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

[Aleksandar Markovic]

10.09.2019. 11.57, "Libo Zhou" <address@hidden> је написао/ла:
>
> 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.
>
> 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?
>

This is a known bug, actually in gdb, but there is a workaround is to
rollback a commit made  around a year ago in QEMU, about 64-bit FPU Mips
registers. Or you can fix the buffer size in gdb.

Aleksandar

> 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