[Buildroot] [PATCH 3/6] package/Makefile.in: Use gcc spec files for PIE build flags

[Matthew Weber]

Thomas,
On Sun, Aug 12, 2018 at 2:41 AM Thomas Petazzoni
<thomas.petazzoni at bootlin.com> wrote:
>
> Hello,
>
> On Sat, 11 Aug 2018 22:55:47 -0500, Matthew Weber wrote:
>
> > I started to look at this tonight and if I understand the current
> > wrapper, it's solely working with cc/gcc.  If someone explicity uses
> > ld, the wrapper doesn't take affect? (I'll do a build tomorrow and
> > look at behavior, didn't have a linux machine handy tonight to check.
>
> We only wrap gcc/cc indeed. Packages should not call "ld" directly, as
> it breaks a bunch of other situations. For example, on mips64, using
> "ld" directly doesn't work as it needs to be passed the "machine
> emulation", which gcc does.
>
> So I don't think we need to wrap "ld", as ld shouldn't be used
> directly. The only packages that should use "ld" directly are things
> like the Linux kernel or bootloaders.
>

The current hardening approach is trying to cover the cases where
packages are still using ld directly and have other incompatible flags
set (static/shared/r).  I don't have the exact list but I believe
busybox is even one of those and others like valgrind, boost, etc who
use the "shared" flag and adding "pie" causes a compile failure.  So
we do still need to cover the ld case or go patch packages.

What I could do is move the cc1 spec file conditional add of PIE into
the wrapper.  Then leave the LDFLAGS as we have them and the
associated spec file that does a conditional add of "pie".  This would
prevent us from wrapping the ld tool and keep the existing wrapper
approach consistent.

Matt