[for-next][PATCH 4/8] tracing: Remove pointer (asterisk) and brackets from cpumask_t field

Steven Rostedt
2022-12-14T14:02:39Z

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

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.

Douglas Raillard pointed out that the "[]" are also misleading, as
cpumask_t is not an array.

Since cpumask() hasn't been created yet, and the parsers currently fail on
it (but will still produce the raw output), make it be:

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

Which is the correct type of the field.

Then the parsers can be updated to handle this.

Link: https://lore.kernel.org/lkml/6dda5e1d-9416-b55e-88f3-31d148bc925f@arm.com/
Link: https://lore.kernel.org/linux-trace-kernel/20221212193814.0e3f1e43@gandalf.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 8230f27b1ccc ("tracing: Add __cpumask to denote a trace event field that is a cpumask_t")
Reported-by: Douglas Raillard <douglas.raillard@arm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
include/trace/stages/stage4_event_fields.h | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/trace/stages/stage4_event_fields.h b/include/trace/stages/stage4_event_fields.h
index f2990d22313c..affd541fd25e 100644
--- a/include/trace/stages/stage4_event_fields.h
+++ b/include/trace/stages/stage4_event_fields.h
@@ -47,7 +47,10 @@
#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) { \
+ .type = "__data_loc cpumask_t", .name = #item, \
+ .size = 4, .align = 4, \
+ .is_signed = 0, .filter_type = FILTER_OTHER },

#undef __sockaddr
#define __sockaddr(field, len) __dynamic_array(u8, field, len)
@@ -68,7 +71,10 @@
#define __rel_bitmask(item, nr_bits) __rel_dynamic_array(unsigned long, item, -1)

#undef __rel_cpumask
-#define __rel_cpumask(item) __rel_dynamic_array(cpumask_t *, item, -1)
+#define __rel_cpumask(item) { \
+ .type = "__rel_loc cpumask_t", .name = #item, \
+ .size = 4, .align = 4, \
+ .is_signed = 0, .filter_type = FILTER_OTHER },

#undef __rel_sockaddr
#define __rel_sockaddr(field, len) __rel_dynamic_array(u8, field, len)
--
2.35.1