[PATCH v3 5/5] csu: Move static pie self relocation later [BZ #27072]

[Szabolcs Nagy]

The 01/14/2021 08:26, H.J. Lu wrote:
> 
> We need to make sure that there are no RELATIVE relocations before
> _dl_relocate_static_pie is called.  The problems with i386 are
> 
> 1.  All calls to IFUNC functions must go through PLT.
> 2.  Calls to hidden functions CANNOT go through PLT in PIE since
> EBX used in PIE PLT may not be set up for local calls.
> 
> I think we should add a new attribute, attribute_hidden_ifunc
> which should be defined as
> 
> 1. __attribute__ ((visibility ("default"))) if in PIE on i386
> 2. __attribute__ ((visibility ("hidden"))) else
> 
> attribute_hidden_ifunc should be used on prototypes of all IFUNC
> functions.  This is similar to NO_HIDDEN_EXTERN_FUNC_IN_PIE.

so is it enough to declare ifuncs with such attribute?

e.g. would it work if memcpy is default visibility
in PIE libc.a but user code is static linking that
with non-pie caller?

do we have a way to track which functions may be
defined as ifunc? should we do that manually? or add
the attribute to every extern function declaration
within the libc?