lib: Implement strndup()

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
diff --git a/include/linux/string.h b/include/linux/string.h
index 3606620..5d63be4 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -94,6 +94,7 @@
 #ifndef __HAVE_ARCH_STRDUP
 extern char * strdup(const char *);
 #endif
+extern char * strndup(const char *, size_t);
 #ifndef __HAVE_ARCH_STRSWAB
 extern char * strswab(const char *);
 #endif
diff --git a/lib/string.c b/lib/string.c
index af17c16..9b779dd 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -326,6 +326,29 @@
 }
 #endif
 
+char * strndup(const char *s, size_t n)
+{
+	size_t len;
+	char *new;
+
+	if (s == NULL)
+		return NULL;
+
+	len = strlen(s);
+
+	if (n < len)
+		len = n;
+
+	new = malloc(len + 1);
+	if (new == NULL)
+		return NULL;
+
+	strncpy(new, s, len);
+	new[len] = '\0';
+
+	return new;
+}
+
 #ifndef __HAVE_ARCH_STRSPN
 /**
  * strspn - Calculate the length of the initial substring of @s which only