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 720EFC2F6; Mon, 17 Jul 2023 20:31:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 478B5C433C8; Mon, 17 Jul 2023 20:31:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689625867; bh=speJUgxSauJb1B97mFzBthgQeNkIXMJQ46d1kG1IBpc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=m5yuNuQ1k00JkD9oSP99xNX3im7OVU9ke1O/ZJxzB5liJ3nS6KJ2q72BNShSb8I7N xppmSyS3mUTrvFrkFzJ6J5Yw3LZXsB9RD6iUirXgxE3ablVVioaCTngcISqjmlozVU gM5C0SHbQBOzZ3Ij/zMvrL9c8QRxdOFSMi+Qp5Zckvnne5ZjBFWrgeyni0U8xyxxok fU7tH/sJXbgeCL7j5rOm0FP8u9kTsuCKd92YiIpBjzWUk2xb01vmp7Ypw8dMNf1LN0 dNIGJJxYGwf1mnzOR0t44YMDNIxi2jaFUurlzb8nT6xsXEEMOkm/MQ+LdvDLIWoA+L X4btRRdqJSTvQ== Date: Mon, 17 Jul 2023 13:31:05 -0700 From: Nathan Chancellor To: Yury Norov Cc: linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Nick Desaulniers , Andy Shevchenko , Alexander Lobakin , Maxim Kuvyrkov , Rasmus Villemoes , Tom Rix , oe-kbuild-all@lists.linux.dev Subject: Re: [PATCH] lib/bitmap: waive const_eval test as it breaks the build Message-ID: <20230717203105.GA2212488@dev-arch.thelio-3990X> References: <20230717195813.29059-1-yury.norov@gmail.com> 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: <20230717195813.29059-1-yury.norov@gmail.com> Hi Yury, On Mon, Jul 17, 2023 at 12:58:13PM -0700, Yury Norov wrote: > When building with clang, and when KASAN and GCOV_PROFILE_ALL are both > enabled, the test fails to build [1]: > > >> lib/test_bitmap.c:920:2: error: call to '__compiletime_assert_239' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res) > BUILD_BUG_ON(!__builtin_constant_p(res)); > ^ > include/linux/build_bug.h:50:2: note: expanded from macro 'BUILD_BUG_ON' > BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) > ^ > include/linux/build_bug.h:39:37: note: expanded from macro 'BUILD_BUG_ON_MSG' > #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) > ^ > include/linux/compiler_types.h:352:2: note: expanded from macro 'compiletime_assert' > _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) > ^ > include/linux/compiler_types.h:340:2: note: expanded from macro '_compiletime_assert' > __compiletime_assert(condition, msg, prefix, suffix) > ^ > include/linux/compiler_types.h:333:4: note: expanded from macro '__compiletime_assert' > prefix ## suffix(); \ > ^ > :185:1: note: expanded from here > __compiletime_assert_239 > > Originally it was attributed to s390, which now looks seemingly wrong. The > issue is also not related to bitmap code itself, but it breaks build for > a given configuration. So, disabling the test unless the compiler will > get fixed. > > [1] https://github.com/ClangBuiltLinux/linux/issues/1874 > > Fixes: dc34d5036692 ("lib: test_bitmap: add compile-time optimization/evaluations assertions") > Signed-off-by: Yury Norov > --- > lib/test_bitmap.c | 17 +++++------------ > 1 file changed, 5 insertions(+), 12 deletions(-) > > diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c > index 187f5b2db4cf..a791fdb7a8c9 100644 > --- a/lib/test_bitmap.c > +++ b/lib/test_bitmap.c > @@ -1163,6 +1163,9 @@ static void __init test_bitmap_print_buf(void) > > static void __init test_bitmap_const_eval(void) > { > +#if defined(CONFIG_CC_IS_CLANG) && defined(CONFIG_KASAN) && defined(CONFIG_GCOV_PROFILE_ALL) > +#warning "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled" Making this a '#warning' will basically just replace the current error with a different one in the face of CONFIG_WERROR, which seems pointless to me: lib/test_bitmap.c:1167:2: error: "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled" [-Werror,-W#warnings] 1167 | #warning "FIXME: Clang breaks compile time evaluations when KASAN and GCOV are enabled" | ^ 1 error generated. Could we just opt out of GCOV for test_bitmap.c if KASAN is enabled with clang? That does not seem too bad of a workaround. I highly doubt there are many people who are interested in debugging test_bitmap.c with KASAN while profiling it with GCOV when building with clang, since they would have hit this already and reported it already; as far as I can tell, only the Intel robot has reported this with a randconfig. diff --git a/lib/Makefile b/lib/Makefile index 42d307ade225..c6f60ae42769 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -83,6 +83,10 @@ obj-$(CONFIG_TEST_DYNAMIC_DEBUG) += test_dynamic_debug.o obj-$(CONFIG_TEST_PRINTF) += test_printf.o obj-$(CONFIG_TEST_SCANF) += test_scanf.o obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o +# https://github.com/ClangBuiltLinux/linux/issues/1874 +ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_KASAN),yy) +GCOV_PROFILE_test_bitmap.o := n +endif obj-$(CONFIG_TEST_UUID) += test_uuid.o obj-$(CONFIG_TEST_XARRAY) += test_xarray.o obj-$(CONFIG_TEST_MAPLE_TREE) += test_maple_tree.o Cheers, Nathan > +#else > DECLARE_BITMAP(bitmap, BITS_PER_LONG); > unsigned long initvar = BIT(2); > unsigned long bitopvar = 0; > @@ -1177,20 +1180,9 @@ static void __init test_bitmap_const_eval(void) > * in runtime. > */ > > - /* > - * Equals to `unsigned long bitmap[1] = { GENMASK(6, 5), }`. > - * Clang on s390 optimizes bitops at compile-time as intended, but at > - * the same time stops treating @bitmap and @bitopvar as compile-time > - * constants after regular test_bit() is executed, thus triggering the > - * build bugs below. So, call const_test_bit() there directly until > - * the compiler is fixed. > - */ > + /* Equals to `unsigned long bitmap[1] = { GENMASK(6, 5), }` */ > bitmap_clear(bitmap, 0, BITS_PER_LONG); > -#if defined(__s390__) && defined(__clang__) > - if (!const_test_bit(7, bitmap)) > -#else > if (!test_bit(7, bitmap)) > -#endif > bitmap_set(bitmap, 5, 2); > > /* Equals to `unsigned long bitopvar = BIT(20)` */ > @@ -1220,6 +1212,7 @@ static void __init test_bitmap_const_eval(void) > /* ~BIT(25) */ > BUILD_BUG_ON(!__builtin_constant_p(~var)); > BUILD_BUG_ON(~var != ~BIT(25)); > +#endif > } > > static void __init selftest(void) > -- > 2.39.2 >