From: Thierry Reding <thierry.reding@gmail.com>
To: "David S. Miller" <davem@davemloft.net>
Cc: Heiner Kallweit <hkallweit1@gmail.com>,
Andrew Lunn <andrew@lunn.ch>,
Realtek linux nic maintainers <nic_swsd@realtek.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 2/2] r8169: Avoid pointer aliasing
Date: Mon, 4 Feb 2019 17:42:13 +0100 [thread overview]
Message-ID: <20190204164213.30727-2-thierry.reding@gmail.com> (raw)
In-Reply-To: <20190204164213.30727-1-thierry.reding@gmail.com>
From: Thierry Reding <treding@nvidia.com>
Read MAC address 32-bit at a time and manually extract the individual
bytes. This avoids pointer aliasing and gives the compiler a better
chance of optimizing the operation.
Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Thierry Reding <treding@nvidia.com>
---
Applies to net-next.
I tested this on a Jetson TX2 with an add-in Realtek ethernet card that
has a properly programmed OTP to verify that I got the endianess right.
Seems like everything works and the device behaves the same with or
without this patch.
drivers/net/ethernet/realtek/r8169.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index 501891be7c56..192fbb36bc9f 100644
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -7113,12 +7113,21 @@ static int rtl_alloc_irq(struct rtl8169_private *tp)
static void rtl_read_mac_address(struct rtl8169_private *tp,
u8 mac_addr[ETH_ALEN])
{
+ u32 value;
+
/* Get MAC address */
switch (tp->mac_version) {
case RTL_GIGA_MAC_VER_35 ... RTL_GIGA_MAC_VER_38:
case RTL_GIGA_MAC_VER_40 ... RTL_GIGA_MAC_VER_51:
- *(u32 *)&mac_addr[0] = rtl_eri_read(tp, 0xe0, ERIAR_EXGMAC);
- *(u16 *)&mac_addr[4] = rtl_eri_read(tp, 0xe4, ERIAR_EXGMAC);
+ value = rtl_eri_read(tp, 0xe0, ERIAR_EXGMAC);
+ mac_addr[0] = (value >> 0) & 0xff;
+ mac_addr[1] = (value >> 8) & 0xff;
+ mac_addr[2] = (value >> 16) & 0xff;
+ mac_addr[3] = (value >> 24) & 0xff;
+
+ value = rtl_eri_read(tp, 0xe4, ERIAR_EXGMAC);
+ mac_addr[4] = (value >> 0) & 0xff;
+ mac_addr[5] = (value >> 8) & 0xff;
break;
default:
break;
@@ -7316,7 +7325,7 @@ static int rtl_get_ether_clk(struct rtl8169_private *tp)
static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
{
const struct rtl_cfg_info *cfg = rtl_cfg_infos + ent->driver_data;
- u8 mac_addr[ETH_ALEN] __aligned(4) = {};
+ u8 mac_addr[ETH_ALEN] = {};
struct rtl8169_private *tp;
struct net_device *dev;
int chipset, region, i;
--
2.19.1
next prev parent reply other threads:[~2019-02-04 16:42 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-04 16:42 [PATCH v2 1/2] r8169: Load MAC address from device tree if present Thierry Reding
2019-02-04 16:42 ` Thierry Reding [this message]
2019-02-04 16:59 ` [PATCH v2 2/2] r8169: Avoid pointer aliasing Andrew Lunn
2019-02-04 18:44 ` Heiner Kallweit
2019-02-05 3:20 ` David Miller
2019-02-05 18:42 ` Joe Perches
2019-02-05 19:14 ` David Miller
2019-02-05 19:19 ` Joe Perches
2019-02-06 7:25 ` Michal Kubecek
2019-02-05 20:04 ` Eric Dumazet
2019-02-05 20:18 ` Joe Perches
2019-02-05 20:23 ` Eric Dumazet
2019-02-05 20:23 ` Heiner Kallweit
2019-02-04 19:30 ` [PATCH v2 1/2] r8169: Load MAC address from device tree if present Heiner Kallweit
2019-02-06 2:27 [PATCH v2 2/2] r8169: Avoid pointer aliasing Paul Zimmerman
2019-02-06 2:52 ` Joe Perches
2019-02-06 3:25 ` Paul Zimmerman
2019-02-06 3:49 ` Joe Perches
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