So if I'm understanding correctly, a useful hardening step would be to ensure that each dynamically linked library had it's own GOT & that the tables are marked as read-only once dynamic linking completes (i.e. you can't reach across dynamic boundaries to patch someone else's ifunc entries).
That would improve the supply chain security of code getting linked in somewhere but never executed.
EDIT: Or even better, perhaps ifunc should be implemented in a declarative fashion so that you can't just cause arbitrary code execution from each library you link against. That might be harder to implement at this point considering back compat, but probably is something that could be layered in over a longer time period (i.e. if you build any library with "declaratively linked ifunc" feature bit set, then the dynamic linker will force all linked libraries to have that feature flag or fail to launch).
That would improve the supply chain security of code getting linked in somewhere but never executed.
EDIT: Or even better, perhaps ifunc should be implemented in a declarative fashion so that you can't just cause arbitrary code execution from each library you link against. That might be harder to implement at this point considering back compat, but probably is something that could be layered in over a longer time period (i.e. if you build any library with "declaratively linked ifunc" feature bit set, then the dynamic linker will force all linked libraries to have that feature flag or fail to launch).