From patchwork Mon May 16 20:54:38 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Markus Boehme X-Patchwork-Id: 573232 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 41CADC433EF for ; Mon, 16 May 2022 21:14:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348029AbiEPVN7 (ORCPT ); Mon, 16 May 2022 17:13:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34998 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350362AbiEPVM0 (ORCPT ); Mon, 16 May 2022 17:12:26 -0400 X-Greylist: delayed 539 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Mon, 16 May 2022 14:04:08 PDT Received: from mout-p-103.mailbox.org (mout-p-103.mailbox.org [80.241.56.161]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1360D40904 for ; Mon, 16 May 2022 14:04:07 -0700 (PDT) Received: from smtp202.mailbox.org (smtp202.mailbox.org [IPv6:2001:67c:2050:b231:465::202]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-103.mailbox.org (Postfix) with ESMTPS id 4L2BN35B62z9sSh; Mon, 16 May 2022 22:55:15 +0200 (CEST) From: Markus Boehme To: stable@vger.kernel.org Cc: Miroslav Benes , Juergen Gross , Markus Boehme Subject: [PATCH 1/2] x86/xen: Make the boot CPU idle task reliable Date: Mon, 16 May 2022 22:54:38 +0200 Message-Id: <20220516205439.255114-2-markubo@amazon.com> In-Reply-To: <20220516205439.255114-1-markubo@amazon.com> References: <20220516205439.255114-1-markubo@amazon.com> MIME-Version: 1.0 X-MBO-RS-ID: 7bdcb081f16ce2e07b8 X-MBO-RS-META: t98x48y3ycm1ukc7wzmts4c9qnpmptrg X-Rspamd-Queue-Id: 4L2BN35B62z9sSh Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Miroslav Benes upstream commit 2f62f36e62daec43aa7b9633ef7f18e042a80bed 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 Reviewed-by: Juergen Gross Signed-off-by: Juergen Gross Signed-off-by: Markus Boehme --- 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 c1d8b90aa4e2..deb6abe5d346 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -35,7 +35,11 @@ ENTRY(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), %rsp +#else + mov pa(initial_stack), %esp +#endif #ifdef CONFIG_X86_64 /* Set up %gs. @@ -51,7 +55,7 @@ ENTRY(startup_xen) wrmsr #endif - jmp xen_start_kernel + call xen_start_kernel END(startup_xen) __FINIT #endif