Lawrence Stewart <[email protected]> wrote: > On 06/20/10 22:28, Fabian Keil wrote: > > Lawrence Stewart<[email protected]> wrote: > > > >> On 06/20/10 21:15, Fabian Keil wrote: > >>> Lawrence Stewart<[email protected]> wrote: > >>> > >>>> On 06/20/10 03:58, Fabian Keil wrote: > >>>>> Lawrence Stewart<[email protected]> wrote: > >>>>> > >>>>>> On 06/13/10 18:12, Lawrence Stewart wrote: > >>>>> > >>>>>>> The time has come to solicit some external testing for my SIFTR tool. > >>>>>>> I'm hoping to commit it within a week or so unless problems are > >>>>>>> discovered. > >>>>> > >>>>>>> I'm interested in all feedback and reports of success/failure, along > >>>>>>> with details of the architecture tested and number of CPUs if you > >>>>>>> would > >>>>>>> be so kind. > >>>>> > >>>>> I got the following hand-transcribed panic maybe a second after > >>>>> sysctl net.inet.siftr.enabled=1 > >>>>> > >>>>> Fatal trap 12: page fault while in kernel mode > >>>>> cpuid = 1; apic id = 01 > >>>>> [...] > >>>>> current process = 12 (swi4: clock) > >>>>> [ thread pid 12 tid 100006 ] > >>>>> Stopped at siftr_chkpkt+0xd0: addq $0x1,0x8(%r14) > >>>>> db> where > >>>>> Tracing pid 12 tid 100006 td 0xffffff00034037e0 > >>>>> siftr_chkpt() at siftr_chkpkt+0xd0 > >>>>> pfil_run_hooks() at pfil_run_hooks+0xb4 > >>>>> ip_output() at ip_output+0x382 > >>>>> tcp_output() tcp_output+0xa41 > >>>>> tcp_timer_rexmt() at tcp_timer_rexmt+0x251 > >>>>> softclock() at softclock+0x291 > >>>>> intr_event_execute_handlers() at intr_event_execute_handlers+0x66 > >>>>> ithread_loop at ithread_loop+0x8e > >>>>> fork_exit() at fork_exit+0x112 > >>>>> fork_trampoline() at fork_trampoline+0xe > >>>>> --- trap 0, rip = 0, rsp = 0xffffff800003ad30, rbp = 0 --- > >>>> > >>>> So I've tracked down the line of code where the page fault is occurring: > >>>> > >>>> if (dir == PFIL_IN) > >>>> ss->n_in++; > >>>> else > >>>> ss->n_out++; > >>>> > >>>> ss is a DPCPU (dynamic per-cpu) variable used to keep a set of stats > >>>> per-cpu and is initialised at the start of the function like so: > >>>> > >>>> ss = DPCPU_PTR(ss); > >>>> > >>>> So for ss to be NULL, that implies DPCPU_PTR() is returning NULL on your > >>>> machine. I know very little about the inner workings of the DPCPU_* > >>>> macros, but I'm pretty sure the way I use them in SIFTR is correct or at > >>>> least as intended. > >>> > >>> siftr_chkpkt() passes ss to siftr_chkreinject() before dereferencing > >>> it itself. I think if ss was NULL, the panic should already occur in > >>> siftr_chkreinject(). > >> > >> Yes but siftr_chkreinject() only dereferences ss in the exceptional case > >> of a malloc failure or duplicate pkt. It's unlikely either case happens > >> for you and so wouldn't trigger the panic. > >> > >>> To be sure I added: > >>> > >>> diff --git a/sys/netinet/siftr.c b/sys/netinet/siftr.c > >>> index 8bc3498..b9fdfe4 100644 > >>> --- a/sys/netinet/siftr.c > >>> +++ b/sys/netinet/siftr.c > >>> @@ -788,6 +788,16 @@ siftr_chkpkt(void *arg, struct mbuf **m, struct > >>> ifnet *ifp, int dir, > >>> if (siftr_chkreinject(*m, dir, ss)) > >>> goto ret; > >>> > >>> + if (ss == NULL) { > >>> + printf("ss is NULL"); > >>> + ss = DPCPU_PTR(ss); > >>> + if (ss == NULL) { > >>> + printf("ss is still NULL"); > >>> + goto ret; > >>> + } > >>> + } > >>> + > >>> + > >>> if (dir == PFIL_IN) > >>> ss->n_in++; > >>> else > >>> > >>> which doesn't seem to affect the problem. > >> > >> As in it still panics and the "ss is NULL" message is not printed? I > >> would have expected to at least see "ss is NULL" printed if my > >> hypothesis was correct... hmm. > > > > Yes, it still panics, but no message is printed. > > It was just pointed out to me that ss doesn't have to be NULL in order > to cause the page fault (duh). It could also just be a garbage ptr which > is why your print statement isn't firing. > > Can you trigger the panic again and look for some information along the > lines of "fault virtual address = ..." as part of the panic info. > Knowing the faulting address would be useful and may help further diagnosis.
Fatal trap 12: page fault while in kernel mode
cpuid = 1; apic id = 01
fault virtual address = 0xffffff7f808f9de8
fault code = supervisor write data, page not present
instruction pointer = 0x20:0xffffffff8241f800
stack pointer = 0x28:0xffffff800003a7d0
frame pointer = 0x28:0xffffff800003a840
code segment = base 0x0, limit 0xfffff, type 0x1b
= DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags = interrupt enabled, resume, IOPL = 0
current process = 12 (swi4: clock)
[ thread pid 12 tid 100006 ]
Stopped at siftr_chkpkt+0xd0: addq $0x1,0x8(%r14)
db> where
Tracing pid 12 tid 100006 td 0xffffff00034037e0
siftr_chkpt() at siftr_chkpkt+0xd0
pfil_run_hooks() at pfil_run_hooks+0xb4
ip_output() at ip_output+0x382
tcp_output() tcp_output+0xa41
tcp_timer_rexmt() at tcp_timer_rexmt+0x251
softclock() at softclock+0x291
intr_event_execute_handlers() at intr_event_execute_handlers+0x66
ithread_loop at ithread_loop+0x8e
fork_exit() at fork_exit+0x112
fork_trampoline() at fork_trampoline+0xe
--- trap 0, rip = 0, rsp = 0xffffff800003ad30, rbp = 0 ---
> >>>> Could you please go ahead and retest using a GENERIC kernel and see if
> >>>> you can reproduce? There could be something in your custom kernel
> >>>> causing the offsets or linker set magic used by the DPCPU bits to break
> >>>> which in turn is triggering this panic in SIFTR.
> >>>
> >>> I'll retry without pf first, and with GENERIC afterwards.
> >>
> >> Sounds good, thanks.
> >
> > Taking pf (and altq) out of the picture doesn't seem to make
> > a difference.
>
> Wouldn't have expected it to. Will be very curious to know if the panic
> is triggered in GENERIC.
It's not. I, too, get pfil.c related LORs though:
lock order reversal:
1st 0xffffffff80e5c568 PFil hook read/write mutex (PFil hook read/write mutex)
@ /usr/src/sys/net/pfil.c:77
2nd 0xffffffff80e5dd68 udp (udp) @
/usr/src/sys/modules/pf/../../contrib/pf/net/pf.c:3035
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
_witness_debugger() at _witness_debugger+0x2e
witness_checkorder() at witness_checkorder+0x81e
_rw_rlock() at _rw_rlock+0x5f
pf_socket_lookup() at pf_socket_lookup+0x1c5
pf_test_udp() at pf_test_udp+0x8b0
pf_test() at pf_test+0x1089
pf_check_in() at pf_check_in+0x39
pfil_run_hooks() at pfil_run_hooks+0xcf
ip_input() at ip_input+0x2ae
swi_net() at swi_net+0x151
intr_event_execute_handlers() at intr_event_execute_handlers+0x66
ithread_loop() at ithread_loop+0xb2
fork_exit() at fork_exit+0x12a
fork_trampoline() at fork_trampoline+0xe
--- trap 0, rip = 0, rsp = 0xffffff8000044d30, rbp = 0 ---
lock order reversal:
1st 0xffffffff80e5c568 PFil hook read/write mutex (PFil hook read/write mutex)
@ /usr/src/sys/net/pfil.c:77
2nd 0xffffffff80e5d788 tcp (tcp) @
/usr/src/sys/modules/siftr/../../netinet/siftr.c:698
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
_witness_debugger() at _witness_debugger+0x2e
witness_checkorder() at witness_checkorder+0x81e
_rw_rlock() at _rw_rlock+0x5f
siftr_chkpkt() at siftr_chkpkt+0x3c4
pfil_run_hooks() at pfil_run_hooks+0xcf
ip_input() at ip_input+0x2ae
swi_net() at swi_net+0x151
intr_event_execute_handlers() at intr_event_execute_handlers+0x66
ithread_loop() at ithread_loop+0xb2
fork_exit() at fork_exit+0x12a
fork_trampoline() at fork_trampoline+0xe
--- trap 0, rip = 0, rsp = 0xffffff8000044d30, rbp = 0 ---
My custom kernel normally doesn't have INVARIANTS and WITNESS
enabled, so I'll try to enable them next.
Fabian
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