2006-12-04 14:56:51

by Martin Schwidefsky

Subject: [S390] cio: Make ccw_dev_id_is_equal() more robust.

From: Cornelia Huck <[email protected]>

[S390] cio: Make ccw_dev_id_is_equal() more robust.

Using memcmp to compare ccw_dev_id implies that the whole structure (incl.
padding) has always been completely initialized to sane values. Comparing
the structures field by field doesn't make such assumptions.

Signed-off-by: Cornelia Huck <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>
---

include/asm-s390/cio.h | 5 ++++-
1 files changed, 4 insertions(+), 1 deletion(-)

diff -urpN linux-2.6/include/asm-s390/cio.h linux-2.6-patched/include/asm-s390/cio.h
--- linux-2.6/include/asm-s390/cio.h 2006-12-04 14:50:48.000000000 +0100
+++ linux-2.6-patched/include/asm-s390/cio.h 2006-12-04 14:51:00.000000000 +0100
@@ -278,7 +278,10 @@ struct ccw_dev_id {
static inline int ccw_dev_id_is_equal(struct ccw_dev_id *dev_id1,
struct ccw_dev_id *dev_id2)
{
- return !memcmp(dev_id1, dev_id2, sizeof(struct ccw_dev_id));
+ if ((dev_id1->ssid == dev_id2->ssid) &&
+ (dev_id1->devno == dev_id2->devno))
+ return 1;
+ return 0;
}

extern int diag210(struct diag210 *addr);

2006-12-04 15:24:53

by Josef Sipek

Subject: Re: [S390] cio: Make ccw_dev_id_is_equal() more robust.

On Mon, Dec 04, 2006 at 03:56:24PM +0100, Martin Schwidefsky wrote:
...
> diff -urpN linux-2.6/include/asm-s390/cio.h linux-2.6-patched/include/asm-s390/cio.h
> --- linux-2.6/include/asm-s390/cio.h 2006-12-04 14:50:48.000000000 +0100
> +++ linux-2.6-patched/include/asm-s390/cio.h 2006-12-04 14:51:00.000000000 +0100
> @@ -278,7 +278,10 @@ struct ccw_dev_id {
> static inline int ccw_dev_id_is_equal(struct ccw_dev_id *dev_id1,
> struct ccw_dev_id *dev_id2)
> {
> - return !memcmp(dev_id1, dev_id2, sizeof(struct ccw_dev_id));
> + if ((dev_id1->ssid == dev_id2->ssid) &&
> + (dev_id1->devno == dev_id2->devno))
> + return 1;
> + return 0;
> }

Why not just:

return ((dev_id1->ssid == ......) && (...));

?

Josef "Jeff" Sipek.

--
UNIX is user-friendly ... it's just selective about who it's friends are

2006-12-04 15:30:27

by Martin Schwidefsky

Subject: Re: [S390] cio: Make ccw_dev_id_is_equal() more robust.

On Mon, 2006-12-04 at 10:23 -0500, Josef Sipek wrote:
> > diff -urpN linux-2.6/include/asm-s390/cio.h linux-2.6-patched/include/asm-s390/cio.h
> > --- linux-2.6/include/asm-s390/cio.h 2006-12-04 14:50:48.000000000 +0100
> > +++ linux-2.6-patched/include/asm-s390/cio.h 2006-12-04 14:51:00.000000000 +0100
> > @@ -278,7 +278,10 @@ struct ccw_dev_id {
> > static inline int ccw_dev_id_is_equal(struct ccw_dev_id *dev_id1,
> > struct ccw_dev_id *dev_id2)
> > {
> > - return !memcmp(dev_id1, dev_id2, sizeof(struct ccw_dev_id));
> > + if ((dev_id1->ssid == dev_id2->ssid) &&
> > + (dev_id1->devno == dev_id2->devno))
> > + return 1;
> > + return 0;
> > }
>
> Why not just:
>
> return ((dev_id1->ssid == ......) && (...));

Yes, why not. It would be a little bit shorter. The compiler probably
won't care and generate the same code..

--
blue skies,
Martin.

Martin Schwidefsky
Linux for zSeries Development & Services
IBM Deutschland Entwicklung GmbH

"Reality continues to ruin my life." - Calvin.