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Date:   Fri, 16 Jul 2021 17:41:01 +0200
From:   Greg KH <greg@kroah.com>
To:     Pintu Agarwal <pintu.ping@gmail.com>
Cc:     open list <linux-kernel@vger.kernel.org>,
        linux-mtd <linux-mtd@lists.infradead.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Phillip Lougher <phillip@squashfs.org.uk>,
        Sean Nyekjaer <sean@geanix.com>,
        Kernelnewbies <kernelnewbies@kernelnewbies.org>,
        Richard Weinberger <richard@nod.at>
Subject: Re: MTD: How to get actual image size from MTD partition
Message-ID: <YPGojf7hX//Wn5su@kroah.com>
References: <CAOuPNLjzyG_2wGDYmwgeoQuuQ7cykJ11THf8jMrOFXZ7vXheJQ@mail.gmail.com>
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On Fri, Jul 16, 2021 at 12:12:41PM +0530, Pintu Agarwal wrote:
> Hi,
> 
> Our ARM32 Linux embedded system consists of these:
> * Linux Kernel: 4.14
> * Processor: Qualcomm Arm32 Cortex-A7
> * Storage: NAND 512MB
> * Platform: Simple busybox
> * Filesystem: UBIFS, Squashfs
> * Consists of nand raw partitions, squashfs ubi volumes.
> 
> My requirement:
> To find the checksum of a real image in runtime which is flashed in an
> MTD partition.

Try using the dm-verity module for ensuring that a block device really
is properly signed before mounting it.  That's what it was designed for
and is independent of the block device type.

good luck!

greg k-h