Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 7 Dec 2022 14:13:49 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Kamal Dasu <kdasu.kdev@gmail.com>
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>
Subject: Re: Invalid pstore_blk use?
Message-ID: <202212071412.1B1BF97@keescook>
References: <e97bc607-a913-dbbd-1965-b60d55d956b8@gmail.com>
 <c5edaa34-6f85-c6a8-84f5-75413dc864ea@gmail.com>
 <202208091600.D19DFF9C7D@keescook>
 <CAC=U0a3F6172JH+xvA0pSb0bewu_0PX9XFKmL32ge+KyTOdaZA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAC=U0a3F6172JH+xvA0pSb0bewu_0PX9XFKmL32ge+KyTOdaZA@mail.gmail.com>
Precedence: bulk

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