bug#18784: Coultdn't compile emacs-24.4

[Stefan Monnier <monnier@IRO.UMontreal.CA>]

> There is a long history of Emacs catching up with kernel hardening
> in this area. It started with setting ADDR_NO_RANDOMIZE via Linux
> personality(2), then setting the NORANDEXEC flag with paxctl(1) or
> setfattr(1). Now it seems that we need -nopie in addition.

But what does "-nopie" mean?  IIUC it means "do not generate PIE code",
so it is a "double-level workaround": not only it doesn't directly fix the
problem we have with randomization but it doesn't directly disable
randomization either.

If OTOH "-nopie" means "indicate that the code should not be relocated
even if it looks like it's position independent", then it's only
a "single-level workaround", like the ADDR_NO_RANDOMIZE and friends.

> My impression is that these are all workarounds that don't address the
> real issue.

AFAIK the only way to address directly the underlying issue is to use
a portable dumper.  Until then we'll have to consider address
randomization as plain bugs that we need to fix with things like
ADDR_NO_RANDOMIZE.


        Stefan "who doesn't really believe in such hardening"