On Fri, Jul 17, 2020 at 05:47:27PM +0100, Alexandru Elisei wrote:
> GCC 10.1.0 introduced the -m{,no-}outline-atomics flags which, according to
> man 1 gcc:
>
> "Enable or disable calls to out-of-line helpers to implement atomic
> operations. These helpers will, at runtime, determine if the LSE
> instructions from ARMv8.1-A can be used; if not, they will use the
> load/store-exclusive instructions that are present in the base ARMv8.0 ISA.
> [..] This option is on by default."
>
> Unfortunately the option causes the following error at compile time:
>
> aarch64-linux-gnu-ld -nostdlib -pie -n -o arm/spinlock-test.elf -T /path/to/kvm-unit-tests/arm/flat.lds \
> arm/spinlock-test.o arm/cstart64.o lib/libcflat.a lib/libfdt/libfdt.a /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a lib/arm/libeabi.a arm/spinlock-test.aux.o
> aarch64-linux-gnu-ld: /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a(lse-init.o): in function `init_have_lse_atomics':
> lse-init.c:(.text.startup+0xc): undefined reference to `__getauxval'
>
> This is happening because we are linking against our own libcflat which
> doesn't implement the function __getauxval().
>
> Disable the use of the out-of-line functions by compiling with
> -mno-outline-atomics if we detect a GCC version greater than 10.
>
> Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
> ---
>
> Tested with gcc versions 10.1.0 and 5.4.0 (cross-compilation), 9.3.0
> (native).
>
> I've been able to suss out the reason for the build failure from this
> rejected gcc patch [1].
>
> [1] https://patches.openembedded.org/patch/172460/
>
> arm/Makefile.arm64 | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
> index dfd0c56fe8fb..3223cb966789 100644
> --- a/arm/Makefile.arm64
> +++ b/arm/Makefile.arm64
> @@ -9,6 +9,12 @@ ldarch = elf64-littleaarch64
> arch_LDFLAGS = -pie -n
> CFLAGS += -mstrict-align
>
> +# The -mno-outline-atomics flag is only valid for GCC versions 10 and greater.
> +GCC_MAJOR_VERSION=$(shell $(CC) -dumpversion 2> /dev/null | cut -f1 -d.)
> +ifeq ($(shell expr "$(GCC_MAJOR_VERSION)" ">=" "10"), 1)
> +CFLAGS += -mno-outline-atomics
> +endif
How about this patch instead?
diff --git a/Makefile b/Makefile
index 3ff2f91600f6..0e21a49096ba 100644
--- a/Makefile
+++ b/Makefile
@@ -17,6 +17,11 @@ DESTDIR := $(PREFIX)/share/kvm-unit-tests/
.PHONY: arch_clean clean distclean cscope
+# cc-option
+# Usage: OP_CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)
+cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
+ > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
+
#make sure env CFLAGS variable is not used
CFLAGS =
@@ -43,12 +48,6 @@ OBJDIRS += $(LIBFDT_objdir)
#include architecture specific make rules
include $(SRCDIR)/$(TEST_DIR)/Makefile
-# cc-option
-# Usage: OP_CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)
-
-cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
- > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
-
COMMON_CFLAGS += -g $(autodepend-flags) -fno-strict-aliasing -fno-common
COMMON_CFLAGS += -Wall -Wwrite-strings -Wempty-body -Wuninitialized
COMMON_CFLAGS += -Wignored-qualifiers -Werror
diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
index dfd0c56fe8fb..dbc7524d3070 100644
--- a/arm/Makefile.arm64
+++ b/arm/Makefile.arm64
@@ -9,6 +9,9 @@ ldarch = elf64-littleaarch64
arch_LDFLAGS = -pie -n
CFLAGS += -mstrict-align
+mno_outline_atomics := $(call cc-option, -mno-outline-atomics, "")
+CFLAGS += $(mno_outline_atomics)
+
define arch_elf_check =
$(if $(shell ! $(OBJDUMP) -R $(1) >&/dev/null && echo "nok"),
$(error $(shell $(OBJDUMP) -R $(1) 2>&1)))
Thanks,
drew
> +
> define arch_elf_check =
> $(if $(shell ! $(OBJDUMP) -R $(1) >&/dev/null && echo "nok"),
> $(error $(shell $(OBJDUMP) -R $(1) 2>&1)))
> --
> 2.27.0
>
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
