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=-7.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 C8B85C04AB5 for ; Fri, 7 Jun 2019 00:50:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7B93720840 for ; Fri, 7 Jun 2019 00:50:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=neuling.org header.i=@neuling.org header.b="jubTl1Xv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727922AbfFGAuk (ORCPT ); Thu, 6 Jun 2019 20:50:40 -0400 Received: from bilbo.ozlabs.org ([203.11.71.1]:52993 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726379AbfFGAuk (ORCPT ); Thu, 6 Jun 2019 20:50:40 -0400 Received: from neuling.org (localhost [127.0.0.1]) by ozlabs.org (Postfix) with ESMTP id 45KkTn2QZnz9sDX; Fri, 7 Jun 2019 10:50:37 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=neuling.org; s=201811; t=1559868637; bh=U7nqidMeM/8XknoLlxj1vv8Py2UMz+gk+UbXzxDB/rU=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=jubTl1Xvy/MvBXMf1gKQk4fyUBHQ3Bl2M5rF752yfwnHKWsWX3kzbX2FffletZ9wq dc3RN39kLZunPSXp1JtabJ7hZZ0vpx09/rHI0iooM9b3aRSQo3JH1b2vpGEXqLTSDH NzuMAJ+oWy+2pQmVIaRfpzSJ4RTHjZRnwgwnY468O3O/IoBemdmL96ZOcAQ3pTIm5B toNb7AfP2RWk/Tk5CYj4mjTWOPTkcn5rm+blRpHO1H8qfAbGfoV0DOUt1rYmg5uWOm VOZRGS9FCrcKs7gn6gEBOpauXPFImAFjmvcn+ZcHfs5F5DFPM3+xV1xy1QU31adn9S UxOae1rZD4ukQ== Received: by neuling.org (Postfix, from userid 1000) id 49C912A27C4; Fri, 7 Jun 2019 10:50:37 +1000 (AEST) Message-ID: <80cfc8d7327d3bb744ea1f7e2843943a998d48de.camel@neuling.org> Subject: Re: [PATCH] Powerpc/Watchpoint: Restore nvgprs while returning from exception From: Michael Neuling To: Ravi Bangoria , mpe@ellerman.id.au Cc: benh@kernel.crashing.org, paulus@samba.org, npiggin@gmail.com, christophe.leroy@c-s.fr, mahesh@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Date: Fri, 07 Jun 2019 10:50:37 +1000 In-Reply-To: <20190606072951.32116-1-ravi.bangoria@linux.ibm.com> References: <20190606072951.32116-1-ravi.bangoria@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.32.2 (3.32.2-1.fc30) MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2019-06-06 at 12:59 +0530, Ravi Bangoria wrote: > Powerpc hw triggers watchpoint before executing the instruction. > To make trigger-after-execute behavior, kernel emulates the > instruction. If the instruction is 'load something into non- > volatile register', exception handler should restore emulated > register state while returning back, otherwise there will be > register state corruption. Ex, Adding a watchpoint on a list > can corrput the list: >=20 > # cat /proc/kallsyms | grep kthread_create_list > c00000000121c8b8 d kthread_create_list >=20 > Add watchpoint on kthread_create_list->next: >=20 > # perf record -e mem:0xc00000000121c8c0 >=20 > Run some workload such that new kthread gets invoked. Ex, I > just logged out from console: >=20 > list_add corruption. next->prev should be prev (c000000001214e00), \ > but was c00000000121c8b8. (next=3Dc00000000121c8b8). > WARNING: CPU: 59 PID: 309 at lib/list_debug.c:25 __list_add_valid+0xb4/= 0xc0 > CPU: 59 PID: 309 Comm: kworker/59:0 Kdump: loaded Not tainted 5.1.0-rc7= + #69 > ... > NIP __list_add_valid+0xb4/0xc0 > LR __list_add_valid+0xb0/0xc0 > Call Trace: > __list_add_valid+0xb0/0xc0 (unreliable) > __kthread_create_on_node+0xe0/0x260 > kthread_create_on_node+0x34/0x50 > create_worker+0xe8/0x260 > worker_thread+0x444/0x560 > kthread+0x160/0x1a0 > ret_from_kernel_thread+0x5c/0x70 >=20 > Signed-off-by: Ravi Bangoria How long has this been around? Should we be CCing stable? Mikey > --- > arch/powerpc/kernel/exceptions-64s.S | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >=20 > diff --git a/arch/powerpc/kernel/exceptions-64s.S > b/arch/powerpc/kernel/exceptions-64s.S > index 9481a11..96de0d1 100644 > --- a/arch/powerpc/kernel/exceptions-64s.S > +++ b/arch/powerpc/kernel/exceptions-64s.S > @@ -1753,7 +1753,7 @@ handle_dabr_fault: > ld r5,_DSISR(r1) > addi r3,r1,STACK_FRAME_OVERHEAD > bl do_break > -12: b ret_from_except_lite > +12: b ret_from_except > =20 > =20 > #ifdef CONFIG_PPC_BOOK3S_64