Is this related to the general panic discussed in freebsd-current?

[Werner Thie]

Hi all

With WITNESS disabled, the BeagleBone runs more or less ok, just had 
Python from ports coming up,

Python 2.7.3 (default, May  5 2013, 16:49:13)
[GCC 4.2.1 Compatible FreeBSD Clang 3.3 (trunk 178860)] on freebsd10

but closer looks showed, that ctypes fails to build because of

Undefined symbol "__clear_cache"

Googling does not reveal all to much, is this a problem connected with 
the ARM platform?

Thxs, Werner

On 5/6/13 1:47 PM, Andrew Turner wrote:
> On Sun, 5 May 2013 22:39:56 -0700
> Tim Kientzle <kientzle at freebsd.org> wrote:
>> Here's a version of stack_capture that allows a Clang-built
>> OABI kernel with WITNESS enabled to boot:
>>
>> /* In sys/arm/arm/stack_machdep.c */
>> static void
>> stack_capture(struct stack *st, u_int32_t *frame)
>> {
>>          vm_offset_t callpc;
>>
>>          stack_zero(st);
>>          while (INKERNEL(frame)) {
>>                  callpc = frame[1];
>>                  if (stack_put(st, callpc) == -1)
>>                          break;
>>                  frame = (u_int32_t *)(frame[0]);
>>          }
>> }
> It looks like this should work in most cases where fp and lr are next
> to each other (ip and sp are between them but doesn't need to be saved).
>>
>>
>>  From the above, it sounds like this should not be committed;
>> rather, we should fix Clang's OABI support to emit the right
>> frame layout.  I've not yet started to look through Clang to
>> try to figure out how to do that….  Any pointers?  ;-)
> Disable this stack unwind code? I'll fix the clang EABI issue and
> switch the ABI.
>
> Andrew
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