Genode 16.05 Fault handler

[Sebastian Sumpf]

Hi Denis,

On 08/30/2016 04:21 PM, Denis Huber wrote:
> Hello Sebastian,
> 
> I created a new thread which causes the page fault, and also assigned an 
> extra Entrypoint for the Signal_handler [1], but still no success. 
> Perhaps I am using the Signal_handler in a wrong way.
> 
> [1] 
> https://github.com/702nADOS/genode-CheckpointRestore-SharedMemory/blob/c58b4144bff720f837112c590ebd2148e9c3f199/src/test/fault_handler/main.cc
> 

You are mixing some things up here, I pushed a working version of your
code (tested on Fisco.OC in Qemu) to GitHub:

https://github.com/ssumpf/genode/commit/0075a0026faa8079f03dfb4d43ec281ef51f1083

I hope this clarifies things a little. The relevant output should look
like this:

> [init -> pf-signal_handler] --- pf-signal_handler started ---
> no RM attachment (WRITE pf_addr=1000 pf_ip=10001d9 from 2d2000)
> Warning: could not resolve pf=0x1000 ip=0x10001d9
> [init -> pf-signal_handler]   Region map state is WRITE_FAULT pf_addr=0x1000
> [init -> pf-signal_handler]   Allocating dataspace and attaching it to the region map
> [init -> pf-signal_handler] --- pf-signal_handler ended ---

Sebastian

P.S. As I see it, you needed the 'join' because the thread was created
on the stack again ;) One has to use the heap or bss/data.


> Kinds regards,
> Denis
> 
> On 30.08.2016 15:45, Sebastian Sumpf wrote:
>> Hello again,
>>
>> I missed that part
>>
>>> *((unsigned int*)0x1000) = 1;
>>
>> in my last reply. You cannot cause a page fault in your entry point and
>> also handle it in the entry point thread, because the entry point is not
>> able to receive signals when it is in page fault. It is a hen and egg
>> problem.
>>
>> If you cause the fault from another Genode thread, it should work as
>> expected.
>>
>> Sebastian
>>
>>
>> On 08/30/2016 03:07 PM, Denis Huber wrote:
>>> Hello Sebastian,
>>>
>>> I moved sigh to the member attributes [1], but without success. I also
>>> tried to use a heap to store the Signal_handler, also without success.
>>>
>>> [1]
>>> https://github.com/702nADOS/genode-CheckpointRestore-SharedMemory/blob/93eaec436ce9b6d3b3a6663558bff9af925ae70f/src/test/fault_handler/main.cc#L19
>>>
>>> I am using run script [2], if it helps.
>>>
>>> [2]
>>> https://github.com/702nADOS/genode-CheckpointRestore-SharedMemory/blob/93eaec436ce9b6d3b3a6663558bff9af925ae70f/run/fault_handler.run
>>>
>>>
>>> Kind regards,
>>> Denis
>>>
>>> On 30.08.2016 14:36, Sebastian Sumpf wrote:
>>>> Hi Denis,
>>>>
>>>>> Signal_handler<Main> sigh = {env.ep(), *this, &Main::_handle_fault};
>>>>
>>>> The line above, creates the Signal_handler on the stack and destructs
>>>> this handler as soon as the 'Main' constructor is finished.
>>>>
>>>> Therefore, 'sigh' should be a member of the 'Main' class.
>>>>
>>>> Regards,
>>>>
>>>> Sebastian
>>>>
>>>> On 08/30/2016 02:10 PM, Denis Huber wrote:
>>>>> Dear Genode community,
>>>>>
>>>>> in Genode 16.05 the old usage of Signal_receivers and Signal_contexts is
>>>>> considered deprecated. Instead Signal_handler and Signal_transmitter
>>>>> shall be used.
>>>>>
>>>>> I am trying to use a Signal_handler as a fault handler for env's address
>>>>> space. I wrote a short test to illustrate the problem [1].
>>>>>
>>>>> [1]
>>>>> https://github.com/702nADOS/genode-CheckpointRestore-SharedMemory/blob/c9a5a1f999a2ce1c6ffd5c316eee127c93d87308/src/test/fault_handler/main.cc
>>>>>
>>>>> The output of [1] is as follows:
>>>>> "
>>>>> [init -> pf-signal_handler] --- pf-signal_handler started ---
>>>>> no RM attachment (WRITE pf_addr=1000 pf_ip=100061c from 2ae000)
>>>>> Genode::Pager_entrypoint::entry()::<lambda(Genode::Pager_object*)>:
>>>>> Could not resolve pf=1000 ip=100061c
>>>>> "
>>>>>
>>>>> The signal handler was registered correctly, because the line
>>>>> "
>>>>> Genode::Core_pd_session_component::submit(Genode::Capability<Genode::Signal_context>,
>>>>> unsigned int)::<lambda(Genode::Signal_context_component*)>: invalid
>>>>> signal-context capability
>>>>> "
>>>>> is missing. However, the method _handle_fault() is never entered. What
>>>>> am I doing wrong?
>>>>>
>>>>>
>>>>> Kind regards,
>>>>> Denis
>>>>>
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