Re: [PATCH 03/19] efi/libstub: Use hidden visiblity for all source files

[Atish Patra <Atish.Patra@wdc.com>]

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@kernel.org>
> ---
>  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@redhat.com>
>   */
>  
> -/*
> - * 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.


-- 
Regards,
Atish