LEON2 and C++ exception handling

[Mike Looijmans]

On 11-08-17 13:43, Mike Looijmans wrote:
> On 11-08-17 10:40, Sebastian Huber wrote:
>> On 11/08/17 10:36, Mike Looijmans wrote:
>>
>>> Now that we got RTEMS running from ROM on a LEON2, I'm running into the 
>>> issue that C++ exceptions don't work. Any "throw" results in a fatal 
>>> termination.
>>>
>>> A program that does something like:
>>>
>>> try {
>>>   throw std::exception();
>>> } catch (const std::exception& ex)
>>>   puts(ex.what());
>>> }
>>>
>>> results in a stack trace like this:
>>>
>>>
>>>   #0   0xf9404fcc   0x4000c5a8
>>>   #1   0x00079340   0x4000c608   <_CPU_Fatal_halt+0x8>
>>>   #2   0x0005497c   0x4000c668   <_Terminate+0x48>
>>>   #3   0x000535b8   0x4000c6d8   <rtems_fatal+0xc>
>>>   #4   0x0004a970   0x4000c738   <bsp_spurious_handler+0xc>
>>>   #5   0x00079588   0x4000c7a0
>>>   #6   0x00048720   0x40017ab8 <classify_object_over_fdes+0xd0>
>>>   #7   0x00048e78   0x40017bd0   <search_object+0x330>
>>>   #8   0x0004965c   0x40017c48   <_Unwind_Find_FDE+0x10c>
>>>   #9   0x00045f30   0x40017cb0   <uw_frame_state_for+0x3c>
>>>   #10  0x0004739c   0x40017d18   <uw_init_context_1+0x28>
>>>   #11  0x00047c44   0x400180f0 <_Unwind_RaiseException+0x10>
>>>   #12  0x0000b478   0x40018918   <__cxa_throw+0x58>
>>>
>>>
>>> Any tips on how to diagnose this? Or should I just give up on C++ exception 
>>> with RTEMS? 
>>
>> You must provide a window flush trap. Something is wrong with your trap 
>> table. It works with the standard BSPs.
>>
> 
> I use the same trap table as the other leon2 BSPs. In start.S I find:
> 
>    TRAP( 0x83, SYM(window_flush_trap_handler) ); ! 83 flush windows SW trap
> 
> So it looks like it's there and provided by RTEMS.
> 

Looking at the memory (trap table is the first thing in RAM in my BSP) while 
the application runs:

grmon2> dis 0x40000830
        0x40000830: a1480000  mov  %psr, %l0
        0x40000834: 2900012b  sethi  %hi(0x4AC00), %l4
        0x40000838: 81c52124  jmp  %l4 + 0x124
        0x4000083c: a6102083  mov  131, %l3

So this save the psr and jumps to 0x4AC00|0x124 which resolves to the trap 
handler:

0004ad24 <window_flush_trap_handler>:
SYM(window_flush_trap_handler):


So as far as I can see, the trap table is okay. Is there maybe some other 
entry/register/variable that my boot code needs to pass to RTEMS?


Kind regards,

Mike Looijmans
System Expert

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