| Message ID | 20201218002432.788499-1-ndesaulniers@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] arm64: link with -z norelro for LLD or aarch64-elf | expand |
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 ($(CONFIG_DYNAMIC_FTRACE_WITH_REGS),y) > -- > 2.29.2.684.gfbc64c5ab5-goog >
On Thu, 17 Dec 2020 16:24:32 -0800, Nick Desaulniers wrote: > With GNU binutils 2.35+, linking with BFD produces warnings for vmlinux: > aarch64-linux-gnu-ld: warning: -z norelro ignored > > BFD can produce this warning when the target emulation mode does not > support RELRO program headers, and -z relro or -z norelro is passed. > > Alan Modra clarifies: > The default linker emulation for an aarch64-linux ld.bfd is > -maarch64linux, the default for an aarch64-elf linker is > -maarch64elf. They are not equivalent. If you choose -maarch64elf > you get an emulation that doesn't support -z relro. > > [...] Applied to arm64 (for-next/fixes), thanks! [1/1] arm64: link with -z norelro for LLD or aarch64-elf https://git.kernel.org/arm64/c/311bea3cb9ee Also added the second Fixes tag with a cc stable.
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 6be9b3750250..90309208bb28 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -10,7 +10,7 @@ # # Copyright (C) 1995-2001 by Russell King -LDFLAGS_vmlinux :=--no-undefined -X -z norelro +LDFLAGS_vmlinux :=--no-undefined -X ifeq ($(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)
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> --- 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. 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(-)