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Re: [RFC] Using function clones for Pointer Bounds Checker


On Wed, May 14, 2014 at 1:18 AM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
> 2014-05-13 23:21 GMT+04:00 Jeff Law <law@redhat.com>:
>> On 05/13/14 02:38, Ilya Enkovich wrote:
>>>>>
>>>>> propagate constant bounds value and remove checks in called function).
>>>>
>>>>
>>>> So from a linking standpoint, presumably you have to mangle the
>>>> instrumented
>>>> caller/callee in some manner.  Right?  Or are you dynamically dispatching
>>>> somehow?
>>>
>>>
>>> Originally the idea was o have instrumented clone to have the same
>>> assembler name as the original function. Since instrumented code is
>>> fully compatible with not instrumented code, we always emit only one
>>> version. Usage of the same assembler name allows instrumented and not
>>> instrumented calls to look similar in assembler. It worked fine until
>>> I tried it with LTO where assembler name is used as a unique
>>> identifier. With linker resolutions files it became even more harder
>>> to use such approach. To resolve these issues I started to use new
>>> assembler name with postfix, but linked with the original name using
>>> IDENTIFIER_TRANSPARENT_ALIAS. It gives different assembler names for
>>> clones and originals during compilation, but both clone and original
>>> functions have similar name in output assembler.
>>
>> OK.  So if I read that correctly, it implies that the existence of bounds
>> information does not change the signature of the callee.   This is obviously
>> important for C++.
>>
>> Sounds like I need to sit down with the branch and see how this works in the
>> new scheme.
>
> Both mpx branch and Wiki
> (http://gcc.gnu.org/wiki/Intel%20MPX%20support%20in%20the%20GCC%20compiler)
> page are up-to-date now and may be tried out either in NOP mode or
> with simulator. Let me know if you have any troubles with using it.
>

I built it.  But "-fcheck-pointer-bounds -mmpx" doesn't generate
MPX enabled executable which runs on both MPX-enabled and
non MPX-enabled hardwares. I didn't see any MPX run-time library.

-- 
H.J.


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