Identifying PowerPC architecture

Identifying PowerPC architecture

[Michael Eager]

I'm looking at how gdb decides which arch/mach it is
working with for PowerPC.  It looks like it always picks up
rs6000:6000 as processor type.

When rs6000_gdbarch_init(struct gdbarch_info info,
struct gdbarch_list *arches) is called, arches is NULL.
As a result, it creates up a default arch/mach based on
info.bfd_arch_info.

The arches data is initialized by gdbarch_register() whichs
sets gdbarch_registry[*]->arches to NULL and I don't see
anywhere that this is changed to point to a list of valid
arches.

Am I missing something somewhere?  How is this supposed to work?

-- 
Michael Eager	 eager@eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077

Re: Identifying PowerPC architecture

[Daniel Jacobowitz]

On Thu, Jan 11, 2007 at 12:46:55PM -0800, Michael Eager wrote:
> I'm looking at how gdb decides which arch/mach it is
> working with for PowerPC.  It looks like it always picks up
> rs6000:6000 as processor type.
> 
> When rs6000_gdbarch_init(struct gdbarch_info info,
> struct gdbarch_list *arches) is called, arches is NULL.
> As a result, it creates up a default arch/mach based on
> info.bfd_arch_info.

->arches is a list of previously initialized gdbarches.  They're
initialized by other calls to rs6000_gdbarch_init.

gdbarch_list_lookup_by_info will only return something with the
same bfd_arch_info as it is passed.

So, if you're not getting the right arch, you're probably not
starting with the right bfd_arch_info.  I don't know if PowerPC
tags binaries with the processor; I don't remember any such markings
for PowerPC.

-- 
Daniel Jacobowitz
CodeSourcery

Re: Identifying PowerPC architecture

[Michael Eager]

Daniel Jacobowitz wrote:
> On Thu, Jan 11, 2007 at 12:46:55PM -0800, Michael Eager wrote:
>> I'm looking at how gdb decides which arch/mach it is
>> working with for PowerPC.  It looks like it always picks up
>> rs6000:6000 as processor type.
>>
>> When rs6000_gdbarch_init(struct gdbarch_info info,
>> struct gdbarch_list *arches) is called, arches is NULL.
>> As a result, it creates up a default arch/mach based on
>> info.bfd_arch_info.
> 
> ->arches is a list of previously initialized gdbarches.  They're
> initialized by other calls to rs6000_gdbarch_init.

I don't see where that happens, but I'll take your word.

> gdbarch_list_lookup_by_info will only return something with the
> same bfd_arch_info as it is passed.
> 
> So, if you're not getting the right arch, you're probably not
> starting with the right bfd_arch_info.  I don't know if PowerPC
> tags binaries with the processor; I don't remember any such markings
> for PowerPC.

Nope, there's no model info for PowerPC in the ELF file.

-- 
Michael Eager	 eager@eagercon.com
1960 Park Blvd., Palo Alto, CA 94306  650-325-8077

Re: Identifying PowerPC architecture

[Daniel Jacobowitz]

On Thu, Jan 11, 2007 at 01:03:57PM -0800, Michael Eager wrote:
> >gdbarch_list_lookup_by_info will only return something with the
> >same bfd_arch_info as it is passed.
> >
> >So, if you're not getting the right arch, you're probably not
> >starting with the right bfd_arch_info.  I don't know if PowerPC
> >tags binaries with the processor; I don't remember any such markings
> >for PowerPC.
> 
> Nope, there's no model info for PowerPC in the ELF file.

Then you're always going to get the default processor, unless you
use "set architecture" (or the new XML <architecture> bit I committed
to HEAD this week).

-- 
Daniel Jacobowitz
CodeSourcery

Re: Identifying PowerPC architecture

[Mark Kettenis]

> Date: Thu, 11 Jan 2007 12:46:55 -0800
> From: Michael Eager <eager@eagercon.com>
> 
> I'm looking at how gdb decides which arch/mach it is
> working with for PowerPC.  It looks like it always picks up
> rs6000:6000 as processor type.

For what it is worth, I get powerpc:common for OpenBSD.  Probably
because of the fact that the OpenBSD OS/ABI support is registered
with:

  gdbarch_register_osabi (bfd_arch_powerpc, 0, GDB_OSABI_OPENBSD_ELF,
                          ppcobsd_init_abi);

Mark