RE: [Patch, microblaze]: Port of Linux gdbserver

[Ajit Kumar Agarwal <ajit.kumar.agarwal@xilinx.com>]

-----Original Message-----
From: Pedro Alves [mailto:palves@redhat.com] 
Sent: Wednesday, September 17, 2014 1:45 PM
To: Ajit Kumar Agarwal; Michael Eager; Joel Brobecker
Cc: gdb-patches@sourceware.org; Vinod Kathail; Vidhumouli Hunsigida; Nagaraju Mekala
Subject: Re: [Patch, microblaze]: Port of Linux gdbserver

On 09/17/2014 07:16 AM, Ajit Kumar Agarwal wrote:

> From: Pedro Alves [mailto:palves@redhat.com] On 09/16/2014 07:41 AM, 
> Ajit Kumar Agarwal wrote:
>> This is needed as gdbserver code expects the register pc as "pc" instead of "rpc" for baremetel. The microblaze-linux-core.xml is changed from "rpc" to "pc" for gdbserver code to work.
> 
>>> This doesn't make much sense to me.  Can you expand please?  Why would you want the register to be named differently on Linux?  We've defined the >>org.gnu.gdb.microblaze.core with "rpc", presumably because that's what the architecture calls that core register.
> 
>>> Not reporting all the registers with the exact names GDB reports should be making GDB consider the description invalid.  Aren't you seeing that happen?
> 
> In Microblaze gdbserver code linux-microblaze-low.c we have are passing the "pc" in supply_register_by_name and the baremetal org.gnu.gdb.microblaze.core its been defined as "rpc". Due to this in regcache.c where the find_regno function compares "pc" passed with "rpc" and reports failures. That is why we have create microblaze-linux-core.xml to have "pc" instead of "rpc".
> 
> static void
> microblaze_set_pc (struct regcache *regcache, CORE_ADDR pc) {
>   unsigned long newpc = pc;
>   supply_register_by_name (regcache, "pc", &newpc); }

>>But that is port-specific code that you're adding with this patch.
>>So just write instead:

  >>supply_register_by_name (regcache, "rpc", &newpc);

>>Why wouldn't that work?  But maybe I'm missing something.

Thanks Pedro !! I will make the change from "pc" to "rpc" in supply_register_by_name.  

>>> Note nothing is done with valid_p.  It's write-only.  Compare with other ports, like arm-tdep.c or mips-tdep.c.
> 
> Would look into this and will make the modification.

Thanks.

Pedro Alves