[rtems commit] libfdt: fdt_offset_ptr(): Fix comparison warnings

[Sebastian Huber]

Module:    rtems
Branch:    master
Commit:    00125807e2ed75e32d6c655ffae7fe155e471f9b
Changeset: http://git.rtems.org/rtems/commit/?id=00125807e2ed75e32d6c655ffae7fe155e471f9b

Author:    Andre Przywara <andre.przywara at arm.com>
Date:      Mon Sep 21 17:52:50 2020 +0100

libfdt: fdt_offset_ptr(): Fix comparison warnings

With -Wsign-compare, compilers warn about mismatching signedness in
comparisons in fdt_offset_ptr().

This mostly stems from "offset" being passed in as a signed integer,
even though the function would not really tolerate negative values.

Short of changing the prototype, check that offset is not negative, and
use an unsigned type internally.

Signed-off-by: Andre Przywara <andre.przywara at arm.com>
Message-Id: <20200921165303.9115-2-andre.przywara at arm.com>
Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

---

 cpukit/dtc/libfdt/fdt.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/cpukit/dtc/libfdt/fdt.c b/cpukit/dtc/libfdt/fdt.c
index 37b7b93..04e1e06 100644
--- a/cpukit/dtc/libfdt/fdt.c
+++ b/cpukit/dtc/libfdt/fdt.c
@@ -134,16 +134,20 @@ int fdt_check_header(const void *fdt)
 
 const void *fdt_offset_ptr(const void *fdt, int offset, unsigned int len)
 {
-	unsigned absoffset = offset + fdt_off_dt_struct(fdt);
+	unsigned int uoffset = offset;
+	unsigned int absoffset = offset + fdt_off_dt_struct(fdt);
+
+	if (offset < 0)
+		return NULL;
 
 	if (!can_assume(VALID_INPUT))
-		if ((absoffset < offset)
+		if ((absoffset < uoffset)
 		    || ((absoffset + len) < absoffset)
 		    || (absoffset + len) > fdt_totalsize(fdt))
 			return NULL;
 
 	if (can_assume(LATEST) || fdt_version(fdt) >= 0x11)
-		if (((offset + len) < offset)
+		if (((uoffset + len) < uoffset)
 		    || ((offset + len) > fdt_size_dt_struct(fdt)))
 			return NULL;