On Thu, Sep 26, 2019 at 6:38 AM Vincenzo Frascino <vincenzo.frasc...@arm.com> wrote: > > As reported by Will Deacon, older versions of binutils that do not > support certain types of memory barriers can cause build failure of the > vdso32 library.
Do we know which specific version of binutils has this problem? Documentation/process/changes.rst lists 2.21+ as the supported versions. If it's older than that, it's unsupported. I triple checked android's 2.27 seems ok. $ cat bar.s .text .globl foo dmb ish dmb ishld dmb ishst $ aarch64-linux-gnu-as bar.s $ echo $? 0 $ llvm-objdump -d a.out a.out: file format ELF64-aarch64-little Disassembly of section .text: 0000000000000000 $x: 0: bf 3b 03 d5 dmb ish 4: bf 39 03 d5 dmb ishld 8: bf 3a 03 d5 dmb ishst > > Add a compilation time mechanism that detects if binutils supports those > instructions and configure the kernel accordingly. > > Cc: Will Deacon <w...@kernel.org> > Cc: Catalin Marinas <catalin.mari...@arm.com> > Signed-off-by: Vincenzo Frascino <vincenzo.frasc...@arm.com> > --- > arch/arm64/Kbuild | 6 ++++++ > arch/arm64/include/asm/vdso/compat_barrier.h | 2 +- > arch/arm64/kernel/vdso32/Makefile | 9 +++++++++ > 3 files changed, 16 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/Kbuild b/arch/arm64/Kbuild > index d6465823b281..75cf8c796d0e 100644 > --- a/arch/arm64/Kbuild > +++ b/arch/arm64/Kbuild > @@ -4,3 +4,9 @@ obj-$(CONFIG_NET) += net/ > obj-$(CONFIG_KVM) += kvm/ > obj-$(CONFIG_XEN) += xen/ > obj-$(CONFIG_CRYPTO) += crypto/ > + > +# as-instr-compat > +# Usage: cflags-y += $(call as-instr-compat,instr,option1,option2) > + > +as-instr-compat = $(call try-run,\ > + printf "%b\n" "$(1)" | $(COMPATCC) $(KBUILD_AFLAGS) -c -x assembler > -o "$$TMP" -,$(2),$(3)) > diff --git a/arch/arm64/include/asm/vdso/compat_barrier.h > b/arch/arm64/include/asm/vdso/compat_barrier.h > index fb60a88b5ed4..3fd8fd6d8fc2 100644 > --- a/arch/arm64/include/asm/vdso/compat_barrier.h > +++ b/arch/arm64/include/asm/vdso/compat_barrier.h > @@ -20,7 +20,7 @@ > > #define dmb(option) __asm__ __volatile__ ("dmb " #option : : : "memory") > > -#if __LINUX_ARM_ARCH__ >= 8 > +#if __LINUX_ARM_ARCH__ >= 8 && defined(CONFIG_AS_DMB_ISHLD) > #define aarch32_smp_mb() dmb(ish) > #define aarch32_smp_rmb() dmb(ishld) > #define aarch32_smp_wmb() dmb(ishst) > diff --git a/arch/arm64/kernel/vdso32/Makefile > b/arch/arm64/kernel/vdso32/Makefile > index 1fba0776ed40..22f0d31ea528 100644 > --- a/arch/arm64/kernel/vdso32/Makefile > +++ b/arch/arm64/kernel/vdso32/Makefile > @@ -17,6 +17,8 @@ cc32-disable-warning = $(call try-run,\ > $(COMPATCC) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip > $(1))) > cc32-ldoption = $(call try-run,\ > $(COMPATCC) $(1) -nostdlib -x c /dev/null -o "$$TMP",$(1),$(2)) > +cc32-as-instr = $(call try-run,\ > + printf "%b\n" "$(1)" | $(COMPATCC) $(VDSO_AFLAGS) -c -x assembler -o > "$$TMP" -,$(2),$(3)) > > # We cannot use the global flags to compile the vDSO files, the main reason > # being that the 32-bit compiler may be older than the main (64-bit) compiler > @@ -55,6 +57,7 @@ endif > VDSO_CAFLAGS += -fPIC -fno-builtin -fno-stack-protector > VDSO_CAFLAGS += -DDISABLE_BRANCH_PROFILING > > + > # Try to compile for ARMv8. If the compiler is too old and doesn't support > it, > # fall back to v7. There is no easy way to check for what architecture the > code > # is being compiled, so define a macro specifying that (see > arch/arm/Makefile). > @@ -91,6 +94,12 @@ VDSO_CFLAGS += -Wno-int-to-pointer-cast > VDSO_AFLAGS := $(VDSO_CAFLAGS) > VDSO_AFLAGS += -D__ASSEMBLY__ > > +# Check for binutils support for dmb ishld > +dmbinstr := $(call cc32-as-instr,dmb ishld,-DCONFIG_AS_DMB_ISHLD=1) > + > +VDSO_CFLAGS += $(dmbinstr) > +VDSO_AFLAGS += $(dmbinstr) > + > VDSO_LDFLAGS := $(VDSO_CPPFLAGS) > # From arm vDSO Makefile > VDSO_LDFLAGS += -Wl,-Bsymbolic -Wl,--no-undefined -Wl,-soname=linux-vdso.so.1 > -- > 2.23.0 > -- Thanks, ~Nick Desaulniers