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 X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E65E4C3F2D2 for ; Tue, 3 Mar 2020 02:48:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BDE3524699 for ; Tue, 3 Mar 2020 02:48:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583203720; bh=QylDUZK3QTKd3//3nJslpmnCls/OiFTo4MnS8zfcwbA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Y1vjhkb6oUeLPe10bQJSuPRTOkpGnozm5K/vfA8wEZ5GLP6C5B9/uWe7HZW7H8rkN 5HzIn7PB5rlhbUNQH/3BTLuYwzJlI/75ET7SWDZpfhaMnYHeBie5QV4oTsG00dTR61 17Y0vGFfpn3mJ48zcTxtX2Rre1Rk+VJrb5Za+ra8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728486AbgCCCsj (ORCPT ); Mon, 2 Mar 2020 21:48:39 -0500 Received: from mail.kernel.org ([198.145.29.99]:44472 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728409AbgCCCsi (ORCPT ); Mon, 2 Mar 2020 21:48:38 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DEF81246A1; Tue, 3 Mar 2020 02:48:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583203717; bh=QylDUZK3QTKd3//3nJslpmnCls/OiFTo4MnS8zfcwbA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2ARjvncwPq8cRLXN7zBdPxDK2tctsr+3XV3TKKs2tWtxWrTOjmYEfO8nGQKWAdvos HfPEa0uyNpN28eWh4x8KuUdJAlxGQvt5qEQtAJbbdYjXakcmJ6Xw0IxetSEks24IME uQy+55tVfWO6TZsMDtuGgMg7LZTZy9xvK2hr1s44= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Kees Cook , Juergen Gross , Boris Ostrovsky , Sasha Levin , xen-devel@lists.xenproject.org, clang-built-linux@googlegroups.com Subject: [PATCH AUTOSEL 5.4 47/58] x86/xen: Distribute switch variables for initialization Date: Mon, 2 Mar 2020 21:47:29 -0500 Message-Id: <20200303024740.9511-47-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200303024740.9511-1-sashal@kernel.org> References: <20200303024740.9511-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Kees Cook [ Upstream commit 9038ec99ceb94fb8d93ade5e236b2928f0792c7c ] Variables declared in a switch statement before any case statements cannot be automatically initialized with compiler instrumentation (as they are not part of any execution flow). With GCC's proposed automatic stack variable initialization feature, this triggers a warning (and they don't get initialized). Clang's automatic stack variable initialization (via CONFIG_INIT_STACK_ALL=y) doesn't throw a warning, but it also doesn't initialize such variables[1]. Note that these warnings (or silent skipping) happen before the dead-store elimination optimization phase, so even when the automatic initializations are later elided in favor of direct initializations, the warnings remain. To avoid these problems, move such variables into the "case" where they're used or lift them up into the main function body. arch/x86/xen/enlighten_pv.c: In function ‘xen_write_msr_safe’: arch/x86/xen/enlighten_pv.c:904:12: warning: statement will never be executed [-Wswitch-unreachable] 904 | unsigned which; | ^~~~~ [1] https://bugs.llvm.org/show_bug.cgi?id=44916 Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20200220062318.69299-1-keescook@chromium.org Reviewed-by: Juergen Gross [boris: made @which an 'unsigned int'] Signed-off-by: Boris Ostrovsky Signed-off-by: Sasha Levin --- arch/x86/xen/enlighten_pv.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index 6ea215cdeadac..6d4d8a5700b71 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -905,14 +905,15 @@ static u64 xen_read_msr_safe(unsigned int msr, int *err) static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high) { int ret; +#ifdef CONFIG_X86_64 + unsigned int which; + u64 base; +#endif ret = 0; switch (msr) { #ifdef CONFIG_X86_64 - unsigned which; - u64 base; - case MSR_FS_BASE: which = SEGBASE_FS; goto set; case MSR_KERNEL_GS_BASE: which = SEGBASE_GS_USER; goto set; case MSR_GS_BASE: which = SEGBASE_GS_KERNEL; goto set; -- 2.20.1