Re: [PATCH v3 3/3] or1k: gcc: initial support for openrisc

[Stafford Horne <shorne at gmail dot com>]

On Mon, Nov 05, 2018 at 10:10:22AM -0500, Rich Felker wrote:
> On Mon, Nov 05, 2018 at 11:13:53AM +0000, Szabolcs Nagy wrote:
> > On 04/11/18 09:05, Stafford Horne wrote:
> > > On Mon, Oct 29, 2018 at 02:28:11PM +0000, Szabolcs Nagy wrote:
> > >> On 27/10/18 05:37, Stafford Horne wrote:
> > ...
> > >>> +#undef LINK_SPEC
> > >>> +#define LINK_SPEC "%{h*}			\
> > >>> +   %{static:-Bstatic}				\
> > >>> +   %{shared:-shared}				\
> > >>> +   %{symbolic:-Bsymbolic}			\
> > >>> +   %{!static:					\
> > >>> +     %{rdynamic:-export-dynamic}		\
> > >>> +     %{!shared:-dynamic-linker " GNU_USER_DYNAMIC_LINKER "}}"
> > >>> +
> > >>> +#endif /* GCC_OR1K_LINUX_H */
> > >>
> > >> note that because of the -static-pie mess each
> > >> target needs a more complicated LINK_SPEC now.
> > > 
> > > Hello,
> > > 
> > > Does something like this look better?
> > > 
> > > --- a/gcc/config/or1k/linux.h
> > > +++ b/gcc/config/or1k/linux.h
> > > @@ -37,8 +37,9 @@
> > >     %{static:-Bstatic}                          \
> > >     %{shared:-shared}                           \
> > >     %{symbolic:-Bsymbolic}                      \
> > > -   %{!static:                                  \
> > > +   %{!static:%{!static-pie:                    \
> > >       %{rdynamic:-export-dynamic}               \
> > > -     %{!shared:-dynamic-linker " GNU_USER_DYNAMIC_LINKER "}}"
> > > +     %{!shared:-dynamic-linker " GNU_USER_DYNAMIC_LINKER "}}} \
> > > +   %{static-pie:-Bstatic -pie --no-dynamic-linker -z text}"
> > >  
> > >  #endif /* GCC_OR1K_LINUX_H */
> > 
> > looks ok.
> > 
> > > I have tested this out with or1k-linux-musl, but I get some LD complaints i.e.
> > > 
> > > .../or1k-linux-musl/bin/ld: .../or1k-linux-musl/lib/libc.a(exit.o): non-pic relocation against symbol __fini_array_end
> > > .../or1k-linux-musl/bin/ld: .../or1k-linux-musl/lib/libc.a(exit.o): non-pic relocation against symbol __fini_array_start
> > > 
> > > Those are some warnings we recently added to LD, perhaps I need to rebuild the
> > > libc.a with PIE as well.  I will try it out, but if anyone has some suggestions
> > > that would be helpful.
> > 
> > yes, musl does not build libc.a with pic by default,
> > either use a gcc configured with --enable-default-pie
> > or CC='gcc -fPIC' when building musl.
> > 
> > after that -static-pie linking should work.
> > 
> > (maybe musl should have an --enable-static-pie config
> > option to make this simpler)
> 
> For practical purposes, if you want to use static pie, you need a
> default-pie toolchain. This is because _every_ static lib you might
> link needs to be built with -fPIE (or -fPIC), and ensuring that
> happens on a package-by-package basis is largely impractical; at least
> it's on the same order of magnitude of difficulty as other systems
> integration/packaging tasks.

Thanks, I kind of figured it out, but it was no so clear when I started.

> However from the musl side it might make sense to produce a libc_pic.a
> as part of the build process. This would make it easy to replace
> libc.a with libc_pic.a if desired, and could also be used as the basis
> for linking libc.so and to allow production of a stripped-down libc.so
> that only includes symbols a fixed set of binaries depend on. We could
> discuss something like this on the musl list.

That makes sense.

Thanks Rich for your input.

-Stafford