On Thu, Dec 17, 2020 at 04:24:32PM -0800, 'Nick Desaulniers' via Clang Built Linux wrote:
With GNU binutils 2.35+, linking with BFD produces warnings for vmlinux: aarch64-linux-gnu-ld: warning: -z norelro ignored
BFD can produce this warning when the target emulation mode does not support RELRO program headers, and -z relro or -z norelro is passed.
Alan Modra clarifies: The default linker emulation for an aarch64-linux ld.bfd is -maarch64linux, the default for an aarch64-elf linker is -maarch64elf. They are not equivalent. If you choose -maarch64elf you get an emulation that doesn't support -z relro.
The ARCH=arm64 kernel prefers -maarch64elf, but may fall back to -maarch64linux based on the toolchain configuration.
LLD will always create RELRO program header regardless of target emulation.
To avoid the above warning when linking with BFD, pass -z norelro only when linking with LLD or with -maarch64linux.
Cc: Alan Modra amodra@gmail.com Cc: Fāng-ruì Sòng maskray@google.com Fixes: 3b92fa7485eb ("arm64: link with -z norelro regardless of CONFIG_RELOCATABLE") Reported-by: kernelci.org bot bot@kernelci.org Reported-by: Quentin Perret qperret@google.com Acked-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Nick Desaulniers ndesaulniers@google.com
Reviewed-by: Nathan Chancellor natechancellor@gmail.com
Changes V1 -> V2:
- s/relocation types/program headers/
- s/newer GNU binutils/GNU binutils 2.35+/
- Pick up Ard's Ack.
Note: maintainers may want to pick up the following tag:
Fixes: 3bbd3db86470 ("arm64: relocatable: fix inconsistencies in linker script and options")
or drop the existing fixes tag (this patch is more so in response to change to BFD to warn than fix a kernel regression, IMO, but I don't care). Either way, it would be good to fix this for the newly minted v5.10.y.
Should probably have
Cc: stable@vger.kernel.org
then.
I'll probably be offline for the next two weeks for the holidays, so no promises on quick replies. Happy holidays+new year!
arch/arm64/Makefile | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 6be9b3750250..90309208bb28 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -10,7 +10,7 @@ # # Copyright (C) 1995-2001 by Russell King -LDFLAGS_vmlinux :=--no-undefined -X -z norelro +LDFLAGS_vmlinux :=--no-undefined -X ifeq ($(CONFIG_RELOCATABLE), y) # Pass --no-apply-dynamic-relocs to restore pre-binutils-2.27 behaviour @@ -115,16 +115,20 @@ KBUILD_CPPFLAGS += -mbig-endian CHECKFLAGS += -D__AARCH64EB__ # Prefer the baremetal ELF build target, but not all toolchains include # it so fall back to the standard linux version if needed. -KBUILD_LDFLAGS += -EB $(call ld-option, -maarch64elfb, -maarch64linuxb) +KBUILD_LDFLAGS += -EB $(call ld-option, -maarch64elfb, -maarch64linuxb -z norelro) UTS_MACHINE := aarch64_be else KBUILD_CPPFLAGS += -mlittle-endian CHECKFLAGS += -D__AARCH64EL__ # Same as above, prefer ELF but fall back to linux target if needed. -KBUILD_LDFLAGS += -EL $(call ld-option, -maarch64elf, -maarch64linux) +KBUILD_LDFLAGS += -EL $(call ld-option, -maarch64elf, -maarch64linux -z norelro) UTS_MACHINE := aarch64 endif +ifeq ($(CONFIG_LD_IS_LLD), y) +KBUILD_LDFLAGS += -z norelro +endif
CHECKFLAGS += -D__aarch64__ ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_REGS),y) -- 2.29.2.684.gfbc64c5ab5-goog