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=-14.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL 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 867BAC433E0 for ; Tue, 4 Aug 2020 14:48:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6EED52086A for ; Tue, 4 Aug 2020 14:48:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="Zd9gPm9P" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729256AbgHDOsQ (ORCPT ); Tue, 4 Aug 2020 10:48:16 -0400 Received: from linux.microsoft.com ([13.77.154.182]:46302 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729009AbgHDOsN (ORCPT ); Tue, 4 Aug 2020 10:48:13 -0400 Received: from [192.168.254.32] (unknown [47.187.206.220]) by linux.microsoft.com (Postfix) with ESMTPSA id C779220B4908; Tue, 4 Aug 2020 07:48:11 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com C779220B4908 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1596552492; bh=WWoZU5hW4wXDmLDqxKWgVjJhEBnDZrlL0eZeSoA1M0E=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=Zd9gPm9PZos91WvJOt0oayxz099VIuOsWoBZIXUJDFjP7lCj1dlQONa0QNp25lwdY dsm1r5OpjOcAXzNUDHh+nWWnMfnxq0oL6LMUtoVLftLBOD3ttlLrNDioYA+AS/vahh DP92H/rykDhIN5jKmVDwqf9m4OvMWrU04m/O4Ps0= Subject: Re: [PATCH v1 0/4] [RFC] Implement Trampoline File Descriptor To: David Laight , 'Mark Rutland' Cc: Andy Lutomirski , Kernel Hardening , Linux API , linux-arm-kernel , Linux FS Devel , linux-integrity , LKML , LSM List , Oleg Nesterov , X86 ML References: <20200728131050.24443-1-madvenka@linux.microsoft.com> <6540b4b7-3f70-adbf-c922-43886599713a@linux.microsoft.com> <46a1adef-65f0-bd5e-0b17-54856fb7e7ee@linux.microsoft.com> <20200731183146.GD67415@C02TD0UTHF1T.local> <86625441-80f3-2909-2f56-e18e2b60957d@linux.microsoft.com> <20200804135558.GA7440@C02TD0UTHF1T.local> From: "Madhavan T. Venkataraman" Message-ID: <5f3c9616-52f5-f539-a39f-3fd3ada4f0aa@linux.microsoft.com> Date: Tue, 4 Aug 2020 09:48:11 -0500 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: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On 8/4/20 9:33 AM, David Laight wrote: >>> If you look at the libffi reference patch I have included, the architecture >>> specific changes to use trampfd just involve a single C function call to >>> a common code function. > No idea what libffi is, but it must surely be simpler to > rewrite it to avoid nested function definitions. Sorry if I wasn't clear. libffi is a separate use case and GCC nested functions is a separate one. libffi is not used to solve the nested function stuff. For nested functions, GCC generates trampoline code and arranges to place it on the stack and execute it. I agree with your other points about nested function implementation. Madhavan > Or find a book from the 1960s on how to do recursive > calls and nested functions in FORTRAN-IV. > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales)