From nobody Thu Dec 18 13:02:27 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9FBBDC32772 for ; Tue, 23 Aug 2022 09:15:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243556AbiHWJPQ (ORCPT ); Tue, 23 Aug 2022 05:15:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33274 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348671AbiHWJMW (ORCPT ); Tue, 23 Aug 2022 05:12:22 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8F0796D576; Tue, 23 Aug 2022 01:31:47 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 19CF76147B; Tue, 23 Aug 2022 08:31:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 250DDC433C1; Tue, 23 Aug 2022 08:31:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661243469; bh=mDDod5hoK9zUIp4GLrFxdxCIQSI8HzlisO5aPIIpYBk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=weXUF9jGuxizLED8U2nYYGYAH8rBGyk4ZRrlil22bAqMKnWaqfs9mU6T9zHz7+a8c eR7Hl9u3JQNeqHLGVyfwqFpFhsjgQQeEO2+sJtSI4hyGU71H3Tj15M2X9v9sFhnxyz hGEzNZK/GJ5kR547Ua+vObm8HPNRmrU/nwLeyQHE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Arnd Bergmann , Tao Zhang , Nick Desaulniers , Arnd Bergmann , Suzuki K Poulose , Sasha Levin Subject: [PATCH 5.19 287/365] coresight: etm4x: avoid build failure with unrolled loops Date: Tue, 23 Aug 2022 10:03:08 +0200 Message-Id: <20220823080130.208107606@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080118.128342613@linuxfoundation.org> References: <20220823080118.128342613@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Nick Desaulniers [ Upstream commit 4d45bc82df667ad9e9cb8361830e54fc1264e993 ] When the following configs are enabled: * CORESIGHT * CORESIGHT_SOURCE_ETM4X * UBSAN * UBSAN_TRAP Clang fails assemble the kernel with the error: :1:7: error: expected constant expression in '.inst' directi= ve .inst (0xd5200000|((((2) << 19) | ((1) << 16) | (((((((((((0x160 + (i * 4))= ))) >> 2))) >> 7) & 0x7)) << 12) | ((((((((((0x160 + (i * 4))))) >> 2))) & = 0xf)) << 8) | (((((((((((0x160 + (i * 4))))) >> 2))) >> 4) & 0x7)) << 5)))|= (.L__reg_num_x8)) ^ drivers/hwtracing/coresight/coresight-etm4x-core.c:702:4: note: while in macro instantiation etm4x_relaxed_read32(csa, TRCCNTVRn(i)); ^ drivers/hwtracing/coresight/coresight-etm4x.h:403:4: note: expanded from macro 'etm4x_relaxed_read32' read_etm4x_sysreg_offset((offset), false))) ^ drivers/hwtracing/coresight/coresight-etm4x.h:383:12: note: expanded from macro 'read_etm4x_sysreg_offset' __val =3D read_etm4x_sysreg_const_offset((offset)); \ ^ drivers/hwtracing/coresight/coresight-etm4x.h:149:2: note: expanded from macro 'read_etm4x_sysreg_const_offset' READ_ETM4x_REG(ETM4x_OFFSET_TO_REG(offset)) ^ drivers/hwtracing/coresight/coresight-etm4x.h:144:2: note: expanded from macro 'READ_ETM4x_REG' read_sysreg_s(ETM4x_REG_NUM_TO_SYSREG((reg))) ^ arch/arm64/include/asm/sysreg.h:1108:15: note: expanded from macro 'read_sysreg_s' asm volatile(__mrs_s("%0", r) : "=3Dr" (__val)); \ ^ arch/arm64/include/asm/sysreg.h:1074:2: note: expanded from macro '__mrs_s' " mrs_s " v ", " __stringify(r) "\n" \ ^ Consider the definitions of TRCSSCSRn and TRCCNTVRn: drivers/hwtracing/coresight/coresight-etm4x.h:56 #define TRCCNTVRn(n) (0x160 + (n * 4)) drivers/hwtracing/coresight/coresight-etm4x.h:81 #define TRCSSCSRn(n) (0x2A0 + (n * 4)) Where the macro parameter is expanded to i; a loop induction variable from etm4_disable_hw. When any compiler can determine that loops may be unrolled, then the __builtin_constant_p check in read_etm4x_sysreg_offset() defined in drivers/hwtracing/coresight/coresight-etm4x.h may evaluate to true. This can lead to the expression `(0x160 + (i * 4))` being passed to read_etm4x_sysreg_const_offset. Via the trace above, this is passed through READ_ETM4x_REG, read_sysreg_s, and finally to __mrs_s where it is string-ified and used directly in inline asm. Regardless of which compiler or compiler options determine whether a loop can or can't be unrolled, which determines whether __builtin_constant_p evaluates to true when passed an expression using a loop induction variable, it is NEVER safe to allow the preprocessor to construct inline asm like: asm volatile (".inst (0x160 + (i * 4))" : "=3Dr"(__val)); ^ expected constant expression Instead of read_etm4x_sysreg_offset() using __builtin_constant_p(), use __is_constexpr from include/linux/const.h instead to ensure only expressions that are valid integer constant expressions get passed through to read_sysreg_s(). This is not a bug in clang; it's a potentially unsafe use of the macro arguments in read_etm4x_sysreg_offset dependent on __builtin_constant_p. Link: https://github.com/ClangBuiltLinux/linux/issues/1310 Reported-by: Arnd Bergmann Reported-by: Tao Zhang Signed-off-by: Nick Desaulniers Acked-by: Arnd Bergmann Signed-off-by: Suzuki K Poulose Link: https://lore.kernel.org/r/20220708231520.3958391-1-ndesaulniers@googl= e.com Signed-off-by: Sasha Levin --- drivers/hwtracing/coresight/coresight-etm4x.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtrac= ing/coresight/coresight-etm4x.h index 33869c1d20c3..a7bfea31f7d8 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x.h +++ b/drivers/hwtracing/coresight/coresight-etm4x.h @@ -7,6 +7,7 @@ #define _CORESIGHT_CORESIGHT_ETM_H =20 #include +#include #include #include #include "coresight-priv.h" @@ -515,7 +516,7 @@ ({ \ u64 __val; \ \ - if (__builtin_constant_p((offset))) \ + if (__is_constexpr((offset))) \ __val =3D read_etm4x_sysreg_const_offset((offset)); \ else \ __val =3D etm4x_sysreg_read((offset), true, (_64bit)); \ --=20 2.35.1