Messages in this thread Patch in this message | | | Date | Mon, 21 Aug 2017 02:16:44 -0700 | From | tip-bot for Ard Biesheuvel <> | Subject | [tip:efi/core] efi/libstub/arm64: Set -fpie when building the EFI stub |
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Commit-ID: 91ee5b21ee026c49e4e7483de69b55b8b47042be Gitweb: http://git.kernel.org/tip/91ee5b21ee026c49e4e7483de69b55b8b47042be Author: Ard Biesheuvel <ard.biesheuvel@linaro.org> AuthorDate: Fri, 18 Aug 2017 20:49:37 +0100 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Mon, 21 Aug 2017 09:43:49 +0200
efi/libstub/arm64: Set -fpie when building the EFI stub
Clang may emit absolute symbol references when building in non-PIC mode, even when using the default 'small' code model, which is already mostly position independent to begin with, due to its use of adrp/add pairs that have a relative range of +/- 4 GB. The remedy is to pass the -fpie flag, which can be done safely now that the code has been updated to avoid GOT indirections (which may be emitted due to the compiler assuming that the PIC/PIE code may end up in a shared library that is subject to ELF symbol preemption)
Passing -fpie when building code that needs to execute at an a priori unknown offset is arguably an improvement in any case, and given that the recent visibility changes allow the PIC build to pass with GCC as well, let's add -fpie for all arm64 builds rather than only for Clang.
Tested-by: Matthias Kaehlcke <mka@chromium.org> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Matt Fleming <matt@codeblueprint.co.uk> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/20170818194947.19347-5-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org> --- drivers/firmware/efi/libstub/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index 37e24f5..cf81e6c 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -10,7 +10,7 @@ cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ -O2 \ -fPIC -fno-strict-aliasing -mno-red-zone \ -mno-mmx -mno-sse -cflags-$(CONFIG_ARM64) := $(subst -pg,,$(KBUILD_CFLAGS)) +cflags-$(CONFIG_ARM64) := $(subst -pg,,$(KBUILD_CFLAGS)) -fpie cflags-$(CONFIG_ARM) := $(subst -pg,,$(KBUILD_CFLAGS)) \ -fno-builtin -fpic -mno-single-pic-base
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