Re: [PATCH net-next v2 0/6] slight optimization of addr compare for some modules

[Joe Perches <joe@perches.com>]

On Mon, 2013-12-16 at 22:53 +0800, Ding Tianhong wrote:
> 于 2013/12/16 22:45, Joe Perches 写道:
> > Are you intending to do more of these?
> > 
> > $ git grep -E "\bmemcmp\s*\([^,]*,[^,]*,\s*(ETH_ALEN|6)\s*\)" * | wc -l
> > 299
> > 
> > Perhaps the majority of these should use ether_addr_equal
> > or ether_addr_equal_unaligned.
>
> yes, it is a juge work to review the whole places and I think it should be
> finished by several times, maybe start from this patchset.

coccinelle (aka: spatch) can help find and change these

$ cat ether_addr_equal_unaligned.cocci
@@
expression e1;
expression e2;
@@

-	!memcmp(e1, e2, 6)
+	ether_addr_equal_unaligned(e1, e2)

@@
expression e1;
expression e2;
@@

-	memcmp(e1, e2, 6) == 0
+	ether_addr_equal_unaligned(e1, e2)

@@
expression e1;
expression e2;
@@

-	memcmp(e1, e2, 6)
+	!ether_addr_equal_unaligned(e1, e2)

@@
expression e1;
expression e2;
@@

-	memcmp(e1, e2, 6) != 0
+	!ether_addr_equal_unaligned(e1, e2)

$ spatch -sp-file ether_addr_equal.cocci drivers/media/dvb-core/dvb_net.c
init_defs_builtins: /usr/local/share/coccinelle/standard.h
HANDLING: drivers/media/dvb-core/dvb_net.c
diff = 
--- drivers/media/dvb-core/dvb_net.c
+++ /tmp/cocci-output-18744-96d16c-dvb_net.c
@@ -837,7 +837,8 @@ static void dvb_net_sec(struct net_devic
 	}
 	if (pkt[5] & 0x02) {
 		/* handle LLC/SNAP, see rfc-1042 */
-		if (pkt_len < 24 || memcmp(&pkt[12], "\xaa\xaa\x03\0\0\0", 6)) {
+		if (pkt_len < 24 || !ether_addr_equal_unaligned(&pkt[12],
+								"\xaa\xaa\x03\0\0\0")) {
 			stats->rx_dropped++;
 			return;
 		}

I presume many of these should be ether_addr_equal
and not ether_addr_equal_unaligned, but I can't
think of a way to automate that easily.