libfdt: Several cleanups to parameter checking

This patch makes a couple of small cleanups to parameter checking of
libfdt functions.

	- In several functions which take a node offset, we use an
idiom involving fdt_next_tag() first to check that we have indeed been
given a node offset.  This patch adds a helper function
_fdt_check_node_offset() to encapsulate this usage of fdt_next_tag().

	- In fdt_rw.c in several places we have the expanded version
of the RW_CHECK_HEADER() macro for no particular reason.  This patch
replaces those instances with an invocation of the macro; that's what
it's for.

	- In fdt_sw.c we rename the check_header_sw() function to
sw_check_header() to match the analgous function in fdt_rw.c, and we
provide an SW_CHECK_HEADER() wrapper macro as RW_CHECK_HEADER()
functions in fdt_rw.c

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 12 insertions, 5 deletions

diff --git a/libfdt/fdt.c b/libfdt/fdt.c
index cfa1989d8..cb08ba0a9 100644
--- a/libfdt/fdt.c
+++ b/libfdt/fdt.c
@@ -133,16 +133,23 @@ uint32_t fdt_next_tag(const void *fdt, int offset, int *nextoffset)
 	return tag;
 }
 
+int _fdt_check_node_offset(const void *fdt, int offset)
+{
+	if ((offset < 0) || (offset % FDT_TAGSIZE)
+	    || (fdt_next_tag(fdt, offset, &offset) != FDT_BEGIN_NODE))
+		return -FDT_ERR_BADOFFSET;
+
+	return offset;
+}
+
 int fdt_next_node(const void *fdt, int offset, int *depth)
 {
 	int nextoffset = 0;
 	uint32_t tag;
 
-	if (offset >= 0) {
-		tag = fdt_next_tag(fdt, offset, &nextoffset);
-		if (tag != FDT_BEGIN_NODE)
-			return -FDT_ERR_BADOFFSET;
-	}
+	if (offset >= 0)
+		if ((nextoffset = _fdt_check_node_offset(fdt, offset)) < 0)
+			return nextoffset;
 
 	do {
 		offset = nextoffset;