Fix widespread incorrect use of strneq(), replace with new strprefixeq()

Every remaining usage of strneq() is, in fact, incorrect.  They're trying
to check that the first n characters of one string exactly match another
string.  But, they fall into the classic trap of strncmp() on which
strneq() is based.  If n is less than the length of the second string, they
only check that the first string matches the start of the second, not the
whole of it.

To fix this, remove strneq() and replace it with a strprefixeq() function
which does what we want here.

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

checks.c

@@ -696,8 +696,8 @@ static void check_pci_bridge(struct check *c, struct dt_info *dti, struct node *
 
 	node->bus = &pci_bus;
 
-	if (!strneq(node->name, "pci", node->basenamelen) &&
+	if (!strprefixeq(node->name, node->basenamelen, "pci") &&
-	    !strneq(node->name, "pcie", node->basenamelen))
+	    !strprefixeq(node->name, node->basenamelen, "pcie"))
 		FAIL(c, dti, "Node %s node name is not \"pci\" or \"pcie\"",
 			     node->fullpath);
 
@@ -828,7 +828,7 @@ static bool node_is_compatible(struct node *node, const char *compat)
 
 	for (str = prop->val.val, end = str + prop->val.len; str < end;
 	     str += strnlen(str, end - str) + 1) {
-		if (strneq(str, compat, end - str))
+		if (strprefixeq(str, end - str, compat))
 			return true;
 	}
 	return false;

dtc.h

@@ -67,8 +67,8 @@ typedef uint32_t cell_t;
 
 
 #define streq(a, b)	(strcmp((a), (b)) == 0)
-#define strneq(a, b, n)	(strncmp((a), (b), (n)) == 0)
 #define strstarts(s, prefix)	(strncmp((s), (prefix), strlen(prefix)) == 0)
+#define strprefixeq(a, n, b)	(strlen(b) == (n) && (memcmp(a, b, n) == 0))
 
 #define ALIGN(x, a)	(((x) + (a) - 1) & ~((a) - 1))
 

livetree.c

@@ -507,7 +507,7 @@ struct node *get_node_by_path(struct node *tree, const char *path)
 
 	for_each_child(tree, child) {
 		if (p && (strlen(child->name) == p-path) &&
-				strneq(path, child->name, p-path))
+		    strprefixeq(path, p - path, child->name))
 			return get_node_by_path(child, p+1);
 		else if (!p && streq(path, child->name))
 			return child;