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Re: Debugging arm-eabi - no stack frame?


Nick Garnett wrote:

>> I am unable to do any backtraces (the emulator barfs
>> at trying to access adresses 0xfffffffc - f).
> 
> Exactly how does it barf?

Bus read error, can not find corresponding bank for addr 0xfffffffc,pc=0x80000dfc
Bus read error, can not find corresponding bank for addr 0xfffffffd,pc=0x80000dfc
Bus read error, can not find corresponding bank for addr 0xfffffffe,pc=0x80000dfc
Bus read error, can not find corresponding bank for addr 0xffffffff,pc=0x80000dfc

I tried to alter values returned by the emulator for invalid memory,
this did not help.

The access itself is not a problem, the emulator informs
me of it, but does not generate any exception or such, it simply
returns something.

> GDB has a somewhat nasty heuristic to try and do backtraces in the
> presence of compiler optimization. To do this it may access memory by
> treating values it finds on the stack and in registers as
> pointers. Sometimes these will point at invalid locations.

OK, this is certainly a possibility. However, its heuristics
seems to fail:

(gdb) where
#0  test1 () at nxttests.cxx:34
#1  0x00000000 in ?? ()

i.e. it does not even know that the test1() was called from main()
The #1 address varies according to what the "invalid" access returns.

There is no -O in my compilation flags.

> When debugging via RedBoot there are mechanisms to prevent it making
> these accesses if they can cause problems. RedBoot can also catch
> memory access execptions and generate a proper response. Perhaps
> skyeye's gdbserver has similar mechanisms.

Thanks for the hint, I'll investigate.


Thanks
-- 
                                     Stano

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