On Tue, Dec 12, 2006 at 02:13:34PM +0100, Bernd Walter wrote: > On Fri, Dec 08, 2006 at 10:36:46AM +0000, Luigi Rizzo wrote: > > luigi 2006-12-08 10:36:45 UTC > > > > FreeBSD src repository > > > > Modified files: > > sys/net if_ethersubr.c > > Log: > > Fix an oscure bug triggered by a recent change in kern_socket.c. > > The symptoms were that outgoing DHCP requests for diskless kernels > > had the IP header corrupt. After long investigations, the source of > > the problem was found in ether_output() - for SIMPLEX interfaces > > and broadcast traffic, a copy of the packet is passed back to the kernel > > through if_simloop(). However if_simloop() modifies the mbuf, while > > the copy obtained through m_copym() is a readonly one. > > > > The bug has been there forever, but it has been triggered only recently > > by a change in sosend_dgram() which passed down mbufs with sufficient > > space to prepend the header. > > > > This fix is trivial - use m_dup() instead of m_copy() to create > > the copy. As an alternative, we could try and modify if_simloop() > > to play safely with readonly mbufs, but i don't think it is worthwhile > > because 1) this is a relatively infrequent code path so we do not need > > to worry too much about performance, and 2) the cost of doing an > > extra m_pullup in if_simloop() is probably the same as doing the > > copy of the cluster, anyways. > > This change produces an alignment panic on arm. > Reverting it gets my system back to live. > > Sending DHCP Discover packet from interface ate0 (00:0e:42:02:00:21) > Fatal kernel mode data abort: 'Alignment Fault 3' > trapframe: 0xc529fd98 > FSR=000000f3, FAR=c08e181e, spsr=20000013 > r0 =c08a2e00, r1 =c529fdec, r2 =00000045, r3 =000005d0 > r4 =c08e180e, r5 =c01eb8a0, r6 =00000014, r7 =00000000 > r8 =00000000, r9 =c01fb9ac, r10=c079acb8, r11=c529fe10 > r12=c08a2e00, ssp=c529fde4, slr=c00d2670, pc =c00e2afc > > [thread pid 11 tid 100004 ] > Stopped at ip_input+0x9c: ldr r1, [r4, #0x010] >
Interesting, before this commit my Gateworks Xscale arm did panic, but this commit fixed the panic. This is what the panic looked like: ##################################################################### Sending DHCP Discover packet from interface npe0 (00:d0:12:02:87:11) Fatal kernel mode prefetch abort at 0x00000080 trapframe: 0xc567ce08, spsr=60000013 r0 =600000d3, r1 =60000013, r2 =000000c0, r3 =80000020 r4 =c0b86c40, r5 =c0b7b7c0, r6 =c567ceac, r7 =c042b634 r8 =00000000, r9 =00000000, r10=c0b85498, r11=c567ce68 r12=c567ce54, ssp=c567ce54, slr=c041fd64, pc =00000080 [thread pid 13 tid 100002 ] Stopped at 0x80: address 0x80 is invalid *** error reading from address 80 *** db> ##################################################################### John -- John Hay -- [EMAIL PROTECTED] / [EMAIL PROTECTED] _______________________________________________ cvs-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/cvs-all To unsubscribe, send any mail to "[EMAIL PROTECTED]"
