Re: illegal hardware instruction during MIPS-I ELF linux user emulation

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 9/23/19 4:42 PM, Peter Maydell wrote:
> On Mon, 23 Sep 2019 at 15:40, Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>> So currently there is no MIPS-I only CPU.
>> Note that the code got written with MIPS32 in mind, and implementing
>> MIPS-I requires a considerable amount of change in the codebase.
> 
> ...but MIPS-I binaries should run on MIPS-II and newer CPUs, shouldn't
> they?

Some MIPS-I instructions where removed for MIPS-II (as RFE) and they are
not implemented. Also some CP0 registers are different.

>> IMO it is likely the RFE (Return from Exception) instruction.
> 
> It seems unlikely that a linux userspace binary would be trying to
> execute RFE...

Oh I thought it was system emulation, indeed it can't be RFE.

One GCC release targetting R3000 (Philips PR31700, Toshiba TX39) doesn't
emit NOP for branch's delay slot. I remember QEMU fails to run the
binaries it generates, but I don't remember how it fails.

Libo, can you provide more information about the cross-compiler you use
and the flags you use when calling it please?

Thanks,

Phil.