[PATCH] edac: Do alignment logic properly in edac_align_ptr()

[PATCH] edac: Do alignment logic properly in edac_align_ptr()

[Chris Metcalf]

The logic was checking the sizeof the structure being allocated to
determine whether an alignment fixup was required.  This isn't right;
what we actually care about is the alignment of the actual pointer that's
about to be returned.  This became an issue recently because struct
edac_mc_layer has a size that is not zero modulo eight, so we were
taking the correctly-aligned pointer and forcing it to be misaligned.
On Tile this caused an alignment exception.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
---
Mauro, I assume you will push this through your tree?  I am also happy
to push it through the tile tree.  Let me know!

 drivers/edac/edac_mc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
index 10f3750..de5ba86 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -164,7 +164,7 @@ void *edac_align_ptr(void **p, unsigned size, int n_elems)
 	else
 		return (char *)ptr;
 
-	r = size % align;
+	r = (unsigned long)p % align;
 
 	if (r == 0)
 		return (char *)ptr;
-- 
1.6.5.2

Re: [PATCH] edac: Do alignment logic properly in edac_align_ptr()

[Chris Metcalf]

On 6/6/2012 1:24 PM, Chris Metcalf wrote:
> The logic was checking the sizeof the structure being allocated to
> determine whether an alignment fixup was required.  This isn't right;
> what we actually care about is the alignment of the actual pointer that's
> about to be returned.  This became an issue recently because struct
> edac_mc_layer has a size that is not zero modulo eight, so we were
> taking the correctly-aligned pointer and forcing it to be misaligned.
> On Tile this caused an alignment exception.
>
> Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
> ---
> Mauro, I assume you will push this through your tree?  I am also happy
> to push it through the tile tree.  Let me know!

Ping - I see this didn't make it into 3.5-rc2.  I'm happy to push the change
through the tile tree if that's helpful (and someone wants to give their
Acked-by).

>
>  drivers/edac/edac_mc.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
> index 10f3750..de5ba86 100644
> --- a/drivers/edac/edac_mc.c
> +++ b/drivers/edac/edac_mc.c
> @@ -164,7 +164,7 @@ void *edac_align_ptr(void **p, unsigned size, int n_elems)
>  	else
>  		return (char *)ptr;
>  
> -	r = size % align;
> +	r = (unsigned long)p % align;
>  
>  	if (r == 0)
>  		return (char *)ptr;

-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com

Re: [PATCH] edac: Do alignment logic properly in edac_align_ptr()

[Mauro Carvalho Chehab]

Em 11-06-2012 12:35, Chris Metcalf escreveu:
> On 6/6/2012 1:24 PM, Chris Metcalf wrote:
>> The logic was checking the sizeof the structure being allocated to
>> determine whether an alignment fixup was required.  This isn't right;
>> what we actually care about is the alignment of the actual pointer that's
>> about to be returned.  This became an issue recently because struct
>> edac_mc_layer has a size that is not zero modulo eight, so we were
>> taking the correctly-aligned pointer and forcing it to be misaligned.
>> On Tile this caused an alignment exception.
>>
>> Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
>> ---
>> Mauro, I assume you will push this through your tree?  I am also happy
>> to push it through the tile tree.  Let me know!
> 
> Ping - I see this didn't make it into 3.5-rc2.  I'm happy to push the change
> through the tile tree if that's helpful (and someone wants to give their
> Acked-by).

Sorry, I took some days off to rest. I'll be applying it today on my -next tree
and likely tomorrow upstream, together with a few other EDAC fixes.

Regards,
Mauro
> 
>>
>>   drivers/edac/edac_mc.c |    2 +-
>>   1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
>> index 10f3750..de5ba86 100644
>> --- a/drivers/edac/edac_mc.c
>> +++ b/drivers/edac/edac_mc.c
>> @@ -164,7 +164,7 @@ void *edac_align_ptr(void **p, unsigned size, int n_elems)
>>   	else
>>   		return (char *)ptr;
>>   
>> -	r = size % align;
>> +	r = (unsigned long)p % align;
>>   
>>   	if (r == 0)
>>   		return (char *)ptr;
>