1 /* bpf_jit_comp.c: BPF JIT compiler for PPC64
3 * Copyright 2011 Matt Evans <matt@ozlabs.org>, IBM Corporation
5 * Based on the x86 BPF compiler, by Eric Dumazet (eric.dumazet@gmail.com)
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
12 #include <linux/moduleloader.h>
13 #include <asm/cacheflush.h>
14 #include <linux/netdevice.h>
15 #include <linux/filter.h>
16 #include <linux/if_vlan.h>
21 /* There are endianness assumptions herein. */
22 #error "Little-endian PPC not supported in BPF compiler"
25 int bpf_jit_enable __read_mostly;
28 static inline void bpf_flush_icache(void *start, void *end)
31 flush_icache_range((unsigned long)start, (unsigned long)end);
34 static void bpf_jit_build_prologue(struct sk_filter *fp, u32 *image,
35 struct codegen_context *ctx)
38 const struct sock_filter *filter = fp->insns;
40 if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
42 if (ctx->seen & SEEN_DATAREF) {
43 /* If we call any helpers (for loads), save LR */
44 EMIT(PPC_INST_MFLR | __PPC_RT(R0));
47 /* Back up non-volatile regs. */
48 PPC_STD(r_D, 1, -(8*(32-r_D)));
49 PPC_STD(r_HL, 1, -(8*(32-r_HL)));
51 if (ctx->seen & SEEN_MEM) {
53 * Conditionally save regs r15-r31 as some will be used
56 for (i = r_M; i < (r_M+16); i++) {
57 if (ctx->seen & (1 << (i-r_M)))
58 PPC_STD(i, 1, -(8*(32-i)));
61 EMIT(PPC_INST_STDU | __PPC_RS(R1) | __PPC_RA(R1) |
62 (-BPF_PPC_STACKFRAME & 0xfffc));
65 if (ctx->seen & SEEN_DATAREF) {
67 * If this filter needs to access skb data,
68 * prepare r_D and r_HL:
69 * r_HL = skb->len - skb->data_len
72 PPC_LWZ_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
74 PPC_LWZ_OFFS(r_HL, r_skb, offsetof(struct sk_buff, len));
75 PPC_SUB(r_HL, r_HL, r_scratch1);
76 PPC_LD_OFFS(r_D, r_skb, offsetof(struct sk_buff, data));
79 if (ctx->seen & SEEN_XREG) {
81 * TODO: Could also detect whether first instr. sets X and
82 * avoid this (as below, with A).
87 switch (filter[0].code) {
90 case BPF_S_ANC_PROTOCOL:
91 case BPF_S_ANC_IFINDEX:
93 case BPF_S_ANC_RXHASH:
94 case BPF_S_ANC_VLAN_TAG:
95 case BPF_S_ANC_VLAN_TAG_PRESENT:
101 /* first instruction sets A register (or is RET 'constant') */
104 /* make sure we dont leak kernel information to user */
109 static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
113 if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) {
114 PPC_ADDI(1, 1, BPF_PPC_STACKFRAME);
115 if (ctx->seen & SEEN_DATAREF) {
118 PPC_LD(r_D, 1, -(8*(32-r_D)));
119 PPC_LD(r_HL, 1, -(8*(32-r_HL)));
121 if (ctx->seen & SEEN_MEM) {
122 /* Restore any saved non-vol registers */
123 for (i = r_M; i < (r_M+16); i++) {
124 if (ctx->seen & (1 << (i-r_M)))
125 PPC_LD(i, 1, -(8*(32-i)));
129 /* The RETs have left a return value in R3. */
134 #define CHOOSE_LOAD_FUNC(K, func) \
135 ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
137 /* Assemble the body code between the prologue & epilogue. */
138 static int bpf_jit_build_body(struct sk_filter *fp, u32 *image,
139 struct codegen_context *ctx,
142 const struct sock_filter *filter = fp->insns;
145 unsigned int true_cond;
148 /* Start of epilogue code */
149 unsigned int exit_addr = addrs[flen];
151 for (i = 0; i < flen; i++) {
152 unsigned int K = filter[i].k;
155 * addrs[] maps a BPF bytecode address into a real offset from
156 * the start of the body code.
158 addrs[i] = ctx->idx * 4;
160 switch (filter[i].code) {
162 case BPF_S_ALU_ADD_X: /* A += X; */
163 ctx->seen |= SEEN_XREG;
164 PPC_ADD(r_A, r_A, r_X);
166 case BPF_S_ALU_ADD_K: /* A += K; */
169 PPC_ADDI(r_A, r_A, IMM_L(K));
171 PPC_ADDIS(r_A, r_A, IMM_HA(K));
173 case BPF_S_ALU_SUB_X: /* A -= X; */
174 ctx->seen |= SEEN_XREG;
175 PPC_SUB(r_A, r_A, r_X);
177 case BPF_S_ALU_SUB_K: /* A -= K */
180 PPC_ADDI(r_A, r_A, IMM_L(-K));
182 PPC_ADDIS(r_A, r_A, IMM_HA(-K));
184 case BPF_S_ALU_MUL_X: /* A *= X; */
185 ctx->seen |= SEEN_XREG;
186 PPC_MUL(r_A, r_A, r_X);
188 case BPF_S_ALU_MUL_K: /* A *= K */
190 PPC_MULI(r_A, r_A, K);
192 PPC_LI32(r_scratch1, K);
193 PPC_MUL(r_A, r_A, r_scratch1);
196 case BPF_S_ALU_DIV_X: /* A /= X; */
197 ctx->seen |= SEEN_XREG;
199 if (ctx->pc_ret0 != -1) {
200 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
203 * Exit, returning 0; first pass hits here
204 * (longer worst-case code size).
206 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
210 PPC_DIVWU(r_A, r_A, r_X);
212 case BPF_S_ALU_DIV_K: /* A = reciprocal_divide(A, K); */
213 PPC_LI32(r_scratch1, K);
214 /* Top 32 bits of 64bit result -> A */
215 PPC_MULHWU(r_A, r_A, r_scratch1);
217 case BPF_S_ALU_AND_X:
218 ctx->seen |= SEEN_XREG;
219 PPC_AND(r_A, r_A, r_X);
221 case BPF_S_ALU_AND_K:
223 PPC_ANDI(r_A, r_A, K);
225 PPC_LI32(r_scratch1, K);
226 PPC_AND(r_A, r_A, r_scratch1);
230 ctx->seen |= SEEN_XREG;
231 PPC_OR(r_A, r_A, r_X);
235 PPC_ORI(r_A, r_A, IMM_L(K));
237 PPC_ORIS(r_A, r_A, IMM_H(K));
239 case BPF_S_ANC_ALU_XOR_X:
240 case BPF_S_ALU_XOR_X: /* A ^= X */
241 ctx->seen |= SEEN_XREG;
242 PPC_XOR(r_A, r_A, r_X);
244 case BPF_S_ALU_XOR_K: /* A ^= K */
246 PPC_XORI(r_A, r_A, IMM_L(K));
248 PPC_XORIS(r_A, r_A, IMM_H(K));
250 case BPF_S_ALU_LSH_X: /* A <<= X; */
251 ctx->seen |= SEEN_XREG;
252 PPC_SLW(r_A, r_A, r_X);
254 case BPF_S_ALU_LSH_K:
258 PPC_SLWI(r_A, r_A, K);
260 case BPF_S_ALU_RSH_X: /* A >>= X; */
261 ctx->seen |= SEEN_XREG;
262 PPC_SRW(r_A, r_A, r_X);
264 case BPF_S_ALU_RSH_K: /* A >>= K; */
268 PPC_SRWI(r_A, r_A, K);
276 if (ctx->pc_ret0 == -1)
280 * If this isn't the very last instruction, branch to
281 * the epilogue if we've stuff to clean up. Otherwise,
282 * if there's nothing to tidy, just return. If we /are/
283 * the last instruction, we're about to fall through to
284 * the epilogue to return.
288 * Note: 'seen' is properly valid only on pass
289 * #2. Both parts of this conditional are the
290 * same instruction size though, meaning the
291 * first pass will still correctly determine the
292 * code size/addresses.
309 case BPF_S_MISC_TAX: /* X = A */
312 case BPF_S_MISC_TXA: /* A = X */
313 ctx->seen |= SEEN_XREG;
317 /*** Constant loads/M[] access ***/
318 case BPF_S_LD_IMM: /* A = K */
321 case BPF_S_LDX_IMM: /* X = K */
324 case BPF_S_LD_MEM: /* A = mem[K] */
325 PPC_MR(r_A, r_M + (K & 0xf));
326 ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
328 case BPF_S_LDX_MEM: /* X = mem[K] */
329 PPC_MR(r_X, r_M + (K & 0xf));
330 ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
332 case BPF_S_ST: /* mem[K] = A */
333 PPC_MR(r_M + (K & 0xf), r_A);
334 ctx->seen |= SEEN_MEM | (1<<(K & 0xf));
336 case BPF_S_STX: /* mem[K] = X */
337 PPC_MR(r_M + (K & 0xf), r_X);
338 ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf));
340 case BPF_S_LD_W_LEN: /* A = skb->len; */
341 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
342 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len));
344 case BPF_S_LDX_W_LEN: /* X = skb->len; */
345 PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len));
348 /*** Ancillary info loads ***/
350 /* None of the BPF_S_ANC* codes appear to be passed by
351 * sk_chk_filter(). The interpreter and the x86 BPF
352 * compiler implement them so we do too -- they may be
355 case BPF_S_ANC_PROTOCOL: /* A = ntohs(skb->protocol); */
356 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
358 PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
360 /* ntohs is a NOP with BE loads. */
362 case BPF_S_ANC_IFINDEX:
363 PPC_LD_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff,
365 PPC_CMPDI(r_scratch1, 0);
366 if (ctx->pc_ret0 != -1) {
367 PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
369 /* Exit, returning 0; first pass hits here. */
370 PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
374 BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
376 PPC_LWZ_OFFS(r_A, r_scratch1,
377 offsetof(struct net_device, ifindex));
380 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
381 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
384 case BPF_S_ANC_RXHASH:
385 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, rxhash) != 4);
386 PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
389 case BPF_S_ANC_VLAN_TAG:
390 case BPF_S_ANC_VLAN_TAG_PRESENT:
391 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
392 PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
394 if (filter[i].code == BPF_S_ANC_VLAN_TAG)
395 PPC_ANDI(r_A, r_A, VLAN_VID_MASK);
397 PPC_ANDI(r_A, r_A, VLAN_TAG_PRESENT);
399 case BPF_S_ANC_QUEUE:
400 BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
401 queue_mapping) != 2);
402 PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff,
409 * raw_smp_processor_id() = local_paca->paca_index
411 BUILD_BUG_ON(FIELD_SIZEOF(struct paca_struct,
413 PPC_LHZ_OFFS(r_A, 13,
414 offsetof(struct paca_struct, paca_index));
420 /*** Absolute loads from packet header/data ***/
422 func = CHOOSE_LOAD_FUNC(K, sk_load_word);
425 func = CHOOSE_LOAD_FUNC(K, sk_load_half);
428 func = CHOOSE_LOAD_FUNC(K, sk_load_byte);
431 ctx->seen |= SEEN_DATAREF;
432 PPC_LI64(r_scratch1, func);
433 PPC_MTLR(r_scratch1);
437 * Helper returns 'lt' condition on error, and an
438 * appropriate return value in r3
440 PPC_BCC(COND_LT, exit_addr);
443 /*** Indirect loads from packet header/data ***/
446 goto common_load_ind;
449 goto common_load_ind;
454 * Load from [X + K]. Negative offsets are tested for
455 * in the helper functions.
457 ctx->seen |= SEEN_DATAREF | SEEN_XREG;
458 PPC_LI64(r_scratch1, func);
459 PPC_MTLR(r_scratch1);
460 PPC_ADDI(r_addr, r_X, IMM_L(K));
462 PPC_ADDIS(r_addr, r_addr, IMM_HA(K));
464 /* If error, cr0.LT set */
465 PPC_BCC(COND_LT, exit_addr);
468 case BPF_S_LDX_B_MSH:
469 func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh);
473 /*** Jump and branches ***/
476 PPC_JMP(addrs[i + 1 + K]);
479 case BPF_S_JMP_JGT_K:
480 case BPF_S_JMP_JGT_X:
483 case BPF_S_JMP_JGE_K:
484 case BPF_S_JMP_JGE_X:
487 case BPF_S_JMP_JEQ_K:
488 case BPF_S_JMP_JEQ_X:
491 case BPF_S_JMP_JSET_K:
492 case BPF_S_JMP_JSET_X:
496 /* same targets, can avoid doing the test :) */
497 if (filter[i].jt == filter[i].jf) {
498 if (filter[i].jt > 0)
499 PPC_JMP(addrs[i + 1 + filter[i].jt]);
503 switch (filter[i].code) {
504 case BPF_S_JMP_JGT_X:
505 case BPF_S_JMP_JGE_X:
506 case BPF_S_JMP_JEQ_X:
507 ctx->seen |= SEEN_XREG;
510 case BPF_S_JMP_JSET_X:
511 ctx->seen |= SEEN_XREG;
512 PPC_AND_DOT(r_scratch1, r_A, r_X);
514 case BPF_S_JMP_JEQ_K:
515 case BPF_S_JMP_JGT_K:
516 case BPF_S_JMP_JGE_K:
520 PPC_LI32(r_scratch1, K);
521 PPC_CMPLW(r_A, r_scratch1);
524 case BPF_S_JMP_JSET_K:
526 /* PPC_ANDI is /only/ dot-form */
527 PPC_ANDI(r_scratch1, r_A, K);
529 PPC_LI32(r_scratch1, K);
530 PPC_AND_DOT(r_scratch1, r_A,
535 /* Sometimes branches are constructed "backward", with
536 * the false path being the branch and true path being
537 * a fallthrough to the next instruction.
539 if (filter[i].jt == 0)
540 /* Swap the sense of the branch */
541 PPC_BCC(true_cond ^ COND_CMP_TRUE,
542 addrs[i + 1 + filter[i].jf]);
544 PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]);
545 if (filter[i].jf != 0)
546 PPC_JMP(addrs[i + 1 + filter[i].jf]);
550 /* The filter contains something cruel & unusual.
551 * We don't handle it, but also there shouldn't be
552 * anything missing from our list.
554 if (printk_ratelimit())
555 pr_err("BPF filter opcode %04x (@%d) unsupported\n",
561 /* Set end-of-body-code address for exit. */
562 addrs[i] = ctx->idx * 4;
567 void bpf_jit_compile(struct sk_filter *fp)
569 unsigned int proglen;
570 unsigned int alloclen;
574 struct codegen_context cgctx;
581 addrs = kzalloc((flen+1) * sizeof(*addrs), GFP_KERNEL);
586 * There are multiple assembly passes as the generated code will change
587 * size as it settles down, figuring out the max branch offsets/exit
590 * The range of standard conditional branches is +/- 32Kbytes. Since
591 * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to
592 * finish with 8 bytes/instruction. Not feasible, so long jumps are
593 * used, distinct from short branches.
597 * For now, both branch types assemble to 2 words (short branches padded
598 * with a NOP); this is less efficient, but assembly will always complete
599 * after exactly 3 passes:
601 * First pass: No code buffer; Program is "faux-generated" -- no code
602 * emitted but maximum size of output determined (and addrs[] filled
603 * in). Also, we note whether we use M[], whether we use skb data, etc.
604 * All generation choices assumed to be 'worst-case', e.g. branches all
605 * far (2 instructions), return path code reduction not available, etc.
607 * Second pass: Code buffer allocated with size determined previously.
608 * Prologue generated to support features we have seen used. Exit paths
609 * determined and addrs[] is filled in again, as code may be slightly
610 * smaller as a result.
612 * Third pass: Code generated 'for real', and branch destinations
613 * determined from now-accurate addrs[] map.
617 * If we optimise this, near branches will be shorter. On the
618 * first assembly pass, we should err on the side of caution and
619 * generate the biggest code. On subsequent passes, branches will be
620 * generated short or long and code size will reduce. With smaller
621 * code, more branches may fall into the short category, and code will
624 * Finally, if we see one pass generate code the same size as the
625 * previous pass we have converged and should now generate code for
626 * real. Allocating at the end will also save the memory that would
627 * otherwise be wasted by the (small) current code shrinkage.
628 * Preferably, we should do a small number of passes (e.g. 5) and if we
629 * haven't converged by then, get impatient and force code to generate
630 * as-is, even if the odd branch would be left long. The chances of a
631 * long jump are tiny with all but the most enormous of BPF filter
632 * inputs, so we should usually converge on the third pass.
638 /* Scouting faux-generate pass 0 */
639 if (bpf_jit_build_body(fp, 0, &cgctx, addrs))
640 /* We hit something illegal or unsupported. */
644 * Pretend to build prologue, given the features we've seen. This will
645 * update ctgtx.idx as it pretends to output instructions, then we can
646 * calculate total size from idx.
648 bpf_jit_build_prologue(fp, 0, &cgctx);
649 bpf_jit_build_epilogue(0, &cgctx);
651 proglen = cgctx.idx * 4;
652 alloclen = proglen + FUNCTION_DESCR_SIZE;
653 image = module_alloc(max_t(unsigned int, alloclen,
654 sizeof(struct work_struct)));
658 code_base = image + (FUNCTION_DESCR_SIZE/4);
660 /* Code generation passes 1-2 */
661 for (pass = 1; pass < 3; pass++) {
662 /* Now build the prologue, body code & epilogue for real. */
664 bpf_jit_build_prologue(fp, code_base, &cgctx);
665 bpf_jit_build_body(fp, code_base, &cgctx, addrs);
666 bpf_jit_build_epilogue(code_base, &cgctx);
668 if (bpf_jit_enable > 1)
669 pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
670 proglen - (cgctx.idx * 4), cgctx.seen);
673 if (bpf_jit_enable > 1)
674 pr_info("flen=%d proglen=%u pass=%d image=%p\n",
675 flen, proglen, pass, image);
678 if (bpf_jit_enable > 1)
679 print_hex_dump(KERN_ERR, "JIT code: ",
684 bpf_flush_icache(code_base, code_base + (proglen/4));
685 /* Function descriptor nastiness: Address + TOC */
686 ((u64 *)image)[0] = (u64)code_base;
687 ((u64 *)image)[1] = local_paca->kernel_toc;
688 fp->bpf_func = (void *)image;
695 static void jit_free_defer(struct work_struct *arg)
697 module_free(NULL, arg);
700 /* run from softirq, we must use a work_struct to call
701 * module_free() from process context
703 void bpf_jit_free(struct sk_filter *fp)
705 if (fp->bpf_func != sk_run_filter) {
706 struct work_struct *work = (struct work_struct *)fp->bpf_func;
708 INIT_WORK(work, jit_free_defer);