From mboxrd@z Thu Jan 1 00:00:00 1970 From: ard.biesheuvel@linaro.org (Ard Biesheuvel) Date: Thu, 18 May 2017 10:09:53 +0100 Subject: [PATCH 3/3] efi/libstub: arm64: set -fpie when building the EFI stub In-Reply-To: <20170518090953.32628-1-ard.biesheuvel@linaro.org> References: <20170518090953.32628-1-ard.biesheuvel@linaro.org> Message-ID: <20170518090953.32628-4-ard.biesheuvel@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. Signed-off-by: Ard Biesheuvel --- 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 f7425960f6a5..e078390ba477 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 -- 2.9.3