Re: [PATCH] Fix PTRACE_GETREGSET failure for compat inferiors on arm64

[Yao Qi <qiyaoltc@gmail.com>]

On Fri, Dec 2, 2016 at 11:08 PM, Kees Cook <keescook@chromium.org> wrote:
>>> diff --git a/gdb/arm-linux-nat.c b/gdb/arm-linux-nat.c
>>> index d11bdc6..2126cd7 100644
>>> --- a/gdb/arm-linux-nat.c
>>> +++ b/gdb/arm-linux-nat.c
>>> @@ -384,17 +384,19 @@ arm_linux_fetch_inferior_registers (struct target_ops *ops,
>>>    if (-1 == regno)
>>>      {
>>>        fetch_regs (regcache);
>>> -      fetch_fpregs (regcache);
>>
>> We should only call fetch_fpregs if tdep->have_fpa_registers is true.
>
> I couldn't determine how this was handled. What actually sets
> org.gnu.gdb.arm.fpa in tdesc? I found gdb/features/arm/arm-fpa.xml and
> seems to imply it's always included with arm? I wasn't able to follow,
> but it seemed like _having_ VFP was a indicator that FPA wasn't used.
>

What is I meant is that instead of calling fetch_fpregs unconditionally,
we call fetch_fpregs if tdep->have_fpa_registers is true, like this,

  if (tdep->have_fpa_registers)
     fetch_fpregs (regcache);

IOW, we only fetch FPA registers if we know FPA registers are available,
as described in target description.

-- 
Yao (齐尧)