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=-11.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 63AF1C433E2 for ; Thu, 17 Sep 2020 13:40:09 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 314572075E for ; Thu, 17 Sep 2020 13:40:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="U9BaAeej" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 314572075E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4BsdPd72jFzDqgp for ; Thu, 17 Sep 2020 23:40:05 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.ibm.com (client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=rcardoso@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=U9BaAeej; dkim-atps=neutral Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4Bsd5V74PrzDqNH for ; Thu, 17 Sep 2020 23:26:06 +1000 (AEST) Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 08HDJhOu107007; Thu, 17 Sep 2020 09:25:58 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=pp1; bh=6tiVtpObG1jc9y3j7QUgB4f6VYVXThdByx1D34/MMJY=; b=U9BaAeejVyKvhcV5+90Bb6UTcyBd9o404DS374TK8zcNdRhpmiR1bNWSachMFDv+6gA7 TiZD/CVN0YSEuvQqQ2F/rLCpyPUWZk/AWUgu3dcVCfQwlVw3jTthQU5Sz7m4xOn+4HFP Wq1QEPy99VSV4tn6QWnpjXdrDe+1gnAnrV6kJbmBt9BcAFa1qziQE+GZhjCQxVJafmvE kQg/giTpv6zDinHRF2dmgwDzMQRS8sbn899bI/Vmzp5zLQBTbE/pt94XnIHo5qaWpKdk 4lgqF5JyNDtjIVZQ2xNXYYJQt07bG9EuUI9QnSk3DulBLdqRaX1fcrdltkewYv2uE4+8 kA== Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 33m8k2r52s-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 17 Sep 2020 09:25:58 -0400 Received: from m0098413.ppops.net (m0098413.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 08HDLAS5110180; Thu, 17 Sep 2020 09:25:57 -0400 Received: from ppma01dal.us.ibm.com (83.d6.3fa9.ip4.static.sl-reverse.com [169.63.214.131]) by mx0b-001b2d01.pphosted.com with ESMTP id 33m8k2r526-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 17 Sep 2020 09:25:57 -0400 Received: from pps.filterd (ppma01dal.us.ibm.com [127.0.0.1]) by ppma01dal.us.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 08HDNEdC029011; Thu, 17 Sep 2020 13:25:57 GMT Received: from b01cxnp22033.gho.pok.ibm.com (b01cxnp22033.gho.pok.ibm.com [9.57.198.23]) by ppma01dal.us.ibm.com with ESMTP id 33k6591e0x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 17 Sep 2020 13:25:57 +0000 Received: from b01ledav005.gho.pok.ibm.com (b01ledav005.gho.pok.ibm.com [9.57.199.110]) by b01cxnp22033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 08HDPurx56623564 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 17 Sep 2020 13:25:56 GMT Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 544E7AE060; Thu, 17 Sep 2020 13:25:56 +0000 (GMT) Received: from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E4287AE05C; Thu, 17 Sep 2020 13:25:52 +0000 (GMT) Received: from localhost.localdomain (unknown [9.211.95.89]) by b01ledav005.gho.pok.ibm.com (Postfix) with ESMTP; Thu, 17 Sep 2020 13:25:52 +0000 (GMT) Subject: Re: [PATCH v6 5/8] powerpc/watchpoint: Fix exception handling for CONFIG_HAVE_HW_BREAKPOINT=N To: Ravi Bangoria , mpe@ellerman.id.au, christophe.leroy@c-s.fr References: <20200902042945.129369-1-ravi.bangoria@linux.ibm.com> <20200902042945.129369-6-ravi.bangoria@linux.ibm.com> From: Rogerio Alves Message-ID: <7632bf52-3a0c-66d7-a236-7f896b1ce13e@linux.ibm.com> Date: Thu, 17 Sep 2020 10:25:51 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200902042945.129369-6-ravi.bangoria@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-09-17_09:2020-09-16, 2020-09-17 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 bulkscore=0 priorityscore=1501 suspectscore=0 impostorscore=0 mlxlogscore=999 lowpriorityscore=0 phishscore=0 adultscore=0 mlxscore=0 spamscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009170098 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mikey@neuling.org, jniethe5@gmail.com, pedromfc@linux.ibm.com, linux-kernel@vger.kernel.org, paulus@samba.org, rogealve@linux.ibm.com, naveen.n.rao@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 9/2/20 1:29 AM, Ravi Bangoria wrote: > On powerpc, ptrace watchpoint works in one-shot mode. i.e. kernel > disables event every time it fires and user has to re-enable it. > Also, in case of ptrace watchpoint, kernel notifies ptrace user > before executing instruction. > > With CONFIG_HAVE_HW_BREAKPOINT=N, kernel is missing to disable > ptrace event and thus it's causing infinite loop of exceptions. > This is especially harmful when user watches on a data which is > also read/written by kernel, eg syscall parameters. In such case, > infinite exceptions happens in kernel mode which causes soft-lockup. > > Fixes: 9422de3e953d ("powerpc: Hardware breakpoints rewrite to handle non DABR breakpoint registers") > Reported-by: Pedro Miraglia Franco de Carvalho > Signed-off-by: Ravi Bangoria Tested-by: Rogerio Alves > --- > arch/powerpc/include/asm/hw_breakpoint.h | 3 ++ > arch/powerpc/kernel/process.c | 48 +++++++++++++++++++++++ > arch/powerpc/kernel/ptrace/ptrace-noadv.c | 4 +- > 3 files changed, 54 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/include/asm/hw_breakpoint.h b/arch/powerpc/include/asm/hw_breakpoint.h > index 81872c420476..abebfbee5b1c 100644 > --- a/arch/powerpc/include/asm/hw_breakpoint.h > +++ b/arch/powerpc/include/asm/hw_breakpoint.h > @@ -18,6 +18,7 @@ struct arch_hw_breakpoint { > u16 type; > u16 len; /* length of the target data symbol */ > u16 hw_len; /* length programmed in hw */ > + u8 flags; > }; > > /* Note: Don't change the first 6 bits below as they are in the same order > @@ -37,6 +38,8 @@ struct arch_hw_breakpoint { > #define HW_BRK_TYPE_PRIV_ALL (HW_BRK_TYPE_USER | HW_BRK_TYPE_KERNEL | \ > HW_BRK_TYPE_HYP) > > +#define HW_BRK_FLAG_DISABLED 0x1 > + > /* Minimum granularity */ > #ifdef CONFIG_PPC_8xx > #define HW_BREAKPOINT_SIZE 0x4 > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c > index 016bd831908e..160fbbf41d40 100644 > --- a/arch/powerpc/kernel/process.c > +++ b/arch/powerpc/kernel/process.c > @@ -636,6 +636,44 @@ void do_send_trap(struct pt_regs *regs, unsigned long address, > (void __user *)address); > } > #else /* !CONFIG_PPC_ADV_DEBUG_REGS */ > + > +static void do_break_handler(struct pt_regs *regs) > +{ > + struct arch_hw_breakpoint null_brk = {0}; > + struct arch_hw_breakpoint *info; > + struct ppc_inst instr = ppc_inst(0); > + int type = 0; > + int size = 0; > + unsigned long ea; > + int i; > + > + /* > + * If underneath hw supports only one watchpoint, we know it > + * caused exception. 8xx also falls into this category. > + */ > + if (nr_wp_slots() == 1) { > + __set_breakpoint(0, &null_brk); > + current->thread.hw_brk[0] = null_brk; > + current->thread.hw_brk[0].flags |= HW_BRK_FLAG_DISABLED; > + return; > + } > + > + /* Otherwise findout which DAWR caused exception and disable it. */ > + wp_get_instr_detail(regs, &instr, &type, &size, &ea); > + > + for (i = 0; i < nr_wp_slots(); i++) { > + info = ¤t->thread.hw_brk[i]; > + if (!info->address) > + continue; > + > + if (wp_check_constraints(regs, instr, ea, type, size, info)) { > + __set_breakpoint(i, &null_brk); > + current->thread.hw_brk[i] = null_brk; > + current->thread.hw_brk[i].flags |= HW_BRK_FLAG_DISABLED; > + } > + } > +} > + > void do_break (struct pt_regs *regs, unsigned long address, > unsigned long error_code) > { > @@ -647,6 +685,16 @@ void do_break (struct pt_regs *regs, unsigned long address, > if (debugger_break_match(regs)) > return; > > + /* > + * We reach here only when watchpoint exception is generated by ptrace > + * event (or hw is buggy!). Now if CONFIG_HAVE_HW_BREAKPOINT is set, > + * watchpoint is already handled by hw_breakpoint_handler() so we don't > + * have to do anything. But when CONFIG_HAVE_HW_BREAKPOINT is not set, > + * we need to manually handle the watchpoint here. > + */ > + if (!IS_ENABLED(CONFIG_HAVE_HW_BREAKPOINT)) > + do_break_handler(regs); > + > /* Deliver the signal to userspace */ > force_sig_fault(SIGTRAP, TRAP_HWBKPT, (void __user *)address); > } > diff --git a/arch/powerpc/kernel/ptrace/ptrace-noadv.c b/arch/powerpc/kernel/ptrace/ptrace-noadv.c > index 57a0ab822334..c9122ed91340 100644 > --- a/arch/powerpc/kernel/ptrace/ptrace-noadv.c > +++ b/arch/powerpc/kernel/ptrace/ptrace-noadv.c > @@ -286,11 +286,13 @@ long ppc_del_hwdebug(struct task_struct *child, long data) > } > return ret; > #else /* CONFIG_HAVE_HW_BREAKPOINT */ > - if (child->thread.hw_brk[data - 1].address == 0) > + if (!(child->thread.hw_brk[data - 1].flags & HW_BRK_FLAG_DISABLED) && > + child->thread.hw_brk[data - 1].address == 0) > return -ENOENT; > > child->thread.hw_brk[data - 1].address = 0; > child->thread.hw_brk[data - 1].type = 0; > + child->thread.hw_brk[data - 1].flags = 0; > #endif /* CONFIG_HAVE_HW_BREAKPOINT */ > > return 0; >