All of lore.kernel.org
 help / color / mirror / Atom feed
From: Jason Gunthorpe <jgg@nvidia.com>
To: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>,
	linux-rdma@vger.kernel.org
Cc: Leon Romanovsky <leonro@nvidia.com>,
	kernel test robot <lkp@intel.com>,
	Mike Marciniszyn <mike.marciniszyn@cornelisnetworks.com>,
	llvm@lists.linux.dev, kbuild-all@lists.01.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH] IB/qib: Fix null pointer subtraction compiler warning
Date: Fri,  3 Sep 2021 10:07:28 -0300	[thread overview]
Message-ID: <0-v1-43ae3c759177+65-qib_type_jgg@nvidia.com> (raw)

>> 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


WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@nvidia.com>
To: kbuild-all@lists.01.org
Subject: [PATCH] IB/qib: Fix null pointer subtraction compiler warning
Date: Fri, 03 Sep 2021 10:07:28 -0300	[thread overview]
Message-ID: <0-v1-43ae3c759177+65-qib_type_jgg@nvidia.com> (raw)

[-- Attachment #1: Type: text/plain, Size: 1683 bytes --]

>> 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

             reply	other threads:[~2021-09-03 13:07 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-03 13:07 Jason Gunthorpe [this message]
2021-09-03 13:07 ` [PATCH] IB/qib: Fix null pointer subtraction compiler warning Jason Gunthorpe
2021-09-03 17:24 ` Dennis Dalessandro
2021-09-03 17:24   ` Dennis Dalessandro
2021-09-08 11:44 ` Jason Gunthorpe
2021-09-08 11:44   ` Jason Gunthorpe

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=0-v1-43ae3c759177+65-qib_type_jgg@nvidia.com \
    --to=jgg@nvidia.com \
    --cc=dennis.dalessandro@cornelisnetworks.com \
    --cc=kbuild-all@lists.01.org \
    --cc=leonro@nvidia.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-rdma@vger.kernel.org \
    --cc=lkp@intel.com \
    --cc=llvm@lists.linux.dev \
    --cc=mike.marciniszyn@cornelisnetworks.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.