x86 bpf_jit: support MOD operation

commit b6069a9570 (filter: add MOD operation) added generic
support for modulus operation in BPF.

This patch brings JIT support for x86_64

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: George Bakos <gbakos@alpinista.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 25 insertions, 0 deletions

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 33643a8bcbbb..106c57829120 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -280,6 +280,31 @@ void bpf_jit_compile(struct sk_filter *fp)
                                 }
                                 EMIT4(0x31, 0xd2, 0xf7, 0xf3); /* xor %edx,%edx; div %ebx */
                                 break;
+                        case BPF_S_ALU_MOD_X: /* A %= X; */
+                                seen |= SEEN_XREG;
+                                EMIT2(0x85, 0xdb);      /* test %ebx,%ebx */
+                                if (pc_ret0 > 0) {
+                                        /* addrs[pc_ret0 - 1] is start address of target
+                                         * (addrs[i] - 6) is the address following this jmp
+                                         * ("xor %edx,%edx; div %ebx;mov %edx,%eax" being 6 bytes long)
+                                         */
+                                        EMIT_COND_JMP(X86_JE, addrs[pc_ret0 - 1] -
+                                                                (addrs[i] - 6));
+                                } else {
+                                        EMIT_COND_JMP(X86_JNE, 2 + 5);
+                                        CLEAR_A();
+                                        EMIT1_off32(0xe9, cleanup_addr - (addrs[i] - 6)); /* jmp .+off32 */
+                                }
+                                EMIT2(0x31, 0xd2);      /* xor %edx,%edx */
+                                EMIT2(0xf7, 0xf3);      /* div %ebx */
+                                EMIT2(0x89, 0xd0);      /* mov %edx,%eax */
+                                break;
+                        case BPF_S_ALU_MOD_K: /* A %= K; */
+                                EMIT2(0x31, 0xd2);      /* xor %edx,%edx */
+                                EMIT1(0xb9);EMIT(K, 4); /* mov imm32,%ecx */
+                                EMIT2(0xf7, 0xf1);      /* div %ecx */
+                                EMIT2(0x89, 0xd0);      /* mov %edx,%eax */
+                                break;
                         case BPF_S_ALU_DIV_K: /* A = reciprocal_divide(A, K); */
                                 EMIT3(0x48, 0x69, 0xc0); /* imul imm32,%rax,%rax */
                                 EMIT(K, 4);