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Subject: Re: [RFC v5 2/4] pstore/blk: add sample for pstore_blk
To:     Kees Cook <keescook@chromium.org>
Cc:     Anton Vorontsov <anton@enomsg.org>,
        Colin Cross <ccross@android.com>,
        Tony Luck <tony.luck@intel.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "David S. Miller" <davem@davemloft.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        Arnd Bergmann <arnd@arndb.de>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
References: <1546862462-19640-1-git-send-email-liaoweixiong@allwinnertech.com>
 <1546862462-19640-3-git-send-email-liaoweixiong@allwinnertech.com>
 <CAGXu5j+4QdqSYokE-0Y_pm5RgBp6i+xMgeXjTnNGVVMKeUafYg@mail.gmail.com>
From:   liaoweixiong <liaoweixiong@allwinnertech.com>
Message-ID: <853df536-a86d-de14-47f4-244f60d9eceb@allwinnertech.com>
Date:   Sat, 19 Jan 2019 17:20:19 +0800
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On 2019-01-18 08:15, Kees Cook wrote:
> On Mon, Jan 7, 2019 at 4:01 AM liaoweixiong
> <liaoweixiong@allwinnertech.com> wrote:
>>
>> It is a sample for pstore_blk, using general ram rather than block device.
>> According to pstore_blk, the data will be saved to ram buffer if not
>> register device path and apis for panic. So, it can only used to dump
>> Oops and some things will not reboot.
> 
> I'm not sure I see the purpose of this implementation? Doesn't this
> just cause all the pstore machinery to skip any actions?

It just a sample for pstore_blk, which can used to record OOPS log on
ram buffer. This module make it easier for device, without panic apis,
to record oops log only.

> i.e. without bzinfo->part_path, won't blkz_sample_write() just return
-EINVAL, etc?

Sure, blkz_sample_write (named blkz_default_general_write now) just
return -EINVAL without bzinfo->part_path. How is the write path? It is
blkoops_pstore_write->blkz_dmesg_write->blkz_zone_write->blkz_default_general_write.
The blkz_zone_write will save the log to ram buffer even
blkz_default_general_write return failure.

>>
>> Signed-off-by: liaoweixiong <liaoweixiong@allwinnertech.com>
>> ---
>>  fs/pstore/Kconfig  |  9 +++++++++
>>  fs/pstore/Makefile |  2 ++
>>  fs/pstore/blkbuf.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 57 insertions(+)
>>  create mode 100644 fs/pstore/blkbuf.c
>>
>> diff --git a/fs/pstore/Kconfig b/fs/pstore/Kconfig
>> index a881c53..18b1fe6 100644
>> --- a/fs/pstore/Kconfig
>> +++ b/fs/pstore/Kconfig
>> @@ -159,3 +159,12 @@ config PSTORE_BLK
>>         help
>>           This enables panic and oops message to be logged to a block dev
>>           where it can be read back at some later point.
>> +
>> +config PSTORE_BLKBUF
>> +       tristate "pstore block buffer sample"
>> +       depends on PSTORE_BLK
>> +       help
>> +         This is a sample for pstore block, but do NOT have a block dev.
>> +         According to pstore_blk, the data will be saved to ram buffer and
>> +         dropped when reboot. So, it can only used to dump Oops and some
>> +         things will not reboot.
>> diff --git a/fs/pstore/Makefile b/fs/pstore/Makefile
>> index c431700..4a6cde1 100644
>> --- a/fs/pstore/Makefile
>> +++ b/fs/pstore/Makefile
>> @@ -15,3 +15,5 @@ obj-$(CONFIG_PSTORE_RAM)      += ramoops.o
>>
>>  obj-$(CONFIG_PSTORE_BLK)       += pstore_blk.o
>>  pstore_blk-y += blkzone.o
>> +
>> +obj-$(CONFIG_PSTORE_BLKBUF)    += blkbuf.o
>> diff --git a/fs/pstore/blkbuf.c b/fs/pstore/blkbuf.c
>> new file mode 100644
>> index 0000000..f1c6f57
>> --- /dev/null
>> +++ b/fs/pstore/blkbuf.c
>> @@ -0,0 +1,46 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + *
>> + * blkbuf.c: Block device Oops/Panic logger
>> + *
>> + * Copyright (C) 2019 liaoweixiong <liaoweixiong@gallwinnertech.com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + *
>> + */
>> +#define pr_fmt(fmt) "blkbuf: " fmt
>> +
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/pstore_blk.h>
>> +
>> +struct blkz_info blkbuf_info = {
>> +       .owner = THIS_MODULE,
>> +       .name = "blkbuf",
>> +       .part_size = 512 * 1024,
>> +       .dmesg_size = 64 * 1024,
>> +       .dump_oops = true,
>> +};
>> +
>> +static int __init blkbuf_init(void)
>> +{
>> +       return blkz_register(&blkbuf_info);
>> +}
>> +module_init(blkbuf_init);
>> +
>> +static void __exit blkbuf_exit(void)
>> +{
>> +       blkz_unregister(&blkbuf_info);
>> +}
>> +module_exit(blkbuf_exit);
>> +
>> +MODULE_LICENSE("GPL");
>> +MODULE_AUTHOR("liaoweixiong <liaoweixiong@allwinnertech.com>");
>> +MODULE_DESCRIPTION("Sample for Pstore BLK with Oops logger");
>> --
>> 1.9.1
>>
> 
>