Subject: objtool: skb_push.cold()+0x15: unreachable instruction

From: Jeffrin Jose <[email-masked]>
Date: Sun, 10 Nov 2019 04:35:20 +0530

hello,

i got a warning during kernel compilation.

net/core/skbuff.o: warning: objtool: skb_push.cold()+0x15: unreachable instruction

related clips...

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(gdb) l skb_push.cold
1880	void *skb_push(struct sk_buff *skb, unsigned int len)
1881	{
1882		skb->data -= len;
1883		skb->len  += len;
1884		if (unlikely(skb->data < skb->head))
1885			skb_under_panic(skb, len, __builtin_return_address(0));
1886		return skb->data;
1887	}
1888	EXPORT_SYMBOL(skb_push);
1889	
(gdb) l *0xffffffff815ffc8e
0xffffffff815ffc8e is in skb_push (net/core/skbuff.c:1885).
1880	void *skb_push(struct sk_buff *skb, unsigned int len)
1881	{
1882		skb->data -= len;
1883		skb->len  += len;
1884		if (unlikely(skb->data < skb->head))
1885			skb_under_panic(skb, len, __builtin_return_address(0));
1886		return skb->data;
1887	}
1888	EXPORT_SYMBOL(skb_push);
1889	
(gdb)

------------------x-----------------------x------------------------------------

$uname -a
Linux debian 5.4.0-rc1+ #1 SMP Sat Nov 9 21:29:48 IST 2019 x86_64 GNU/Linux
$

this kernel is from linux-kselftest tree

---------------------------x-------------x------------------------------

$gcc --version
gcc (Debian 9.2.1-14) 9.2.1 20191025
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

-------------------------x-------------------x-----------------------------

Linux debian 5.4.0-rc1+ #1 SMP Sat Nov 9 21:29:48 IST 2019 x86_64 GNU/Linux

GNU Make            	4.2.1
Binutils            	2.33.1
Util-linux          	2.33.1
Mount               	2.33.1
Linux C Library     	2.29
Dynamic linker (ldd)	2.29
Procps              	3.3.15
Kbd                 	2.0.4
Console-tools       	2.0.4
Sh-utils            	8.30
Udev                	241

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--
software engineer
rajagiri school of engineering and technology