This is a note to let you know that I've just added the patch titled
tracing: Error if a trace event has an array for a __field()
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-error-if-a-trace-event-has-an-array-for-a-__.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0db7172e7d810534b30b5621bad5aeb0ed766dab
Author: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Date: Thu Mar 9 22:13:02 2023 -0500
tracing: Error if a trace event has an array for a __field()
[ Upstream commit f82e7ca019dfad3b006fd3b772f7ac569672db55 ]
A __field() in the TRACE_EVENT() macro is used to set up the fields of the
trace event data. It is for single storage units (word, char, int,
pointer, etc) and not for complex structures or arrays. Unfortunately,
there's nothing preventing the build from accepting:
__field(int, arr[5]);
from building. It will turn into a array value. This use to work fine, as
the offset and size use to be determined by the macro using the field name,
but things have changed and the offset and size are now determined by the
type. So the above would only be size 4, and the next field will be
located 4 bytes from it (instead of 20).
The proper way to declare static arrays is to use the __array() macro.
Instead of __field(int, arr[5]) it should be __array(int, arr, 5).
Add some macro tricks to the building of a trace event from the
TRACE_EVENT() macro such that __field(int, arr[5]) will fail to build. A
comment by the failure will explain why the build failed.
Link: https://lore.kernel.org/lkml/20230306122549.236561-1-douglas.raillard@xxxxxxx/
Link: https://lore.kernel.org/linux-trace-kernel/20230309221302.642e82d9@xxxxxxxxxxxxxxxxxx
Reported-by: Douglas RAILLARD <douglas.raillard@xxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/trace/stages/stage5_get_offsets.h b/include/trace/stages/stage5_get_offsets.h
index fba4c24ed9e60..def36fbb8c5cd 100644
--- a/include/trace/stages/stage5_get_offsets.h
+++ b/include/trace/stages/stage5_get_offsets.h
@@ -9,17 +9,30 @@
#undef __entry
#define __entry entry
+/*
+ * Fields should never declare an array: i.e. __field(int, arr[5])
+ * If they do, it will cause issues in parsing and possibly corrupt the
+ * events. To prevent that from happening, test the sizeof() a fictitious
+ * type called "struct _test_no_array_##item" which will fail if "item"
+ * contains array elements (like "arr[5]").
+ *
+ * If you hit this, use __array(int, arr, 5) instead.
+ */
#undef __field
-#define __field(type, item)
+#define __field(type, item) \
+ { (void)sizeof(struct _test_no_array_##item *); }
#undef __field_ext
-#define __field_ext(type, item, filter_type)
+#define __field_ext(type, item, filter_type) \
+ { (void)sizeof(struct _test_no_array_##item *); }
#undef __field_struct
-#define __field_struct(type, item)
+#define __field_struct(type, item) \
+ { (void)sizeof(struct _test_no_array_##item *); }
#undef __field_struct_ext
-#define __field_struct_ext(type, item, filter_type)
+#define __field_struct_ext(type, item, filter_type) \
+ { (void)sizeof(struct _test_no_array_##item *); }
#undef __array
#define __array(type, item, len)
