Preventing preemption of 'protected' symbols in GNU ld 2.26

[Cary Coutant]

>>> Did you look at what the costs were in startup time and dirty pages by using
>>> copy relocations? What do you do if the size of the definition changes in a
>>> new version of the library?
>>
>> There wouldn't be a measurable cost in dirty pages; the copied objects
>> are simply allocated in bss in the executable.
>
> Wouldn't references to the symbol from within the .so need to be relocated to reference the now-canonical copy in the executable?

No, references from within the .so would have always used the GOT.
Non-protected global symbols in a shared library are still
pre-emptible, so they are always indirect, and there's always a
dynamic relocation for the GOT entry. Whether the prevailing
definition winds up in the executable or the shared library, the
dynamic loader still has to bind the symbol and apply the relocation.

-cary