linux-kernel - Re: [RFC v5 2/4] pstore/blk: add sample for pstore

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Date:   Thu, 17 Jan 2019 16:15:46 -0800
From:   Kees Cook <keescook@...omium.org>
To:     liaoweixiong <liaoweixiong@...winnertech.com>
Cc:     Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        Jonathan Corbet <corbet@....net>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Arnd Bergmann <arnd@...db.de>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v5 2/4] pstore/blk: add sample for pstore_blk

On Mon, Jan 7, 2019 at 4:01 AM liaoweixiong
<liaoweixiong@...winnertech.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? i.e. without
bzinfo->part_path, won't blkz_sample_write() just return -EINVAL, etc?

>
> Signed-off-by: liaoweixiong <liaoweixiong@...winnertech.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@...lwinnertech.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@...winnertech.com>");
> +MODULE_DESCRIPTION("Sample for Pstore BLK with Oops logger");
> --
> 1.9.1
>


-- 
Kees Cook