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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 4946EC76186 for ; Wed, 24 Jul 2019 20:00:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1E17022ADA for ; Wed, 24 Jul 2019 20:00:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563998400; bh=/+pFugCSIqfhfErvc6YLgXqeyrlG/zIJSFs2/GxY+F4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=dF9M9dgMRbucdK+rYG7fYd2gYrovxAfmoXng+ER31WnmW3+9Od0O/l1x32xExa/GN w+rm+EPq4rYfRmyJcdPT/UZZJ88NAJvySut1aIzIfwVYRraCrAo/+tHa7BZhrLlyVD 54dl1nMsFGoZMDdqCH6jz6s+wnr3dh6E5zB1x8/E= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392263AbfGXT77 (ORCPT ); Wed, 24 Jul 2019 15:59:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:47528 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392142AbfGXT74 (ORCPT ); Wed, 24 Jul 2019 15:59:56 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BB78022ADA; Wed, 24 Jul 2019 19:59:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563998395; bh=/+pFugCSIqfhfErvc6YLgXqeyrlG/zIJSFs2/GxY+F4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QStOJCJok3xwb5E9TasOrJyNon8Bs83WkmfnyPMaV7Xf0p0zDMDOn9uc7pOy1go0A uQRQwdWcA270BQki+i/Ij/sh6uJtgsagzl/FA0KAJ1RXs/c+JZJF2S8FoKz/E5A8o1 hn3NDN6/R+BBUyRadrZ2TECgPmSEAJtFuVCMFArs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ravi Bangoria , Michael Ellerman Subject: [PATCH 5.1 351/371] powerpc/watchpoint: Restore NV GPRs while returning from exception Date: Wed, 24 Jul 2019 21:21:43 +0200 Message-Id: <20190724191750.222689727@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190724191724.382593077@linuxfoundation.org> References: <20190724191724.382593077@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ravi Bangoria commit f474c28fbcbe42faca4eb415172c07d76adcb819 upstream. powerpc hardware 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. eg, adding a watchpoint on a list can corrput the list: # cat /proc/kallsyms | grep kthread_create_list c00000000121c8b8 d kthread_create_list Add watchpoint on kthread_create_list->prev: # perf record -e mem:0xc00000000121c8c0 Run some workload such that new kthread gets invoked. eg, I just logged out from console: list_add corruption. next->prev should be prev (c000000001214e00), \ but was c00000000121c8b8. (next=c00000000121c8b8). 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 List corruption happened because it uses 'load into non-volatile register' instruction: Snippet from __kthread_create_on_node: c000000000136be8: addis r29,r2,-19 c000000000136bec: ld r29,31424(r29) if (!__list_add_valid(new, prev, next)) c000000000136bf0: mr r3,r30 c000000000136bf4: mr r5,r28 c000000000136bf8: mr r4,r29 c000000000136bfc: bl c00000000059a2f8 <__list_add_valid+0x8> Register state from WARN_ON(): GPR00: c00000000059a3a0 c000007ff23afb50 c000000001344e00 0000000000000075 GPR04: 0000000000000000 0000000000000000 0000001852af8bc1 0000000000000000 GPR08: 0000000000000001 0000000000000007 0000000000000006 00000000000004aa GPR12: 0000000000000000 c000007ffffeb080 c000000000137038 c000005ff62aaa00 GPR16: 0000000000000000 0000000000000000 c000007fffbe7600 c000007fffbe7370 GPR20: c000007fffbe7320 c000007fffbe7300 c000000001373a00 0000000000000000 GPR24: fffffffffffffef7 c00000000012e320 c000007ff23afcb0 c000000000cb8628 GPR28: c00000000121c8b8 c000000001214e00 c000007fef5b17e8 c000007fef5b17c0 Watchpoint hit at 0xc000000000136bec. addis r29,r2,-19 => r29 = 0xc000000001344e00 + (-19 << 16) => r29 = 0xc000000001214e00 ld r29,31424(r29) => r29 = *(0xc000000001214e00 + 31424) => r29 = *(0xc00000000121c8c0) 0xc00000000121c8c0 is where we placed a watchpoint and thus this instruction was emulated by emulate_step. But because handle_dabr_fault did not restore emulated register state, r29 still contains stale value in above register state. Fixes: 5aae8a5370802 ("powerpc, hw_breakpoints: Implement hw_breakpoints for 64-bit server processors") Signed-off-by: Ravi Bangoria Cc: stable@vger.kernel.org # 2.6.36+ Signed-off-by: Michael Ellerman Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/exceptions-64s.S | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -1738,7 +1738,7 @@ handle_page_fault: addi r3,r1,STACK_FRAME_OVERHEAD bl do_page_fault cmpdi r3,0 - beq+ 12f + beq+ ret_from_except_lite bl save_nvgprs mr r5,r3 addi r3,r1,STACK_FRAME_OVERHEAD @@ -1753,7 +1753,12 @@ handle_dabr_fault: ld r5,_DSISR(r1) addi r3,r1,STACK_FRAME_OVERHEAD bl do_break -12: b ret_from_except_lite + /* + * do_break() may have changed the NV GPRS while handling a breakpoint. + * If so, we need to restore them with their updated values. Don't use + * ret_from_except_lite here. + */ + b ret_from_except #ifdef CONFIG_PPC_BOOK3S_64