* [PATCH 9/10] drivers/mmc: Move a dereference below a NULL test
@ 2009-07-19 15:30 Julia Lawall
2009-07-20 8:01 ` Adrian Hunter
0 siblings, 1 reply; 5+ messages in thread
From: Julia Lawall @ 2009-07-19 15:30 UTC (permalink / raw)
To: jarkko.lavinen, linux-omap, linux-kernel, kernel-janitors
From: Julia Lawall <julia@diku.dk>
If the NULL test is necessary, then the dereference should be moved below
the NULL test.
The semantic patch that makes this change is as follows:
(http://www.emn.fr/x-info/coccinelle/)
// <smpl>
@@
type T;
expression E,E1;
identifier i,fld;
statement S;
@@
- T i = E->fld;
+ T i;
... when != E=E1
when != i
BUG_ON (E == NULL||
- i
+ E->fld
== NULL || ...);
+ i = E->fld;
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
---
drivers/mmc/host/omap.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
index e7a331d..89281ab 100644
--- a/drivers/mmc/host/omap.c
+++ b/drivers/mmc/host/omap.c
@@ -255,11 +255,12 @@ static void mmc_omap_slot_release_work(struct work_struct *work)
static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int clk_enabled)
{
- struct mmc_omap_host *host = slot->host;
+ struct mmc_omap_host *host;
unsigned long flags;
int i;
- BUG_ON(slot == NULL || host->mmc == NULL);
+ BUG_ON(slot == NULL || slot->host->mmc == NULL);
+ host = slot->host;
if (clk_enabled)
/* Keeps clock running for at least 8 cycles on valid freq */
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH 9/10] drivers/mmc: Move a dereference below a NULL test
2009-07-19 15:30 [PATCH 9/10] drivers/mmc: Move a dereference below a NULL test Julia Lawall
@ 2009-07-20 8:01 ` Adrian Hunter
2009-07-20 12:33 ` arun c
0 siblings, 1 reply; 5+ messages in thread
From: Adrian Hunter @ 2009-07-20 8:01 UTC (permalink / raw)
To: Julia Lawall
Cc: Lavinen Jarkko (Nokia-D/Helsinki), linux-omap@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Julia Lawall wrote:
> From: Julia Lawall <julia@diku.dk>
>
> If the NULL test is necessary, then the dereference should be moved below
> the NULL test.
>
> The semantic patch that makes this change is as follows:
> (http://www.emn.fr/x-info/coccinelle/)
>
> // <smpl>
> @@
> type T;
> expression E,E1;
> identifier i,fld;
> statement S;
> @@
>
> - T i = E->fld;
> + T i;
> ... when != E=E1
> when != i
> BUG_ON (E == NULL||
> - i
> + E->fld
> == NULL || ...);
> + i = E->fld;
> // </smpl>
>
> Signed-off-by: Julia Lawall <julia@diku.dk>
>
> ---
> drivers/mmc/host/omap.c | 5 +++--
> 1 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
> index e7a331d..89281ab 100644
> --- a/drivers/mmc/host/omap.c
> +++ b/drivers/mmc/host/omap.c
> @@ -255,11 +255,12 @@ static void mmc_omap_slot_release_work(struct work_struct *work)
>
> static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int clk_enabled)
> {
> - struct mmc_omap_host *host = slot->host;
> + struct mmc_omap_host *host;
> unsigned long flags;
> int i;
>
> - BUG_ON(slot == NULL || host->mmc == NULL);
> + BUG_ON(slot == NULL || slot->host->mmc == NULL);
> + host = slot->host;
>
> if (clk_enabled)
> /* Keeps clock running for at least 8 cycles on valid freq */
> --
If slot is NULL it will oops anyway, so the following is better IMHO:
static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int clk_enabled)
{
struct mmc_omap_host *host = slot->host;
unsigned long flags;
int i;
> - BUG_ON(slot == NULL || host->mmc == NULL);
> + BUG_ON(host->mmc == NULL);
if (clk_enabled)
/* Keeps clock running for at least 8 cycles on valid freq */
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH 9/10] drivers/mmc: Move a dereference below a NULL test
2009-07-20 8:01 ` Adrian Hunter
@ 2009-07-20 12:33 ` arun c
2009-07-20 12:43 ` Adrian Hunter
0 siblings, 1 reply; 5+ messages in thread
From: arun c @ 2009-07-20 12:33 UTC (permalink / raw)
To: Adrian Hunter
Cc: Julia Lawall, Lavinen Jarkko (Nokia-D/Helsinki),
linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-janitors@vger.kernel.org
On Mon, Jul 20, 2009 at 1:31 PM, Adrian Hunter<adrian.hunter@nokia.com> wrote:
> Julia Lawall wrote:
>>
>> From: Julia Lawall <julia@diku.dk>
>>
>> If the NULL test is necessary, then the dereference should be moved below
>> the NULL test.
>>
>> The semantic patch that makes this change is as follows:
>> (http://www.emn.fr/x-info/coccinelle/)
>>
>> // <smpl>
>> @@
>> type T;
>> expression E,E1;
>> identifier i,fld;
>> statement S;
>> @@
>>
>> - T i = E->fld;
>> + T i;
>> ... when != E=E1
>> when != i
>> BUG_ON (E == NULL||
>> - i
>> + E->fld
>> == NULL || ...);
>> + i = E->fld;
>> // </smpl>
>>
>> Signed-off-by: Julia Lawall <julia@diku.dk>
>>
>> ---
>> drivers/mmc/host/omap.c | 5 +++--
>> 1 files changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
>> index e7a331d..89281ab 100644
>> --- a/drivers/mmc/host/omap.c
>> +++ b/drivers/mmc/host/omap.c
>> @@ -255,11 +255,12 @@ static void mmc_omap_slot_release_work(struct
>> work_struct *work)
>> static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int
>> clk_enabled)
>> {
>> - struct mmc_omap_host *host = slot->host;
>> + struct mmc_omap_host *host;
>> unsigned long flags;
>> int i;
>> - BUG_ON(slot == NULL || host->mmc == NULL);
>> + BUG_ON(slot == NULL || slot->host->mmc == NULL);
>> + host = slot->host;
>> if (clk_enabled)
>> /* Keeps clock running for at least 8 cycles on valid freq
>> */
>> --
>
> If slot is NULL it will oops anyway, so the following is better IMHO:
>
> static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int
> clk_enabled)
> {
> struct mmc_omap_host *host = slot->host;
> unsigned long flags;
> int i;
>
>> - BUG_ON(slot == NULL || host->mmc == NULL);
>> + BUG_ON(host->mmc == NULL);
>
> if (clk_enabled)
> /* Keeps clock running for at least 8 cycles on valid freq */
> --
According to http://isc.sans.org/diary.html?storyid=6820&rss "NULL check"
must be done before assigning the values. Does Julia Lawall's version
is the more correct one??
Arun
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH 9/10] drivers/mmc: Move a dereference below a NULL test
2009-07-20 12:33 ` arun c
@ 2009-07-20 12:43 ` Adrian Hunter
2009-07-20 12:47 ` Alan Cox
0 siblings, 1 reply; 5+ messages in thread
From: Adrian Hunter @ 2009-07-20 12:43 UTC (permalink / raw)
To: arun c
Cc: Julia Lawall, Lavinen Jarkko (Nokia-D/Helsinki),
linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-janitors@vger.kernel.org
arun c wrote:
> On Mon, Jul 20, 2009 at 1:31 PM, Adrian Hunter<adrian.hunter@nokia.com> wrote:
>> Julia Lawall wrote:
>>> From: Julia Lawall <julia@diku.dk>
>>>
>>> If the NULL test is necessary, then the dereference should be moved below
>>> the NULL test.
>>>
>>> The semantic patch that makes this change is as follows:
>>> (http://www.emn.fr/x-info/coccinelle/)
>>>
>>> // <smpl>
>>> @@
>>> type T;
>>> expression E,E1;
>>> identifier i,fld;
>>> statement S;
>>> @@
>>>
>>> - T i = E->fld;
>>> + T i;
>>> ... when != E=E1
>>> when != i
>>> BUG_ON (E == NULL||
>>> - i
>>> + E->fld
>>> == NULL || ...);
>>> + i = E->fld;
>>> // </smpl>
>>>
>>> Signed-off-by: Julia Lawall <julia@diku.dk>
>>>
>>> ---
>>> drivers/mmc/host/omap.c | 5 +++--
>>> 1 files changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
>>> index e7a331d..89281ab 100644
>>> --- a/drivers/mmc/host/omap.c
>>> +++ b/drivers/mmc/host/omap.c
>>> @@ -255,11 +255,12 @@ static void mmc_omap_slot_release_work(struct
>>> work_struct *work)
>>> static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int
>>> clk_enabled)
>>> {
>>> - struct mmc_omap_host *host = slot->host;
>>> + struct mmc_omap_host *host;
>>> unsigned long flags;
>>> int i;
>>> - BUG_ON(slot == NULL || host->mmc == NULL);
>>> + BUG_ON(slot == NULL || slot->host->mmc == NULL);
>>> + host = slot->host;
>>> if (clk_enabled)
>>> /* Keeps clock running for at least 8 cycles on valid freq
>>> */
>>> --
>> If slot is NULL it will oops anyway, so the following is better IMHO:
>>
>> static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int
>> clk_enabled)
>> {
>> struct mmc_omap_host *host = slot->host;
>> unsigned long flags;
>> int i;
>>
>>> - BUG_ON(slot == NULL || host->mmc == NULL);
>>> + BUG_ON(host->mmc == NULL);
>> if (clk_enabled)
>> /* Keeps clock running for at least 8 cycles on valid freq */
>> --
>
> According to http://isc.sans.org/diary.html?storyid=6820&rss "NULL check"
> must be done before assigning the values. Does Julia Lawall's version
> is the more correct one??
>
> Arun
It is not a "NULL check" it is an assertion, which can be compiled out.
On some platforms BUG is implemented as a null dereference anyway
e.g. on ARM it is *(int *)0 = 0;
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH 9/10] drivers/mmc: Move a dereference below a NULL test
2009-07-20 12:43 ` Adrian Hunter
@ 2009-07-20 12:47 ` Alan Cox
0 siblings, 0 replies; 5+ messages in thread
From: Alan Cox @ 2009-07-20 12:47 UTC (permalink / raw)
To: Adrian Hunter
Cc: arun c, Julia Lawall, Lavinen Jarkko (Nokia-D/Helsinki),
linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-janitors@vger.kernel.org
> It is not a "NULL check" it is an assertion, which can be compiled out.
> On some platforms BUG is implemented as a null dereference anyway
> e.g. on ARM it is *(int *)0 = 0;
It's a bogus check because the
struct mmc_omap_host *host = slot->host;
has already been executed before you check for slot == NULL
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2009-07-20 12:46 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2009-07-19 15:30 [PATCH 9/10] drivers/mmc: Move a dereference below a NULL test Julia Lawall
2009-07-20 8:01 ` Adrian Hunter
2009-07-20 12:33 ` arun c
2009-07-20 12:43 ` Adrian Hunter
2009-07-20 12:47 ` Alan Cox
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