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From: Rob Landley <firstname.lastname@example.org>
To: "H. Peter Anvin" <email@example.com>,
Taras Kondratiuk <firstname.lastname@example.org>,
Al Viro <email@example.com>, Arnd Bergmann <firstname.lastname@example.org>,
Mimi Zohar <email@example.com>,
Jonathan Corbet <firstname.lastname@example.org>,
James McMechan <email@example.com>
Cc: firstname.lastname@example.org, Victor Kamensky <email@example.com>,
Subject: Re: [PATCH v3 01/15] Documentation: add newcx initramfs format description
Date: Fri, 16 Feb 2018 15:25:07 -0600 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
On 02/16/2018 02:59 PM, H. Peter Anvin wrote:
> On 02/16/18 12:33, Taras Kondratiuk wrote:
>> Many of the Linux security/integrity features are dependent on file
>> metadata, stored as extended attributes (xattrs), for making decisions.
>> These features need to be initialized during initcall and enabled as
>> early as possible for complete security coverage.
>> Initramfs (tmpfs) supports xattrs, but newc CPIO archive format does not
>> support including them into the archive.
>> This patch describes "extended" newc format (newcx) that is based on
>> newc and has following changes:
>> - extended attributes support
>> - increased size of filesize to support files >4GB
>> - increased mtime field size to have 64 bits of seconds and added a
>> field for nanoseconds
>> - removed unused checksum field
> If you are going to implement a new, non-backwards-compatible format,
> you shouldn't replicate the mistakes of the current format. Specifically:
So rather than make minimal changes to the existing format and continue to
support the existing format (sharing as much code as possible), you recommend
gratuitous aesthetic changes?
> 1. The use of ASCII-encoded fixed-length numbers is an idiotic legacy
> from an era before there were any portable way of dealing with numbers
> with prespecified endianness.
It lets encoders and decoders easily share code with the existing cpio format,
which we still intend to be able to read and write.
> If you are going to use ASCII, make them
> delimited so that they don't have fixed limits, or just use binary.
When it's gzipped this accomplishes what? (Other than being gratuitously
different from the previous iteration?)
> The cpio header isn't fixed size, so that argument goes away, in fact
> the only way to determine the end of the header is to scan forward.
> 2. Alignment sensitivity! Because there is no header length
> information, the above scan tells you where the header ends, but there
> is padding before the data, and the size of that padding is only defined
> by alignment.
Again, these are minimal changes to the existing cpio format. You're complaining
about _cpio_, and that the new stuff isn't _different_ enough from it.
> 3. Inband encoding of EOF: if you actually have a filename "TRAILER!!!"
> you have problems.
Been there, done that:
> But first, before you define a whole new format for which no tools exist
> (you will have to work with the maintainers of the GNU tools to add
No, he's been working with the maintainer of toybox to add support (for about a
year now), which gets him the Android command line. And the kernel has its own
built-in tool to generate cpio images anyway.
Why would anyone care what the GNU project thinks?
> you should see how complex it would be to support the POSIX
> tar/pax format,
That argument was had (at length) when initramfs went in over a decade ago.
There are links in Documentation/filesystems/ramfs-rootfs-initramfs.txt to the
mailing list entries about it.
> which already has all the features you are seeking, and
> by now is well-supported.
So... tar wasn't well-supported 15 years ago? (Hasn't the kernel source always
been distributed via tarball back since 0.0.1?)
You're suggesting having a whole second codepath that shares no code with the
existing cpio extractor. Are you suggesting abandoning support for the existing
initramfs.cpio.gz file format?
next prev parent reply other threads:[~2018-02-16 21:25 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-16 20:33 [PATCH v3 00/15] extend initramfs archive format to support xattrs Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 01/15] Documentation: add newcx initramfs format description Taras Kondratiuk
2018-02-16 20:59 ` H. Peter Anvin
2018-02-16 21:25 ` Rob Landley [this message]
2018-02-16 21:47 ` Victor Kamensky
2018-02-17 0:00 ` hpa
2018-02-17 10:04 ` Taras Kondratiuk
2018-02-17 17:32 ` Rob Landley
2018-02-18 0:15 ` Mimi Zohar
2018-02-18 0:24 ` hpa
2018-02-18 0:26 ` hpa
2018-02-18 0:47 ` Mimi Zohar
2018-02-16 20:33 ` [PATCH v3 02/15] initramfs: replace states with function pointers Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 03/15] initramfs: store file name in name_buf Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 04/15] initramfs: remove unnecessary symlinks processing shortcut Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 05/15] initramfs: move files creation into separate state Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 06/15] initramfs: separate reading cpio method from header Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 07/15] initramfs: split header layout information from parsing function Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 08/15] initramfs: add newcx format Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 09/15] initramfs: set extended attributes Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 10/15] gen_init_cpio: move header formatting into function Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 11/15] gen_init_cpio: add newcx format Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 12/15] gen_init_cpio: set extended attributes for " Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 12/14] gen_initramfs_list.sh: add -x option to enable " Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 13/15] " Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 13/14] selinux: allow setxattr on rootfs so initramfs code can set them Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 14/15] " Taras Kondratiuk
2018-02-20 19:01 ` Stephen Smalley
2018-03-11 3:07 ` Victor Kamensky
2018-03-20 16:33 ` [Non-DoD Source] " Stephen Smalley
2018-02-16 20:33 ` [PATCH v3 14/14] selinux: delay sid population for rootfs till init is complete Taras Kondratiuk
2018-02-16 20:33 ` [PATCH v3 15/15] " Taras Kondratiuk
2018-02-20 18:56 ` Stephen Smalley
2018-03-07 16:51 ` Rob Landley
2018-03-07 17:26 ` Victor Kamensky
2018-03-11 3:08 ` Victor Kamensky
2018-03-20 16:30 ` [Non-DoD Source] " Stephen Smalley
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