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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 EE3AAC2BA1A for ; Fri, 24 Apr 2020 07:20:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C996D20700 for ; Fri, 24 Apr 2020 07:20:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726520AbgDXHUm (ORCPT ); Fri, 24 Apr 2020 03:20:42 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:64356 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726317AbgDXHUm (ORCPT ); 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Fri, 24 Apr 2020 07:20:27 +0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 03O7KPA450790596 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 24 Apr 2020 07:20:25 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 457615205A; Fri, 24 Apr 2020 07:20:25 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.145.14.129]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id AC3FD5204E; Fri, 24 Apr 2020 07:20:24 +0000 (GMT) Subject: Re: [PATCH v2 6/9] s390/module: Use s390_kernel_write() for late relocations To: Josh Poimboeuf , Miroslav Benes Cc: Gerald Schaefer , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Jessica Yu , linux-s390@vger.kernel.org, heiko.carstens@de.ibm.com, Vasily Gorbik , Joe Lawrence References: <18266eb2c2c9a2ce0033426837d89dcb363a85d3.1587131959.git.jpoimboe@redhat.com> <20200422164037.7edd21ea@thinkpad> <20200422172126.743908f5@thinkpad> <20200422194605.n77t2wtx5fomxpyd@treble> <20200423141834.234ed0bc@thinkpad> <20200423141228.sjvnxwdqlzoyqdwg@treble> <20200423181030.b5mircvgc7zmqacr@treble> <20200423232657.7minzcsysnhp474w@treble> From: Christian Borntraeger Autocrypt: addr=borntraeger@de.ibm.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200423232657.7minzcsysnhp474w@treble> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.676 definitions=2020-04-24_02:2020-04-23,2020-04-24 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 lowpriorityscore=0 adultscore=0 mlxscore=0 bulkscore=0 clxscore=1011 priorityscore=1501 suspectscore=0 impostorscore=0 malwarescore=0 mlxlogscore=999 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004240052 Sender: live-patching-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On 24.04.20 01:26, Josh Poimboeuf wrote: > On Thu, Apr 23, 2020 at 01:10:30PM -0500, Josh Poimboeuf wrote: >> On Thu, Apr 23, 2020 at 09:12:28AM -0500, Josh Poimboeuf wrote: >>>>> this is strange. While I would have expected an exception similar to >>>>> this, it really should have happened on the "sturg" instruction which >>>>> does the DAT-off store in s390_kernel_write(), and certainly not with >>>>> an ID of 0004 (protection). However, in your case, it happens on a >>>>> normal store instruction, with 0004 indicating a protection exception. >>>>> >>>>> This is more like what I would expect e.g. in the case where you do >>>>> _not_ use the s390_kernel_write() function for RO module text patching, >>>>> but rather normal memory access. So I am pretty sure that this is not >>>>> related to the s390_kernel_write(), but some other issue, maybe some >>>>> place left where you still use normal memory access? >>>> >>>> The call trace above also suggests that it is not a late relocation, no? >>>> The path is from KLP module init function through klp_enable_patch. It should >>>> mean that the to-be-patched object is loaded (it must be a module thanks >>>> to a check klp_init_object_loaded(), vmlinux relocations were processed >>>> earlier in apply_relocations()). >>>> >>>> However, the KLP module state here must be COMING, so s390_kernel_write() >>>> should be used. What are we missing? >>> >>> I'm also scratching my head. It _should_ be using s390_kernel_write() >>> based on the module state, but I don't see that on the stack trace. >>> >>> This trace (and Gerald's comment) seem to imply it's using >>> __builtin_memcpy(), which might expected for UNFORMED state. >>> >>> Weird... >> >> Mystery solved: >> >> $ CROSS_COMPILE=s390x-linux-gnu- scripts/faddr2line vmlinux apply_rela+0x16a/0x520 >> apply_rela+0x16a/0x520: >> apply_rela at arch/s390/kernel/module.c:336 >> >> which corresponds to the following code in apply_rela(): >> >> >> case R_390_PLTOFF64: /* 16 bit offset from GOT to PLT. */ >> if (info->plt_initialized == 0) { >> unsigned int *ip; >> ip = me->core_layout.base + me->arch.plt_offset + >> info->plt_offset; >> ip[0] = 0x0d10e310; /* basr 1,0 */ >> ip[1] = 0x100a0004; /* lg 1,10(1) */ >> >> >> Notice how it's writing directly to text... oops. > > Here's a fix, using write() for the PLT and the GOT. Are you going to provide a proper patch? > > diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c > index 2798329ebb74..fe446f42818f 100644 > --- a/arch/s390/kernel/module.c > +++ b/arch/s390/kernel/module.c > @@ -297,7 +297,7 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab, > > gotent = me->core_layout.base + me->arch.got_offset + > info->got_offset; > - *gotent = val; > + write(gotent, &val, sizeof(*gotent)); > info->got_initialized = 1; > } > val = info->got_offset + rela->r_addend; > @@ -330,25 +330,29 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab, > case R_390_PLTOFF32: /* 32 bit offset from GOT to PLT. */ > case R_390_PLTOFF64: /* 16 bit offset from GOT to PLT. */ > if (info->plt_initialized == 0) { > - unsigned int *ip; > + unsigned int *ip, insn[5]; > + > ip = me->core_layout.base + me->arch.plt_offset + > info->plt_offset; > - ip[0] = 0x0d10e310; /* basr 1,0 */ > - ip[1] = 0x100a0004; /* lg 1,10(1) */ > + > + insn[0] = 0x0d10e310; /* basr 1,0 */ > + insn[1] = 0x100a0004; /* lg 1,10(1) */ > if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_disable) { > unsigned int *ij; > ij = me->core_layout.base + > me->arch.plt_offset + > me->arch.plt_size - PLT_ENTRY_SIZE; > - ip[2] = 0xa7f40000 + /* j __jump_r1 */ > + insn[2] = 0xa7f40000 + /* j __jump_r1 */ > (unsigned int)(u16) > (((unsigned long) ij - 8 - > (unsigned long) ip) / 2); > } else { > - ip[2] = 0x07f10000; /* br %r1 */ > + insn[2] = 0x07f10000; /* br %r1 */ > } > - ip[3] = (unsigned int) (val >> 32); > - ip[4] = (unsigned int) val; > + insn[3] = (unsigned int) (val >> 32); > + insn[4] = (unsigned int) val; > + > + write(ip, insn, sizeof(insn)); > info->plt_initialized = 1; > } > if (r_type == R_390_PLTOFF16 || >