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efi/libstub: Use hidden visibility for all source files

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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>
This commit is contained in:
Ard Biesheuvel 2020-02-10 17:02:32 +01:00
parent 04a7d0e156
commit 6f05106e20
4 changed files with 8 additions and 10 deletions
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3
arch/arm64/include/asm/efi.h
View File

@ -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)
{
}

1
drivers/firmware/efi/libstub/Makefile
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@ -25,6 +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 \
-include $(srctree)/drivers/firmware/efi/libstub/hidden.h \
-D__NO_FORTIFY \
$(call cc-option,-ffreestanding) \
$(call cc-option,-fno-stack-protector) \

8
drivers/firmware/efi/libstub/arm64-stub.c
View File

@ -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"

6
drivers/firmware/efi/libstub/hidden.h Normal file
View File

@ -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)