From c205cc7534a97f2d6fbd2a23a94ed7c036c6e2aa Mon Sep 17 00:00:00 2001 From: Menglong Dong Date: Sun, 21 Aug 2022 13:18:58 +0800 Subject: 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 Signed-off-by: David S. Miller --- include/linux/compiler_attributes.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include/linux/compiler_attributes.h') 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 */ -- cgit v1.2.3-70-g09d2