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Subject[PATCH net-next] net: skb: fix kfree_skb event output error in perf
Date
From: Menglong Dong <imagedong@tencent.com>

As Eric reported, the 'reason' field is not presented when trace the
kfree_skb event by perf:

$ perf record -e skb:kfree_skb -a sleep 10
$ perf script
ip_defrag 14605 [021] 221.614303: skb:kfree_skb:
skbaddr=0xffff9d2851242700 protocol=34525 location=0xffffffffa39346b1
reason:

The cause seems to be passing kernel address directly to TP_printk(),
which is not right.

Therefore, fix this by adding a '__string' field to the TP_STRUCT of
kfree_skb, which is 'reason_str', and passing it to TP_printk().

(Not sure if we should still keep the 'reason' field in
TP_STRUCT__entry)

Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
include/trace/events/skb.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 45264e4bb254..7235554141c3 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -24,6 +24,7 @@ TRACE_EVENT(kfree_skb,
__field(void *, location)
__field(unsigned short, protocol)
__field(enum skb_drop_reason, reason)
+ __string(reason_str, drop_reasons[reason])
),

TP_fast_assign(
@@ -31,11 +32,12 @@ TRACE_EVENT(kfree_skb,
__entry->location = location;
__entry->protocol = ntohs(skb->protocol);
__entry->reason = reason;
+ __assign_str(reason_str, drop_reasons[reason]);
),

TP_printk("skbaddr=%p protocol=%u location=%p reason: %s",
__entry->skbaddr, __entry->protocol, __entry->location,
- drop_reasons[__entry->reason])
+ __get_str(reason_str))
);

TRACE_EVENT(consume_skb,
--
2.37.2
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