Using Instruction Pointer address in debug interfaces [Was: Re: vm_page_t related KBI [Was: Re: panic at vm_page_wire with FreeBSD 9.0 Beta 3]]

Arnaud Lacombe lacombar at
Wed Nov 9 01:43:42 UTC 2011


On Tue, Nov 8, 2011 at 8:09 PM, Arnaud Lacombe <lacombar at> wrote:
> Hi,
> On Tue, Nov 8, 2011 at 3:55 PM, Andriy Gapon <avg at> wrote:
>> [cc list trimmed]
>> on 08/11/2011 22:34 Attilio Rao said the following:
>>> 2011/11/8 Arnaud Lacombe <lacombar at>:
>>>> To avoid future complaints about the fact that I would be only "talk"
>>>> without "action", I did implement what I suggested above. As it is
>>>> quite a large patch-set, I will not post it directly here, however, it
>>>> is available on github:
>>> I really think that this is way too dependent by the good health of
>>> your tool, thus that is highly fragile.
>>> However, you may have more luck by just the core of your kernel
>>> changes here, for comment and leave alone all the (ptr ->
>>> LOCK_FILE/LOCK_LINE conversion).
>>> Said that, I think this logic is too fragile and likely won't be as
>>> effective as __FILE__/__LINE__ in many cases.
>> I agree.
>> If we were able to somehow automatically, magically, easily and correctly
>> determine an instruction pointer of a caller, then it would make sense to ditch
>> explicit passing of __FILE__/__LINE__ arguments in favor of doing instruction
>> pointer decoding.
> again, no need for magic, this already exists, as the form of gcc[0]'s
> __builtin_return_address(0).
actually, this should be __builtin_return_address(1).

 - Arnaud

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