On Fri, Jun 17, 2011 at 07:30:43AM -0700, Ian Lance Taylor wrote: > Jack Howarth <howa...@bromo.med.uc.edu> writes: > > > What is the current state of supporting hardened operating systems > > that default to -fpie/-fPIE/-pie in gcc trunk? Do those releases still use > > their own patches for gcc or has all of those changes been committed to gcc > > trunk? > > If so, does anyone recall the specific commits? In particular, I am > > interested > > in any fixes to boehm-gc, libffi and pch to support PIE. > > I know there are variants of gcc out there which default to -fPIE when > compiling and -pie when linking. As far as I know there is no support > for that in trunk, unless you count the --with-specs configure option > which may be used to implement these defaults. > > I don't see why -pie should make any difference for boehm-gc or libffi. > Is there some known problem with them?
On darwin11, we see crashes in the boehm-gc testsuite as well as in ecj1 when linked as -pie. I'll try a test under x86_64 Fedora 15 this weekend of building with the same -fPIC default as darwin uses but inverting what we added this week to mh-darwin for linux so that FSF gcc is built with... BOOT_LDFLAGS += -Wl,-pie Hopefully linux allows pie executables to be created from -fPIC object files like on darwin. > > For PCH what matters is not whether gcc defaults to generating PIE, but > whether gcc itself is compiled as a PIE. In general I believe that a > PIE gcc will not support PCH--it will work most of the time, but will > occasionally fail. However, I have not actually tested this. If I'm > right about this limitation, it would be quite difficult to fix given > the current PCH implementation. Fortunately, as far as I can see, the > kind of attacks which PIE protects against are unimportant when > attacking gcc, as gcc simply runs under your own user ID on your own > system. Anything the user can somehow suborn gcc into doing, the user > can do anyhow. So I see no reason to build gcc as a PIE. Of course > those considerations would change if somebody is running a compilation > server on the net which invokes gcc; such a setup might get some small > benefit from building gcc as a PIE, but such a setup would be unlikely > to support PCH in any case. > > Ian
