tracing: Have trace_marker break up by lines by size of trace_seq

If a trace_marker write is bigger than what trace_seq can hold, then it
will print "LINE TOO BIG" message and not what was written.

Instead, check if the write is bigger than the trace_seq and break it
up by that size.

Ideally, we could make the trace_seq dynamic that could hold this. But
that's for another time.

Link: https://lore.kernel.org/linux-trace-kernel/20231212190422.1eaf224f@gandalf.local.home
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 0be30cc..9cf5838 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -7304,6 +7304,11 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
        if (cnt < FAULTED_SIZE)
                size += FAULTED_SIZE - cnt;
 
+       if (size > TRACE_SEQ_BUFFER_SIZE) {
+               cnt -= size - TRACE_SEQ_BUFFER_SIZE;
+               goto again;
+       }
+
        buffer = tr->array_buffer.buffer;
        event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
                                            tracing_gen_ctx());