This is xnu-8019. See this file in:
/*
 * Copyright (c) 2007-2008, 2012 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 <sys/types.h>
#include <mach/vm_param.h>  /* For PAGE_SIZE */

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

#if KERNEL
#define __KXLD_KERNEL_UNUSED __unused
#else
#define __KXLD_KERNEL_UNUSED
#endif

#if !KERNEL
    #include "kxld.h"
    #include "kxld_types.h"
#else
    #include <libkern/kxld.h>
    #include <libkern/kxld_types.h>
#endif /* KERNEL */

#include "kxld_array.h"
#include "kxld_dict.h"
#include "kxld_kext.h"
#include "kxld_object.h"
#include "kxld_sym.h"
#include "kxld_symtab.h"
#include "kxld_util.h"
#include "kxld_vtable.h"

struct kxld_vtable;

struct kxld_context {
	KXLDKext *kext;
	KXLDArray *section_order;
	KXLDArray objects;
	KXLDArray dependencies;
	KXLDDict defined_symbols_by_name;
	KXLDDict defined_cxx_symbols_by_value;
	KXLDDict obsolete_symbols_by_name;
	KXLDDict vtables_by_name;
	KXLDFlags flags;
	KXLDAllocateCallback allocate_callback;
	cpu_type_t cputype;
	cpu_subtype_t cpusubtype;
};

// set to TRUE if the kext has a vmaddr_TEXT_EXEC != 0
boolean_t   isSplitKext         = FALSE;

// set to TRUE is we come in via kxld_link_file
boolean_t   isOldInterface      = FALSE;
uint32_t    kaslr_offsets_count = 0;
uint32_t   *kaslr_offsets = NULL;
uint32_t    kaslr_offsets_index = 0;

/*******************************************************************************
* Globals
*******************************************************************************/

/* Certain architectures alter the order of a kext's sections from its input
 * binary, so we track that order in a dictionary of arrays, with one array for
 * each architecture.  Since the kernel only has one architecture, we can
 * eliminate the dictionary and use a simple array.
 * XXX: If we ever use the linker in a multithreaded environment, we will need
 * locks around these global structures.
 */
#if KXLD_USER_OR_OBJECT
#if KERNEL
static KXLDArray *s_section_order;
#else
static KXLDDict *s_order_dict;
#endif
#endif

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

static kern_return_t init_context(KXLDContext *context, u_int ndependencies);
static KXLDObject * get_object_for_file(KXLDContext *context,
    u_char *file, u_long size, const char *name);
static kern_return_t allocate_split_kext(KXLDContext *context, splitKextLinkInfo * link_info);
static u_char * allocate_kext(KXLDContext *context, void *callback_data,
    kxld_addr_t *vmaddr, u_long *vmsize, u_char **linked_object_alloc_out);
static kern_return_t init_kext_objects(KXLDContext *context, u_char *file,
    u_long size, const char *name, KXLDDependency *dependencies,
    u_int ndependencies);
static void clear_context(KXLDContext *context);

/*******************************************************************************
*******************************************************************************/
kern_return_t
kxld_create_context(KXLDContext **_context,
    KXLDAllocateCallback allocate_callback, KXLDLoggingCallback logging_callback,
    KXLDFlags flags, cpu_type_t cputype, cpu_subtype_t cpusubtype,
    vm_size_t pagesize __KXLD_KERNEL_UNUSED)
{
	kern_return_t rval = KERN_FAILURE;
	KXLDContext       * context         = NULL;
	KXLDArray         * section_order   = NULL;
#if !KERNEL
	cpu_type_t        * cputype_p       = NULL;
#endif

	check(_context);
	if (isOldInterface) {
		check(allocate_callback);
	}
	check(logging_callback);
	*_context = NULL;

	context = kxld_calloc(sizeof(*context));
	require_action(context, finish, rval = KERN_RESOURCE_SHORTAGE);

	context->flags = flags;
	context->allocate_callback = allocate_callback;
	context->cputype = cputype;
	context->cpusubtype = cpusubtype;

#if !KERNEL
	if (pagesize) {
		kxld_set_cross_link_page_size(pagesize);
	}
#endif /* !KERNEL */

	kxld_set_logging_callback(logging_callback);

	context->kext = kxld_calloc(kxld_kext_sizeof());
	require_action(context->kext, finish, rval = KERN_RESOURCE_SHORTAGE);

	/* Check if we already have an order array for this arch */

#if KXLD_USER_OR_OBJECT
#if KERNEL
	context->section_order = s_section_order;
#else
	/* In userspace, create the dictionary if it doesn't already exist */
	if (!s_order_dict) {
		s_order_dict = kxld_calloc(sizeof(*s_order_dict));
		require_action(s_order_dict, finish, rval = KERN_RESOURCE_SHORTAGE);

		rval = kxld_dict_init(s_order_dict, kxld_dict_uint32_hash,
		    kxld_dict_uint32_cmp, 0);
		require_noerr(rval, finish);
	}

	context->section_order = kxld_dict_find(s_order_dict, &cputype);
#endif /* KERNEL */

	/* Create an order array for this arch if needed */

	if (!context->section_order) {
		section_order = kxld_calloc(sizeof(*section_order));
		require_action(section_order, finish, rval = KERN_RESOURCE_SHORTAGE);

#if KERNEL
		s_section_order = section_order;
#else
		/* In userspace, add the new array to the order dictionary */
		cputype_p = kxld_alloc(sizeof(*cputype_p));
		require_action(cputype_p, finish, rval = KERN_RESOURCE_SHORTAGE);
		*cputype_p = cputype;

		rval = kxld_dict_insert(s_order_dict, cputype_p, section_order);
		require_noerr(rval, finish);

		cputype_p = NULL;
#endif /* KERNEL */

		context->section_order = section_order;

		section_order = NULL;
	}
#endif /* KXLD_USER_OR_OBJECT */

	rval = KERN_SUCCESS;
	*_context = context;
	context = NULL;

finish:
	if (context) {
		kxld_destroy_context(context);
	}
	if (section_order) {
		kxld_free(section_order, sizeof(*section_order));
	}
#if !KERNEL
	if (cputype_p) {
		kxld_free(cputype_p, sizeof(*cputype_p));
	}
#endif

	return rval;
}

/*******************************************************************************
*******************************************************************************/
void
kxld_destroy_context(KXLDContext *context)
{
	KXLDObject *object = NULL;
	KXLDKext *dep = NULL;
	u_int i = 0;

	check(context);

	kxld_kext_deinit(context->kext);

	for (i = 0; i < context->objects.maxitems; ++i) {
		object = kxld_array_get_slot(&context->objects, i);
		kxld_object_deinit(object);
	}
	kxld_array_deinit(&context->objects);

	for (i = 0; i < context->dependencies.maxitems; ++i) {
		dep = kxld_array_get_slot(&context->dependencies, i);
		kxld_kext_deinit(dep);
	}
	kxld_array_deinit(&context->dependencies);

	kxld_dict_deinit(&context->defined_symbols_by_name);
	kxld_dict_deinit(&context->defined_cxx_symbols_by_value);
	kxld_dict_deinit(&context->obsolete_symbols_by_name);
	kxld_dict_deinit(&context->vtables_by_name);

	kxld_free(context->kext, kxld_kext_sizeof());
	kxld_free(context, sizeof(*context));

	kxld_print_memory_report();
}

/*******************************************************************************
*******************************************************************************/
kern_return_t
kxld_link_split_file(
	KXLDContext       * context,
	splitKextLinkInfo *link_info,
	const char        * name,
	void              * callback_data,
	KXLDDependency    * dependencies,
	u_int               ndependencies,
	kxld_addr_t       * kmod_info_kern)
{
	kern_return_t       rval                    = KERN_FAILURE;
	KXLDObject *        kext_object             = NULL;
	splitKextLinkInfo * my_link_info            = NULL;

	isSplitKext = (link_info->vmaddr_TEXT_EXEC != 0);
	isOldInterface = FALSE;

	kxld_set_logging_callback_data(name, callback_data);

	kxld_log(kKxldLogLinking, kKxldLogBasic, "Linking kext %s", name);

	kaslr_offsets_count = 0;
	kaslr_offsets_index = 0;
	kaslr_offsets = NULL;

	require_action(context, finish, rval = KERN_INVALID_ARGUMENT);
	require_action(link_info, finish, rval = KERN_INVALID_ARGUMENT);
	require_action(dependencies, finish, rval = KERN_INVALID_ARGUMENT);
	require_action(ndependencies, finish, rval = KERN_INVALID_ARGUMENT);
	require_action(kmod_info_kern, finish, rval = KERN_INVALID_ARGUMENT);

	rval = init_context(context, ndependencies);
	require_noerr(rval, finish);

	rval = init_kext_objects(context,
	    link_info->kextExecutable,
	    link_info->kextSize,
	    name,
	    dependencies, ndependencies);
	require_noerr(rval, finish);

	kext_object = get_object_for_file(context,
	    link_info->kextExecutable,
	    link_info->kextSize,
	    name);
	require_action(kext_object, finish, rval = KERN_FAILURE);

	// copy vmaddrs and fileoffsets for split segments into kext_object
	kxld_object_set_link_info(kext_object, link_info);

	my_link_info = kxld_object_get_link_info(kext_object);

	rval = allocate_split_kext(context, my_link_info);
	require_noerr(rval, finish);

#if SPLIT_KEXTS_DEBUG
	kxld_log(kKxldLogLinking, kKxldLogErr, "Linking kext %s", name);
	kxld_show_split_info(link_info);
#endif // SPLIT_KEXTS_DEBUG

	rval = kxld_kext_relocate(context->kext,
	    (kxld_addr_t)my_link_info,
	    &context->vtables_by_name,
	    &context->defined_symbols_by_name,
	    &context->obsolete_symbols_by_name,
	    &context->defined_cxx_symbols_by_value);
	require_noerr(rval, finish);

	rval = kxld_kext_export_linked_object(context->kext,
	    (void *) my_link_info,
	    kmod_info_kern);
	require_noerr(rval, finish);

	// pass back info about linked kext
	link_info->kaslr_offsets_count = kaslr_offsets_count;
	link_info->kaslr_offsets = kaslr_offsets;
	link_info->linkedKext = my_link_info->linkedKext;
	link_info->linkedKextSize = my_link_info->linkedKextSize;

	if (kaslr_offsets_count != kaslr_offsets_index) {
		kxld_log(kKxldLogLinking, kKxldLogErr, "[ERROR] %s: KASLR pointers: count=%d, but only populated %d!", name, kaslr_offsets_count, kaslr_offsets_index);
		rval = KERN_FAILURE;
		goto finish;
	}

	// the values are now the responsibility of the caller
	kaslr_offsets_count = 0;
	kaslr_offsets_index = 0;
	kaslr_offsets = NULL;

	rval = KERN_SUCCESS;
finish:
	clear_context(context);
	kxld_set_logging_callback_data(NULL, NULL);

	return rval;
}

/*******************************************************************************
*******************************************************************************/
kern_return_t
kxld_link_file(
	KXLDContext       * context,
	u_char            * file,
	u_long              size,
	const char        * name,
	void              * callback_data,
	KXLDDependency    * dependencies,
	u_int               ndependencies,
	u_char           ** linked_object_out,
	kxld_addr_t       * kmod_info_kern)
{
	kern_return_t       rval                    = KERN_FAILURE;
	kxld_addr_t         vmaddr                  = 0;
	u_long              vmsize                  = 0;
	u_char            * linked_object           = NULL;
	u_char            * linked_object_alloc     = NULL;

	kaslr_offsets_count = 0;
	kaslr_offsets_index = 0;
	kaslr_offsets = NULL;

	kxld_set_logging_callback_data(name, callback_data);

	kxld_log(kKxldLogLinking, kKxldLogBasic, "Linking kext %s", name);

	require_action(context, finish, rval = KERN_INVALID_ARGUMENT);
	require_action(dependencies, finish, rval = KERN_INVALID_ARGUMENT);
	require_action(ndependencies, finish, rval = KERN_INVALID_ARGUMENT);
	require_action(file, finish, rval = KERN_INVALID_ARGUMENT);
	require_action(size, finish, rval = KERN_INVALID_ARGUMENT);
	require_action(linked_object_out, finish, rval = KERN_INVALID_ARGUMENT);
	require_action(kmod_info_kern, finish, rval = KERN_INVALID_ARGUMENT);

	isSplitKext = FALSE;
	isOldInterface = TRUE;

	rval = init_context(context, ndependencies);
	require_noerr(rval, finish);

	rval = init_kext_objects(context, file, size, name,
	    dependencies, ndependencies);
	require_noerr(rval, finish);

	linked_object = allocate_kext(context, callback_data,
	    &vmaddr, &vmsize, &linked_object_alloc);
	require_action(linked_object, finish, rval = KERN_RESOURCE_SHORTAGE);


	rval = kxld_kext_relocate(context->kext,
	    vmaddr,
	    &context->vtables_by_name,
	    &context->defined_symbols_by_name,
	    &context->obsolete_symbols_by_name,
	    &context->defined_cxx_symbols_by_value);
	require_noerr(rval, finish);

	rval = kxld_kext_export_linked_object(context->kext,
	    (void *) linked_object,
	    kmod_info_kern);
	require_noerr(rval, finish);
	*linked_object_out = linked_object;

	linked_object_alloc = NULL;

	rval = KERN_SUCCESS;
finish:
	if (linked_object_alloc) {
		kxld_page_free_untracked(linked_object_alloc, vmsize);
	}

	clear_context(context);
	kxld_set_logging_callback_data(NULL, NULL);

	return rval;
}


/*******************************************************************************
*******************************************************************************/
static kern_return_t
init_context(KXLDContext *context, u_int ndependencies)
{
	kern_return_t rval = KERN_FAILURE;

	/* Create an array of objects large enough to hold an object
	 * for every dependency, an interface for each dependency, and a kext. */
	rval = kxld_array_init(&context->objects,
	    kxld_object_sizeof(), 2 * ndependencies + 1);
	require_noerr(rval, finish);

	rval = kxld_array_init(&context->dependencies,
	    kxld_kext_sizeof(), ndependencies);
	require_noerr(rval, finish);

	rval = kxld_dict_init(&context->defined_symbols_by_name,
	    kxld_dict_string_hash, kxld_dict_string_cmp, 0);
	require_noerr(rval, finish);

	rval = kxld_dict_init(&context->defined_cxx_symbols_by_value,
	    kxld_dict_kxldaddr_hash, kxld_dict_kxldaddr_cmp, 0);
	require_noerr(rval, finish);

	rval = kxld_dict_init(&context->obsolete_symbols_by_name,
	    kxld_dict_string_hash, kxld_dict_string_cmp, 0);
	require_noerr(rval, finish);

	rval = kxld_dict_init(&context->vtables_by_name, kxld_dict_string_hash,
	    kxld_dict_string_cmp, 0);
	require_noerr(rval, finish);

	rval = KERN_SUCCESS;
finish:
	return rval;
}

/*******************************************************************************
*******************************************************************************/
static kern_return_t
init_kext_objects(KXLDContext *context,
    u_char *file,
    u_long size,
    const char *name,
    KXLDDependency *dependencies,
    u_int ndependencies)
{
	kern_return_t rval = KERN_FAILURE;
	KXLDKext *kext = NULL;
	KXLDObject *kext_object = NULL;
	KXLDObject *interface_object = NULL;
	u_int i = 0;

	/* Create a kext object for each dependency.  If it's a direct dependency,
	 * export its symbols by name by value.  If it's indirect, just export the
	 * C++ symbols by value.
	 */
	for (i = 0; i < ndependencies; ++i) {
		kext = kxld_array_get_item(&context->dependencies, i);
		kext_object = NULL;
		interface_object = NULL;

		kext_object = get_object_for_file(context, dependencies[i].kext,
		    dependencies[i].kext_size, dependencies[i].kext_name);
		require_action(kext_object, finish, rval = KERN_FAILURE);

		if (dependencies[i].interface) {
			interface_object = get_object_for_file(context,
			    dependencies[i].interface, dependencies[i].interface_size,
			    dependencies[i].interface_name);
			require_action(interface_object, finish, rval = KERN_FAILURE);
		}

		rval = kxld_kext_init(kext, kext_object, interface_object);
		require_noerr(rval, finish);

		if (dependencies[i].is_direct_dependency) {
			rval = kxld_kext_export_symbols(kext,
			    &context->defined_symbols_by_name,
			    &context->obsolete_symbols_by_name,
			    &context->defined_cxx_symbols_by_value);
			require_noerr(rval, finish);
		} else {
			rval = kxld_kext_export_symbols(kext,
			    /* defined_symbols */ NULL, /* obsolete_symbols */ NULL,
			    &context->defined_cxx_symbols_by_value);
			require_noerr(rval, finish);
		}
	}

	/* Export the vtables for all of the dependencies. */
	for (i = 0; i < context->dependencies.nitems; ++i) {
		kext = kxld_array_get_item(&context->dependencies, i);

		rval = kxld_kext_export_vtables(kext,
		    &context->defined_cxx_symbols_by_value,
		    &context->defined_symbols_by_name,
		    &context->vtables_by_name);
		require_noerr(rval, finish);
	}

	/* Create a kext object for the kext we're linking and export its locally
	 * defined C++ symbols.
	 */
	kext_object = get_object_for_file(context, file, size, name);
	require_action(kext_object, finish, rval = KERN_FAILURE);

	rval = kxld_kext_init(context->kext, kext_object, /* interface */ NULL);
	require_noerr(rval, finish);

	rval = kxld_kext_export_symbols(context->kext,
	    /* defined_symbols */ NULL, /* obsolete_symbols */ NULL,
	    &context->defined_cxx_symbols_by_value);
	require_noerr(rval, finish);

	rval = KERN_SUCCESS;
finish:
	return rval;
}

/*******************************************************************************
*******************************************************************************/
static KXLDObject *
get_object_for_file(KXLDContext *context, u_char *file, u_long size,
    const char *name)
{
	KXLDObject *rval = NULL;
	KXLDObject *object = NULL;
	kern_return_t result = 0;
	u_int i = 0;

	for (i = 0; i < context->objects.nitems; ++i) {
		object = kxld_array_get_item(&context->objects, i);

		if (!kxld_object_get_file(object)) {
			result = kxld_object_init_from_macho(object, file, size, name,
			    context->section_order, context->cputype, context->cpusubtype, context->flags);
			require_noerr(result, finish);

			rval = object;
			break;
		}

		if (kxld_object_get_file(object) == file) {
			rval = object;
			break;
		}
	}

finish:
	return rval;
}

#include <mach-o/loader.h>

/*******************************************************************************
*******************************************************************************/
static kern_return_t
allocate_split_kext(KXLDContext *context, splitKextLinkInfo * link_info)
{
	kern_return_t       rval                    = KERN_FAILURE;
	u_long              vmsize                  = 0;
	u_long              header_size             = 0;
	u_char            * linked_object           = NULL;

	kxld_kext_get_vmsize(context->kext, &header_size, &vmsize);

	if (isSplitKext) {
		/* get __LINKEDIT vmsize */
		kxld_kext_get_vmsize_for_seg_by_name(context->kext, SEG_LINKEDIT, &vmsize);
		// add in the gaps
		vmsize += (link_info->vmaddr_LINKEDIT - link_info->vmaddr_TEXT);
	}
	link_info->linkedKextSize = vmsize;

	linked_object = kxld_page_alloc_untracked(link_info->linkedKextSize);
	require(linked_object, finish);
	link_info->linkedKext = linked_object;
	rval = KERN_SUCCESS;

finish:
	return rval;
}

/*******************************************************************************
*******************************************************************************/
static u_char *
allocate_kext(KXLDContext *context,
    void *callback_data,
    kxld_addr_t *vmaddr_out,
    u_long *vmsize_out,
    u_char **linked_object_alloc_out)
{
	KXLDAllocateFlags   flags                   = 0;
	kxld_addr_t         vmaddr                  = 0;
	u_long              vmsize                  = 0;
	u_long              header_size             = 0;
	u_char            * linked_object           = NULL;

	*linked_object_alloc_out = NULL;

	kxld_kext_get_vmsize(context->kext, &header_size, &vmsize);

	vmaddr = context->allocate_callback(vmsize, &flags, callback_data);
	require_action(!(vmaddr & (kxld_get_effective_page_size() - 1)), finish,
	    kxld_log(kKxldLogLinking, kKxldLogErr,
	    "Load address %p is not page-aligned.",
	    (void *) (uintptr_t) vmaddr));

	/* Zero out the memory before we fill it.  We fill this buffer in a
	 * sparse fashion, and it's simpler to clear it now rather than
	 * track and zero any pieces we didn't touch after we've written
	 * all of the sections to memory.
	 */
	if (flags & kKxldAllocateWritable) {
		linked_object = (u_char *) (u_long) vmaddr;
		bzero(linked_object, vmsize);
	} else {
		linked_object = kxld_page_alloc_untracked(vmsize);
		require(linked_object, finish);

		*linked_object_alloc_out = linked_object;
	}

	kxld_kext_set_linked_object_size(context->kext, vmsize);

	*vmaddr_out = vmaddr;
	*vmsize_out = vmsize;

finish:
	return linked_object;
}

/*******************************************************************************
*******************************************************************************/
static void
clear_context(KXLDContext *context)
{
	KXLDObject * object = NULL;
	KXLDKext   * dep     = NULL;
	u_int i = 0;

	check(context);

	kxld_kext_clear(context->kext);

	for (i = 0; i < context->objects.nitems; ++i) {
		object = kxld_array_get_item(&context->objects, i);
		kxld_object_clear(object);
	}
	kxld_array_reset(&context->objects);

	for (i = 0; i < context->dependencies.nitems; ++i) {
		dep = kxld_array_get_item(&context->dependencies, i);
		kxld_kext_clear(dep);
	}
	kxld_array_reset(&context->dependencies);

	kxld_dict_clear(&context->defined_symbols_by_name);
	kxld_dict_clear(&context->defined_cxx_symbols_by_value);
	kxld_dict_clear(&context->obsolete_symbols_by_name);
	kxld_dict_clear(&context->vtables_by_name);
}