[PATCH] Makefile: fix u-boot-initial-env target if lto is enabled

[Max Krummenacher]

Hi Tom

On Tue, Oct 18, 2022 at 7:57 PM Tom Rini <trini at konsulko.com> wrote:
>
> On Tue, Oct 18, 2022 at 07:48:27PM +0200, Max Krummenacher wrote:
> > From: Max Krummenacher <max.krummenacher at toradex.com>
> >
> > With LTO enabled the U-Boot initial environment is no longer stored
> > in an easy accessible section in env/common.o. I.e. the section name
> > changes from build to build, its content maybe compressed and it is
> > annotated with additional data.
> >
> > For GCC adding the option '-ffat-lto-objects' when compiling common.o
> > adds additionally the traditional sections in the object file and
> > 'make u-boot-initial-env' would work also for the LTO enabled case.
> > However clang doesn't have that option.
> >
> > Fix this by recompiling common.o into a object file only used for
> > the creation of u-boot-initial-env if LTO is enabled.
> >
> > See also:
> > https://lore.kernel.org/all/927b122e-1f62-e790-f5ca-30bae4332c77@foss.st.com/
> >
> > Signed-off-by: Max Krummenacher <max.krummenacher at toradex.com>
> >
> > ---
> >
> >  Makefile | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/Makefile b/Makefile
> > index 3866cc62f9a..cd45c720d23 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -2451,9 +2451,17 @@ endif
> >       $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
> >
> >  quiet_cmd_genenv = GENENV  $@
> > +ifeq ($(LTO_ENABLE),y)
> > +cmd_genenv = $(CC) $(filter-out $(LTO_CFLAGS),$(c_flags)) -c -o env/initial_env.o env/common.c; \
> > +     $(OBJCOPY) --dump-section .rodata.default_environment=$@ env/initial_env.o; \
> > +     sed --in-place -e 's/\x00/\x0A/g' $@; sed --in-place -e '/^\s*$$/d' $@; \
> > +     sort --field-separator== -k1,1 --stable $@ -o $@; \
> > +     rm -f env/initial_env.o env/initial_env.su
> > +else
> >  cmd_genenv = $(OBJCOPY) --dump-section .rodata.default_environment=$@ env/common.o; \
> >       sed --in-place -e 's/\x00/\x0A/g' $@; sed --in-place -e '/^\s*$$/d' $@; \
> >       sort --field-separator== -k1,1 --stable $@ -o $@
> > +endif
> >
> >  u-boot-initial-env: u-boot.bin
> >       $(call if_changed,genenv)
>
> Can we pipe the output instead of making a new object file? Maybe not,
> in a portable way it seems. But, I'm not sure the above respects using
> O= as well so that does need to be checked and fixed if so.

While I didn't test it seems that objcopy doesn't allow to pipe data in and out
of it.

Max
>
> --
> Tom