Re: [PATCH 1/2] ramoops: use pstore interface

[Kees Cook]

On Wed, Nov 16, 2011 at 9:35 PM, Chen Gong <gong.chen@xxxxxxxxxxxxxxx> wrote:
> ä 2011/11/17 5:25, Kees Cook åé:
>> Instead of using /dev/mem directly, use the common pstore infrastructure
>> to handle Oops gathering and extraction.
>> [...]
>> + Â Â Â /* Explicitly only take the first part of any new crash.
>> + Â Â Â Â* If our buffer is larger than kmsg_bytes, this can never happen,
>> + Â Â Â Â* and if our buffer is smaller than kmsg_bytes, we don't want the
>> + Â Â Â Â* report split across multiple records. */
>> + Â Â Â if (part != 1)
>> + Â Â Â Â Â Â Â return -ENOSPC;
>
> why only one part is accepted? You are afraid about your filename style?

The logic in ramoops doesn't expect to have a split-up report. Since
pstore doesn't limit reports to kmsg_bytes in size (it actually splits
reports on pstore_info.bufsize) this is a non-issue, but in the case
that a platform defines very small ramoops record sizes, I didn't want
the extra stuff written to additional records. If ramoops gains real
record headers ever, this can change, of course. In the meantime, it
should be defensive.

>> + Â Â Â /* Only a single ramoops area allowed at a time, so fail extra
>> + Â Â Â Â* probes.
>> + Â Â Â Â*/
>> + Â Â Â if (cxt->max_count)
>> + Â Â Â Â Â Â Â goto fail3;
>
> Should be fail4
> [...]
> In some situations fail4 maybe hits max_count != 0, so here max_count should
> be cleared. I think you should rearrange the logic in this function
> carefully.

Ah, thanks for the catch. All the error targets got messed up. I'll
fix them and name them instead of using numbers.

>> + Â Â Â /* TODO(kees): It shouldn't be possible to remove ramoops since
>> + Â Â Â Â* pstore doesn't support unregistering yet. When it does, remove
>> + Â Â Â Â* this early return and add the unregister where noted below.
>> + Â Â Â Â*/
>> + Â Â Â return -EBUSY;
>
> This style is not reasonable. Maybe it should have a better wrap.

I'm not sure I understand what you mean. It's wrapped roughly to
column 75 already. What would be better for this comment? Or did you
mean I shouldn't have unreachable code?

> BTW, you need to update Documentation/ramoops.txt

Ah! Yes, thanks for the reminder.

-Kees

-- 
Kees Cook
ChromeOS Security
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