Re: [Qemu-discuss] Qemu-discuss Digest, Vol 95, Issue 8

[G 3]

>
> Aug 7, 2019, 8:32 PM by address@hidden:
>
> >>
> >> I'm definitetly not familiar with gdb debugging. But if someone is
> >> interested in the problem and wants to be a tutor I'm up for the job.
> >> I'm always up to learn something new.
> >>
> >
> https://wiki.qemu.org/Documentation/Platforms/PowerPC#Debugging_qemu-system-ppc_with_GDB_on_an_x86_Linux_host
> > This information may help you.
> >
> Thanks, this helped a bit.
>
> Short version:
> I found differences in the behaviour with or without -cpu 7447a_v1.2
> option. It seems gdb can't debug with the cpu-option set. Commands like
> 'backtrace' or 'where' did not finsh but had to be killed.
>
> Long version:
> I started three terminals.
>
> Terminal 1:
> | /usr/bin/qemu-system-ppc -machine mac99,via=pmu -m 512M -g 1280x854x32
> -s -S -prom-env "auto-boot?=false" --nographic -monitor
> "unix:sockets/ppcdebug",server,nowait
> | ##### after continuing in qemu:
> | s>> et_property: NULL phandle
> |
> | >> =============================================================
> | >> OpenBIOS 1.1 [Dec 27 2018 19:16]
> | >> Configuration device id QEMU version 1 machine id 1
> | >> CPUs: 1
> | >> Memory: 512M
> | >> UUID: 00000000-0000-0000-0000-000000000000
> | >> CPU type PowerPC,G4
> | milliseconds isn't unique.
> | Welcome to OpenBIOS v1.1 built on Dec 27 2018 19:16
> |
> | 0 >
>
>
> Terminal 2:
> | nc -U sockets/ppcdebug
> | (qemu) info status| info status| VM status: paused (prelaunch)| #####
> after continuing in qemu:| (qemu) info status
> | info status
> | VM status: running
> | ##### after CTRL-C in qemu| (qemu) info status
> | info status
> | VM status: paused
>
>
> Terminal 3:
> | gdb-multiarch
> | (gdb) target remote localhost:1234
> | Remote debugging using localhost:1234
> | warning: No executable has been specified and target does not support
> | determining executable automatically.  Try using the "file" command.
> | 0x0001f0ff in ?? ()
> | (gdb) show arch
> | The target architecture is set automatically (currently powerpc:common)
> | (gdb)
> | (gdb) continue
> | Continuing.
> | ##### I waited about a minute
> | ^C| Program received signal SIGINT, Interrupt.
> | 0x98d2f1ff in ?? ()
> | (gdb) where
> | #0  0x98d2f1ff in ?? ()
> | Backtrace stopped: previous frame identical to this frame (corrupt
> stack?)
>
>
> Now, the same with '-cpu 7447a_v1.2' option.
>
> Terminal 1:
> | /usr/bin/qemu-system-ppc -machine mac99,via=pmu -m 512M -g 1280x854x32
> -s -S -prom-env "auto-boot?=false" --nographic -monitor
> "unix:sockets/ppcdebug",server,nowait -cpu 7447a_v1.2
> | ##### There was no further output during the whole session
> Terminal 2: # same output as before
> | nc -U sockets/ppcdebug
> | (qemu) info status
> | info status
> | VM status: paused (prelaunch)
> | ##### after continuing in qemu:
> | (qemu) info status| info status
> | VM status: running
> | ##### after CTRL-C in qemu
> | (qemu) info status| info status
> | VM status: paused
>
> Terminal 3:
> | gdb-multiarch| (gdb) target remote localhost:1234| Remote debugging
> using localhost:1234| warning: No executable has been specified and target
> does not support| determining executable automatically.  Try using the
> "file" command.| 0x0001f0ff in ?? ()| (gdb) show arch| The target
> architecture is set automatically (currently powerpc:common)| (gdb)
> continue| Continuing.
> | ##### I waited about a minute
> | ^C| Program received signal SIGINT, Interrupt.| 0x3cc9f2ff in ?? ()|
> (gdb) where| ##### I waited about a minute
> | ^CQuit| # I had to kill the where command - there was no output
> I'm stuck. Which should be the next steps?
> Thomas
>

I would print out the instructions that are executed:

x/10i $pc