linux-kernel - Re: [Cocci] [v3 05/10] mmap locking API: Checking the Coccinelle software

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Date:   Sat, 28 Mar 2020 14:53:40 +0100 (CET)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Markus Elfring <Markus.Elfring@....de>
cc:     Michel Lespinasse <walken@...gle.com>,
        Coccinelle <cocci@...teme.lip6.fr>, linux-mm@...ck.org,
        Davidlohr Bueso <dave@...olabs.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Hugh Dickins <hughd@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Liam Howlett <Liam.Howlett@...cle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Matthew Wilcox <willy@...radead.org>,
        Ying Han <yinghan@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [Cocci] [v3 05/10] mmap locking API: Checking the Coccinelle
 software

On Sat, 28 Mar 2020, Markus Elfring wrote:

> >> 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/arch/mips/mm/fault.c?id=69c5eea3128e775fd3c70ecf0098105d96dee330#n34
>
> // deleted part
> static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
> 	unsigned long address)
> {
> 	struct vm_area_struct * vma = NULL;
> 	struct task_struct *tsk = current;
> 	struct mm_struct *mm = tsk->mm;
> // deleted part
> retry:
> 	down_read(&mm->mmap_sem);
> 	vma = find_vma(mm, address);
> 	if (!vma)
> 		goto bad_area;
> // deleted part
> }
> // deleted part
>
>
> Application of the software “Coccinelle 1.0.8-00029-ga549b9f0” (OCaml 4.10.0)
>
> elfring@...ne:~/Projekte/Coccinelle/Probe> spatch --parse-c do_page_fault-excerpt3.c
> …
> NB total files = 1; perfect = 1; pbs = 0; timeout = 0; =========> 100%
> nb good = 15,  nb passed = 1 =========> 6.25% passed
> nb good = 15,  nb bad = 0 =========> 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@...ne:~/Projekte/Coccinelle/Probe> spatch use_mmap_locking_API_3.cocci do_page_fault-excerpt3.c
>
>
> The desired diff is not generated so far.
> How would you like to fix this situation?

The problem is due to a preceding goto where the destination is expressed
as a macro name.  Maybe there should be a warning in this case.

julia

>
> Regards,
> Markus
> _______________________________________________
> Cocci mailing list
> Cocci@...teme.lip6.fr
> https://systeme.lip6.fr/mailman/listinfo/cocci
>

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