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Mon, 27 Jul 2020 12:30:36 +0000 (UTC) Received: from kamzik.brq.redhat.com (unknown [10.40.194.132]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CC3111992D; Mon, 27 Jul 2020 12:30:34 +0000 (UTC) Date: Mon, 27 Jul 2020 14:30:31 +0200 From: Andrew Jones To: Alexandru Elisei Subject: Re: [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10 Message-ID: <20200727123031.7v52lu23mmhailar@kamzik.brq.redhat.com> References: <20200717164727.75580-1-alexandru.elisei@arm.com> <20200718091145.zheu46pfjwsntr3a@kamzik.brq.redhat.com> <202d475d-95df-2350-a8e9-9264144993ac@arm.com> <1bf2eab6-c6df-8b4c-b365-7216e7b9a9d7@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1bf2eab6-c6df-8b4c-b365-7216e7b9a9d7@arm.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Cc: pbonzini@redhat.com, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Mon, Jul 27, 2020 at 01:21:03PM +0100, Alexandru Elisei wrote: > Hi Drew, > > On 7/18/20 2:50 PM, Alexandru Elisei wrote: > > Hi, > > > > On 7/18/20 10:11 AM, Andrew Jones wrote: > >> 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 > >>> --- > >>> > >>> 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 > > Looks much better than my version. Do you want me to spin a v2 or do you want to > > send it as a separate patch? If that's the case, I tested the same way I did my > > patch (gcc 10.1.0 and 5.4.0 for cross-compiling, 9.3.0 native): > > > > Tested-by: Alexandru Elisei > > Gentle ping regarding this. > Hi Alexandru, I was on vacation all last week and have been digging myself out of email today. I'll send this as a proper patch with your T-b later today or tomorrow. Thanks, drew _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm