Preventing preemption of 'protected' symbols in GNU ld 2.26

[H.J. Lu]

On Thu, Mar 31, 2016 at 6:26 AM, Ramana Radhakrishnan
<ramana.gcc@googlemail.com> wrote:
> On Thu, Mar 31, 2016 at 1:52 AM, Jeff Law <law@redhat.com> wrote:
>> On 03/30/2016 06:40 PM, Cary Coutant wrote:
>>>>
>>>> It would help me immensely on the GCC side if things if you and Alan
>>>> could
>>>> easily summarize correct behavior and the impact if we were to just
>>>> revert
>>>> HJ's change.  A testcase would be amazingly helpful too.
>>>
>>>
>>> It looks like it's not just the one change. There's this patch:
>>>
>>>     https://gcc.gnu.org/ml/gcc-patches/2015-07/msg01871.html
>>>
>>> which took the idea that protected can still be pre-empted by a COPY
>>> relocation and extended it to three more targets that use COPY
>>> relocations.
>>>
>>> I wonder how many other patches have been based on the same
>>> misunderstanding?
>>
>> I don't think it was many -- I certainly recall the arm/aarch64 variant.
>> There may have been one other varasm.c change in this space or I might be
>> conflating it with the arm/aarch64 change.  Tracking those down is naturally
>> part of this work.
>
> The glibc tests elf/tst-protected1{a,b}.c also need to be reviewed at
> the same time.  IIUC, the reason the patch above went in were to fix
> failures on arm / aarch64 with those tests. I haven't yet worked out
> whether all this is the same issue.
>

These testcases show the problem between copy relocation and
protected data symbol.  I updated my program property extension
to GNU ABI to prevent copy relocation against protected data symbol:

https://sourceware.org/ml/gnu-gabi/2016-q1/msg00041.html

-- 
H.J.