How to disable Altivec registers in powerpc GDB ?

How to disable Altivec registers in powerpc GDB ?

[James Murray]

I've built gdb 6.9 using --target=powerpc-eabi

gdb appears to think that my target has the altivec vector registers,
although it does not. It is a Freescale MPC5xxx embedded part.

e.g. when trying to debug the embedded target via Eclipse, I'm seeing
this:
(gdb) 
5624-data-list-register-names
5624^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7","r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18","r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29","r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9","f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20","f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31","pc","msr","cr","lr","ctr","xer","fpscr","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","vr0","vr1","vr2","vr3","vr4","vr5","vr6","vr7","vr8","vr9","vr10","vr11","vr12","vr13","vr14","vr15","vr16","vr17","vr18","vr19","vr20","vr21","vr22","vr23","vr24","vr25","vr26","vr27","vr28","vr29","vr30","vr31","vscr","vrsave","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","dl0","dl1","dl2","dl3","dl4","dl5","dl6","dl7","dl8","dl9","dl10","dl11","dl12","dl13","dl14","dl15"]
(gdb)

The target doesn't have that many registers and the remote debugger
returns an error code and drops the gdb connection if any are accessed.
I'd like gdb to only report the basic 32 GPRs and 8 specials.

I've searched online a fair bit and through the archives of this mailing
list without finding any obvious solutions.

The source appears to make reference to gdbarch determining whether
these features are enabled or not but I don't know how to use it.

I built the .elf file I'm debugging using gcc - are there any flag that
I should have set there that determine the vector register ABI that are
then used by gdb?

Any help appreciated.

regards

James Murray

Re: How to disable Altivec registers in powerpc GDB ?

[Yao Qi]

James Murray <james@nscc.info> writes:

> gdb appears to think that my target has the altivec vector registers,
> although it does not. It is a Freescale MPC5xxx embedded part.
>
> e.g. when trying to debug the embedded target via Eclipse, I'm seeing
> this:
> (gdb) 
> 5624-data-list-register-names
> 5624^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7","r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18","r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29","r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9","f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20","f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31","pc","msr","cr","lr","ctr","xer","fpscr","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","vr0","vr1","vr2","vr3","vr4","vr5","vr6","vr7","vr8","vr9","vr10","vr11","vr12","vr13","vr14","vr15","vr16","vr17","vr18","vr19","vr20","vr21","vr22","vr23","vr24","vr25","vr26","vr27","vr28","vr29","vr30","vr31","vscr","vrsave","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","dl0","dl1","dl2","dl3","dl4","dl5","dl6","dl7","dl8","dl9","dl10","dl11","dl12","dl13","dl14","dl15"]
> (gdb)
>
> The target doesn't have that many registers and the remote debugger
> returns an error code and drops the gdb connection if any are accessed.
> I'd like gdb to only report the basic 32 GPRs and 8 specials.

Your debug stub/probe should return the right target description for
your processor, to tell GDB that processor doesn't have these altivec
registers.  See
https://sourceware.org/gdb/current/onlinedocs/gdb/Target-Descriptions.html

-- 
Yao (齐尧)

Re: How to disable Altivec registers in powerpc GDB ?

[James Murray]

On Fri, 2015-05-01 at 14:56 +0100, Yao Qi wrote:
> Your debug stub/probe should return the right target description for
> your processor, to tell GDB that processor doesn't have these altivec
> registers.  See
> https://sourceware.org/gdb/current/onlinedocs/gdb/Target-Descriptions.html
> 

Many thanks for that.

I've created a target description from the examples in the gdb source
and then used:

set tdesc filename ppc32.xml

and it works!

regards

James Murray