diff --git a/lib/libfdt/fdt_ro.c b/lib/libfdt/fdt_ro.c
index e03570a..91cc6fe 100644
--- a/lib/libfdt/fdt_ro.c
+++ b/lib/libfdt/fdt_ro.c
@@ -53,7 +53,7 @@
 
 	err = -FDT_ERR_BADOFFSET;
 	absoffset = stroffset + fdt_off_dt_strings(fdt);
-	if (absoffset >= totalsize)
+	if (absoffset >= (unsigned)totalsize)
 		goto fail;
 	len = totalsize - absoffset;
 
@@ -61,17 +61,19 @@
 		if (stroffset < 0)
 			goto fail;
 		if (can_assume(LATEST) || fdt_version(fdt) >= 17) {
-			if (stroffset >= fdt_size_dt_strings(fdt))
+			if ((unsigned)stroffset >= fdt_size_dt_strings(fdt))
 				goto fail;
 			if ((fdt_size_dt_strings(fdt) - stroffset) < len)
 				len = fdt_size_dt_strings(fdt) - stroffset;
 		}
 	} else if (fdt_magic(fdt) == FDT_SW_MAGIC) {
-		if ((stroffset >= 0)
-		    || (stroffset < -fdt_size_dt_strings(fdt)))
+		unsigned int sw_stroffset = -stroffset;
+
+		if ((stroffset >= 0) ||
+		    (sw_stroffset > fdt_size_dt_strings(fdt)))
 			goto fail;
-		if ((-stroffset) < len)
-			len = -stroffset;
+		if (sw_stroffset < len)
+			len = sw_stroffset;
 	} else {
 		err = -FDT_ERR_INTERNAL;
 		goto fail;
@@ -157,8 +159,8 @@
 
 static const struct fdt_reserve_entry *fdt_mem_rsv(const void *fdt, int n)
 {
-	int offset = n * sizeof(struct fdt_reserve_entry);
-	int absoffset = fdt_off_mem_rsvmap(fdt) + offset;
+	unsigned int offset = n * sizeof(struct fdt_reserve_entry);
+	unsigned int absoffset = fdt_off_mem_rsvmap(fdt) + offset;
 
 	if (!can_assume(VALID_INPUT)) {
 		if (absoffset < fdt_off_mem_rsvmap(fdt))
@@ -680,7 +682,7 @@
 {
 	int offset;
 
-	if ((phandle == 0) || (phandle == -1))
+	if ((phandle == 0) || (phandle == ~0U))
 		return -FDT_ERR_BADPHANDLE;
 
 	FDT_RO_PROBE(fdt);