Index: sys/amd64/include/cpu.h
===================================================================
--- sys/amd64/include/cpu.h
+++ sys/amd64/include/cpu.h
@@ -92,6 +92,10 @@
 	return (rdtsc());
 }
 
+#define MEMSET_EARLY_FUNC       memset_std
+#define MEMCPY_EARLY_FUNC       memcpy_std
+#define MEMMOVE_EARLY_FUNC      memmove_std
+
 #endif
 
 #endif /* !_MACHINE_CPU_H_ */
Index: sys/conf/files
===================================================================
--- sys/conf/files
+++ sys/conf/files
@@ -3876,6 +3876,7 @@
 kern/subr_counter.c		standard
 kern/subr_devstat.c		standard
 kern/subr_disk.c		standard
+kern/subr_early.c		standard
 kern/subr_epoch.c		standard
 kern/subr_eventhandler.c	standard
 kern/subr_fattime.c		standard
Index: sys/kern/link_elf.c
===================================================================
--- sys/kern/link_elf.c
+++ sys/kern/link_elf.c
@@ -1682,14 +1682,10 @@
 {
 	struct elf_file eff;
 	elf_file_t ef;
-	volatile char *c;
-	size_t i;
 
 	ef = &eff;
 
-	/* Do not use bzero/memset before ireloc is done. */
-	for (c = (char *)ef, i = 0; i < sizeof(*ef); i++)
-		c[i] = 0;
+	bzero_early(ef, sizeof(*ef));
 
 	ef->modptr = kmdp;
 	ef->dynamic = (Elf_Dyn *)&_DYNAMIC;
Index: sys/kern/subr_early.c
===================================================================
--- /dev/null
+++ sys/kern/subr_early.c
@@ -0,0 +1,76 @@
+/*-
+ * Copyright (c) 2018 The FreeBSD Foundation
+ *
+ * This software was developed by Mateusz Guzik <mjg@FreeBSD.org>
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/types.h>
+#include <sys/systm.h>
+#include <machine/cpu.h>
+
+#ifndef	MEMSET_EARLY_FUNC
+#define	MEMSET_EARLY_FUNC	memset
+#else
+void *MEMSET_EARLY_FUNC(void *, int, size_t);
+#endif
+
+void *
+memset_early(void *buf, int c, size_t len)
+{
+
+	return (MEMSET_EARLY_FUNC(buf, c, len));
+}
+
+#ifndef	MEMCPY_EARLY_FUNC
+#define	MEMCPY_EARLY_FUNC	memcpy
+#else
+void *MEMCPY_EARLY_FUNC(void *, const void *, size_t);
+#endif
+
+void *
+memcpy_early(void *to, const void *from, size_t len)
+{
+
+	return (MEMCPY_EARLY_FUNC(to, from, len));
+}
+
+#ifndef	MEMMOVE_EARLY_FUNC
+#define	MEMMOVE_EARLY_FUNC	memmove
+#else
+void *MEMMOVE_EARLY_FUNC(void *, const void *, size_t);
+#endif
+
+void *
+memmove_early(void *to, const void *from, size_t len)
+{
+
+	return (MEMMOVE_EARLY_FUNC(to, from, len));
+}
Index: sys/sys/systm.h
===================================================================
--- sys/sys/systm.h
+++ sys/sys/systm.h
@@ -324,6 +324,12 @@
 int	memcmp(const void *b1, const void *b2, size_t len);
 #define memcmp(b1, b2, len) __builtin_memcmp((b1), (b2), (len))
 
+void	*memset_early(void * _Nonnull buf, int c, size_t len);
+#define bzero_early(buf, len) memset_early((buf), 0, (len))
+void	*memcpy_early(void * _Nonnull to, const void * _Nonnull from, size_t len);
+void	*memmove_early(void * _Nonnull dest, const void * _Nonnull src, size_t n);
+#define bcopy_early(from, to, len) memmove_early((to), (from), (len))
+
 int	copystr(const void * _Nonnull __restrict kfaddr,
 	    void * _Nonnull __restrict kdaddr, size_t len,
 	    size_t * __restrict lencopied);
Index: sys/x86/x86/ucode.c
===================================================================
--- sys/x86/x86/ucode.c
+++ sys/x86/x86/ucode.c
@@ -355,8 +355,7 @@
 		if (match != NULL) {
 			addr = map_ucode(free, len);
 			/* We can't use memcpy() before ifunc resolution. */
-			for (i = 0; i < len; i++)
-				addr[i] = ((volatile uint8_t *)match)[i];
+			memcpy_early(addr, match, len);
 			match = addr;
 
 			error = ucode_loader->load(match, false, &nrev, &orev);
Index: sys/x86/xen/pv.c
===================================================================
--- sys/x86/xen/pv.c
+++ sys/x86/xen/pv.c
@@ -259,7 +259,7 @@
 	 */
 	kenv = (void *)(physfree + KERNBASE);
 	physfree += PAGE_SIZE;
-	bzero(kenv, PAGE_SIZE);
+	bzero_early(kenv, PAGE_SIZE);
 	init_static_kenv(kenv, PAGE_SIZE);
 
 	/* Set the hooks for early functions that diverge from bare metal */
@@ -320,7 +320,7 @@
 	 */
 	kenv = (void *)(physfree + KERNBASE);
 	physfree += PAGE_SIZE;
-	bzero(kenv, PAGE_SIZE);
+	bzero_early(kenv, PAGE_SIZE);
 	init_static_kenv(kenv, PAGE_SIZE);
 
 	if (start_info->modlist_paddr != 0) {