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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1317DC43219 for ; Mon, 4 Apr 2022 21:50:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233931AbiDDVvl convert rfc822-to-8bit (ORCPT ); Mon, 4 Apr 2022 17:51:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43922 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379415AbiDDRJO (ORCPT ); Mon, 4 Apr 2022 13:09:14 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 69EB340A22 for ; Mon, 4 Apr 2022 10:07:17 -0700 (PDT) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-170-mCYWs2NyMrqY9YLkljzOvg-1; Mon, 04 Apr 2022 18:07:14 +0100 X-MC-Unique: mCYWs2NyMrqY9YLkljzOvg-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.32; Mon, 4 Apr 2022 18:07:11 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.033; Mon, 4 Apr 2022 18:07:11 +0100 From: David Laight To: "'Maciej W. Rozycki'" , Kees Cook CC: James Jones , "bp@alien8.de" , "x86@kernel.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH] x86: Remove a.out support Thread-Topic: [PATCH] x86: Remove a.out support Thread-Index: AQHYSBOog1urTOlT506l8VY6NMoEJKzf++oQ Date: Mon, 4 Apr 2022 17:07:11 +0000 Message-ID: <08c095230941445f9139ab89bc70da43@AcuMS.aculab.com> References: <4c449fab-8135-5057-7d2c-7b948ce130cc@theinnocuous.com> <0b31b1d3-852d-6cab-82ae-5eecaec05679@theinnocuous.com> <202203151150.1CDB1D8DA@keescook> <67CF27C5-5013-4EF4-B24C-8D9EB52536FB@chromium.org> In-Reply-To: Accept-Language: en-GB, 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 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Maciej W. Rozycki > Sent: 04 April 2022 12:04 > > On Sat, 2 Apr 2022, Kees Cook wrote: > > > > Chiming in late as I'm scanning outstanding mailing list traffic: if this > > >is as you say all statically linked stuff, then converting from a.out to > > >ELF might be as easy as: > > > > > >$ objcopy -I a.out-i386-linux -O elf32-i386 a.out-binary elf-binary > > > > Based on my research (and the wrapper I ended up writing), I don't think > > this is sufficient because entry point handling is different between ELF > > and a.out (specifically the stack layout and initial sp register value). > > Fair enough. I guess the exact value of %esp doesn't matter that much > (why would it?), but the arguments and environment may well be structured > differently (and indeed based on a glance over binfmt_aout.c there's extra > indirection involved compared to the ELF i386 psABI). You could write a custom 'elf interpreter'. Hacking at those isn't for the faint-hearted :-) David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)