Re: [oss-security] [patch] proc.5: tell how to parse /proc/*/stat correctly

Alejandro Colomar
2022-12-28T19:57:29Z

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Hi all,

On 12/28/22 20:24, Shawn Webb wrote:
> On Wed, Dec 28, 2022 at 01:02:35PM -0500, Demi Marie Obenour wrote:
>> On Wed, Dec 28, 2022 at 12:25:17PM -0500, Shawn Webb wrote:
>>> On Wed, Dec 28, 2022 at 11:47:25AM -0500, Demi Marie Obenour wrote:
>>>> On Wed, Dec 28, 2022 at 10:24:58AM -0500, Shawn Webb wrote:
>>>>> On Tue, Dec 27, 2022 at 04:44:49PM -0800, Lyndon Nerenberg (VE7TFX/VE6BBM) wrote:
>>>>>> Dominique Martinet writes:
>>>>>>
>>>>>>> But, really, I just don't see how this can practically be said to be parsable...
>>>>>>
>>>>>> In its current form it never will be. The solution is to place
>>>>>> this variable-length field last. Then you can "cut -d ' ' -f 51-"
>>>>>> to get the command+args part (assuming I counted all those fields
>>>>>> correctly ...)
>>>>>>
>>>>>> Of course, this breaks backwards compatability.
>>>>>
>>>>> It would also break forwards compatibility in the case new fields
>>>>> needed to be added.
>>>>>
>>>>> The only solution would be a libxo-style feature wherein a
>>>>> machine-parseable format is exposed by virtue of a file extension.
>>>>>
>>>>> Examples:
>>>>>
>>>>> 1. /proc/pid/stats.json
>>>>> 2. /proc/pid/stats.xml
>>>>> 3. /proc/pid/stats.yaml_shouldnt_be_a_thing
>>>>
>>>> A binary format would be even better. No risk of ambiguity.
>>>
>>> I think the argument I'm trying to make is to be flexible in
>>> implementation, allowing for future needs and wants--that is "future
>>> proofing".
>>
>> Linux should not have an XML, JSON, or YAML serializer. Linux already
>> does way too much; let’s not add one more thing to the list.
>
> Somewhat agreed. I think formats like JSON provide a good balance
> between machine parseable and human readable.
> a
> As I described earlier, though, when it comes to concepts like procfs
> and sysfs, I have a bias towards abandoning them in favor of sysctl.
> If sysctl nodes were to be used, no new serialization formats would
> need to be implemented--and developers would also use a safter method
> of system and process inspection and manipulation.
>

Just a comment as someone who is reading without much understanding of the
contents of /prod/pid/stat:

If organization of the data in the file is a problem, and the format starts to
matter, maybe it's a hint that there are too many different contents, and could
be split into different files, each one with its own formatting rules. I'll
suggest that maybe a set of files, maybe contained in a common directory
stats.d, is what you're looking for?

Binary format is not of my preference, since most user-space tools work with the
standard interface, that is, text.

Cheers,

Alex

--
<http://www.alejandro-colomar.es/>

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