Re: [Qemu-devel] QEMU as ISS (Instruction Set Simulator)

[Alex Bennée]

Libo Zhou <address@hidden> writes:

> Hi Alex,
>
>
> gdb says remote 'g' packet reply is too long, and then prints out a
> long string of zeros and some other digits sparsely.

Sounds like your gdb isn't multiarch aware. Debian/Ubuntu have multiarch
binutils which are aware of more than just the host architecture.

>
>
> I have tried a lot of combinations of flags but I just can't get it running 
> properly. Do you know what is causing this error?
>
>
> Cheers,
>
> Libo
>
>
>
>
>
> ------------------ Original ------------------
> From:  "Alex Bennée";<address@hidden>;
> Send time: Friday, Sep 6, 2019 5:19 PM
> To: "Libo Zhou"<address@hidden>;
> Cc: "qemu-devel"<address@hidden>; "Aleksandar Markovic"<address@hidden>;
> Subject:  Re: [Qemu-devel] QEMU as ISS (Instruction Set Simulator)
>
>
>
>
> Libo Zhou <address@hidden> writes:
>
>> Hi Alex,
>>
>>
>> I just need to log the registers and memory after the program finishes
>> its execution. Is it possible to add this functionality myself?
>
> You'll need to set some sort of breakpoint on the last instruction so
> gdb can inspect things before the program is unloaded. I think it's
> possible to wire poweroff events to the gdbstub but I haven't looked
> into that myself.
>
>> As for the GDB option, can you tell me the specific steps to do that? I've 
>> tried it myself but I had no luck getting it running due to me being new to 
>> all this.
>>
>
> For linux-user:
>
>   $QEMU -g 1234 $PRG
>
> for system emulation
>
>   $QEMU -s -S
>
> and then on the gdb end:
>
>   gdb $BIN -ex "target remote localhost:1234"
>
> and then you can operate as you normally do with a gdb session. GDB has
> two scripting interfaces. The command mode is basically a list of gdb
> commands but might work for what you want. If you want to be a bit more
> programatic you can use python. See the example in
> tests/guest-debug/test-gdbstub.py
>
>>
>> Thanks,
>> Libo
>>
>>
>>
>> ------------------ Original ------------------
>> From:  "Alex Bennée";<address@hidden>;
>> Send time: Thursday, Sep 5, 2019 8:58 PM
>> To: "qemu-devel"<address@hidden>;
>> Cc: "Aleksandar Markovic"<address@hidden>;
>> Subject:  Re: [Qemu-devel] QEMU as ISS (Instruction Set Simulator)
>>
>>
>>
>>
>> Libo Zhou <address@hidden> writes:
>>
>>> Do you know where in the source file I should look into to add my custom 
>>> logging functionality?
>>>
>>>
>>> Or, would you suggest using gdb to look at my target register and memory 
>>> contents? The answer in this link below looks really promising. I'm gonna 
>>> give it a try first.
>>>
>>> https://stackoverflow.com/questions/39503997/how-to-run-a-single-line-of-assembly-then-see-r1-and-condition-flags
>>
>> The gdbstub should allow you do full introspection and adding
>> additional registers is fairly easy, see FOO_gdb_[set|get]_reg helpers
>> in the appropriate target/FOO directories.
>>
>>> However, if I am able to customize log, it will be super convenient.
>>
>> So you want something above what -d cpu will show you?
>>
>>>
>>>
>>>
>>> Cheers,
>>>
>>> Libo
>>>
>>>
>>>
>>> ------------------ Original ------------------
>>> From:  "Aleksandar Markovic";<address@hidden>;
>>> Send time: Thursday, Sep 5, 2019 6:54 PM
>>> To: "Libo Zhou"<address@hidden>;
>>> Cc: "qemu-devel"<address@hidden>;
>>> Subject:  Re: [Qemu-devel] QEMU as ISS (Instruction Set Simulator)
>>>
>>>
>>>
>>> 04.09.2019. 05.23, "Libo Zhou" <address@hidden> ?е написао/ла:
>>>>
>>>> Hi Aleksandar,
>>>>
>>>> I have spent some time looking at your MXU ASE patch. It's super helpful.
>>> I need to do exactly the same thing as you did.
>>>>
>>>> Now I just need a way to observe the memory and register file contents to
>>> debug my instruction set simulator. I played with the "-d" switch to log a
>>> bunch of information, but it seems that none of the items is of my
>>> interest. The "-d cpu_reset" option displays all zeros in the GPR log.
>>>>
>>>
>>> It looks you need a custom logging tailored to your needs, based on
>>> intercepting the instructions you added.
>>>
>>> Aleksandar
>>>
>>>> Please take your time, as I fully understand you need to work on Qemu
>>> while answering all my questions. Again, thank you very much for your help!
>>>>
>>>> Cheers,
>>>> Libo
>>>>


--
Alex Bennée