On Thu, Dec 23, 2004 at 04:58:03PM +0530, Nori, Soma Sekhar wrote:
> We are using montavista Linux version 2.4.17, gcc version 2.95.3 running on
> MIPS 4kec.
>
> Here is the dump:
> $0 : 00000000 0044def4 000001ac 0000006b 00000000 7fff7c08 00000001 00000000
> $8 : 0000fc00 00000001 00000000 941524d0 00004700 00000000 97fc3ea0 7fff7c08
> $16: 100048a4 100029d8 100029d8 10003020 00000000 7fff7dc8 10003b60 2d8e2163
> $24: 00000001 2ab7bc30 10008e70 7fff7bf0 04000000 00439e50
> Hi : 00000000
> Lo : 00000001
> epc : 00439e84 Not tainted
> Status: 0000fc13
> Cause : 10800028
> Process sh (pid: 18, stackpage=97fc2000)
> Stack: 00000001 00000000 2abd0ff0 7fff7c28 10008e70 00000000 10008e6c 00000000
> 100049a0 0042f188 00000000 100029d8 00000001 00000001 7fff7f04 10008e70
> 00427fe4 00427f00 00000000 00000000 10002764 10008e70 10008e70 00000000
> 00000000 00000000 10008e70 00422734 00000001 00000001 7fff7f04 10008e70
> 10008e70 00000003 10008e70 004315cc 00000001 00000000 10002764 00000000
> 10008e70 ...
> Call Trace:
> Code: 00000000 2421dd48 00220821 <8c220000> 00000000 005c1021 00400008
> 0000
> 0000 8f99802c
>
> The epc is not in kernel space and ksymoops did not provide any info. The epc
> keeps changing to different locations in user space over multiple runs.
In a case like this you're likely dealing with double exceptions. Your
code is taking an exception and the exception handler while running with
c0_status set is taking another exception. If the first exception handler
is still running with the c0_status.exl bit set the CPU when taking the
second exception it will not record the PC of the second exception and
you will have a seemingly unexplainable exception.
A few processors have the nasty habit of throwing RI receptions or do
similarly weird things when executing code that is mapped through multiple
TLB pages but the 4kEC shouldn't.
Ralf
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