Re: [Cocci] [PATCH] coccinelle: memdup.cocci: fix matching rules

[Nicholas Mc Guire <der.herr@hofr.at>]

On Thu, 06 Aug 2015, Andrzej Hajda wrote:

> This patch fixes three things, listed in order of importance.
> 1. Removes matching of kmemdup from !patch rule - it is incorrect and
> in fact makes report mode unusable.
> 2. Adds unlikely to if clause. It allows to match more cases - the ones with
> unlikely and the ones without it.
> 3. Fixes report message.
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
> ---
> Hi Julia,
> 
> I guess 1st and 3rd changes are OK. I am not sure about 2nd change, without
> it I was not able to catch cases containing unlikely macro. For example
> fs/ntfs/dir.c:1175:
>   ir = kmalloc(rc, GFP_NOFS);
>   if (unlikely(!ir)) {
>     err = -ENOMEM;
>     goto err_out;
>   }
>   /* Copy the index root value (it has been verified in read_inode). */
>   memcpy(ir, (u8*)ctx->attr +
>     le16_to_cpu(ctx->attr->data.resident.value_offset), rc);
> 
> It seems quite strange for me, as these rules looks to me isomorphic.
> Is this expected behavior of coccinelle or just some bug?
> 
> After this fix, cocci finds 46 places to patch, I will send patchset if this
> change looks OK to you.
> 
> I have used:
> spatch version 1.0.1 with Python support and with PCRE support
> latest linux-next.
> 
> Regards
> Andrzej
> ---
>  scripts/coccinelle/api/memdup.cocci | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/scripts/coccinelle/api/memdup.cocci b/scripts/coccinelle/api/memdup.cocci
> index 3d1aa71..2297205 100644
> --- a/scripts/coccinelle/api/memdup.cocci
> +++ b/scripts/coccinelle/api/memdup.cocci
> @@ -39,7 +39,7 @@ statement S;
>  
>  -  to = \(kmalloc@p\|kzalloc@p\)(size,flag);
>  +  to = kmemdup(from,size,flag);
> -   if (to==NULL || ...) S
> +   if (unlikely(to==NULL) || ...) S
>  -  memcpy(to, from, size);

maybe I don't understand isomorphism declarations properly but
that should actually be covered by standard.iso:

@ unlikely @
expression E;
@@
unlikely(E) <=> likely(E) => E

??
so not clear why you would get more cases with this patch.

>  
>  @r depends on !patch@
> @@ -49,18 +49,17 @@ statement S;
>  @@
>  
>  *  to = \(kmalloc@p\|kzalloc@p\)(size,flag);
> -   to = kmemdup(from,size,flag);
> -   if (to==NULL || ...) S
> +   if (unlikely(to==NULL) || ...) S
>  *  memcpy(to, from, size);
>  
>  @script:python depends on org@
>  p << r.p;
>  @@
>  
> -coccilib.org.print_todo(p[0], "WARNING opportunity for kmemdep")
> +coccilib.org.print_todo(p[0], "WARNING opportunity for kmemdup")
>  
>  @script:python depends on report@
>  p << r.p;
>  @@
>  
> -coccilib.report.print_report(p[0], "WARNING opportunity for kmemdep")
> +coccilib.report.print_report(p[0], "WARNING opportunity for kmemdup")
> -- 
> 1.9.1
> 
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