This is xnu-8019. See this file in:
/*
 * Copyright (c) 2020 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 <IOKit/IOLib.h>
#include <kern/debug.h> // for panic()

#include <libkern/ptrauth_utils.h>

/*
 * On ptrauth systems, ptrauth_utils_sign_blob_generic is implemented
 * in osfmk/arm64/machine_routines_asm.s
 */

#if !__has_feature(ptrauth_calls)
ptrauth_generic_signature_t
ptrauth_utils_sign_blob_generic(__unused const void * ptr, __unused size_t len_bytes, __unused uint64_t data, __unused int flags)
{
	return 0;
}
#endif // __has_feature(ptrauth_calls)


/*
 * ptrauth_utils_auth_blob_generic
 *
 * Authenticate signature produced by ptrauth_utils_sign_blob_generic
 */

#if __has_feature(ptrauth_calls)
__attribute__((noinline))
void
ptrauth_utils_auth_blob_generic(const void * ptr, size_t len_bytes, uint64_t data, int flags, ptrauth_generic_signature_t signature)
{
	ptrauth_generic_signature_t calculated_signature = 0;

	if (ptr == NULL) {
		if (flags & PTRAUTH_NON_NULL) {
			panic("ptrauth_utils_auth_blob_generic: ptr must not be NULL");
		} else {
			return;
		}
	}

	if ((calculated_signature = ptrauth_utils_sign_blob_generic(ptr, len_bytes, data, flags)) == signature) {
		return;
	} else {
		panic("signature mismatch for %lu bytes at %p, calculated %lx vs %lx", len_bytes,
		    ptr,
		    calculated_signature,
		    signature);
	}
}
#else
void
ptrauth_utils_auth_blob_generic(__unused const void * ptr, __unused size_t len_bytes, __unused uint64_t data, __unused int flags, __unused ptrauth_generic_signature_t signature)
{
	return;
}
#endif // __has_feature(ptrauth_calls)