On 2024-03-04 20:41, Steven Rostedt wrote:
On Mon, 4 Mar 2024 20:35:16 -0500
Steven Rostedt <rost...@goodmis.org> wrote:
BUILD_BUG_ON(TRACING_MARK_MAX_SIZE + sizeof(meta data stuff...) >
TRACE_SEQ_SIZE);
That's not the meta size I'm worried about. The sizeof(meta data) is the
raw event binary data, which is not related to the size of the event output.
# cd /sys/kernel/tracing
# echo hello > trace_marker
# cat trace
[..]
<...>-999 [001] ..... 2296.140373: tracing_mark_write: hello
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This is the meta data that is added to trace_seq
That said, the meta data is most likely not going to be more than 128 bytes
(it shouldn't be more than 80).
I could do as you suggest and create a separate TRACE_MARKER_SIZE and just
make sure that it's less than TRACE_SEQ_BUFFER_SIZE (as that's the size of
the content) by 128 bytes.
/* Added meta data should not be more than 128 bytes */
BUILD_BUG_ON((TRACE_MARKER_MAX_SIZE + 128) > TRACE_SEQ_BUFFER_SIZE);
Bonus points if you add
#define TRACE_OUTPUT_META_DATA_MAX_LEN 80
and a runtime check in the code generating this header.
This would avoid adding an unchecked upper limit.
Thanks,
Mathieu
-- Steve
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
