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From:   Kamal Dasu <kdasu.kdev@gmail.com>
Date:   Fri, 9 Dec 2022 16:19:56 -0500
Message-ID: <CAC=U0a20oYLjh_m3N2oUpEGhVZTyARKn_rTgwscTG0HdCZU_Tg@mail.gmail.com>
Subject: Re: Invalid pstore_blk use?
To:     Kees Cook <keescook@chromium.org>
Cc:     Florian Fainelli <f.fainelli@gmail.com>,
        WeiXiong Liao <gmpy.liaowx@gmail.com>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Anton Vorontsov <anton@enomsg.org>,
        Colin Cross <ccross@android.com>,
        Tony Luck <tony.luck@intel.com>
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Kees,

Thanks for your reply. I will send the RFC patch.

Kamal

On Wed, Dec 7, 2022 at 5:13 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Fri, Nov 18, 2022 at 03:41:44PM -0500, Kamal Dasu wrote:
> > Kees,
> >
> > I am in the process of implementing  mmcpstore  backend for mmc  based
> > on the mtdpstore driver
> >
> > This is what is registered with register_pstore_device(&cxt->dev);
> > cxt->dev.flags = PSTORE_FLAGS_DMESG;
> > cxt->dev.zone.read = mmcpstore_read;
> > cxt->dev.zone.write = mmcpstore_write;
> > cxt->dev.zone.erase = mmcpstore_erase;
> > cxt->dev.zone.panic_write = mmcpstore_panic_write;
> >
> > # dmesg | grep pstor
> > [    0.000000] Kernel command line: pstore_blk.blkdev=/dev/mmcblk1p8
> > crash_kexec_post_notifiers printk.always_kmsg_dump
> > [    1.993986] pstore_zone: registered pstore_blk as backend for
> > kmsg(Oops,panic_write) pmsg
> > [    2.002582] pstore: Using crash dump compression: deflate
> > [    2.008133] pstore: Registered pstore_blk as persistent store backend
> > [    2.020907] mmcpstore: /dev/mmcblk1p8 size 131072 start sector
> > 34468 registered as psblk backend
> > [   17.868753] psz_kmsg_recover_meta: pstore_zone: no valid data in
> > kmsg dump zone 0
> > [   18.298933] psz_recover_zone: pstore_zone: no valid data in zone pmsg
> > [   18.305398] psz_recovery: pstore_zone: recover end!
> >
> > The driver is successfully registered and the read path works when
> > /sys/fs/pstor is mounted , however mmc_pstore_panic_write is not
> > called.
> > Need help in understanding what could be missing. I am using the
> > latest upstream kernel for testing.
>
> Hi!
>
> Can you send an RFC patch? I'd expect this to work as you've currently
> described it, but without code I'd just be guessing. :)
>
> -Kees
>
> --
> Kees Cook