Re: PATCH: PR gdb/13969: GDBserver doesn't check unsupported binary

[Pedro Alves <palves@redhat.com>]

On 04/12/2012 05:25 PM, H.J. Lu wrote:

> On Thu, Apr 12, 2012 at 8:57 AM, Pedro Alves <palves@redhat.com> wrote:
>> On 04/12/2012 04:37 PM, H.J. Lu wrote:
>>
>>> It doesn't work since x32 is a 32-bit process.  Although x32
>>> GDBserver can get registers of 64-bit process,  it can't handle 64-bit address
>>
>>> in 64b-bit process, like setting break points.
>>
>> Oh yeah...  PowerPC has PPC_PTRACE_PEEKDATA_3264/PPC_PTRACE_POKEDATA_3264
>> for that, but well, it's PowerPC specific.
>>
> 
> Also x32 siginfo is different from 64bit signfo. X32 ptrace can't get 64bit
> siginfo due to address fields in siginfo.


Are you certain about that?  With a 64-bit debugger vs 32-bit process,
PTRACE_GETSIGINFO returns the siginfo in 64-bit layout.  I could see the
kernel returning 64-bit siginfo for x32 too (it's a question of whether
the kernel returns its native layout, or the debugger's).

In the 64x32 case, GDB has to go through contortions to
translate the siginfo layout (in both directions), for the
$_siginfo convenience variable's support.  This ends up needing to
replicate what the kernel's compat layer does.  IMO, a PTRACE_
method that always returned the siginfo object in the layout of the
inferior would be nice.

-- 
Pedro Alves