libfdt: Add fdt_check_full() function

This new function implements a complete and thorough check of an fdt blob's
structure.  Given a buffer containing an fdt, it should return 0 only if
the fdt within is structurally sound in all regards.  It doesn't check
anything about the blob's contents (i.e. the actual values of the nodes and
properties), of course.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Simon Glass <sjg@chromium.org>

libfdt/fdt_ro.c

@@ -857,3 +857,66 @@ int fdt_node_offset_by_compatible(const void *fdt, int startoffset,
 
 	return offset; /* error from fdt_next_node() */
 }
+
+int fdt_check_full(const void *fdt, size_t bufsize)
+{
+	int err;
+	int num_memrsv;
+	int offset, nextoffset = 0;
+	uint32_t tag;
+	unsigned depth = 0;
+	const void *prop;
+	const char *propname;
+
+	if (bufsize < FDT_V1_SIZE)
+		return -FDT_ERR_TRUNCATED;
+	err = fdt_check_header(fdt);
+	if (err != 0)
+		return err;
+	if (bufsize < fdt_totalsize(fdt))
+		return -FDT_ERR_TRUNCATED;
+
+	num_memrsv = fdt_num_mem_rsv(fdt);
+	if (num_memrsv < 0)
+		return num_memrsv;
+
+	while (1) {
+		offset = nextoffset;
+		tag = fdt_next_tag(fdt, offset, &nextoffset);
+
+		if (nextoffset < 0)
+			return nextoffset;
+
+		switch (tag) {
+		case FDT_NOP:
+			break;
+
+		case FDT_END:
+			if (depth != 0)
+				return -FDT_ERR_BADSTRUCTURE;
+			return 0;
+
+		case FDT_BEGIN_NODE:
+			depth++;
+			if (depth > INT_MAX)
+				return -FDT_ERR_BADSTRUCTURE;
+			break;
+
+		case FDT_END_NODE:
+			if (depth == 0)
+				return -FDT_ERR_BADSTRUCTURE;
+			depth--;
+			break;
+
+		case FDT_PROP:
+			prop = fdt_getprop_by_offset(fdt, offset, &propname,
+						     &err);
+			if (!prop)
+				return err;
+			break;
+
+		default:
+			return -FDT_ERR_INTERNAL;
+		}
+	}
+}

libfdt/libfdt.h

@@ -298,6 +298,8 @@ int fdt_move(const void *fdt, void *buf, int bufsize);
 /* Read-only functions                                                */
 /**********************************************************************/
 
+int fdt_check_full(const void *fdt, size_t bufsize);
+
 /**
  * fdt_get_string - retrieve a string from the strings block of a device tree
  * @fdt: pointer to the device tree blob

tests/.gitignore

@@ -8,6 +8,7 @@ tmp.*
 /asm_tree_dump
 /boot-cpuid
 /char_literal
+/check_full
 /check_header
 /check_path
 /del_node

tests/Makefile.tests

@@ -26,7 +26,7 @@ LIB_TESTS_L = get_mem_rsv \
 	property_iterate \
 	subnode_iterate \
 	overlay overlay_bad_fixup \
-	check_path check_header
+	check_path check_header check_full
 LIB_TESTS = $(LIB_TESTS_L:%=$(TESTS_PREFIX)%)
 
 LIBTREE_TESTS_L = truncated_property truncated_string truncated_memrsv

tests/check_full.c

@@ -0,0 +1,63 @@
+/*
+ * libfdt - Flat Device Tree manipulation
+ *	Tests if two given dtbs are structurally equal (including order)
+ * Copyright (C) 2007 David Gibson, IBM Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser 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
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+#include <libfdt.h>
+
+#include "tests.h"
+#include "testdata.h"
+
+static int expect_bad; /* = 0 */
+
+int main(int argc, char *argv[])
+{
+	const char *filename;
+	char *fdt;
+	size_t len;
+	int err;
+
+	test_init(argc, argv);
+	if ((argc != 2)
+	    && ((argc != 3) || !streq(argv[1], "-n")))
+		CONFIG("Usage: %s [-n] <dtb file>", argv[0]);
+	if (argc == 3)
+		expect_bad = 1;
+
+	filename = argv[argc-1];
+	err = utilfdt_read_err(filename, &fdt, &len);
+	if (err)
+		CONFIG("Couldn't open blob from \"%s\": %s",
+		       filename, strerror(err));
+
+	vg_prepare_blob(fdt, len);
+
+	err = fdt_check_full(fdt, len);
+
+	if (expect_bad && (err == 0))
+		FAIL("fdt_check_full() succeeded unexpectedly");
+	else if (!expect_bad && (err != 0))
+		FAIL("fdt_check_full() failed: %s", fdt_strerror(err));
+
+	PASS();
+}

tests/dumptrees.c

@@ -37,6 +37,8 @@ static struct {
 	TREE(test_tree1),
 	TREE(bad_node_char), TREE(bad_node_format), TREE(bad_prop_char),
 	TREE(ovf_size_strings),
+	TREE(truncated_property), TREE(truncated_string),
+	TREE(truncated_memrsv),
 };
 
 #define NUM_TREES	(sizeof(trees) / sizeof(trees[0]))

tests/run_tests.sh

@@ -445,6 +445,15 @@ libfdt_tests () {
     run_wrap_error_test $DTC -I dtb -O dts -o /dev/null ovf_size_strings.dtb
 
     run_test check_header test_tree1.dtb
+
+    # check full tests
+    for good in test_tree1.dtb; do
+	run_test check_full $good
+    done
+    for bad in truncated_property.dtb truncated_string.dtb \
+				      truncated_memrsv.dtb; do
+	run_test check_full -n $bad
+    done
 }
 
 dtc_tests () {