From patchwork Thu Mar 19 09:56:05 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miroslav Benes X-Patchwork-Id: 11446981 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 26B491874 for ; Thu, 19 Mar 2020 09:57:37 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0CF9220722 for ; Thu, 19 Mar 2020 09:57:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0CF9220722 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jEruP-0007xW-5z; Thu, 19 Mar 2020 09:56:13 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jEruO-0007xG-Iw for xen-devel@lists.xenproject.org; Thu, 19 Mar 2020 09:56:12 +0000 X-Inumbo-ID: dcbc682c-69c7-11ea-b34e-bc764e2007e4 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id dcbc682c-69c7-11ea-b34e-bc764e2007e4; Thu, 19 Mar 2020 09:56:11 +0000 (UTC) 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 C6909AE59; Thu, 19 Mar 2020 09:56:10 +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 Date: Thu, 19 Mar 2020 10:56:05 +0100 Message-Id: <20200319095606.23627-2-mbenes@suse.cz> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200319095606.23627-1-mbenes@suse.cz> References: <20200319095606.23627-1-mbenes@suse.cz> MIME-Version: 1.0 Subject: [Xen-devel] [PATCH v2 1/2] x86/xen: Make the boot CPU idle task reliable X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: andrew.cooper3@citrix.com, x86@kernel.org, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, xen-devel@lists.xenproject.org, Miroslav Benes , jslaby@suse.cz Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" 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, which is exactly what call instruction does. Signed-off-by: Miroslav Benes --- arch/x86/xen/xen-head.S | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index 1d0cee3163e4..edc776af0e0a 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -35,7 +35,11 @@ SYM_CODE_START(startup_xen) rep __ASM_SIZE(stos) mov %_ASM_SI, xen_start_info - mov $init_thread_union+THREAD_SIZE, %_ASM_SP +#ifdef CONFIG_X86_64 + mov initial_stack(%rip), %_ASM_SP +#else + mov pa(initial_stack), %_ASM_SP +#endif #ifdef CONFIG_X86_64 /* Set up %gs. @@ -51,7 +55,7 @@ SYM_CODE_START(startup_xen) wrmsr #endif - jmp xen_start_kernel + call xen_start_kernel SYM_CODE_END(startup_xen) __FINIT #endif