arch/x86/net/bpf_jit_comp.c - kernel/msm-4.19 - Gitiles

 /* bpf_jit_comp.c : BPF JIT compiler
  *
  * Copyright (C) 2011 Eric Dumazet (eric.dumazet@gmail.com)
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; version 2
  * of the License.
  */
 #include <linux/moduleloader.h>
 #include <asm/cacheflush.h>
 #include <linux/netdevice.h>
 #include <linux/filter.h>
 #include <linux/if_vlan.h>

 /*
  * Conventions :
  *  EAX : BPF A accumulator
  *  EBX : BPF X accumulator
  *  RDI : pointer to skb   (first argument given to JIT function)
  *  RBP : frame pointer (even if CONFIG_FRAME_POINTER=n)
  *  ECX,EDX,ESI : scratch registers
  *  r9d : skb->len - skb->data_len (headlen)
  *  r8  : skb->data
  * -8(RBP) : saved RBX value
  * -16(RBP)..-80(RBP) : BPF_MEMWORDS values
  */
 int bpf_jit_enable __read_mostly;

 /*
  * assembly code in arch/x86/net/bpf_jit.S
  */
 extern u8 sk_load_word[], sk_load_half[], sk_load_byte[], sk_load_byte_msh[];
 extern u8 sk_load_word_positive_offset[], sk_load_half_positive_offset[];
 extern u8 sk_load_byte_positive_offset[], sk_load_byte_msh_positive_offset[];
 extern u8 sk_load_word_negative_offset[], sk_load_half_negative_offset[];
 extern u8 sk_load_byte_negative_offset[], sk_load_byte_msh_negative_offset[];

 static inline u8 *emit_code(u8 *ptr, u32 bytes, unsigned int len)
 {
 	if (len == 1)
 		*ptr = bytes;
 	else if (len == 2)
 		*(u16 *)ptr = bytes;
 	else {
 		*(u32 *)ptr = bytes;
 		barrier();
 	}
 	return ptr + len;
 }

 #define EMIT(bytes, len)	do { prog = emit_code(prog, bytes, len); } while (0)

 #define EMIT1(b1)		EMIT(b1, 1)
 #define EMIT2(b1, b2)		EMIT((b1) + ((b2) << 8), 2)
 #define EMIT3(b1, b2, b3)	EMIT((b1) + ((b2) << 8) + ((b3) << 16), 3)
 #define EMIT4(b1, b2, b3, b4)   EMIT((b1) + ((b2) << 8) + ((b3) << 16) + ((b4) << 24), 4)
 #define EMIT1_off32(b1, off)	do { EMIT1(b1); EMIT(off, 4);} while (0)

 #define CLEAR_A() EMIT2(0x31, 0xc0) /* xor %eax,%eax */
 #define CLEAR_X() EMIT2(0x31, 0xdb) /* xor %ebx,%ebx */

 static inline bool is_imm8(int value)
 {
 	return value <= 127 && value >= -128;
 }

 static inline bool is_near(int offset)
 {
 	return offset <= 127 && offset >= -128;
 }

 #define EMIT_JMP(offset)						\
 do {									\
 	if (offset) {							\
 		if (is_near(offset))					\
 			EMIT2(0xeb, offset); /* jmp .+off8 */		\
 		else							\
 			EMIT1_off32(0xe9, offset); /* jmp .+off32 */	\
 	}								\
 } while (0)

 /* list of x86 cond jumps opcodes (. + s8)
  * Add 0x10 (and an extra 0x0f) to generate far jumps (. + s32)
  */
 #define X86_JB  0x72
 #define X86_JAE 0x73
 #define X86_JE  0x74
 #define X86_JNE 0x75
 #define X86_JBE 0x76
 #define X86_JA  0x77

 #define EMIT_COND_JMP(op, offset)				\
 do {								\
 	if (is_near(offset))					\
 		EMIT2(op, offset); /* jxx .+off8 */		\
 	else {							\
 		EMIT2(0x0f, op + 0x10);				\
 		EMIT(offset, 4); /* jxx .+off32 */		\
 	}							\
 } while (0)

 #define COND_SEL(CODE, TOP, FOP)	\
 	case CODE:			\
 		t_op = TOP;		\
 		f_op = FOP;		\
 		goto cond_branch


 #define SEEN_DATAREF 1 /* might call external helpers */
 #define SEEN_XREG    2 /* ebx is used */
 #define SEEN_MEM     4 /* use mem[] for temporary storage */

 static inline void bpf_flush_icache(void *start, void *end)
 {
 	mm_segment_t old_fs = get_fs();

 	set_fs(KERNEL_DS);
 	smp_wmb();
 	flush_icache_range((unsigned long)start, (unsigned long)end);
 	set_fs(old_fs);
 }

 #define CHOOSE_LOAD_FUNC(K, func) \
 	((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)

 void bpf_jit_compile(struct sk_filter *fp)
 {
 	u8 temp[64];
 	u8 *prog;
 	unsigned int proglen, oldproglen = 0;
 	int ilen, i;
 	int t_offset, f_offset;
 	u8 t_op, f_op, seen = 0, pass;
 	u8 *image = NULL;
 	u8 *func;
 	int pc_ret0 = -1; /* bpf index of first RET #0 instruction (if any) */
 	unsigned int cleanup_addr; /* epilogue code offset */
 	unsigned int *addrs;
 	const struct sock_filter *filter = fp->insns;
 	int flen = fp->len;

 	if (!bpf_jit_enable)
 		return;

 	addrs = kmalloc(flen * sizeof(*addrs), GFP_KERNEL);
 	if (addrs == NULL)
 		return;

 	/* Before first pass, make a rough estimation of addrs[]
 	 * each bpf instruction is translated to less than 64 bytes
 	 */
 	for (proglen = 0, i = 0; i < flen; i++) {
 		proglen += 64;
 		addrs[i] = proglen;
 	}
 	cleanup_addr = proglen; /* epilogue address */

 	for (pass = 0; pass < 10; pass++) {
 		u8 seen_or_pass0 = (pass == 0) ? (SEEN_XREG | SEEN_DATAREF | SEEN_MEM) : seen;
 		/* no prologue/epilogue for trivial filters (RET something) */
 		proglen = 0;
 		prog = temp;

 		if (seen_or_pass0) {
 			EMIT4(0x55, 0x48, 0x89, 0xe5); /* push %rbp; mov %rsp,%rbp */
 			EMIT4(0x48, 0x83, 0xec, 96);	/* subq  $96,%rsp	*/
 			/* note : must save %rbx in case bpf_error is hit */
 			if (seen_or_pass0 & (SEEN_XREG | SEEN_DATAREF))
 				EMIT4(0x48, 0x89, 0x5d, 0xf8); /* mov %rbx, -8(%rbp) */
 			if (seen_or_pass0 & SEEN_XREG)
 				CLEAR_X(); /* make sure we dont leek kernel memory */

 			/*
 			 * If this filter needs to access skb data,
 			 * loads r9 and r8 with :
 			 *  r9 = skb->len - skb->data_len
 			 *  r8 = skb->data
 			 */
 			if (seen_or_pass0 & SEEN_DATAREF) {
 				if (offsetof(struct sk_buff, len) <= 127)
 					/* mov    off8(%rdi),%r9d */
 					EMIT4(0x44, 0x8b, 0x4f, offsetof(struct sk_buff, len));
 				else {
 					/* mov    off32(%rdi),%r9d */
 					EMIT3(0x44, 0x8b, 0x8f);
 					EMIT(offsetof(struct sk_buff, len), 4);
 				}
 				if (is_imm8(offsetof(struct sk_buff, data_len)))
 					/* sub    off8(%rdi),%r9d */
 					EMIT4(0x44, 0x2b, 0x4f, offsetof(struct sk_buff, data_len));
 				else {
 					EMIT3(0x44, 0x2b, 0x8f);
 					EMIT(offsetof(struct sk_buff, data_len), 4);
 				}

 				if (is_imm8(offsetof(struct sk_buff, data)))
 					/* mov off8(%rdi),%r8 */
 					EMIT4(0x4c, 0x8b, 0x47, offsetof(struct sk_buff, data));
 				else {
 					/* mov off32(%rdi),%r8 */
 					EMIT3(0x4c, 0x8b, 0x87);
 					EMIT(offsetof(struct sk_buff, data), 4);
 				}
 			}
 		}

 		switch (filter[0].code) {
 		case BPF_S_RET_K:
 		case BPF_S_LD_W_LEN:
 		case BPF_S_ANC_PROTOCOL:
 		case BPF_S_ANC_IFINDEX:
 		case BPF_S_ANC_MARK:
 		case BPF_S_ANC_RXHASH:
 		case BPF_S_ANC_CPU:
 		case BPF_S_ANC_VLAN_TAG:
 		case BPF_S_ANC_VLAN_TAG_PRESENT:
 		case BPF_S_ANC_QUEUE:
 		case BPF_S_LD_W_ABS:
 		case BPF_S_LD_H_ABS:
 		case BPF_S_LD_B_ABS:
 			/* first instruction sets A register (or is RET 'constant') */
 			break;
 		default:
 			/* make sure we dont leak kernel information to user */
 			CLEAR_A(); /* A = 0 */
 		}

 		for (i = 0; i < flen; i++) {
 			unsigned int K = filter[i].k;

 			switch (filter[i].code) {
 			case BPF_S_ALU_ADD_X: /* A += X; */
 				seen |= SEEN_XREG;
 				EMIT2(0x01, 0xd8);		/* add %ebx,%eax */
 				break;
 			case BPF_S_ALU_ADD_K: /* A += K; */
 				if (!K)
 					break;
 				if (is_imm8(K))
 					EMIT3(0x83, 0xc0, K);	/* add imm8,%eax */
 				else
 					EMIT1_off32(0x05, K);	/* add imm32,%eax */
 				break;
 			case BPF_S_ALU_SUB_X: /* A -= X; */
 				seen |= SEEN_XREG;
 				EMIT2(0x29, 0xd8);		/* sub    %ebx,%eax */
 				break;
 			case BPF_S_ALU_SUB_K: /* A -= K */
 				if (!K)
 					break;
 				if (is_imm8(K))
 					EMIT3(0x83, 0xe8, K); /* sub imm8,%eax */
 				else
 					EMIT1_off32(0x2d, K); /* sub imm32,%eax */
 				break;
 			case BPF_S_ALU_MUL_X: /* A *= X; */
 				seen |= SEEN_XREG;
 				EMIT3(0x0f, 0xaf, 0xc3);	/* imul %ebx,%eax */
 				break;
 			case BPF_S_ALU_MUL_K: /* A *= K */
 				if (is_imm8(K))
 					EMIT3(0x6b, 0xc0, K); /* imul imm8,%eax,%eax */
 				else {
 					EMIT2(0x69, 0xc0);		/* imul imm32,%eax */
 					EMIT(K, 4);
 				}
 				break;
 			case BPF_S_ALU_DIV_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] - 4) is the address following this jmp
 					 * ("xor %edx,%edx; div %ebx" being 4 bytes long)
 					 */
 					EMIT_COND_JMP(X86_JE, addrs[pc_ret0 - 1] -
 								(addrs[i] - 4));
 				} else {
 					EMIT_COND_JMP(X86_JNE, 2 + 5);
 					CLEAR_A();
 					EMIT1_off32(0xe9, cleanup_addr - (addrs[i] - 4)); /* jmp .+off32 */
 				}
 				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);
 				EMIT4(0x48, 0xc1, 0xe8, 0x20); /* shr $0x20,%rax */
 				break;
 			case BPF_S_ALU_AND_X:
 				seen |= SEEN_XREG;
 				EMIT2(0x21, 0xd8);		/* and %ebx,%eax */
 				break;
 			case BPF_S_ALU_AND_K:
 				if (K >= 0xFFFFFF00) {
 					EMIT2(0x24, K & 0xFF); /* and imm8,%al */
 				} else if (K >= 0xFFFF0000) {
 					EMIT2(0x66, 0x25);	/* and imm16,%ax */
 					EMIT(K, 2);
 				} else {
 					EMIT1_off32(0x25, K);	/* and imm32,%eax */
 				}
 				break;
 			case BPF_S_ALU_OR_X:
 				seen |= SEEN_XREG;
 				EMIT2(0x09, 0xd8);		/* or %ebx,%eax */
 				break;
 			case BPF_S_ALU_OR_K:
 				if (is_imm8(K))
 					EMIT3(0x83, 0xc8, K); /* or imm8,%eax */
 				else
 					EMIT1_off32(0x0d, K);	/* or imm32,%eax */
 				break;
 			case BPF_S_ANC_ALU_XOR_X: /* A ^= X; */
 			case BPF_S_ALU_XOR_X:
 				seen |= SEEN_XREG;
 				EMIT2(0x31, 0xd8);		/* xor %ebx,%eax */
 				break;
 			case BPF_S_ALU_XOR_K: /* A ^= K; */
 				if (K == 0)
 					break;
 				if (is_imm8(K))
 					EMIT3(0x83, 0xf0, K);	/* xor imm8,%eax */
 				else
 					EMIT1_off32(0x35, K);	/* xor imm32,%eax */
 				break;
 			case BPF_S_ALU_LSH_X: /* A <<= X; */
 				seen |= SEEN_XREG;
 				EMIT4(0x89, 0xd9, 0xd3, 0xe0);	/* mov %ebx,%ecx; shl %cl,%eax */
 				break;
 			case BPF_S_ALU_LSH_K:
 				if (K == 0)
 					break;
 				else if (K == 1)
 					EMIT2(0xd1, 0xe0); /* shl %eax */
 				else
 					EMIT3(0xc1, 0xe0, K);
 				break;
 			case BPF_S_ALU_RSH_X: /* A >>= X; */
 				seen |= SEEN_XREG;
 				EMIT4(0x89, 0xd9, 0xd3, 0xe8);	/* mov %ebx,%ecx; shr %cl,%eax */
 				break;
 			case BPF_S_ALU_RSH_K: /* A >>= K; */
 				if (K == 0)
 					break;
 				else if (K == 1)
 					EMIT2(0xd1, 0xe8); /* shr %eax */
 				else
 					EMIT3(0xc1, 0xe8, K);
 				break;
 			case BPF_S_ALU_NEG:
 				EMIT2(0xf7, 0xd8);		/* neg %eax */
 				break;
 			case BPF_S_RET_K:
 				if (!K) {
 					if (pc_ret0 == -1)
 						pc_ret0 = i;
 					CLEAR_A();
 				} else {
 					EMIT1_off32(0xb8, K);	/* mov $imm32,%eax */
 				}
 				/* fallinto */
 			case BPF_S_RET_A:
 				if (seen_or_pass0) {
 					if (i != flen - 1) {
 						EMIT_JMP(cleanup_addr - addrs[i]);
 						break;
 					}
 					if (seen_or_pass0 & SEEN_XREG)
 						EMIT4(0x48, 0x8b, 0x5d, 0xf8);  /* mov  -8(%rbp),%rbx */
 					EMIT1(0xc9);		/* leaveq */
 				}
 				EMIT1(0xc3);		/* ret */
 				break;
 			case BPF_S_MISC_TAX: /* X = A */
 				seen |= SEEN_XREG;
 				EMIT2(0x89, 0xc3);	/* mov    %eax,%ebx */
 				break;
 			case BPF_S_MISC_TXA: /* A = X */
 				seen |= SEEN_XREG;
 				EMIT2(0x89, 0xd8);	/* mov    %ebx,%eax */
 				break;
 			case BPF_S_LD_IMM: /* A = K */
 				if (!K)
 					CLEAR_A();
 				else
 					EMIT1_off32(0xb8, K); /* mov $imm32,%eax */
 				break;
 			case BPF_S_LDX_IMM: /* X = K */
 				seen |= SEEN_XREG;
 				if (!K)
 					CLEAR_X();
 				else
 					EMIT1_off32(0xbb, K); /* mov $imm32,%ebx */
 				break;
 			case BPF_S_LD_MEM: /* A = mem[K] : mov off8(%rbp),%eax */
 				seen |= SEEN_MEM;
 				EMIT3(0x8b, 0x45, 0xf0 - K*4);
 				break;
 			case BPF_S_LDX_MEM: /* X = mem[K] : mov off8(%rbp),%ebx */
 				seen |= SEEN_XREG | SEEN_MEM;
 				EMIT3(0x8b, 0x5d, 0xf0 - K*4);
 				break;
 			case BPF_S_ST: /* mem[K] = A : mov %eax,off8(%rbp) */
 				seen |= SEEN_MEM;
 				EMIT3(0x89, 0x45, 0xf0 - K*4);
 				break;
 			case BPF_S_STX: /* mem[K] = X : mov %ebx,off8(%rbp) */
 				seen |= SEEN_XREG | SEEN_MEM;
 				EMIT3(0x89, 0x5d, 0xf0 - K*4);
 				break;
 			case BPF_S_LD_W_LEN: /*	A = skb->len; */
 				BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
 				if (is_imm8(offsetof(struct sk_buff, len)))
 					/* mov    off8(%rdi),%eax */
 					EMIT3(0x8b, 0x47, offsetof(struct sk_buff, len));
 				else {
 					EMIT2(0x8b, 0x87);
 					EMIT(offsetof(struct sk_buff, len), 4);
 				}
 				break;
 			case BPF_S_LDX_W_LEN: /* X = skb->len; */
 				seen |= SEEN_XREG;
 				if (is_imm8(offsetof(struct sk_buff, len)))
 					/* mov off8(%rdi),%ebx */
 					EMIT3(0x8b, 0x5f, offsetof(struct sk_buff, len));
 				else {
 					EMIT2(0x8b, 0x9f);
 					EMIT(offsetof(struct sk_buff, len), 4);
 				}
 				break;
 			case BPF_S_ANC_PROTOCOL: /* A = ntohs(skb->protocol); */
 				BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);
 				if (is_imm8(offsetof(struct sk_buff, protocol))) {
 					/* movzwl off8(%rdi),%eax */
 					EMIT4(0x0f, 0xb7, 0x47, offsetof(struct sk_buff, protocol));
 				} else {
 					EMIT3(0x0f, 0xb7, 0x87); /* movzwl off32(%rdi),%eax */
 					EMIT(offsetof(struct sk_buff, protocol), 4);
 				}
 				EMIT2(0x86, 0xc4); /* ntohs() : xchg   %al,%ah */
 				break;
 			case BPF_S_ANC_IFINDEX:
 				if (is_imm8(offsetof(struct sk_buff, dev))) {
 					/* movq off8(%rdi),%rax */
 					EMIT4(0x48, 0x8b, 0x47, offsetof(struct sk_buff, dev));
 				} else {
 					EMIT3(0x48, 0x8b, 0x87); /* movq off32(%rdi),%rax */
 					EMIT(offsetof(struct sk_buff, dev), 4);
 				}
 				EMIT3(0x48, 0x85, 0xc0);	/* test %rax,%rax */
 				EMIT_COND_JMP(X86_JE, cleanup_addr - (addrs[i] - 6));
 				BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
 				EMIT2(0x8b, 0x80);	/* mov off32(%rax),%eax */
 				EMIT(offsetof(struct net_device, ifindex), 4);
 				break;
 			case BPF_S_ANC_MARK:
 				BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
 				if (is_imm8(offsetof(struct sk_buff, mark))) {
 					/* mov off8(%rdi),%eax */
 					EMIT3(0x8b, 0x47, offsetof(struct sk_buff, mark));
 				} else {
 					EMIT2(0x8b, 0x87);
 					EMIT(offsetof(struct sk_buff, mark), 4);
 				}
 				break;
 			case BPF_S_ANC_RXHASH:
 				BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, rxhash) != 4);
 				if (is_imm8(offsetof(struct sk_buff, rxhash))) {
 					/* mov off8(%rdi),%eax */
 					EMIT3(0x8b, 0x47, offsetof(struct sk_buff, rxhash));
 				} else {
 					EMIT2(0x8b, 0x87);
 					EMIT(offsetof(struct sk_buff, rxhash), 4);
 				}
 				break;
 			case BPF_S_ANC_QUEUE:
 				BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, queue_mapping) != 2);
 				if (is_imm8(offsetof(struct sk_buff, queue_mapping))) {
 					/* movzwl off8(%rdi),%eax */
 					EMIT4(0x0f, 0xb7, 0x47, offsetof(struct sk_buff, queue_mapping));
 				} else {
 					EMIT3(0x0f, 0xb7, 0x87); /* movzwl off32(%rdi),%eax */
 					EMIT(offsetof(struct sk_buff, queue_mapping), 4);
 				}
 				break;
 			case BPF_S_ANC_CPU:
 #ifdef CONFIG_SMP
 				EMIT4(0x65, 0x8b, 0x04, 0x25); /* mov %gs:off32,%eax */
 				EMIT((u32)(unsigned long)&cpu_number, 4); /* A = smp_processor_id(); */
 #else
 				CLEAR_A();
 #endif
 				break;
 			case BPF_S_ANC_VLAN_TAG:
 			case BPF_S_ANC_VLAN_TAG_PRESENT:
 				BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
 				if (is_imm8(offsetof(struct sk_buff, vlan_tci))) {
 					/* movzwl off8(%rdi),%eax */
 					EMIT4(0x0f, 0xb7, 0x47, offsetof(struct sk_buff, vlan_tci));
 				} else {
 					EMIT3(0x0f, 0xb7, 0x87); /* movzwl off32(%rdi),%eax */
 					EMIT(offsetof(struct sk_buff, vlan_tci), 4);
 				}
 				BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
 				if (filter[i].code == BPF_S_ANC_VLAN_TAG) {
 					EMIT3(0x80, 0xe4, 0xef); /* and    $0xef,%ah */
 				} else {
 					EMIT3(0xc1, 0xe8, 0x0c); /* shr    $0xc,%eax */
 					EMIT3(0x83, 0xe0, 0x01); /* and    $0x1,%eax */
 				}
 				break;
 			case BPF_S_LD_W_ABS:
 				func = CHOOSE_LOAD_FUNC(K, sk_load_word);
 common_load:			seen |= SEEN_DATAREF;
 				t_offset = func - (image + addrs[i]);
 				EMIT1_off32(0xbe, K); /* mov imm32,%esi */
 				EMIT1_off32(0xe8, t_offset); /* call */
 				break;
 			case BPF_S_LD_H_ABS:
 				func = CHOOSE_LOAD_FUNC(K, sk_load_half);
 				goto common_load;
 			case BPF_S_LD_B_ABS:
 				func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
 				goto common_load;
 			case BPF_S_LDX_B_MSH:
 				func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
 				seen |= SEEN_DATAREF | SEEN_XREG;
 				t_offset = func - (image + addrs[i]);
 				EMIT1_off32(0xbe, K);	/* mov imm32,%esi */
 				EMIT1_off32(0xe8, t_offset); /* call sk_load_byte_msh */
 				break;
 			case BPF_S_LD_W_IND:
 				func = sk_load_word;
 common_load_ind:		seen |= SEEN_DATAREF | SEEN_XREG;
 				t_offset = func - (image + addrs[i]);
 				if (K) {
 					if (is_imm8(K)) {
 						EMIT3(0x8d, 0x73, K); /* lea imm8(%rbx), %esi */
 					} else {
 						EMIT2(0x8d, 0xb3); /* lea imm32(%rbx),%esi */
 						EMIT(K, 4);
 					}
 				} else {
 					EMIT2(0x89,0xde); /* mov %ebx,%esi */
 				}
 				EMIT1_off32(0xe8, t_offset);	/* call sk_load_xxx_ind */
 				break;
 			case BPF_S_LD_H_IND:
 				func = sk_load_half;
 				goto common_load_ind;
 			case BPF_S_LD_B_IND:
 				func = sk_load_byte;
 				goto common_load_ind;
 			case BPF_S_JMP_JA:
 				t_offset = addrs[i + K] - addrs[i];
 				EMIT_JMP(t_offset);
 				break;
 			COND_SEL(BPF_S_JMP_JGT_K, X86_JA, X86_JBE);
 			COND_SEL(BPF_S_JMP_JGE_K, X86_JAE, X86_JB);
 			COND_SEL(BPF_S_JMP_JEQ_K, X86_JE, X86_JNE);
 			COND_SEL(BPF_S_JMP_JSET_K,X86_JNE, X86_JE);
 			COND_SEL(BPF_S_JMP_JGT_X, X86_JA, X86_JBE);
 			COND_SEL(BPF_S_JMP_JGE_X, X86_JAE, X86_JB);
 			COND_SEL(BPF_S_JMP_JEQ_X, X86_JE, X86_JNE);
 			COND_SEL(BPF_S_JMP_JSET_X,X86_JNE, X86_JE);

 cond_branch:			f_offset = addrs[i + filter[i].jf] - addrs[i];
 				t_offset = addrs[i + filter[i].jt] - addrs[i];

 				/* same targets, can avoid doing the test :) */
 				if (filter[i].jt == filter[i].jf) {
 					EMIT_JMP(t_offset);
 					break;
 				}

 				switch (filter[i].code) {
 				case BPF_S_JMP_JGT_X:
 				case BPF_S_JMP_JGE_X:
 				case BPF_S_JMP_JEQ_X:
 					seen |= SEEN_XREG;
 					EMIT2(0x39, 0xd8); /* cmp %ebx,%eax */
 					break;
 				case BPF_S_JMP_JSET_X:
 					seen |= SEEN_XREG;
 					EMIT2(0x85, 0xd8); /* test %ebx,%eax */
 					break;
 				case BPF_S_JMP_JEQ_K:
 					if (K == 0) {
 						EMIT2(0x85, 0xc0); /* test   %eax,%eax */
 						break;
 					}
 				case BPF_S_JMP_JGT_K:
 				case BPF_S_JMP_JGE_K:
 					if (K <= 127)
 						EMIT3(0x83, 0xf8, K); /* cmp imm8,%eax */
 					else
 						EMIT1_off32(0x3d, K); /* cmp imm32,%eax */
 					break;
 				case BPF_S_JMP_JSET_K:
 					if (K <= 0xFF)
 						EMIT2(0xa8, K); /* test imm8,%al */
 					else if (!(K & 0xFFFF00FF))
 						EMIT3(0xf6, 0xc4, K >> 8); /* test imm8,%ah */
 					else if (K <= 0xFFFF) {
 						EMIT2(0x66, 0xa9); /* test imm16,%ax */
 						EMIT(K, 2);
 					} else {
 						EMIT1_off32(0xa9, K); /* test imm32,%eax */
 					}
 					break;
 				}
 				if (filter[i].jt != 0) {
 					if (filter[i].jf && f_offset)
 						t_offset += is_near(f_offset) ? 2 : 5;
 					EMIT_COND_JMP(t_op, t_offset);
 					if (filter[i].jf)
 						EMIT_JMP(f_offset);
 					break;
 				}
 				EMIT_COND_JMP(f_op, f_offset);
 				break;
 			default:
 				/* hmm, too complex filter, give up with jit compiler */
 				goto out;
 			}
 			ilen = prog - temp;
 			if (image) {
 				if (unlikely(proglen + ilen > oldproglen)) {
 					pr_err("bpb_jit_compile fatal error\n");
 					kfree(addrs);
 					module_free(NULL, image);
 					return;
 				}
 				memcpy(image + proglen, temp, ilen);
 			}
 			proglen += ilen;
 			addrs[i] = proglen;
 			prog = temp;
 		}
 		/* last bpf instruction is always a RET :
 		 * use it to give the cleanup instruction(s) addr
 		 */
 		cleanup_addr = proglen - 1; /* ret */
 		if (seen_or_pass0)
 			cleanup_addr -= 1; /* leaveq */
 		if (seen_or_pass0 & SEEN_XREG)
 			cleanup_addr -= 4; /* mov  -8(%rbp),%rbx */

 		if (image) {
 			if (proglen != oldproglen)
 				pr_err("bpb_jit_compile proglen=%u != oldproglen=%u\n", proglen, oldproglen);
 			break;
 		}
 		if (proglen == oldproglen) {
 			image = module_alloc(max_t(unsigned int,
 						   proglen,
 						   sizeof(struct work_struct)));
 			if (!image)
 				goto out;
 		}
 		oldproglen = proglen;
 	}
 	if (bpf_jit_enable > 1)
 		pr_err("flen=%d proglen=%u pass=%d image=%p\n",
 		       flen, proglen, pass, image);

 	if (image) {
 		if (bpf_jit_enable > 1)
 			print_hex_dump(KERN_ERR, "JIT code: ", DUMP_PREFIX_ADDRESS,
 				       16, 1, image, proglen, false);

 		bpf_flush_icache(image, image + proglen);

 		fp->bpf_func = (void *)image;
 	}
 out:
 	kfree(addrs);
 	return;
 }

 static void jit_free_defer(struct work_struct *arg)
 {
 	module_free(NULL, arg);
 }

 /* run from softirq, we must use a work_struct to call
  * module_free() from process context
  */
 void bpf_jit_free(struct sk_filter *fp)
 {
 	if (fp->bpf_func != sk_run_filter) {
 		struct work_struct *work = (struct work_struct *)fp->bpf_func;

 		INIT_WORK(work, jit_free_defer);
 		schedule_work(work);
 	}
 }
	/* bpf_jit_comp.c : BPF JIT compiler
	*
	* Copyright (C) 2011 Eric Dumazet (eric.dumazet@gmail.com)
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* as published by the Free Software Foundation; version 2
	* of the License.
	*/
	#include <linux/moduleloader.h>
	#include <asm/cacheflush.h>
	#include <linux/netdevice.h>
	#include <linux/filter.h>
	#include <linux/if_vlan.h>

	/*
	* Conventions :
	* EAX : BPF A accumulator
	* EBX : BPF X accumulator
	* RDI : pointer to skb (first argument given to JIT function)
	* RBP : frame pointer (even if CONFIG_FRAME_POINTER=n)
	* ECX,EDX,ESI : scratch registers
	* r9d : skb->len - skb->data_len (headlen)
	* r8 : skb->data
	* -8(RBP) : saved RBX value
	* -16(RBP)..-80(RBP) : BPF_MEMWORDS values
	*/
	int bpf_jit_enable __read_mostly;

	/*
	* assembly code in arch/x86/net/bpf_jit.S
	*/
	extern u8 sk_load_word[], sk_load_half[], sk_load_byte[], sk_load_byte_msh[];
	extern u8 sk_load_word_positive_offset[], sk_load_half_positive_offset[];
	extern u8 sk_load_byte_positive_offset[], sk_load_byte_msh_positive_offset[];
	extern u8 sk_load_word_negative_offset[], sk_load_half_negative_offset[];
	extern u8 sk_load_byte_negative_offset[], sk_load_byte_msh_negative_offset[];

	static inline u8 emit_code(u8 ptr, u32 bytes, unsigned int len)
	{
	if (len == 1)
	*ptr = bytes;
	else if (len == 2)
	(u16 )ptr = bytes;
	else {
	(u32 )ptr = bytes;
	barrier();
	}
	return ptr + len;
	}

	#define EMIT(bytes, len) do { prog = emit_code(prog, bytes, len); } while (0)

	#define EMIT1(b1) EMIT(b1, 1)
	#define EMIT2(b1, b2) EMIT((b1) + ((b2) << 8), 2)
	#define EMIT3(b1, b2, b3) EMIT((b1) + ((b2) << 8) + ((b3) << 16), 3)
	#define EMIT4(b1, b2, b3, b4) EMIT((b1) + ((b2) << 8) + ((b3) << 16) + ((b4) << 24), 4)
	#define EMIT1_off32(b1, off) do { EMIT1(b1); EMIT(off, 4);} while (0)

	#define CLEAR_A() EMIT2(0x31, 0xc0) /* xor %eax,%eax */
	#define CLEAR_X() EMIT2(0x31, 0xdb) /* xor %ebx,%ebx */

	static inline bool is_imm8(int value)
	{
	return value <= 127 && value >= -128;
	}

	static inline bool is_near(int offset)
	{
	return offset <= 127 && offset >= -128;
	}

	#define EMIT_JMP(offset) \
	do { \
	if (offset) { \
	if (is_near(offset)) \
	EMIT2(0xeb, offset); /* jmp .+off8 */ \
	else \
	EMIT1_off32(0xe9, offset); /* jmp .+off32 */ \
	} \
	} while (0)

	/* list of x86 cond jumps opcodes (. + s8)
	* Add 0x10 (and an extra 0x0f) to generate far jumps (. + s32)
	*/
	#define X86_JB 0x72
	#define X86_JAE 0x73
	#define X86_JE 0x74
	#define X86_JNE 0x75
	#define X86_JBE 0x76
	#define X86_JA 0x77

	#define EMIT_COND_JMP(op, offset) \
	do { \
	if (is_near(offset)) \
	EMIT2(op, offset); /* jxx .+off8 */ \
	else { \
	EMIT2(0x0f, op + 0x10); \
	EMIT(offset, 4); /* jxx .+off32 */ \
	} \
	} while (0)

	#define COND_SEL(CODE, TOP, FOP) \
	case CODE: \
	t_op = TOP; \
	f_op = FOP; \
	goto cond_branch


	#define SEEN_DATAREF 1 /* might call external helpers */
	#define SEEN_XREG 2 /* ebx is used */
	#define SEEN_MEM 4 /* use mem[] for temporary storage */

	static inline void bpf_flush_icache(void start, void end)
	{
	mm_segment_t old_fs = get_fs();

	set_fs(KERNEL_DS);
	smp_wmb();
	flush_icache_range((unsigned long)start, (unsigned long)end);
	set_fs(old_fs);
	}

	#define CHOOSE_LOAD_FUNC(K, func) \
	((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)

	void bpf_jit_compile(struct sk_filter *fp)
	{
	u8 temp[64];
	u8 *prog;
	unsigned int proglen, oldproglen = 0;
	int ilen, i;
	int t_offset, f_offset;
	u8 t_op, f_op, seen = 0, pass;
	u8 *image = NULL;
	u8 *func;
	int pc_ret0 = -1; /* bpf index of first RET #0 instruction (if any) */
	unsigned int cleanup_addr; /* epilogue code offset */
	unsigned int *addrs;
	const struct sock_filter *filter = fp->insns;
	int flen = fp->len;

	if (!bpf_jit_enable)
	return;

	addrs = kmalloc(flen * sizeof(*addrs), GFP_KERNEL);
	if (addrs == NULL)
	return;

	/* Before first pass, make a rough estimation of addrs[]
	* each bpf instruction is translated to less than 64 bytes
	*/
	for (proglen = 0, i = 0; i < flen; i++) {
	proglen += 64;
	addrs[i] = proglen;
	}
	cleanup_addr = proglen; /* epilogue address */

	for (pass = 0; pass < 10; pass++) {
	u8 seen_or_pass0 = (pass == 0) ? (SEEN_XREG \| SEEN_DATAREF \| SEEN_MEM) : seen;
	/* no prologue/epilogue for trivial filters (RET something) */
	proglen = 0;
	prog = temp;

	if (seen_or_pass0) {
	EMIT4(0x55, 0x48, 0x89, 0xe5); /* push %rbp; mov %rsp,%rbp */
	EMIT4(0x48, 0x83, 0xec, 96); /* subq $96,%rsp */
	/* note : must save %rbx in case bpf_error is hit */
	if (seen_or_pass0 & (SEEN_XREG \| SEEN_DATAREF))
	EMIT4(0x48, 0x89, 0x5d, 0xf8); /* mov %rbx, -8(%rbp) */
	if (seen_or_pass0 & SEEN_XREG)
	CLEAR_X(); /* make sure we dont leek kernel memory */

	/*
	* If this filter needs to access skb data,
	* loads r9 and r8 with :
	* r9 = skb->len - skb->data_len
	* r8 = skb->data
	*/
	if (seen_or_pass0 & SEEN_DATAREF) {
	if (offsetof(struct sk_buff, len) <= 127)
	/* mov off8(%rdi),%r9d */
	EMIT4(0x44, 0x8b, 0x4f, offsetof(struct sk_buff, len));
	else {
	/* mov off32(%rdi),%r9d */
	EMIT3(0x44, 0x8b, 0x8f);
	EMIT(offsetof(struct sk_buff, len), 4);
	}
	if (is_imm8(offsetof(struct sk_buff, data_len)))
	/* sub off8(%rdi),%r9d */
	EMIT4(0x44, 0x2b, 0x4f, offsetof(struct sk_buff, data_len));
	else {
	EMIT3(0x44, 0x2b, 0x8f);
	EMIT(offsetof(struct sk_buff, data_len), 4);
	}

	if (is_imm8(offsetof(struct sk_buff, data)))
	/* mov off8(%rdi),%r8 */
	EMIT4(0x4c, 0x8b, 0x47, offsetof(struct sk_buff, data));
	else {
	/* mov off32(%rdi),%r8 */
	EMIT3(0x4c, 0x8b, 0x87);
	EMIT(offsetof(struct sk_buff, data), 4);
	}
	}
	}

	switch (filter[0].code) {
	case BPF_S_RET_K:
	case BPF_S_LD_W_LEN:
	case BPF_S_ANC_PROTOCOL:
	case BPF_S_ANC_IFINDEX:
	case BPF_S_ANC_MARK:
	case BPF_S_ANC_RXHASH:
	case BPF_S_ANC_CPU:
	case BPF_S_ANC_VLAN_TAG:
	case BPF_S_ANC_VLAN_TAG_PRESENT:
	case BPF_S_ANC_QUEUE:
	case BPF_S_LD_W_ABS:
	case BPF_S_LD_H_ABS:
	case BPF_S_LD_B_ABS:
	/* first instruction sets A register (or is RET 'constant') */
	break;
	default:
	/* make sure we dont leak kernel information to user */
	CLEAR_A(); /* A = 0 */
	}

	for (i = 0; i < flen; i++) {
	unsigned int K = filter[i].k;

	switch (filter[i].code) {
	case BPF_S_ALU_ADD_X: /* A += X; */
	seen \|= SEEN_XREG;
	EMIT2(0x01, 0xd8); /* add %ebx,%eax */
	break;
	case BPF_S_ALU_ADD_K: /* A += K; */
	if (!K)
	break;
	if (is_imm8(K))
	EMIT3(0x83, 0xc0, K); /* add imm8,%eax */
	else
	EMIT1_off32(0x05, K); /* add imm32,%eax */
	break;
	case BPF_S_ALU_SUB_X: /* A -= X; */
	seen \|= SEEN_XREG;
	EMIT2(0x29, 0xd8); /* sub %ebx,%eax */
	break;
	case BPF_S_ALU_SUB_K: /* A -= K */
	if (!K)
	break;
	if (is_imm8(K))
	EMIT3(0x83, 0xe8, K); /* sub imm8,%eax */
	else
	EMIT1_off32(0x2d, K); /* sub imm32,%eax */
	break;
	case BPF_S_ALU_MUL_X: /* A = X; /
	seen \|= SEEN_XREG;
	EMIT3(0x0f, 0xaf, 0xc3); /* imul %ebx,%eax */
	break;
	case BPF_S_ALU_MUL_K: /* A = K /
	if (is_imm8(K))
	EMIT3(0x6b, 0xc0, K); /* imul imm8,%eax,%eax */
	else {
	EMIT2(0x69, 0xc0); /* imul imm32,%eax */
	EMIT(K, 4);
	}
	break;
	case BPF_S_ALU_DIV_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] - 4) is the address following this jmp
	* ("xor %edx,%edx; div %ebx" being 4 bytes long)
	*/
	EMIT_COND_JMP(X86_JE, addrs[pc_ret0 - 1] -
	(addrs[i] - 4));
	} else {
	EMIT_COND_JMP(X86_JNE, 2 + 5);
	CLEAR_A();
	EMIT1_off32(0xe9, cleanup_addr - (addrs[i] - 4)); /* jmp .+off32 */
	}
	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);
	EMIT4(0x48, 0xc1, 0xe8, 0x20); /* shr $0x20,%rax */
	break;
	case BPF_S_ALU_AND_X:
	seen \|= SEEN_XREG;
	EMIT2(0x21, 0xd8); /* and %ebx,%eax */
	break;
	case BPF_S_ALU_AND_K:
	if (K >= 0xFFFFFF00) {
	EMIT2(0x24, K & 0xFF); /* and imm8,%al */
	} else if (K >= 0xFFFF0000) {
	EMIT2(0x66, 0x25); /* and imm16,%ax */
	EMIT(K, 2);
	} else {
	EMIT1_off32(0x25, K); /* and imm32,%eax */
	}
	break;
	case BPF_S_ALU_OR_X:
	seen \|= SEEN_XREG;
	EMIT2(0x09, 0xd8); /* or %ebx,%eax */
	break;
	case BPF_S_ALU_OR_K:
	if (is_imm8(K))
	EMIT3(0x83, 0xc8, K); /* or imm8,%eax */
	else
	EMIT1_off32(0x0d, K); /* or imm32,%eax */
	break;
	case BPF_S_ANC_ALU_XOR_X: /* A ^= X; */
	case BPF_S_ALU_XOR_X:
	seen \|= SEEN_XREG;
	EMIT2(0x31, 0xd8); /* xor %ebx,%eax */
	break;
	case BPF_S_ALU_XOR_K: /* A ^= K; */
	if (K == 0)
	break;
	if (is_imm8(K))
	EMIT3(0x83, 0xf0, K); /* xor imm8,%eax */
	else
	EMIT1_off32(0x35, K); /* xor imm32,%eax */
	break;
	case BPF_S_ALU_LSH_X: /* A <<= X; */
	seen \|= SEEN_XREG;
	EMIT4(0x89, 0xd9, 0xd3, 0xe0); /* mov %ebx,%ecx; shl %cl,%eax */
	break;
	case BPF_S_ALU_LSH_K:
	if (K == 0)
	break;
	else if (K == 1)
	EMIT2(0xd1, 0xe0); /* shl %eax */
	else
	EMIT3(0xc1, 0xe0, K);
	break;
	case BPF_S_ALU_RSH_X: /* A >>= X; */
	seen \|= SEEN_XREG;
	EMIT4(0x89, 0xd9, 0xd3, 0xe8); /* mov %ebx,%ecx; shr %cl,%eax */
	break;
	case BPF_S_ALU_RSH_K: /* A >>= K; */
	if (K == 0)
	break;
	else if (K == 1)
	EMIT2(0xd1, 0xe8); /* shr %eax */
	else
	EMIT3(0xc1, 0xe8, K);
	break;
	case BPF_S_ALU_NEG:
	EMIT2(0xf7, 0xd8); /* neg %eax */
	break;
	case BPF_S_RET_K:
	if (!K) {
	if (pc_ret0 == -1)
	pc_ret0 = i;
	CLEAR_A();
	} else {
	EMIT1_off32(0xb8, K); /* mov $imm32,%eax */
	}
	/* fallinto */
	case BPF_S_RET_A:
	if (seen_or_pass0) {
	if (i != flen - 1) {
	EMIT_JMP(cleanup_addr - addrs[i]);
	break;
	}
	if (seen_or_pass0 & SEEN_XREG)
	EMIT4(0x48, 0x8b, 0x5d, 0xf8); /* mov -8(%rbp),%rbx */
	EMIT1(0xc9); /* leaveq */
	}
	EMIT1(0xc3); /* ret */
	break;
	case BPF_S_MISC_TAX: /* X = A */
	seen \|= SEEN_XREG;
	EMIT2(0x89, 0xc3); /* mov %eax,%ebx */
	break;
	case BPF_S_MISC_TXA: /* A = X */
	seen \|= SEEN_XREG;
	EMIT2(0x89, 0xd8); /* mov %ebx,%eax */
	break;
	case BPF_S_LD_IMM: /* A = K */
	if (!K)
	CLEAR_A();
	else
	EMIT1_off32(0xb8, K); /* mov $imm32,%eax */
	break;
	case BPF_S_LDX_IMM: /* X = K */
	seen \|= SEEN_XREG;
	if (!K)
	CLEAR_X();
	else
	EMIT1_off32(0xbb, K); /* mov $imm32,%ebx */
	break;
	case BPF_S_LD_MEM: /* A = mem[K] : mov off8(%rbp),%eax */
	seen \|= SEEN_MEM;
	EMIT3(0x8b, 0x45, 0xf0 - K*4);
	break;
	case BPF_S_LDX_MEM: /* X = mem[K] : mov off8(%rbp),%ebx */
	seen \|= SEEN_XREG \| SEEN_MEM;
	EMIT3(0x8b, 0x5d, 0xf0 - K*4);
	break;
	case BPF_S_ST: /* mem[K] = A : mov %eax,off8(%rbp) */
	seen \|= SEEN_MEM;
	EMIT3(0x89, 0x45, 0xf0 - K*4);
	break;
	case BPF_S_STX: /* mem[K] = X : mov %ebx,off8(%rbp) */
	seen \|= SEEN_XREG \| SEEN_MEM;
	EMIT3(0x89, 0x5d, 0xf0 - K*4);
	break;
	case BPF_S_LD_W_LEN: /* A = skb->len; */
	BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
	if (is_imm8(offsetof(struct sk_buff, len)))
	/* mov off8(%rdi),%eax */
	EMIT3(0x8b, 0x47, offsetof(struct sk_buff, len));
	else {
	EMIT2(0x8b, 0x87);
	EMIT(offsetof(struct sk_buff, len), 4);
	}
	break;
	case BPF_S_LDX_W_LEN: /* X = skb->len; */
	seen \|= SEEN_XREG;
	if (is_imm8(offsetof(struct sk_buff, len)))
	/* mov off8(%rdi),%ebx */
	EMIT3(0x8b, 0x5f, offsetof(struct sk_buff, len));
	else {
	EMIT2(0x8b, 0x9f);
	EMIT(offsetof(struct sk_buff, len), 4);
	}
	break;
	case BPF_S_ANC_PROTOCOL: /* A = ntohs(skb->protocol); */
	BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);
	if (is_imm8(offsetof(struct sk_buff, protocol))) {
	/* movzwl off8(%rdi),%eax */
	EMIT4(0x0f, 0xb7, 0x47, offsetof(struct sk_buff, protocol));
	} else {
	EMIT3(0x0f, 0xb7, 0x87); /* movzwl off32(%rdi),%eax */
	EMIT(offsetof(struct sk_buff, protocol), 4);
	}
	EMIT2(0x86, 0xc4); /* ntohs() : xchg %al,%ah */
	break;
	case BPF_S_ANC_IFINDEX:
	if (is_imm8(offsetof(struct sk_buff, dev))) {
	/* movq off8(%rdi),%rax */
	EMIT4(0x48, 0x8b, 0x47, offsetof(struct sk_buff, dev));
	} else {
	EMIT3(0x48, 0x8b, 0x87); /* movq off32(%rdi),%rax */
	EMIT(offsetof(struct sk_buff, dev), 4);
	}
	EMIT3(0x48, 0x85, 0xc0); /* test %rax,%rax */
	EMIT_COND_JMP(X86_JE, cleanup_addr - (addrs[i] - 6));
	BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
	EMIT2(0x8b, 0x80); /* mov off32(%rax),%eax */
	EMIT(offsetof(struct net_device, ifindex), 4);
	break;
	case BPF_S_ANC_MARK:
	BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
	if (is_imm8(offsetof(struct sk_buff, mark))) {
	/* mov off8(%rdi),%eax */
	EMIT3(0x8b, 0x47, offsetof(struct sk_buff, mark));
	} else {
	EMIT2(0x8b, 0x87);
	EMIT(offsetof(struct sk_buff, mark), 4);
	}
	break;
	case BPF_S_ANC_RXHASH:
	BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, rxhash) != 4);
	if (is_imm8(offsetof(struct sk_buff, rxhash))) {
	/* mov off8(%rdi),%eax */
	EMIT3(0x8b, 0x47, offsetof(struct sk_buff, rxhash));
	} else {
	EMIT2(0x8b, 0x87);
	EMIT(offsetof(struct sk_buff, rxhash), 4);
	}
	break;
	case BPF_S_ANC_QUEUE:
	BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, queue_mapping) != 2);
	if (is_imm8(offsetof(struct sk_buff, queue_mapping))) {
	/* movzwl off8(%rdi),%eax */
	EMIT4(0x0f, 0xb7, 0x47, offsetof(struct sk_buff, queue_mapping));
	} else {
	EMIT3(0x0f, 0xb7, 0x87); /* movzwl off32(%rdi),%eax */
	EMIT(offsetof(struct sk_buff, queue_mapping), 4);
	}
	break;
	case BPF_S_ANC_CPU:
	#ifdef CONFIG_SMP
	EMIT4(0x65, 0x8b, 0x04, 0x25); /* mov %gs:off32,%eax */
	EMIT((u32)(unsigned long)&cpu_number, 4); /* A = smp_processor_id(); */
	#else
	CLEAR_A();
	#endif
	break;
	case BPF_S_ANC_VLAN_TAG:
	case BPF_S_ANC_VLAN_TAG_PRESENT:
	BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
	if (is_imm8(offsetof(struct sk_buff, vlan_tci))) {
	/* movzwl off8(%rdi),%eax */
	EMIT4(0x0f, 0xb7, 0x47, offsetof(struct sk_buff, vlan_tci));
	} else {
	EMIT3(0x0f, 0xb7, 0x87); /* movzwl off32(%rdi),%eax */
	EMIT(offsetof(struct sk_buff, vlan_tci), 4);
	}
	BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
	if (filter[i].code == BPF_S_ANC_VLAN_TAG) {
	EMIT3(0x80, 0xe4, 0xef); /* and $0xef,%ah */
	} else {
	EMIT3(0xc1, 0xe8, 0x0c); /* shr $0xc,%eax */
	EMIT3(0x83, 0xe0, 0x01); /* and $0x1,%eax */
	}
	break;
	case BPF_S_LD_W_ABS:
	func = CHOOSE_LOAD_FUNC(K, sk_load_word);
	common_load: seen \|= SEEN_DATAREF;
	t_offset = func - (image + addrs[i]);
	EMIT1_off32(0xbe, K); /* mov imm32,%esi */
	EMIT1_off32(0xe8, t_offset); /* call */
	break;
	case BPF_S_LD_H_ABS:
	func = CHOOSE_LOAD_FUNC(K, sk_load_half);
	goto common_load;
	case BPF_S_LD_B_ABS:
	func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
	goto common_load;
	case BPF_S_LDX_B_MSH:
	func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
	seen \|= SEEN_DATAREF \| SEEN_XREG;
	t_offset = func - (image + addrs[i]);
	EMIT1_off32(0xbe, K); /* mov imm32,%esi */
	EMIT1_off32(0xe8, t_offset); /* call sk_load_byte_msh */
	break;
	case BPF_S_LD_W_IND:
	func = sk_load_word;
	common_load_ind: seen \|= SEEN_DATAREF \| SEEN_XREG;
	t_offset = func - (image + addrs[i]);
	if (K) {
	if (is_imm8(K)) {
	EMIT3(0x8d, 0x73, K); /* lea imm8(%rbx), %esi */
	} else {
	EMIT2(0x8d, 0xb3); /* lea imm32(%rbx),%esi */
	EMIT(K, 4);
	}
	} else {
	EMIT2(0x89,0xde); /* mov %ebx,%esi */
	}
	EMIT1_off32(0xe8, t_offset); /* call sk_load_xxx_ind */
	break;
	case BPF_S_LD_H_IND:
	func = sk_load_half;
	goto common_load_ind;
	case BPF_S_LD_B_IND:
	func = sk_load_byte;
	goto common_load_ind;
	case BPF_S_JMP_JA:
	t_offset = addrs[i + K] - addrs[i];
	EMIT_JMP(t_offset);
	break;
	COND_SEL(BPF_S_JMP_JGT_K, X86_JA, X86_JBE);
	COND_SEL(BPF_S_JMP_JGE_K, X86_JAE, X86_JB);
	COND_SEL(BPF_S_JMP_JEQ_K, X86_JE, X86_JNE);
	COND_SEL(BPF_S_JMP_JSET_K,X86_JNE, X86_JE);
	COND_SEL(BPF_S_JMP_JGT_X, X86_JA, X86_JBE);
	COND_SEL(BPF_S_JMP_JGE_X, X86_JAE, X86_JB);
	COND_SEL(BPF_S_JMP_JEQ_X, X86_JE, X86_JNE);
	COND_SEL(BPF_S_JMP_JSET_X,X86_JNE, X86_JE);

	cond_branch: f_offset = addrs[i + filter[i].jf] - addrs[i];
	t_offset = addrs[i + filter[i].jt] - addrs[i];

	/* same targets, can avoid doing the test :) */
	if (filter[i].jt == filter[i].jf) {
	EMIT_JMP(t_offset);
	break;
	}

	switch (filter[i].code) {
	case BPF_S_JMP_JGT_X:
	case BPF_S_JMP_JGE_X:
	case BPF_S_JMP_JEQ_X:
	seen \|= SEEN_XREG;
	EMIT2(0x39, 0xd8); /* cmp %ebx,%eax */
	break;
	case BPF_S_JMP_JSET_X:
	seen \|= SEEN_XREG;
	EMIT2(0x85, 0xd8); /* test %ebx,%eax */
	break;
	case BPF_S_JMP_JEQ_K:
	if (K == 0) {
	EMIT2(0x85, 0xc0); /* test %eax,%eax */
	break;
	}
	case BPF_S_JMP_JGT_K:
	case BPF_S_JMP_JGE_K:
	if (K <= 127)
	EMIT3(0x83, 0xf8, K); /* cmp imm8,%eax */
	else
	EMIT1_off32(0x3d, K); /* cmp imm32,%eax */
	break;
	case BPF_S_JMP_JSET_K:
	if (K <= 0xFF)
	EMIT2(0xa8, K); /* test imm8,%al */
	else if (!(K & 0xFFFF00FF))
	EMIT3(0xf6, 0xc4, K >> 8); /* test imm8,%ah */
	else if (K <= 0xFFFF) {
	EMIT2(0x66, 0xa9); /* test imm16,%ax */
	EMIT(K, 2);
	} else {
	EMIT1_off32(0xa9, K); /* test imm32,%eax */
	}
	break;
	}
	if (filter[i].jt != 0) {
	if (filter[i].jf && f_offset)
	t_offset += is_near(f_offset) ? 2 : 5;
	EMIT_COND_JMP(t_op, t_offset);
	if (filter[i].jf)
	EMIT_JMP(f_offset);
	break;
	}
	EMIT_COND_JMP(f_op, f_offset);
	break;
	default:
	/* hmm, too complex filter, give up with jit compiler */
	goto out;
	}
	ilen = prog - temp;
	if (image) {
	if (unlikely(proglen + ilen > oldproglen)) {
	pr_err("bpb_jit_compile fatal error\n");
	kfree(addrs);
	module_free(NULL, image);
	return;
	}
	memcpy(image + proglen, temp, ilen);
	}
	proglen += ilen;
	addrs[i] = proglen;
	prog = temp;
	}
	/* last bpf instruction is always a RET :
	* use it to give the cleanup instruction(s) addr
	*/
	cleanup_addr = proglen - 1; /* ret */
	if (seen_or_pass0)
	cleanup_addr -= 1; /* leaveq */
	if (seen_or_pass0 & SEEN_XREG)
	cleanup_addr -= 4; /* mov -8(%rbp),%rbx */

	if (image) {
	if (proglen != oldproglen)
	pr_err("bpb_jit_compile proglen=%u != oldproglen=%u\n", proglen, oldproglen);
	break;
	}
	if (proglen == oldproglen) {
	image = module_alloc(max_t(unsigned int,
	proglen,
	sizeof(struct work_struct)));
	if (!image)
	goto out;
	}
	oldproglen = proglen;
	}
	if (bpf_jit_enable > 1)
	pr_err("flen=%d proglen=%u pass=%d image=%p\n",
	flen, proglen, pass, image);

	if (image) {
	if (bpf_jit_enable > 1)
	print_hex_dump(KERN_ERR, "JIT code: ", DUMP_PREFIX_ADDRESS,
	16, 1, image, proglen, false);

	bpf_flush_icache(image, image + proglen);

	fp->bpf_func = (void *)image;
	}
	out:
	kfree(addrs);
	return;
	}

	static void jit_free_defer(struct work_struct *arg)
	{
	module_free(NULL, arg);
	}

	/* run from softirq, we must use a work_struct to call
	* module_free() from process context
	*/
	void bpf_jit_free(struct sk_filter *fp)
	{
	if (fp->bpf_func != sk_run_filter) {
	struct work_struct work = (struct work_struct )fp->bpf_func;

	INIT_WORK(work, jit_free_defer);
	schedule_work(work);
	}
	}