netdev - [PATCH net 3/3] ethernet: ice: avoid gcc-9 integer overflow warning

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Date:   Tue,  7 Mar 2023 14:07:14 -0800
From:   Tony Nguyen <anthony.l.nguyen@...el.com>
To:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        edumazet@...gle.com, netdev@...r.kernel.org
Cc:     Arnd Bergmann <arnd@...db.de>, anthony.l.nguyen@...el.com,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Sujai Buvaneswaran <sujai.buvaneswaran@...el.com>
Subject: [PATCH net 3/3] ethernet: ice: avoid gcc-9 integer overflow warning

From: Arnd Bergmann <arnd@...db.de>

With older compilers like gcc-9, the calculation of the vlan
priority field causes a false-positive warning from the byteswap:

In file included from drivers/net/ethernet/intel/ice/ice_tc_lib.c:4:
drivers/net/ethernet/intel/ice/ice_tc_lib.c: In function 'ice_parse_cls_flower':
include/uapi/linux/swab.h:15:15: error: integer overflow in expression '(int)(short unsigned int)((int)match.key-><U67c8>.<U6698>.vlan_priority << 13) & 57344 & 255' of type 'int' results in '0' [-Werror=overflow]
   15 |  (((__u16)(x) & (__u16)0x00ffU) << 8) |   \
      |   ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
include/uapi/linux/swab.h:106:2: note: in expansion of macro '___constant_swab16'
  106 |  ___constant_swab16(x) :   \
      |  ^~~~~~~~~~~~~~~~~~
include/uapi/linux/byteorder/little_endian.h:42:43: note: in expansion of macro '__swab16'
   42 | #define __cpu_to_be16(x) ((__force __be16)__swab16((x)))
      |                                           ^~~~~~~~
include/linux/byteorder/generic.h:96:21: note: in expansion of macro '__cpu_to_be16'
   96 | #define cpu_to_be16 __cpu_to_be16
      |                     ^~~~~~~~~~~~~
drivers/net/ethernet/intel/ice/ice_tc_lib.c:1458:5: note: in expansion of macro 'cpu_to_be16'
 1458 |     cpu_to_be16((match.key->vlan_priority <<
      |     ^~~~~~~~~~~

After a change to be16_encode_bits(), the code becomes more
readable to both people and compilers, which avoids the warning.

Fixes: 34800178b302 ("ice: Add support for VLAN priority filters in switchdev")
Suggested-by: Alexander Lobakin <alexandr.lobakin@...el.com>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Alexander Lobakin <alexandr.lobakin@...el.com>
Tested-by: Sujai Buvaneswaran <sujai.buvaneswaran@...el.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
---
 drivers/net/ethernet/intel/ice/ice_tc_lib.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_tc_lib.c b/drivers/net/ethernet/intel/ice/ice_tc_lib.c
index 6b48cbc049c6..76f29a5bf8d7 100644
--- a/drivers/net/ethernet/intel/ice/ice_tc_lib.c
+++ b/drivers/net/ethernet/intel/ice/ice_tc_lib.c
@@ -1455,8 +1455,8 @@ ice_parse_cls_flower(struct net_device *filter_dev, struct ice_vsi *vsi,
 		if (match.mask->vlan_priority) {
 			fltr->flags |= ICE_TC_FLWR_FIELD_VLAN_PRIO;
 			headers->vlan_hdr.vlan_prio =
-				cpu_to_be16((match.key->vlan_priority <<
-					     VLAN_PRIO_SHIFT) & VLAN_PRIO_MASK);
+				be16_encode_bits(match.key->vlan_priority,
+						 VLAN_PRIO_MASK);
 		}
 
 		if (match.mask->vlan_tpid)
@@ -1489,8 +1489,8 @@ ice_parse_cls_flower(struct net_device *filter_dev, struct ice_vsi *vsi,
 		if (match.mask->vlan_priority) {
 			fltr->flags |= ICE_TC_FLWR_FIELD_CVLAN_PRIO;
 			headers->cvlan_hdr.vlan_prio =
-				cpu_to_be16((match.key->vlan_priority <<
-					     VLAN_PRIO_SHIFT) & VLAN_PRIO_MASK);
+				be16_encode_bits(match.key->vlan_priority,
+						 VLAN_PRIO_MASK);
 		}
 	}
 
-- 
2.38.1