On Thu, Oct 26, 2023 at 12:40:37PM -0700, Kees Cook wrote:

Solve two ergonomic issues with struct seq_buf;

1) Too much boilerplate is required to initialize:

	struct seq_buf s;
	char buf[32];

	seq_buf_init(s, buf, sizeof(buf));

Instead, we can build this directly on the stack. Provide
DECLARE_SEQ_BUF() macro to do this:

	DECLARE_SEQ_BUF(s, 32);

2) %NUL termination is fragile and requires 2 steps to get a valid
   C String (and is a layering violation exposing the "internals" of
   seq_buf):

	seq_buf_terminate(s);
	do_something(s->buffer);

Instead, we can just return s->buffer direction after terminating it
in refactored seq_buf_terminate(), now known as seq_buf_str():

	do_soemthing(seq_buf_str(s));

...

+#define DECLARE_SEQ_BUF(NAME, SIZE)					\
+	char __ ## NAME ## _buffer[SIZE] = "";				\
+	struct seq_buf NAME = { .buffer = &__ ## NAME ## _buffer,	\
+				.size = SIZE }

Hmm... Wouldn't be more readable to have it as

#define DECLARE_SEQ_BUF(NAME, SIZE)			\
	char __ ## NAME ## _buffer[SIZE] = "";		\
	struct seq_buf NAME = {				\
		.buffer = &__ ## NAME ## _buffer,	\
		.size = SIZE,				\
	}

?

...

+static inline char *seq_buf_str(struct seq_buf *s)
 {
 	if (WARN_ON(s->size == 0))
-		return;
+		return "";

I'm wondering why it's a problem to have an empty string?

 	if (seq_buf_buffer_left(s))
 		s->buffer[s->len] = 0;
 	else
 		s->buffer[s->size - 1] = 0;
+
+	return s->buffer;
 }

-- 
With Best Regards,
Andy Shevchenko