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* [PATCH] IB/qib: Fix null pointer subtraction compiler warning
@ 2021-09-03 13:07 Jason Gunthorpe
  2021-09-03 17:24 ` Dennis Dalessandro
  2021-09-08 11:44 ` Jason Gunthorpe
  0 siblings, 2 replies; 3+ messages in thread
From: Jason Gunthorpe @ 2021-09-03 13:07 UTC (permalink / raw)
  To: Dennis Dalessandro, linux-rdma
  Cc: Leon Romanovsky, kernel test robot, Mike Marciniszyn, llvm,
	kbuild-all, linux-kernel

>> drivers/infiniband/hw/qib/qib_sysfs.c:411:1: warning: performing pointer subtraction with a null pointer has undefined behavior
+[-Wnull-pointer-subtraction]
   QIB_DIAGC_ATTR(rc_resends);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/infiniband/hw/qib/qib_sysfs.c:408:51: note: expanded from macro 'QIB_DIAGC_ATTR'
                   .counter = &((struct qib_ibport *)0)->rvp.n_##N - (u64 *)0,    \

Use offsetof and accomplish the type check using static_assert.

Fixes: 4a7aaf88c89f ("RDMA/qib: Use attributes for the port sysfs")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/infiniband/hw/qib/qib_sysfs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/qib/qib_sysfs.c b/drivers/infiniband/hw/qib/qib_sysfs.c
index d57e49de6650be..452e2355d24eeb 100644
--- a/drivers/infiniband/hw/qib/qib_sysfs.c
+++ b/drivers/infiniband/hw/qib/qib_sysfs.c
@@ -403,9 +403,11 @@ static ssize_t diagc_attr_store(struct ib_device *ibdev, u32 port_num,
 }
 
 #define QIB_DIAGC_ATTR(N)                                                      \
+	static_assert(&((struct qib_ibport *)0)->rvp.n_##N != (u64 *)NULL);    \
 	static struct qib_diagc_attr qib_diagc_attr_##N = {                    \
 		.attr = __ATTR(N, 0664, diagc_attr_show, diagc_attr_store),    \
-		.counter = &((struct qib_ibport *)0)->rvp.n_##N - (u64 *)0,    \
+		.counter =                                                     \
+			offsetof(struct qib_ibport, rvp.n_##N) / sizeof(u64)   \
 	}
 
 QIB_DIAGC_ATTR(rc_resends);

base-commit: 6a217437f9f5482a3f6f2dc5fcd27cf0f62409ac
-- 
2.33.0


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] IB/qib: Fix null pointer subtraction compiler warning
  2021-09-03 13:07 [PATCH] IB/qib: Fix null pointer subtraction compiler warning Jason Gunthorpe
@ 2021-09-03 17:24 ` Dennis Dalessandro
  2021-09-08 11:44 ` Jason Gunthorpe
  1 sibling, 0 replies; 3+ messages in thread
From: Dennis Dalessandro @ 2021-09-03 17:24 UTC (permalink / raw)
  To: Jason Gunthorpe, linux-rdma
  Cc: Leon Romanovsky, kernel test robot, Mike Marciniszyn, llvm,
	kbuild-all, linux-kernel

On 9/3/21 9:07 AM, Jason Gunthorpe wrote:
>>> drivers/infiniband/hw/qib/qib_sysfs.c:411:1: warning: performing pointer subtraction with a null pointer has undefined behavior
> +[-Wnull-pointer-subtraction]
>    QIB_DIAGC_ATTR(rc_resends);
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~
>    drivers/infiniband/hw/qib/qib_sysfs.c:408:51: note: expanded from macro 'QIB_DIAGC_ATTR'
>                    .counter = &((struct qib_ibport *)0)->rvp.n_##N - (u64 *)0,    \
> 
> Use offsetof and accomplish the type check using static_assert.
> 
> Fixes: 4a7aaf88c89f ("RDMA/qib: Use attributes for the port sysfs")
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  drivers/infiniband/hw/qib/qib_sysfs.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/hw/qib/qib_sysfs.c b/drivers/infiniband/hw/qib/qib_sysfs.c
> index d57e49de6650be..452e2355d24eeb 100644
> --- a/drivers/infiniband/hw/qib/qib_sysfs.c
> +++ b/drivers/infiniband/hw/qib/qib_sysfs.c
> @@ -403,9 +403,11 @@ static ssize_t diagc_attr_store(struct ib_device *ibdev, u32 port_num,
>  }
>  
>  #define QIB_DIAGC_ATTR(N)                                                      \
> +	static_assert(&((struct qib_ibport *)0)->rvp.n_##N != (u64 *)NULL);    \
>  	static struct qib_diagc_attr qib_diagc_attr_##N = {                    \
>  		.attr = __ATTR(N, 0664, diagc_attr_show, diagc_attr_store),    \
> -		.counter = &((struct qib_ibport *)0)->rvp.n_##N - (u64 *)0,    \
> +		.counter =                                                     \
> +			offsetof(struct qib_ibport, rvp.n_##N) / sizeof(u64)   \
>  	}
>  
>  QIB_DIAGC_ATTR(rc_resends);
> 
> base-commit: 6a217437f9f5482a3f6f2dc5fcd27cf0f62409ac
> 

Looks fine.

Acked-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] IB/qib: Fix null pointer subtraction compiler warning
  2021-09-03 13:07 [PATCH] IB/qib: Fix null pointer subtraction compiler warning Jason Gunthorpe
  2021-09-03 17:24 ` Dennis Dalessandro
@ 2021-09-08 11:44 ` Jason Gunthorpe
  1 sibling, 0 replies; 3+ messages in thread
From: Jason Gunthorpe @ 2021-09-08 11:44 UTC (permalink / raw)
  To: Dennis Dalessandro, linux-rdma
  Cc: Leon Romanovsky, kernel test robot, Mike Marciniszyn, llvm,
	kbuild-all, linux-kernel

On Fri, Sep 03, 2021 at 10:07:28AM -0300, Jason Gunthorpe wrote:
> >> drivers/infiniband/hw/qib/qib_sysfs.c:411:1: warning: performing pointer subtraction with a null pointer has undefined behavior
> +[-Wnull-pointer-subtraction]
>    QIB_DIAGC_ATTR(rc_resends);
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~
>    drivers/infiniband/hw/qib/qib_sysfs.c:408:51: note: expanded from macro 'QIB_DIAGC_ATTR'
>                    .counter = &((struct qib_ibport *)0)->rvp.n_##N - (u64 *)0,    \
> 
> Use offsetof and accomplish the type check using static_assert.
> 
> Fixes: 4a7aaf88c89f ("RDMA/qib: Use attributes for the port sysfs")
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> Acked-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
> ---
>  drivers/infiniband/hw/qib/qib_sysfs.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Applied to for-rc

Jason

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-09-08 11:44 UTC | newest]

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2021-09-03 13:07 [PATCH] IB/qib: Fix null pointer subtraction compiler warning Jason Gunthorpe
2021-09-03 17:24 ` Dennis Dalessandro
2021-09-08 11:44 ` Jason Gunthorpe

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