ether_addr_equal: Optimize implementation, remove unused compare_ether_addr
Add a new check for CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS to reduce the number of or's used in the ether_addr_equal comparison to very slightly improve function performance. Simplify the ether_addr_equal_64bits implementation. Integrate and remove the zap_last_2bytes helper as it's now used only once. Remove the now unused compare_ether_addr function. Update the unaligned-memory-access documentation to remove the compare_ether_addr description and show how unaligned accesses could occur with ether_addr_equal. Signed-off-by: Joe Perches <joe@perches.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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committed by
David S. Miller

parent
5cc208becb
commit
0d74c42f78
@@ -26,6 +26,7 @@
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#include <linux/netdevice.h>
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#include <linux/random.h>
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#include <asm/unaligned.h>
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#include <asm/bitsperlong.h>
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#ifdef __KERNEL__
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__be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev);
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@@ -210,41 +211,27 @@ static inline void eth_hw_addr_inherit(struct net_device *dst,
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memcpy(dst->dev_addr, src->dev_addr, ETH_ALEN);
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}
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/**
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* compare_ether_addr - Compare two Ethernet addresses
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* @addr1: Pointer to a six-byte array containing the Ethernet address
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* @addr2: Pointer other six-byte array containing the Ethernet address
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*
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* Compare two Ethernet addresses, returns 0 if equal, non-zero otherwise.
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* Unlike memcmp(), it doesn't return a value suitable for sorting.
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*/
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static inline unsigned compare_ether_addr(const u8 *addr1, const u8 *addr2)
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{
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const u16 *a = (const u16 *) addr1;
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const u16 *b = (const u16 *) addr2;
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BUILD_BUG_ON(ETH_ALEN != 6);
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return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | (a[2] ^ b[2])) != 0;
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}
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/**
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* ether_addr_equal - Compare two Ethernet addresses
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* @addr1: Pointer to a six-byte array containing the Ethernet address
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* @addr2: Pointer other six-byte array containing the Ethernet address
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*
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* Compare two Ethernet addresses, returns true if equal
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*
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* Please note: addr1 & addr2 must both be aligned to u16.
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*/
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static inline bool ether_addr_equal(const u8 *addr1, const u8 *addr2)
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{
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return !compare_ether_addr(addr1, addr2);
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}
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#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
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u32 fold = ((*(const u32 *)addr1) ^ (*(const u32 *)addr2)) |
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((*(const u16 *)(addr1 + 4)) ^ (*(const u16 *)(addr2 + 4)));
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static inline unsigned long zap_last_2bytes(unsigned long value)
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{
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#ifdef __BIG_ENDIAN
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return value >> 16;
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return fold == 0;
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#else
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return value << 16;
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const u16 *a = (const u16 *)addr1;
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const u16 *b = (const u16 *)addr2;
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return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | (a[2] ^ b[2])) == 0;
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#endif
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}
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@@ -265,16 +252,14 @@ static inline unsigned long zap_last_2bytes(unsigned long value)
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static inline bool ether_addr_equal_64bits(const u8 addr1[6+2],
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const u8 addr2[6+2])
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{
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#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
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unsigned long fold = ((*(unsigned long *)addr1) ^
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(*(unsigned long *)addr2));
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#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
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u64 fold = (*(const u64 *)addr1) ^ (*(const u64 *)addr2);
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if (sizeof(fold) == 8)
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return zap_last_2bytes(fold) == 0;
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fold |= zap_last_2bytes((*(unsigned long *)(addr1 + 4)) ^
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(*(unsigned long *)(addr2 + 4)));
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return fold == 0;
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#ifdef __BIG_ENDIAN
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return (fold >> 16) == 0;
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#else
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return (fold << 16) == 0;
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#endif
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#else
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return ether_addr_equal(addr1, addr2);
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#endif
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