Kernel 4.14: Using dm-verity with squashfs rootfs - mounting issue

[Pintu Agarwal]

On Mon, 30 Aug 2021 at 22:25, Thomas Petazzoni
<thomas.petazzoni at bootlin.com> wrote:
>
> Hello,
>
> On Mon, 30 Aug 2021 21:55:19 +0530
> Pintu Agarwal <pintu.ping at gmail.com> wrote:
>
> > Sorry for coming back to this again..
> > Unfortunately, none of the options is working for us with squashfs
> > (bootloader, initramfs).
> > initramfs have different kinds of challenges because of the partition
> > size issue.
> > So, our preferred option is still the bootloader command line approach..
> >
> > Is there a proven and working solution of dm-verity with squashfs ?
> > If yes, please share some references.
> >
> > The current problem with squashfs is that we could not append the
> > verity-metadata to squashfs, so we store it on a separate volume and
> > access it.
>
> Here, it definitely worked to append the hash tree to the squashfs
> image and store them in the same partition.
>
> > By specifying it like : /dev/mtdblock53
> >
> > Then we get the error like this:
> > {
> > [    4.950276] device-mapper: init: attempting early device configuration.
> > [    4.957577] device-mapper: init: adding target '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'
> > [    4.975283] device-mapper: verity: sha256 using implementation
> > "sha256-generic"
> > [    4.998728] device-mapper: init: dm-0 is ready
>
> Could you show the full kernel command line ?
Shared below

> > Do you see any other problem here with dm-verity cmdline or with squashfs ?
> >
> > Is squashfs ever proved to be working with dm-verity on higher kernel version ?
> > Currently our kernel version is 4.14.
>
> I confirm we used squashfs on dm-verity successfully. For sure on 4.19,
> perhaps on older kernels as well.

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 ?

> Again, please give your complete kernel command line.
>
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" ...

Do you see any issue here ?
Can you share your command line for squashfs to compare ?

Thank you,
Pintu