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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 03D1AC04AAF for ; Mon, 20 May 2019 09:39:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D7D2520859 for ; Mon, 20 May 2019 09:39:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730531AbfETJju (ORCPT ); Mon, 20 May 2019 05:39:50 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:32956 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727720AbfETJju (ORCPT ); Mon, 20 May 2019 05:39:50 -0400 Received: from LHREML714-CAH.china.huawei.com (unknown [172.18.7.107]) by Forcepoint Email with ESMTP id 4A75E6FA85003A8236AE; Mon, 20 May 2019 10:39:48 +0100 (IST) Received: from [10.220.96.108] (10.220.96.108) by smtpsuk.huawei.com (10.201.108.37) with Microsoft SMTP Server (TLS) id 14.3.408.0; Mon, 20 May 2019 10:39:40 +0100 Subject: Re: [PATCH v3 2/2] initramfs: introduce do_readxattrs() To: Arvind Sankar , "H. Peter Anvin" CC: , , , , , , , , , , , , , , , References: <20190517165519.11507-1-roberto.sassu@huawei.com> <20190517165519.11507-3-roberto.sassu@huawei.com> <20190517210219.GA5998@rani.riverdale.lan> <20190517221731.GA11358@rani.riverdale.lan> From: Roberto Sassu Message-ID: <7bdca169-7a01-8c55-40e4-a832e876a0e5@huawei.com> Date: Mon, 20 May 2019 11:39:46 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <20190517221731.GA11358@rani.riverdale.lan> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.220.96.108] X-CFilter-Loop: Reflected Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 5/18/2019 12:17 AM, Arvind Sankar wrote: > On Fri, May 17, 2019 at 02:47:31PM -0700, H. Peter Anvin wrote: >> On 5/17/19 2:02 PM, Arvind Sankar wrote: >>> On Fri, May 17, 2019 at 01:18:11PM -0700, hpa@zytor.com wrote: >>>> >>>> Ok... I just realized this does not work for a modular initramfs, composed at load time from multiple files, which is a very real problem. Should be easy enough to deal with: instead of one large file, use one companion file per source file, perhaps something like filename..xattrs (suggesting double dots to make it less likely to conflict with a "real" file.) No leading dot, as it makes it more likely that archivers will sort them before the file proper. >>> This version of the patch was changed from the previous one exactly to deal with this case -- >>> it allows for the bootloader to load multiple initramfs archives, each >>> with its own .xattr-list file, and to have that work properly. >>> Could you elaborate on the issue that you see? >>> >> >> Well, for one thing, how do you define "cpio archive", each with its own >> .xattr-list file? Second, that would seem to depend on the ordering, no, >> in which case you depend critically on .xattr-list file following the >> files, which most archivers won't do. >> >> Either way it seems cleaner to have this per file; especially if/as it >> can be done without actually mucking up the format. >> >> I need to run, but I'll post a more detailed explanation of what I did >> in a little bit. >> >> -hpa >> > Not sure what you mean by how do I define it? Each cpio archive will > contain its own .xattr-list file with signatures for the files within > it, that was the idea. > > You need to review the code more closely I think -- it does not depend > on the .xattr-list file following the files to which it applies. > > The code first extracts .xattr-list as though it was a regular file. If > a later dupe shows up (presumably from a second archive, although the > patch will actually allow a second one in the same archive), it will > then process the existing .xattr-list file and apply the attributes > listed within it. It then will proceed to read the second one and > overwrite the first one with it (this is the normal behaviour in the > kernel cpio parser). At the end once all the archives have been > extracted, if there is an .xattr-list file in the rootfs it will be > parsed (it would've been the last one encountered, which hasn't been > parsed yet, just extracted). > > Regarding the idea to use the high 16 bits of the mode field in > the header that's another possibility. It would just require additional > support in the program that actually creates the archive though, which > the current patch doesn't. Yes, for adding signatures for a subset of files, no changes to the ram disk generator are necessary. Everything is done by a custom module. To support a generic use case, it would be necessary to modify the generator to execute getfattr and the awk script after files have been placed in the temporary directory. If I understood the new proposal correctly, it would be task for cpio to read file metadata after the content and create a new record for each file with mode 0x18000, type of metadata encoded in the file name and metadata as file content. I don't know how easy it would be to modify cpio. Probably the amount of changes would be reasonable. The kernel will behave in a similar way. It will call do_readxattrs() in do_copy() for each file. Since the only difference between the current and the new proposal would be two additional calls to do_readxattrs() in do_name() and unpack_to_rootfs(), maybe we could support both. Roberto -- HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Bo PENG, Jian LI, Yanli SHI