From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760781AbcBYPRE (ORCPT ); Thu, 25 Feb 2016 10:17:04 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:51777 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760412AbcBYPRB (ORCPT ); Thu, 25 Feb 2016 10:17:01 -0500 From: Boris Ostrovsky To: konrad.wilk@oracle.com, david.vrabel@citrix.com Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, mcgrof@kernel.org, brgerst@gmail.com, andrew.cooper3@citrix.com, Boris Ostrovsky , stable@vger.kernel.org Subject: [PATCH v3 1/2] xen/x86: Zero out .bss for PV guests Date: Thu, 25 Feb 2016 10:16:34 -0500 Message-Id: <1456413395-7679-2-git-send-email-boris.ostrovsky@oracle.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1456413395-7679-1-git-send-email-boris.ostrovsky@oracle.com> References: <1456413395-7679-1-git-send-email-boris.ostrovsky@oracle.com> X-Source-IP: aserv0021.oracle.com [141.146.126.233] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Baremetal kernels clear .bss early in the boot but Xen PV guests don't execute that code. They have been able to run without problems because Xen domain builder happens to give out zeroed pages. However, since this is not really guaranteed, .bss should be explicitly cleared. Signed-off-by: Boris Ostrovsky Cc: stable@vger.kernel.org --- arch/x86/xen/xen-head.S | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index b65f59a..11dbe49 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -38,6 +38,20 @@ __INIT ENTRY(startup_xen) cld + +#ifdef CONFIG_X86_32 +#define WSIZE_SHIFT 2 +#else +#define WSIZE_SHIFT 3 +#endif + /* Clear .bss */ + xor %eax,%eax + mov $__bss_start, %__ASM_REG(di) + mov $__bss_stop, %__ASM_REG(cx) + sub %__ASM_REG(di), %__ASM_REG(cx) + shr $WSIZE_SHIFT, %__ASM_REG(cx) + rep __ASM_SIZE(stos) + #ifdef CONFIG_X86_32 mov %esi,xen_start_info mov $init_thread_union+THREAD_SIZE,%esp -- 2.1.0