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authorMenglong Dong <imagedong@tencent.com>2022-08-21 13:18:58 +0800
committerDavid S. Miller <davem@davemloft.net>2022-08-24 09:47:51 +0100
commitc205cc7534a97f2d6fbd2a23a94ed7c036c6e2aa (patch)
tree3d3bef30360bef6fa79771d761fa2b1a21803eed
parentfa2bc96259098a3bc1f32a10bfe1139c0f742256 (diff)
net: skb: prevent the split of kfree_skb_reason() by gcc
Sometimes, gcc will optimize the function by spliting it to two or more functions. In this case, kfree_skb_reason() is splited to kfree_skb_reason and kfree_skb_reason.part.0. However, the function/tracepoint trace_kfree_skb() in it needs the return address of kfree_skb_reason(). This split makes the call chains becomes: kfree_skb_reason() -> kfree_skb_reason.part.0 -> trace_kfree_skb() which makes the return address that passed to trace_kfree_skb() be kfree_skb(). Therefore, introduce '__fix_address', which is the combination of '__noclone' and 'noinline', and apply it to kfree_skb_reason() to prevent to from being splited or made inline. (Is it better to simply apply '__noclone oninline' to kfree_skb_reason? I'm thinking maybe other functions have the same problems) Meanwhile, wrap 'skb_unref()' with 'unlikely()', as the compiler thinks it is likely return true and splits kfree_skb_reason(). Signed-off-by: Menglong Dong <imagedong@tencent.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/linux/compiler_attributes.h7
-rw-r--r--include/linux/skbuff.h3
-rw-r--r--net/core/skbuff.c5
3 files changed, 12 insertions, 3 deletions
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index 445e80517cab..fc93c9488c76 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -371,4 +371,11 @@
*/
#define __weak __attribute__((__weak__))
+/*
+ * Used by functions that use '__builtin_return_address'. These function
+ * don't want to be splited or made inline, which can make
+ * the '__builtin_return_address' get unexpected address.
+ */
+#define __fix_address noinline __noclone
+
#endif /* __LINUX_COMPILER_ATTRIBUTES_H */
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index ca8afa382bf2..b51d07a727c9 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1195,7 +1195,8 @@ static inline bool skb_unref(struct sk_buff *skb)
return true;
}
-void kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason);
+void __fix_address
+kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason);
/**
* kfree_skb - free an sk_buff with 'NOT_SPECIFIED' reason
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 974bbbbe7138..35d9d5958dc6 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -777,9 +777,10 @@ EXPORT_SYMBOL(__kfree_skb);
* hit zero. Meanwhile, pass the drop reason to 'kfree_skb'
* tracepoint.
*/
-void kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)
+void __fix_address
+kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)
{
- if (!skb_unref(skb))
+ if (unlikely(!skb_unref(skb)))
return;
DEBUG_NET_WARN_ON_ONCE(reason <= 0 || reason >= SKB_DROP_REASON_MAX);