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Thu, 13 Feb 2020 10:44:56 -0800 (PST) Date: Thu, 13 Feb 2020 11:44:54 -0700 From: Nathan Chancellor To: Vincenzo Frascino Cc: linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, clang-built-linux@googlegroups.com, x86@kernel.org, catalin.marinas@arm.com, will.deacon@arm.com, arnd@arndb.de, linux@armlinux.org.uk, paul.burton@mips.com, tglx@linutronix.de, luto@kernel.org, mingo@redhat.com, bp@alien8.de, sboyd@kernel.org, salyzyn@android.com, pcc@google.com, 0x7f454c46@gmail.com, ndesaulniers@google.com, avagin@openvz.org Subject: Re: [PATCH 19/19] arm64: vdso32: Enable Clang Compilation Message-ID: <20200213184454.GA4663@ubuntu-m2-xlarge-x86> References: <20200213161614.23246-1-vincenzo.frascino@arm.com> <20200213161614.23246-20-vincenzo.frascino@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200213161614.23246-20-vincenzo.frascino@arm.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 13, 2020 at 04:16:14PM +0000, Vincenzo Frascino wrote: > Enable Clang Compilation for the vdso32 library. > > Cc: Catalin Marinas > Cc: Will Deacon > Signed-off-by: Vincenzo Frascino > --- > arch/arm64/kernel/vdso32/Makefile | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile > index 04df57b43cb1..209639101044 100644 > --- a/arch/arm64/kernel/vdso32/Makefile > +++ b/arch/arm64/kernel/vdso32/Makefile > @@ -11,8 +11,10 @@ include $(srctree)/lib/vdso/Makefile > # Same as cc-*option, but using CC_COMPAT instead of CC > ifeq ($(CONFIG_CC_IS_CLANG), y) > CC_COMPAT ?= $(CC) > +LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc Well this is unfortunate :/ It looks like adding the --target flag to VDSO_LDFLAGS allows clang to link the vDSO just fine although it does warn that -nostdinc is unused: clang-11: warning: argument unused during compilation: '-nostdinc' [-Wunused-command-line-argument] It would be nice if the logic of commit fe00e50b2db8 ("ARM: 8858/1: vdso: use $(LD) instead of $(CC) to link VDSO") could be adopted here but I get that this Makefile is its own beast :) at the very least, I think that the --target flag should be added to VDSO_LDFLAGS so that gcc is not a requirement for this but I am curious if you tried that already and noticed any issues with it. Cheers, Nathan > else > CC_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc > +LD_COMPAT ?= $(CC_COMPAT) > endif > > cc32-option = $(call try-run,\ > @@ -171,7 +173,7 @@ quiet_cmd_vdsold_and_vdso_check = LD32 $@ > cmd_vdsold_and_vdso_check = $(cmd_vdsold); $(cmd_vdso_check) > > quiet_cmd_vdsold = LD32 $@ > - cmd_vdsold = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_LDFLAGS) \ > + cmd_vdsold = $(LD_COMPAT) -Wp,-MD,$(depfile) $(VDSO_LDFLAGS) \ > -Wl,-T $(filter %.lds,$^) $(filter %.o,$^) -o $@ > quiet_cmd_vdsocc = CC32 $@ > cmd_vdsocc = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_CFLAGS) -c -o $@ $< > -- > 2.25.0 >