Re: Generic Netlink

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Hi,

Thanks for your answer.
But sorry I'm not capable to debug this problem.
I noticed this problem occurs only if nobody heards the multicast
group when the message was send.
Perhaps, I didn't use the correct flags when I create or send the msg
(in functions genlmsg_put or genlmsg_multicast). I didn't find a good
doc on its flags.

Doude.

On Nov 21, 2007 6:27 PM, Breno Leitao <leitao@xxxxxxxxxxxxxxxxxx> wrote:
> Hello Edouard,
>
> I've tried your example using  the HEAD kernel (2.6.23.8) on a ppc
> machine.
> As you said, it is crashing the operating system, and as I am using
> xmon, it shows the backtrace and the register states during the failure.
> IMHO there is something wrong with the message, which could be
> dereferencing the genl header, causing the following  message "Unable to
> handle kernel paging request for data at address 0x00000008"
> I hope this helps.
>
> ...
> error on genlmsg_multicast -3
> Failure
> Unable to handle kernel paging request for data at address 0x00000008
> Faulting instruction address: 0xc0000000002ebe0c
> cpu 0x1: Vector: 300 (Data Access) at [c000000053f53500]
>     pc: c0000000002ebe0c: .skb_dequeue+0x5c/0x94
>     lr: c0000000002ebdd8: .skb_dequeue+0x28/0x94
>     sp: c000000053f53780
>    msr: 8000000000009032
>    dar: 8
>  dsisr: 42000000
>   current = 0xc000000053a72570
>   paca    = 0xc00000000050d480
>     pid   = 1643, comm = syslogd
> enter ? for help
> [c000000053f53810] c0000000002efc3c .skb_recv_datagram+0xe8/0x2b8
> [c000000053f538f0] c00000000037d8d4 .unix_dgram_recvmsg+0x84/0x348
> [c000000053f539f0] c0000000002e443c .sock_recvmsg+0x114/0x160
> [c000000053f53c00] c0000000002e5c1c .sys_recvfrom+0xec/0x170
> [c000000053f53d90] c000000000309934 .compat_sys_socketcall+0x178/0x214
> [c000000053f53e30] c000000000008534 syscall_exit+0x0/0x40
> --- Exception: c01 (System Call) at 000000001ff500d0
> SP (fff4f600) is in userspace
> 1:mon> t
> [c000000053f53810] c0000000002efc3c .skb_recv_datagram+0xe8/0x2b8
> [c000000053f538f0] c00000000037d8d4 .unix_dgram_recvmsg+0x84/0x348
> [c000000053f539f0] c0000000002e443c .sock_recvmsg+0x114/0x160
> [c000000053f53c00] c0000000002e5c1c .sys_recvfrom+0xec/0x170
> [c000000053f53d90] c000000000309934 .compat_sys_socketcall+0x178/0x214
> [c000000053f53e30] c000000000008534 syscall_exit+0x0/0x40
> --- Exception: c01 (System Call) at 000000001ff500d0
> SP (fff4f600) is in userspace
> 1:mon> r
> R00 = 0000000000000000   R16 = 0000000020008ac8
> R01 = c000000053f53780   R17 = 0000000020008ac0
> R02 = c0000000005e3a60   R18 = 0000000020008aa8
> R03 = 0000000000000001   R19 = 0000000020008a80
> R04 = 0000000000000001   R20 = 0000000020008a7c
> R05 = 0000000000000000   R21 = 0000000020019dfc
> R06 = c000000053f53960   R22 = 0000000020019a84
> R07 = 0000000000000000   R23 = c000000002df8880
> R08 = 0000000000000000   R24 = 0000000000000000
> R09 = 0000000000000000   R25 = c000000053f53960
> R10 = c0000000481e3508   R26 = 7fffffffffffffff
> R11 = 0000000000000000   R27 = c000000053f53c88
> R12 = 000003fe00000000   R28 = c00000005aa15c44
> R13 = c00000000050d480   R29 = c00000005aa15c30
> R14 = 0000000020008b1c   R30 = c0000000005aabf8
> R15 = 0000000020008ae0   R31 = c000000051fbe280
> pc  = c0000000002ebe0c .skb_dequeue+0x5c/0x94
> lr  = c0000000002ebdd8 .skb_dequeue+0x28/0x94
> msr = 8000000000009032   cr  = 24000488
> ctr = c00000000037d850   xer = 0000000020000009   trap =  300
> dar = 0000000000000008   dsisr = 42000000
>
> Regards,
> Breno
> ---
> Breno Leitão
> +55 (16) 8115-3915
> IBM Linux Technology Center
>
>
> On Mon, 2007-11-12 at 17:47 +0100, Edouard Thuleau wrote:
> > Hi,
> >
> > I try to use the generic netlink functionalities in a kernel module.
> >
> > I looked the doc
> > http://www.linux-foundation.org/en/Net:Generic_Netlink_HOWTO and the
> > source code of kernel/taskstats.c in the kernel.
> > I tried to reproduce the example of the doc (look in the attached
> > file) but it doesn't work.
> >
> > I work on a 2.6.23 kernel and on two different architectures, a
> > classic x86 pc and a armv5b board.
> > On the PC the genlmsg_multicast function return an error (-3) and the
> > system crash totally in the next 5 sec (hard reboot).
> > On the arm board, the genlmsg_put function return the NULL value, but
> > the module is unload and the system stay stable.
> >
> > Can you help me ?
> > Doude.
> > -
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