[PATCH] Bus error on ARMv7 when using OSPF

[Matthew Reeve]

Hi, yes sure, here it is. Please let me know if this does not give you 
what you need.

Thanks!

root at OpenWrt:/tmp# gdb debug/bird bird.1623776146.6869.7.core
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Reading symbols from debug/bird...
[New LWP 6869]
Core was generated by `./bird'.
Program terminated with signal SIGBUS, Bus error.
#0  ospf_rt_reset (p=0x1d610a0) at proto/ospf/rt.c:1646
1646    proto/ospf/rt.c: No such file or directory.
(gdb) bt
#0  ospf_rt_reset (p=0x1d610a0) at proto/ospf/rt.c:1646
#1  ospf_rt_spf (p=0x1d610a0) at proto/ospf/rt.c:1698
#2  ospf_rt_spf (p=0x1d610a0) at proto/ospf/rt.c:1688
#3  ospf_disp (timer=<optimized out>) at proto/ospf/ospf.c:468
#4  0x00061574 in timers_fire (loop=0xc4878 <main_timeloop>) at 
lib/timer.c:235
#5  0x00012ca8 in io_loop () at sysdep/unix/io.c:2195
#6  main (argc=<optimized out>, argv=<optimized out>) at 
sysdep/unix/main.c:939
(gdb)

On 18/06/2021 16:16, Ondrej Zajicek wrote:
> On Mon, Jun 14, 2021 at 04:25:04PM +0100, Matthew Reeve wrote:
>> Hi,
>>
>> when using bird 2.0.8 on openwrt 21.02 (and other versions) on a Netgear
>> R7800 router, if the OSPF protocol is used, either v2 or v3, bird
>> immediately crashes on startup with:
>>
>> Fri Jun 11 14:41:11 2021 daemon.info bird: Started
>> Fri Jun 11 14:41:11 2021 kern.err kernel: [ 3500.853248] Alignment trap: not
>> handling instruction f44c0a1f at [<00035848>] Fri Jun 11 14:41:11 2021
>> kern.alert kernel: [ 3500.853283] 8<--- cut here ---
>> Fri Jun 11 14:41:11 2021 kern.alert kernel: [ 3500.859363] Unhandled fault:
>> alignment exception (0x801) at 0x007e0624
>> Fri Jun 11 14:41:11 2021 kern.alert kernel: [ 3500.862443] pgd = 0bbef4fd
>> Fri Jun 11 14:41:11 2021 kern.alert kernel: [ 3500.868821] [007e0624]
>> *pgd=5d6ca835, *pte=5c40b75f, *ppte=5c40bc7f
>>
>>
>> This router uses an ARMv7 processor and the issue seems to be to do with
>> memory alignment issues. I've debugged it and traced it to an access to the
>> top_hash_entry struct. I've found that if I add the PACKED macro to the
>> struct definition then it fixes the problem, as per this patch:
> Hi
>
> Thanks, could you try to get backtrace from the coredump using gdb to see
> where is the invalid access?
>
>