linux-kernel - Re: [PATCH v6 01/24] erofs: add on-disk layout

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20190903112707.GA3844@amd>
Date:   Tue, 3 Sep 2019 13:27:07 +0200
From:   Pavel Machek <pavel@...x.de>
To:     dsterba@...e.cz, Pavel Machek <pavel@...x.de>,
        Joe Perches <joe@...ches.com>,
        Gao Xiang <gaoxiang25@...wei.com>,
        Christoph Hellwig <hch@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Theodore Ts'o <tytso@....edu>,
        Amir Goldstein <amir73il@...il.com>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Dave Chinner <david@...morbit.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>, Jan Kara <jack@...e.cz>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, devel@...verdev.osuosl.org,
        LKML <linux-kernel@...r.kernel.org>,
        linux-erofs@...ts.ozlabs.org, Chao Yu <yuchao0@...wei.com>,
        Miao Xie <miaoxie@...wei.com>,
        Li Guifu <bluce.liguifu@...wei.com>,
        Fang Wei <fangwei1@...wei.com>
Subject: Re: [PATCH v6 01/24] erofs: add on-disk layout

Hi!

> > No. gdb tells you what the actual offsets _are_.
> 
> Ok, reading your reply twice, I think we have different perspectives. I
> don't trust the comments.
> 
> The tool I had in mind is pahole that parses dwarf information about the
> structures, the same as gdb does. The actual value of the struct members
> is the thing that needs to be investigated in memory dumps or disk image
> dumps.
> 
> > > > The expected offset is somewhat valuable, but
> > > > perhaps the form is a bit off given the visual
> > > > run-in to the field types.
> > > > 
> > > > The extra work with this form is manipulating all
> > > > the offsets whenever a structure change occurs.
> > > 
> > > ... while this is error prone.
> > 
> > While the comment tells you what they _should be_.
> 
> That's exactly the source of confusion and bugs. For me an acceptable
> way of asserting that a value has certain offset is a build check, eg.
> like
> 
> BUILD_BUG_ON(strct my_superblock, magic, 16);

Yes, that would work, too. As would documentation file with the disk
structures.

Best regards,
								Pavel
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

Download attachment "signature.asc" of type "application/pgp-signature" (182 bytes)