On Thu, 28 Aug 2008, Vegard Nossum wrote:

quoted text
> On Thu, Aug 28, 2008 at 8:40 PM, Alexey Dobriyan  wrote:

> > On Thu, Aug 28, 2008 at 08:32:23PM +0200, Vegard Nossum wrote:

> >> How do you feel about this patch? It's all about making kmemcheck more

> >> useful... and not much else. Does it have any chance of entering the

> >> kernel along with kmemcheck (when/if that happens)?

> >

> > DEFINE_BITFIELD is horrible.

> >

> >> @@ -285,11 +286,12 @@ struct sk_buff {

> >>               };

> >>       };

> >>       __u32                   priority;

> >> -     __u8                    local_df:1,

> >> +     DEFINE_BITFIELD(__u8,   flags1,

> >> +                             local_df:1,

> >>                               cloned:1,

> >>                               ip_summed:2,

> >>                               nohdr:1,

> >> -                             nfctinfo:3;

> >> +                             nfctinfo:3);

> >>       __u8                    pkt_type:3,

> >>                               fclone:2,

> >>                               ipvs_property:1,

>

> Ok, that's constructive :-P

>

> Can we skip the type and always assume that it should be __u8/uint8_t?

> I read somewhere that bitfields should anyway always be 1 byte wide if

> the bitfield should be "portable". Would it help (to make this less

> horrible) to omit the type declaration and have just the bitfield

> members as arguments to the macro?

Why not do something like this (as suggested by Ingo, I think)? Yeah, the

macro should go into kmemcheck.h but I don't have a tree handy...
		Pekka
Index: linux-2.6/include/linux/bitfield.h

===================================================================

--- /dev/null

+++ linux-2.6/include/linux/bitfield.h

@@ -0,0 +1,10 @@

+#ifndef __LINUX_BITFIELD_H

+#define __LINUX_BITFIELD_H

+

+#ifdef CONFIG_KMEMCHECK

+#define KMEMCHECK_BIT_FIELD(field) do { field = 0; } while (0)

+#else

+#define KMEMCHECK_BIT_FIELD(field) do { } while (0)

+#endif /* CONFIG_KMEMCHECK */

+

+#endif /* __LINUX_BITFIELD_H */
Index: linux-2.6/net/core/skbuff.c

===================================================================

--- linux-2.6.orig/net/core/skbuff.c

+++ linux-2.6/net/core/skbuff.c

@@ -55,6 +55,7 @@

 #include

 #include

 #include

+#include 
 #include

 #include

@@ -209,6 +210,11 @@ struct sk_buff *__alloc_skb(unsigned int

 	skb->data = data;

 	skb_reset_tail_pointer(skb);

 	skb->end = skb->tail + size;

+	KMEMCHECK_BIT_FIELD(skb->local_df);

+	KMEMCHECK_BIT_FIELD(skb->cloned);

+	KMEMCHECK_BIT_FIELD(skb->ip_summed);

+	KMEMCHECK_BIT_FIELD(skb->nohdr);

+	KMEMCHECK_BIT_FIELD(skb->nfctinfo);

 	/* make sure we initialize shinfo sequentially */

 	shinfo = skb_shinfo(skb);

 	atomic_set(&shinfo->dataref, 1);

--

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