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Re: [PATCH v4 0/3] initramfs: add support for xattrs in the initial ram

From: Jim Baxter
Subject: Re: [PATCH v4 0/3] initramfs: add support for xattrs in the initial ram disk
Date: Mon, 18 Jul 2022 19:08:04 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0

Best regards,

*Jim Baxter*

Siemens Digital Industries Software
Automotive Business Unit
Tel.: +44 (161) 926-1656
mailto:jim.baxter@siemens.com <mailto:jim.baxter@siemens.com>
sw.siemens.com <https://sw.siemens.com/>

On 18/07/2022 17:49, Roberto Sassu wrote:
>> From: Jim Baxter [mailto:jim_baxter@mentor.com]
>> Sent: Monday, July 18, 2022 6:36 PM
>> Hello,
>> I have been testing these patches and do not see the xattr information when
>> trying to retrieve it within the initramfs, do you have an example of how
>> you tested this originally?
> Hi Jim, all
> apologies, I didn't find yet the time to look at this.

Hello Roberto,

Thank you for your response, I can wait until you have looked at the patches,
I asked the question to make sure it was not something wrong in my

> Uhm, I guess this could be solved with:
> https://github.com/openeuler-mirror/kernel/commit/18a502f7e3b1de7b9ba0c70896ce08ee13d052da
> and adding initramtmpfs to the kernel command line. You are
> probably using ramfs, which does not have xattr support.

Thank you, I have tested that patch but the problem remained. Here is my
command line, I wonder if there is something wrong.

Kernel command line: rw rootfstype=initramtmpfs root=/dev/ram0 
initrd=0x500000000 rootwait 

I also found that root is always mounted as rootfs in my initramfs system
which I understood to be tmpfs, is that incorrect?

sh-3.2# mount
none on / type rootfs (rw)

>> So far I have set the xattr in the rootfs before creating the cpio file like 
>> this:
>> $ setfattr -n user.comment -v "this is a comment" test.txt
>> If I access the data here it works:
>> $ getfattr test.txt
>> # file: test.txt
>> user.comment
>> Then I package it and try to verify it with this command:
>> $getfattr /test.txt
> I assume you try to pack/unpack, right? If I remember correctly
> I only implemented the pack part. Unpacking is done by the kernel
> (but you are right, it should be done by user space too).

I modified the file before packing. To pack I use the following commands:

$ ./usr/gen_initramfs.sh -l initramfs.list -e xattr ../rootfs > initramfs.cpio
$ gzip initramfs.cpio
$ mkimage -A arm64 -O linux -T ramdisk -d initramfs.cpio.gz uRamdisk

The kernel is loaded using:
booti ${kernaddr} ${initramaddr} ${dtbaddr}

>> Which returns to the command line without the data.
>> I believe the cpio is working because I see the file /METADATA\!\!\! in
>> the target root filesystem, which shows the following when viewed with cat 
>> -e:
>> 00000028^A^Auser.comment^@this is a comment
>> This matches the data I fed in at the start, so I believe the data is being
>> transferred correctly but I am accessioning it with the wrong tools.
> Yes, xattrs are marshalled in the METADATA!!! file, one per regular file
> xattrs are applied to. Xattrs are applied to the previous regular file.
> That file name was preferred to adding a suffix to the file, to avoid
> reaching the filename size limit.
> Roberto

Best regards,

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