From: julia.lawall@lip6.fr (Julia Lawall)
To: cocci@systeme.lip6.fr
Subject: [Cocci] First coccinelle script, need some help.
Date: Wed, 10 Oct 2018 22:51:28 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1810102249410.2479@hadrien> (raw)
In-Reply-To: <20181010204517.GA109962@joelaf.mtv.corp.google.com>
On Wed, 10 Oct 2018, Joel Fernandes wrote:
> On Wed, Oct 10, 2018 at 10:23:18PM +0200, Julia Lawall wrote:
> >
> >
> > On Wed, 10 Oct 2018, Joel Fernandes wrote:
> >
> > >
> > > Hi!
> > >
> > > I am trying to determine if a function argument is used across the whole
> > > kernel for a certain kernel function.
> > >
> > > I mustered up enough courage to write my first coccinelle script after a few
> > > late nights of reading up about it :)
> > >
> > > Here is .cocci script. I am trying to find if address is used at all in any
> > > possible definitions of pte_alloc():
> > >
> > > $ cat ~/pte_alloc.cocci
> > > virtual report
> > >
> > > @pte_args depends on report@
> > > identifier E1, E2;
> > > type T1, T2;
> > > position p;
> > > @@
> > >
> > > pte_alloc at p(T1 E1, T2 E2)
> > > {
> > > ...
> > > (
> > > ...
> > > E2
> > > ...
> > > )
> > > ...
> > > }
> >
> >
> > In report mode, by default, the pattern has to match on all paths. Also
> > when you have ... before or after E2, there can be no occurrence of E2 in
> > the code matched by the ... So your rule requires that on every possible
> > execution path through the function, there is exactly one occurrence of
> > E2.
> >
> > You can try the following instead:
> >
> > virtual report
> >
> > @pte_args depends on report exists@
> > identifier E1, E2;
> > type T1, T2;
> > position p;
> > @@
> >
> > pte_alloc at p(T1 E1, T2 E2)
> > {
> > ... when any
> > E2
> > ... when any
> > }
>
> Thanks for the quick reply.
> If I just add 'depends on report exists' to the rule, then my original
> example works fine now. I did not need to add the 'when any'. Do you mind
> taking my original simple test.c example and modify it and let me know under
> what situation would it not work?
>
> I even added address = 1 outside of the if block and it works fine, I see the
> warning as I expect without 'when any' in pront of the "...".
>
> struct page *pte_alloc(struct mm_struct *mm, unsigned long address)
> {
> address = 1;
> if (condition()) {
> while (1) {
> address++;
> }
> return NULL;
> }
> }
This works, because there exists a path through the function that has only
one use of address, ie the path where condition() is false. It should
break if you put address = 2; just under address = 1, for example.
julia
next prev parent reply other threads:[~2018-10-10 20:51 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-10 19:38 [Cocci] First coccinelle script, need some help Joel Fernandes
2018-10-10 20:23 ` Julia Lawall
2018-10-10 20:45 ` Joel Fernandes
2018-10-10 20:51 ` Julia Lawall [this message]
2018-10-10 21:11 ` Joel Fernandes
2018-10-10 21:12 ` Julia Lawall
[not found] ` <93da55ff-c807-6587-7ef3-3d2af820117d@users.sourceforge.net>
2018-10-11 15:43 ` [Cocci] Searching for parameter usages of pte_alloc() Joel Fernandes
2018-10-11 15:51 ` Julia Lawall
2018-10-11 16:28 ` Joel Fernandes
2018-10-11 16:40 ` Julia Lawall
2018-10-11 16:49 ` Joel Fernandes
2018-10-11 16:57 ` Julia Lawall
2018-10-11 17:06 ` Joel Fernandes
2018-10-11 18:06 ` Joel Fernandes
2018-10-11 18:07 ` Joel Fernandes
[not found] ` <cd2eb29e-775f-9c48-b839-b2ebdc3e3c56@users.sourceforge.net>
2018-10-11 23:54 ` Joel Fernandes
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