Make __start/__stop symbols protected visibility

[H.J. Lu]

On Tue, Aug 22, 2017 at 1:04 AM, Alan Modra <amodra@gmail.com> wrote:
> On Mon, Aug 21, 2017 at 05:29:14AM -0700, H.J. Lu wrote:
>> When SYMBOLIC_BIND is set, protected visibility no longer make any
>> senses.
>
> I already explained why __start_section and __stop_section symbols
> ought to be protected visibility.  You want a symbol that is visible
> to other modules but resolves locally.  That is exactly what the gABI
> says of protected visibility.
>
> STV_PROTECTED
>     A symbol defined in the current component is protected if it is
>     visible in other components but not preemptable..
>
> So by making these linker defined symbols protected visibility, the
> object itself documents their binding.

STV_PROTECTED is meaningful only if there is a dynamic relocation.
When the relocation is already resolved by the linker at run-time via
SYMBOLIC_BIND, the symbol is not preemptable regardless if it is
STV_PROTECTED or not.


-- 
H.J.