From patchwork Thu Sep 30 18:05:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 12537987 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B8D5FC433FE for ; Thu, 30 Sep 2021 18:05:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9FC2361A02 for ; Thu, 30 Sep 2021 18:05:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353066AbhI3SH0 (ORCPT ); Thu, 30 Sep 2021 14:07:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353062AbhI3SHZ (ORCPT ); Thu, 30 Sep 2021 14:07:25 -0400 Received: from mail-qv1-xf4a.google.com (mail-qv1-xf4a.google.com [IPv6:2607:f8b0:4864:20::f4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9CE76C06176F for ; Thu, 30 Sep 2021 11:05:42 -0700 (PDT) Received: by mail-qv1-xf4a.google.com with SMTP id q9-20020ad45749000000b00382b7c83aa1so31659qvx.11 for ; Thu, 30 Sep 2021 11:05:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=7QsELX2b4zYjlGgyKK6SovhZ4mE+qI9YjYk7qrPU0wo=; b=U3ToAP/4F0z7c/GCezlIqVZAyjDQl9Undff00n8rJGZDjq+07eqdViNINuCfWY1gAV unl0hcnz0BXbOBcy4UqMjtpy6qawy4EcwcORy+8OW1ACvyXXa6zNSchJ1AgtSuMiyhci A2Rb3gS4n1GsjAdz8QP0qRZXZlN7W5YcVoEHpCHtWmD7vAunZfgv5OLov4Y4ncEh1Feb 8FI5yhThK1PcJDaedcnZ0vKjLy0BIpS4W/lszSEK1gEaPNiwNcDLMreQ6kvO28TkAnOW hUXG+aiWaZ407Veb2EEYZn3WXY1mJv3sZVnKlxe3E/7bfH5npygUexLcxyON5o7gD53g m+Kw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=7QsELX2b4zYjlGgyKK6SovhZ4mE+qI9YjYk7qrPU0wo=; b=L+XCIREFPg+CM4eK67X3Ls9AEW1pXaEsmVaKa44rHiPMg9VydzZ8VFV3ZuACIUkXoW VFM56E40CXF4cHu+ZG7JJ5WsU6r1cLgfPcJo62gcXAUpVJMox/wMV0hR2idaXrBW3xla aj7OaBvaM+hYluSmgulhSWgWtZsuk0n+gDqjVR8SS1Sn/CpyrTGZHF7GOarF3+3zIR7A Kj5BThNFN9aUe1O4Bj8I9c1dPmhqcS4yiXqFd8gcsolakltOX5Oh5jc1gk8GIU4TPTGY XuJQ97CXmjVmlqiqrrU4FVSUcDj4M0H9rimrYVMe5Vjib1rhGu+HD4o3uZHwb3Fh87tB Mjlg== X-Gm-Message-State: AOAM533gVigMvsHa3cavQuVI0K0BZ1TXpCrRmVHFkZ5rTn3/vAHkws39 kc134zuPotiogt6pWIw+4xaFulH+U7nTAFwk4gY= X-Google-Smtp-Source: ABdhPJx2qfURfbEwyFW4qktv+A5fIlkTLMCqBZahUPc77DrDAO6ToNYtooGeOAIl80LkI4WjSBoXazOHhIJ3TSe3qUs= X-Received: from samitolvanen1.mtv.corp.google.com ([2620:15c:201:2:ce43:4366:95ca:d6e9]) (user=samitolvanen job=sendgmr) by 2002:a05:6214:1c8d:: with SMTP id ib13mr81485qvb.10.1633025141843; Thu, 30 Sep 2021 11:05:41 -0700 (PDT) Date: Thu, 30 Sep 2021 11:05:19 -0700 In-Reply-To: <20210930180531.1190642-1-samitolvanen@google.com> Message-Id: <20210930180531.1190642-4-samitolvanen@google.com> Mime-Version: 1.0 References: <20210930180531.1190642-1-samitolvanen@google.com> X-Mailer: git-send-email 2.33.0.800.g4c38ced690-goog Subject: [PATCH v4 03/15] linkage: Add DECLARE_ASM_FUNC_SYMBOL From: Sami Tolvanen To: x86@kernel.org Cc: Kees Cook , Josh Poimboeuf , Peter Zijlstra , Nathan Chancellor , Nick Desaulniers , Sedat Dilek , linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Sami Tolvanen Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org The kernel has several assembly functions, which are not directly callable from C but need to be referred to from C code. This change adds the DECLARE_ASM_FUNC_SYMBOL macro, which allows us to declare these symbols using an opaque type, which makes misuse harder, and avoids the need to annotate references to the functions for Clang's Control-Flow Integrity (CFI). Suggested-by: Andy Lutomirski Signed-off-by: Sami Tolvanen --- include/linux/linkage.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/include/linux/linkage.h b/include/linux/linkage.h index dbf8506decca..f1eac26b2dd6 100644 --- a/include/linux/linkage.h +++ b/include/linux/linkage.h @@ -48,6 +48,19 @@ #define __PAGE_ALIGNED_DATA .section ".data..page_aligned", "aw" #define __PAGE_ALIGNED_BSS .section ".bss..page_aligned", "aw" +/* + * Declares a function not callable from C using an opaque type. Defined as + * an array to allow the address of the symbol to be taken without '&'. + */ +#ifndef DECLARE_ASM_FUNC_SYMBOL +#define DECLARE_ASM_FUNC_SYMBOL(sym) \ + extern const u8 sym[] +#endif + +#ifndef __ASSEMBLY__ +typedef const u8 *asm_func_ptr; +#endif + /* * This is used by architectures to keep arguments on the stack * untouched by the compiler by keeping them live until the end.