RFC: PATCHES: Properly handle reference to protected data on x86
H.J. Lu
hjl.tools@gmail.com
Fri Mar 6 13:05:00 GMT 2015
On Thu, Mar 5, 2015 at 8:19 PM, Alan Modra <amodra@gmail.com> wrote:
> On Wed, Mar 04, 2015 at 03:26:10PM -0800, H.J. Lu wrote:
>> Protected symbol means that it can't be pre-emptied. It
>> doesn't mean its address won't be external. This is true
>> for pointer to protected function. With copy relocation,
>> address of protected data defined in the shared library may
>> also be external. We only know that for sure at run-time.
>> Here are patches for glibc, binutils and GCC to handle it
>> properly.
>>
>> Any comments?
>
> I'd like to see this pass some more tests. For example
>
> reference in non-PIC exe to var x
> protected visibility definition of x in libA
> protected visibility definition of x in libB
>
> I suspect you don't have this case correct, but congratulations if you
> do! Assuming libA is first on the breadth first search for libraries,
> then exe and libA ought to use the same x, but libB have its own x.
I believe my new testcases on hjl/pr17711 branch at
https://sourceware.org/git/?p=glibc.git;a=summary
covers those and they work correctly.
> In fact it would be good to prove that all variations of either a
> reference, a default visibility definition or a protected visibility
> definition worked in the exe plus two libs case.
>
You can git my branch a try on PPC. If PPC uses copy
relocation, it shouldn't be too hard to update PPC to make
it work.
--
H.J.
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