diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index d6ebf0596510..2fb266ea69fa 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -181,7 +181,6 @@ int seq_open_private(struct file *, const struct seq_operations *, int);
 int seq_release_private(struct inode *, struct file *);
 
 #ifdef CONFIG_BINARY_PRINTF
-__printf(2, 0)
 void seq_bprintf(struct seq_file *m, const char *f, const u32 *binary);
 #endif
 
diff --git a/include/linux/string.h b/include/linux/string.h
index 1b564c36d721..b850bd91b3d8 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -336,8 +336,8 @@ int __sysfs_match_string(const char * const *array, size_t n, const char *s);
 #define sysfs_match_string(_a, _s) __sysfs_match_string(_a, ARRAY_SIZE(_a), _s)
 
 #ifdef CONFIG_BINARY_PRINTF
-__printf(3, 0) int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args);
-__printf(3, 0) int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf);
+int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args);
+int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf);
 #endif
 
 extern ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index 32fc12e53675..be5a04367e60 100644
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -1758,9 +1758,12 @@ bool nbcon_alloc(struct console *con)
 	/* Synchronize the kthread start. */
 	lockdep_assert_console_list_lock_held();
 
-	/* The write_thread() callback is mandatory. */
-	if (WARN_ON(!con->write_thread))
+	/* Check for mandatory nbcon callbacks. */
+	if (WARN_ON(!con->write_thread ||
+		    !con->device_lock ||
+		    !con->device_unlock)) {
 		return false;
+	}
 
 	rcuwait_init(&con->rcuwait);
 	init_irq_work(&con->irq_work, nbcon_irq_work);
diff --git a/lib/tests/printf_kunit.c b/lib/tests/printf_kunit.c
index 7617e5b8b02c..f6f21b445ece 100644
--- a/lib/tests/printf_kunit.c
+++ b/lib/tests/printf_kunit.c
@@ -266,15 +266,17 @@ hash_pointer(struct kunit *kunittest)
 	KUNIT_EXPECT_MEMNEQ(kunittest, buf, PTR_STR, PTR_WIDTH);
 }
 
-static void
-test_hashed(struct kunit *kunittest, const char *fmt, const void *p)
-{
-	char buf[PLAIN_BUF_SIZE];
-
-	plain_hash_to_buffer(kunittest, p, buf, PLAIN_BUF_SIZE);
-
-	test(buf, fmt, p);
-}
+/*
+ * This is a macro so that the compiler can compare its arguments to the
+ * __printf() attribute on __test(). This cannot be a function with a __printf()
+ * attribute because GCC requires __printf() functions to be variadic.
+ */
+#define test_hashed(kunittest, fmt, p)						\
+	do {									\
+		char buf[PLAIN_BUF_SIZE];					\
+		plain_hash_to_buffer(kunittest, p, buf, PLAIN_BUF_SIZE);	\
+		test(buf, fmt, p);						\
+	} while (0)
 
 /*
  * NULL pointers aren't hashed.