[OpenBIOS] ppc(64) debugging (was: Q: How to "squeeze" C functions in between two symbols?)

[Alexander Graf]

On 31.10.2010, at 16:33, Andreas Färber wrote:

> Am 08.10.2010 um 15:30 schrieb Alexander Graf:
> 
>> You can use the apple gdb without an object file, so you don't get symbols. But if you have an instruction pointer, just
>> 
>> $ qemu-system-ppc -s -S ...
>> (gdb) target remote localhost:1234
>> (gdb) b *0x1234 <- address of rtas_something
>> (gdb) c
>> 
>> It should break on that IP and then you can evaluate the register contents at least. Either by
>> 
>> (gdb) info registers
>> 
>> or
>> 
>> (qemu) info registers
> 
> I'm trying to find out how far we get with the ppc64 OpenBIOS, so I've tried the following:
> 
> $ .../ppc64-softmmu/qemu-system-ppc64 ... -nographic -prom-env 'auto-boot?=false' -s -S
> 
> $ gdb --arch=ppc64
> GNU gdb 6.3.50-20050815 (Apple version gdb-967) (Tue Jul 14 02:15:14 UTC 2009)
> Copyright 2004 Free Software Foundation, Inc.
> GDB is free software, covered by the GNU General Public License, and you are
> welcome to change it and/or distribute copies of it under certain conditions.
> Type "show copying" to see the conditions.
> There is absolutely no warranty for GDB.  Type "show warranty" for details.
> This GDB was configured as "powerpc-apple-darwin".
> (gdb) target remote localhost:1234
> Remote debugging using localhost:1234
> [New thread 1]
> 0x0000000000000000 in ?? ()
> (gdb) b *0xfffffffc
> Breakpoint 1 at 0xfffffffc
> (gdb) c
> Continuing.
> 
> It doesn't break though and executes to the OpenBIOS prompt.
> 0xfffffffc is supposed to be the hard reset vector, i.e. the very first instruction it must execute to branch to _entry.

Uuuh IIRC there's a register that's set on RESET which defines an offset to take when in real mode code or so. Please check the cpu init code for 970, it should tell you :)

Alex