Re: [PATCH v3 02/15] libfdt: Don't assume the root node is available at offset 0

@@ -228,16 +228,24 @@ uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
 	return tag;
 }
 
-int fdt_check_node_offset_(const void *fdt, int offset)
+int fdt_check_node_offset_(const void *fdt, int *offset)
 {
+	int nextoffset;
+
 	if (!can_assume(VALID_INPUT)
-	    && ((offset < 0) || (offset % FDT_TAGSIZE)))
+	    && ((*offset < 0) || (*offset % FDT_TAGSIZE)))
 		return -FDT_ERR_BADOFFSET;
 
-	if (fdt_next_tag(fdt, offset, &offset) != FDT_BEGIN_NODE)
+	if (*offset == 0) {
+		*offset = fdt_root_offset(fdt);
+		if (*offset < 0)
+			return *offset;
+	}
+
+	if (fdt_next_tag(fdt, *offset, &nextoffset) != FDT_BEGIN_NODE)
 		return -FDT_ERR_BADOFFSET;
 
-	return offset;
+	return nextoffset;
 }
 
 int fdt_check_prop_offset_(const void *fdt, int offset)

@@ -252,13 +260,38 @@ int fdt_check_prop_offset_(const void *fdt, int offset)
 	return offset;
 }
 
+int fdt_root_offset(const void *fdt)
+{
+	int nextoffset = 0;
+	int offset;
+	uint32_t tag;
+
+	do {
+		offset = nextoffset;
+		tag = fdt_next_tag(fdt, offset, &nextoffset);
+		switch (tag) {
+		case FDT_END_NODE:
+		case FDT_PROP:
+			return -FDT_ERR_BADSTRUCTURE;
+
+		case FDT_BEGIN_NODE:
+			return offset;
+
+		default:
+			break;
+		}
+	} while (tag != FDT_END);
+
+	return (nextoffset < 0) ? nextoffset : -FDT_ERR_NOTFOUND;
+}
+
 int fdt_next_node(const void *fdt, int offset, int *depth)
 {
 	int nextoffset = 0;
 	uint32_t tag;
 
 	if (offset >= 0)
-		if ((nextoffset = fdt_check_node_offset_(fdt, offset)) < 0)
+		if ((nextoffset = fdt_check_node_offset_(fdt, &offset)) < 0)
 			return nextoffset;
 
 	do {

@@ -281,7 +281,7 @@ int fdt_path_offset_namelen(const void *fdt, const char *path, int namelen)
 		while (*p == '/') {
 			p++;
 			if (p == end)
-				return offset;
+				goto terminate;
 		}
 		q = memchr(p, '/', end - p);
 		if (! q)

@@ -294,7 +294,13 @@ int fdt_path_offset_namelen(const void *fdt, const char *path, int namelen)
 		p = q;
 	}
 
-	return offset;
+terminate:
+        /*
+         * Avoid returning offset 0 or the real root offset.
+         * Be sure to return one and only one offset for the root node, its
+         * real offset.
+         */
+	return offset ? offset : fdt_root_offset(fdt);
 }
 
 int fdt_path_offset(const void *fdt, const char *path)

@@ -304,14 +310,17 @@ int fdt_path_offset(const void *fdt, const char *path)
 
 const char *fdt_get_name(const void *fdt, int nodeoffset, int *len)
 {
-	const struct fdt_node_header *nh = fdt_offset_ptr_(fdt, nodeoffset);
+	const struct fdt_node_header *nh;
 	const char *nameptr;
 	int err;
 
-	if (!can_assume(VALID_DTB) && (((err = fdt_ro_probe_(fdt)) < 0)
-	    || ((err = fdt_check_node_offset_(fdt, nodeoffset)) < 0)))
-			goto fail;
+	if (!can_assume(VALID_DTB) && (err = fdt_ro_probe_(fdt)) < 0)
+		goto fail;
+
+	if ((err = fdt_check_node_offset_(fdt, &nodeoffset)) < 0)
+		goto fail;
 
+	nh = fdt_offset_ptr_(fdt, nodeoffset);
 	nameptr = nh->name;
 
 	if (!can_assume(LATEST) && fdt_version(fdt) < 0x10) {

@@ -344,7 +353,7 @@ int fdt_first_property_offset(const void *fdt, int nodeoffset)
 {
 	int offset;
 
-	if ((offset = fdt_check_node_offset_(fdt, nodeoffset)) < 0)
+	if ((offset = fdt_check_node_offset_(fdt, &nodeoffset)) < 0)
 		return offset;
 
 	return nextprop_(fdt, offset);

@@ -574,6 +583,7 @@ int fdt_get_path(const void *fdt, int nodeoffset, char *buf, int buflen)
 {
 	int pdepth = 0, p = 0;
 	int offset, depth, namelen;
+	int root_offset;
 	const char *name;
 
 	FDT_RO_PROBE(fdt);

@@ -581,7 +591,14 @@ int fdt_get_path(const void *fdt, int nodeoffset, char *buf, int buflen)
 	if (buflen < 2)
 		return -FDT_ERR_NOSPACE;
 
-	for (offset = 0, depth = 0;
+	root_offset = fdt_root_offset(fdt);
+	if (root_offset < 0)
+		return root_offset;
+
+	if (!nodeoffset)
+		nodeoffset = root_offset;
+
+	for (offset = root_offset, depth = 0;
 	     (offset >= 0) && (offset <= nodeoffset);
 	     offset = fdt_next_node(fdt, offset, &depth)) {
 		while (pdepth > depth) {

@@ -627,13 +644,21 @@ int fdt_supernode_atdepth_offset(const void *fdt, int nodeoffset,
 {
 	int offset, depth;
 	int supernodeoffset = -FDT_ERR_INTERNAL;
+	int root_offset;
 
 	FDT_RO_PROBE(fdt);
 
 	if (supernodedepth < 0)
 		return -FDT_ERR_NOTFOUND;
 
-	for (offset = 0, depth = 0;
+	root_offset = fdt_root_offset(fdt);
+	if (root_offset < 0)
+		return root_offset;
+
+	if (!nodeoffset)
+		nodeoffset = root_offset;
+
+	for (offset = root_offset, depth = 0;
 	     (offset >= 0) && (offset <= nodeoffset);
 	     offset = fdt_next_node(fdt, offset, &depth)) {
 		if (depth == supernodedepth)

@@ -663,12 +688,15 @@ int fdt_supernode_atdepth_offset(const void *fdt, int nodeoffset,
 int fdt_node_depth(const void *fdt, int nodeoffset)
 {
 	int nodedepth;
-	int err;
+	int offset;
+
+	offset = fdt_supernode_atdepth_offset(fdt, nodeoffset, 0, &nodedepth);
+	if (offset < 0)
+		return offset;
+
+	if (!can_assume(LIBFDT_FLAWLESS) && offset != fdt_root_offset(fdt))
+		return -FDT_ERR_INTERNAL;
 
-	err = fdt_supernode_atdepth_offset(fdt, nodeoffset, 0, &nodedepth);
-	if (err)
-		return (can_assume(LIBFDT_FLAWLESS) || err < 0) ? err :
-			-FDT_ERR_INTERNAL;
 	return nodedepth;
 }
 

@@ -226,7 +226,7 @@ static int fdt_add_property_(void *fdt, int nodeoffset, const char *name,
 	int err;
 	int allocated;
 
-	if ((nextoffset = fdt_check_node_offset_(fdt, nodeoffset)) < 0)
+	if ((nextoffset = fdt_check_node_offset_(fdt, &nodeoffset)) < 0)
 		return nextoffset;
 
 	namestroff = fdt_find_add_string_(fdt, name, namelen, &allocated);

@@ -377,6 +377,12 @@ int fdt_add_subnode_namelen(void *fdt, int parentoffset,
 
 	FDT_RW_PROBE(fdt);
 
+	if (!parentoffset) {
+		parentoffset = fdt_root_offset(fdt);
+		if (parentoffset < 0)
+			return parentoffset;
+	}
+
 	offset = fdt_subnode_offset_namelen(fdt, parentoffset, name, namelen);
 	if (offset >= 0)
 		return -FDT_ERR_EXISTS;

@@ -503,6 +503,19 @@ int fdt_num_mem_rsv(const void *fdt);
  */
 int fdt_get_mem_rsv(const void *fdt, int n, uint64_t *address, uint64_t *size);
 
+/**
+ * fdt_root_offset - Get the offset of the root node
+ * @fdt: pointer to the device tree blob
+ *
+ * The root node can be located after the offset 0. Indeed FDT_NOP tags can be
+ * present at offset 0. fdt_root_offset() takes care of those possible FDT_NOP
+ * tags.
+ *
+ * returns: offset of the root node or negative libfdt error value otherwise
+ */
+int fdt_root_offset(const void *fdt);
+
+
 /**
  * fdt_subnode_offset_namelen - find a subnode based on substring
  * @fdt: pointer to the device tree blob

@@ -1025,7 +1038,7 @@ int fdt_get_path(const void *fdt, int nodeoffset, char *buf, int buflen);
  * at a specific depth from the root (where the root itself has depth
  * 0, its immediate subnodes depth 1 and so forth).  So
  *	fdt_supernode_atdepth_offset(fdt, nodeoffset, 0, NULL);
- * will always return 0, the offset of the root node.  If the node at
+ * will always return the offset of the root node.  If the node at
  * nodeoffset has depth D, then:
  *	fdt_supernode_atdepth_offset(fdt, nodeoffset, D, NULL);
  * will return nodeoffset itself.

@@ -20,7 +20,7 @@ int32_t fdt_ro_probe_(const void *fdt);
 		}							\
 	}
 
-int fdt_check_node_offset_(const void *fdt, int offset);
+int fdt_check_node_offset_(const void *fdt, int *offset);
 int fdt_check_prop_offset_(const void *fdt, int offset);
 
 const char *fdt_find_string_len_(const char *strtab, int tabsize, const char *s,

@@ -7,6 +7,7 @@ LIBFDT_1.2 {
 		fdt_string;
 		fdt_num_mem_rsv;
 		fdt_get_mem_rsv;
+		fdt_root_offset;
 		fdt_subnode_offset_namelen;
 		fdt_subnode_offset;
 		fdt_path_offset_namelen;
--- 8< ---