From mboxrd@z Thu Jan 1 00:00:00 1970 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 D7380C25B06 for ; Sun, 14 Aug 2022 15:44:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241188AbiHNPoi (ORCPT ); Sun, 14 Aug 2022 11:44:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39562 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241189AbiHNPmh (ORCPT ); Sun, 14 Aug 2022 11:42:37 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 012DD1C137; Sun, 14 Aug 2022 08:33:40 -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 ams.source.kernel.org (Postfix) with ESMTPS id F2E31B80B87; Sun, 14 Aug 2022 15:33:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3EB0BC43143; Sun, 14 Aug 2022 15:33:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1660491217; bh=jUkAJE7/Y8YQ4Nx6v1v38JNhEtb9m+JA5U0akmvdf3Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OqmRE4YoEslcm+2RyRmlwl2tQWUymbPA9+kBaTo1jThmBimq6aPe8MBf8OS5Mlph6 UW8XpcQpxWtEkzql2sRp3XNDGbNGxrqgCBwnUxzriRkl2Uq542jXowe5twj5QmImvD sIg+GmJORnUosAiHwBLViDPPVnK1FPoPtsh2r/um9KNYlJ9BJhHqI7g84v9XDPLhSs u0BBjyWF8aHpbG7Cta4OoCAYEcbE1+d13+Acd0N6TllC4HImiTiitZvMkCQlhLJswK bliyBmPeUbTpYVWKoD6El1M51CdKH8WLP7GLV6vnYDQv3qW5pSFhpB6arvgO5MNyZu RMtPD7frAtfNQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Nick Desaulniers , Arnd Bergmann , Tao Zhang , Arnd Bergmann , Suzuki K Poulose , Sasha Levin , mathieu.poirier@linaro.org, alexander.shishkin@linux.intel.com, nathan@kernel.org, coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev Subject: [PATCH AUTOSEL 5.15 24/46] coresight: etm4x: avoid build failure with unrolled loops Date: Sun, 14 Aug 2022 11:32:25 -0400 Message-Id: <20220814153247.2378312-24-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220814153247.2378312-1-sashal@kernel.org> References: <20220814153247.2378312-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 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' directive .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 = 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) : "=r" (__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))" : "=r"(__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@google.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/hwtracing/coresight/coresight-etm4x.h index e5b79bdb9851..794b29639035 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x.h +++ b/drivers/hwtracing/coresight/coresight-etm4x.h @@ -7,6 +7,7 @@ #define _CORESIGHT_CORESIGHT_ETM_H #include +#include #include #include #include "coresight-priv.h" @@ -417,7 +418,7 @@ ({ \ u64 __val; \ \ - if (__builtin_constant_p((offset))) \ + if (__is_constexpr((offset))) \ __val = read_etm4x_sysreg_const_offset((offset)); \ else \ __val = etm4x_sysreg_read((offset), true, (_64bit)); \ -- 2.35.1