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

[Duarte Silva <duarte.silva@serializing.me>]

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

OUT: [size=84]
0x606026b0:  mov    -0x4(%r14),%ebp
0x606026b4:  test   %ebp,%ebp
0x606026b6:  jne    0x606026f5
0x606026bc:  mov    $0x765d1fa4,%ebp
0x606026c1:  mov    %ebp,0x80(%r14)
0x606026c8:  mov    %r14,%rdi
0x606026cb:  mov    $0x14,%esi
0x606026d0:  callq  0x600acaa0
0x606026d5:  jmpq   0x606026da
0x606026da:  mov    $0x765d1fa8,%ebp
0x606026df:  mov    %ebp,0x80(%r14)
0x606026e6:  mov    $0x7fe1de9d3bc0,%rax
0x606026f0:  jmpq   0x62561d26
0x606026f5:  mov    $0x7fe1de9d3bc3,%rax
0x606026ff:  jmpq   0x62561d26

do_raise_exception_err: 20 0
qemu: uncaught target signal 4 (Illegal instruction) - core dumped
Illegal instruction

I have found on QEMU code the following definitions for udi4 (on file 
disas/mips.c):

{"udi4", "s,t,d,+1", 0x70000014, 0xfc00003f, WR_d|RD_s|RD_t, 0, I33 },
{"udi4", "s,t,+2",    0x70000014, 0xfc00003f, WR_d|RD_s|RD_t, 0, I33 },
{"udi4", "s,+3",      0x70000014, 0xfc00003f, WR_d|RD_s|RD_t, 0, I33 },
{"udi4", "+4",         0x70000014, 0xfc00003f, WR_d|RD_s|RD_t, 0, I33 },

Does any of these match the above instruction? It seems so no?

Cheers,
Duarte

> 
> that will cause it to only translate one instruction at a time, and to
> dump each one as it is translated. The last one printed will very likely
> to be the one that is causing the problem.
> 
> Cheers
> James