symbols by value before we relocate the symbols because the vtable
	 * entries will still have unrelocated values.
	 */
	rval = kxld_object_index_cxx_symbols_by_value(kext->kext);
	require_noerr(rval, finish);

	rval = kxld_object_index_symbols_by_name(kext->kext);
	require_noerr(rval, finish);

	rval = kxld_object_relocate(kext->kext, link_address);
	require_noerr(rval, finish);

	rval = resolve_symbols(kext, defined_symbols, obsolete_symbols);
	require_noerr(rval, finish);

	rval = create_vtables(kext, defined_cxx_symbols, /* defined_symbols */ NULL);
	require_noerr(rval, finish);

	if (isSplitKext == FALSE) {
		rval = patch_vtables(kext, patched_vtables, defined_symbols);
		require_noerr(rval, finish);
	}

	rval = validate_symbols(kext);
	require_noerr(rval, finish);

	rval = kxld_object_process_relocations(kext->kext, patched_vtables);
	require_noerr(rval, finish);

	rval = KERN_SUCCESS;
finish:
	return rval;
}

/*******************************************************************************
* The defined symbols argument is optional.  When supplied, create_vtables()
* will look for vtable symbols in the defined_symbols dictionary.  Otherwise,
* it will look in the kext's symbol table for vtable symbols.
*
* We do this because there are two types of KXLDKext objects that call
* create_vtables(), those that have been linked, and those that haven't.  The
* linked kexts export their symbols into the global symbol table that is used
* for symbol resolution, so we can look there for vtable symbols without
* having to index their local symbol table separately.
*
* Unlinked kexts haven't yet had their symbols exported into the global table,
* so we have to index their local symbol table separately.
*******************************************************************************/
static kern_return_t
create_vtables(KXLDKext *kext, const KXLDDict *defined_cxx_symbols,
    const KXLDDict *defined_symbols)
{
	kern_return_t rval = KERN_FAILURE;
	const KXLDSymtab *symtab = NULL;
	KXLDSymtabIterator iter;
	KXLDSym *sym = NULL;
	KXLDSym *vtable_sym = NULL;
	KXLDSym *meta_vtable_sym = NULL;
	KXLDVTable *vtable = NULL;
	KXLDVTable *meta_vtable = NULL;
	u_int i = 0;
	u_int nvtables = 0;

	if (kext->vtables_created) {
		rval = KERN_SUCCESS;
		goto finish;
	}

	symtab = kxld_object_get_symtab(kext->kext);

	if (kxld_object_is_linked(kext->kext)) {
		/* Create a vtable object for every vtable symbol */
		kxld_symtab_iterator_init(&iter, symtab, kxld_sym_is_vtable, FALSE);
		nvtables = kxld_symtab_iterator_get_num_remaining(&iter);
	} else {
		/* We walk over the super metaclass pointer symbols because classes
		 * with them are the only ones that need patching.  Then we double the
		 * number of vtables we're expecting, because every pointer will have a
		 * class vtable and a MetaClass vtable.
		 */
		kxld_symtab_iterator_init(&iter, symtab,
		    kxld_sym_is_super_metaclass_pointer, FALSE);
		nvtables = kxld_symtab_iterator_get_num_remaining(&iter) * 2;
	}

	rval = kxld_array_init(&kext->vtables, sizeof(KXLDVTable), nvtables);
	require_noerr(rval, finish);

	while ((sym = kxld_symtab_iterator_get_next(&iter))) {
		if (kxld_object_is_linked(kext->kext)) {
			vtable_sym = sym;
			meta_vtable_sym = NULL;
			meta_vtable = NULL;
		} else {
			rval = get_vtable_syms_from_smcp(kext, defined_symbols, sym,
			    &vtable_sym, &meta_vtable_sym);
			require_noerr(rval, finish);
		}

		vtable = kxld_array_get_item(&kext->vtables, i++);
		rval = kxld_vtable_init(vtable, vtable_sym, kext->kext,
		    defined_cxx_symbols);
		require_noerr(rval, finish);

		/* meta_vtable_sym will be null when we don't support strict
		 * patching and can't find the metaclass vtable. If that's the
		 * case, we just reduce the expect number of vtables by 1.
		 */
		if (!kxld_object_is_linked(kext->kext)) {
			if (meta_vtable_sym) {
				meta_vtable = kxld_array_get_item(&kext->vtables, i++);
				rval = kxld_vtable_init(meta_vtable, meta_vtable_sym,
				    kext->kext, defined_cxx_symbols);
				require_noerr(rval, finish);
			} else {
				kxld_array_resize(&kext->vtables, --nvtables);
				meta_vtable = NULL;
			}
		}
	}
	require_action(i == kext->vtables.nitems, finish,
	    rval = KERN_FAILURE);

	kext->vtables_created = TRUE;
	rval = KERN_SUCCESS;
finish:
	return rval;
}

/*******************************************************************************
*******************************************************************************/
static kern_return_t
get_vtable_syms_from_smcp(KXLDKext *kext, const KXLDDict *defined_symbols,
    KXLDSym *super_metaclass_ptr_sym, KXLDSym **vtable_sym_out,
    KXLDSym **meta_vtable_sym_out)
{
	kern_return_t rval = KERN_FAILURE;
	const KXLDSymtab *symtab = NULL;
	KXLDSym *vtable_sym = NULL;
	KXLDSym *meta_vtable_sym = NULL;
	char class_name[KXLD_MAX_NAME_LEN];
	char vtable_name[KXLD_MAX_NAME_LEN];
	char meta_vtable_name[KXLD_MAX_NAME_LEN];
	char *demangled_name1 = NULL;
	char *demangled_name2 = NULL;
	size_t demangled_length1 = 0;
	size_t demangled_length2 = 0;

	check(kext);
	check(vtable_sym_out);
	check(meta_vtable_sym_out);

	require(!kxld_object_is_kernel(kext->kext), finish);

	symtab = kxld_object_get_symtab(kext->kext);

	/* Get the class name from the smc pointer */
	rval = kxld_sym_get_class_name_from_super_metaclass_pointer(
		super_metaclass_ptr_sym, class_name, sizeof(class_name));
	require_noerr(rval, finish);

	/* Get the vtable name from the class name */
	rval = kxld_sym_get_vtable_name_from_class_name(class_name,
	    vtable_name, sizeof(vtable_name));
	require_noerr(rval, finish);

	/* Get the vtable symbol */
	if (defined_symbols) {
		vtable_sym = kxld_dict_find(defined_symbols, vtable_name);
	} else {
		vtable_sym = kxld_symtab_get_locally_defined_symbol_by_name(symtab,
		    vtable_name);
	}
	require_action(vtable_sym, finish, rval = KERN_FAILURE;
	    kxld_log(kKxldLogPatching, kKxldLogErr, kKxldLogMissingVtable,
	    vtable_name, class_name));

	/* Get the meta vtable name from the class name */
	rval = kxld_sym_get_meta_vtable_name_from_class_name(class_name,
	    meta_vtable_name, sizeof(meta_vtable_name));
	require_noerr(rval, finish);

	/* Get the meta vtable symbol */
	if (defined_symbols) {
		meta_vtable_sym = kxld_dict_find(defined_symbols, meta_vtable_name);
	} else {
		meta_vtable_sym = kxld_symtab_get_locally_defined_symbol_by_name(symtab,
		    meta_vtable_name);
	}
	if (!meta_vtable_sym) {
		if (kxld_object_target_supports_strict_patching(kext->kext)) {
			kxld_log(kKxldLogPatching, kKxldLogErr,
			    kKxldLogMissingVtable,
			    meta_vtable_name, class_name);
			rval = KERN_FAILURE;
			goto finish;
		} else {
			kxld_log(kKxldLogPatching, kKxldLogErr,
			    "Warning: " kKxldLogMissingVtable,
			    kxld_demangle(meta_vtable_name, &demangled_name1,
			    &demangled_length1),
			    kxld_demangle(class_name, &demangled_name2,
			    &demangled_length2));
		}
	}

	*vtable_sym_out = vtable_sym;
	*meta_vtable_sym_out = meta_vtable_sym;
	rval = KERN_SUCCESS;
finish:
	if (demangled_name1) {
		kxld_free(demangled_name1, demangled_length1);
	}
	if (demangled_name2) {
		kxld_free(demangled_name2, demangled_length2);
	}

	return rval;
}

/*******************************************************************************
*******************************************************************************/
static kern_return_t
resolve_symbols(KXLDKext *kext, const KXLDDict *defined_symbols,
    const KXLDDict *obsolete_symbols)
{
	kern_return_t rval = KERN_FAILURE;
	const KXLDSymtab *symtab = NULL;
	KXLDSymtabIterator iter;
	KXLDSym *sym = NULL;
	KXLDSym *defined_sym = NULL;
	const char *name = NULL;
	boolean_t tests_for_weak = FALSE;
	boolean_t error = FALSE;
	char *demangled_name = NULL;
	size_t demangled_length = 0;

	check(kext->kext);
	check(defined_symbols);
	check(obsolete_symbols);

	symtab = kxld_object_get_symtab(kext->kext);

	/* Check if the kext tests for weak symbols */
	sym = kxld_symtab_get_symbol_by_name(symtab, KXLD_WEAK_TEST_SYMBOL);
	tests_for_weak = (sym != NULL);

	/* Check for duplicate symbols */
	kxld_symtab_iterator_init(&iter, symtab, kxld_sym_is_exported, FALSE);
	while ((sym = kxld_symtab_iterator_get_next(&iter))) {
		defined_sym = kxld_dict_find(defined_symbols, sym->name);
		if (defined_sym) {
			/* Not a problem if the symbols have the same address */
			if (defined_sym->link_addr == sym->link_addr) {
				continue;
			}

			if (!error) {
				error = TRUE;
				kxld_log(kKxldLogLinking, kKxldLogErr,
				    "The following symbols were defined more than once:");
			}

			kxld_log(kKxldLogLinking, kKxldLogErr, "\t%s: %p - %p",
			    kxld_demangle(sym->name, &demangled_name, &demangled_length),
			    (void *) (uintptr_t) sym->link_addr,
			    (void *) (uintptr_t) defined_sym->link_addr);
		}
	}
	require_noerr_action(error, finish, rval = KERN_FAILURE);

	/* Resolve undefined and indirect symbols */

	/* Iterate over all unresolved symbols */
	kxld_symtab_iterator_init(&iter, symtab,
	    kxld_sym_is_unresolved, FALSE);
	while ((sym = kxld_symtab_iterator_get_next(&iter))) {
		/* Common symbols are not supported */
		if (kxld_sym_is_common(sym)) {
			if (!error) {
				error = TRUE;
				if (kxld_object_target_supports_common_symbols(kext->kext)) {
					kxld_log(kKxldLogLinking, kKxldLogErr,
					    "The following common symbols were not resolved:");
				} else {
					kxld_log(kKxldLogLinking, kKxldLogErr,
					    "Common symbols are not supported in kernel extensions. "
					    "Use -fno-common to build your kext. "
					    "The following are common symbols:");
				}
			}
			kxld_log(kKxldLogLinking, kKxldLogErr, "\t%s",
			    kxld_demangle(sym->name, &demangled_name, &demangled_length));
		} else {
			/* Find the address of the defined symbol */
			if (kxld_sym_is_undefined(sym)) {
				name = sym->name;
			} else {
				name = sym->alias;
			}
			defined_sym = kxld_dict_find(defined_symbols, name);

			/* Resolve the symbol.  If a definition cannot be found, then:
			 * 1) Psuedokexts log a warning and proceed
			 * 2) Actual kexts delay the error until validation in case vtable
			 *    patching replaces the undefined symbol.
			 */

			if (defined_sym) {
				rval = kxld_sym_resolve(sym, defined_sym->link_addr);
				require_noerr(rval, finish);

				if (obsolete_symbols && kxld_dict_find(obsolete_symbols, name)) {
					kxld_log(kKxldLogLinking, kKxldLogWarn,
					    "This kext uses obsolete symbol %s.",
					    kxld_demangle(name, &demangled_name, &demangled_length));
				}
			} else if (kxld_sym_is_weak(sym)) {
				kxld_addr_t addr = 0;

				/* Make sure that the kext has referenced gOSKextUnresolved.
				 */
				require_action(tests_for_weak, finish,
				    rval = KERN_FAILURE;
				    kxld_log(kKxldLogLinking, kKxldLogErr,
				    "This kext has weak references but does not test for "
				    "them. Test for weak references with "
				    "OSKextSymbolIsResolved(). (found in <libkern/OSKextLib.h>)"));

#if KERNEL
				/* Get the address of the default weak address.
				 */
				addr = (kxld_addr_t) &kext_weak_symbol_referenced;
#else
				/* This is run during symbol generation only, so we only
				 * need a filler value here.
				 */
				addr = 0xF00DD00D;
#endif /* KERNEL */

				rval = kxld_sym_resolve(sym, addr);
				require_noerr(rval, finish);
			}
		}
	}
	require_noerr_action(error, finish, rval = KERN_FAILURE);

	rval = KERN_SUCCESS;

finish:
	if (demangled_name) {
		kxld_free(demangled_name, demangled_length);
	}

	return rval;
}

/*******************************************************************************
* We must patch vtables to ensure binary compatibility, and to perform that
* patching, we have to determine the vtables' inheritance relationships.  The
* MetaClass system gives us a way to do that:
*   1) Iterate over all of the super MetaClass pointer symbols.  Every class
*      that inherits from OSObject will have a pointer in its MetaClass that
*      points to the MetaClass's super MetaClass.
*   2) Derive the name of the class from the super MetaClass pointer.
*   3) Derive the name of the class's vtable from the name of the class
*   4) Follow the super MetaClass pointer to get the address of the super
*      MetaClass's symbol
*   5) Look up the super MetaClass symbol by address
*   6) Derive the super class's name from the super MetaClass name
*   7) Derive the super class's vtable from the super class's name
* This procedure will allow us to find all of the OSObject-derived classes and
* their super classes, and thus patch all of the vtables.
*
* We also have to take care to patch up the MetaClass's vtables.  The
* MetaClasses follow a parallel hierarchy to the classes, so once we have the
* class name and super class name, we can also derive the MetaClass name and
* the super MetaClass name, and thus find and patch their vtables as well.
*******************************************************************************/

#define kOSMetaClassVTableName "__ZTV11OSMetaClass"

static kern_return_t
patch_vtables(KXLDKext *kext, KXLDDict *patched_vtables,
    const KXLDDict *defined_symbols)
{
	kern_return_t rval = KERN_FAILURE;
	KXLDSymtabIterator iter;
	const KXLDSymtab *symtab = NULL;
	const KXLDSym *metaclass = NULL;
	KXLDSym *super_metaclass_pointer = NULL;
	KXLDSym *final_sym = NULL;
	KXLDVTable *vtable = NULL;
	KXLDVTable *super_vtable = NULL;
	char class_name[KXLD_MAX_NAME_LEN];
	char super_class_name[KXLD_MAX_NAME_LEN];
	char vtable_name[KXLD_MAX_NAME_LEN];
	char super_vtable_name[KXLD_MAX_NAME_LEN];
	char final_sym_name[KXLD_MAX_NAME_LEN];
	char *demangled_name1 = NULL;
	char *demangled_name2 = NULL;
	size_t demangled_length1 = 0;
	size_t demangled_length2 = 0;
	size_t len = 0;
	u_int nvtables = 0;
	u_int npatched = 0;
	u_int nprogress = 0;
	boolean_t failure = FALSE;

	check(kext);
	check(patched_vtables);

	symtab = kxld_object_get_symtab(kext->kext);

	rval = create_vtable_index(kext);
	require_noerr(rval, finish);

	/* Find each super meta class pointer symbol */

	kxld_symtab_iterator_init(&iter, symtab,
	    kxld_sym_is_super_metaclass_pointer, FALSE);
	nvtables = kxld_symtab_iterator_get_num_remaining(&iter);

	while (npatched < nvtables) {
		npatched = 0;
		nprogress = 0;
		kxld_symtab_iterator_reset(&iter);
		while ((super_metaclass_pointer = kxld_symtab_iterator_get_next(&iter))) {
			/* Get the class name from the smc pointer */
			rval = kxld_sym_get_class_name_from_super_metaclass_pointer(
				super_metaclass_pointer, class_name, sizeof(class_name));
			require_noerr(rval, finish);

			/* Get the vtable name from the class name */
			rval = kxld_sym_get_vtable_name_from_class_name(class_name,
			    vtable_name, sizeof(vtable_name));
			require_noerr(rval, finish);

			/* Get the vtable and make sure it hasn't been patched */
			vtable = kxld_dict_find(&kext->vtable_index, vtable_name);
			require_action(vtable, finish, rval = KERN_FAILURE;
			    kxld_log(kKxldLogPatching, kKxldLogErr, kKxldLogMissingVtable,
			    vtable_name, class_name));

			if (!vtable->is_patched) {
				/* Find the SMCP's meta class symbol */
				metaclass = get_metaclass_symbol_from_super_meta_class_pointer_symbol(
					kext, super_metaclass_pointer);
				require_action(metaclass, finish, rval = KERN_FAILURE);

				/* Get the super class name from the super metaclass */
				rval = kxld_sym_get_class_name_from_metaclass(metaclass,
				    super_class_name, sizeof(super_class_name));
				require_noerr(rval, finish);

				/* Get the super vtable name from the class name */
				rval = kxld_sym_get_vtable_name_from_class_name(super_class_name,
				    super_vtable_name, sizeof(super_vtable_name));
				require_noerr(rval, finish);

				/* Get the super vtable if it's been patched */
				super_vtable = kxld_dict_find(patched_vtables, super_vtable_name);

				if (failure) {
					const KXLDVTable *unpatched_super_vtable;
					unpatched_super_vtable = kxld_dict_find(&kext->vtable_index,
					    super_vtable_name);

					/* If the parent's vtable hasn't been patched, warn that
					 * this vtable is unpatchable because of the parent.
					 */
					if (!super_vtable) {
						kxld_log(kKxldLogPatching, kKxldLogErr,
						    "The %s was not patched because its parent, "
						    "the %s, was not %s.",
						    kxld_demangle(vtable_name, &demangled_name1,
						    &demangled_length1),
						    kxld_demangle(super_vtable_name, &demangled_name2,
						    &demangled_length2),
						    (unpatched_super_vtable) ? "patchable" : "found");
					}
					continue;
				}

				if (!super_vtable) {
					continue;
				}

				/* Get the final symbol's name from the super vtable */
				rval = kxld_sym_get_final_sym_name_from_class_name(super_class_name,
				    final_sym_name, sizeof(final_sym_name));
				require_noerr(rval, finish);

				/* Verify that the final symbol does not exist.  First check
				 * all the externally defined symbols, then check locally.
				 */
				final_sym = kxld_dict_find(defined_symbols, final_sym_name);
				if (!final_sym) {
					final_sym = kxld_symtab_get_locally_defined_symbol_by_name(
						symtab, final_sym_name);
				}
				if (final_sym) {
					kxld_log(kKxldLogPatching, kKxldLogErr,
					    "Class '%s' is a subclass of final class '%s'.",
					    kxld_demangle(class_name, &demangled_name1,
					    &demangled_length1),
					    kxld_demangle(super_class_name, &demangled_name2,
					    &demangled_length2));
					continue;
				}

				/* Patch the class's vtable */
				rval = kxld_vtable_patch(vtable, super_vtable, kext->kext);
				if (rval) {
					continue;
				}

				/* Add the class's vtable to the set of patched vtables */
				rval = kxld_dict_insert(patched_vtables, vtable->name, vtable);
				require_noerr(rval, finish);

				/* Get the meta vtable name from the class name */
				rval = kxld_sym_get_meta_vtable_name_from_class_name(class_name,
				    vtable_name, sizeof(vtable_name));
				require_noerr(rval, finish);

				/* Get the meta vtable.  Whether or not it should exist has already
				 * been tested in create_vtables(), so if it doesn't exist and we're
				 * still running, we can safely skip it.
				 */
				vtable = kxld_dict_find(&kext->vtable_index, vtable_name);
				if (!vtable) {
					++nprogress;
					++npatched;
					continue;
				}
				require_action(!vtable->is_patched, finish, rval = KERN_FAILURE);

				/* There is no way to look up a metaclass vtable at runtime, but
				 * we know that every class's metaclass inherits directly from
				 * OSMetaClass, so we just hardcode that vtable name here.
				 */
				len = strlcpy(super_vtable_name, kOSMetaClassVTableName,
				    sizeof(super_vtable_name));
				require_action(len == const_strlen(kOSMetaClassVTableName),
				    finish, rval = KERN_FAILURE);

				/* Get the super meta vtable */
				super_vtable = kxld_dict_find(patched_vtables, super_vtable_name);
				require_action(super_vtable && super_vtable->is_patched,
				    finish, rval = KERN_FAILURE);

				/* Patch the meta class's vtable */
				rval = kxld_vtable_patch(vtable, super_vtable, kext->kext);
				require_noerr(rval, finish);

				/* Add the MetaClass's vtable to the set of patched vtables */
				rval = kxld_dict_insert(patched_vtables, vtable->name, vtable);
				require_noerr(rval, finish);

				++nprogress;
			}

			++npatched;
		}

		require_action(!failure, finish, rval = KERN_FAILURE);
		failure = (nprogress == 0);
	}

	rval = KERN_SUCCESS;
finish:
	if (demangled_name1) {
		kxld_free(demangled_name1, demangled_length1);
	}
	if (demangled_name2) {
		kxld_free(demangled_name2, demangled_length2);
	}

	return rval;
}

/*******************************************************************************
*******************************************************************************/
static kern_return_t
create_vtable_index(KXLDKext *kext)
{
	kern_return_t rval = KERN_FAILURE;
	KXLDVTable *vtable = NULL;
	u_int i = 0;

	if (kext->vtable_index_created) {
		rval = KERN_SUCCESS;
		goto finish;
	}

	/* Map vtable names to the vtable structures */
	rval = kxld_dict_init(&kext->vtable_index, kxld_dict_string_hash,
	    kxld_dict_string_cmp, kext->vtables.nitems);
	require_noerr(rval, finish);

	for (i = 0; i < kext->vtables.nitems; ++i) {
		vtable = kxld_array_get_item(&kext->vtables, i);
		rval = kxld_dict_insert(&kext->vtable_index, vtable->name, vtable);
		require_noerr(rval, finish);
	}

	kext->vtable_index_created = TRUE;
	rval = KERN_SUCCESS;
finish:
	return rval;
}

/*******************************************************************************
*******************************************************************************/
static const KXLDSym *
get_metaclass_symbol_from_super_meta_class_pointer_symbol(KXLDKext *kext,
    KXLDSym *super_metaclass_pointer_sym)
{
	kern_return_t rval = KERN_FAILURE;
	const KXLDReloc *reloc = NULL;
	const KXLDSect *sect = NULL;
	const KXLDSym *metaclass = NULL;

	check(kext);
	check(super_metaclass_pointer_sym);

	/* Get the relocation entry that fills in the super metaclass pointer. */
	reloc = kxld_object_get_reloc_at_symbol(kext->kext,
	    super_metaclass_pointer_sym);
	require_action(reloc, finish, rval = KERN_FAILURE);

	/* Get the section of the super metaclass pointer. */
	sect = kxld_object_get_section_by_index(kext->kext,
	    super_metaclass_pointer_sym->sectnum);
	require_action(sect, finish, rval = KERN_FAILURE);

	/* Get the symbol that will be filled into the super metaclass pointer. */
	metaclass = kxld_object_get_symbol_of_reloc(kext->kext, reloc, sect);


finish:
	if (metaclass == NULL) {
		kxld_log(kKxldLogLinking, kKxldLogErr,
		    "metaclass == NULL kxld_sym %s <%s>",
		    super_metaclass_pointer_sym->name, __func__);
	}
	return metaclass;
}


/*******************************************************************************
*******************************************************************************/
static kern_return_t
validate_symbols(KXLDKext *kext)
{
	kern_return_t rval = KERN_FAILURE;
	KXLDSymtabIterator iter;
	KXLDSym *sym = NULL;
	u_int error = FALSE;
	char *demangled_name = NULL;
	size_t demangled_length = 0;

	/* Check for any unresolved symbols */
	kxld_symtab_iterator_init(&iter, kxld_object_get_symtab(kext->kext),
	    kxld_sym_is_unresolved, FALSE);
	while ((sym = kxld_symtab_iterator_get_next(&iter))) {
		if (!error) {
			error = TRUE;
			kxld_log(kKxldLogLinking, kKxldLogErr,
			    "The following symbols are unresolved for this kext:");
		}
		kxld_log(kKxldLogLinking, kKxldLogErr, "\t%s",
		    kxld_demangle(sym->name, &demangled_name, &demangled_length));
	}
	require_noerr_action(error, finish, rval = KERN_FAILURE);

	rval = KERN_SUCCESS;

finish:
	if (demangled_name) {
		kxld_free(demangled_name, demangled_length);
	}
	return rval;
}