[PATCH] tracing: Remove pointer (asterisk) from cpumask_t field

From: Steven Rostedt
Date: Mon Dec 12 2022 - 13:04:07 EST


From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>

To differentiate between long arrays and cpumasks, the __cpumask() field
was created. Part of the TRACE_EVENT() macros test if the type is signed
or not by using the is_signed_type() macro. The __cpumask() field used the
__dynamic_array() helper but because cpumask_t is a structure, it could
not be used in the is_signed_type() macro as that would fail to build, so
instead it passed in the pointer to cpumask_t.

Unfortunately, that creates in the format file:

field:__data_loc cpumask_t *[] mask; offset:36; size:4; signed:0;

Which looks like an array of pointers to cpumask_t and not a cpumask_t
type, which is misleading to user space parsers.

Instead, create another helper called __dynamic_array_sign() that can be
used directly by the __cpumaks() field macro where it passes in an
unsigned value to avoid using the is_signed_type() and have the
__dynamic_array() macro call it by passing it the is_signed_type() on the
type.

This now produces:

field:__data_loc cpumask_t[] mask; offset:36; size:4; signed:0;

Which is the correct type of the field.

Link: https://lore.kernel.org/lkml/6dda5e1d-9416-b55e-88f3-31d148bc925f@xxxxxxx/

Fixes: 8230f27b1ccc ("tracing: Add __cpumask to denote a trace event field that is a cpumask_t")
Reported-by: Douglas Raillard <douglas.raillard@xxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
include/trace/stages/stage4_event_fields.h | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/trace/stages/stage4_event_fields.h b/include/trace/stages/stage4_event_fields.h
index f2990d22313c..9f0049c309f0 100644
--- a/include/trace/stages/stage4_event_fields.h
+++ b/include/trace/stages/stage4_event_fields.h
@@ -28,11 +28,15 @@
.size = sizeof(_type[_len]), .align = ALIGN_STRUCTFIELD(_type), \
.is_signed = is_signed_type(_type), .filter_type = FILTER_OTHER },

-#undef __dynamic_array
-#define __dynamic_array(_type, _item, _len) { \
+#undef __dynamic_array_sign
+#define __dynamic_array_sign(_type, _item, _len, _sign) { \
.type = "__data_loc " #_type "[]", .name = #_item, \
.size = 4, .align = 4, \
- .is_signed = is_signed_type(_type), .filter_type = FILTER_OTHER },
+ .is_signed = _sign, .filter_type = FILTER_OTHER },
+
+#undef __dynamic_array
+#define __dynamic_array(_type, _item, _len) \
+ __dynamic_array_sign(_type, item, len, is_signed_type(_type))

#undef __string
#define __string(item, src) __dynamic_array(char, item, -1)
@@ -47,7 +51,7 @@
#define __bitmask(item, nr_bits) __dynamic_array(unsigned long, item, -1)

#undef __cpumask
-#define __cpumask(item) __dynamic_array(cpumask_t *, item, -1)
+#define __cpumask(item) __dynamic_array_sign(cpumask_t, item, -1, 0)

#undef __sockaddr
#define __sockaddr(field, len) __dynamic_array(u8, field, len)
--
2.35.1