aboutsummaryrefslogtreecommitdiffstats
path: root/arch/arm/net/bpf_jit_32.c
blob: 9ed155ad0f97c42c80fd903919a51dac8b0298d4 (plain) (blame)
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
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
/*
 * Just-In-Time compiler for BPF filters on 32bit ARM
 *
 * Copyright (c) 2011 Mircea Gherzan <mgherzan@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/bitops.h>
#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/filter.h>
#include <linux/moduleloader.h>
#include <linux/netdevice.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/if_vlan.h>
#include <asm/cacheflush.h>
#include <asm/hwcap.h>
#include <asm/opcodes.h>

#include "bpf_jit_32.h"

/*
 * ABI:
 *
 * r0	scratch register
 * r4	BPF register A
 * r5	BPF register X
 * r6	pointer to the skb
 * r7	skb->data
 * r8	skb_headlen(skb)
 */

#define r_scratch	ARM_R0
/* r1-r3 are (also) used for the unaligned loads on the non-ARMv7 slowpath */
#define r_off		ARM_R1
#define r_A		ARM_R4
#define r_X		ARM_R5
#define r_skb		ARM_R6
#define r_skb_data	ARM_R7
#define r_skb_hl	ARM_R8

#define SCRATCH_SP_OFFSET	0
#define SCRATCH_OFF(k)		(SCRATCH_SP_OFFSET + 4 * (k))

#define SEEN_MEM		((1 << BPF_MEMWORDS) - 1)
#define SEEN_MEM_WORD(k)	(1 << (k))
#define SEEN_X			(1 << BPF_MEMWORDS)
#define SEEN_CALL		(1 << (BPF_MEMWORDS + 1))
#define SEEN_SKB		(1 << (BPF_MEMWORDS + 2))
#define SEEN_DATA		(1 << (BPF_MEMWORDS + 3))

#define FLAG_NEED_X_RESET	(1 << 0)

struct jit_ctx {
	const struct sk_filter *skf;
	unsigned idx;
	unsigned prologue_bytes;
	int ret0_fp_idx;
	u32 seen;
	u32 flags;
	u32 *offsets;
	u32 *target;
#if __LINUX_ARM_ARCH__ < 7
	u16 epilogue_bytes;
	u16 imm_count;
	u32 *imms;
#endif
};

int bpf_jit_enable __read_mostly;

static u64 jit_get_skb_b(struct sk_buff *skb, unsigned offset)
{
	u8 ret;
	int err;

	err = skb_copy_bits(skb, offset, &ret, 1);

	return (u64)err << 32 | ret;
}

static u64 jit_get_skb_h(struct sk_buff *skb, unsigned offset)
{
	u16 ret;
	int err;

	err = skb_copy_bits(skb, offset, &ret, 2);

	return (u64)err << 32 | ntohs(ret);
}

static u64 jit_get_skb_w(struct sk_buff *skb, unsigned offset)
{
	u32 ret;
	int err;

	err = skb_copy_bits(skb, offset, &ret, 4);

	return (u64)err << 32 | ntohl(ret);
}

/*
 * Wrapper that handles both OABI and EABI and assures Thumb2 interworking
 * (where the assembly routines like __aeabi_uidiv could cause problems).
 */
static u32 jit_udiv(u32 dividend, u32 divisor)
{
	return dividend / divisor;
}

static inline void _emit(int cond, u32 inst, struct jit_ctx *ctx)
{
	inst |= (cond << 28);
	inst = __opcode_to_mem_arm(inst);

	if (ctx->target != NULL)
		ctx->target[ctx->idx] = inst;

	ctx->idx++;
}

/*
 * Emit an instruction that will be executed unconditionally.
 */
static inline void emit(u32 inst, struct jit_ctx *ctx)
{
	_emit(ARM_COND_AL, inst, ctx);
}

static u16 saved_regs(struct jit_ctx *ctx)
{
	u16 ret = 0;

	if ((ctx->skf->len > 1) ||
	    (ctx->skf->insns[0].code == BPF_S_RET_A))
		ret |= 1 << r_A;

#ifdef CONFIG_FRAME_POINTER
	ret |= (1 << ARM_FP) | (1 << ARM_IP) | (1 << ARM_LR) | (1 << ARM_PC);
#else
	if (ctx->seen & SEEN_CALL)
		ret |= 1 << ARM_LR;
#endif
	if (ctx->seen & (SEEN_DATA | SEEN_SKB))
		ret |= 1 << r_skb;
	if (ctx->seen & SEEN_DATA)
		ret |= (1 << r_skb_data) | (1 << r_skb_hl);
	if (ctx->seen & SEEN_X)
		ret |= 1 << r_X;

	return ret;
}

static inline int mem_words_used(struct jit_ctx *ctx)
{
	/* yes, we do waste some stack space IF there are "holes" in the set" */
	return fls(ctx->seen & SEEN_MEM);
}

static inline bool is_load_to_a(u16 inst)
{
	switch (inst) {
	case BPF_S_LD_W_LEN:
	case BPF_S_LD_W_ABS:
	case BPF_S_LD_H_ABS:
	case BPF_S_LD_B_ABS:
	case BPF_S_ANC_CPU:
	case BPF_S_ANC_IFINDEX:
	case BPF_S_ANC_MARK:
	case BPF_S_ANC_PROTOCOL:
	case BPF_S_ANC_RXHASH:
	case BPF_S_ANC_VLAN_TAG:
	case BPF_S_ANC_VLAN_TAG_PRESENT:
	case BPF_S_ANC_QUEUE:
		return true;
	default:
		return false;
	}
}

static void build_prologue(struct jit_ctx *ctx)
{
	u16 reg_set = saved_regs(ctx);
	u16 first_inst = ctx->skf->insns[0].code;
	u16 off;

#ifdef CONFIG_FRAME_POINTER
	emit(ARM_MOV_R(ARM_IP, ARM_SP), ctx);
	emit(ARM_PUSH(reg_set), ctx);
	emit(ARM_SUB_I(ARM_FP, ARM_IP, 4), ctx);
#else
	if (reg_set)
		emit(ARM_PUSH(reg_set), ctx);
#endif

	if (ctx->seen & (SEEN_DATA | SEEN_SKB))
		emit(ARM_MOV_R(r_skb, ARM_R0), ctx);

	if (ctx->seen & SEEN_DATA) {
		off = offsetof(struct sk_buff, data);
		emit(ARM_LDR_I(r_skb_data, r_skb, off), ctx);
		/* headlen = len - data_len */
		off = offsetof(struct sk_buff, len);
		emit(ARM_LDR_I(r_skb_hl, r_skb, off), ctx);
		off = offsetof(struct sk_buff, data_len);
		emit(ARM_LDR_I(r_scratch, r_skb, off), ctx);
		emit(ARM_SUB_R(r_skb_hl, r_skb_hl, r_scratch), ctx);
	}

	if (ctx->flags & FLAG_NEED_X_RESET)
		emit(ARM_MOV_I(r_X, 0), ctx);

	/* do not leak kernel data to userspace */
	if ((first_inst != BPF_S_RET_K) && !(is_load_to_a(first_inst)))
		emit(ARM_MOV_I(r_A, 0), ctx);

	/* stack space for the BPF_MEM words */
	if (ctx->seen & SEEN_MEM)
		emit(ARM_SUB_I(ARM_SP, ARM_SP, mem_words_used(ctx) * 4), ctx);
}

static void build_epilogue(struct jit_ctx *ctx)
{
	u16 reg_set = saved_regs(ctx);

	if (ctx->seen & SEEN_MEM)
		emit(ARM_ADD_I(ARM_SP, ARM_SP, mem_words_used(ctx) * 4), ctx);

	reg_set &= ~(1 << ARM_LR);

#ifdef CONFIG_FRAME_POINTER
	/* the first instruction of the prologue was: mov ip, sp */
	reg_set &= ~(1 << ARM_IP);
	reg_set |= (1 << ARM_SP);
	emit(ARM_LDM(ARM_SP, reg_set), ctx);
#else
	if (reg_set) {
		if (ctx->seen & SEEN_CALL)
			reg_set |= 1 << ARM_PC;
		emit(ARM_POP(reg_set), ctx);
	}

	if (!(ctx->seen & SEEN_CALL))
		emit(ARM_BX(ARM_LR), ctx);
#endif
}

static int16_t imm8m(u32 x)
{
	u32 rot;

	for (rot = 0; rot < 16; rot++)
		if ((x & ~ror32(0xff, 2 * rot)) == 0)
			return rol32(x, 2 * rot) | (rot << 8);

	return -1;
}

#if __LINUX_ARM_ARCH__ < 7

static u16 imm_offset(u32 k, struct jit_ctx *ctx)
{
	unsigned i = 0, offset;
	u16 imm;

	/* on the "fake" run we just count them (duplicates included) */
	if (ctx->target == NULL) {
		ctx->imm_count++;
		return 0;
	}

	while ((i < ctx->imm_count) && ctx->imms[i]) {
		if (ctx->imms[i] == k)
			break;
		i++;
	}

	if (ctx->imms[i] == 0)
		ctx->imms[i] = k;

	/* constants go just after the epilogue */
	offset =  ctx->offsets[ctx->skf->len];
	offset += ctx->prologue_bytes;
	offset += ctx->epilogue_bytes;
	offset += i * 4;

	ctx->target[offset / 4] = k;

	/* PC in ARM mode == address of the instruction + 8 */
	imm = offset - (8 + ctx->idx * 4);

	return imm;
}

#endif /* __LINUX_ARM_ARCH__ */

/*
 * Move an immediate that's not an imm8m to a core register.
 */
static inline void emit_mov_i_no8m(int rd, u32 val, struct jit_ctx *ctx)
{
#if __LINUX_ARM_ARCH__ < 7
	emit(ARM_LDR_I(rd, ARM_PC, imm_offset(val, ctx)), ctx);
#else
	emit(ARM_MOVW(rd, val & 0xffff), ctx);
	if (val > 0xffff)
		emit(ARM_MOVT(rd, val >> 16), ctx);
#endif
}

static inline void emit_mov_i(int rd, u32 val, struct jit_ctx *ctx)
{
	int imm12 = imm8m(val);

	if (imm12 >= 0)
		emit(ARM_MOV_I(rd, imm12), ctx);
	else
		emit_mov_i_no8m(rd, val, ctx);
}

#if __LINUX_ARM_ARCH__ < 6

static void emit_load_be32(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx)
{
	_emit(cond, ARM_LDRB_I(ARM_R3, r_addr, 1), ctx);
	_emit(cond, ARM_LDRB_I(ARM_R1, r_addr, 0), ctx);
	_emit(cond, ARM_LDRB_I(ARM_R2, r_addr, 3), ctx);
	_emit(cond, ARM_LSL_I(ARM_R3, ARM_R3, 16), ctx);
	_emit(cond, ARM_LDRB_I(ARM_R0, r_addr, 2), ctx);
	_emit(cond, ARM_ORR_S(ARM_R3, ARM_R3, ARM_R1, SRTYPE_LSL, 24), ctx);
	_emit(cond, ARM_ORR_R(ARM_R3, ARM_R3, ARM_R2), ctx);
	_emit(cond, ARM_ORR_S(r_res, ARM_R3, ARM_R0, SRTYPE_LSL, 8), ctx);
}

static void emit_load_be16(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx)
{
	_emit(cond, ARM_LDRB_I(ARM_R1, r_addr, 0), ctx);
	_emit(cond, ARM_LDRB_I(ARM_R2, r_addr, 1), ctx);
	_emit(cond, ARM_ORR_S(r_res, ARM_R2, ARM_R1, SRTYPE_LSL, 8), ctx);
}

static inline void emit_swap16(u8 r_dst, u8 r_src, struct jit_ctx *ctx)
{
	/* r_dst = (r_src << 8) | (r_src >> 8) */
	emit(ARM_LSL_I(ARM_R1, r_src, 8), ctx);
	emit(ARM_ORR_S(r_dst, ARM_R1, r_src, SRTYPE_LSR, 8), ctx);

	/*
	 * we need to mask out the bits set in r_dst[23:16] due to
	 * the first shift instruction.
	 *
	 * note that 0x8ff is the encoded immediate 0x00ff0000.
	 */
	emit(ARM_BIC_I(r_dst, r_dst, 0x8ff), ctx);
}

#else  /* ARMv6+ */

static void emit_load_be32(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx)
{
	_emit(cond, ARM_LDR_I(r_res, r_addr, 0), ctx);
#ifdef __LITTLE_ENDIAN
	_emit(cond, ARM_REV(r_res, r_res), ctx);
#endif
}

static void emit_load_be16(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx)
{
	_emit(cond, ARM_LDRH_I(r_res, r_addr, 0), ctx);
#ifdef __LITTLE_ENDIAN
	_emit(cond, ARM_REV16(r_res, r_res), ctx);
#endif
}

static inline void emit_swap16(u8 r_dst __maybe_unused,
			       u8 r_src __maybe_unused,
			       struct jit_ctx *ctx __maybe_unused)
{
#ifdef __LITTLE_ENDIAN
	emit(ARM_REV16(r_dst, r_src), ctx);
#endif
}

#endif /* __LINUX_ARM_ARCH__ < 6 */


/* Compute the immediate value for a PC-relative branch. */
static inline u32 b_imm(unsigned tgt, struct jit_ctx *ctx)
{
	u32 imm;

	if (ctx->target == NULL)
		return 0;
	/*
	 * BPF allows only forward jumps and the offset of the target is
	 * still the one computed during the first pass.
	 */
	imm  = ctx->offsets[tgt] + ctx->prologue_bytes - (ctx->idx * 4 + 8);

	return imm >> 2;
}

#define OP_IMM3(op, r1, r2, imm_val, ctx)				\
	do {								\
		imm12 = imm8m(imm_val);					\
		if (imm12 < 0) {					\
			emit_mov_i_no8m(r_scratch, imm_val, ctx);	\
			emit(op ## _R((r1), (r2), r_scratch), ctx);	\
		} else {						\
			emit(op ## _I((r1), (r2), imm12), ctx);		\
		}							\
	} while (0)

static inline void emit_err_ret(u8 cond, struct jit_ctx *ctx)
{
	if (ctx->ret0_fp_idx >= 0) {
		_emit(cond, ARM_B(b_imm(ctx->ret0_fp_idx, ctx)), ctx);
		/* NOP to keep the size constant between passes */
		emit(ARM_MOV_R(ARM_R0, ARM_R0), ctx);
	} else {
		_emit(cond, ARM_MOV_I(ARM_R0, 0), ctx);
		_emit(cond, ARM_B(b_imm(ctx->skf->len, ctx)), ctx);
	}
}

static inline void emit_blx_r(u8 tgt_reg, struct jit_ctx *ctx)
{
#if __LINUX_ARM_ARCH__ < 5
	emit(ARM_MOV_R(ARM_LR, ARM_PC), ctx);

	if (elf_hwcap & HWCAP_THUMB)
		emit(ARM_BX(tgt_reg), ctx);
	else
		emit(ARM_MOV_R(ARM_PC, tgt_reg), ctx);
#else
	emit(ARM_BLX_R(tgt_reg), ctx);
#endif
}

static inline void emit_udiv(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx)
{
#if __LINUX_ARM_ARCH__ == 7
	if (elf_hwcap & HWCAP_IDIVA) {
		emit(ARM_UDIV(rd, rm, rn), ctx);
		return;
	}
#endif
	if (rm != ARM_R0)
		emit(ARM_MOV_R(ARM_R0, rm), ctx);
	if (rn != ARM_R1)
		emit(ARM_MOV_R(ARM_R1, rn), ctx);

	ctx->seen |= SEEN_CALL;
	emit_mov_i(ARM_R3, (u32)jit_udiv, ctx);
	emit_blx_r(ARM_R3, ctx);

	if (rd != ARM_R0)
		emit(ARM_MOV_R(rd, ARM_R0), ctx);
}

static inline void update_on_xread(struct jit_ctx *ctx)
{
	if (!(ctx->seen & SEEN_X))
		ctx->flags |= FLAG_NEED_X_RESET;

	ctx->seen |= SEEN_X;
}

static int build_body(struct jit_ctx *ctx)
{
	void *load_func[] = {jit_get_skb_b, jit_get_skb_h, jit_get_skb_w};
	const struct sk_filter *prog = ctx->skf;
	const struct sock_filter *inst;
	unsigned i, load_order, off, condt;
	int imm12;
	u32 k;

	for (i = 0; i < prog->len; i++) {
		inst = &(prog->insns[i]);
		/* K as an immediate value operand */
		k = inst->k;

		/* compute offsets only in the fake pass */
		if (ctx->target == NULL)
			ctx->offsets[i] = ctx->idx * 4;

		switch (inst->code) {
		case BPF_S_LD_IMM:
			emit_mov_i(r_A, k, ctx);
			break;
		case BPF_S_LD_W_LEN:
			ctx->seen |= SEEN_SKB;
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
			emit(ARM_LDR_I(r_A, r_skb,
				       offsetof(struct sk_buff, len)), ctx);
			break;
		case BPF_S_LD_MEM:
			/* A = scratch[k] */
			ctx->seen |= SEEN_MEM_WORD(k);
			emit(ARM_LDR_I(r_A, ARM_SP, SCRATCH_OFF(k)), ctx);
			break;
		case BPF_S_LD_W_ABS:
			load_order = 2;
			goto load;
		case BPF_S_LD_H_ABS:
			load_order = 1;
			goto load;
		case BPF_S_LD_B_ABS:
			load_order = 0;
load:
			/* the interpreter will deal with the negative K */
			if ((int)k < 0)
				return -ENOTSUPP;
			emit_mov_i(r_off, k, ctx);
load_common:
			ctx->seen |= SEEN_DATA | SEEN_CALL;

			if (load_order > 0) {
				emit(ARM_SUB_I(r_scratch, r_skb_hl,
					       1 << load_order), ctx);
				emit(ARM_CMP_R(r_scratch, r_off), ctx);
				condt = ARM_COND_HS;
			} else {
				emit(ARM_CMP_R(r_skb_hl, r_off), ctx);
				condt = ARM_COND_HI;
			}

			_emit(condt, ARM_ADD_R(r_scratch, r_off, r_skb_data),
			      ctx);

			if (load_order == 0)
				_emit(condt, ARM_LDRB_I(r_A, r_scratch, 0),
				      ctx);
			else if (load_order == 1)
				emit_load_be16(condt, r_A, r_scratch, ctx);
			else if (load_order == 2)
				emit_load_be32(condt, r_A, r_scratch, ctx);

			_emit(condt, ARM_B(b_imm(i + 1, ctx)), ctx);

			/* the slowpath */
			emit_mov_i(ARM_R3, (u32)load_func[load_order], ctx);
			emit(ARM_MOV_R(ARM_R0, r_skb), ctx);
			/* the offset is already in R1 */
			emit_blx_r(ARM_R3, ctx);
			/* check the result of skb_copy_bits */
			emit(ARM_CMP_I(ARM_R1, 0), ctx);
			emit_err_ret(ARM_COND_NE, ctx);
			emit(ARM_MOV_R(r_A, ARM_R0), ctx);
			break;
		case BPF_S_LD_W_IND:
			load_order = 2;
			goto load_ind;
		case BPF_S_LD_H_IND:
			load_order = 1;
			goto load_ind;
		case BPF_S_LD_B_IND:
			load_order = 0;
load_ind:
			OP_IMM3(ARM_ADD, r_off, r_X, k, ctx);
			goto load_common;
		case BPF_S_LDX_IMM:
			ctx->seen |= SEEN_X;
			emit_mov_i(r_X, k, ctx);
			break;
		case BPF_S_LDX_W_LEN:
			ctx->seen |= SEEN_X | SEEN_SKB;
			emit(ARM_LDR_I(r_X, r_skb,
				       offsetof(struct sk_buff, len)), ctx);
			break;
		case BPF_S_LDX_MEM:
			ctx->seen |= SEEN_X | SEEN_MEM_WORD(k);
			emit(ARM_LDR_I(r_X, ARM_SP, SCRATCH_OFF(k)), ctx);
			break;
		case BPF_S_LDX_B_MSH:
			/* x = ((*(frame + k)) & 0xf) << 2; */
			ctx->seen |= SEEN_X | SEEN_DATA | SEEN_CALL;
			/* the interpreter should deal with the negative K */
			if ((int)k < 0)
				return -1;
			/* offset in r1: we might have to take the slow path */
			emit_mov_i(r_off, k, ctx);
			emit(ARM_CMP_R(r_skb_hl, r_off), ctx);

			/* load in r0: common with the slowpath */
			_emit(ARM_COND_HI, ARM_LDRB_R(ARM_R0, r_skb_data,
						      ARM_R1), ctx);
			/*
			 * emit_mov_i() might generate one or two instructions,
			 * the same holds for emit_blx_r()
			 */
			_emit(ARM_COND_HI, ARM_B(b_imm(i + 1, ctx) - 2), ctx);

			emit(ARM_MOV_R(ARM_R0, r_skb), ctx);
			/* r_off is r1 */
			emit_mov_i(ARM_R3, (u32)jit_get_skb_b, ctx);
			emit_blx_r(ARM_R3, ctx);
			/* check the return value of skb_copy_bits */
			emit(ARM_CMP_I(ARM_R1, 0), ctx);
			emit_err_ret(ARM_COND_NE, ctx);

			emit(ARM_AND_I(r_X, ARM_R0, 0x00f), ctx);
			emit(ARM_LSL_I(r_X, r_X, 2), ctx);
			break;
		case BPF_S_ST:
			ctx->seen |= SEEN_MEM_WORD(k);
			emit(ARM_STR_I(r_A, ARM_SP, SCRATCH_OFF(k)), ctx);
			break;
		case BPF_S_STX:
			update_on_xread(ctx);
			ctx->seen |= SEEN_MEM_WORD(k);
			emit(ARM_STR_I(r_X, ARM_SP, SCRATCH_OFF(k)), ctx);
			break;
		case BPF_S_ALU_ADD_K:
			/* A += K */
			OP_IMM3(ARM_ADD, r_A, r_A, k, ctx);
			break;
		case BPF_S_ALU_ADD_X:
			update_on_xread(ctx);
			emit(ARM_ADD_R(r_A, r_A, r_X), ctx);
			break;
		case BPF_S_ALU_SUB_K:
			/* A -= K */
			OP_IMM3(ARM_SUB, r_A, r_A, k, ctx);
			break;
		case BPF_S_ALU_SUB_X:
			update_on_xread(ctx);
			emit(ARM_SUB_R(r_A, r_A, r_X), ctx);
			break;
		case BPF_S_ALU_MUL_K:
			/* A *= K */
			emit_mov_i(r_scratch, k, ctx);
			emit(ARM_MUL(r_A, r_A, r_scratch), ctx);
			break;
		case BPF_S_ALU_MUL_X:
			update_on_xread(ctx);
			emit(ARM_MUL(r_A, r_A, r_X), ctx);
			break;
		case BPF_S_ALU_DIV_K:
			/* current k == reciprocal_value(userspace k) */
			emit_mov_i(r_scratch, k, ctx);
			/* A = top 32 bits of the product */
			emit(ARM_UMULL(r_scratch, r_A, r_A, r_scratch), ctx);
			break;
		case BPF_S_ALU_DIV_X:
			update_on_xread(ctx);
			emit(ARM_CMP_I(r_X, 0), ctx);
			emit_err_ret(ARM_COND_EQ, ctx);
			emit_udiv(r_A, r_A, r_X, ctx);
			break;
		case BPF_S_ALU_OR_K:
			/* A |= K */
			OP_IMM3(ARM_ORR, r_A, r_A, k, ctx);
			break;
		case BPF_S_ALU_OR_X:
			update_on_xread(ctx);
			emit(ARM_ORR_R(r_A, r_A, r_X), ctx);
			break;
		case BPF_S_ALU_XOR_K:
			/* A ^= K; */
			OP_IMM3(ARM_EOR, r_A, r_A, k, ctx);
			break;
		case BPF_S_ANC_ALU_XOR_X:
		case BPF_S_ALU_XOR_X:
			/* A ^= X */
			update_on_xread(ctx);
			emit(ARM_EOR_R(r_A, r_A, r_X), ctx);
			break;
		case BPF_S_ALU_AND_K:
			/* A &= K */
			OP_IMM3(ARM_AND, r_A, r_A, k, ctx);
			break;
		case BPF_S_ALU_AND_X:
			update_on_xread(ctx);
			emit(ARM_AND_R(r_A, r_A, r_X), ctx);
			break;
		case BPF_S_ALU_LSH_K:
			if (unlikely(k > 31))
				return -1;
			emit(ARM_LSL_I(r_A, r_A, k), ctx);
			break;
		case BPF_S_ALU_LSH_X:
			update_on_xread(ctx);
			emit(ARM_LSL_R(r_A, r_A, r_X), ctx);
			break;
		case BPF_S_ALU_RSH_K:
			if (unlikely(k > 31))
				return -1;
			emit(ARM_LSR_I(r_A, r_A, k), ctx);
			break;
		case BPF_S_ALU_RSH_X:
			update_on_xread(ctx);
			emit(ARM_LSR_R(r_A, r_A, r_X), ctx);
			break;
		case BPF_S_ALU_NEG:
			/* A = -A */
			emit(ARM_RSB_I(r_A, r_A, 0), ctx);
			break;
		case BPF_S_JMP_JA:
			/* pc += K */
			emit(ARM_B(b_imm(i + k + 1, ctx)), ctx);
			break;
		case BPF_S_JMP_JEQ_K:
			/* pc += (A == K) ? pc->jt : pc->jf */
			condt  = ARM_COND_EQ;
			goto cmp_imm;
		case BPF_S_JMP_JGT_K:
			/* pc += (A > K) ? pc->jt : pc->jf */
			condt  = ARM_COND_HI;
			goto cmp_imm;
		case BPF_S_JMP_JGE_K:
			/* pc += (A >= K) ? pc->jt : pc->jf */
			condt  = ARM_COND_HS;
cmp_imm:
			imm12 = imm8m(k);
			if (imm12 < 0) {
				emit_mov_i_no8m(r_scratch, k, ctx);
				emit(ARM_CMP_R(r_A, r_scratch), ctx);
			} else {
				emit(ARM_CMP_I(r_A, imm12), ctx);
			}
cond_jump:
			if (inst->jt)
				_emit(condt, ARM_B(b_imm(i + inst->jt + 1,
						   ctx)), ctx);
			if (inst->jf)
				_emit(condt ^ 1, ARM_B(b_imm(i + inst->jf + 1,
							     ctx)), ctx);
			break;
		case BPF_S_JMP_JEQ_X:
			/* pc += (A == X) ? pc->jt : pc->jf */
			condt   = ARM_COND_EQ;
			goto cmp_x;
		case BPF_S_JMP_JGT_X:
			/* pc += (A > X) ? pc->jt : pc->jf */
			condt   = ARM_COND_HI;
			goto cmp_x;
		case BPF_S_JMP_JGE_X:
			/* pc += (A >= X) ? pc->jt : pc->jf */
			condt   = ARM_COND_CS;
cmp_x:
			update_on_xread(ctx);
			emit(ARM_CMP_R(r_A, r_X), ctx);
			goto cond_jump;
		case BPF_S_JMP_JSET_K:
			/* pc += (A & K) ? pc->jt : pc->jf */
			condt  = ARM_COND_NE;
			/* not set iff all zeroes iff Z==1 iff EQ */

			imm12 = imm8m(k);
			if (imm12 < 0) {
				emit_mov_i_no8m(r_scratch, k, ctx);
				emit(ARM_TST_R(r_A, r_scratch), ctx);
			} else {
				emit(ARM_TST_I(r_A, imm12), ctx);
			}
			goto cond_jump;
		case BPF_S_JMP_JSET_X:
			/* pc += (A & X) ? pc->jt : pc->jf */
			update_on_xread(ctx);
			condt  = ARM_COND_NE;
			emit(ARM_TST_R(r_A, r_X), ctx);
			goto cond_jump;
		case BPF_S_RET_A:
			emit(ARM_MOV_R(ARM_R0, r_A), ctx);
			goto b_epilogue;
		case BPF_S_RET_K:
			if ((k == 0) && (ctx->ret0_fp_idx < 0))
				ctx->ret0_fp_idx = i;
			emit_mov_i(ARM_R0, k, ctx);
b_epilogue:
			if (i != ctx->skf->len - 1)
				emit(ARM_B(b_imm(prog->len, ctx)), ctx);
			break;
		case BPF_S_MISC_TAX:
			/* X = A */
			ctx->seen |= SEEN_X;
			emit(ARM_MOV_R(r_X, r_A), ctx);
			break;
		case BPF_S_MISC_TXA:
			/* A = X */
			update_on_xread(ctx);
			emit(ARM_MOV_R(r_A, r_X), ctx);
			break;
		case BPF_S_ANC_PROTOCOL:
			/* A = ntohs(skb->protocol) */
			ctx->seen |= SEEN_SKB;
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
						  protocol) != 2);
			off = offsetof(struct sk_buff, protocol);
			emit(ARM_LDRH_I(r_scratch, r_skb, off), ctx);
			emit_swap16(r_A, r_scratch, ctx);
			break;
		case BPF_S_ANC_CPU:
			/* r_scratch = current_thread_info() */
			OP_IMM3(ARM_BIC, r_scratch, ARM_SP, THREAD_SIZE - 1, ctx);
			/* A = current_thread_info()->cpu */
			BUILD_BUG_ON(FIELD_SIZEOF(struct thread_info, cpu) != 4);
			off = offsetof(struct thread_info, cpu);
			emit(ARM_LDR_I(r_A, r_scratch, off), ctx);
			break;
		case BPF_S_ANC_IFINDEX:
			/* A = skb->dev->ifindex */
			ctx->seen |= SEEN_SKB;
			off = offsetof(struct sk_buff, dev);
			emit(ARM_LDR_I(r_scratch, r_skb, off), ctx);

			emit(ARM_CMP_I(r_scratch, 0), ctx);
			emit_err_ret(ARM_COND_EQ, ctx);

			BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
						  ifindex) != 4);
			off = offsetof(struct net_device, ifindex);
			emit(ARM_LDR_I(r_A, r_scratch, off), ctx);
			break;
		case BPF_S_ANC_MARK:
			ctx->seen |= SEEN_SKB;
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
			off = offsetof(struct sk_buff, mark);
			emit(ARM_LDR_I(r_A, r_skb, off), ctx);
			break;
		case BPF_S_ANC_RXHASH:
			ctx->seen |= SEEN_SKB;
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, rxhash) != 4);
			off = offsetof(struct sk_buff, rxhash);
			emit(ARM_LDR_I(r_A, r_skb, off), ctx);
			break;
		case BPF_S_ANC_VLAN_TAG:
		case BPF_S_ANC_VLAN_TAG_PRESENT:
			ctx->seen |= SEEN_SKB;
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
			off = offsetof(struct sk_buff, vlan_tci);
			emit(ARM_LDRH_I(r_A, r_skb, off), ctx);
			if (inst->code == BPF_S_ANC_VLAN_TAG)
				OP_IMM3(ARM_AND, r_A, r_A, VLAN_VID_MASK, ctx);
			else
				OP_IMM3(ARM_AND, r_A, r_A, VLAN_TAG_PRESENT, ctx);
			break;
		case BPF_S_ANC_QUEUE:
			ctx->seen |= SEEN_SKB;
			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
						  queue_mapping) != 2);
			BUILD_BUG_ON(offsetof(struct sk_buff,
					      queue_mapping) > 0xff);
			off = offsetof(struct sk_buff, queue_mapping);
			emit(ARM_LDRH_I(r_A, r_skb, off), ctx);
			break;
		default:
			return -1;
		}
	}

	/* compute offsets only during the first pass */
	if (ctx->target == NULL)
		ctx->offsets[i] = ctx->idx * 4;

	return 0;
}


void bpf_jit_compile(struct sk_filter *fp)
{
	struct jit_ctx ctx;
	unsigned tmp_idx;
	unsigned alloc_size;

	if (!bpf_jit_enable)
		return;

	memset(&ctx, 0, sizeof(ctx));
	ctx.skf		= fp;
	ctx.ret0_fp_idx = -1;

	ctx.offsets = kzalloc(4 * (ctx.skf->len + 1), GFP_KERNEL);
	if (ctx.offsets == NULL)
		return;

	/* fake pass to fill in the ctx->seen */
	if (unlikely(build_body(&ctx)))
		goto out;

	tmp_idx = ctx.idx;
	build_prologue(&ctx);
	ctx.prologue_bytes = (ctx.idx - tmp_idx) * 4;

#if __LINUX_ARM_ARCH__ < 7
	tmp_idx = ctx.idx;
	build_epilogue(&ctx);
	ctx.epilogue_bytes = (ctx.idx - tmp_idx) * 4;

	ctx.idx += ctx.imm_count;
	if (ctx.imm_count) {
		ctx.imms = kzalloc(4 * ctx.imm_count, GFP_KERNEL);
		if (ctx.imms == NULL)
			goto out;
	}
#else
	/* there's nothing after the epilogue on ARMv7 */
	build_epilogue(&ctx);
#endif

	alloc_size = 4 * ctx.idx;
	ctx.target = module_alloc(alloc_size);
	if (unlikely(ctx.target == NULL))
		goto out;

	ctx.idx = 0;
	build_prologue(&ctx);
	build_body(&ctx);
	build_epilogue(&ctx);

	flush_icache_range((u32)ctx.target, (u32)(ctx.target + ctx.idx));

#if __LINUX_ARM_ARCH__ < 7
	if (ctx.imm_count)
		kfree(ctx.imms);
#endif

	if (bpf_jit_enable > 1)
		/* there are 2 passes here */
		bpf_jit_dump(fp->len, alloc_size, 2, ctx.target);

	fp->bpf_func = (void *)ctx.target;
out:
	kfree(ctx.offsets);
	return;
}

void bpf_jit_free(struct sk_filter *fp)
{
	if (fp->bpf_func != sk_run_filter)
		module_free(NULL, fp->bpf_func);
	kfree(fp);
}