Re: [Fwd: Fix arm_addr_bits_remove: 26-bit Thumb doesn't exist]

Re: [Fwd: Fix arm_addr_bits_remove: 26-bit Thumb doesn't exist]

[Nick Clifton]

Hi Fernando, Hi Ben,

> From: Ben Harris <bjh21@netbsd.org>
> 
> I haven't actually encountered this bug in reality yet, but it looks
> to me as if arm_addr_bits_remove() is bogus.  Specifically, it has a
> case for Thumb state in a 26-bit mode.  According to the ARM ARM
> (2nd Edition, section A8.1), no processor will support both 26-bit
> mode and thumb state at all, let alone at the same time.  I suspect
> this might be a noticeable problem when debugging SVC mode code,
> since then R15 will have its bottom bit set, which arm_pc_is_thumb()
> is likely to interpret as meaning the CPU is in Thumb state.
> 
> ChangeLog entry:
> 
> 2001-10-20  Ben Harris  <bjh21@netbsd.org>
> 
> 	* arm-tdep.c (arm_addr_bits_remove): Don't believe in 26-bit
> 	Thumb.

This looks like a reasonable patch to me.  I do not have the authority
to approve it, but I would certainly recommend it to the GDB
maintainers.

Cheers
        Nick

Re: [Fwd: Fix arm_addr_bits_remove: 26-bit Thumb doesn't exist]

[Fernando Nasser]

Thank you Nick and Richard.

I haven't heard anything on the contrary from Scott (native ARM)
so I will check this in later today or tomorrow.

Thanks for the patch Ben.

Regards to all,
Fernando


Nick Clifton wrote:
> 
> Hi Fernando, Hi Ben,
> 
> > From: Ben Harris <bjh21@netbsd.org>
> >
> > I haven't actually encountered this bug in reality yet, but it looks
> > to me as if arm_addr_bits_remove() is bogus.  Specifically, it has a
> > case for Thumb state in a 26-bit mode.  According to the ARM ARM
> > (2nd Edition, section A8.1), no processor will support both 26-bit
> > mode and thumb state at all, let alone at the same time.  I suspect
> > this might be a noticeable problem when debugging SVC mode code,
> > since then R15 will have its bottom bit set, which arm_pc_is_thumb()
> > is likely to interpret as meaning the CPU is in Thumb state.
> >
> > ChangeLog entry:
> >
> > 2001-10-20  Ben Harris  <bjh21@netbsd.org>
> >
> >       * arm-tdep.c (arm_addr_bits_remove): Don't believe in 26-bit
> >       Thumb.
> 
> This looks like a reasonable patch to me.  I do not have the authority
> to approve it, but I would certainly recommend it to the GDB
> maintainers.
> 
> Cheers
>         Nick

-- 
Fernando Nasser
Red Hat Canada Ltd.                     E-Mail:  fnasser@redhat.com
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Toronto, Ontario   M4P 2C9