Re: [PATCH] coccinelle: api: add kzfree script

Re: [PATCH] coccinelle: api: add kzfree script

[Markus Elfring]

> Check for memset() with 0 followed by kfree().

I suggest to simplify the SmPL code a bit like the following.


> +virtual context
> +virtual org
> +virtual report
> +virtual patch

+virtual context, org, report, patch


…
> +@@
> +
> +(
> +* memset(E, 0, ...);
> +|
> +* memset(E, '\0', ...);
> +)
> +* kfree(E)@p;

+@@
+*memset(E, 0, ...);
+*kfree(E)@p;


How does the SmPL asterisk functionality fit to the operation
modes “org” and “report”?


> +@@
> +
> +(
> +- memset(E, 0, ...);
> +|
> +- memset(E, '\0', ...);
> +)
> +- kfree(E);
> ++ kzfree(E);

+@@
+-memset(E, 0, ...);
+-kfree
++kzfree
+       (E);

I got the impression that the specification of a SmPL disjunction
could be omitted because of the technical detail that the isomorphism
“zero_multiple_format” should handle such an use case already.

Would you like to tolerate any extra source code between these function calls?

Regards,
Markus

Re: [PATCH] coccinelle: api: add kzfree script

[Julia Lawall]

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On Thu, 4 Jun 2020, Markus Elfring wrote:

> > Check for memset() with 0 followed by kfree().
>
> I suggest to simplify the SmPL code a bit like the following.
>
>
> > +virtual context
> > +virtual org
> > +virtual report
> > +virtual patch
>
> +virtual context, org, report, patch

This is pointless.

>
>
> …
> > +@@
> > +
> > +(
> > +* memset(E, 0, ...);
> > +|
> > +* memset(E, '\0', ...);
> > +)
> > +* kfree(E)@p;
>
> +@@
> +*memset(E, 0, ...);
> +*kfree(E)@p;
>
>
> How does the SmPL asterisk functionality fit to the operation
> modes “org” and “report”?

make coccicheck uses the option --no-show-diff for the org and report
modes.

>
> > +@@
> > +
> > +(
> > +- memset(E, 0, ...);
> > +|
> > +- memset(E, '\0', ...);
> > +)
> > +- kfree(E);
> > ++ kzfree(E);
>
> +@@
> +-memset(E, 0, ...);
> +-kfree
> ++kzfree
> +       (E);
>
> I got the impression that the specification of a SmPL disjunction
> could be omitted because of the technical detail that the isomorphism
> “zero_multiple_format” should handle such an use case already.
>
> Would you like to tolerate any extra source code between these function calls?

I already addressed these issues.

julia

Re: coccinelle: api: add kzfree script

[Markus Elfring]

>>> +virtual context
>>> +virtual org
>>> +virtual report
>>> +virtual patch
>>
>> +virtual context, org, report, patch
>
> This is pointless.

I find the proposed SmPL code variant more succinct.


>> How does the SmPL asterisk functionality fit to the operation
>> modes “org” and “report”?
>
> make coccicheck uses the option --no-show-diff for the org and report modes.

Can it be nicer to avoid the usage of specific functionality
in the SmPL script directly?
Should the corresponding SmPL rule dependencies become clearer?

Regards,
Markus

Re: coccinelle: api: add kzfree script

[Markus Elfring]

> Is avoiding transforming the case where E is not verified to be a pointer a concern?

I imagine that answers to this question have got consequences also on
the confidence level for such SmPL scripts.
The desire and requirement to specify data type restrictions (for expressions)
can influence data processing efforts in significant ways.

* If it would be accepted to choose a simpler source code search approach,
  there are corresponding risks to consider.

* If you would like to reduce the general possibility for false positives
  according to advanced software analysis, the amount of data processing
  will increase because information from header files will probably be needed.
  The run time characteristics will become more interesting then.
  Additional program execution parameters will be relevant for this use case.

Regards,
Markus