things to do for arch maintainers

[Roland McGrath]

> This may be appropriate because powerpc does not have a pc relative 
> reference to access __pointer_chk_guard_local and access via the 
> .got/.toc will fail if access is attemped before the got/toc are 
> relocated. But I wanted to verify this.

If you cannot access it safely in the first _dl_catch_error call in
startup, then leave the macros undefined.  I think the ld.so bootstrap
relocation will be complete before it's ever used.

> It is not clear what this change is really for, so it is difficult to 
> determine what is intended or required.

They make it harder to exploit buffer overruns to write useful addresses
into jmp_buf's PC values and have those result in attacker-chosen jumps.


Thanks,
Roland