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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 5B579C2BB1D for ; Thu, 12 Mar 2020 14:20:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3931F2071B for ; Thu, 12 Mar 2020 14:20:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727580AbgCLOUS (ORCPT ); Thu, 12 Mar 2020 10:20:18 -0400 Received: from mx2.suse.de ([195.135.220.15]:58356 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727340AbgCLOUM (ORCPT ); Thu, 12 Mar 2020 10:20:12 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 3CAA6B2F1; Thu, 12 Mar 2020 14:20:10 +0000 (UTC) From: Miroslav Benes To: boris.ostrovsky@oracle.com, jgross@suse.com, sstabellini@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, jpoimboe@redhat.com Cc: x86@kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, jslaby@suse.cz, Miroslav Benes Subject: [PATCH 1/2] x86/xen: Make the boot CPU idle task reliable Date: Thu, 12 Mar 2020 15:20:06 +0100 Message-Id: <20200312142007.11488-2-mbenes@suse.cz> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200312142007.11488-1-mbenes@suse.cz> References: <20200312142007.11488-1-mbenes@suse.cz> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: live-patching-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org The unwinder reports the boot CPU idle task's stack on XEN PV as unreliable, which affects at least live patching. There are two reasons for this. First, the task does not follow the x86 convention that its stack starts at the offset right below saved pt_regs. It allows the unwinder to easily detect the end of the stack and verify it. Second, startup_xen() function does not store the return address before jumping to xen_start_kernel() which confuses the unwinder. Amend both issues by moving the starting point of initial stack in startup_xen() and storing the return address before the jump. Signed-off-by: Miroslav Benes --- arch/x86/xen/xen-head.S | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index 1d0cee3163e4..642f346bfe02 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -35,7 +35,7 @@ SYM_CODE_START(startup_xen) rep __ASM_SIZE(stos) mov %_ASM_SI, xen_start_info - mov $init_thread_union+THREAD_SIZE, %_ASM_SP + mov $init_thread_union+THREAD_SIZE-SIZEOF_PTREGS, %_ASM_SP #ifdef CONFIG_X86_64 /* Set up %gs. @@ -51,7 +51,9 @@ SYM_CODE_START(startup_xen) wrmsr #endif + push $1f jmp xen_start_kernel +1: SYM_CODE_END(startup_xen) __FINIT #endif -- 2.25.1