Christoffer Dall <[email protected]> writes:
> On Thu, Nov 20, 2014 at 04:55:14PM +0000, Alex Bennée wrote:
<snip>
>>
>> * ptrace(PTRACE_GETREGSET, NT_ARM_HW_WATCH)
>>
>> This is used by GDB to access the host details in debug-monitors.
>> However the ptrace API really wants you to attach to a process before
>> calling PTRACE_GETREGSET. Currently I've tried attaching to the
>> thread_id of the vCPU but this fails with EPERM, I suspect because
>> attaching to your own threads likely upsets the kernel.
>
> Can you confirm your suspicion? This seems like a rather good approach
> so we should really investigate why this doesn't work and explore ways
> to get it working.
>From ptrace_attach:
retval = -EPERM;
if (unlikely(task->flags & PF_KTHREAD))
goto out;
if (same_thread_group(task, current))
goto out;
I think this is what is triggering my EPERM. I'm going to dig into the
history of code around that bit. While I can see it might be undesirable
I'm not sure if it has to be verbotten...
--
Alex Bennée
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