linux-kernel - Re: [PATCH] pstore: reset ftrace_read_cnt at ramoops_pstore

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Date:	Fri, 7 Mar 2014 16:23:29 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Liu ShuoX <shuox.liu@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Tony Luck <tony.luck@...el.com>,
	Colin Cross <ccross@...roid.com>,
	Anton Vorontsov <anton@...msg.org>,
	yanmin_zhang@...ux.intel.com
Subject: Re: [PATCH] pstore: reset ftrace_read_cnt at ramoops_pstore_open

On Fri, Mar 7, 2014 at 1:25 PM, Andrew Morton <akpm@...ux-foundation.org> wrote:
> On Fri, 7 Mar 2014 10:58:43 +0800 Liu ShuoX <shuox.liu@...el.com> wrote:
>
>>
>> ftrace_read_cnt need to be reset in open to support mutli times
>> getting the records.
>>
>> Signed-off-by: Liu ShuoX <shuox.liu@...el.com>
>> ---
>>   fs/pstore/ram.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
>> index fa8cef2..9fe5b13 100644
>> --- a/fs/pstore/ram.c
>> +++ b/fs/pstore/ram.c
>> @@ -86,6 +86,7 @@ struct ramoops_context {
>>       struct persistent_ram_ecc_info ecc_info;
>>       unsigned int max_dump_cnt;
>>       unsigned int dump_write_cnt;
>> +     /* _read_cnt need clear on ramoops_pstore_open */
>>       unsigned int dump_read_cnt;
>>       unsigned int console_read_cnt;
>>       unsigned int ftrace_read_cnt;
>> @@ -101,6 +102,7 @@ static int ramoops_pstore_open(struct pstore_info *psi)
>>
>>       cxt->dump_read_cnt = 0;
>>       cxt->console_read_cnt = 0;
>> +     cxt->ftrace_read_cnt = 0;
>>       return 0;
>>   }
>>
>> @@ -428,7 +430,6 @@ static int ramoops_probe(struct platform_device *pdev)
>>       if (pdata->ftrace_size && !is_power_of_2(pdata->ftrace_size))
>>               pdata->ftrace_size = rounddown_pow_of_two(pdata->ftrace_size);
>>
>> -     cxt->dump_read_cnt = 0;
>>       cxt->size = pdata->mem_size;
>>       cxt->phys_addr = pdata->mem_address;
>>       cxt->record_size = pdata->record_size;
>
> The dump_read_cnt changes appear to be unrelated to the actual bugfix?

I recommended this change since it is being cleared during open, and
this zeroing was confusing.

> If so, please send this along as a separate patch.  With a full
> changelog - this one doesn't explain the dump_read_cnt changes at all.

Liu, I would recommend a changelog along the lines of:

Clarify which variables need to be cleared during pstore_open. Added
missed ftrace_read_cnt clearing and removed duplicate clearing in
ramoops_probe.

-Kees


-- 
Kees Cook
Chrome OS Security
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