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

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Message-Id: <20230214132002.1498163-1-arnd@kernel.org>
Date:   Tue, 14 Feb 2023 14:19:49 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Martyna Szapar-Mudlaw <martyna.szapar-mudlaw@...ux.intel.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Marcin Szycik <marcin.szycik@...ux.intel.com>,
        Amritha Nambiar <amritha.nambiar@...el.com>,
        Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>,
        Wojciech Drewek <wojciech.drewek@...el.com>,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] 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 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 <<
      |     ^~~~~~~~~~~

The code looks correct to me, so just avoid the warning by replacing
the macro expansion with an intermediate variable.

Fixes: 34800178b302 ("ice: Add support for VLAN priority filters in switchdev")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/net/ethernet/intel/ice/ice_tc_lib.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 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..e9932446185c 100644
--- a/drivers/net/ethernet/intel/ice/ice_tc_lib.c
+++ b/drivers/net/ethernet/intel/ice/ice_tc_lib.c
@@ -1453,10 +1453,9 @@ ice_parse_cls_flower(struct net_device *filter_dev, struct ice_vsi *vsi,
 		}
 
 		if (match.mask->vlan_priority) {
+			u16 prio = (match.key->vlan_priority << VLAN_PRIO_SHIFT) & VLAN_PRIO_MASK;
 			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);
+			headers->vlan_hdr.vlan_prio = cpu_to_be16(prio);
 		}
 
 		if (match.mask->vlan_tpid)
@@ -1487,10 +1486,9 @@ ice_parse_cls_flower(struct net_device *filter_dev, struct ice_vsi *vsi,
 		}
 
 		if (match.mask->vlan_priority) {
+			u16 prio = (match.key->vlan_priority << VLAN_PRIO_SHIFT) & VLAN_PRIO_MASK;
 			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);
+			headers->cvlan_hdr.vlan_prio = cpu_to_be16(prio);
 		}
 	}
 
-- 
2.39.1