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Merge remote-tracking branch 'overlayfs/overlayfs-next'
[deliverable/linux.git] / arch / arm / net / bpf_jit_32.c
1 /*
2 * Just-In-Time compiler for BPF filters on 32bit ARM
3 *
4 * Copyright (c) 2011 Mircea Gherzan <mgherzan@gmail.com>
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the
8 * Free Software Foundation; version 2 of the License.
9 */
10
11 #include <linux/bitops.h>
12 #include <linux/compiler.h>
13 #include <linux/errno.h>
14 #include <linux/filter.h>
15 #include <linux/netdevice.h>
16 #include <linux/string.h>
17 #include <linux/slab.h>
18 #include <linux/if_vlan.h>
19
20 #include <asm/cacheflush.h>
21 #include <asm/hwcap.h>
22 #include <asm/opcodes.h>
23
24 #include "bpf_jit_32.h"
25
26 /*
27 * ABI:
28 *
29 * r0 scratch register
30 * r4 BPF register A
31 * r5 BPF register X
32 * r6 pointer to the skb
33 * r7 skb->data
34 * r8 skb_headlen(skb)
35 */
36
37 #define r_scratch ARM_R0
38 /* r1-r3 are (also) used for the unaligned loads on the non-ARMv7 slowpath */
39 #define r_off ARM_R1
40 #define r_A ARM_R4
41 #define r_X ARM_R5
42 #define r_skb ARM_R6
43 #define r_skb_data ARM_R7
44 #define r_skb_hl ARM_R8
45
46 #define SCRATCH_SP_OFFSET 0
47 #define SCRATCH_OFF(k) (SCRATCH_SP_OFFSET + 4 * (k))
48
49 #define SEEN_MEM ((1 << BPF_MEMWORDS) - 1)
50 #define SEEN_MEM_WORD(k) (1 << (k))
51 #define SEEN_X (1 << BPF_MEMWORDS)
52 #define SEEN_CALL (1 << (BPF_MEMWORDS + 1))
53 #define SEEN_SKB (1 << (BPF_MEMWORDS + 2))
54 #define SEEN_DATA (1 << (BPF_MEMWORDS + 3))
55
56 #define FLAG_NEED_X_RESET (1 << 0)
57 #define FLAG_IMM_OVERFLOW (1 << 1)
58
59 struct jit_ctx {
60 const struct bpf_prog *skf;
61 unsigned idx;
62 unsigned prologue_bytes;
63 int ret0_fp_idx;
64 u32 seen;
65 u32 flags;
66 u32 *offsets;
67 u32 *target;
68 #if __LINUX_ARM_ARCH__ < 7
69 u16 epilogue_bytes;
70 u16 imm_count;
71 u32 *imms;
72 #endif
73 };
74
75 int bpf_jit_enable __read_mostly;
76
77 static inline int call_neg_helper(struct sk_buff *skb, int offset, void *ret,
78 unsigned int size)
79 {
80 void *ptr = bpf_internal_load_pointer_neg_helper(skb, offset, size);
81
82 if (!ptr)
83 return -EFAULT;
84 memcpy(ret, ptr, size);
85 return 0;
86 }
87
88 static u64 jit_get_skb_b(struct sk_buff *skb, int offset)
89 {
90 u8 ret;
91 int err;
92
93 if (offset < 0)
94 err = call_neg_helper(skb, offset, &ret, 1);
95 else
96 err = skb_copy_bits(skb, offset, &ret, 1);
97
98 return (u64)err << 32 | ret;
99 }
100
101 static u64 jit_get_skb_h(struct sk_buff *skb, int offset)
102 {
103 u16 ret;
104 int err;
105
106 if (offset < 0)
107 err = call_neg_helper(skb, offset, &ret, 2);
108 else
109 err = skb_copy_bits(skb, offset, &ret, 2);
110
111 return (u64)err << 32 | ntohs(ret);
112 }
113
114 static u64 jit_get_skb_w(struct sk_buff *skb, int offset)
115 {
116 u32 ret;
117 int err;
118
119 if (offset < 0)
120 err = call_neg_helper(skb, offset, &ret, 4);
121 else
122 err = skb_copy_bits(skb, offset, &ret, 4);
123
124 return (u64)err << 32 | ntohl(ret);
125 }
126
127 /*
128 * Wrappers which handle both OABI and EABI and assures Thumb2 interworking
129 * (where the assembly routines like __aeabi_uidiv could cause problems).
130 */
131 static u32 jit_udiv(u32 dividend, u32 divisor)
132 {
133 return dividend / divisor;
134 }
135
136 static u32 jit_mod(u32 dividend, u32 divisor)
137 {
138 return dividend % divisor;
139 }
140
141 static inline void _emit(int cond, u32 inst, struct jit_ctx *ctx)
142 {
143 inst |= (cond << 28);
144 inst = __opcode_to_mem_arm(inst);
145
146 if (ctx->target != NULL)
147 ctx->target[ctx->idx] = inst;
148
149 ctx->idx++;
150 }
151
152 /*
153 * Emit an instruction that will be executed unconditionally.
154 */
155 static inline void emit(u32 inst, struct jit_ctx *ctx)
156 {
157 _emit(ARM_COND_AL, inst, ctx);
158 }
159
160 static u16 saved_regs(struct jit_ctx *ctx)
161 {
162 u16 ret = 0;
163
164 if ((ctx->skf->len > 1) ||
165 (ctx->skf->insns[0].code == (BPF_RET | BPF_A)))
166 ret |= 1 << r_A;
167
168 #ifdef CONFIG_FRAME_POINTER
169 ret |= (1 << ARM_FP) | (1 << ARM_IP) | (1 << ARM_LR) | (1 << ARM_PC);
170 #else
171 if (ctx->seen & SEEN_CALL)
172 ret |= 1 << ARM_LR;
173 #endif
174 if (ctx->seen & (SEEN_DATA | SEEN_SKB))
175 ret |= 1 << r_skb;
176 if (ctx->seen & SEEN_DATA)
177 ret |= (1 << r_skb_data) | (1 << r_skb_hl);
178 if (ctx->seen & SEEN_X)
179 ret |= 1 << r_X;
180
181 return ret;
182 }
183
184 static inline int mem_words_used(struct jit_ctx *ctx)
185 {
186 /* yes, we do waste some stack space IF there are "holes" in the set" */
187 return fls(ctx->seen & SEEN_MEM);
188 }
189
190 static void jit_fill_hole(void *area, unsigned int size)
191 {
192 u32 *ptr;
193 /* We are guaranteed to have aligned memory. */
194 for (ptr = area; size >= sizeof(u32); size -= sizeof(u32))
195 *ptr++ = __opcode_to_mem_arm(ARM_INST_UDF);
196 }
197
198 static void build_prologue(struct jit_ctx *ctx)
199 {
200 u16 reg_set = saved_regs(ctx);
201 u16 off;
202
203 #ifdef CONFIG_FRAME_POINTER
204 emit(ARM_MOV_R(ARM_IP, ARM_SP), ctx);
205 emit(ARM_PUSH(reg_set), ctx);
206 emit(ARM_SUB_I(ARM_FP, ARM_IP, 4), ctx);
207 #else
208 if (reg_set)
209 emit(ARM_PUSH(reg_set), ctx);
210 #endif
211
212 if (ctx->seen & (SEEN_DATA | SEEN_SKB))
213 emit(ARM_MOV_R(r_skb, ARM_R0), ctx);
214
215 if (ctx->seen & SEEN_DATA) {
216 off = offsetof(struct sk_buff, data);
217 emit(ARM_LDR_I(r_skb_data, r_skb, off), ctx);
218 /* headlen = len - data_len */
219 off = offsetof(struct sk_buff, len);
220 emit(ARM_LDR_I(r_skb_hl, r_skb, off), ctx);
221 off = offsetof(struct sk_buff, data_len);
222 emit(ARM_LDR_I(r_scratch, r_skb, off), ctx);
223 emit(ARM_SUB_R(r_skb_hl, r_skb_hl, r_scratch), ctx);
224 }
225
226 if (ctx->flags & FLAG_NEED_X_RESET)
227 emit(ARM_MOV_I(r_X, 0), ctx);
228
229 /* do not leak kernel data to userspace */
230 if (bpf_needs_clear_a(&ctx->skf->insns[0]))
231 emit(ARM_MOV_I(r_A, 0), ctx);
232
233 /* stack space for the BPF_MEM words */
234 if (ctx->seen & SEEN_MEM)
235 emit(ARM_SUB_I(ARM_SP, ARM_SP, mem_words_used(ctx) * 4), ctx);
236 }
237
238 static void build_epilogue(struct jit_ctx *ctx)
239 {
240 u16 reg_set = saved_regs(ctx);
241
242 if (ctx->seen & SEEN_MEM)
243 emit(ARM_ADD_I(ARM_SP, ARM_SP, mem_words_used(ctx) * 4), ctx);
244
245 reg_set &= ~(1 << ARM_LR);
246
247 #ifdef CONFIG_FRAME_POINTER
248 /* the first instruction of the prologue was: mov ip, sp */
249 reg_set &= ~(1 << ARM_IP);
250 reg_set |= (1 << ARM_SP);
251 emit(ARM_LDM(ARM_SP, reg_set), ctx);
252 #else
253 if (reg_set) {
254 if (ctx->seen & SEEN_CALL)
255 reg_set |= 1 << ARM_PC;
256 emit(ARM_POP(reg_set), ctx);
257 }
258
259 if (!(ctx->seen & SEEN_CALL))
260 emit(ARM_BX(ARM_LR), ctx);
261 #endif
262 }
263
264 static int16_t imm8m(u32 x)
265 {
266 u32 rot;
267
268 for (rot = 0; rot < 16; rot++)
269 if ((x & ~ror32(0xff, 2 * rot)) == 0)
270 return rol32(x, 2 * rot) | (rot << 8);
271
272 return -1;
273 }
274
275 #if __LINUX_ARM_ARCH__ < 7
276
277 static u16 imm_offset(u32 k, struct jit_ctx *ctx)
278 {
279 unsigned i = 0, offset;
280 u16 imm;
281
282 /* on the "fake" run we just count them (duplicates included) */
283 if (ctx->target == NULL) {
284 ctx->imm_count++;
285 return 0;
286 }
287
288 while ((i < ctx->imm_count) && ctx->imms[i]) {
289 if (ctx->imms[i] == k)
290 break;
291 i++;
292 }
293
294 if (ctx->imms[i] == 0)
295 ctx->imms[i] = k;
296
297 /* constants go just after the epilogue */
298 offset = ctx->offsets[ctx->skf->len];
299 offset += ctx->prologue_bytes;
300 offset += ctx->epilogue_bytes;
301 offset += i * 4;
302
303 ctx->target[offset / 4] = k;
304
305 /* PC in ARM mode == address of the instruction + 8 */
306 imm = offset - (8 + ctx->idx * 4);
307
308 if (imm & ~0xfff) {
309 /*
310 * literal pool is too far, signal it into flags. we
311 * can only detect it on the second pass unfortunately.
312 */
313 ctx->flags |= FLAG_IMM_OVERFLOW;
314 return 0;
315 }
316
317 return imm;
318 }
319
320 #endif /* __LINUX_ARM_ARCH__ */
321
322 /*
323 * Move an immediate that's not an imm8m to a core register.
324 */
325 static inline void emit_mov_i_no8m(int rd, u32 val, struct jit_ctx *ctx)
326 {
327 #if __LINUX_ARM_ARCH__ < 7
328 emit(ARM_LDR_I(rd, ARM_PC, imm_offset(val, ctx)), ctx);
329 #else
330 emit(ARM_MOVW(rd, val & 0xffff), ctx);
331 if (val > 0xffff)
332 emit(ARM_MOVT(rd, val >> 16), ctx);
333 #endif
334 }
335
336 static inline void emit_mov_i(int rd, u32 val, struct jit_ctx *ctx)
337 {
338 int imm12 = imm8m(val);
339
340 if (imm12 >= 0)
341 emit(ARM_MOV_I(rd, imm12), ctx);
342 else
343 emit_mov_i_no8m(rd, val, ctx);
344 }
345
346 #if __LINUX_ARM_ARCH__ < 6
347
348 static void emit_load_be32(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx)
349 {
350 _emit(cond, ARM_LDRB_I(ARM_R3, r_addr, 1), ctx);
351 _emit(cond, ARM_LDRB_I(ARM_R1, r_addr, 0), ctx);
352 _emit(cond, ARM_LDRB_I(ARM_R2, r_addr, 3), ctx);
353 _emit(cond, ARM_LSL_I(ARM_R3, ARM_R3, 16), ctx);
354 _emit(cond, ARM_LDRB_I(ARM_R0, r_addr, 2), ctx);
355 _emit(cond, ARM_ORR_S(ARM_R3, ARM_R3, ARM_R1, SRTYPE_LSL, 24), ctx);
356 _emit(cond, ARM_ORR_R(ARM_R3, ARM_R3, ARM_R2), ctx);
357 _emit(cond, ARM_ORR_S(r_res, ARM_R3, ARM_R0, SRTYPE_LSL, 8), ctx);
358 }
359
360 static void emit_load_be16(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx)
361 {
362 _emit(cond, ARM_LDRB_I(ARM_R1, r_addr, 0), ctx);
363 _emit(cond, ARM_LDRB_I(ARM_R2, r_addr, 1), ctx);
364 _emit(cond, ARM_ORR_S(r_res, ARM_R2, ARM_R1, SRTYPE_LSL, 8), ctx);
365 }
366
367 static inline void emit_swap16(u8 r_dst, u8 r_src, struct jit_ctx *ctx)
368 {
369 /* r_dst = (r_src << 8) | (r_src >> 8) */
370 emit(ARM_LSL_I(ARM_R1, r_src, 8), ctx);
371 emit(ARM_ORR_S(r_dst, ARM_R1, r_src, SRTYPE_LSR, 8), ctx);
372
373 /*
374 * we need to mask out the bits set in r_dst[23:16] due to
375 * the first shift instruction.
376 *
377 * note that 0x8ff is the encoded immediate 0x00ff0000.
378 */
379 emit(ARM_BIC_I(r_dst, r_dst, 0x8ff), ctx);
380 }
381
382 #else /* ARMv6+ */
383
384 static void emit_load_be32(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx)
385 {
386 _emit(cond, ARM_LDR_I(r_res, r_addr, 0), ctx);
387 #ifdef __LITTLE_ENDIAN
388 _emit(cond, ARM_REV(r_res, r_res), ctx);
389 #endif
390 }
391
392 static void emit_load_be16(u8 cond, u8 r_res, u8 r_addr, struct jit_ctx *ctx)
393 {
394 _emit(cond, ARM_LDRH_I(r_res, r_addr, 0), ctx);
395 #ifdef __LITTLE_ENDIAN
396 _emit(cond, ARM_REV16(r_res, r_res), ctx);
397 #endif
398 }
399
400 static inline void emit_swap16(u8 r_dst __maybe_unused,
401 u8 r_src __maybe_unused,
402 struct jit_ctx *ctx __maybe_unused)
403 {
404 #ifdef __LITTLE_ENDIAN
405 emit(ARM_REV16(r_dst, r_src), ctx);
406 #endif
407 }
408
409 #endif /* __LINUX_ARM_ARCH__ < 6 */
410
411
412 /* Compute the immediate value for a PC-relative branch. */
413 static inline u32 b_imm(unsigned tgt, struct jit_ctx *ctx)
414 {
415 u32 imm;
416
417 if (ctx->target == NULL)
418 return 0;
419 /*
420 * BPF allows only forward jumps and the offset of the target is
421 * still the one computed during the first pass.
422 */
423 imm = ctx->offsets[tgt] + ctx->prologue_bytes - (ctx->idx * 4 + 8);
424
425 return imm >> 2;
426 }
427
428 #define OP_IMM3(op, r1, r2, imm_val, ctx) \
429 do { \
430 imm12 = imm8m(imm_val); \
431 if (imm12 < 0) { \
432 emit_mov_i_no8m(r_scratch, imm_val, ctx); \
433 emit(op ## _R((r1), (r2), r_scratch), ctx); \
434 } else { \
435 emit(op ## _I((r1), (r2), imm12), ctx); \
436 } \
437 } while (0)
438
439 static inline void emit_err_ret(u8 cond, struct jit_ctx *ctx)
440 {
441 if (ctx->ret0_fp_idx >= 0) {
442 _emit(cond, ARM_B(b_imm(ctx->ret0_fp_idx, ctx)), ctx);
443 /* NOP to keep the size constant between passes */
444 emit(ARM_MOV_R(ARM_R0, ARM_R0), ctx);
445 } else {
446 _emit(cond, ARM_MOV_I(ARM_R0, 0), ctx);
447 _emit(cond, ARM_B(b_imm(ctx->skf->len, ctx)), ctx);
448 }
449 }
450
451 static inline void emit_blx_r(u8 tgt_reg, struct jit_ctx *ctx)
452 {
453 #if __LINUX_ARM_ARCH__ < 5
454 emit(ARM_MOV_R(ARM_LR, ARM_PC), ctx);
455
456 if (elf_hwcap & HWCAP_THUMB)
457 emit(ARM_BX(tgt_reg), ctx);
458 else
459 emit(ARM_MOV_R(ARM_PC, tgt_reg), ctx);
460 #else
461 emit(ARM_BLX_R(tgt_reg), ctx);
462 #endif
463 }
464
465 static inline void emit_udivmod(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx,
466 int bpf_op)
467 {
468 #if __LINUX_ARM_ARCH__ == 7
469 if (elf_hwcap & HWCAP_IDIVA) {
470 if (bpf_op == BPF_DIV)
471 emit(ARM_UDIV(rd, rm, rn), ctx);
472 else {
473 emit(ARM_UDIV(ARM_R3, rm, rn), ctx);
474 emit(ARM_MLS(rd, rn, ARM_R3, rm), ctx);
475 }
476 return;
477 }
478 #endif
479
480 /*
481 * For BPF_ALU | BPF_DIV | BPF_K instructions, rm is ARM_R4
482 * (r_A) and rn is ARM_R0 (r_scratch) so load rn first into
483 * ARM_R1 to avoid accidentally overwriting ARM_R0 with rm
484 * before using it as a source for ARM_R1.
485 *
486 * For BPF_ALU | BPF_DIV | BPF_X rm is ARM_R4 (r_A) and rn is
487 * ARM_R5 (r_X) so there is no particular register overlap
488 * issues.
489 */
490 if (rn != ARM_R1)
491 emit(ARM_MOV_R(ARM_R1, rn), ctx);
492 if (rm != ARM_R0)
493 emit(ARM_MOV_R(ARM_R0, rm), ctx);
494
495 ctx->seen |= SEEN_CALL;
496 emit_mov_i(ARM_R3, bpf_op == BPF_DIV ? (u32)jit_udiv : (u32)jit_mod,
497 ctx);
498 emit_blx_r(ARM_R3, ctx);
499
500 if (rd != ARM_R0)
501 emit(ARM_MOV_R(rd, ARM_R0), ctx);
502 }
503
504 static inline void update_on_xread(struct jit_ctx *ctx)
505 {
506 if (!(ctx->seen & SEEN_X))
507 ctx->flags |= FLAG_NEED_X_RESET;
508
509 ctx->seen |= SEEN_X;
510 }
511
512 static int build_body(struct jit_ctx *ctx)
513 {
514 void *load_func[] = {jit_get_skb_b, jit_get_skb_h, jit_get_skb_w};
515 const struct bpf_prog *prog = ctx->skf;
516 const struct sock_filter *inst;
517 unsigned i, load_order, off, condt;
518 int imm12;
519 u32 k;
520
521 for (i = 0; i < prog->len; i++) {
522 u16 code;
523
524 inst = &(prog->insns[i]);
525 /* K as an immediate value operand */
526 k = inst->k;
527 code = bpf_anc_helper(inst);
528
529 /* compute offsets only in the fake pass */
530 if (ctx->target == NULL)
531 ctx->offsets[i] = ctx->idx * 4;
532
533 switch (code) {
534 case BPF_LD | BPF_IMM:
535 emit_mov_i(r_A, k, ctx);
536 break;
537 case BPF_LD | BPF_W | BPF_LEN:
538 ctx->seen |= SEEN_SKB;
539 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
540 emit(ARM_LDR_I(r_A, r_skb,
541 offsetof(struct sk_buff, len)), ctx);
542 break;
543 case BPF_LD | BPF_MEM:
544 /* A = scratch[k] */
545 ctx->seen |= SEEN_MEM_WORD(k);
546 emit(ARM_LDR_I(r_A, ARM_SP, SCRATCH_OFF(k)), ctx);
547 break;
548 case BPF_LD | BPF_W | BPF_ABS:
549 load_order = 2;
550 goto load;
551 case BPF_LD | BPF_H | BPF_ABS:
552 load_order = 1;
553 goto load;
554 case BPF_LD | BPF_B | BPF_ABS:
555 load_order = 0;
556 load:
557 emit_mov_i(r_off, k, ctx);
558 load_common:
559 ctx->seen |= SEEN_DATA | SEEN_CALL;
560
561 if (load_order > 0) {
562 emit(ARM_SUB_I(r_scratch, r_skb_hl,
563 1 << load_order), ctx);
564 emit(ARM_CMP_R(r_scratch, r_off), ctx);
565 condt = ARM_COND_GE;
566 } else {
567 emit(ARM_CMP_R(r_skb_hl, r_off), ctx);
568 condt = ARM_COND_HI;
569 }
570
571 /*
572 * test for negative offset, only if we are
573 * currently scheduled to take the fast
574 * path. this will update the flags so that
575 * the slowpath instruction are ignored if the
576 * offset is negative.
577 *
578 * for loard_order == 0 the HI condition will
579 * make loads at offset 0 take the slow path too.
580 */
581 _emit(condt, ARM_CMP_I(r_off, 0), ctx);
582
583 _emit(condt, ARM_ADD_R(r_scratch, r_off, r_skb_data),
584 ctx);
585
586 if (load_order == 0)
587 _emit(condt, ARM_LDRB_I(r_A, r_scratch, 0),
588 ctx);
589 else if (load_order == 1)
590 emit_load_be16(condt, r_A, r_scratch, ctx);
591 else if (load_order == 2)
592 emit_load_be32(condt, r_A, r_scratch, ctx);
593
594 _emit(condt, ARM_B(b_imm(i + 1, ctx)), ctx);
595
596 /* the slowpath */
597 emit_mov_i(ARM_R3, (u32)load_func[load_order], ctx);
598 emit(ARM_MOV_R(ARM_R0, r_skb), ctx);
599 /* the offset is already in R1 */
600 emit_blx_r(ARM_R3, ctx);
601 /* check the result of skb_copy_bits */
602 emit(ARM_CMP_I(ARM_R1, 0), ctx);
603 emit_err_ret(ARM_COND_NE, ctx);
604 emit(ARM_MOV_R(r_A, ARM_R0), ctx);
605 break;
606 case BPF_LD | BPF_W | BPF_IND:
607 load_order = 2;
608 goto load_ind;
609 case BPF_LD | BPF_H | BPF_IND:
610 load_order = 1;
611 goto load_ind;
612 case BPF_LD | BPF_B | BPF_IND:
613 load_order = 0;
614 load_ind:
615 update_on_xread(ctx);
616 OP_IMM3(ARM_ADD, r_off, r_X, k, ctx);
617 goto load_common;
618 case BPF_LDX | BPF_IMM:
619 ctx->seen |= SEEN_X;
620 emit_mov_i(r_X, k, ctx);
621 break;
622 case BPF_LDX | BPF_W | BPF_LEN:
623 ctx->seen |= SEEN_X | SEEN_SKB;
624 emit(ARM_LDR_I(r_X, r_skb,
625 offsetof(struct sk_buff, len)), ctx);
626 break;
627 case BPF_LDX | BPF_MEM:
628 ctx->seen |= SEEN_X | SEEN_MEM_WORD(k);
629 emit(ARM_LDR_I(r_X, ARM_SP, SCRATCH_OFF(k)), ctx);
630 break;
631 case BPF_LDX | BPF_B | BPF_MSH:
632 /* x = ((*(frame + k)) & 0xf) << 2; */
633 ctx->seen |= SEEN_X | SEEN_DATA | SEEN_CALL;
634 /* the interpreter should deal with the negative K */
635 if ((int)k < 0)
636 return -1;
637 /* offset in r1: we might have to take the slow path */
638 emit_mov_i(r_off, k, ctx);
639 emit(ARM_CMP_R(r_skb_hl, r_off), ctx);
640
641 /* load in r0: common with the slowpath */
642 _emit(ARM_COND_HI, ARM_LDRB_R(ARM_R0, r_skb_data,
643 ARM_R1), ctx);
644 /*
645 * emit_mov_i() might generate one or two instructions,
646 * the same holds for emit_blx_r()
647 */
648 _emit(ARM_COND_HI, ARM_B(b_imm(i + 1, ctx) - 2), ctx);
649
650 emit(ARM_MOV_R(ARM_R0, r_skb), ctx);
651 /* r_off is r1 */
652 emit_mov_i(ARM_R3, (u32)jit_get_skb_b, ctx);
653 emit_blx_r(ARM_R3, ctx);
654 /* check the return value of skb_copy_bits */
655 emit(ARM_CMP_I(ARM_R1, 0), ctx);
656 emit_err_ret(ARM_COND_NE, ctx);
657
658 emit(ARM_AND_I(r_X, ARM_R0, 0x00f), ctx);
659 emit(ARM_LSL_I(r_X, r_X, 2), ctx);
660 break;
661 case BPF_ST:
662 ctx->seen |= SEEN_MEM_WORD(k);
663 emit(ARM_STR_I(r_A, ARM_SP, SCRATCH_OFF(k)), ctx);
664 break;
665 case BPF_STX:
666 update_on_xread(ctx);
667 ctx->seen |= SEEN_MEM_WORD(k);
668 emit(ARM_STR_I(r_X, ARM_SP, SCRATCH_OFF(k)), ctx);
669 break;
670 case BPF_ALU | BPF_ADD | BPF_K:
671 /* A += K */
672 OP_IMM3(ARM_ADD, r_A, r_A, k, ctx);
673 break;
674 case BPF_ALU | BPF_ADD | BPF_X:
675 update_on_xread(ctx);
676 emit(ARM_ADD_R(r_A, r_A, r_X), ctx);
677 break;
678 case BPF_ALU | BPF_SUB | BPF_K:
679 /* A -= K */
680 OP_IMM3(ARM_SUB, r_A, r_A, k, ctx);
681 break;
682 case BPF_ALU | BPF_SUB | BPF_X:
683 update_on_xread(ctx);
684 emit(ARM_SUB_R(r_A, r_A, r_X), ctx);
685 break;
686 case BPF_ALU | BPF_MUL | BPF_K:
687 /* A *= K */
688 emit_mov_i(r_scratch, k, ctx);
689 emit(ARM_MUL(r_A, r_A, r_scratch), ctx);
690 break;
691 case BPF_ALU | BPF_MUL | BPF_X:
692 update_on_xread(ctx);
693 emit(ARM_MUL(r_A, r_A, r_X), ctx);
694 break;
695 case BPF_ALU | BPF_DIV | BPF_K:
696 if (k == 1)
697 break;
698 emit_mov_i(r_scratch, k, ctx);
699 emit_udivmod(r_A, r_A, r_scratch, ctx, BPF_DIV);
700 break;
701 case BPF_ALU | BPF_DIV | BPF_X:
702 update_on_xread(ctx);
703 emit(ARM_CMP_I(r_X, 0), ctx);
704 emit_err_ret(ARM_COND_EQ, ctx);
705 emit_udivmod(r_A, r_A, r_X, ctx, BPF_DIV);
706 break;
707 case BPF_ALU | BPF_MOD | BPF_K:
708 if (k == 1) {
709 emit_mov_i(r_A, 0, ctx);
710 break;
711 }
712 emit_mov_i(r_scratch, k, ctx);
713 emit_udivmod(r_A, r_A, r_scratch, ctx, BPF_MOD);
714 break;
715 case BPF_ALU | BPF_MOD | BPF_X:
716 update_on_xread(ctx);
717 emit(ARM_CMP_I(r_X, 0), ctx);
718 emit_err_ret(ARM_COND_EQ, ctx);
719 emit_udivmod(r_A, r_A, r_X, ctx, BPF_MOD);
720 break;
721 case BPF_ALU | BPF_OR | BPF_K:
722 /* A |= K */
723 OP_IMM3(ARM_ORR, r_A, r_A, k, ctx);
724 break;
725 case BPF_ALU | BPF_OR | BPF_X:
726 update_on_xread(ctx);
727 emit(ARM_ORR_R(r_A, r_A, r_X), ctx);
728 break;
729 case BPF_ALU | BPF_XOR | BPF_K:
730 /* A ^= K; */
731 OP_IMM3(ARM_EOR, r_A, r_A, k, ctx);
732 break;
733 case BPF_ANC | SKF_AD_ALU_XOR_X:
734 case BPF_ALU | BPF_XOR | BPF_X:
735 /* A ^= X */
736 update_on_xread(ctx);
737 emit(ARM_EOR_R(r_A, r_A, r_X), ctx);
738 break;
739 case BPF_ALU | BPF_AND | BPF_K:
740 /* A &= K */
741 OP_IMM3(ARM_AND, r_A, r_A, k, ctx);
742 break;
743 case BPF_ALU | BPF_AND | BPF_X:
744 update_on_xread(ctx);
745 emit(ARM_AND_R(r_A, r_A, r_X), ctx);
746 break;
747 case BPF_ALU | BPF_LSH | BPF_K:
748 if (unlikely(k > 31))
749 return -1;
750 emit(ARM_LSL_I(r_A, r_A, k), ctx);
751 break;
752 case BPF_ALU | BPF_LSH | BPF_X:
753 update_on_xread(ctx);
754 emit(ARM_LSL_R(r_A, r_A, r_X), ctx);
755 break;
756 case BPF_ALU | BPF_RSH | BPF_K:
757 if (unlikely(k > 31))
758 return -1;
759 if (k)
760 emit(ARM_LSR_I(r_A, r_A, k), ctx);
761 break;
762 case BPF_ALU | BPF_RSH | BPF_X:
763 update_on_xread(ctx);
764 emit(ARM_LSR_R(r_A, r_A, r_X), ctx);
765 break;
766 case BPF_ALU | BPF_NEG:
767 /* A = -A */
768 emit(ARM_RSB_I(r_A, r_A, 0), ctx);
769 break;
770 case BPF_JMP | BPF_JA:
771 /* pc += K */
772 emit(ARM_B(b_imm(i + k + 1, ctx)), ctx);
773 break;
774 case BPF_JMP | BPF_JEQ | BPF_K:
775 /* pc += (A == K) ? pc->jt : pc->jf */
776 condt = ARM_COND_EQ;
777 goto cmp_imm;
778 case BPF_JMP | BPF_JGT | BPF_K:
779 /* pc += (A > K) ? pc->jt : pc->jf */
780 condt = ARM_COND_HI;
781 goto cmp_imm;
782 case BPF_JMP | BPF_JGE | BPF_K:
783 /* pc += (A >= K) ? pc->jt : pc->jf */
784 condt = ARM_COND_HS;
785 cmp_imm:
786 imm12 = imm8m(k);
787 if (imm12 < 0) {
788 emit_mov_i_no8m(r_scratch, k, ctx);
789 emit(ARM_CMP_R(r_A, r_scratch), ctx);
790 } else {
791 emit(ARM_CMP_I(r_A, imm12), ctx);
792 }
793 cond_jump:
794 if (inst->jt)
795 _emit(condt, ARM_B(b_imm(i + inst->jt + 1,
796 ctx)), ctx);
797 if (inst->jf)
798 _emit(condt ^ 1, ARM_B(b_imm(i + inst->jf + 1,
799 ctx)), ctx);
800 break;
801 case BPF_JMP | BPF_JEQ | BPF_X:
802 /* pc += (A == X) ? pc->jt : pc->jf */
803 condt = ARM_COND_EQ;
804 goto cmp_x;
805 case BPF_JMP | BPF_JGT | BPF_X:
806 /* pc += (A > X) ? pc->jt : pc->jf */
807 condt = ARM_COND_HI;
808 goto cmp_x;
809 case BPF_JMP | BPF_JGE | BPF_X:
810 /* pc += (A >= X) ? pc->jt : pc->jf */
811 condt = ARM_COND_CS;
812 cmp_x:
813 update_on_xread(ctx);
814 emit(ARM_CMP_R(r_A, r_X), ctx);
815 goto cond_jump;
816 case BPF_JMP | BPF_JSET | BPF_K:
817 /* pc += (A & K) ? pc->jt : pc->jf */
818 condt = ARM_COND_NE;
819 /* not set iff all zeroes iff Z==1 iff EQ */
820
821 imm12 = imm8m(k);
822 if (imm12 < 0) {
823 emit_mov_i_no8m(r_scratch, k, ctx);
824 emit(ARM_TST_R(r_A, r_scratch), ctx);
825 } else {
826 emit(ARM_TST_I(r_A, imm12), ctx);
827 }
828 goto cond_jump;
829 case BPF_JMP | BPF_JSET | BPF_X:
830 /* pc += (A & X) ? pc->jt : pc->jf */
831 update_on_xread(ctx);
832 condt = ARM_COND_NE;
833 emit(ARM_TST_R(r_A, r_X), ctx);
834 goto cond_jump;
835 case BPF_RET | BPF_A:
836 emit(ARM_MOV_R(ARM_R0, r_A), ctx);
837 goto b_epilogue;
838 case BPF_RET | BPF_K:
839 if ((k == 0) && (ctx->ret0_fp_idx < 0))
840 ctx->ret0_fp_idx = i;
841 emit_mov_i(ARM_R0, k, ctx);
842 b_epilogue:
843 if (i != ctx->skf->len - 1)
844 emit(ARM_B(b_imm(prog->len, ctx)), ctx);
845 break;
846 case BPF_MISC | BPF_TAX:
847 /* X = A */
848 ctx->seen |= SEEN_X;
849 emit(ARM_MOV_R(r_X, r_A), ctx);
850 break;
851 case BPF_MISC | BPF_TXA:
852 /* A = X */
853 update_on_xread(ctx);
854 emit(ARM_MOV_R(r_A, r_X), ctx);
855 break;
856 case BPF_ANC | SKF_AD_PROTOCOL:
857 /* A = ntohs(skb->protocol) */
858 ctx->seen |= SEEN_SKB;
859 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
860 protocol) != 2);
861 off = offsetof(struct sk_buff, protocol);
862 emit(ARM_LDRH_I(r_scratch, r_skb, off), ctx);
863 emit_swap16(r_A, r_scratch, ctx);
864 break;
865 case BPF_ANC | SKF_AD_CPU:
866 /* r_scratch = current_thread_info() */
867 OP_IMM3(ARM_BIC, r_scratch, ARM_SP, THREAD_SIZE - 1, ctx);
868 /* A = current_thread_info()->cpu */
869 BUILD_BUG_ON(FIELD_SIZEOF(struct thread_info, cpu) != 4);
870 off = offsetof(struct thread_info, cpu);
871 emit(ARM_LDR_I(r_A, r_scratch, off), ctx);
872 break;
873 case BPF_ANC | SKF_AD_IFINDEX:
874 case BPF_ANC | SKF_AD_HATYPE:
875 /* A = skb->dev->ifindex */
876 /* A = skb->dev->type */
877 ctx->seen |= SEEN_SKB;
878 off = offsetof(struct sk_buff, dev);
879 emit(ARM_LDR_I(r_scratch, r_skb, off), ctx);
880
881 emit(ARM_CMP_I(r_scratch, 0), ctx);
882 emit_err_ret(ARM_COND_EQ, ctx);
883
884 BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
885 ifindex) != 4);
886 BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
887 type) != 2);
888
889 if (code == (BPF_ANC | SKF_AD_IFINDEX)) {
890 off = offsetof(struct net_device, ifindex);
891 emit(ARM_LDR_I(r_A, r_scratch, off), ctx);
892 } else {
893 /*
894 * offset of field "type" in "struct
895 * net_device" is above what can be
896 * used in the ldrh rd, [rn, #imm]
897 * instruction, so load the offset in
898 * a register and use ldrh rd, [rn, rm]
899 */
900 off = offsetof(struct net_device, type);
901 emit_mov_i(ARM_R3, off, ctx);
902 emit(ARM_LDRH_R(r_A, r_scratch, ARM_R3), ctx);
903 }
904 break;
905 case BPF_ANC | SKF_AD_MARK:
906 ctx->seen |= SEEN_SKB;
907 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
908 off = offsetof(struct sk_buff, mark);
909 emit(ARM_LDR_I(r_A, r_skb, off), ctx);
910 break;
911 case BPF_ANC | SKF_AD_RXHASH:
912 ctx->seen |= SEEN_SKB;
913 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);
914 off = offsetof(struct sk_buff, hash);
915 emit(ARM_LDR_I(r_A, r_skb, off), ctx);
916 break;
917 case BPF_ANC | SKF_AD_VLAN_TAG:
918 case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT:
919 ctx->seen |= SEEN_SKB;
920 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
921 off = offsetof(struct sk_buff, vlan_tci);
922 emit(ARM_LDRH_I(r_A, r_skb, off), ctx);
923 if (code == (BPF_ANC | SKF_AD_VLAN_TAG))
924 OP_IMM3(ARM_AND, r_A, r_A, ~VLAN_TAG_PRESENT, ctx);
925 else {
926 OP_IMM3(ARM_LSR, r_A, r_A, 12, ctx);
927 OP_IMM3(ARM_AND, r_A, r_A, 0x1, ctx);
928 }
929 break;
930 case BPF_ANC | SKF_AD_PKTTYPE:
931 ctx->seen |= SEEN_SKB;
932 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
933 __pkt_type_offset[0]) != 1);
934 off = PKT_TYPE_OFFSET();
935 emit(ARM_LDRB_I(r_A, r_skb, off), ctx);
936 emit(ARM_AND_I(r_A, r_A, PKT_TYPE_MAX), ctx);
937 #ifdef __BIG_ENDIAN_BITFIELD
938 emit(ARM_LSR_I(r_A, r_A, 5), ctx);
939 #endif
940 break;
941 case BPF_ANC | SKF_AD_QUEUE:
942 ctx->seen |= SEEN_SKB;
943 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
944 queue_mapping) != 2);
945 BUILD_BUG_ON(offsetof(struct sk_buff,
946 queue_mapping) > 0xff);
947 off = offsetof(struct sk_buff, queue_mapping);
948 emit(ARM_LDRH_I(r_A, r_skb, off), ctx);
949 break;
950 case BPF_ANC | SKF_AD_PAY_OFFSET:
951 ctx->seen |= SEEN_SKB | SEEN_CALL;
952
953 emit(ARM_MOV_R(ARM_R0, r_skb), ctx);
954 emit_mov_i(ARM_R3, (unsigned int)skb_get_poff, ctx);
955 emit_blx_r(ARM_R3, ctx);
956 emit(ARM_MOV_R(r_A, ARM_R0), ctx);
957 break;
958 case BPF_LDX | BPF_W | BPF_ABS:
959 /*
960 * load a 32bit word from struct seccomp_data.
961 * seccomp_check_filter() will already have checked
962 * that k is 32bit aligned and lies within the
963 * struct seccomp_data.
964 */
965 ctx->seen |= SEEN_SKB;
966 emit(ARM_LDR_I(r_A, r_skb, k), ctx);
967 break;
968 default:
969 return -1;
970 }
971
972 if (ctx->flags & FLAG_IMM_OVERFLOW)
973 /*
974 * this instruction generated an overflow when
975 * trying to access the literal pool, so
976 * delegate this filter to the kernel interpreter.
977 */
978 return -1;
979 }
980
981 /* compute offsets only during the first pass */
982 if (ctx->target == NULL)
983 ctx->offsets[i] = ctx->idx * 4;
984
985 return 0;
986 }
987
988
989 void bpf_jit_compile(struct bpf_prog *fp)
990 {
991 struct bpf_binary_header *header;
992 struct jit_ctx ctx;
993 unsigned tmp_idx;
994 unsigned alloc_size;
995 u8 *target_ptr;
996
997 if (!bpf_jit_enable)
998 return;
999
1000 memset(&ctx, 0, sizeof(ctx));
1001 ctx.skf = fp;
1002 ctx.ret0_fp_idx = -1;
1003
1004 ctx.offsets = kzalloc(4 * (ctx.skf->len + 1), GFP_KERNEL);
1005 if (ctx.offsets == NULL)
1006 return;
1007
1008 /* fake pass to fill in the ctx->seen */
1009 if (unlikely(build_body(&ctx)))
1010 goto out;
1011
1012 tmp_idx = ctx.idx;
1013 build_prologue(&ctx);
1014 ctx.prologue_bytes = (ctx.idx - tmp_idx) * 4;
1015
1016 #if __LINUX_ARM_ARCH__ < 7
1017 tmp_idx = ctx.idx;
1018 build_epilogue(&ctx);
1019 ctx.epilogue_bytes = (ctx.idx - tmp_idx) * 4;
1020
1021 ctx.idx += ctx.imm_count;
1022 if (ctx.imm_count) {
1023 ctx.imms = kzalloc(4 * ctx.imm_count, GFP_KERNEL);
1024 if (ctx.imms == NULL)
1025 goto out;
1026 }
1027 #else
1028 /* there's nothing after the epilogue on ARMv7 */
1029 build_epilogue(&ctx);
1030 #endif
1031 alloc_size = 4 * ctx.idx;
1032 header = bpf_jit_binary_alloc(alloc_size, &target_ptr,
1033 4, jit_fill_hole);
1034 if (header == NULL)
1035 goto out;
1036
1037 ctx.target = (u32 *) target_ptr;
1038 ctx.idx = 0;
1039
1040 build_prologue(&ctx);
1041 if (build_body(&ctx) < 0) {
1042 #if __LINUX_ARM_ARCH__ < 7
1043 if (ctx.imm_count)
1044 kfree(ctx.imms);
1045 #endif
1046 bpf_jit_binary_free(header);
1047 goto out;
1048 }
1049 build_epilogue(&ctx);
1050
1051 flush_icache_range((u32)header, (u32)(ctx.target + ctx.idx));
1052
1053 #if __LINUX_ARM_ARCH__ < 7
1054 if (ctx.imm_count)
1055 kfree(ctx.imms);
1056 #endif
1057
1058 if (bpf_jit_enable > 1)
1059 /* there are 2 passes here */
1060 bpf_jit_dump(fp->len, alloc_size, 2, ctx.target);
1061
1062 set_memory_ro((unsigned long)header, header->pages);
1063 fp->bpf_func = (void *)ctx.target;
1064 fp->jited = 1;
1065 out:
1066 kfree(ctx.offsets);
1067 return;
1068 }
1069
1070 void bpf_jit_free(struct bpf_prog *fp)
1071 {
1072 unsigned long addr = (unsigned long)fp->bpf_func & PAGE_MASK;
1073 struct bpf_binary_header *header = (void *)addr;
1074
1075 if (!fp->jited)
1076 goto free_filter;
1077
1078 set_memory_rw(addr, header->pages);
1079 bpf_jit_binary_free(header);
1080
1081 free_filter:
1082 bpf_prog_unlock_free(fp);
1083 }
Linux kernel - Deliverables
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