Copy relocations against protected symbols

[H.J. Lu]

On Thu, Dec 18, 2014 at 2:13 PM, Alan Modra <amodra@gmail.com> wrote:
> On Thu, Dec 18, 2014 at 11:02:59AM -0800, H.J. Lu wrote:
>> Adding glibc.
>>
>> On Thu, Dec 18, 2014 at 10:52 AM, Cary Coutant <ccoutant@google.com> wrote:
>> >> Should we simply disallow creating DSO with protected data on targets
>> >> with copy relocation?
>> >
>> > I don't think so. Protected symbols are useful, and their presence
>>
>> As soon as they are used in executable, the program will misbehave.
>
> Not if the references in the executable are in code compiled with
> -fPIC.  I agree with Cary, disallowing protected visibility variables

It only works with -fPIC, not -fPIE when GCC 5 is used:

https://gcc.gnu.org/ml/gcc-patches/2014-12/msg00428.html

Are we suggesting we should compile PIE with -fPIC now?

> in shared libraries, or disabling the compiler optimisation that
> allows shared library code to access protected variables without a GOT
> indirection, is too big a hammer.


-- 
H.J.