Re: [Qemu-devel] [PATCH] gdb: provide the name of the architecture in the target.xml

[Peter Maydell]

On 6 October 2014 20:14, David Hildenbrand <address@hidden> wrote:
> actually the questions were addressed in the last review. Haven't received any
> answer from you to my reply. Maybe some mails got lost in the system.
>
> 32bit arm:
> -"On my way through the possible architecture names
>   (binutils-gdb/gdb/features/*.xml), I wasn't able to come up with the right 
> name
>   for arm 32 bit (arm-core.xml) - they don't specify any. This patch therefore
>   adapts to the xml files from gdb."

But can we specify it for 32 bit ARM? Saying "set arch arm" at
a gdb prompt works OK, so can we pass "arm" through in the XML too?
The gdb documentation says that anything that works as an arch
string at the gdb prompt is OK to pass through in the XML.

> - Not included in this patch as Edgar provided a patch in the previous thread
>   (that's why he is on cc) that can easily be adopted. I don't want to simply
>   include his effort in my patch :) And we have to make sure that this name is
>   the right one.
>
> More complicated names:
> - "The architecture should be known at the same point when specifying the xml
>   file. So if anyone can come up with the proper arm name in the future (or 
> even some
>   kind of detection algorithm), it can simply be set in target-arm/cpu.c 
> (after
>   "arm-core.xml")."

At the moment we specify the XML file in the CPU class init
function, whereas specific CPU subfeatures may not be known
until rather later when we actually instantiate a CPU
object. Are there any cases where we'd actually need to care?
I can't tell, because you seem to be taking the "we're going
to ignore all the CPU types where the answer isn't obvious"
approach. The ARM "iwmmxt" architecture would be an interesting
one to check, since if we really need to use that string rather
than a generic "arm" string we need to postpone choosing the
name til CPU init time when we set up the feature bits.

> - The same should apply for all architectures. So we can set (or even build)
>   the proper string when also specifying the core xml file.
>
> Do you have something in mind like your "powerpc:common" and "powerpc:e500"
> example? To build the names based on some pattern?
>
> I don't think that we can generalize the name format here (at least "aarch64"
> makes me assume that :) ). I think it would be enough to set the complete
> strings in the class init functions.

Only if the complete string doesn't depend on things we don't
know at that point. Maybe we can always pick a generic
name for each architecture, in which case we should do that
(and do it for all architectures now, not only three).
What does gdb do differently if you specify "powerpc:common"
versus "powerpc:e500", for instance? Is it anything we care
about?

thanks
-- PMM