linux-kernel - Re: [Cocci] [PATCH 1/2] Coccinelle: extend memdup_user transformation with GFP

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Date:   Sat, 6 Jun 2020 23:46:11 +0300
From:   Denis Efremov <efremov@...ux.com>
To:     Julia Lawall <julia.lawall@...ia.fr>
Cc:     Joe Perches <joe@...ches.com>, cocci@...teme.lip6.fr,
        linux-kernel@...r.kernel.org
Subject: Re: [Cocci] [PATCH 1/2] Coccinelle: extend memdup_user transformation
 with GFP_USER



On 6/6/20 11:24 AM, Julia Lawall wrote:
> 
> 
> On Sat, 30 May 2020, Denis Efremov wrote:
> 
>> Match GFP_USER allocations with memdup_user.cocci rule.
>> Commit 6c2c97a24f09 ("memdup_user(): switch to GFP_USER") switched
>> memdup_user() from GFP_KERNEL to GFP_USER. In most cases it is still
>> a good idea to use memdup_user() for GFP_KERNEL allocations. The
>> motivation behind altering memdup_user() to GFP_USER is here:
>> https://lkml.org/lkml/2018/1/6/333
> 
> Should the rule somehow document the cases in which memdup_user should now
> not be used?
> 
> julia
> 
> 
>>
>> Signed-off-by: Denis Efremov <efremov@...ux.com>
>> ---
>>  scripts/coccinelle/api/memdup_user.cocci | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/scripts/coccinelle/api/memdup_user.cocci b/scripts/coccinelle/api/memdup_user.cocci
>> index c809ab10bbce..49f487e6a5c8 100644
>> --- a/scripts/coccinelle/api/memdup_user.cocci
>> +++ b/scripts/coccinelle/api/memdup_user.cocci
>> @@ -20,7 +20,7 @@ expression from,to,size;
>>  identifier l1,l2;
>>  @@
>>
>> --  to = \(kmalloc\|kzalloc\)(size,GFP_KERNEL);
>> +-  to = \(kmalloc\|kzalloc\)(size,\(GFP_KERNEL\|GFP_USER\));

Actually, we can add optional __GFP_NOWARN here to match such cases as:
GFP_KERNEL | __GFP_NOWARN

However, I don't know how to express it in elegant way. Something like?
(
-  to = \(kmalloc\|kzalloc\)(size,\(GFP_KERNEL\|GFP_USER\));
|
-  to = \(kmalloc\|kzalloc\)(size, GFP_KERNEL|__GFP_NOWARN);
|
-  to = \(kmalloc\|kzalloc\)(size, GFP_USER|__GFP_NOWARN);
)

Thanks,
Denis