Preventing preemption of 'protected' symbols in GNU ld 2.26

[Cary Coutant]

> 2) Emit dynamic text relocations for non-PIC executable access to
> protected visibility variables defined in shared libraries.  Makes
> executable pages with text relocations non-shared between processes.
> (But can be shared again after relocation if two processes have the
> same layout.)

Note that this is not always possible, depending on the addressing
range of the code emitted. For example, a pc-relative access may have
sufficient range to reach a variable copied into the executable's bss,
but not sufficient range to reach the original definition in a shared
library.

-cary