Re: [Cocci] Whitelist function in rule

[Paul Chaignon <paul@cilium.io>]

On Tue, Jun 02, 2020 at 12:19:50PM +0200, Julia Lawall wrote:
> 
> 
> On Tue, 2 Jun 2020, Paul Chaignon wrote:
> 
> > Hi all,
> >
> > I'm trying to find calls to ep_tail_call() that are *not* followed by
> > 'return DROP_MISSED_TAIL_CALL'. That works fine (rule1 below), but I then
> > want to whitelist one specific function, send_drop_notify().
> >
> > I couldn't find a way to do that from the first rule, so I whitelisted
> > send_drop_notify() with a second rule (rule2 below). That seems rather
> > cumbersome and I'm wondering if there's maybe a simpler approach?
> >
> >   @rule1@
> >   position p1;
> 
> In coccinelle/tests/python_poscon.cocci you have an example of how to
> attach python code to a metavariable:
> 
> @initialize:python@
> @@
> 
> def past_line_4(p, other):
>     return int(p[0].line) > 4
> 
> @r@
> expression e;
> @@
> 
> f(e)
> 
> @@
> position p : script:python(r.e) { past_line_4(p, e) };
> expression r.e;
> @@
> 
> g(
> -e@p
> +27
>  )
> 
> In your case, I think that in the python code you should be able to access
> p1[0].current_element.  You can check that that is different than the
> name of the function that you want to ignore.  There are some limitations
> on what can be put in the {} in such a metavariable declaration, so if you
> have problems you can make a function, as shown in the example.  That code
> should return true if you want the match to take place and false
> otherwise.

Thanks! That worked great!
And the Python filtering looks super useful; I'm likely going to be
using that a lot :-)

Paul

> 
> julia
> 
> 
> 
> >   @@
> >
> >   (
> >     ep_tail_call(...);
> >     ... when forall
> >     return DROP_MISSED_TAIL_CALL;
> >   |
> >     ep_tail_call@p1(...);
> >   )
> >
> >   @rule2@
> >   position p2, rule1.p1;
> >   identifier fn != send_drop_notify;
> >   @@
> >
> >   fn(...) {
> >   <+...
> >   ep_tail_call@p1@p2(...);
> >   ...+>
> >   }
> >
> > When I tried using rule1 as the body of the function in rule2, it just
> > didn't match anything anymore.
> >
> > Thanks,
> > Paul
> > _______________________________________________
> > Cocci mailing list
> > Cocci@systeme.lip6.fr
> > https://systeme.lip6.fr/mailman/listinfo/cocci
> >
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