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 953A51C01 for ; Sun, 14 Aug 2022 15:28:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E0712C433C1; Sun, 14 Aug 2022 15:28:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1660490937; bh=mDDod5hoK9zUIp4GLrFxdxCIQSI8HzlisO5aPIIpYBk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BmVsbBFU/j93P+ja3YK1lSuc+16nTMIgn6iLNGT1lbqb7Gpbriw5Xx4XeO8EN3lqk FNYj8TSTV/yyMHfhpA/FgiF9WfCobQApoMdH3clhMMqjIGJCQoDxyhb4nOf/SyUN96 S6fU2Wuuxnq7gAxRUFPYNDx4OEsjJ3DiwLSwoLknlBZBIl1VUnJrTQGnodZysIsore gVvtzA01RENGo0WhzAeDLzf4CNYwVbm8Ntzo516Ng7+tZpvYua1hgd3DVNKEX5bv/C oLIJ3xlAFLB7t/tDk492ZLiefhiIy51NPub6SxiwQh8Vxxp032Qo+C5VXAgHkB+aAS Qp/uKbUaamKqw== 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 5.19 32/64] coresight: etm4x: avoid build failure with unrolled loops Date: Sun, 14 Aug 2022 11:24:05 -0400 Message-Id: <20220814152437.2374207-32-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220814152437.2374207-1-sashal@kernel.org> References: <20220814152437.2374207-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit 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 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 #include +#include #include #include #include "coresight-priv.h" @@ -515,7 +516,7 @@ ({ \ 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