linux-kernel - Re: Kernel 4.14: Using dm-verity with squashfs rootfs

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Message-ID: <20210830211224.76391708@windsurf>
Date:   Mon, 30 Aug 2021 21:12:24 +0200
From:   Thomas Petazzoni <thomas.petazzoni@...tlin.com>
To:     Pintu Agarwal <pintu.ping@...il.com>
Cc:     Mikulas Patocka <mpatocka@...hat.com>,
        open list <linux-kernel@...r.kernel.org>,
        Phillip Lougher <phillip@...ashfs.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-mtd <linux-mtd@...ts.infradead.org>, dm-devel@...hat.com,
        Kernelnewbies <kernelnewbies@...nelnewbies.org>, agk@...hat.com,
        snitzer@...hat.com, Sami Tolvanen <samitolvanen@...gle.com>
Subject: Re: Kernel 4.14: Using dm-verity with squashfs rootfs - mounting
 issue

Hello,

On Mon, 30 Aug 2021 23:48:40 +0530
Pintu Agarwal <pintu.ping@...il.com> wrote:

> ohh that means we already have a working reference.
> If possible can you share the details, even 4.19 or higher will be
> also a good reference.
> 
> > > Or, another option is to use the new concept from 5.1 kernel that is:
> > > dm-mod.create = ?  
> > How are you doing it today without dm-mod.create ?  
> I think in 4.14 we don't have dm-mod.create right ?

No, but you can backport it easily. Back at
http://lists.infradead.org/pipermail/openwrt-devel/2019-November/025967.html
I provided backports of this feature to OpenWrt, for the 4.14 and 4.19
kernels.

> Here is our kernel command line:
> 
> [    0.000000] Kernel command line: ro rootwait
> console=ttyMSM0,115200,n8 ....  verity="95384 11923
> 16da5e4bbc706e5d90511d2a3dae373b5d878f9aebd522cd614a4faaace6baa3 12026
> " rootfstype=squashfs ubi.mtd=40,0,30 ubi.block=0,0 root=/dev/dm-0
> .... init=/sbin/init root=/dev/dm-0 dm="rootfs none ro,0 95384 verity
> 1 /dev/ubiblock0_0 /dev/mtdblock53 4096 4096 11923 8 sha256
> 16da5e4bbc706e5d90511d2a3dae373b5d878f9aebd522cd614a4faaace6baa3
> aee087a5be3b982978c923f566a94613496b417f2af592639bc80d141e34dfe7 10
> restart_on_corruption ignore_zero_blocks use_fec_from_device
> /dev/mtdblock53 fec_roots 2 fec_blocks 12026 fec_start 12026" ...

I don't see how this can work without the dm-mod.create feature. Are
you sure the verity= and dm= kernel arguments exist?

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com