svn commit: r267233 - in head: . bin/rmail gnu/usr.bin/binutils/addr2line gnu/usr.bin/binutils/nm gnu/usr.bin/binutils/objcopy gnu/usr.bin/binutils/objdump gnu/usr.bin/binutils/readelf gnu/usr.bin/...

[Konstantin Belousov]

On Sun, Jun 08, 2014 at 12:14:15PM -0700, Alfred Perlstein wrote:
> On 6/8/14 11:44 AM, Konstantin Belousov wrote:
> > On Sun, Jun 08, 2014 at 11:30:42AM -0700, Alfred Perlstein wrote:
> >> On 6/8/14 11:27 AM, Konstantin Belousov wrote:
> >>> On Sun, Jun 08, 2014 at 05:38:49PM +0000, Bjoern A. Zeeb wrote:
> >>>> On 08 Jun 2014, at 17:29 , Bryan Drewery <bdrewery at FreeBSD.org> wrote:
> >>>>
> >>>>> Author: bdrewery
> >>>>> Date: Sun Jun  8 17:29:31 2014
> >>>>> New Revision: 267233
> >>>>> URL: http://svnweb.freebsd.org/changeset/base/267233
> >>>>>
> >>>>> Log:
> >>>>>    In preparation for ASLR [1] support add WITH_PIE to support building with -fPIE.
> >>>>>
> >>>>>    This is currently an opt-in build flag. Once ASLR support is ready and stable
> >>>>>    it should changed to opt-out and be enabled by default along with ASLR.
> >>>>>
> >>>>>    Each application Makefile uses opt-out to ensure that ASLR will be enabled by
> >>>>>    default in new directories when the system is compiled with PIE/ASLR. [2]
> >>>>>
> >>>>>    Mark known build failures as NO_PIE for now.
> >>>> No, no, no, no more NOs!
> >>>>
> >>>> I?ll leave it to others who understand the current build system in days when it?s not broken to fix this entire splattering across all these Makefiles;  we really need a better way for this.
> >>> I have no words to express my dissatisfaction with this commit.
> >>> If change to the build of _some_ usermode binaries require patching
> >>> of loader', csu and rtld Makefiles, obviously it is done wrong.
> >>>
> >>> Why almost half of the binaries require opt-out ?
> >>>
> >>> PLEASE REVERT THIS.
> >> Wait.  Does this not serve as a useful stake in the ground for people to
> >> come in and update things?  Instead of asking to back out, shouldn't we
> >> be doing an announcement "ok folks, it's now time to fix this!" and move
> >> forward?  Otherwise we may never get any pie.
> > Let me reformulate.
> >
> > Somebody commits broken change, despite it was pointed out by many
> > before the commit. From the changes it is obvious that people which
> > proposed it do not understand what they hack on. And then, somebody else
> > must run and 'fix' previously non-broken code.
> >
> > Sure, you get the pie.
> Sure, but hasn't the default stayed unchanged?
No, they were changed, in very buggy and unuseful way, which is indicated
by the need to modify the Makefiles for the completely unrelated things
which I listed before.

The change modified the VA layout of all affected binaries, and also
added overhead of relocation to the previously fixed-mapped binaries.
> 
> It seems like you have to enable ASLR first before you see all the 
> breakage.  Right now it seems like goal was to document what even 
> compiles versus doesn't compile with ASLR.  Afaik there is not setting 
> of ASLR on by default.
The change of binaries to the shared objects, which was done by the
discussing commit, is not about ASLR.  It is required to get that
snake oil to function, but by itself it is not ASLR.

And no, it is not about what works/does not work with ASLR. Seemingly,
it is about what the authors were able to mangle, or not able. E.g.,
FreeBSD cannot execute static 'binaries' compiled with PIE, since our
csu does not perform relocations. So whatever is changed by a knob to
become static (WITHOUT_SHARED_ROOT or how is it called now) is plain
broken after the commit, if the knob is tweaked. Similarly, if something
becomes shared-linked by knob (WITHOUT_STATIC_TOOLCHAIN ?) the NO_PIE is
not needed.

That said, the change is wrong on its principle.

> 
> There has to be a way to call out what works and what doesn't work and 
> form a transition from a world with no ASLR to one with some ASLR and 
> eventually one with almost entirely ASLR coverage.  I'm not sure it can 
> be done in one fell swoop.  Hooks like this in -current allow for this 
> to be done as a group effort.
> 
> It would be very unlikely that we retain the semantics all the way until 
> a -stable release.

I do not understand this two paragraphs at all.

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