From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5EA95436A for ; Thu, 17 Feb 2022 17:41:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 467FFC340E8; Thu, 17 Feb 2022 17:41:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1645119703; bh=8pbZj/3cVuW2vQLaHmXTlBvSAEOnHZPHPU8EvjwJvmY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lICo15JaGIZ/+wRcv2OoGVinuJEdNg3fOgujgAyrExKrBVNZWnseGROU0F8zsi3XY SwZR4kNdyhOIKqUv8y+gsMfXk8TBoQPckN91MTym3WTpQB1X7VLe8CL/u5O+Pf9x9a UxRJvr1+jg2PvqdiG+nBI0C+x2ZyLUiI3nyUguqk62WvzsT2+H3tL3JabPWuJXf4cU AKOkKRnJBf9FTiqOTbx2N6qVW5b2iVuCWLutJcz2kv473EmYc2TlKYMhu4n1/gj0d9 1TjxBU5O4nVFT1ikddcrYzGZ55h/hVIr4rQws6yNoehya20EIeOGWhPPzUpR1bL+Nv XQ6Bz+csenJuw== Date: Thu, 17 Feb 2022 10:41:37 -0700 From: Nathan Chancellor To: Masahiro Yamada Cc: Kees Cook , Jeff Dike , Richard Weinberger , Anton Ivanov , Nick Desaulniers , David Gow , linux-um@lists.infradead.org, Linux Kbuild mailing list , "open list:KERNEL SELFTEST FRAMEWORK" , kunit-dev@googlegroups.com, llvm@lists.linux.dev, Linux Kernel Mailing List , X86 ML , linux-hardening@vger.kernel.org Subject: Re: [PATCH] um: Allow builds with Clang Message-ID: References: <20220217002843.2312603-1-keescook@chromium.org> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Feb 17, 2022 at 01:54:58PM +0900, Masahiro Yamada wrote: > On Thu, Feb 17, 2022 at 9:28 AM Kees Cook wrote: > > > > Add x86-64 target for Clang+um and update user-offsets.c to use > > Clang-friendly assembler, similar to the fix from commit cf0c3e68aa81 > > ("kbuild: fix asm-offset generation to work with clang"). > > > > This lets me run KUnit tests with Clang: > > > > $ ./tools/testing/kunit/kunit.py config --make_options LLVM=1 > > ... > > $ ./tools/testing/kunit/kunit.py run --make_options LLVM=1 > > ... > > > > Cc: Jeff Dike > > Cc: Richard Weinberger > > Cc: Anton Ivanov > > Cc: Masahiro Yamada > > Cc: Nick Desaulniers > > Cc: Nathan Chancellor > > Cc: David Gow > > Cc: linux-um@lists.infradead.org > > Cc: linux-kbuild@vger.kernel.org > > Cc: linux-kselftest@vger.kernel.org > > Cc: kunit-dev@googlegroups.com > > Cc: llvm@lists.linux.dev > > Signed-off-by: Kees Cook > > --- > > arch/x86/um/user-offsets.c | 4 ++-- > > scripts/Makefile.clang | 1 + > > 2 files changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c > > index bae61554abcc..d9071827b515 100644 > > --- a/arch/x86/um/user-offsets.c > > +++ b/arch/x86/um/user-offsets.c > > @@ -10,10 +10,10 @@ > > #include > > > > #define DEFINE(sym, val) \ > > - asm volatile("\n->" #sym " %0 " #val : : "i" (val)) > > + asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val)) > > > > #define DEFINE_LONGS(sym, val) \ > > - asm volatile("\n->" #sym " %0 " #val : : "i" (val/sizeof(unsigned long))) > > + asm volatile("\n.ascii \"->" #sym " %0 " #val "\"": : "i" (val/sizeof(unsigned long))) > > > > void foo(void) > > { > > diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang > > index 51fc23e2e9e5..857b23de51c6 100644 > > --- a/scripts/Makefile.clang > > +++ b/scripts/Makefile.clang > > @@ -10,6 +10,7 @@ CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu > > CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu > > CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu > > CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu > > +CLANG_TARGET_FLAGS_um := x86_64-linux-gnu > > > Does this work for the i386 host? > > UML supports i386 and x86_64 as the host architecture as of now, > but this always compiles UML for x86_64? I think the current code will work because arch/x86/Makefile.um includes -m32 for CONFIG_X86_32, which will implicitly change x86_64-linux-gnu into a 32-bit target triple: $ echo | clang --target=x86_64-linux-gnu -x c -c -o test.o - $ file test.o test.o: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped $ echo | clang --target=x86_64-linux-gnu -m32 -x c -c -o test.o - $ file test.o test.o: ELF 32-bit LSB relocatable, Intel 80386, version 1 (SYSV), not stripped In fact, we rely on this for ARCH=i386 LLVM=1 right now, as it uses x86_64-linux-gnu for the target flag. While UML only supports x86, maybe it is worth using SUBARCH instead of hardcoding the triple? No strong opinion around that though. diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang index 51fc23e2e9e5..87285b76adb2 100644 --- a/scripts/Makefile.clang +++ b/scripts/Makefile.clang @@ -10,6 +10,7 @@ CLANG_TARGET_FLAGS_powerpc := powerpc64le-linux-gnu CLANG_TARGET_FLAGS_riscv := riscv64-linux-gnu CLANG_TARGET_FLAGS_s390 := s390x-linux-gnu CLANG_TARGET_FLAGS_x86 := x86_64-linux-gnu +CLANG_TARGET_FLAGS_um := $(CLANG_TARGET_FLAGS_$(SUBARCH)) CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH)) ifeq ($(CROSS_COMPILE),) > > CLANG_TARGET_FLAGS := $(CLANG_TARGET_FLAGS_$(SRCARCH)) > > > > ifeq ($(CROSS_COMPILE),) > > -- > > 2.30.2 > > > > > -- > Best Regards > Masahiro Yamada