RE: [PATCH] gdbserver: try selecting a thread first to access memory

["Aktemur, Tankut Baris" <tankut.baris.aktemur@intel.com>]

On Tuesday, July 18, 2023 4:03 PM, Pedro Alves wrote:
> On 2023-07-18 14:36, Aktemur, Tankut Baris wrote:
> > On Tuesday, July 18, 2023 3:09 PM, Pedro Alves wrote:
> 
> [ snip answers; thanks! ]
> 
> >> I'm wondering whether we should have something like:
> >>
> >>   if ((aspace_thread_specific (...) && set_desired_thread ())
> >>       || set_desired_process ())
> >>      res = read_inferior_memory (memaddr, myaddr, len);
> >>   else
> >>      res = 1;
> >
> > I believe `aspace_thread_specific` would have to be a target-specific
> > logic.
> 
> Right.
> 
> > What you referred to in the comment [1] above, i.e.  "immediately
> > exposed to the problem scenario and is forced to fix it", would be caught
> > and the target would fix the problem by implementing `aspace_thread_specific`
> > appropriately.  This makes sense to me.
> 
> Exactly.
> 
> > An alternative would be that
> > the target calls `set_desired_thread` itself, before accessing the memory,
> > if it detects that the request is thread-specific.  I don't see any low-target
> > using `set_desired_thread` ever in the gdbserver codebase, though.  So, it
> > might be considered a breakage of abstraction.  Hence, your suggestion looks
> > favorable.
> 
> Yeah, that'd be an abstraction violation.  Ideally, the gdbserver backends would
> have no RSP awareness at all, and would even be reusable by GDB.
> Many years ago, the abstraction didn't exist as it does today, and the backends
> would even peek into the remote protocol message buffer.  That was all separated
> out with the non-stop and multi-process work, IIRC, where gdbserver migrated to a
> target_ops interface similar to GDB's.

Ack. 

I'll revise the patch accordingly and send an update as soon as I can.

Thanks
-Baris


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