1 files changed, 20 insertions, 0 deletions

diff --git a/include/linux/string.h b/include/linux/string.h
index 27d0482e5e05..7927b875f80c 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -456,4 +456,24 @@ static inline void memcpy_and_pad(void *dest, size_t dest_len,
                 memcpy(dest, src, dest_len);
 }
 
+/**
+ * str_has_prefix - Test if a string has a given prefix
+ * @str: The string to test
+ * @prefix: The string to see if @str starts with
+ *
+ * A common way to test a prefix of a string is to do:
+ *  strncmp(str, prefix, sizeof(prefix) - 1)
+ *
+ * But this can lead to bugs due to typos, or if prefix is a pointer
+ * and not a constant. Instead use str_has_prefix().
+ *
+ * Returns: 0 if @str does not start with @prefix
+         strlen(@prefix) if @str does start with @prefix
+ */
+static __always_inline size_t str_has_prefix(const char *str, const char *prefix)
+{
+        size_t len = strlen(prefix);
+        return strncmp(str, prefix, len) == 0 ? len : 0;
+}
+
 #endif /* _LINUX_STRING_H_ */