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1// SPDX-License-Identifier: GPL-2.0-only
2/* bpf_jit_comp.c: BPF JIT compiler
3 *
4 * Copyright 2011 Matt Evans <matt@ozlabs.org>, IBM Corporation
5 *
6 * Based on the x86 BPF compiler, by Eric Dumazet (eric.dumazet@gmail.com)
7 * Ported to ppc32 by Denis Kirjanov <kda@linux-powerpc.org>
8 */
9#include <linux/moduleloader.h>
10#include <asm/cacheflush.h>
11#include <asm/asm-compat.h>
12#include <linux/netdevice.h>
13#include <linux/filter.h>
14#include <linux/if_vlan.h>
15
16#include "bpf_jit32.h"
17
18static inline void bpf_flush_icache(void *start, void *end)
19{
20 smp_wmb();
21 flush_icache_range((unsigned long)start, (unsigned long)end);
22}
23
24static void bpf_jit_build_prologue(struct bpf_prog *fp, u32 *image,
25 struct codegen_context *ctx)
26{
27 int i;
28 const struct sock_filter *filter = fp->insns;
29
30 if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
31 /* Make stackframe */
32 if (ctx->seen & SEEN_DATAREF) {
33 /* If we call any helpers (for loads), save LR */
34 EMIT(PPC_INST_MFLR | __PPC_RT(R0));
35 PPC_BPF_STL(0, 1, PPC_LR_STKOFF);
36
37 /* Back up non-volatile regs. */
38 PPC_BPF_STL(r_D, 1, -(REG_SZ*(32-r_D)));
39 PPC_BPF_STL(r_HL, 1, -(REG_SZ*(32-r_HL)));
40 }
41 if (ctx->seen & SEEN_MEM) {
42 /*
43 * Conditionally save regs r15-r31 as some will be used
44 * for M[] data.
45 */
46 for (i = r_M; i < (r_M+16); i++) {
47 if (ctx->seen & (1 << (i-r_M)))
48 PPC_BPF_STL(i, 1, -(REG_SZ*(32-i)));
49 }
50 }
51 PPC_BPF_STLU(1, 1, -BPF_PPC_STACKFRAME);
52 }
53
54 if (ctx->seen & SEEN_DATAREF) {
55 /*
56 * If this filter needs to access skb data,
57 * prepare r_D and r_HL:
58 * r_HL = skb->len - skb->data_len
59 * r_D = skb->data
60 */
61 PPC_LWZ_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
62 data_len));
63 PPC_LWZ_OFFS(r_HL, r_skb, offsetof(struct sk_buff, len));
64 PPC_SUB(r_HL, r_HL, r_scratch1);
65 PPC_LL_OFFS(r_D, r_skb, offsetof(struct sk_buff, data));
66 }
67
68 if (ctx->seen & SEEN_XREG) {
69 /*
70 * TODO: Could also detect whether first instr. sets X and
71 * avoid this (as below, with A).
72 */
73 PPC_LI(r_X, 0);
74 }
75
76 /* make sure we dont leak kernel information to user */
77 if (bpf_needs_clear_a(&filter[0]))
78 PPC_LI(r_A, 0);
79}
80
81static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
82{
83 int i;
84
85 if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
86 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
87 if (ctx->seen & SEEN_DATAREF) {
88 PPC_BPF_LL(0, 1, PPC_LR_STKOFF);
89 PPC_MTLR(0);
90 PPC_BPF_LL(r_D, 1, -(REG_SZ*(32-r_D)));
91 PPC_BPF_LL(r_HL, 1, -(REG_SZ*(32-r_HL)));
92 }
93 if (ctx->seen & SEEN_MEM) {
94 /* Restore any saved non-vol registers */
95 for (i = r_M; i < (r_M+16); i++) {
96 if (ctx->seen & (1 << (i-r_M)))
97 PPC_BPF_LL(i, 1, -(REG_SZ*(32-i)));
98 }
99 }
100 }
101 /* The RETs have left a return value in R3. */
102
103 PPC_BLR();
104}
105
106#define CHOOSE_LOAD_FUNC(K, func) \
107 ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
108
109/* Assemble the body code between the prologue & epilogue. */
110static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image,
111 struct codegen_context *ctx,
112 unsigned int *addrs)
113{
114 const struct sock_filter *filter = fp->insns;
115 int flen = fp->len;
116 u8 *func;
117 unsigned int true_cond;
118 int i;
119
120 /* Start of epilogue code */
121 unsigned int exit_addr = addrs[flen];
122
123 for (i = 0; i < flen; i++) {
124 unsigned int K = filter[i].k;
125 u16 code = bpf_anc_helper(&filter[i]);
126
127 /*
128 * addrs[] maps a BPF bytecode address into a real offset from
129 * the start of the body code.
130 */
131 addrs[i] = ctx->idx * 4;
132
133 switch (code) {
134 /*** ALU ops ***/
135 case BPF_ALU | BPF_ADD | BPF_X: /* A += X; */
136 ctx->seen |= SEEN_XREG;
137 PPC_ADD(r_A, r_A, r_X);
138 break;
139 case BPF_ALU | BPF_ADD | BPF_K: /* A += K; */
140 if (!K)
141 break;
142 PPC_ADDI(r_A, r_A, IMM_L(K));
143 if (K >= 32768)
144 PPC_ADDIS(r_A, r_A, IMM_HA(K));
145 break;
146 case BPF_ALU | BPF_SUB | BPF_X: /* A -= X; */
147 ctx->seen |= SEEN_XREG;
148 PPC_SUB(r_A, r_A, r_X);
149 break;
150 case BPF_ALU | BPF_SUB | BPF_K: /* A -= K */
151 if (!K)
152 break;
153 PPC_ADDI(r_A, r_A, IMM_L(-K));
154 if (K >= 32768)
155 PPC_ADDIS(r_A, r_A, IMM_HA(-K));
156 break;
157 case BPF_ALU | BPF_MUL | BPF_X: /* A *= X; */
158 ctx->seen |= SEEN_XREG;
159 PPC_MULW(r_A, r_A, r_X);
160 break;
161 case BPF_ALU | BPF_MUL | BPF_K: /* A *= K */
162 if (K < 32768)
163 PPC_MULI(r_A, r_A, K);
164 else {
165 PPC_LI32(r_scratch1, K);
166 PPC_MULW(r_A, r_A, r_scratch1);
167 }
168 break;
169 case BPF_ALU | BPF_MOD | BPF_X: /* A %= X; */
170 case BPF_ALU | BPF_DIV | BPF_X: /* A /= X; */
171 ctx->seen |= SEEN_XREG;
172 PPC_CMPWI(r_X, 0);
173 if (ctx->pc_ret0 != -1) {
174 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
175 } else {
176 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
177 PPC_LI(r_ret, 0);
178 PPC_JMP(exit_addr);
179 }
180 if (code == (BPF_ALU | BPF_MOD | BPF_X)) {
181 PPC_DIVWU(r_scratch1, r_A, r_X);
182 PPC_MULW(r_scratch1, r_X, r_scratch1);
183 PPC_SUB(r_A, r_A, r_scratch1);
184 } else {
185 PPC_DIVWU(r_A, r_A, r_X);
186 }
187 break;
188 case BPF_ALU | BPF_MOD | BPF_K: /* A %= K; */
189 PPC_LI32(r_scratch2, K);
190 PPC_DIVWU(r_scratch1, r_A, r_scratch2);
191 PPC_MULW(r_scratch1, r_scratch2, r_scratch1);
192 PPC_SUB(r_A, r_A, r_scratch1);
193 break;
194 case BPF_ALU | BPF_DIV | BPF_K: /* A /= K */
195 if (K == 1)
196 break;
197 PPC_LI32(r_scratch1, K);
198 PPC_DIVWU(r_A, r_A, r_scratch1);
199 break;
200 case BPF_ALU | BPF_AND | BPF_X:
201 ctx->seen |= SEEN_XREG;
202 PPC_AND(r_A, r_A, r_X);
203 break;
204 case BPF_ALU | BPF_AND | BPF_K:
205 if (!IMM_H(K))
206 PPC_ANDI(r_A, r_A, K);
207 else {
208 PPC_LI32(r_scratch1, K);
209 PPC_AND(r_A, r_A, r_scratch1);
210 }
211 break;
212 case BPF_ALU | BPF_OR | BPF_X:
213 ctx->seen |= SEEN_XREG;
214 PPC_OR(r_A, r_A, r_X);
215 break;
216 case BPF_ALU | BPF_OR | BPF_K:
217 if (IMM_L(K))
218 PPC_ORI(r_A, r_A, IMM_L(K));
219 if (K >= 65536)
220 PPC_ORIS(r_A, r_A, IMM_H(K));
221 break;
222 case BPF_ANC | SKF_AD_ALU_XOR_X:
223 case BPF_ALU | BPF_XOR | BPF_X: /* A ^= X */
224 ctx->seen |= SEEN_XREG;
225 PPC_XOR(r_A, r_A, r_X);
226 break;
227 case BPF_ALU | BPF_XOR | BPF_K: /* A ^= K */
228 if (IMM_L(K))
229 PPC_XORI(r_A, r_A, IMM_L(K));
230 if (K >= 65536)
231 PPC_XORIS(r_A, r_A, IMM_H(K));
232 break;
233 case BPF_ALU | BPF_LSH | BPF_X: /* A <<= X; */
234 ctx->seen |= SEEN_XREG;
235 PPC_SLW(r_A, r_A, r_X);
236 break;
237 case BPF_ALU | BPF_LSH | BPF_K:
238 if (K == 0)
239 break;
240 else
241 PPC_SLWI(r_A, r_A, K);
242 break;
243 case BPF_ALU | BPF_RSH | BPF_X: /* A >>= X; */
244 ctx->seen |= SEEN_XREG;
245 PPC_SRW(r_A, r_A, r_X);
246 break;
247 case BPF_ALU | BPF_RSH | BPF_K: /* A >>= K; */
248 if (K == 0)
249 break;
250 else
251 PPC_SRWI(r_A, r_A, K);
252 break;
253 case BPF_ALU | BPF_NEG:
254 PPC_NEG(r_A, r_A);
255 break;
256 case BPF_RET | BPF_K:
257 PPC_LI32(r_ret, K);
258 if (!K) {
259 if (ctx->pc_ret0 == -1)
260 ctx->pc_ret0 = i;
261 }
262 /*
263 * If this isn't the very last instruction, branch to
264 * the epilogue if we've stuff to clean up. Otherwise,
265 * if there's nothing to tidy, just return. If we /are/
266 * the last instruction, we're about to fall through to
267 * the epilogue to return.
268 */
269 if (i != flen - 1) {
270 /*
271 * Note: 'seen' is properly valid only on pass
272 * #2. Both parts of this conditional are the
273 * same instruction size though, meaning the
274 * first pass will still correctly determine the
275 * code size/addresses.
276 */
277 if (ctx->seen)
278 PPC_JMP(exit_addr);
279 else
280 PPC_BLR();
281 }
282 break;
283 case BPF_RET | BPF_A:
284 PPC_MR(r_ret, r_A);
285 if (i != flen - 1) {
286 if (ctx->seen)
287 PPC_JMP(exit_addr);
288 else
289 PPC_BLR();
290 }
291 break;
292 case BPF_MISC | BPF_TAX: /* X = A */
293 PPC_MR(r_X, r_A);
294 break;
295 case BPF_MISC | BPF_TXA: /* A = X */
296 ctx->seen |= SEEN_XREG;
297 PPC_MR(r_A, r_X);
298 break;
299
300 /*** Constant loads/M[] access ***/
301 case BPF_LD | BPF_IMM: /* A = K */
302 PPC_LI32(r_A, K);
303 break;
304 case BPF_LDX | BPF_IMM: /* X = K */
305 PPC_LI32(r_X, K);
306 break;
307 case BPF_LD | BPF_MEM: /* A = mem[K] */
308 PPC_MR(r_A, r_M + (K & 0xf));
309 ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
310 break;
311 case BPF_LDX | BPF_MEM: /* X = mem[K] */
312 PPC_MR(r_X, r_M + (K & 0xf));
313 ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
314 break;
315 case BPF_ST: /* mem[K] = A */
316 PPC_MR(r_M + (K & 0xf), r_A);
317 ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
318 break;
319 case BPF_STX: /* mem[K] = X */
320 PPC_MR(r_M + (K & 0xf), r_X);
321 ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
322 break;
323 case BPF_LD | BPF_W | BPF_LEN: /* A = skb->len; */
324 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
325 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
326 break;
327 case BPF_LDX | BPF_W | BPF_ABS: /* A = *((u32 *)(seccomp_data + K)); */
328 PPC_LWZ_OFFS(r_A, r_skb, K);
329 break;
330 case BPF_LDX | BPF_W | BPF_LEN: /* X = skb->len; */
331 PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
332 break;
333
334 /*** Ancillary info loads ***/
335 case BPF_ANC | SKF_AD_PROTOCOL: /* A = ntohs(skb->protocol); */
336 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
337 protocol) != 2);
338 PPC_NTOHS_OFFS(r_A, r_skb, offsetof(struct sk_buff,
339 protocol));
340 break;
341 case BPF_ANC | SKF_AD_IFINDEX:
342 case BPF_ANC | SKF_AD_HATYPE:
343 BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
344 ifindex) != 4);
345 BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
346 type) != 2);
347 PPC_LL_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
348 dev));
349 PPC_CMPDI(r_scratch1, 0);
350 if (ctx->pc_ret0 != -1) {
351 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
352 } else {
353 /* Exit, returning 0; first pass hits here. */
354 PPC_BCC_SHORT(COND_NE, ctx->idx * 4 + 12);
355 PPC_LI(r_ret, 0);
356 PPC_JMP(exit_addr);
357 }
358 if (code == (BPF_ANC | SKF_AD_IFINDEX)) {
359 PPC_LWZ_OFFS(r_A, r_scratch1,
360 offsetof(struct net_device, ifindex));
361 } else {
362 PPC_LHZ_OFFS(r_A, r_scratch1,
363 offsetof(struct net_device, type));
364 }
365
366 break;
367 case BPF_ANC | SKF_AD_MARK:
368 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
369 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
370 mark));
371 break;
372 case BPF_ANC | SKF_AD_RXHASH:
373 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);
374 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
375 hash));
376 break;
377 case BPF_ANC | SKF_AD_VLAN_TAG:
378 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
379
380 PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
381 vlan_tci));
382 break;
383 case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT:
384 PPC_LBZ_OFFS(r_A, r_skb, PKT_VLAN_PRESENT_OFFSET());
385 if (PKT_VLAN_PRESENT_BIT)
386 PPC_SRWI(r_A, r_A, PKT_VLAN_PRESENT_BIT);
387 if (PKT_VLAN_PRESENT_BIT < 7)
388 PPC_ANDI(r_A, r_A, 1);
389 break;
390 case BPF_ANC | SKF_AD_QUEUE:
391 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
392 queue_mapping) != 2);
393 PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
394 queue_mapping));
395 break;
396 case BPF_ANC | SKF_AD_PKTTYPE:
397 PPC_LBZ_OFFS(r_A, r_skb, PKT_TYPE_OFFSET());
398 PPC_ANDI(r_A, r_A, PKT_TYPE_MAX);
399 PPC_SRWI(r_A, r_A, 5);
400 break;
401 case BPF_ANC | SKF_AD_CPU:
402 PPC_BPF_LOAD_CPU(r_A);
403 break;
404 /*** Absolute loads from packet header/data ***/
405 case BPF_LD | BPF_W | BPF_ABS:
406 func = CHOOSE_LOAD_FUNC(K, sk_load_word);
407 goto common_load;
408 case BPF_LD | BPF_H | BPF_ABS:
409 func = CHOOSE_LOAD_FUNC(K, sk_load_half);
410 goto common_load;
411 case BPF_LD | BPF_B | BPF_ABS:
412 func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
413 common_load:
414 /* Load from [K]. */
415 ctx->seen |= SEEN_DATAREF;
416 PPC_FUNC_ADDR(r_scratch1, func);
417 PPC_MTLR(r_scratch1);
418 PPC_LI32(r_addr, K);
419 PPC_BLRL();
420 /*
421 * Helper returns 'lt' condition on error, and an
422 * appropriate return value in r3
423 */
424 PPC_BCC(COND_LT, exit_addr);
425 break;
426
427 /*** Indirect loads from packet header/data ***/
428 case BPF_LD | BPF_W | BPF_IND:
429 func = sk_load_word;
430 goto common_load_ind;
431 case BPF_LD | BPF_H | BPF_IND:
432 func = sk_load_half;
433 goto common_load_ind;
434 case BPF_LD | BPF_B | BPF_IND:
435 func = sk_load_byte;
436 common_load_ind:
437 /*
438 * Load from [X + K]. Negative offsets are tested for
439 * in the helper functions.
440 */
441 ctx->seen |= SEEN_DATAREF | SEEN_XREG;
442 PPC_FUNC_ADDR(r_scratch1, func);
443 PPC_MTLR(r_scratch1);
444 PPC_ADDI(r_addr, r_X, IMM_L(K));
445 if (K >= 32768)
446 PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
447 PPC_BLRL();
448 /* If error, cr0.LT set */
449 PPC_BCC(COND_LT, exit_addr);
450 break;
451
452 case BPF_LDX | BPF_B | BPF_MSH:
453 func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
454 goto common_load;
455 break;
456
457 /*** Jump and branches ***/
458 case BPF_JMP | BPF_JA:
459 if (K != 0)
460 PPC_JMP(addrs[i + 1 + K]);
461 break;
462
463 case BPF_JMP | BPF_JGT | BPF_K:
464 case BPF_JMP | BPF_JGT | BPF_X:
465 true_cond = COND_GT;
466 goto cond_branch;
467 case BPF_JMP | BPF_JGE | BPF_K:
468 case BPF_JMP | BPF_JGE | BPF_X:
469 true_cond = COND_GE;
470 goto cond_branch;
471 case BPF_JMP | BPF_JEQ | BPF_K:
472 case BPF_JMP | BPF_JEQ | BPF_X:
473 true_cond = COND_EQ;
474 goto cond_branch;
475 case BPF_JMP | BPF_JSET | BPF_K:
476 case BPF_JMP | BPF_JSET | BPF_X:
477 true_cond = COND_NE;
478 /* Fall through */
479 cond_branch:
480 /* same targets, can avoid doing the test :) */
481 if (filter[i].jt == filter[i].jf) {
482 if (filter[i].jt > 0)
483 PPC_JMP(addrs[i + 1 + filter[i].jt]);
484 break;
485 }
486
487 switch (code) {
488 case BPF_JMP | BPF_JGT | BPF_X:
489 case BPF_JMP | BPF_JGE | BPF_X:
490 case BPF_JMP | BPF_JEQ | BPF_X:
491 ctx->seen |= SEEN_XREG;
492 PPC_CMPLW(r_A, r_X);
493 break;
494 case BPF_JMP | BPF_JSET | BPF_X:
495 ctx->seen |= SEEN_XREG;
496 PPC_AND_DOT(r_scratch1, r_A, r_X);
497 break;
498 case BPF_JMP | BPF_JEQ | BPF_K:
499 case BPF_JMP | BPF_JGT | BPF_K:
500 case BPF_JMP | BPF_JGE | BPF_K:
501 if (K < 32768)
502 PPC_CMPLWI(r_A, K);
503 else {
504 PPC_LI32(r_scratch1, K);
505 PPC_CMPLW(r_A, r_scratch1);
506 }
507 break;
508 case BPF_JMP | BPF_JSET | BPF_K:
509 if (K < 32768)
510 /* PPC_ANDI is /only/ dot-form */
511 PPC_ANDI(r_scratch1, r_A, K);
512 else {
513 PPC_LI32(r_scratch1, K);
514 PPC_AND_DOT(r_scratch1, r_A,
515 r_scratch1);
516 }
517 break;
518 }
519 /* Sometimes branches are constructed "backward", with
520 * the false path being the branch and true path being
521 * a fallthrough to the next instruction.
522 */
523 if (filter[i].jt == 0)
524 /* Swap the sense of the branch */
525 PPC_BCC(true_cond ^ COND_CMP_TRUE,
526 addrs[i + 1 + filter[i].jf]);
527 else {
528 PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
529 if (filter[i].jf != 0)
530 PPC_JMP(addrs[i + 1 + filter[i].jf]);
531 }
532 break;
533 default:
534 /* The filter contains something cruel & unusual.
535 * We don't handle it, but also there shouldn't be
536 * anything missing from our list.
537 */
538 if (printk_ratelimit())
539 pr_err("BPF filter opcode %04x (@%d) unsupported\n",
540 filter[i].code, i);
541 return -ENOTSUPP;
542 }
543
544 }
545 /* Set end-of-body-code address for exit. */
546 addrs[i] = ctx->idx * 4;
547
548 return 0;
549}
550
551void bpf_jit_compile(struct bpf_prog *fp)
552{
553 unsigned int proglen;
554 unsigned int alloclen;
555 u32 *image = NULL;
556 u32 *code_base;
557 unsigned int *addrs;
558 struct codegen_context cgctx;
559 int pass;
560 int flen = fp->len;
561
562 if (!bpf_jit_enable)
563 return;
564
565 addrs = kcalloc(flen + 1, sizeof(*addrs), GFP_KERNEL);
566 if (addrs == NULL)
567 return;
568
569 /*
570 * There are multiple assembly passes as the generated code will change
571 * size as it settles down, figuring out the max branch offsets/exit
572 * paths required.
573 *
574 * The range of standard conditional branches is +/- 32Kbytes. Since
575 * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to
576 * finish with 8 bytes/instruction. Not feasible, so long jumps are
577 * used, distinct from short branches.
578 *
579 * Current:
580 *
581 * For now, both branch types assemble to 2 words (short branches padded
582 * with a NOP); this is less efficient, but assembly will always complete
583 * after exactly 3 passes:
584 *
585 * First pass: No code buffer; Program is "faux-generated" -- no code
586 * emitted but maximum size of output determined (and addrs[] filled
587 * in). Also, we note whether we use M[], whether we use skb data, etc.
588 * All generation choices assumed to be 'worst-case', e.g. branches all
589 * far (2 instructions), return path code reduction not available, etc.
590 *
591 * Second pass: Code buffer allocated with size determined previously.
592 * Prologue generated to support features we have seen used. Exit paths
593 * determined and addrs[] is filled in again, as code may be slightly
594 * smaller as a result.
595 *
596 * Third pass: Code generated 'for real', and branch destinations
597 * determined from now-accurate addrs[] map.
598 *
599 * Ideal:
600 *
601 * If we optimise this, near branches will be shorter. On the
602 * first assembly pass, we should err on the side of caution and
603 * generate the biggest code. On subsequent passes, branches will be
604 * generated short or long and code size will reduce. With smaller
605 * code, more branches may fall into the short category, and code will
606 * reduce more.
607 *
608 * Finally, if we see one pass generate code the same size as the
609 * previous pass we have converged and should now generate code for
610 * real. Allocating at the end will also save the memory that would
611 * otherwise be wasted by the (small) current code shrinkage.
612 * Preferably, we should do a small number of passes (e.g. 5) and if we
613 * haven't converged by then, get impatient and force code to generate
614 * as-is, even if the odd branch would be left long. The chances of a
615 * long jump are tiny with all but the most enormous of BPF filter
616 * inputs, so we should usually converge on the third pass.
617 */
618
619 cgctx.idx = 0;
620 cgctx.seen = 0;
621 cgctx.pc_ret0 = -1;
622 /* Scouting faux-generate pass 0 */
623 if (bpf_jit_build_body(fp, 0, &cgctx, addrs))
624 /* We hit something illegal or unsupported. */
625 goto out;
626
627 /*
628 * Pretend to build prologue, given the features we've seen. This will
629 * update ctgtx.idx as it pretends to output instructions, then we can
630 * calculate total size from idx.
631 */
632 bpf_jit_build_prologue(fp, 0, &cgctx);
633 bpf_jit_build_epilogue(0, &cgctx);
634
635 proglen = cgctx.idx * 4;
636 alloclen = proglen + FUNCTION_DESCR_SIZE;
637 image = module_alloc(alloclen);
638 if (!image)
639 goto out;
640
641 code_base = image + (FUNCTION_DESCR_SIZE/4);
642
643 /* Code generation passes 1-2 */
644 for (pass = 1; pass < 3; pass++) {
645 /* Now build the prologue, body code & epilogue for real. */
646 cgctx.idx = 0;
647 bpf_jit_build_prologue(fp, code_base, &cgctx);
648 bpf_jit_build_body(fp, code_base, &cgctx, addrs);
649 bpf_jit_build_epilogue(code_base, &cgctx);
650
651 if (bpf_jit_enable > 1)
652 pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
653 proglen - (cgctx.idx * 4), cgctx.seen);
654 }
655
656 if (bpf_jit_enable > 1)
657 /* Note that we output the base address of the code_base
658 * rather than image, since opcodes are in code_base.
659 */
660 bpf_jit_dump(flen, proglen, pass, code_base);
661
662 bpf_flush_icache(code_base, code_base + (proglen/4));
663
664#ifdef CONFIG_PPC64
665 /* Function descriptor nastiness: Address + TOC */
666 ((u64 *)image)[0] = (u64)code_base;
667 ((u64 *)image)[1] = local_paca->kernel_toc;
668#endif
669
670 fp->bpf_func = (void *)image;
671 fp->jited = 1;
672
673out:
674 kfree(addrs);
675 return;
676}
677
678void bpf_jit_free(struct bpf_prog *fp)
679{
680 if (fp->jited)
681 module_memfree(fp->bpf_func);
682
683 bpf_prog_unlock_free(fp);
684}
1/* bpf_jit_comp.c: BPF JIT compiler
2 *
3 * Copyright 2011 Matt Evans <matt@ozlabs.org>, IBM Corporation
4 *
5 * Based on the x86 BPF compiler, by Eric Dumazet (eric.dumazet@gmail.com)
6 * Ported to ppc32 by Denis Kirjanov <kda@linux-powerpc.org>
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License
10 * as published by the Free Software Foundation; version 2
11 * of the License.
12 */
13#include <linux/moduleloader.h>
14#include <asm/cacheflush.h>
15#include <linux/netdevice.h>
16#include <linux/filter.h>
17#include <linux/if_vlan.h>
18
19#include "bpf_jit32.h"
20
21static inline void bpf_flush_icache(void *start, void *end)
22{
23 smp_wmb();
24 flush_icache_range((unsigned long)start, (unsigned long)end);
25}
26
27static void bpf_jit_build_prologue(struct bpf_prog *fp, u32 *image,
28 struct codegen_context *ctx)
29{
30 int i;
31 const struct sock_filter *filter = fp->insns;
32
33 if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
34 /* Make stackframe */
35 if (ctx->seen & SEEN_DATAREF) {
36 /* If we call any helpers (for loads), save LR */
37 EMIT(PPC_INST_MFLR | __PPC_RT(R0));
38 PPC_BPF_STL(0, 1, PPC_LR_STKOFF);
39
40 /* Back up non-volatile regs. */
41 PPC_BPF_STL(r_D, 1, -(REG_SZ*(32-r_D)));
42 PPC_BPF_STL(r_HL, 1, -(REG_SZ*(32-r_HL)));
43 }
44 if (ctx->seen & SEEN_MEM) {
45 /*
46 * Conditionally save regs r15-r31 as some will be used
47 * for M[] data.
48 */
49 for (i = r_M; i < (r_M+16); i++) {
50 if (ctx->seen & (1 << (i-r_M)))
51 PPC_BPF_STL(i, 1, -(REG_SZ*(32-i)));
52 }
53 }
54 PPC_BPF_STLU(1, 1, -BPF_PPC_STACKFRAME);
55 }
56
57 if (ctx->seen & SEEN_DATAREF) {
58 /*
59 * If this filter needs to access skb data,
60 * prepare r_D and r_HL:
61 * r_HL = skb->len - skb->data_len
62 * r_D = skb->data
63 */
64 PPC_LWZ_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
65 data_len));
66 PPC_LWZ_OFFS(r_HL, r_skb, offsetof(struct sk_buff, len));
67 PPC_SUB(r_HL, r_HL, r_scratch1);
68 PPC_LL_OFFS(r_D, r_skb, offsetof(struct sk_buff, data));
69 }
70
71 if (ctx->seen & SEEN_XREG) {
72 /*
73 * TODO: Could also detect whether first instr. sets X and
74 * avoid this (as below, with A).
75 */
76 PPC_LI(r_X, 0);
77 }
78
79 /* make sure we dont leak kernel information to user */
80 if (bpf_needs_clear_a(&filter[0]))
81 PPC_LI(r_A, 0);
82}
83
84static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
85{
86 int i;
87
88 if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
89 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
90 if (ctx->seen & SEEN_DATAREF) {
91 PPC_BPF_LL(0, 1, PPC_LR_STKOFF);
92 PPC_MTLR(0);
93 PPC_BPF_LL(r_D, 1, -(REG_SZ*(32-r_D)));
94 PPC_BPF_LL(r_HL, 1, -(REG_SZ*(32-r_HL)));
95 }
96 if (ctx->seen & SEEN_MEM) {
97 /* Restore any saved non-vol registers */
98 for (i = r_M; i < (r_M+16); i++) {
99 if (ctx->seen & (1 << (i-r_M)))
100 PPC_BPF_LL(i, 1, -(REG_SZ*(32-i)));
101 }
102 }
103 }
104 /* The RETs have left a return value in R3. */
105
106 PPC_BLR();
107}
108
109#define CHOOSE_LOAD_FUNC(K, func) \
110 ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
111
112/* Assemble the body code between the prologue & epilogue. */
113static int bpf_jit_build_body(struct bpf_prog *fp, u32 *image,
114 struct codegen_context *ctx,
115 unsigned int *addrs)
116{
117 const struct sock_filter *filter = fp->insns;
118 int flen = fp->len;
119 u8 *func;
120 unsigned int true_cond;
121 int i;
122
123 /* Start of epilogue code */
124 unsigned int exit_addr = addrs[flen];
125
126 for (i = 0; i < flen; i++) {
127 unsigned int K = filter[i].k;
128 u16 code = bpf_anc_helper(&filter[i]);
129
130 /*
131 * addrs[] maps a BPF bytecode address into a real offset from
132 * the start of the body code.
133 */
134 addrs[i] = ctx->idx * 4;
135
136 switch (code) {
137 /*** ALU ops ***/
138 case BPF_ALU | BPF_ADD | BPF_X: /* A += X; */
139 ctx->seen |= SEEN_XREG;
140 PPC_ADD(r_A, r_A, r_X);
141 break;
142 case BPF_ALU | BPF_ADD | BPF_K: /* A += K; */
143 if (!K)
144 break;
145 PPC_ADDI(r_A, r_A, IMM_L(K));
146 if (K >= 32768)
147 PPC_ADDIS(r_A, r_A, IMM_HA(K));
148 break;
149 case BPF_ALU | BPF_SUB | BPF_X: /* A -= X; */
150 ctx->seen |= SEEN_XREG;
151 PPC_SUB(r_A, r_A, r_X);
152 break;
153 case BPF_ALU | BPF_SUB | BPF_K: /* A -= K */
154 if (!K)
155 break;
156 PPC_ADDI(r_A, r_A, IMM_L(-K));
157 if (K >= 32768)
158 PPC_ADDIS(r_A, r_A, IMM_HA(-K));
159 break;
160 case BPF_ALU | BPF_MUL | BPF_X: /* A *= X; */
161 ctx->seen |= SEEN_XREG;
162 PPC_MULW(r_A, r_A, r_X);
163 break;
164 case BPF_ALU | BPF_MUL | BPF_K: /* A *= K */
165 if (K < 32768)
166 PPC_MULI(r_A, r_A, K);
167 else {
168 PPC_LI32(r_scratch1, K);
169 PPC_MULW(r_A, r_A, r_scratch1);
170 }
171 break;
172 case BPF_ALU | BPF_MOD | BPF_X: /* A %= X; */
173 case BPF_ALU | BPF_DIV | BPF_X: /* A /= X; */
174 ctx->seen |= SEEN_XREG;
175 PPC_CMPWI(r_X, 0);
176 if (ctx->pc_ret0 != -1) {
177 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
178 } else {
179 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
180 PPC_LI(r_ret, 0);
181 PPC_JMP(exit_addr);
182 }
183 if (code == (BPF_ALU | BPF_MOD | BPF_X)) {
184 PPC_DIVWU(r_scratch1, r_A, r_X);
185 PPC_MULW(r_scratch1, r_X, r_scratch1);
186 PPC_SUB(r_A, r_A, r_scratch1);
187 } else {
188 PPC_DIVWU(r_A, r_A, r_X);
189 }
190 break;
191 case BPF_ALU | BPF_MOD | BPF_K: /* A %= K; */
192 PPC_LI32(r_scratch2, K);
193 PPC_DIVWU(r_scratch1, r_A, r_scratch2);
194 PPC_MULW(r_scratch1, r_scratch2, r_scratch1);
195 PPC_SUB(r_A, r_A, r_scratch1);
196 break;
197 case BPF_ALU | BPF_DIV | BPF_K: /* A /= K */
198 if (K == 1)
199 break;
200 PPC_LI32(r_scratch1, K);
201 PPC_DIVWU(r_A, r_A, r_scratch1);
202 break;
203 case BPF_ALU | BPF_AND | BPF_X:
204 ctx->seen |= SEEN_XREG;
205 PPC_AND(r_A, r_A, r_X);
206 break;
207 case BPF_ALU | BPF_AND | BPF_K:
208 if (!IMM_H(K))
209 PPC_ANDI(r_A, r_A, K);
210 else {
211 PPC_LI32(r_scratch1, K);
212 PPC_AND(r_A, r_A, r_scratch1);
213 }
214 break;
215 case BPF_ALU | BPF_OR | BPF_X:
216 ctx->seen |= SEEN_XREG;
217 PPC_OR(r_A, r_A, r_X);
218 break;
219 case BPF_ALU | BPF_OR | BPF_K:
220 if (IMM_L(K))
221 PPC_ORI(r_A, r_A, IMM_L(K));
222 if (K >= 65536)
223 PPC_ORIS(r_A, r_A, IMM_H(K));
224 break;
225 case BPF_ANC | SKF_AD_ALU_XOR_X:
226 case BPF_ALU | BPF_XOR | BPF_X: /* A ^= X */
227 ctx->seen |= SEEN_XREG;
228 PPC_XOR(r_A, r_A, r_X);
229 break;
230 case BPF_ALU | BPF_XOR | BPF_K: /* A ^= K */
231 if (IMM_L(K))
232 PPC_XORI(r_A, r_A, IMM_L(K));
233 if (K >= 65536)
234 PPC_XORIS(r_A, r_A, IMM_H(K));
235 break;
236 case BPF_ALU | BPF_LSH | BPF_X: /* A <<= X; */
237 ctx->seen |= SEEN_XREG;
238 PPC_SLW(r_A, r_A, r_X);
239 break;
240 case BPF_ALU | BPF_LSH | BPF_K:
241 if (K == 0)
242 break;
243 else
244 PPC_SLWI(r_A, r_A, K);
245 break;
246 case BPF_ALU | BPF_RSH | BPF_X: /* A >>= X; */
247 ctx->seen |= SEEN_XREG;
248 PPC_SRW(r_A, r_A, r_X);
249 break;
250 case BPF_ALU | BPF_RSH | BPF_K: /* A >>= K; */
251 if (K == 0)
252 break;
253 else
254 PPC_SRWI(r_A, r_A, K);
255 break;
256 case BPF_ALU | BPF_NEG:
257 PPC_NEG(r_A, r_A);
258 break;
259 case BPF_RET | BPF_K:
260 PPC_LI32(r_ret, K);
261 if (!K) {
262 if (ctx->pc_ret0 == -1)
263 ctx->pc_ret0 = i;
264 }
265 /*
266 * If this isn't the very last instruction, branch to
267 * the epilogue if we've stuff to clean up. Otherwise,
268 * if there's nothing to tidy, just return. If we /are/
269 * the last instruction, we're about to fall through to
270 * the epilogue to return.
271 */
272 if (i != flen - 1) {
273 /*
274 * Note: 'seen' is properly valid only on pass
275 * #2. Both parts of this conditional are the
276 * same instruction size though, meaning the
277 * first pass will still correctly determine the
278 * code size/addresses.
279 */
280 if (ctx->seen)
281 PPC_JMP(exit_addr);
282 else
283 PPC_BLR();
284 }
285 break;
286 case BPF_RET | BPF_A:
287 PPC_MR(r_ret, r_A);
288 if (i != flen - 1) {
289 if (ctx->seen)
290 PPC_JMP(exit_addr);
291 else
292 PPC_BLR();
293 }
294 break;
295 case BPF_MISC | BPF_TAX: /* X = A */
296 PPC_MR(r_X, r_A);
297 break;
298 case BPF_MISC | BPF_TXA: /* A = X */
299 ctx->seen |= SEEN_XREG;
300 PPC_MR(r_A, r_X);
301 break;
302
303 /*** Constant loads/M[] access ***/
304 case BPF_LD | BPF_IMM: /* A = K */
305 PPC_LI32(r_A, K);
306 break;
307 case BPF_LDX | BPF_IMM: /* X = K */
308 PPC_LI32(r_X, K);
309 break;
310 case BPF_LD | BPF_MEM: /* A = mem[K] */
311 PPC_MR(r_A, r_M + (K & 0xf));
312 ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
313 break;
314 case BPF_LDX | BPF_MEM: /* X = mem[K] */
315 PPC_MR(r_X, r_M + (K & 0xf));
316 ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
317 break;
318 case BPF_ST: /* mem[K] = A */
319 PPC_MR(r_M + (K & 0xf), r_A);
320 ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
321 break;
322 case BPF_STX: /* mem[K] = X */
323 PPC_MR(r_M + (K & 0xf), r_X);
324 ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
325 break;
326 case BPF_LD | BPF_W | BPF_LEN: /* A = skb->len; */
327 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
328 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
329 break;
330 case BPF_LDX | BPF_W | BPF_ABS: /* A = *((u32 *)(seccomp_data + K)); */
331 PPC_LWZ_OFFS(r_A, r_skb, K);
332 break;
333 case BPF_LDX | BPF_W | BPF_LEN: /* X = skb->len; */
334 PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
335 break;
336
337 /*** Ancillary info loads ***/
338 case BPF_ANC | SKF_AD_PROTOCOL: /* A = ntohs(skb->protocol); */
339 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
340 protocol) != 2);
341 PPC_NTOHS_OFFS(r_A, r_skb, offsetof(struct sk_buff,
342 protocol));
343 break;
344 case BPF_ANC | SKF_AD_IFINDEX:
345 case BPF_ANC | SKF_AD_HATYPE:
346 BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
347 ifindex) != 4);
348 BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
349 type) != 2);
350 PPC_LL_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
351 dev));
352 PPC_CMPDI(r_scratch1, 0);
353 if (ctx->pc_ret0 != -1) {
354 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
355 } else {
356 /* Exit, returning 0; first pass hits here. */
357 PPC_BCC_SHORT(COND_NE, ctx->idx * 4 + 12);
358 PPC_LI(r_ret, 0);
359 PPC_JMP(exit_addr);
360 }
361 if (code == (BPF_ANC | SKF_AD_IFINDEX)) {
362 PPC_LWZ_OFFS(r_A, r_scratch1,
363 offsetof(struct net_device, ifindex));
364 } else {
365 PPC_LHZ_OFFS(r_A, r_scratch1,
366 offsetof(struct net_device, type));
367 }
368
369 break;
370 case BPF_ANC | SKF_AD_MARK:
371 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
372 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
373 mark));
374 break;
375 case BPF_ANC | SKF_AD_RXHASH:
376 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);
377 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
378 hash));
379 break;
380 case BPF_ANC | SKF_AD_VLAN_TAG:
381 case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT:
382 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
383 BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
384
385 PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
386 vlan_tci));
387 if (code == (BPF_ANC | SKF_AD_VLAN_TAG)) {
388 PPC_ANDI(r_A, r_A, ~VLAN_TAG_PRESENT);
389 } else {
390 PPC_ANDI(r_A, r_A, VLAN_TAG_PRESENT);
391 PPC_SRWI(r_A, r_A, 12);
392 }
393 break;
394 case BPF_ANC | SKF_AD_QUEUE:
395 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
396 queue_mapping) != 2);
397 PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
398 queue_mapping));
399 break;
400 case BPF_ANC | SKF_AD_PKTTYPE:
401 PPC_LBZ_OFFS(r_A, r_skb, PKT_TYPE_OFFSET());
402 PPC_ANDI(r_A, r_A, PKT_TYPE_MAX);
403 PPC_SRWI(r_A, r_A, 5);
404 break;
405 case BPF_ANC | SKF_AD_CPU:
406 PPC_BPF_LOAD_CPU(r_A);
407 break;
408 /*** Absolute loads from packet header/data ***/
409 case BPF_LD | BPF_W | BPF_ABS:
410 func = CHOOSE_LOAD_FUNC(K, sk_load_word);
411 goto common_load;
412 case BPF_LD | BPF_H | BPF_ABS:
413 func = CHOOSE_LOAD_FUNC(K, sk_load_half);
414 goto common_load;
415 case BPF_LD | BPF_B | BPF_ABS:
416 func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
417 common_load:
418 /* Load from [K]. */
419 ctx->seen |= SEEN_DATAREF;
420 PPC_FUNC_ADDR(r_scratch1, func);
421 PPC_MTLR(r_scratch1);
422 PPC_LI32(r_addr, K);
423 PPC_BLRL();
424 /*
425 * Helper returns 'lt' condition on error, and an
426 * appropriate return value in r3
427 */
428 PPC_BCC(COND_LT, exit_addr);
429 break;
430
431 /*** Indirect loads from packet header/data ***/
432 case BPF_LD | BPF_W | BPF_IND:
433 func = sk_load_word;
434 goto common_load_ind;
435 case BPF_LD | BPF_H | BPF_IND:
436 func = sk_load_half;
437 goto common_load_ind;
438 case BPF_LD | BPF_B | BPF_IND:
439 func = sk_load_byte;
440 common_load_ind:
441 /*
442 * Load from [X + K]. Negative offsets are tested for
443 * in the helper functions.
444 */
445 ctx->seen |= SEEN_DATAREF | SEEN_XREG;
446 PPC_FUNC_ADDR(r_scratch1, func);
447 PPC_MTLR(r_scratch1);
448 PPC_ADDI(r_addr, r_X, IMM_L(K));
449 if (K >= 32768)
450 PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
451 PPC_BLRL();
452 /* If error, cr0.LT set */
453 PPC_BCC(COND_LT, exit_addr);
454 break;
455
456 case BPF_LDX | BPF_B | BPF_MSH:
457 func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
458 goto common_load;
459 break;
460
461 /*** Jump and branches ***/
462 case BPF_JMP | BPF_JA:
463 if (K != 0)
464 PPC_JMP(addrs[i + 1 + K]);
465 break;
466
467 case BPF_JMP | BPF_JGT | BPF_K:
468 case BPF_JMP | BPF_JGT | BPF_X:
469 true_cond = COND_GT;
470 goto cond_branch;
471 case BPF_JMP | BPF_JGE | BPF_K:
472 case BPF_JMP | BPF_JGE | BPF_X:
473 true_cond = COND_GE;
474 goto cond_branch;
475 case BPF_JMP | BPF_JEQ | BPF_K:
476 case BPF_JMP | BPF_JEQ | BPF_X:
477 true_cond = COND_EQ;
478 goto cond_branch;
479 case BPF_JMP | BPF_JSET | BPF_K:
480 case BPF_JMP | BPF_JSET | BPF_X:
481 true_cond = COND_NE;
482 /* Fall through */
483 cond_branch:
484 /* same targets, can avoid doing the test :) */
485 if (filter[i].jt == filter[i].jf) {
486 if (filter[i].jt > 0)
487 PPC_JMP(addrs[i + 1 + filter[i].jt]);
488 break;
489 }
490
491 switch (code) {
492 case BPF_JMP | BPF_JGT | BPF_X:
493 case BPF_JMP | BPF_JGE | BPF_X:
494 case BPF_JMP | BPF_JEQ | BPF_X:
495 ctx->seen |= SEEN_XREG;
496 PPC_CMPLW(r_A, r_X);
497 break;
498 case BPF_JMP | BPF_JSET | BPF_X:
499 ctx->seen |= SEEN_XREG;
500 PPC_AND_DOT(r_scratch1, r_A, r_X);
501 break;
502 case BPF_JMP | BPF_JEQ | BPF_K:
503 case BPF_JMP | BPF_JGT | BPF_K:
504 case BPF_JMP | BPF_JGE | BPF_K:
505 if (K < 32768)
506 PPC_CMPLWI(r_A, K);
507 else {
508 PPC_LI32(r_scratch1, K);
509 PPC_CMPLW(r_A, r_scratch1);
510 }
511 break;
512 case BPF_JMP | BPF_JSET | BPF_K:
513 if (K < 32768)
514 /* PPC_ANDI is /only/ dot-form */
515 PPC_ANDI(r_scratch1, r_A, K);
516 else {
517 PPC_LI32(r_scratch1, K);
518 PPC_AND_DOT(r_scratch1, r_A,
519 r_scratch1);
520 }
521 break;
522 }
523 /* Sometimes branches are constructed "backward", with
524 * the false path being the branch and true path being
525 * a fallthrough to the next instruction.
526 */
527 if (filter[i].jt == 0)
528 /* Swap the sense of the branch */
529 PPC_BCC(true_cond ^ COND_CMP_TRUE,
530 addrs[i + 1 + filter[i].jf]);
531 else {
532 PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
533 if (filter[i].jf != 0)
534 PPC_JMP(addrs[i + 1 + filter[i].jf]);
535 }
536 break;
537 default:
538 /* The filter contains something cruel & unusual.
539 * We don't handle it, but also there shouldn't be
540 * anything missing from our list.
541 */
542 if (printk_ratelimit())
543 pr_err("BPF filter opcode %04x (@%d) unsupported\n",
544 filter[i].code, i);
545 return -ENOTSUPP;
546 }
547
548 }
549 /* Set end-of-body-code address for exit. */
550 addrs[i] = ctx->idx * 4;
551
552 return 0;
553}
554
555void bpf_jit_compile(struct bpf_prog *fp)
556{
557 unsigned int proglen;
558 unsigned int alloclen;
559 u32 *image = NULL;
560 u32 *code_base;
561 unsigned int *addrs;
562 struct codegen_context cgctx;
563 int pass;
564 int flen = fp->len;
565
566 if (!bpf_jit_enable)
567 return;
568
569 addrs = kzalloc((flen+1) * sizeof(*addrs), GFP_KERNEL);
570 if (addrs == NULL)
571 return;
572
573 /*
574 * There are multiple assembly passes as the generated code will change
575 * size as it settles down, figuring out the max branch offsets/exit
576 * paths required.
577 *
578 * The range of standard conditional branches is +/- 32Kbytes. Since
579 * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to
580 * finish with 8 bytes/instruction. Not feasible, so long jumps are
581 * used, distinct from short branches.
582 *
583 * Current:
584 *
585 * For now, both branch types assemble to 2 words (short branches padded
586 * with a NOP); this is less efficient, but assembly will always complete
587 * after exactly 3 passes:
588 *
589 * First pass: No code buffer; Program is "faux-generated" -- no code
590 * emitted but maximum size of output determined (and addrs[] filled
591 * in). Also, we note whether we use M[], whether we use skb data, etc.
592 * All generation choices assumed to be 'worst-case', e.g. branches all
593 * far (2 instructions), return path code reduction not available, etc.
594 *
595 * Second pass: Code buffer allocated with size determined previously.
596 * Prologue generated to support features we have seen used. Exit paths
597 * determined and addrs[] is filled in again, as code may be slightly
598 * smaller as a result.
599 *
600 * Third pass: Code generated 'for real', and branch destinations
601 * determined from now-accurate addrs[] map.
602 *
603 * Ideal:
604 *
605 * If we optimise this, near branches will be shorter. On the
606 * first assembly pass, we should err on the side of caution and
607 * generate the biggest code. On subsequent passes, branches will be
608 * generated short or long and code size will reduce. With smaller
609 * code, more branches may fall into the short category, and code will
610 * reduce more.
611 *
612 * Finally, if we see one pass generate code the same size as the
613 * previous pass we have converged and should now generate code for
614 * real. Allocating at the end will also save the memory that would
615 * otherwise be wasted by the (small) current code shrinkage.
616 * Preferably, we should do a small number of passes (e.g. 5) and if we
617 * haven't converged by then, get impatient and force code to generate
618 * as-is, even if the odd branch would be left long. The chances of a
619 * long jump are tiny with all but the most enormous of BPF filter
620 * inputs, so we should usually converge on the third pass.
621 */
622
623 cgctx.idx = 0;
624 cgctx.seen = 0;
625 cgctx.pc_ret0 = -1;
626 /* Scouting faux-generate pass 0 */
627 if (bpf_jit_build_body(fp, 0, &cgctx, addrs))
628 /* We hit something illegal or unsupported. */
629 goto out;
630
631 /*
632 * Pretend to build prologue, given the features we've seen. This will
633 * update ctgtx.idx as it pretends to output instructions, then we can
634 * calculate total size from idx.
635 */
636 bpf_jit_build_prologue(fp, 0, &cgctx);
637 bpf_jit_build_epilogue(0, &cgctx);
638
639 proglen = cgctx.idx * 4;
640 alloclen = proglen + FUNCTION_DESCR_SIZE;
641 image = module_alloc(alloclen);
642 if (!image)
643 goto out;
644
645 code_base = image + (FUNCTION_DESCR_SIZE/4);
646
647 /* Code generation passes 1-2 */
648 for (pass = 1; pass < 3; pass++) {
649 /* Now build the prologue, body code & epilogue for real. */
650 cgctx.idx = 0;
651 bpf_jit_build_prologue(fp, code_base, &cgctx);
652 bpf_jit_build_body(fp, code_base, &cgctx, addrs);
653 bpf_jit_build_epilogue(code_base, &cgctx);
654
655 if (bpf_jit_enable > 1)
656 pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
657 proglen - (cgctx.idx * 4), cgctx.seen);
658 }
659
660 if (bpf_jit_enable > 1)
661 /* Note that we output the base address of the code_base
662 * rather than image, since opcodes are in code_base.
663 */
664 bpf_jit_dump(flen, proglen, pass, code_base);
665
666 bpf_flush_icache(code_base, code_base + (proglen/4));
667
668#ifdef CONFIG_PPC64
669 /* Function descriptor nastiness: Address + TOC */
670 ((u64 *)image)[0] = (u64)code_base;
671 ((u64 *)image)[1] = local_paca->kernel_toc;
672#endif
673
674 fp->bpf_func = (void *)image;
675 fp->jited = 1;
676
677out:
678 kfree(addrs);
679 return;
680}
681
682void bpf_jit_free(struct bpf_prog *fp)
683{
684 if (fp->jited)
685 module_memfree(fp->bpf_func);
686
687 bpf_prog_unlock_free(fp);
688}