linux-kernel - Re: [PATCH v2] ramoops: use pstore interface

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Date:	Sat, 03 Dec 2011 09:47:36 +0100
From:	Marco Stornelli <marco.stornelli@...il.com>
To:	Kees Cook <keescook@...omium.org>
CC:	Chen Gong <gong.chen@...ux.intel.com>,
	linux-kernel@...r.kernel.org, Tony Luck <tony.luck@...il.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <greg@...ah.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2] ramoops: use pstore interface

Il 02/12/2011 20:19, Kees Cook ha scritto:
> On Fri, Dec 2, 2011 at 12:20 AM, Marco Stornelli
> <marco.stornelli@...il.com>  wrote:
>> Il 02/12/2011 03:40, Chen Gong ha scritto:
>>
>>> 于 2011/12/1 18:31, Marco Stornelli 写道:
>>>>
>>>> Il 29/11/2011 18:24, Kees Cook ha scritto:
>>>>>
>>>>> On Mon, Nov 28, 2011 at 8:50 PM, Chen Gong<gong.chen@...ux.intel.com>
>>>>> wrote:
>>>>>>
>>>>>> 于 2011/11/29 4:09, Kees Cook 写道:
>>>>>>>
>>>>>>>
>>>>>>> Instead of using /dev/mem directly, use the common pstore
>>>>>>> infrastructure
>>>>>>> to handle Oops gathering and extraction.
>>>>>>>
>>>>>>> Signed-off-by: Kees Cook<keescook@...omium.org>
>>>>>>> ---
>>>>>>> This depends on the pstore changes waiting for -next in:
>>>>>>>
>>>>>>>
>>>>>>> http://git.kernel.org/?p=linux/kernel/git/aegl/linux.git;a=shortlog;h=refs/heads/next
>>>>>>>
>>>>>>>
>>>>>>> ---
>>>>>>> Documentation/ramoops.txt | 8 +-
>>>>>>> drivers/char/Kconfig | 1 +
>>>>>>> drivers/char/ramoops.c | 206
>>>>>>> ++++++++++++++++++++++++++++++++++-----------
>>>>>>> 3 files changed, 160 insertions(+), 55 deletions(-)
>>>>>>>
>>>>>>> diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt
>>>>>>> index 8fb1ba7..a0b9d8e 100644
>>>>>>> --- a/Documentation/ramoops.txt
>>>>>>> +++ b/Documentation/ramoops.txt
>>>>>>> @@ -3,7 +3,7 @@ Ramoops oops/panic logger
>>>>>>>
>>>>>>> Sergiu Iordache<sergiu@...omium.org>
>>>>>>>
>>>>>>> -Updated: 8 August 2011
>>>>>>> +Updated: 17 November 2011
>>>>>>>
>>>>>>> 0. Introduction
>>>>>>>
>>>>>>> @@ -71,6 +71,6 @@ timestamp and a new line. The dump then continues
>>>>>>> with
>>>>>>> the actual data.
>>>>>>>
>>>>>>> 4. Reading the data
>>>>>>>
>>>>>>> -The dump data can be read from memory (through /dev/mem or other
>>>>>>> means).
>>>>>>> -Getting the module parameters, which are needed in order to parse the
>>>>>>> data, can
>>>>>>> -be done through /sys/module/ramoops/parameters/* .
>>>>>>> +The dump data can be read from the pstore filesystem. The format for
>>>>>>> these
>>>>>>> +files is "dmesg-ramoops-N", where N is the record number in
>>>>>>> memory. To
>>>>>>> delete
>>>>>>> +a stored record from RAM, simply unlink the respective pstore file.
>>>>>>
>>>>>>
>>>>>> I think the definition of "mem_address" in the doc is not very
>>>>>> clear. It is
>>>>>> not a normal memory instead of a persistent RAM. I suggest adding more
>>>>>> descriptions.
>>>>>> It's better if there is a real example.
>>>>>
>>>>> Okay. I'm not sure it's in the scope of this patch, but I can try.
>>>>>
>>>>> Marco, do you have suggestions for how this could be enhanced?
>>>>
>>>> I don't know actually. It's not mandatory use a persistent memory. A
>>>> simple
>>>> piece of reserved RAM is ok. Obviously it will work only over reboot
>>>> and not
>>>> over power down. I define mem_address as a generic piece of reserved
>>>> memory.
>>>
>>> Anyway, we need a pratical exmaple to instruct us how to use this diver.
>>
>> For example we can use the mem parameter to reserve memory and use it as
>> ramoops buffer, very simple.
> 
> I tried both "mem" and "memmap":
> 
> mem=0x3f000000 ramoops.mem_address=0x3f000000 ramoops.mem_size=0x40000
> ramoops.record_size=0x10000
> 
> memmap=256K$0x3f000000 ramoops.mem_address=0x3f000000
> ramoops.mem_size=0x40000 ramoops.record_size=0x10000
> 
> Neither works for me (I end up triggering a panic via BUG in kfree). I
> wonder if it's some bad interaction between the cmdline and the memory
> tables? When I boot with mem=0x3f000000 and without ramoops, I see in
> /proc/iomem:
> 
> 00100000-3effffff : System RAM
>    01000000-0137c35f : Kernel code
>    0137c360-0151e85f : Kernel data
>    01591000-01627fff : Kernel bss
> 3f000000-3fffcfff : RAM buffer
> 
> It seems like the system isn't ignoring the region? What's the right
> way to do this?
> 
> -Kees
> 

I don't know, however in that situation it's normal to have a crash, if
you use the RAM buffer region, you should see "reserved" in iomem. It
can be an other kind of problem.

Marco
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