r8169: Avoid pointer aliasing

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>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 3 deletions

diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index 501891be7c56..1dd72137fd53 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 +7325,8 @@ 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) = {};
+        /* align to u16 for is_valid_ether_addr() */
+        u8 mac_addr[ETH_ALEN] __aligned(2) = {};
         struct rtl8169_private *tp;
         struct net_device *dev;
         int chipset, region, i;