Free Electrons

Embedded Linux Experts

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
/* 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; */
				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 /= 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;
				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);
	}
}