diff --git a/lib/libfdt/fdt_sw.c b/lib/libfdt/fdt_sw.c
index 6d33cc2..26759d5 100644
--- a/lib/libfdt/fdt_sw.c
+++ b/lib/libfdt/fdt_sw.c
@@ -1,52 +1,7 @@
+// SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-Clause)
 /*
  * libfdt - Flat Device Tree manipulation
  * Copyright (C) 2006 David Gibson, IBM Corporation.
- *
- * libfdt is dual licensed: you can use it either under the terms of
- * the GPL, or the BSD license, at your option.
- *
- *  a) This library is free software; you can redistribute it and/or
- *     modify it under the terms of the GNU General Public License as
- *     published by the Free Software Foundation; either version 2 of the
- *     License, or (at your option) any later version.
- *
- *     This library is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- *
- *     You should have received a copy of the GNU General Public
- *     License along with this library; if not, write to the Free
- *     Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
- *     MA 02110-1301 USA
- *
- * Alternatively,
- *
- *  b) 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 COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.
  */
 #include "libfdt_env.h"
 
@@ -55,21 +10,87 @@
 
 #include "libfdt_internal.h"
 
-static int fdt_sw_check_header_(void *fdt)
+static int fdt_sw_probe_(void *fdt)
 {
-	if (fdt_magic(fdt) != FDT_SW_MAGIC)
-		return -FDT_ERR_BADMAGIC;
-	/* FIXME: should check more details about the header state */
+	if (!can_assume(VALID_INPUT)) {
+		if (fdt_magic(fdt) == FDT_MAGIC)
+			return -FDT_ERR_BADSTATE;
+		else if (fdt_magic(fdt) != FDT_SW_MAGIC)
+			return -FDT_ERR_BADMAGIC;
+	}
+
 	return 0;
 }
 
-#define FDT_SW_CHECK_HEADER(fdt) \
+#define FDT_SW_PROBE(fdt) \
 	{ \
 		int err; \
-		if ((err = fdt_sw_check_header_(fdt)) != 0) \
+		if ((err = fdt_sw_probe_(fdt)) != 0) \
 			return err; \
 	}
 
+/* 'memrsv' state:	Initial state after fdt_create()
+ *
+ * Allowed functions:
+ *	fdt_add_reservmap_entry()
+ *	fdt_finish_reservemap()		[moves to 'struct' state]
+ */
+static int fdt_sw_probe_memrsv_(void *fdt)
+{
+	int err = fdt_sw_probe_(fdt);
+	if (err)
+		return err;
+
+	if (!can_assume(VALID_INPUT) && fdt_off_dt_strings(fdt) != 0)
+		return -FDT_ERR_BADSTATE;
+	return 0;
+}
+
+#define FDT_SW_PROBE_MEMRSV(fdt) \
+	{ \
+		int err; \
+		if ((err = fdt_sw_probe_memrsv_(fdt)) != 0) \
+			return err; \
+	}
+
+/* 'struct' state:	Enter this state after fdt_finish_reservemap()
+ *
+ * Allowed functions:
+ *	fdt_begin_node()
+ *	fdt_end_node()
+ *	fdt_property*()
+ *	fdt_finish()			[moves to 'complete' state]
+ */
+static int fdt_sw_probe_struct_(void *fdt)
+{
+	int err = fdt_sw_probe_(fdt);
+	if (err)
+		return err;
+
+	if (!can_assume(VALID_INPUT) &&
+	    fdt_off_dt_strings(fdt) != fdt_totalsize(fdt))
+		return -FDT_ERR_BADSTATE;
+	return 0;
+}
+
+#define FDT_SW_PROBE_STRUCT(fdt) \
+	{ \
+		int err; \
+		if ((err = fdt_sw_probe_struct_(fdt)) != 0) \
+			return err; \
+	}
+
+static inline uint32_t sw_flags(void *fdt)
+{
+	/* assert: (fdt_magic(fdt) == FDT_SW_MAGIC) */
+	return fdt_last_comp_version(fdt);
+}
+
+/* 'complete' state:	Enter this state after fdt_finish()
+ *
+ * Allowed functions: none
+ */
+
 static void *fdt_grab_space_(void *fdt, size_t len)
 {
 	int offset = fdt_size_dt_struct(fdt);
@@ -85,38 +106,59 @@
 	return fdt_offset_ptr_w_(fdt, offset);
 }
 
-int fdt_create(void *buf, int bufsize)
+int fdt_create_with_flags(void *buf, int bufsize, uint32_t flags)
 {
+	const size_t hdrsize = FDT_ALIGN(sizeof(struct fdt_header),
+					 sizeof(struct fdt_reserve_entry));
 	void *fdt = buf;
 
-	if (bufsize < sizeof(struct fdt_header))
+	if (bufsize < hdrsize)
 		return -FDT_ERR_NOSPACE;
 
+	if (flags & ~FDT_CREATE_FLAGS_ALL)
+		return -FDT_ERR_BADFLAGS;
+
 	memset(buf, 0, bufsize);
 
+	/*
+	 * magic and last_comp_version keep intermediate state during the fdt
+	 * creation process, which is replaced with the proper FDT format by
+	 * fdt_finish().
+	 *
+	 * flags should be accessed with sw_flags().
+	 */
 	fdt_set_magic(fdt, FDT_SW_MAGIC);
 	fdt_set_version(fdt, FDT_LAST_SUPPORTED_VERSION);
-	fdt_set_last_comp_version(fdt, FDT_FIRST_SUPPORTED_VERSION);
+	fdt_set_last_comp_version(fdt, flags);
+
 	fdt_set_totalsize(fdt,  bufsize);
 
-	fdt_set_off_mem_rsvmap(fdt, FDT_ALIGN(sizeof(struct fdt_header),
-					      sizeof(struct fdt_reserve_entry)));
+	fdt_set_off_mem_rsvmap(fdt, hdrsize);
 	fdt_set_off_dt_struct(fdt, fdt_off_mem_rsvmap(fdt));
-	fdt_set_off_dt_strings(fdt, bufsize);
+	fdt_set_off_dt_strings(fdt, 0);
 
 	return 0;
 }
 
+int fdt_create(void *buf, int bufsize)
+{
+	return fdt_create_with_flags(buf, bufsize, 0);
+}
+
 int fdt_resize(void *fdt, void *buf, int bufsize)
 {
 	size_t headsize, tailsize;
 	char *oldtail, *newtail;
 
-	FDT_SW_CHECK_HEADER(fdt);
+	FDT_SW_PROBE(fdt);
 
-	headsize = fdt_off_dt_struct(fdt);
+	headsize = fdt_off_dt_struct(fdt) + fdt_size_dt_struct(fdt);
 	tailsize = fdt_size_dt_strings(fdt);
 
+	if (!can_assume(VALID_DTB) &&
+	    headsize + tailsize > fdt_totalsize(fdt))
+		return -FDT_ERR_INTERNAL;
+
 	if ((headsize + tailsize) > bufsize)
 		return -FDT_ERR_NOSPACE;
 
@@ -133,8 +175,9 @@
 		memmove(buf, fdt, headsize);
 	}
 
-	fdt_set_off_dt_strings(buf, bufsize);
 	fdt_set_totalsize(buf, bufsize);
+	if (fdt_off_dt_strings(buf))
+		fdt_set_off_dt_strings(buf, bufsize);
 
 	return 0;
 }
@@ -144,10 +187,7 @@
 	struct fdt_reserve_entry *re;
 	int offset;
 
-	FDT_SW_CHECK_HEADER(fdt);
-
-	if (fdt_size_dt_struct(fdt))
-		return -FDT_ERR_BADSTATE;
+	FDT_SW_PROBE_MEMRSV(fdt);
 
 	offset = fdt_off_dt_struct(fdt);
 	if ((offset + sizeof(*re)) > fdt_totalsize(fdt))
@@ -164,16 +204,23 @@
 
 int fdt_finish_reservemap(void *fdt)
 {
-	return fdt_add_reservemap_entry(fdt, 0, 0);
+	int err = fdt_add_reservemap_entry(fdt, 0, 0);
+
+	if (err)
+		return err;
+
+	fdt_set_off_dt_strings(fdt, fdt_totalsize(fdt));
+	return 0;
 }
 
 int fdt_begin_node(void *fdt, const char *name)
 {
 	struct fdt_node_header *nh;
-	int namelen = strlen(name) + 1;
+	int namelen;
 
-	FDT_SW_CHECK_HEADER(fdt);
+	FDT_SW_PROBE_STRUCT(fdt);
 
+	namelen = strlen(name) + 1;
 	nh = fdt_grab_space_(fdt, sizeof(*nh) + FDT_TAGALIGN(namelen));
 	if (! nh)
 		return -FDT_ERR_NOSPACE;
@@ -187,7 +234,7 @@
 {
 	fdt32_t *en;
 
-	FDT_SW_CHECK_HEADER(fdt);
+	FDT_SW_PROBE_STRUCT(fdt);
 
 	en = fdt_grab_space_(fdt, FDT_TAGSIZE);
 	if (! en)
@@ -197,19 +244,13 @@
 	return 0;
 }
 
-static int fdt_find_add_string_(void *fdt, const char *s)
+static int fdt_add_string_(void *fdt, const char *s)
 {
 	char *strtab = (char *)fdt + fdt_totalsize(fdt);
-	const char *p;
 	int strtabsize = fdt_size_dt_strings(fdt);
 	int len = strlen(s) + 1;
 	int struct_top, offset;
 
-	p = fdt_find_string_(strtab - strtabsize, strtabsize, s);
-	if (p)
-		return p - strtab;
-
-	/* Add it */
 	offset = -strtabsize - len;
 	struct_top = fdt_off_dt_struct(fdt) + fdt_size_dt_struct(fdt);
 	if (fdt_totalsize(fdt) + offset < struct_top)
@@ -220,20 +261,56 @@
 	return offset;
 }
 
+/* Must only be used to roll back in case of error */
+static void fdt_del_last_string_(void *fdt, const char *s)
+{
+	int strtabsize = fdt_size_dt_strings(fdt);
+	int len = strlen(s) + 1;
+
+	fdt_set_size_dt_strings(fdt, strtabsize - len);
+}
+
+static int fdt_find_add_string_(void *fdt, const char *s, int *allocated)
+{
+	char *strtab = (char *)fdt + fdt_totalsize(fdt);
+	int strtabsize = fdt_size_dt_strings(fdt);
+	const char *p;
+
+	*allocated = 0;
+
+	p = fdt_find_string_(strtab - strtabsize, strtabsize, s);
+	if (p)
+		return p - strtab;
+
+	*allocated = 1;
+
+	return fdt_add_string_(fdt, s);
+}
+
 int fdt_property_placeholder(void *fdt, const char *name, int len, void **valp)
 {
 	struct fdt_property *prop;
 	int nameoff;
+	int allocated;
 
-	FDT_SW_CHECK_HEADER(fdt);
+	FDT_SW_PROBE_STRUCT(fdt);
 
-	nameoff = fdt_find_add_string_(fdt, name);
+	/* String de-duplication can be slow, _NO_NAME_DEDUP skips it */
+	if (sw_flags(fdt) & FDT_CREATE_FLAG_NO_NAME_DEDUP) {
+		allocated = 1;
+		nameoff = fdt_add_string_(fdt, name);
+	} else {
+		nameoff = fdt_find_add_string_(fdt, name, &allocated);
+	}
 	if (nameoff == 0)
 		return -FDT_ERR_NOSPACE;
 
 	prop = fdt_grab_space_(fdt, sizeof(*prop) + FDT_TAGALIGN(len));
-	if (! prop)
+	if (! prop) {
+		if (allocated)
+			fdt_del_last_string_(fdt, name);
 		return -FDT_ERR_NOSPACE;
+	}
 
 	prop->tag = cpu_to_fdt32(FDT_PROP);
 	prop->nameoff = cpu_to_fdt32(nameoff);
@@ -262,7 +339,7 @@
 	uint32_t tag;
 	int offset, nextoffset;
 
-	FDT_SW_CHECK_HEADER(fdt);
+	FDT_SW_PROBE_STRUCT(fdt);
 
 	/* Add terminator */
 	end = fdt_grab_space_(fdt, sizeof(*end));
@@ -295,6 +372,10 @@
 
 	/* Finally, adjust the header */
 	fdt_set_totalsize(fdt, newstroffset + fdt_size_dt_strings(fdt));
+
+	/* And fix up fields that were keeping intermediate state. */
+	fdt_set_last_comp_version(fdt, FDT_FIRST_SUPPORTED_VERSION);
 	fdt_set_magic(fdt, FDT_MAGIC);
+
 	return 0;
 }