From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752651AbdKENGP (ORCPT ); Sun, 5 Nov 2017 08:06:15 -0500 Received: from mail-wr0-f171.google.com ([209.85.128.171]:47904 "EHLO mail-wr0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751615AbdKENGM (ORCPT ); Sun, 5 Nov 2017 08:06:12 -0500 X-Google-Smtp-Source: ABhQp+Ts9NRFfR71uQrDTgcSkTQFtupZW3a+bxC/f5sR2cFzQMo3RkmEAAxm96pqjKnBjiHhKuAM0w== Date: Sun, 5 Nov 2017 14:06:08 +0100 From: Pali =?utf-8?B?Um9ow6Fy?= To: Andreas Bombe , Karel Zak , util-linux@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Andrius =?utf-8?B?xaB0aWtvbmFz?= , Curtis Gedak Subject: Re: Linux & FAT32 label Message-ID: <20171105130608.5oww3b2fnnrwe7ok@pali> References: <20171004153332.GA6696@pali> <20171011212435.znmtdnsxcd5ectub@pali> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20171011212435.znmtdnsxcd5ectub@pali> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 11 October 2017 23:24:35 Pali Rohár wrote: > On Wednesday 04 October 2017 17:33:32 Pali Rohár wrote: > > Hi! There is a big inconsistency in Linux tools which read or write > > FAT32 label in filesystem images. The most common used are tools: > > blkid (from util-linux project), fatlabel (previously known as > > dosfslabel; from dosfstools project) and mlabel (from mtools project). > > > > FAT32 is itself a big mess from Microsoft hell and even FAT32 > > implementation in Microsoft Windows systems is not compliant to the > > released FAT32 documentation from Microsoft. > > > > In past months I observed that Linux FAT32 tools has its own way how > > they interpret FAT32 label (known as volume id) and because every GUI > > application uses one of those low-level command line tool, it is a big > > mess if one application say that FAT32 label is A and another that it is > > B. And then Windows XP say, it is C. > > > > I would like to open discussion if it would be possible to change > > behavior how blkid (from util-linux project) and fatlabel (from > > dosfstool project) handle FAT32 label. Ideally to report exactly same > > output. > > > > Basic information about FAT32 label: > > > > 1) It is stored in two locations: boot sector and root directory as > > file name. > > > > 2) In both location format is 11 bytes, padded with spaces (not nulls). > > > > 3) Empty label in boot sector is stored as "NO NAME " and not as > > empty string. > > > > 4) Empty label in root directory is stored either as name which starts > > with byte 0xE5, or is not stored in root directory at all. > > > > 5) If label contains leading byte 0xE5, then in root directory is stored > > as byte 0x05. > > > > 6) Label string is stored according to current DOS code page. Therefore > > label string needs to be converted to bytes. > > > > 7) Label string cannot contain control characters and characters from > > the set ? / \ | . , ; : + = [ ] < > " plus lower case characters > > are stored as their upper case variant (not only ASCII). > > > > (Please correct me if I'm wrong in some of those points) > > > > Plus Microsoft Windows systems fully ignores label stored in boot > > sector. Seems they do not read it nor they do not update it on changes. > > > > Looks like that mlabel (from mtools) applies all above rules and uses > > DOS code page 850 by default (can be changed in config file). > > > > blkid and fatlabel process special cases from 1) to 5) differently and > > they operates on raw bytes, not strings (in DOS code page). > > > > mlabel reads label from the root directory (missing entry is interpreted > > as no label; there is no fallback to boot sector), but "set" operation > > modify label in both location boot sector + root directory. Basically it > > is near to Windows implementation. And reason why Gparted GUI > > application uses mlabel and not fatlabel. > > > > As Linux does not have "current DOS code page" and argv arguments are > > not (Unicode) strings, but arbitrary bytes, I understand that for point > > 6) it is easier to operates not on FAT strings (in current code page), > > but rather on bytes. Which also would be same on all machines with any > > configuration. > > > > But would it be possible to decide and unify handling of point 2), 3), > > 4), 5)? Ideally with combination how to handle situation when different > > label is stored in boot sector and root directory. > > > > As Windows does not use label in boot sector, it is very common > > situation that label in boot sector differs from the root directory. > > > > The best would be see in all cases same label from blkid, fatlabel and > > mlabel. Ideally same as Windows machines -- but due to DOS code page, > > this is possible only for ASCII subset of the 8bit encoding. IIRC most > > (or all?) DOS code page has same characters in printable ASCII range. > > > > It is really bad situation if I open disk in Gparted which show me label > > via mlabel and then I open in KDE Partition Manager and I see different > > label string (as it reads it from fatlabel). > > > > Also note that older version of fatlabel (when it was named dosfslabel) > > operated only the label stored in boot sector (and label stored in root > > directory was not read or touched). > > > > Hi! I did some testing of FAT32 label with different tools and here are > results: Hi! I did more tests with MS-DOS and Windows systems and I'm extending result tables below: > dosfslabel 3.0.12 fatlabel 4.1 blkid 2.20.1 mlabel 4.0.12 label.exe Windows XP > fat32_mkdosfs_label1 'label1 ' 'label1 ' 'label1' 'label1 ' 'label1' > fat32_mkdosfs_label1_dosfslabel_empty ' ' ' ' none ' ' none > fat32_mkdosfs_label1_dosfslabel_label2 'label2 ' 'label2 ' 'label2' 'label2 ' 'label2' > fat32_mkdosfs_label1_dosfslabel_NO_NAME 'NO NAME ' 'NO NAME ' none 'NO NAME ' 'NO NAME' > fat32_mkdosfs_label1_mlabel_erase 'NO NAME ' 'NO NAME ' none none none > fat32_mkdosfs_label1_mlabel_NO_NAME 'NO NAME ' 'NO NAME ' none 'NO NAME ' 'NO NAME' > fat32_mkdosfs_label1_xp_erase 'label1' ' 0xE5'abel1 ' 'label1' none none > fat32_mkdosfs_label1_xp_label2 'label1' ' 'LABEL2 ' 'LABEL2' 'LABEL2 ' 'LABEL2' > fat32_mkdosfs_none ' ' ' ' none none none > fat32_mkdosfs_none_dosfslabel_label1 'label1 ' 'label1 ' 'label1' none none > fat32_mkdosfs_none_dosfslabel_label1_xp_label2 'label1' ' 'LABEL2 ' 'LABEL2' 'LABEL2 ' 'LABEL2' > fat32_mkdosfs_none_dosfslabel_NO_NAME 'NO NAME ' 'NO NAME ' none none none > fat32_mkdosfs_none_xp_label1 ' ' 'LABEL1 ' 'LABEL1' 'LABEL1 ' 'LABEL1' > fat32_mkdosfs_none_xp_label1_dosfslabel_label2 'label2 ' 'label2 ' 'label2' 'label2 ' 'label2' > fat32_xp_label1 'NO NAME ' 'LABEL1 ' 'LABEL1' 'LABEL1 ' 'LABEL1' > fat32_xp_none 'NO NAME ' 'NO NAME ' none none none > fat32_xp_none_dosfslabel_label1 'label1 ' 'label1 ' 'label1' none none > fat32_xp_none_mlabel_label1 'LABEL1 ' 'LABEL1 ' 'LABEL1' 'LABEL1 ' 'LABEL1' label.exe MS-DOS 7.10 label.exe Windows 98 label.exe Windows 10 fat32_mkdosfs_label1 'label1' 'label1' 'label1' fat32_mkdosfs_label1_dosfslabel_empty '' '' none fat32_mkdosfs_label1_dosfslabel_label2 'label2' 'label2' 'label2' fat32_mkdosfs_label1_dosfslabel_NO_NAME 'NO NAME' 'NO NAME' 'NO NAME' fat32_mkdosfs_label1_mlabel_erase none none none fat32_mkdosfs_label1_mlabel_NO_NAME 'NO NAME' 'NO NAME' 'NO NAME' fat32_mkdosfs_label1_xp_erase none none none fat32_mkdosfs_label1_xp_label2 'LABEL2' 'LABEL2' 'LABEL2' fat32_mkdosfs_none none none none fat32_mkdosfs_none_dosfslabel_label1 none none none fat32_mkdosfs_none_dosfslabel_label1_xp_label2 'LABEL2' 'LABEL2' 'LABEL2' fat32_mkdosfs_none_dosfslabel_NO_NAME none none none fat32_mkdosfs_none_xp_label1 'LABEL1' 'LABEL1' 'LABEL1' fat32_mkdosfs_none_xp_label1_dosfslabel_label2 'label2' 'label2' 'label2' fat32_xp_label1 'LABEL1' 'LABEL1' 'LABEL1' fat32_xp_none none none none fat32_xp_none_dosfslabel_label1 none none none fat32_xp_none_mlabel_label1 'LABEL1' 'LABEL1' 'LABEL1' Seems that behavior of reading label from FAT32 volume is consistent between MS-DOS and different Windows versions. The only exception is when in label in the root directory is stored as empty string (11 spaces). MS-DOS and Windows 98 treat it as label with empty string, but Windows XP and Windows 10 as disk without label. > In the first column is image name (all images are compressed and > attached) which contains steps of operations, e.g. file name > fat32_mkdosfs_none_dosfslabel_label1_xp_label2 means: > > 1. create filesystem with mkdosfs without specifying label > 2. change label with dosfslabel (3.0.12) to 'label1' > 3. change label under Windows XP to 'label2' > > From testing it looks like that different tools and different version of > them have different behavior how they read or write FAT32 label, see > following table: > > read boot write boot read root write root > dosfslabel 3.0.0 - 3.0.6 YES YES NO NO > dosfslabel 3.0.7 - 3.0.15 YES YES NO BUGGY (YES - if already exists; NO - otherwise) > dosfslabel 3.0.16 - 4.1 YES YES YES YES > label.exe Windows XP NO NO YES YES > blkid YES NO YES NO > mlabel NO YES YES YES label.exe MS-DOS 6.22 NO YES YES YES label.exe MS-DOS 7.10 NO YES YES YES label.exe Windows 98 SE NO YES YES YES label.exe Windows 10 NO NO YES YES Older MS-DOS 6.22 does not support FAT32 disks, only FAT16. MS-DOS 7.10 has support for FAT32 and also for LFN. But both tested MS-DOS versions and Windows 98 updates label in both locations: boot sector and root directory. Also in case when label is changed in Windows 98 via "My Computer" GUI. >>From above tests it can be seen that both MS-DOS and all Windows versions ignores label which is stored in boot sector and show to user only label from root directory. Also it can be seen that both MS-DOS versions do not have problems when label contains lower case letters. > Attached images in compressed form has only 600 kB and I think they can > be useful for testing either blkid or dosfstools project, so I'm sending > them here. -- Pali Rohár pali.rohar@gmail.com