bpf: do not use reciprocal divide

[~andy/linux] / arch / x86 / net / bpf_jit_comp.c

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 26328e800869fc6ac1821c0ab3dcd2baa1506ec1..4ed75dd81d052ff96cc832702d174ad4d63bffec 100644 (file)
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -359,15 +359,21 @@ void bpf_jit_compile(struct sk_filter *fp)
                                EMIT2(0x89, 0xd0);      /* mov %edx,%eax */
                                break;
                        case BPF_S_ALU_MOD_K: /* A %= K; */
+                               if (K == 1) {
+                                       CLEAR_A();
+                                       break;
+                               }
                                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);
-                               EMIT4(0x48, 0xc1, 0xe8, 0x20); /* shr $0x20,%rax */
+                       case BPF_S_ALU_DIV_K: /* A /= K */
+                               if (K == 1)
+                                       break;
+                               EMIT2(0x31, 0xd2);      /* xor %edx,%edx */
+                               EMIT1(0xb9);EMIT(K, 4); /* mov imm32,%ecx */
+                               EMIT2(0xf7, 0xf1);      /* div %ecx */
                                break;
                        case BPF_S_ALU_AND_X:
                                seen |= SEEN_XREG;