From: Alexandru Elisei <alexandru.elisei@arm.com> To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Cc: drjones@redhat.com, pbonzini@redhat.com Subject: [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10 Date: Fri, 17 Jul 2020 17:47:27 +0100 [thread overview] Message-ID: <20200717164727.75580-1-alexandru.elisei@arm.com> (raw) 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@arm.com> --- 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 + define arch_elf_check = $(if $(shell ! $(OBJDUMP) -R $(1) >&/dev/null && echo "nok"), $(error $(shell $(OBJDUMP) -R $(1) 2>&1))) -- 2.27.0
WARNING: multiple messages have this Message-ID (diff)
From: Alexandru Elisei <alexandru.elisei@arm.com> To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Cc: pbonzini@redhat.com Subject: [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10 Date: Fri, 17 Jul 2020 17:47:27 +0100 [thread overview] Message-ID: <20200717164727.75580-1-alexandru.elisei@arm.com> (raw) 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@arm.com> --- 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 + 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@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
next reply other threads:[~2020-07-17 16:46 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-07-17 16:47 Alexandru Elisei [this message] 2020-07-17 16:47 ` [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10 Alexandru Elisei 2020-07-18 9:11 ` Andrew Jones 2020-07-18 9:11 ` Andrew Jones 2020-07-18 13:50 ` Alexandru Elisei 2020-07-18 13:50 ` Alexandru Elisei 2020-07-27 12:21 ` Alexandru Elisei 2020-07-27 12:21 ` Alexandru Elisei 2020-07-27 12:30 ` Andrew Jones 2020-07-27 12:30 ` Andrew Jones 2020-07-27 12:39 ` Alexandru Elisei 2020-07-27 12:39 ` Alexandru Elisei 2020-07-27 17:25 ` Paolo Bonzini 2020-07-27 17:25 ` Paolo Bonzini
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