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=-3.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 20ED7C5518A for ; Fri, 24 Apr 2020 04:12:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EE8832075A for ; Fri, 24 Apr 2020 04:12:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UeSf/5Nu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726174AbgDXEMO (ORCPT ); Fri, 24 Apr 2020 00:12:14 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:40314 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725922AbgDXEMN (ORCPT ); Fri, 24 Apr 2020 00:12:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587701532; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1ORnbYYJvOimK1L52WvsWC1QfTySNsKmDnq5F4Mgpto=; b=UeSf/5Nu6THn+yPpTuKjC1daZXfbchBVG4+TpNcp0rGr8o3CbH1iEuIjFK8lHCO1tep7kC HWzhAqzLZEtSwd+bLq2ic5Kf6HaneR8aeR1oaGdYRFecDZanUhp5QnSNEUf1srLilzK/HP qOToL7oZHZ1AhpG4LlDK637XYn6CnhE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-200-lVzwMglxMhKl9T9PGTuJzQ-1; Fri, 24 Apr 2020 00:12:09 -0400 X-MC-Unique: lVzwMglxMhKl9T9PGTuJzQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A4B67835B47; Fri, 24 Apr 2020 04:12:07 +0000 (UTC) Received: from treble (ovpn-118-207.rdu2.redhat.com [10.10.118.207]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5764D100164D; Fri, 24 Apr 2020 04:12:03 +0000 (UTC) Date: Thu, 23 Apr 2020 23:12:01 -0500 From: Josh Poimboeuf To: Joe Lawrence Cc: Miroslav Benes , 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 Subject: Re: [PATCH v2 6/9] s390/module: Use s390_kernel_write() for late relocations Message-ID: <20200424041201.ekbx6wvl3dn45zfl@treble> 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> <20200424023521.GA22117@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200424023521.GA22117@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 23, 2020 at 10:35:21PM -0400, Joe Lawrence wrote: > > 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 ba= se, Elf_Sym *symtab, > > =20 > > gotent =3D me->core_layout.base + me->arch.got_offset + > > info->got_offset; > > - *gotent =3D val; > > + write(gotent, &val, sizeof(*gotent)); > > info->got_initialized =3D 1; > > } > > val =3D 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 =3D=3D 0) { > > - unsigned int *ip; > > + unsigned int *ip, insn[5]; > > + > > ip =3D me->core_layout.base + me->arch.plt_offset + > > info->plt_offset; >=20 > Would it be too paranoid to declare: >=20 > const unsigned int *ip =3D me->core_layout.base +=20 > me->arch.plt_offset + > info->plt_offset; >=20 > That would trip an assignment to read-only error if someone were tempte= d > to write directly through the pointer in the future. Ditto for Elf_Add= r > *gotent pointer in the R_390_GOTPLTENT case. The only problem is then the write() triggers a warning because then we *are* trying to write through the pointer :-) arch/s390/kernel/module.c:300:10: warning: passing argument 1 of =E2=80=98= write=E2=80=99 discards =E2=80=98const=E2=80=99 qualifier from pointer ta= rget type [-Wdiscarded-qualifiers] 300 | write(gotent, &val, sizeof(*gotent)); --=20 Josh