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1/* bpf_jit_comp.c: BPF JIT compiler for PPC64
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 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; version 2
10 * of the License.
11 */
12#include <linux/moduleloader.h>
13#include <asm/cacheflush.h>
14#include <linux/netdevice.h>
15#include <linux/filter.h>
16#include "bpf_jit.h"
17
18#ifndef __BIG_ENDIAN
19/* There are endianness assumptions herein. */
20#error "Little-endian PPC not supported in BPF compiler"
21#endif
22
23int bpf_jit_enable __read_mostly;
24
25
26static inline void bpf_flush_icache(void *start, void *end)
27{
28 smp_wmb();
29 flush_icache_range((unsigned long)start, (unsigned long)end);
30}
31
32static void bpf_jit_build_prologue(struct sk_filter *fp, u32 *image,
33 struct codegen_context *ctx)
34{
35 int i;
36 const struct sock_filter *filter = fp->insns;
37
38 if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
39 /* Make stackframe */
40 if (ctx->seen & SEEN_DATAREF) {
41 /* If we call any helpers (for loads), save LR */
42 EMIT(PPC_INST_MFLR | __PPC_RT(0));
43 PPC_STD(0, 1, 16);
44
45 /* Back up non-volatile regs. */
46 PPC_STD(r_D, 1, -(8*(32-r_D)));
47 PPC_STD(r_HL, 1, -(8*(32-r_HL)));
48 }
49 if (ctx->seen & SEEN_MEM) {
50 /*
51 * Conditionally save regs r15-r31 as some will be used
52 * for M[] data.
53 */
54 for (i = r_M; i < (r_M+16); i++) {
55 if (ctx->seen & (1 << (i-r_M)))
56 PPC_STD(i, 1, -(8*(32-i)));
57 }
58 }
59 EMIT(PPC_INST_STDU | __PPC_RS(1) | __PPC_RA(1) |
60 (-BPF_PPC_STACKFRAME & 0xfffc));
61 }
62
63 if (ctx->seen & SEEN_DATAREF) {
64 /*
65 * If this filter needs to access skb data,
66 * prepare r_D and r_HL:
67 * r_HL = skb->len - skb->data_len
68 * r_D = skb->data
69 */
70 PPC_LWZ_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
71 data_len));
72 PPC_LWZ_OFFS(r_HL, r_skb, offsetof(struct sk_buff, len));
73 PPC_SUB(r_HL, r_HL, r_scratch1);
74 PPC_LD_OFFS(r_D, r_skb, offsetof(struct sk_buff, data));
75 }
76
77 if (ctx->seen & SEEN_XREG) {
78 /*
79 * TODO: Could also detect whether first instr. sets X and
80 * avoid this (as below, with A).
81 */
82 PPC_LI(r_X, 0);
83 }
84
85 switch (filter[0].code) {
86 case BPF_S_RET_K:
87 case BPF_S_LD_W_LEN:
88 case BPF_S_ANC_PROTOCOL:
89 case BPF_S_ANC_IFINDEX:
90 case BPF_S_ANC_MARK:
91 case BPF_S_ANC_RXHASH:
92 case BPF_S_ANC_CPU:
93 case BPF_S_ANC_QUEUE:
94 case BPF_S_LD_W_ABS:
95 case BPF_S_LD_H_ABS:
96 case BPF_S_LD_B_ABS:
97 /* first instruction sets A register (or is RET 'constant') */
98 break;
99 default:
100 /* make sure we dont leak kernel information to user */
101 PPC_LI(r_A, 0);
102 }
103}
104
105static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
106{
107 int i;
108
109 if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
110 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
111 if (ctx->seen & SEEN_DATAREF) {
112 PPC_LD(0, 1, 16);
113 PPC_MTLR(0);
114 PPC_LD(r_D, 1, -(8*(32-r_D)));
115 PPC_LD(r_HL, 1, -(8*(32-r_HL)));
116 }
117 if (ctx->seen & SEEN_MEM) {
118 /* Restore any saved non-vol registers */
119 for (i = r_M; i < (r_M+16); i++) {
120 if (ctx->seen & (1 << (i-r_M)))
121 PPC_LD(i, 1, -(8*(32-i)));
122 }
123 }
124 }
125 /* The RETs have left a return value in R3. */
126
127 PPC_BLR();
128}
129
130/* Assemble the body code between the prologue & epilogue. */
131static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
132 struct codegen_context *ctx,
133 unsigned int *addrs)
134{
135 const struct sock_filter *filter = fp->insns;
136 int flen = fp->len;
137 u8 *func;
138 unsigned int true_cond;
139 int i;
140
141 /* Start of epilogue code */
142 unsigned int exit_addr = addrs[flen];
143
144 for (i = 0; i < flen; i++) {
145 unsigned int K = filter[i].k;
146
147 /*
148 * addrs[] maps a BPF bytecode address into a real offset from
149 * the start of the body code.
150 */
151 addrs[i] = ctx->idx * 4;
152
153 switch (filter[i].code) {
154 /*** ALU ops ***/
155 case BPF_S_ALU_ADD_X: /* A += X; */
156 ctx->seen |= SEEN_XREG;
157 PPC_ADD(r_A, r_A, r_X);
158 break;
159 case BPF_S_ALU_ADD_K: /* A += K; */
160 if (!K)
161 break;
162 PPC_ADDI(r_A, r_A, IMM_L(K));
163 if (K >= 32768)
164 PPC_ADDIS(r_A, r_A, IMM_HA(K));
165 break;
166 case BPF_S_ALU_SUB_X: /* A -= X; */
167 ctx->seen |= SEEN_XREG;
168 PPC_SUB(r_A, r_A, r_X);
169 break;
170 case BPF_S_ALU_SUB_K: /* A -= K */
171 if (!K)
172 break;
173 PPC_ADDI(r_A, r_A, IMM_L(-K));
174 if (K >= 32768)
175 PPC_ADDIS(r_A, r_A, IMM_HA(-K));
176 break;
177 case BPF_S_ALU_MUL_X: /* A *= X; */
178 ctx->seen |= SEEN_XREG;
179 PPC_MUL(r_A, r_A, r_X);
180 break;
181 case BPF_S_ALU_MUL_K: /* A *= K */
182 if (K < 32768)
183 PPC_MULI(r_A, r_A, K);
184 else {
185 PPC_LI32(r_scratch1, K);
186 PPC_MUL(r_A, r_A, r_scratch1);
187 }
188 break;
189 case BPF_S_ALU_DIV_X: /* A /= X; */
190 ctx->seen |= SEEN_XREG;
191 PPC_CMPWI(r_X, 0);
192 if (ctx->pc_ret0 != -1) {
193 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
194 } else {
195 /*
196 * Exit, returning 0; first pass hits here
197 * (longer worst-case code size).
198 */
199 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
200 PPC_LI(r_ret, 0);
201 PPC_JMP(exit_addr);
202 }
203 PPC_DIVWU(r_A, r_A, r_X);
204 break;
205 case BPF_S_ALU_DIV_K: /* A = reciprocal_divide(A, K); */
206 PPC_LI32(r_scratch1, K);
207 /* Top 32 bits of 64bit result -> A */
208 PPC_MULHWU(r_A, r_A, r_scratch1);
209 break;
210 case BPF_S_ALU_AND_X:
211 ctx->seen |= SEEN_XREG;
212 PPC_AND(r_A, r_A, r_X);
213 break;
214 case BPF_S_ALU_AND_K:
215 if (!IMM_H(K))
216 PPC_ANDI(r_A, r_A, K);
217 else {
218 PPC_LI32(r_scratch1, K);
219 PPC_AND(r_A, r_A, r_scratch1);
220 }
221 break;
222 case BPF_S_ALU_OR_X:
223 ctx->seen |= SEEN_XREG;
224 PPC_OR(r_A, r_A, r_X);
225 break;
226 case BPF_S_ALU_OR_K:
227 if (IMM_L(K))
228 PPC_ORI(r_A, r_A, IMM_L(K));
229 if (K >= 65536)
230 PPC_ORIS(r_A, r_A, IMM_H(K));
231 break;
232 case BPF_S_ALU_LSH_X: /* A <<= X; */
233 ctx->seen |= SEEN_XREG;
234 PPC_SLW(r_A, r_A, r_X);
235 break;
236 case BPF_S_ALU_LSH_K:
237 if (K == 0)
238 break;
239 else
240 PPC_SLWI(r_A, r_A, K);
241 break;
242 case BPF_S_ALU_RSH_X: /* A >>= X; */
243 ctx->seen |= SEEN_XREG;
244 PPC_SRW(r_A, r_A, r_X);
245 break;
246 case BPF_S_ALU_RSH_K: /* A >>= K; */
247 if (K == 0)
248 break;
249 else
250 PPC_SRWI(r_A, r_A, K);
251 break;
252 case BPF_S_ALU_NEG:
253 PPC_NEG(r_A, r_A);
254 break;
255 case BPF_S_RET_K:
256 PPC_LI32(r_ret, K);
257 if (!K) {
258 if (ctx->pc_ret0 == -1)
259 ctx->pc_ret0 = i;
260 }
261 /*
262 * If this isn't the very last instruction, branch to
263 * the epilogue if we've stuff to clean up. Otherwise,
264 * if there's nothing to tidy, just return. If we /are/
265 * the last instruction, we're about to fall through to
266 * the epilogue to return.
267 */
268 if (i != flen - 1) {
269 /*
270 * Note: 'seen' is properly valid only on pass
271 * #2. Both parts of this conditional are the
272 * same instruction size though, meaning the
273 * first pass will still correctly determine the
274 * code size/addresses.
275 */
276 if (ctx->seen)
277 PPC_JMP(exit_addr);
278 else
279 PPC_BLR();
280 }
281 break;
282 case BPF_S_RET_A:
283 PPC_MR(r_ret, r_A);
284 if (i != flen - 1) {
285 if (ctx->seen)
286 PPC_JMP(exit_addr);
287 else
288 PPC_BLR();
289 }
290 break;
291 case BPF_S_MISC_TAX: /* X = A */
292 PPC_MR(r_X, r_A);
293 break;
294 case BPF_S_MISC_TXA: /* A = X */
295 ctx->seen |= SEEN_XREG;
296 PPC_MR(r_A, r_X);
297 break;
298
299 /*** Constant loads/M[] access ***/
300 case BPF_S_LD_IMM: /* A = K */
301 PPC_LI32(r_A, K);
302 break;
303 case BPF_S_LDX_IMM: /* X = K */
304 PPC_LI32(r_X, K);
305 break;
306 case BPF_S_LD_MEM: /* A = mem[K] */
307 PPC_MR(r_A, r_M + (K & 0xf));
308 ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
309 break;
310 case BPF_S_LDX_MEM: /* X = mem[K] */
311 PPC_MR(r_X, r_M + (K & 0xf));
312 ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
313 break;
314 case BPF_S_ST: /* mem[K] = A */
315 PPC_MR(r_M + (K & 0xf), r_A);
316 ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
317 break;
318 case BPF_S_STX: /* mem[K] = X */
319 PPC_MR(r_M + (K & 0xf), r_X);
320 ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
321 break;
322 case BPF_S_LD_W_LEN: /* A = skb->len; */
323 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
324 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
325 break;
326 case BPF_S_LDX_W_LEN: /* X = skb->len; */
327 PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
328 break;
329
330 /*** Ancillary info loads ***/
331
332 /* None of the BPF_S_ANC* codes appear to be passed by
333 * sk_chk_filter(). The interpreter and the x86 BPF
334 * compiler implement them so we do too -- they may be
335 * planted in future.
336 */
337 case BPF_S_ANC_PROTOCOL: /* A = ntohs(skb->protocol); */
338 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
339 protocol) != 2);
340 PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
341 protocol));
342 /* ntohs is a NOP with BE loads. */
343 break;
344 case BPF_S_ANC_IFINDEX:
345 PPC_LD_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
346 dev));
347 PPC_CMPDI(r_scratch1, 0);
348 if (ctx->pc_ret0 != -1) {
349 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
350 } else {
351 /* Exit, returning 0; first pass hits here. */
352 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
353 PPC_LI(r_ret, 0);
354 PPC_JMP(exit_addr);
355 }
356 BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
357 ifindex) != 4);
358 PPC_LWZ_OFFS(r_A, r_scratch1,
359 offsetof(struct net_device, ifindex));
360 break;
361 case BPF_S_ANC_MARK:
362 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
363 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
364 mark));
365 break;
366 case BPF_S_ANC_RXHASH:
367 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, rxhash) != 4);
368 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
369 rxhash));
370 break;
371 case BPF_S_ANC_QUEUE:
372 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
373 queue_mapping) != 2);
374 PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
375 queue_mapping));
376 break;
377 case BPF_S_ANC_CPU:
378#ifdef CONFIG_SMP
379 /*
380 * PACA ptr is r13:
381 * raw_smp_processor_id() = local_paca->paca_index
382 */
383 BUILD_BUG_ON(FIELD_SIZEOF(struct paca_struct,
384 paca_index) != 2);
385 PPC_LHZ_OFFS(r_A, 13,
386 offsetof(struct paca_struct, paca_index));
387#else
388 PPC_LI(r_A, 0);
389#endif
390 break;
391
392 /*** Absolute loads from packet header/data ***/
393 case BPF_S_LD_W_ABS:
394 func = sk_load_word;
395 goto common_load;
396 case BPF_S_LD_H_ABS:
397 func = sk_load_half;
398 goto common_load;
399 case BPF_S_LD_B_ABS:
400 func = sk_load_byte;
401 common_load:
402 /*
403 * Load from [K]. Reference with the (negative)
404 * SKF_NET_OFF/SKF_LL_OFF offsets is unsupported.
405 */
406 ctx->seen |= SEEN_DATAREF;
407 if ((int)K < 0)
408 return -ENOTSUPP;
409 PPC_LI64(r_scratch1, func);
410 PPC_MTLR(r_scratch1);
411 PPC_LI32(r_addr, K);
412 PPC_BLRL();
413 /*
414 * Helper returns 'lt' condition on error, and an
415 * appropriate return value in r3
416 */
417 PPC_BCC(COND_LT, exit_addr);
418 break;
419
420 /*** Indirect loads from packet header/data ***/
421 case BPF_S_LD_W_IND:
422 func = sk_load_word;
423 goto common_load_ind;
424 case BPF_S_LD_H_IND:
425 func = sk_load_half;
426 goto common_load_ind;
427 case BPF_S_LD_B_IND:
428 func = sk_load_byte;
429 common_load_ind:
430 /*
431 * Load from [X + K]. Negative offsets are tested for
432 * in the helper functions, and result in a 'ret 0'.
433 */
434 ctx->seen |= SEEN_DATAREF | SEEN_XREG;
435 PPC_LI64(r_scratch1, func);
436 PPC_MTLR(r_scratch1);
437 PPC_ADDI(r_addr, r_X, IMM_L(K));
438 if (K >= 32768)
439 PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
440 PPC_BLRL();
441 /* If error, cr0.LT set */
442 PPC_BCC(COND_LT, exit_addr);
443 break;
444
445 case BPF_S_LDX_B_MSH:
446 /*
447 * x86 version drops packet (RET 0) when K<0, whereas
448 * interpreter does allow K<0 (__load_pointer, special
449 * ancillary data). common_load returns ENOTSUPP if K<0,
450 * so we fall back to interpreter & filter works.
451 */
452 func = sk_load_byte_msh;
453 goto common_load;
454 break;
455
456 /*** Jump and branches ***/
457 case BPF_S_JMP_JA:
458 if (K != 0)
459 PPC_JMP(addrs[i + 1 + K]);
460 break;
461
462 case BPF_S_JMP_JGT_K:
463 case BPF_S_JMP_JGT_X:
464 true_cond = COND_GT;
465 goto cond_branch;
466 case BPF_S_JMP_JGE_K:
467 case BPF_S_JMP_JGE_X:
468 true_cond = COND_GE;
469 goto cond_branch;
470 case BPF_S_JMP_JEQ_K:
471 case BPF_S_JMP_JEQ_X:
472 true_cond = COND_EQ;
473 goto cond_branch;
474 case BPF_S_JMP_JSET_K:
475 case BPF_S_JMP_JSET_X:
476 true_cond = COND_NE;
477 /* Fall through */
478 cond_branch:
479 /* same targets, can avoid doing the test :) */
480 if (filter[i].jt == filter[i].jf) {
481 if (filter[i].jt > 0)
482 PPC_JMP(addrs[i + 1 + filter[i].jt]);
483 break;
484 }
485
486 switch (filter[i].code) {
487 case BPF_S_JMP_JGT_X:
488 case BPF_S_JMP_JGE_X:
489 case BPF_S_JMP_JEQ_X:
490 ctx->seen |= SEEN_XREG;
491 PPC_CMPLW(r_A, r_X);
492 break;
493 case BPF_S_JMP_JSET_X:
494 ctx->seen |= SEEN_XREG;
495 PPC_AND_DOT(r_scratch1, r_A, r_X);
496 break;
497 case BPF_S_JMP_JEQ_K:
498 case BPF_S_JMP_JGT_K:
499 case BPF_S_JMP_JGE_K:
500 if (K < 32768)
501 PPC_CMPLWI(r_A, K);
502 else {
503 PPC_LI32(r_scratch1, K);
504 PPC_CMPLW(r_A, r_scratch1);
505 }
506 break;
507 case BPF_S_JMP_JSET_K:
508 if (K < 32768)
509 /* PPC_ANDI is /only/ dot-form */
510 PPC_ANDI(r_scratch1, r_A, K);
511 else {
512 PPC_LI32(r_scratch1, K);
513 PPC_AND_DOT(r_scratch1, r_A,
514 r_scratch1);
515 }
516 break;
517 }
518 /* Sometimes branches are constructed "backward", with
519 * the false path being the branch and true path being
520 * a fallthrough to the next instruction.
521 */
522 if (filter[i].jt == 0)
523 /* Swap the sense of the branch */
524 PPC_BCC(true_cond ^ COND_CMP_TRUE,
525 addrs[i + 1 + filter[i].jf]);
526 else {
527 PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
528 if (filter[i].jf != 0)
529 PPC_JMP(addrs[i + 1 + filter[i].jf]);
530 }
531 break;
532 default:
533 /* The filter contains something cruel & unusual.
534 * We don't handle it, but also there shouldn't be
535 * anything missing from our list.
536 */
537 if (printk_ratelimit())
538 pr_err("BPF filter opcode %04x (@%d) unsupported\n",
539 filter[i].code, i);
540 return -ENOTSUPP;
541 }
542
543 }
544 /* Set end-of-body-code address for exit. */
545 addrs[i] = ctx->idx * 4;
546
547 return 0;
548}
549
550void bpf_jit_compile(struct sk_filter *fp)
551{
552 unsigned int proglen;
553 unsigned int alloclen;
554 u32 *image = NULL;
555 u32 *code_base;
556 unsigned int *addrs;
557 struct codegen_context cgctx;
558 int pass;
559 int flen = fp->len;
560
561 if (!bpf_jit_enable)
562 return;
563
564 addrs = kzalloc((flen+1) * sizeof(*addrs), GFP_KERNEL);
565 if (addrs == NULL)
566 return;
567
568 /*
569 * There are multiple assembly passes as the generated code will change
570 * size as it settles down, figuring out the max branch offsets/exit
571 * paths required.
572 *
573 * The range of standard conditional branches is +/- 32Kbytes. Since
574 * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to
575 * finish with 8 bytes/instruction. Not feasible, so long jumps are
576 * used, distinct from short branches.
577 *
578 * Current:
579 *
580 * For now, both branch types assemble to 2 words (short branches padded
581 * with a NOP); this is less efficient, but assembly will always complete
582 * after exactly 3 passes:
583 *
584 * First pass: No code buffer; Program is "faux-generated" -- no code
585 * emitted but maximum size of output determined (and addrs[] filled
586 * in). Also, we note whether we use M[], whether we use skb data, etc.
587 * All generation choices assumed to be 'worst-case', e.g. branches all
588 * far (2 instructions), return path code reduction not available, etc.
589 *
590 * Second pass: Code buffer allocated with size determined previously.
591 * Prologue generated to support features we have seen used. Exit paths
592 * determined and addrs[] is filled in again, as code may be slightly
593 * smaller as a result.
594 *
595 * Third pass: Code generated 'for real', and branch destinations
596 * determined from now-accurate addrs[] map.
597 *
598 * Ideal:
599 *
600 * If we optimise this, near branches will be shorter. On the
601 * first assembly pass, we should err on the side of caution and
602 * generate the biggest code. On subsequent passes, branches will be
603 * generated short or long and code size will reduce. With smaller
604 * code, more branches may fall into the short category, and code will
605 * reduce more.
606 *
607 * Finally, if we see one pass generate code the same size as the
608 * previous pass we have converged and should now generate code for
609 * real. Allocating at the end will also save the memory that would
610 * otherwise be wasted by the (small) current code shrinkage.
611 * Preferably, we should do a small number of passes (e.g. 5) and if we
612 * haven't converged by then, get impatient and force code to generate
613 * as-is, even if the odd branch would be left long. The chances of a
614 * long jump are tiny with all but the most enormous of BPF filter
615 * inputs, so we should usually converge on the third pass.
616 */
617
618 cgctx.idx = 0;
619 cgctx.seen = 0;
620 cgctx.pc_ret0 = -1;
621 /* Scouting faux-generate pass 0 */
622 if (bpf_jit_build_body(fp, 0, &cgctx, addrs))
623 /* We hit something illegal or unsupported. */
624 goto out;
625
626 /*
627 * Pretend to build prologue, given the features we've seen. This will
628 * update ctgtx.idx as it pretends to output instructions, then we can
629 * calculate total size from idx.
630 */
631 bpf_jit_build_prologue(fp, 0, &cgctx);
632 bpf_jit_build_epilogue(0, &cgctx);
633
634 proglen = cgctx.idx * 4;
635 alloclen = proglen + FUNCTION_DESCR_SIZE;
636 image = module_alloc(max_t(unsigned int, alloclen,
637 sizeof(struct work_struct)));
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 pr_info("flen=%d proglen=%u pass=%d image=%p\n",
658 flen, proglen, pass, image);
659
660 if (image) {
661 if (bpf_jit_enable > 1)
662 print_hex_dump(KERN_ERR, "JIT code: ",
663 DUMP_PREFIX_ADDRESS,
664 16, 1, code_base,
665 proglen, false);
666
667 bpf_flush_icache(code_base, code_base + (proglen/4));
668 /* Function descriptor nastiness: Address + TOC */
669 ((u64 *)image)[0] = (u64)code_base;
670 ((u64 *)image)[1] = local_paca->kernel_toc;
671 fp->bpf_func = (void *)image;
672 }
673out:
674 kfree(addrs);
675 return;
676}
677
678static void jit_free_defer(struct work_struct *arg)
679{
680 module_free(NULL, arg);
681}
682
683/* run from softirq, we must use a work_struct to call
684 * module_free() from process context
685 */
686void bpf_jit_free(struct sk_filter *fp)
687{
688 if (fp->bpf_func != sk_run_filter) {
689 struct work_struct *work = (struct work_struct *)fp->bpf_func;
690
691 INIT_WORK(work, jit_free_defer);
692 schedule_work(work);
693 }
694}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * eBPF JIT compiler
4 *
5 * Copyright 2016 Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
6 * IBM Corporation
7 *
8 * Based on the powerpc classic BPF JIT compiler by Matt Evans
9 */
10#include <linux/moduleloader.h>
11#include <asm/cacheflush.h>
12#include <asm/asm-compat.h>
13#include <linux/netdevice.h>
14#include <linux/filter.h>
15#include <linux/if_vlan.h>
16#include <asm/kprobes.h>
17#include <linux/bpf.h>
18
19#include "bpf_jit.h"
20
21static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
22{
23 memset32(area, BREAKPOINT_INSTRUCTION, size / 4);
24}
25
26/* Fix updated addresses (for subprog calls, ldimm64, et al) during extra pass */
27static int bpf_jit_fixup_addresses(struct bpf_prog *fp, u32 *image,
28 struct codegen_context *ctx, u32 *addrs)
29{
30 const struct bpf_insn *insn = fp->insnsi;
31 bool func_addr_fixed;
32 u64 func_addr;
33 u32 tmp_idx;
34 int i, j, ret;
35
36 for (i = 0; i < fp->len; i++) {
37 /*
38 * During the extra pass, only the branch target addresses for
39 * the subprog calls need to be fixed. All other instructions
40 * can left untouched.
41 *
42 * The JITed image length does not change because we already
43 * ensure that the JITed instruction sequence for these calls
44 * are of fixed length by padding them with NOPs.
45 */
46 if (insn[i].code == (BPF_JMP | BPF_CALL) &&
47 insn[i].src_reg == BPF_PSEUDO_CALL) {
48 ret = bpf_jit_get_func_addr(fp, &insn[i], true,
49 &func_addr,
50 &func_addr_fixed);
51 if (ret < 0)
52 return ret;
53
54 /*
55 * Save ctx->idx as this would currently point to the
56 * end of the JITed image and set it to the offset of
57 * the instruction sequence corresponding to the
58 * subprog call temporarily.
59 */
60 tmp_idx = ctx->idx;
61 ctx->idx = addrs[i] / 4;
62 ret = bpf_jit_emit_func_call_rel(image, ctx, func_addr);
63 if (ret)
64 return ret;
65
66 /*
67 * Restore ctx->idx here. This is safe as the length
68 * of the JITed sequence remains unchanged.
69 */
70 ctx->idx = tmp_idx;
71 } else if (insn[i].code == (BPF_LD | BPF_IMM | BPF_DW)) {
72 tmp_idx = ctx->idx;
73 ctx->idx = addrs[i] / 4;
74#ifdef CONFIG_PPC32
75 PPC_LI32(bpf_to_ppc(insn[i].dst_reg) - 1, (u32)insn[i + 1].imm);
76 PPC_LI32(bpf_to_ppc(insn[i].dst_reg), (u32)insn[i].imm);
77 for (j = ctx->idx - addrs[i] / 4; j < 4; j++)
78 EMIT(PPC_RAW_NOP());
79#else
80 func_addr = ((u64)(u32)insn[i].imm) | (((u64)(u32)insn[i + 1].imm) << 32);
81 PPC_LI64(bpf_to_ppc(insn[i].dst_reg), func_addr);
82 /* overwrite rest with nops */
83 for (j = ctx->idx - addrs[i] / 4; j < 5; j++)
84 EMIT(PPC_RAW_NOP());
85#endif
86 ctx->idx = tmp_idx;
87 i++;
88 }
89 }
90
91 return 0;
92}
93
94int bpf_jit_emit_exit_insn(u32 *image, struct codegen_context *ctx, int tmp_reg, long exit_addr)
95{
96 if (!exit_addr || is_offset_in_branch_range(exit_addr - (ctx->idx * 4))) {
97 PPC_JMP(exit_addr);
98 } else if (ctx->alt_exit_addr) {
99 if (WARN_ON(!is_offset_in_branch_range((long)ctx->alt_exit_addr - (ctx->idx * 4))))
100 return -1;
101 PPC_JMP(ctx->alt_exit_addr);
102 } else {
103 ctx->alt_exit_addr = ctx->idx * 4;
104 bpf_jit_build_epilogue(image, ctx);
105 }
106
107 return 0;
108}
109
110struct powerpc64_jit_data {
111 struct bpf_binary_header *header;
112 u32 *addrs;
113 u8 *image;
114 u32 proglen;
115 struct codegen_context ctx;
116};
117
118bool bpf_jit_needs_zext(void)
119{
120 return true;
121}
122
123struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
124{
125 u32 proglen;
126 u32 alloclen;
127 u8 *image = NULL;
128 u32 *code_base;
129 u32 *addrs;
130 struct powerpc64_jit_data *jit_data;
131 struct codegen_context cgctx;
132 int pass;
133 int flen;
134 struct bpf_binary_header *bpf_hdr;
135 struct bpf_prog *org_fp = fp;
136 struct bpf_prog *tmp_fp;
137 bool bpf_blinded = false;
138 bool extra_pass = false;
139 u32 extable_len;
140 u32 fixup_len;
141
142 if (!fp->jit_requested)
143 return org_fp;
144
145 tmp_fp = bpf_jit_blind_constants(org_fp);
146 if (IS_ERR(tmp_fp))
147 return org_fp;
148
149 if (tmp_fp != org_fp) {
150 bpf_blinded = true;
151 fp = tmp_fp;
152 }
153
154 jit_data = fp->aux->jit_data;
155 if (!jit_data) {
156 jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL);
157 if (!jit_data) {
158 fp = org_fp;
159 goto out;
160 }
161 fp->aux->jit_data = jit_data;
162 }
163
164 flen = fp->len;
165 addrs = jit_data->addrs;
166 if (addrs) {
167 cgctx = jit_data->ctx;
168 image = jit_data->image;
169 bpf_hdr = jit_data->header;
170 proglen = jit_data->proglen;
171 extra_pass = true;
172 goto skip_init_ctx;
173 }
174
175 addrs = kcalloc(flen + 1, sizeof(*addrs), GFP_KERNEL);
176 if (addrs == NULL) {
177 fp = org_fp;
178 goto out_addrs;
179 }
180
181 memset(&cgctx, 0, sizeof(struct codegen_context));
182 bpf_jit_init_reg_mapping(&cgctx);
183
184 /* Make sure that the stack is quadword aligned. */
185 cgctx.stack_size = round_up(fp->aux->stack_depth, 16);
186
187 /* Scouting faux-generate pass 0 */
188 if (bpf_jit_build_body(fp, 0, &cgctx, addrs, 0)) {
189 /* We hit something illegal or unsupported. */
190 fp = org_fp;
191 goto out_addrs;
192 }
193
194 /*
195 * If we have seen a tail call, we need a second pass.
196 * This is because bpf_jit_emit_common_epilogue() is called
197 * from bpf_jit_emit_tail_call() with a not yet stable ctx->seen.
198 * We also need a second pass if we ended up with too large
199 * a program so as to ensure BPF_EXIT branches are in range.
200 */
201 if (cgctx.seen & SEEN_TAILCALL || !is_offset_in_branch_range((long)cgctx.idx * 4)) {
202 cgctx.idx = 0;
203 if (bpf_jit_build_body(fp, 0, &cgctx, addrs, 0)) {
204 fp = org_fp;
205 goto out_addrs;
206 }
207 }
208
209 bpf_jit_realloc_regs(&cgctx);
210 /*
211 * Pretend to build prologue, given the features we've seen. This will
212 * update ctgtx.idx as it pretends to output instructions, then we can
213 * calculate total size from idx.
214 */
215 bpf_jit_build_prologue(0, &cgctx);
216 addrs[fp->len] = cgctx.idx * 4;
217 bpf_jit_build_epilogue(0, &cgctx);
218
219 fixup_len = fp->aux->num_exentries * BPF_FIXUP_LEN * 4;
220 extable_len = fp->aux->num_exentries * sizeof(struct exception_table_entry);
221
222 proglen = cgctx.idx * 4;
223 alloclen = proglen + FUNCTION_DESCR_SIZE + fixup_len + extable_len;
224
225 bpf_hdr = bpf_jit_binary_alloc(alloclen, &image, 4, bpf_jit_fill_ill_insns);
226 if (!bpf_hdr) {
227 fp = org_fp;
228 goto out_addrs;
229 }
230
231 if (extable_len)
232 fp->aux->extable = (void *)image + FUNCTION_DESCR_SIZE + proglen + fixup_len;
233
234skip_init_ctx:
235 code_base = (u32 *)(image + FUNCTION_DESCR_SIZE);
236
237 if (extra_pass) {
238 /*
239 * Do not touch the prologue and epilogue as they will remain
240 * unchanged. Only fix the branch target address for subprog
241 * calls in the body, and ldimm64 instructions.
242 *
243 * This does not change the offsets and lengths of the subprog
244 * call instruction sequences and hence, the size of the JITed
245 * image as well.
246 */
247 bpf_jit_fixup_addresses(fp, code_base, &cgctx, addrs);
248
249 /* There is no need to perform the usual passes. */
250 goto skip_codegen_passes;
251 }
252
253 /* Code generation passes 1-2 */
254 for (pass = 1; pass < 3; pass++) {
255 /* Now build the prologue, body code & epilogue for real. */
256 cgctx.idx = 0;
257 cgctx.alt_exit_addr = 0;
258 bpf_jit_build_prologue(code_base, &cgctx);
259 if (bpf_jit_build_body(fp, code_base, &cgctx, addrs, pass)) {
260 bpf_jit_binary_free(bpf_hdr);
261 fp = org_fp;
262 goto out_addrs;
263 }
264 bpf_jit_build_epilogue(code_base, &cgctx);
265
266 if (bpf_jit_enable > 1)
267 pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
268 proglen - (cgctx.idx * 4), cgctx.seen);
269 }
270
271skip_codegen_passes:
272 if (bpf_jit_enable > 1)
273 /*
274 * Note that we output the base address of the code_base
275 * rather than image, since opcodes are in code_base.
276 */
277 bpf_jit_dump(flen, proglen, pass, code_base);
278
279#ifdef CONFIG_PPC64_ELF_ABI_V1
280 /* Function descriptor nastiness: Address + TOC */
281 ((u64 *)image)[0] = (u64)code_base;
282 ((u64 *)image)[1] = local_paca->kernel_toc;
283#endif
284
285 fp->bpf_func = (void *)image;
286 fp->jited = 1;
287 fp->jited_len = proglen + FUNCTION_DESCR_SIZE;
288
289 bpf_flush_icache(bpf_hdr, (u8 *)bpf_hdr + bpf_hdr->size);
290 if (!fp->is_func || extra_pass) {
291 bpf_jit_binary_lock_ro(bpf_hdr);
292 bpf_prog_fill_jited_linfo(fp, addrs);
293out_addrs:
294 kfree(addrs);
295 kfree(jit_data);
296 fp->aux->jit_data = NULL;
297 } else {
298 jit_data->addrs = addrs;
299 jit_data->ctx = cgctx;
300 jit_data->proglen = proglen;
301 jit_data->image = image;
302 jit_data->header = bpf_hdr;
303 }
304
305out:
306 if (bpf_blinded)
307 bpf_jit_prog_release_other(fp, fp == org_fp ? tmp_fp : org_fp);
308
309 return fp;
310}
311
312/*
313 * The caller should check for (BPF_MODE(code) == BPF_PROBE_MEM) before calling
314 * this function, as this only applies to BPF_PROBE_MEM, for now.
315 */
316int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, int pass, struct codegen_context *ctx,
317 int insn_idx, int jmp_off, int dst_reg)
318{
319 off_t offset;
320 unsigned long pc;
321 struct exception_table_entry *ex;
322 u32 *fixup;
323
324 /* Populate extable entries only in the last pass */
325 if (pass != 2)
326 return 0;
327
328 if (!fp->aux->extable ||
329 WARN_ON_ONCE(ctx->exentry_idx >= fp->aux->num_exentries))
330 return -EINVAL;
331
332 pc = (unsigned long)&image[insn_idx];
333
334 fixup = (void *)fp->aux->extable -
335 (fp->aux->num_exentries * BPF_FIXUP_LEN * 4) +
336 (ctx->exentry_idx * BPF_FIXUP_LEN * 4);
337
338 fixup[0] = PPC_RAW_LI(dst_reg, 0);
339 if (IS_ENABLED(CONFIG_PPC32))
340 fixup[1] = PPC_RAW_LI(dst_reg - 1, 0); /* clear higher 32-bit register too */
341
342 fixup[BPF_FIXUP_LEN - 1] =
343 PPC_RAW_BRANCH((long)(pc + jmp_off) - (long)&fixup[BPF_FIXUP_LEN - 1]);
344
345 ex = &fp->aux->extable[ctx->exentry_idx];
346
347 offset = pc - (long)&ex->insn;
348 if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN))
349 return -ERANGE;
350 ex->insn = offset;
351
352 offset = (long)fixup - (long)&ex->fixup;
353 if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN))
354 return -ERANGE;
355 ex->fixup = offset;
356
357 ctx->exentry_idx++;
358 return 0;
359}