On Mon, Apr 18, 2016 at 10:03 AM, Maciej W. Rozycki <ma...@imgtec.com> wrote: > On Mon, 18 Apr 2016, H.J. Lu wrote: > >> > Any testcase the takes the address of a protected visibility variable >> > defined in a shared library now can get the wrong answer, since you >> > can argue that any address outside the shared library is wrong >> > according to the gABI. >> >> What value should you get when taking an address of a function >> with protected visibility inside the shared library? Should it be >> pointed to the function body or its PLT entry in the executable >> which calls the function? > > I think it has to be an address within the shared library itself, that is > -- depending on the particular psABI -- either the function body or its > corresponding PLT entry in the DSO, but not in the main executable. The
Sorry, this isn't how function pointer works on x86. > reason is DSO code (also handcoded assembly) may reasonably expect to be > able to load the address with a PC-relative load-address type instruction > (ADDIUPC, LEA, MOVAB, etc.) and the target may not even have suitable > dynamic relocations available to apply any load-time fixup if the symbol > referred turns up outside of the DSO. The instruction used may have a > PC-relative range limit too. > That is why protected visibility is such a mess. -- H.J.
