Re: [v3 05/10] mmap locking API: Checking the Coccinelle software

Markus Elfring
2020-03-28T13:21:01Z

>> 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@Sonne:~/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@Sonne:~/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?

Regards,
Markus