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>

diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index 501891be7c56c66856e1242ebe4b7e4c7bfa2429..1dd72137fd53710294d5d44be78859b7d6d9f04a 100644 (file)
--- 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;