arch/x86/net/bpf_jit_comp.c

/* bpf_jit_comp.c : BPF JIT compiler
 *
 * Copyright (C) 2011-2013 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>
#include <linux/random.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)

/* Helper to find the offset of pkt_type in sk_buff
 * We want to make sure its still a 3bit field starting at a byte boundary.
 */
#define PKT_TYPE_MAX 7
static int pkt_type_offset(void)
{
	struct sk_buff skb_probe = {
		.pkt_type = ~0,
	};
	char *ct = (char *)&skb_probe;
	unsigned int off;

	for (off = 0; off < sizeof(struct sk_buff); off++) {
		if (ct[off] == PKT_TYPE_MAX)
			return off;
	}
	pr_err_once("Please fix pkt_type_offset(), as pkt_type couldn't be found\n");
	return -1;
}

struct bpf_binary_header {
	unsigned int	pages;
	/* Note : for security reasons, bpf code will follow a randomly
	 * sized amount of int3 instructions
	 */
	u8		image[];
};

static struct bpf_binary_header *bpf_alloc_binary(unsigned int proglen,
						  u8 **image_ptr)
{
	unsigned int sz, hole;
	struct bpf_binary_header *header;

	/* Most of BPF filters are really small,
	 * but if some of them fill a page, allow at least
	 * 128 extra bytes to insert a random section of int3
	 */
	sz = round_up(proglen + sizeof(*header) + 128, PAGE_SIZE);
	header = module_alloc(sz);
	if (!header)
		return NULL;

	memset(header, 0xcc, sz); /* fill whole space with int3 instructions */

	header->pages = sz / PAGE_SIZE;
	hole = sz - (proglen + sizeof(*header));

	/* insert a random number of int3 instructions before BPF code */
	*image_ptr = &header->image[prandom_u32() % hole];
	return header;
}

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;
	struct bpf_binary_header *header = 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_ANC_PKTTYPE:
		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_ANC_PKTTYPE:
			{
				int off = pkt_type_offset();

				if (off < 0)
					goto out;
				if (is_imm8(off)) {
					/* movzbl off8(%rdi),%eax */
					EMIT4(0x0f, 0xb6, 0x47, off);
				} else {
					/* movbl off32(%rdi),%eax */
					EMIT3(0x0f, 0xb6, 0x87);
					EMIT(off, 4);
				}
				EMIT3(0x83, 0xe0, PKT_TYPE_MAX); /* and    $0x7,%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, header);
					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) {
			header = bpf_alloc_binary(proglen, &image);
			if (!header)
				goto out;
		}
		oldproglen = proglen;
	}

	if (bpf_jit_enable > 1)
		bpf_jit_dump(flen, proglen, pass, image);

	if (image) {
		bpf_flush_icache(header, image + proglen);
		set_memory_ro((unsigned long)header, header->pages);
		fp->bpf_func = (void *)image;
	}
out:
	kfree(addrs);
	return;
}

static void bpf_jit_free_deferred(struct work_struct *work)
{
	struct sk_filter *fp = container_of(work, struct sk_filter, work);
	unsigned long addr = (unsigned long)fp->bpf_func & PAGE_MASK;
	struct bpf_binary_header *header = (void *)addr;

	set_memory_rw(addr, header->pages);
	module_free(NULL, header);
	kfree(fp);
}

void bpf_jit_free(struct sk_filter *fp)
{
	if (fp->bpf_func != sk_run_filter) {
		INIT_WORK(&fp->work, bpf_jit_free_deferred);
		schedule_work(&fp->work);
	} else {
		kfree(fp);
	}
}