Re: [Qemu-devel] Support for NetLogic XLP Processors

[Leon Alrae <leon.alrae@imgtec.com>]

On 25/03/2015 15:38, Duarte Silva wrote:
> On Wednesday 25 March 2015 14:54:41 Leon Alrae wrote:
>> On 25/03/2015 14:44, Leon Alrae wrote:
>>> Hi Duarte,
>>>
>>> On 25/03/2015 14:20, Duarte Silva wrote:
>>>> On Wednesday 25 March 2015 13:13:14 James Hogan wrote:
>>>>> Hi Duarte,
>>>>>
>>>>> On 22/03/15 11:13, Duarte Silva wrote:
>>>>>> Hi guys,
>>>>>>
>>>>>> I have been struggling to get some binaries compiled for NetLogic XLP
>>>>>> processor to run under QEMU. I have tried a bunch of things (most going
>>>>>> back and forth) and always get the following error message:
>>>>>>
>>>>>> qemu: uncaught target signal 4 (Illegal instruction) - core dumped
>>>>>> Illegal instruction
>>>>>>
>>>>>> I tried to debug it using GDB but to no avail. Does anybody have ideas?
>>>>>> I'm
>>>>>> running QEMU 2.2.1.
>>>>>
>>>>> It sounds like the program had an instruction that QEMU doesn't
>>>>> recognise, or doesn't think should be allowed on the current CPU which
>>>>> you've set with -cpu. You might be able to find out what that
>>>>>
>>>>> instruction is by putting this on your qemu command line:
>>>>>  -singlestep -d in_asm
>>>>
>>>> Hi James,
>>>>
>>>> thanks for the help :) I have tried with all the CPU's available. None of
>>>> them worked, so I just leave it as undefined. It seems the offending
>>>> instruction is "udi4".
>>>>
>>>> (...)
>>>> IN:
>>>> 0x765d1fa4:  udi4       a0,v0,zero,0x0
>>>
>>> According to this line you are trying to use MIPS32 CPU whereas I
>>> presume you would like MIPS64R2? Please try 5KEf CPU for example which
>>> is available in qemu-mips64 and qemu-mips64el QEMU binaries for big and
>>> little endian respectively.
>>
>> I just noticed the QEMU version you are using and it doesn't contain
>> 5KEf and 5KEc CPUs. Please try MIPS64R2-generic.
>>
>> Leon
> 
> Hi Leon,
> 
> have a look at the "binary-info.txt" file in the first e-Mail. It does use the 
> ELF magic for 32 bits ELF, not the 64 bits, that's why I get the following:
> 
> # chroot rootfs/ /usr/local/bin/qemu-mips64 -cpu MIPS64R2-generic /bin/sh
> /bin/sh: Invalid ELF image for this architecture
> 
> Is there a way to force the execution of the binary even if the flag doesn't 
> match?
> 
> Also, if you have a look at the flags you get: noreorder, cpic, 32bitmode, 
> unknown CPU, o32, mips64r2. So, is it 64 bits or 32 bits ELF file?

I see, this mips64r2 binary has o32 ABI. It indeed would work in
qemu-mips provided there are no mips64r2-specific instructions. I think
I jumped a bit too quickly to the conclusion.

QEMU's mips/disas doesn't help much in this case as it just indicates
User Defined Instruction. Presumably this instruction is specific to
this processor and is missing in QEMU. Are you able to get disassembly
of your program and look up what is under 0x765d1fa4 address which
caused the illegal instruction?

Leon