netdev - Re: sparse checking prevented by "net: fix kmemcheck annotations"

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Date:	Mon, 01 Mar 2010 14:09:26 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
Cc:	linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: sparse checking prevented by "net: fix kmemcheck annotations"

Le lundi 01 mars 2010 à 13:09 +0100, Stefan Richter a écrit :
> Hi all,
> 
> the post 2.6.32-rc5, pre 2.6.32-rc6 commit 14d18a81 causes a serious
> regression for sparse checks:  make C=1 CF="-D__CHECK_ENDIAN__" now
> causes sparse to log
> 
>     include/linux/skbuff.h:357:41: error: invalid bitfield specifier for
>     type restricted __be16.
> 
> 
> I reported this already shortly after this hit the mainline.  But back
> then I didn't notice that this sparse error causes sparse to remain
> silent on all subsequent warnings in a file!
> 
> We need to either change sparse to accept this bogus bit field that
> occurs in skbuff.h (__be16 protocol:16;), silently or with a warning, or
> revert this kmemcheck annotation.
> 
> ("We" == preferably Eric :-)
> 
> skbuff.h is included by lots of drivers, even ones that are not even
> networking drivers, notably DVB drivers.  None of these drivers can be
> checked with sparse's __CHECK_ENDIAN__ at the moment.

Hi Stefan

I believe kmemcheck side effects were solved by commit e992cd9b72a18122
(kmemcheck: make bitfield annotations truly no-ops when disabled),
so there is no problem to partially revert the patch and fix this
problem.

Thanks !

[PATCH] net: fix protocol sk_buff field

Commit e992cd9b72a18 (kmemcheck: make bitfield annotations truly no-ops
when disabled) allows us to revert a workaround we did in the past to
not add holes in sk_buff structure.

This patch partially reverts commit 14d18a81b5171
(net: fix kmemcheck annotations) so that sparse doesnt complain:

include/linux/skbuff.h:357:41: error: invalid bitfield specifier for
type restricted __be16.

Reported-by: Stefan Richter <stefanr@...6.in-berlin.de>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index ae836fd..b40f56b 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -354,8 +354,8 @@ struct sk_buff {
 				ipvs_property:1,
 				peeked:1,
 				nf_trace:1;
-	__be16			protocol:16;
 	kmemcheck_bitfield_end(flags1);
+	__be16			protocol;
 
 	void			(*destructor)(struct sk_buff *skb);
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)


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