filter: add MOD operation
Add a new ALU opcode, to compute a modulus.
Commit ffe06c17afbbb used an ancillary to implement XOR_X,
but here we reserve one of the available ALU opcode to implement both
MOD_X and MOD_K
Signed-off-by: Eric Dumazet <edumazet@google.com>
Suggested-by: George Bakos <gbakos@alpinista.org>
Cc: Jay Schulist <jschlst@samba.org>
Cc: Jiri Pirko <jpirko@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 82b0135..3cf5fd5 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -74,6 +74,8 @@
#define BPF_LSH 0x60
#define BPF_RSH 0x70
#define BPF_NEG 0x80
+#define BPF_MOD 0x90
+
#define BPF_JA 0x00
#define BPF_JEQ 0x10
#define BPF_JGT 0x20
@@ -196,6 +198,8 @@
BPF_S_ALU_MUL_K,
BPF_S_ALU_MUL_X,
BPF_S_ALU_DIV_X,
+ BPF_S_ALU_MOD_K,
+ BPF_S_ALU_MOD_X,
BPF_S_ALU_AND_K,
BPF_S_ALU_AND_X,
BPF_S_ALU_OR_K,
diff --git a/net/core/filter.c b/net/core/filter.c
index 907efd2..fbe3a8d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -167,6 +167,14 @@
case BPF_S_ALU_DIV_K:
A = reciprocal_divide(A, K);
continue;
+ case BPF_S_ALU_MOD_X:
+ if (X == 0)
+ return 0;
+ A %= X;
+ continue;
+ case BPF_S_ALU_MOD_K:
+ A %= K;
+ continue;
case BPF_S_ALU_AND_X:
A &= X;
continue;
@@ -469,6 +477,8 @@
[BPF_ALU|BPF_MUL|BPF_K] = BPF_S_ALU_MUL_K,
[BPF_ALU|BPF_MUL|BPF_X] = BPF_S_ALU_MUL_X,
[BPF_ALU|BPF_DIV|BPF_X] = BPF_S_ALU_DIV_X,
+ [BPF_ALU|BPF_MOD|BPF_K] = BPF_S_ALU_MOD_K,
+ [BPF_ALU|BPF_MOD|BPF_X] = BPF_S_ALU_MOD_X,
[BPF_ALU|BPF_AND|BPF_K] = BPF_S_ALU_AND_K,
[BPF_ALU|BPF_AND|BPF_X] = BPF_S_ALU_AND_X,
[BPF_ALU|BPF_OR|BPF_K] = BPF_S_ALU_OR_K,
@@ -531,6 +541,11 @@
return -EINVAL;
ftest->k = reciprocal_value(ftest->k);
break;
+ case BPF_S_ALU_MOD_K:
+ /* check for division by zero */
+ if (ftest->k == 0)
+ return -EINVAL;
+ break;
case BPF_S_LD_MEM:
case BPF_S_LDX_MEM:
case BPF_S_ST: