Re: [PATCH] New option --enable-pie-programs

["H.J. Lu" <hjl.tools@gmail.com>]

On Thu, Nov 18, 2021 at 5:26 AM Siddhesh Poyarekar <siddhesh@gotplt.org> wrote:
>
> On 11/18/21 18:19, Adhemerval Zanella wrote:
> >
> >
> > On 18/11/2021 09:42, H.J. Lu via Libc-alpha wrote:
> >> On Thu, Nov 18, 2021 at 1:24 AM Siddhesh Poyarekar <siddhesh@gotplt.org> wrote:
> >>>
> >>> On 11/17/21 15:34, Siddhesh Poyarekar via Libc-alpha wrote:
> >>>> I suppose you're right.  That is current behaviour with
> >>>> --enable-static-pie too; wouldn't a similar argument hold for
> >>>> --enable-static-pie=no?  Or is the rationale in that case is that
> >>>> *static-pie* is disabled, not pie itself and hence the default PIE
> >>>> toolchain could get away with building PIE dynamic programs, just not
> >>>> static ones?
> >>>>
> >>>> I wonder if the clearer option is to have a new
> >>>> --enable-pie=<no|dynamic|yes/full>, where "no" disables PIE (even on
> >>>> default-PIE toolchains), "dynamic" enables PIE for dynamic programs and
> >>>> "full" or "yes" enables static-pie on architectures that support it,
> >>>> terminating with an error if it's not supported.  --enable-static-pie=no
> >>>> could then imply --enable-pie=dynamic and could be deprecated.  I don't
> >>>> remember if we have ever deprecated configure flags before.
> >>>>
> >>>> Even simpler, we could have just a yes/no option and enable static-pie
> >>>> transparently on architectures that support it, making an explicit
> >>>> --enable-static-pie=no equivalent to disabling all PIE.  It may in
> >>>> theory break a use case but I don't know if there's actually a use case
> >>>> where one would strictly want only dynamic PIE and not static PIE.
> >>>
> >>> A third option (as we discussed offlist yesterday) could be to always
> >>> build glibc dynamic programs as PIE as long as the toolchain supports
> >>> it.  Would non-distribution use cases be adversely affected by not
> >>> having an option to produce non-PIE glibc programs, e.g. iconvconfig,
> >>> getconf, etc.?
> >>
> >> How about --enable-default-pie?
>
> HJ, could you describe how you'd expect it to behave?  Would it map to
> any of the options I describe above?

--enable-default-pie builds all dynamic programs, including tests, as PIE.   If
compiler/target supports static PIE, it also builds static programs as PIE.

> > Another option would be to --enable-pie=<no,auto> where 'no' disables PIE
> > for both both static and dynamic installed programs and 'auto' checks
> > compiler support and enables for everything.  I would like to provide less
> > options which results in less permutations to test.
>
> OK, that sounds like the two option alternative I described above.
>
> Siddhesh



-- 
H.J.