net: fix call location in kfree_skb_list_reason

The SKB drop reason uses __builtin_return_address(0) to give the call
"location" to trace_kfree_skb() tracepoint skb:kfree_skb.

To keep this stable for compilers kfree_skb_reason() is annotated with
__fix_address (noinline __noclone) as fixed in commit c205cc7534a9
("net: skb: prevent the split of kfree_skb_reason() by gcc").

The function kfree_skb_list_reason() invoke kfree_skb_reason(), which
cause the __builtin_return_address(0) "location" to report the
unexpected address of kfree_skb_list_reason.

Example output from 'perf script':
 kpktgend_0  1337 [000]    81.002597: skb:kfree_skb: skbaddr=0xffff888144824700 protocol=2048 location=kfree_skb_list_reason+0x1e reason: QDISC_DROP

Patch creates an __always_inline __kfree_skb_reason() helper call that
is called from both kfree_skb_list() and kfree_skb_list_reason().
Suggestions for solutions that shares code better are welcome.

As preparation for next patch move __kfree_skb() invocation out of
this helper function.

Reviewed-by: Saeed Mahameed <saeed@kernel.org>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 3a10387..ca2b4d6 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -930,6 +930,21 @@ void __kfree_skb(struct sk_buff *skb)
 }
 EXPORT_SYMBOL(__kfree_skb);
 
+static __always_inline
+bool __kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)
+{
+       if (unlikely(!skb_unref(skb)))
+               return false;
+
+       DEBUG_NET_WARN_ON_ONCE(reason <= 0 || reason >= SKB_DROP_REASON_MAX);
+
+       if (reason == SKB_CONSUMED)
+               trace_consume_skb(skb);
+       else
+               trace_kfree_skb(skb, __builtin_return_address(0), reason);
+       return true;
+}
+
 /**
  *     kfree_skb_reason - free an sk_buff with special reason
  *     @skb: buffer to free
@@ -942,26 +957,19 @@ EXPORT_SYMBOL(__kfree_skb);
 void __fix_address
 kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)
 {
-       if (unlikely(!skb_unref(skb)))
-               return;
-
-       DEBUG_NET_WARN_ON_ONCE(reason <= 0 || reason >= SKB_DROP_REASON_MAX);
-
-       if (reason == SKB_CONSUMED)
-               trace_consume_skb(skb);
-       else
-               trace_kfree_skb(skb, __builtin_return_address(0), reason);
-       __kfree_skb(skb);
+       if (__kfree_skb_reason(skb, reason))
+               __kfree_skb(skb);
 }
 EXPORT_SYMBOL(kfree_skb_reason);
 
-void kfree_skb_list_reason(struct sk_buff *segs,
-                          enum skb_drop_reason reason)
+void __fix_address
+kfree_skb_list_reason(struct sk_buff *segs, enum skb_drop_reason reason)
 {
        while (segs) {
                struct sk_buff *next = segs->next;
 
-               kfree_skb_reason(segs, reason);
+               if (__kfree_skb_reason(segs, reason))
+                       __kfree_skb(segs);
                segs = next;
        }
 }