More weird behaviour on PowerPC.
joel.sherrill at OARcorp.com
Mon May 24 20:06:56 UTC 2010
On 05/24/2010 03:00 PM, Nick Thomas wrote:
> My colleague and I have spent the last couple of days upgrading our RTEMS OS
> from 4.7.1 to 4.7.3. At the same time we have added the -fno-strict-aliasing
> flag to the compiler.
> I don't this these modifications have helped in our stability issues,
> because I have just observed a weird thing with the new build :(
I hate to ask the obvious, but have you blown a stack? It would not
be for FILTER_Task but either the one created before or after it.
I don't remember which in 4.7.x. I think it would be the one created
next after it but not 100% sure.
> It's just taken a 0x0700 (Program Exception). And looking at the call stack
> I see:
> (gdb) bt
> #0 0x00000014 in ?? ()
> #1 0x00000010 in ?? ()
> #2 0x00325148 in FILTER_Task_Entry ()
> #3 0x003197b8 in task_launch ()
> The last good address is 0x00325148. Which is indeed in FILTER_Task_Entry,
> the disassembly around 0x00325148 is:
> 0x0032513c<FILTER_Task_Entry+540>: stw r10,1864(r16)
> 0x00325140<FILTER_Task_Entry+544>: sth r0,4(r11)
> 0x00325144<FILTER_Task_Entry+548>: bl 0x323964
> 0x00325148<FILTER_Task_Entry+552>: b 0x325024
> 0x0032514c<FILTER_Task_Entry+556>: lwz r4,1912(r19)
> 0x00325150<FILTER_Task_Entry+560>: li r5,0
> So, at 0x00325148 is a simple branch instruction to an address earlier
> inside the same function. But, the call stack shows that it next went to
> 0x00000010 !!!!
> What on earth could make it do that?
> I don't know if this is useful, but here is the dump of the memory at those
>> md 0x0032513c 6
> 0032513c : 0x91500748 -1857026232 .P.H
> 00325140 : 0xb00b0004 -1341456380 ....
> 00325144 : 0x4bffe821 1275062305 K..!
> 00325148 : 0x4bfffedc 1275068124 K...
> 0032514c : 0x80930778 -2137847944 ...x
> 00325150 : 0x38a00000 950009856
> Nick Thomas
> Email: nick.thomas at pixsan.com
> rtems-users mailing list
> rtems-users at rtems.org
Joel Sherrill, Ph.D. Director of Research& Development
joel.sherrill at OARcorp.com On-Line Applications Research
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