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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 CFF5BC433FF for ; Wed, 7 Aug 2019 11:41:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AEB7A218FE for ; Wed, 7 Aug 2019 11:41:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387507AbfHGLlK convert rfc822-to-8bit (ORCPT ); Wed, 7 Aug 2019 07:41:10 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([146.101.78.151]:33004 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726873AbfHGLlK (ORCPT ); Wed, 7 Aug 2019 07:41:10 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-105-UxpvcEd0PjOivqu6C53zeA-1; Wed, 07 Aug 2019 12:41:07 +0100 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b::d117) by AcuMS.aculab.com (fd9f:af1c:a25b::d117) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Wed, 7 Aug 2019 12:41:06 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Wed, 7 Aug 2019 12:41:06 +0100 From: David Laight To: "'john.hubbard@gmail.com'" , "H . Peter Anvin" CC: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "x86@kernel.org" , LKML , John Hubbard Subject: RE: [PATCH v2] x86/boot: save fields explicitly, zero out everything else Thread-Topic: [PATCH v2] x86/boot: save fields explicitly, zero out everything else Thread-Index: AQHVR2NW7IoEB4DZD0igIVYuZS+m96bvl74Q Date: Wed, 7 Aug 2019 11:41:06 +0000 Message-ID: <531b38aaa15e4de79a5e27fd37c04351@AcuMS.aculab.com> References: <20190731054627.5627-1-jhubbard@nvidia.com> <20190731054627.5627-2-jhubbard@nvidia.com> In-Reply-To: <20190731054627.5627-2-jhubbard@nvidia.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-MC-Unique: UxpvcEd0PjOivqu6C53zeA-1 X-Mimecast-Spam-Score: 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: john.hubbard@gmail.com > Sent: 31 July 2019 06:46 > > Recent gcc compilers (gcc 9.1) generate warnings about an > out of bounds memset, if you trying memset across several fields > of a struct. This generated a couple of warnings on x86_64 builds. > > Fix this by explicitly saving the fields in struct boot_params > that are intended to be preserved, and zeroing all the rest. > > Suggested-by: Thomas Gleixner > Suggested-by: H. Peter Anvin > Signed-off-by: John Hubbard > --- > arch/x86/include/asm/bootparam_utils.h | 62 +++++++++++++++++++------- > 1 file changed, 47 insertions(+), 15 deletions(-) > > diff --git a/arch/x86/include/asm/bootparam_utils.h b/arch/x86/include/asm/bootparam_utils.h > index 101eb944f13c..514aee24b8de 100644 > --- a/arch/x86/include/asm/bootparam_utils.h > +++ b/arch/x86/include/asm/bootparam_utils.h > @@ -18,6 +18,20 @@ > * Note: efi_info is commonly left uninitialized, but that field has a > * private magic, so it is better to leave it unchanged. > */ > + > +#define sizeof_mbr(type, member) ({ sizeof(((type *)0)->member); }) > + > +#define BOOT_PARAM_PRESERVE(struct_member) \ > + { \ > + .start = offsetof(struct boot_params, struct_member), \ > + .len = sizeof_mbr(struct boot_params, struct_member), \ > + } > + > +struct boot_params_to_save { > + unsigned int start; > + unsigned int len; > +}; > + > static void sanitize_boot_params(struct boot_params *boot_params) > { > /* > @@ -35,21 +49,39 @@ static void sanitize_boot_params(struct boot_params *boot_params) > * problems again. > */ > if (boot_params->sentinel) { > - /* fields in boot_params are left uninitialized, clear them */ > - boot_params->acpi_rsdp_addr = 0; > - memset(&boot_params->ext_ramdisk_image, 0, > - (char *)&boot_params->efi_info - > - (char *)&boot_params->ext_ramdisk_image); > - memset(&boot_params->kbd_status, 0, > - (char *)&boot_params->hdr - > - (char *)&boot_params->kbd_status); > - memset(&boot_params->_pad7[0], 0, > - (char *)&boot_params->edd_mbr_sig_buffer[0] - > - (char *)&boot_params->_pad7[0]); > - memset(&boot_params->_pad8[0], 0, > - (char *)&boot_params->eddbuf[0] - > - (char *)&boot_params->_pad8[0]); > - memset(&boot_params->_pad9[0], 0, sizeof(boot_params->_pad9)); ... How about replacing the above first using: #define zero_struct_fields(ptr, from, to) memset(&ptr->from, 0, (char *)&ptr->to - (char *)&ptr->from) zero_struct_fields(boot_params, ext_ramdisk_image, efi_info); ... Which is absolutely identical to the original code. The replacing the define with: #define so(s, m) offsetof(typeof(*s), m) #define zero_struct_fields(ptr, from, to) memset((char *)ptr + so(ptr, from), 0, so(ptr, to) - so(ptr, from)) which gcc probably doesn't complain about, but should generate identical code again. There might be an existing define for so(). David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)