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 B3F962590 for ; Sun, 22 Jan 2023 15:27:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3992CC433D2; Sun, 22 Jan 2023 15:27:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1674401248; bh=Z+go7V2dzW28B1W51aduDlNg9EWQ3PwYuDkZM4E7Jtk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LFnljg8ll7NgcHtIMHqieq0NA5yruaVXyjyWzgeKV/6rdlVQz1FcvAMSlnJJSzz+J /e3IerWYThhUBFn43oi9WovzrGBxEIFyq56/ijLt/P+k9a+U+d/MqMr+B8DE2U3O3H e3+hBGnZDtbclQRSmEcFO/xjhdvsiiHw7PAmJBPk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, YingChi Long , Borislav Petkov , Nick Desaulniers , Nathan Chancellor Subject: [PATCH 6.1 159/193] x86/fpu: Use _Alignof to avoid undefined behavior in TYPE_ALIGN Date: Sun, 22 Jan 2023 16:04:48 +0100 Message-Id: <20230122150253.675516595@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230122150246.321043584@linuxfoundation.org> References: <20230122150246.321043584@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: YingChi Long commit 55228db2697c09abddcb9487c3d9fa5854a932cd upstream. WG14 N2350 specifies that it is an undefined behavior to have type definitions within offsetof", see https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm This specification is also part of C23. Therefore, replace the TYPE_ALIGN macro with the _Alignof builtin to avoid undefined behavior. (_Alignof itself is C11 and the kernel is built with -gnu11). ISO C11 _Alignof is subtly different from the GNU C extension __alignof__. Latter is the preferred alignment and _Alignof the minimal alignment. For long long on x86 these are 8 and 4 respectively. The macro TYPE_ALIGN's behavior matches _Alignof rather than __alignof__. [ bp: Massage commit message. ] Signed-off-by: YingChi Long Signed-off-by: Borislav Petkov Reviewed-by: Nick Desaulniers Link: https://lore.kernel.org/r/20220925153151.2467884-1-me@inclyc.cn Signed-off-by: Nathan Chancellor Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/fpu/init.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) --- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -133,9 +133,6 @@ static void __init fpu__init_system_gene fpu__init_system_mxcsr(); } -/* Get alignment of the TYPE. */ -#define TYPE_ALIGN(TYPE) offsetof(struct { char x; TYPE test; }, test) - /* * Enforce that 'MEMBER' is the last field of 'TYPE'. * @@ -143,8 +140,8 @@ static void __init fpu__init_system_gene * because that's how C aligns structs. */ #define CHECK_MEMBER_AT_END_OF(TYPE, MEMBER) \ - BUILD_BUG_ON(sizeof(TYPE) != ALIGN(offsetofend(TYPE, MEMBER), \ - TYPE_ALIGN(TYPE))) + BUILD_BUG_ON(sizeof(TYPE) != \ + ALIGN(offsetofend(TYPE, MEMBER), _Alignof(TYPE))) /* * We append the 'struct fpu' to the task_struct: