On Wed, 27 May 2020 at 20:29, Brian Gerst <brgerst@xxxxxxxxx> wrote: > > On Wed, May 27, 2020 at 2:08 PM Arvind Sankar <nivedita@xxxxxxxxxxxx> wrote: > > > > On Sat, May 23, 2020 at 02:00:20PM +0200, Ard Biesheuvel wrote: > > > Eliminate all GOT entries in the decompressor binary, by forcing hidden > > > visibility for all symbol references, which informs the compiler that > > > such references will be resolved at link time without the need for > > > allocating GOT entries. > > > > > > To ensure that no GOT entries will creep back in, add an assertion to > > > the decompressor linker script that will fire if the .got section has > > > a non-zero size. > > > > > > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> > > > --- > > > arch/x86/boot/compressed/Makefile | 1 + > > > arch/x86/boot/compressed/hidden.h | 19 +++++++++++++++++++ > > > arch/x86/boot/compressed/vmlinux.lds.S | 1 + > > > 3 files changed, 21 insertions(+) > > > > > > diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile > > > index 5f7c262bcc99..aa9ed814e5fa 100644 > > > --- a/arch/x86/boot/compressed/Makefile > > > +++ b/arch/x86/boot/compressed/Makefile > > > @@ -40,6 +40,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, gnu) > > > KBUILD_CFLAGS += -Wno-pointer-sign > > > KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) > > > KBUILD_CFLAGS += -fno-asynchronous-unwind-tables > > > +KBUILD_CFLAGS += -include hidden.h > > > > > > > Ard, from the other thread [1] in case you missed it -- the plain > > hidden.h fails to build in-tree. We need something like > > KBUILD_CFLAGS += -include $(srctree)/$(src)/hidden.h > > instead. > > > > [1] https://lore.kernel.org/lkml/20200526153104.GC2190602@xxxxxxxxxxxxxxxxxx/ > > How about using -fvisibility=hidden instead of including this header? > That only works for definitions, not for extern declarations.
