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Subject: Re: [v3 05/10] mmap locking API: Checking the Coccinelle software
To:     Michel Lespinasse <walken@google.com>,
        Coccinelle <cocci@systeme.lip6.fr>, linux-mm@kvack.org
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Laurent Dufour <ldufour@linux.ibm.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Matthew Wilcox <willy@infradead.org>,
        Liam Howlett <Liam.Howlett@oracle.com>,
        Jerome Glisse <jglisse@redhat.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        David Rientjes <rientjes@google.com>,
        Hugh Dickins <hughd@google.com>, Ying Han <yinghan@google.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Andrew Morton <akpm@linux-foundation.org>
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From:   Markus Elfring <Markus.Elfring@web.de>
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Date:   Sat, 28 Mar 2020 14:20:20 +0100
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Sender: linux-kernel-owner@vger.kernel.org
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>> How will corresponding software development resources evolve?
>
> I don't think I understand the question, or, actually, are you asking
> me or the coccinelle developers ?

I hope that another communication approach can eventually increase
the chances for a better common understanding of development challenges.

The code from a mentioned source file can be reduced to the following
test file.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/ar=
ch/mips/mm/fault.c?id=3D69c5eea3128e775fd3c70ecf0098105d96dee330#n34

// deleted part
static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long =
write,
	unsigned long address)
{
	struct vm_area_struct * vma =3D NULL;
	struct task_struct *tsk =3D current;
	struct mm_struct *mm =3D tsk->mm;
// deleted part
retry:
	down_read(&mm->mmap_sem);
	vma =3D find_vma(mm, address);
	if (!vma)
		goto bad_area;
// deleted part
}
// deleted part


Application of the software =E2=80=9CCoccinelle 1.0.8-00029-ga549b9f0=E2=
=80=9D (OCaml 4.10.0)

elfring@Sonne:~/Projekte/Coccinelle/Probe> spatch --parse-c do_page_fault-=
excerpt3.c
=E2=80=A6
NB total files =3D 1; perfect =3D 1; pbs =3D 0; timeout =3D 0; =3D=3D=3D=
=3D=3D=3D=3D=3D=3D> 100%
nb good =3D 15,  nb passed =3D 1 =3D=3D=3D=3D=3D=3D=3D=3D=3D> 6.25% passed
nb good =3D 15,  nb bad =3D 0 =3D=3D=3D=3D=3D=3D=3D=3D=3D> 100.00% good or=
 passed


The discussed transformation approach can also be reduced for a test
to the following script for the semantic patch language.

@replacement@
expression x;
@@
-down_read
+mmap_read_lock
 (
- &
  x
- ->mmap_sem
 )


elfring@Sonne:~/Projekte/Coccinelle/Probe> spatch use_mmap_locking_API_3.c=
occi do_page_fault-excerpt3.c


The desired diff is not generated so far.
How would you like to fix this situation?

Regards,
Markus