--- xnu/xnu-12377.121.6/iokit/Kernel/IOStringFuncs.c
+++ xnu/xnu-8792.61.2/iokit/Kernel/IOStringFuncs.c
@@ -86,6 +86,7 @@
 unsigned long strtoul(const char *nptr, char **endptr, int base);
 quad_t strtoq(const char *nptr, char **endptr, int base);
 u_quad_t strtouq(const char *nptr, char **endptr, int base);
+char *strncat(char *s1, const char *s2, unsigned long n);
 
 
 typedef int BOOL;
@@ -469,3 +470,29 @@
 
 	return acc;
 }
+
+
+/*
+ *
+ */
+
+char *
+strncat(char *s1, const char *s2, unsigned long n)
+{
+	if (n != 0) {
+		char *d = s1;
+		const char *s = s2;
+
+		while (*d != 0) {
+			d++;
+		}
+		do {
+			if ((*d = *s++) == '\0') {
+				break;
+			}
+			d++;
+		} while (--n != 0);
+		*d = '\0';
+	}
+	return s1;
+}