[PATCH 6.7 25/61] tracing/net_sched: Fix tracepoints that save qdisc_dev() as a string

Sasha Levin
2024-03-13T16:33:09Z

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

[ Upstream commit 51270d573a8d9dd5afdc7934de97d66c0e14b5fd ]

I'm updating __assign_str() and will be removing the second parameter. To
make sure that it does not break anything, I make sure that it matches the
__string() field, as that is where the string is actually going to be
saved in. To make sure there's nothing that breaks, I added a WARN_ON() to
make sure that what was used in __string() is the same that is used in
__assign_str().

In doing this change, an error was triggered as __assign_str() now expects
the string passed in to be a char * value. I instead had the following
warning:

include/trace/events/qdisc.h: In function ‘trace_event_raw_event_qdisc_reset’:
include/trace/events/qdisc.h:91:35: error: passing argument 1 of 'strcmp' from incompatible pointer type [-Werror=incompatible-pointer-types]
91 | __assign_str(dev, qdisc_dev(q));

That's because the qdisc_enqueue() and qdisc_reset() pass in qdisc_dev(q)
to __assign_str() and to __string(). But that function returns a pointer
to struct net_device and not a string.

It appears that these events are just saving the pointer as a string and
then reading it as a string as well.

Use qdisc_dev(q)->name to save the device instead.

Fixes: a34dac0b90552 ("net_sched: add tracepoints for qdisc_reset() and qdisc_destroy()")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/trace/events/qdisc.h | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/trace/events/qdisc.h b/include/trace/events/qdisc.h
index a3995925cb057..1f4258308b967 100644
--- a/include/trace/events/qdisc.h
+++ b/include/trace/events/qdisc.h
@@ -81,14 +81,14 @@ TRACE_EVENT(qdisc_reset,
TP_ARGS(q),

TP_STRUCT__entry(
- __string( dev, qdisc_dev(q) )
- __string( kind, q->ops->id )
- __field( u32, parent )
- __field( u32, handle )
+ __string( dev, qdisc_dev(q)->name )
+ __string( kind, q->ops->id )
+ __field( u32, parent )
+ __field( u32, handle )
),

TP_fast_assign(
- __assign_str(dev, qdisc_dev(q));
+ __assign_str(dev, qdisc_dev(q)->name);
__assign_str(kind, q->ops->id);
__entry->parent = q->parent;
__entry->handle = q->handle;
@@ -106,14 +106,14 @@ TRACE_EVENT(qdisc_destroy,
TP_ARGS(q),

TP_STRUCT__entry(
- __string( dev, qdisc_dev(q) )
- __string( kind, q->ops->id )
- __field( u32, parent )
- __field( u32, handle )
+ __string( dev, qdisc_dev(q)->name )
+ __string( kind, q->ops->id )
+ __field( u32, parent )
+ __field( u32, handle )
),

TP_fast_assign(
- __assign_str(dev, qdisc_dev(q));
+ __assign_str(dev, qdisc_dev(q)->name);
__assign_str(kind, q->ops->id);
__entry->parent = q->parent;
__entry->handle = q->handle;
--
2.43.0