On Tue, 25 Feb 2020 at 00:15, Atish Patra <Atish.Patra@xxxxxxx> wrote:
>
> On Mon, 2020-02-10 at 17:02 +0100, Ard Biesheuvel wrote:
> > Instead of setting the visibility pragma for a small set of symbol
> > declarations that could result in absolute references that we cannot
> > support in the stub, declare hidden visibility for all code in the
> > EFI stub, which is more robust and future proof.
> >
> > To ensure that the #pragma is taken into account before any other
> > includes are processed, put it in a header file of its own and
> > include it via the compiler command line using the -include option.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> > ---
> > arch/arm64/include/asm/efi.h | 3 ---
> > drivers/firmware/efi/libstub/Makefile | 2 +-
> > drivers/firmware/efi/libstub/arm64-stub.c | 8 +-------
> > drivers/firmware/efi/libstub/hidden.h | 6 ++++++
> > 4 files changed, 8 insertions(+), 11 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/efi.h
> > b/arch/arm64/include/asm/efi.h
> > index 44531a69d32b..56ae87401a26 100644
> > --- a/arch/arm64/include/asm/efi.h
> > +++ b/arch/arm64/include/asm/efi.h
> > @@ -107,9 +107,6 @@ static inline void free_screen_info(struct
> > screen_info *si)
> > {
> > }
> >
> > -/* redeclare as 'hidden' so the compiler will generate relative
> > references */
> > -extern struct screen_info screen_info
> > __attribute__((__visibility__("hidden")));
> > -
> > static inline void efifb_setup_from_dmi(struct screen_info *si,
> > const char *opt)
> > {
> > }
> > diff --git a/drivers/firmware/efi/libstub/Makefile
> > b/drivers/firmware/efi/libstub/Makefile
> > index f14b7636323a..4efdbd711e8e 100644
> > --- a/drivers/firmware/efi/libstub/Makefile
> > +++ b/drivers/firmware/efi/libstub/Makefile
> > @@ -25,7 +25,7 @@ cflags-$(CONFIG_ARM) := $(subst
> > $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
> > cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt
> >
> > KBUILD_CFLAGS := $(cflags-y)
> > -DDISABLE_BRANCH_PROFILING \
> > - -D__NO_FORTIFY \
> > + -include hidden.h -D__NO_FORTIFY \
> > $(call cc-option,-ffreestanding) \
> > $(call cc-option,-fno-stack-
> > protector) \
> > -D__DISABLE_EXPORTS
> > diff --git a/drivers/firmware/efi/libstub/arm64-stub.c
> > b/drivers/firmware/efi/libstub/arm64-stub.c
> > index 2915b44132e6..719d03a64329 100644
> > --- a/drivers/firmware/efi/libstub/arm64-stub.c
> > +++ b/drivers/firmware/efi/libstub/arm64-stub.c
> > @@ -6,17 +6,11 @@
> > * Adapted from ARM version by Mark Salter <msalter@xxxxxxxxxx>
> > */
> >
> > -/*
> > - * To prevent the compiler from emitting GOT-indirected (and thus
> > absolute)
> > - * references to the section markers, override their visibility as
> > 'hidden'
> > - */
> > -#pragma GCC visibility push(hidden)
> > -#include <asm/sections.h>
> > -#pragma GCC visibility pop
> >
> > #include <linux/efi.h>
> > #include <asm/efi.h>
> > #include <asm/memory.h>
> > +#include <asm/sections.h>
> > #include <asm/sysreg.h>
> >
> > #include "efistub.h"
> > diff --git a/drivers/firmware/efi/libstub/hidden.h
> > b/drivers/firmware/efi/libstub/hidden.h
> > new file mode 100644
> > index 000000000000..3493b041f419
> > --- /dev/null
> > +++ b/drivers/firmware/efi/libstub/hidden.h
> > @@ -0,0 +1,6 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * To prevent the compiler from emitting GOT-indirected (and thus
> > absolute)
> > + * references to any global symbols, override their visibility as
> > 'hidden'
> > + */
> > +#pragma GCC visibility push(hidden)
>
> I am getting following compiler errors because of this patch while
> cross compiling for ARM, ARM64 and RISC-V.
>
> cc1: fatal error: hidden.h: No such file or directory
>
> Adding the following line to cflags solves the issue which indicates
> that gcc is not looking at the source file directory for this
> particularly include file.
>
> -I$(srctree)/drivers/firmware/efi/libstub
>
> I might have some trick in my build setup. Just posting here to see if
> anybody else also seeing the same problem.
>
Thanks Atish. Heinrich reported the same issue. It didn't affect me or
any of the bots because it only hits if you build in-tree (i.e.,
$srctree == $objtree)
My latest efi/next branch carries a fix for this (similar to your
suggestion, but using -include)
