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Subject: Re: [PATCH] net: skbuff: fix missing a __noreturn annotation warning
To:     Kuniyuki Iwashima <kuniyu@amazon.com>
CC:     <davem@davemloft.net>, <edumazet@google.com>, <kuba@kernel.org>,
        <linux-kernel@vger.kernel.org>, <netdev@vger.kernel.org>,
        <pabeni@redhat.com>
References: <20230527110409.497408-1-linmiaohe@huawei.com>
 <20230527040038.6783-1-kuniyu@amazon.com>
From:   Miaohe Lin <linmiaohe@huawei.com>
Message-ID: <251633c6-7cbc-a574-5631-9db43a76683b@huawei.com>
Date:   Sat, 27 May 2023 17:22:03 +0800
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On 2023/5/27 12:00, Kuniyuki Iwashima wrote:
> From: Miaohe Lin <linmiaohe@huawei.com>
> Date: Sat, 27 May 2023 19:04:09 +0800
>> Add __noreturn annotation to fix the warning:
>>  net/core/skbuff.o: warning: objtool: skb_push+0x3c: skb_panic() is missing a __noreturn annotation
>>  net/core/skbuff.o: warning: objtool: skb_put+0x4e: skb_panic() is missing a __noreturn annotation
> 
> What arch are you using ?
> 
> IIUC, BUG() should have an annotation for objtool, for
> example, __builtin_unreachable() for x86.
> 
> Maybe the arch is missing such an annotation ?
> 
> Also I'm curious why objtool complains about only skb_push(),
> there should be more non-inline functions that has BUG().

I'm not really sure. I was just compiling the kernel using my old gcc (GCC) 7.3.0 and saw this warning.
Maybe this warning is just false positive.

Thanks.

> 
> Thanks,
> Kuniyuki
> 
> 
>>
>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
>> ---
>>  net/core/skbuff.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
>> index 6724a84ebb09..12b525aa4783 100644
>> --- a/net/core/skbuff.c
>> +++ b/net/core/skbuff.c
>> @@ -181,8 +181,8 @@ EXPORT_SYMBOL_GPL(drop_reasons_unregister_subsys);
>>   *	Keep out of line to prevent kernel bloat.
>>   *	__builtin_return_address is not used because it is not always reliable.
>>   */
>> -static void skb_panic(struct sk_buff *skb, unsigned int sz, void *addr,
>> -		      const char msg[])
>> +static void __noreturn skb_panic(struct sk_buff *skb, unsigned int sz, void *addr,
>> +				 const char msg[])
>>  {
>>  	pr_emerg("%s: text:%px len:%d put:%d head:%px data:%px tail:%#lx end:%#lx dev:%s\n",
>>  		 msg, addr, skb->len, sz, skb->head, skb->data,
>> -- 
>> 2.27.0
> .
>