Re: [PATCH v5 4/4] sim: mips: Add simulator support for mips32r6/mips64r6

[Dragan Mladjenovic <Dragan.Mladjenovic@syrmia.com>]

On 28-Dec-22 01:12, Mike Frysinger wrote:
> On 27 Dec 2022 20:35, Dragan Mladjenovic wrote:
>> On 25-Dec-22 01:26, Mike Frysinger wrote:
>>> On 02 Feb 2022 11:17, Dragan Mladjenovic wrote:
>>>> --- a/sim/mips/configure.ac
>>>> +++ b/sim/mips/configure.ac
>>>> @@ -216,6 +227,7 @@ if test ${sim_gen} = MULTI; then
>>>>    #include "sim-main.h"
>>>>    #include "multi-include.h"
>>>>    #include "elf-bfd.h"
>>>> +#include "elfxx-mips.h"
>>>>    #include "elf/mips.h"
>>>>    
>>>>    #define SD sd
>>>> @@ -235,7 +247,11 @@ sim_engine_run (SIM_DESC sd,
>>>>    	   & EF_MIPS_ARCH_ASE_MICROMIPS)
>>>>        mach = bfd_mach_mips_micromips;
>>>>      else
>>>> -    mach = STATE_ARCHITECTURE (SD)->mach;
>>>> +  {
>>>> +     mach = _bfd_elf_mips_mach (elf_elfheader (STATE_PROG_BFD (sd))->e_flags);
>>>> +     if (!mach)
>>>> +       mach = STATE_ARCHITECTURE (SD)->mach;
>>>> +  }
>>>
>>> why do you need this logic in the main engine run routine ?  why isn't the
>>> STATE_ARCHITECTURE value already set to the correct value ?  if it isn't set
>>> correctly all the time, this can lead to incorrect behavior elsewhere when
>>> code checks it.
>>>
>>> when the sim is opened, the bfd_mach is either explicitly passed in (which
>>> gdb does), or initialized with a call to the bfd library APIs.  see the
>>> sim/common/sim-utils.c:sim_analyze_program code.
>>
>> Sorry but the exact reason for doing so eludes me. It is done on
>> internal jump for gdb 8 to gdb 10, permissibly to allow running
>> binary even whet set arch forces older mips isa, but I see little
>> use of that outside of testsuite maybe.
> 
> i'd argue that if you load a binary for one ISA, then force the runtime
> to use a different one, and the result crashes, then the sim is WAI.  it
> should behave as real hardware does, and if you load a binary that needs
> a newer ISA than a CPU provides, it won't work.
> 
> do you know if there's a testsuite, sim or gdb, that exercises this ?
> -mike

Hi,

Sorry for the late reply. I couldn't find any.


Best regards,
Dragan