filter: add XOR instruction for use with X/K

SKF_AD_ALU_XOR_X has been added a while ago, but as an 'ancillary'
operation that is invoked through a negative offset in K within BPF
load operations. Since BPF_MOD has recently been added, BPF_XOR should
also be part of the common ALU operations. Removing SKF_AD_ALU_XOR_X
might not be an option since this is exposed to user space.

Signed-off-by: Daniel Borkmann <daniel.borkmann@tik.ee.ethz.ch>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/filter.h

@@ -75,6 +75,7 @@ struct sock_fprog {	/* Required for SO_ATTACH_FILTER. */
 #define         BPF_RSH         0x70
 #define         BPF_NEG         0x80
 #define		BPF_MOD		0x90
+#define		BPF_XOR		0xa0
 
 #define         BPF_JA          0x00
 #define         BPF_JEQ         0x10
@@ -204,6 +205,8 @@ enum {
 	BPF_S_ALU_AND_X,
 	BPF_S_ALU_OR_K,
 	BPF_S_ALU_OR_X,
+	BPF_S_ALU_XOR_K,
+	BPF_S_ALU_XOR_X,
 	BPF_S_ALU_LSH_K,
 	BPF_S_ALU_LSH_X,
 	BPF_S_ALU_RSH_K,

net/core/filter.c

@@ -187,6 +187,13 @@ unsigned int sk_run_filter(const struct sk_buff *skb,
 		case BPF_S_ALU_OR_K:
 			A |= K;
 			continue;
+		case BPF_S_ANC_ALU_XOR_X:
+		case BPF_S_ALU_XOR_X:
+			A ^= X;
+			continue;
+		case BPF_S_ALU_XOR_K:
+			A ^= K;
+			continue;
 		case BPF_S_ALU_LSH_X:
 			A <<= X;
 			continue;
@@ -334,9 +341,6 @@ unsigned int sk_run_filter(const struct sk_buff *skb,
 		case BPF_S_ANC_CPU:
 			A = raw_smp_processor_id();
 			continue;
-		case BPF_S_ANC_ALU_XOR_X:
-			A ^= X;
-			continue;
 		case BPF_S_ANC_NLATTR: {
 			struct nlattr *nla;
 
@@ -483,6 +487,8 @@ int sk_chk_filter(struct sock_filter *filter, unsigned int flen)
 		[BPF_ALU|BPF_AND|BPF_X]  = BPF_S_ALU_AND_X,
 		[BPF_ALU|BPF_OR|BPF_K]   = BPF_S_ALU_OR_K,
 		[BPF_ALU|BPF_OR|BPF_X]   = BPF_S_ALU_OR_X,
+		[BPF_ALU|BPF_XOR|BPF_K]  = BPF_S_ALU_XOR_K,
+		[BPF_ALU|BPF_XOR|BPF_X]  = BPF_S_ALU_XOR_X,
 		[BPF_ALU|BPF_LSH|BPF_K]  = BPF_S_ALU_LSH_K,
 		[BPF_ALU|BPF_LSH|BPF_X]  = BPF_S_ALU_LSH_X,
 		[BPF_ALU|BPF_RSH|BPF_K]  = BPF_S_ALU_RSH_K,