/* bpf_jit_comp.c: BPF JIT compiler for PPC64 * * Copyright 2011 Matt Evans , IBM Corporation * * Based on the x86 BPF compiler, by Eric Dumazet (eric.dumazet@gmail.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; version 2 * of the License. */ #include #include #include #include #include #include "bpf_jit.h" #ifndef __BIG_ENDIAN /* There are endianness assumptions herein. */ #error "Little-endian PPC not supported in BPF compiler" #endif int bpf_jit_enable __read_mostly; static inline void bpf_flush_icache(void *start, void *end) { smp_wmb(); flush_icache_range((unsigned long)start, (unsigned long)end); } static void bpf_jit_build_prologue(struct sk_filter *fp, u32 *image, struct codegen_context *ctx) { int i; const struct sock_filter *filter = fp->insns; if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) { /* Make stackframe */ if (ctx->seen & SEEN_DATAREF) { /* If we call any helpers (for loads), save LR */ EMIT(PPC_INST_MFLR | __PPC_RT(R0)); PPC_STD(0, 1, 16); /* Back up non-volatile regs. */ PPC_STD(r_D, 1, -(8*(32-r_D))); PPC_STD(r_HL, 1, -(8*(32-r_HL))); } if (ctx->seen & SEEN_MEM) { /* * Conditionally save regs r15-r31 as some will be used * for M[] data. */ for (i = r_M; i < (r_M+16); i++) { if (ctx->seen & (1 << (i-r_M))) PPC_STD(i, 1, -(8*(32-i))); } } EMIT(PPC_INST_STDU | __PPC_RS(R1) | __PPC_RA(R1) | (-BPF_PPC_STACKFRAME & 0xfffc)); } if (ctx->seen & SEEN_DATAREF) { /* * If this filter needs to access skb data, * prepare r_D and r_HL: * r_HL = skb->len - skb->data_len * r_D = skb->data */ PPC_LWZ_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff, data_len)); PPC_LWZ_OFFS(r_HL, r_skb, offsetof(struct sk_buff, len)); PPC_SUB(r_HL, r_HL, r_scratch1); PPC_LD_OFFS(r_D, r_skb, offsetof(struct sk_buff, data)); } if (ctx->seen & SEEN_XREG) { /* * TODO: Could also detect whether first instr. sets X and * avoid this (as below, with A). */ PPC_LI(r_X, 0); } switch (filter[0].code) { case BPF_S_RET_K: case BPF_S_LD_W_LEN: case BPF_S_ANC_PROTOCOL: case BPF_S_ANC_IFINDEX: case BPF_S_ANC_MARK: case BPF_S_ANC_RXHASH: case BPF_S_ANC_VLAN_TAG: case BPF_S_ANC_VLAN_TAG_PRESENT: case BPF_S_ANC_CPU: case BPF_S_ANC_QUEUE: case BPF_S_LD_W_ABS: case BPF_S_LD_H_ABS: case BPF_S_LD_B_ABS: /* first instruction sets A register (or is RET 'constant') */ break; default: /* make sure we dont leak kernel information to user */ PPC_LI(r_A, 0); } } static void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx) { int i; if (ctx->seen & (SEEN_MEM | SEEN_DATAREF)) { PPC_ADDI(1, 1, BPF_PPC_STACKFRAME); if (ctx->seen & SEEN_DATAREF) { PPC_LD(0, 1, 16); PPC_MTLR(0); PPC_LD(r_D, 1, -(8*(32-r_D))); PPC_LD(r_HL, 1, -(8*(32-r_HL))); } if (ctx->seen & SEEN_MEM) { /* Restore any saved non-vol registers */ for (i = r_M; i < (r_M+16); i++) { if (ctx->seen & (1 << (i-r_M))) PPC_LD(i, 1, -(8*(32-i))); } } } /* The RETs have left a return value in R3. */ PPC_BLR(); } #define CHOOSE_LOAD_FUNC(K, func) \ ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset) /* Assemble the body code between the prologue & epilogue. */ static int bpf_jit_build_body(struct sk_filter *fp, u32 *image, struct codegen_context *ctx, unsigned int *addrs) { const struct sock_filter *filter = fp->insns; int flen = fp->len; u8 *func; unsigned int true_cond; int i; /* Start of epilogue code */ unsigned int exit_addr = addrs[flen]; for (i = 0; i < flen; i++) { unsigned int K = filter[i].k; /* * addrs[] maps a BPF bytecode address into a real offset from * the start of the body code. */ addrs[i] = ctx->idx * 4; switch (filter[i].code) { /*** ALU ops ***/ case BPF_S_ALU_ADD_X: /* A += X; */ ctx->seen |= SEEN_XREG; PPC_ADD(r_A, r_A, r_X); break; case BPF_S_ALU_ADD_K: /* A += K; */ if (!K) break; PPC_ADDI(r_A, r_A, IMM_L(K)); if (K >= 32768) PPC_ADDIS(r_A, r_A, IMM_HA(K)); break; case BPF_S_ALU_SUB_X: /* A -= X; */ ctx->seen |= SEEN_XREG; PPC_SUB(r_A, r_A, r_X); break; case BPF_S_ALU_SUB_K: /* A -= K */ if (!K) break; PPC_ADDI(r_A, r_A, IMM_L(-K)); if (K >= 32768) PPC_ADDIS(r_A, r_A, IMM_HA(-K)); break; case BPF_S_ALU_MUL_X: /* A *= X; */ ctx->seen |= SEEN_XREG; PPC_MUL(r_A, r_A, r_X); break; case BPF_S_ALU_MUL_K: /* A *= K */ if (K < 32768) PPC_MULI(r_A, r_A, K); else { PPC_LI32(r_scratch1, K); PPC_MUL(r_A, r_A, r_scratch1); } break; case BPF_S_ALU_DIV_X: /* A /= X; */ ctx->seen |= SEEN_XREG; PPC_CMPWI(r_X, 0); if (ctx->pc_ret0 != -1) { PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]); } else { /* * Exit, returning 0; first pass hits here * (longer worst-case code size). */ PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12); PPC_LI(r_ret, 0); PPC_JMP(exit_addr); } PPC_DIVWU(r_A, r_A, r_X); break; case BPF_S_ALU_DIV_K: /* A /= K */ if (K == 1) break; PPC_LI32(r_scratch1, K); PPC_DIVWU(r_A, r_A, r_scratch1); break; case BPF_S_ALU_AND_X: ctx->seen |= SEEN_XREG; PPC_AND(r_A, r_A, r_X); break; case BPF_S_ALU_AND_K: if (!IMM_H(K)) PPC_ANDI(r_A, r_A, K); else { PPC_LI32(r_scratch1, K); PPC_AND(r_A, r_A, r_scratch1); } break; case BPF_S_ALU_OR_X: ctx->seen |= SEEN_XREG; PPC_OR(r_A, r_A, r_X); break; case BPF_S_ALU_OR_K: if (IMM_L(K)) PPC_ORI(r_A, r_A, IMM_L(K)); if (K >= 65536) PPC_ORIS(r_A, r_A, IMM_H(K)); break; case BPF_S_ANC_ALU_XOR_X: case BPF_S_ALU_XOR_X: /* A ^= X */ ctx->seen |= SEEN_XREG; PPC_XOR(r_A, r_A, r_X); break; case BPF_S_ALU_XOR_K: /* A ^= K */ if (IMM_L(K)) PPC_XORI(r_A, r_A, IMM_L(K)); if (K >= 65536) PPC_XORIS(r_A, r_A, IMM_H(K)); break; case BPF_S_ALU_LSH_X: /* A <<= X; */ ctx->seen |= SEEN_XREG; PPC_SLW(r_A, r_A, r_X); break; case BPF_S_ALU_LSH_K: if (K == 0) break; else PPC_SLWI(r_A, r_A, K); break; case BPF_S_ALU_RSH_X: /* A >>= X; */ ctx->seen |= SEEN_XREG; PPC_SRW(r_A, r_A, r_X); break; case BPF_S_ALU_RSH_K: /* A >>= K; */ if (K == 0) break; else PPC_SRWI(r_A, r_A, K); break; case BPF_S_ALU_NEG: PPC_NEG(r_A, r_A); break; case BPF_S_RET_K: PPC_LI32(r_ret, K); if (!K) { if (ctx->pc_ret0 == -1) ctx->pc_ret0 = i; } /* * If this isn't the very last instruction, branch to * the epilogue if we've stuff to clean up. Otherwise, * if there's nothing to tidy, just return. If we /are/ * the last instruction, we're about to fall through to * the epilogue to return. */ if (i != flen - 1) { /* * Note: 'seen' is properly valid only on pass * #2. Both parts of this conditional are the * same instruction size though, meaning the * first pass will still correctly determine the * code size/addresses. */ if (ctx->seen) PPC_JMP(exit_addr); else PPC_BLR(); } break; case BPF_S_RET_A: PPC_MR(r_ret, r_A); if (i != flen - 1) { if (ctx->seen) PPC_JMP(exit_addr); else PPC_BLR(); } break; case BPF_S_MISC_TAX: /* X = A */ PPC_MR(r_X, r_A); break; case BPF_S_MISC_TXA: /* A = X */ ctx->seen |= SEEN_XREG; PPC_MR(r_A, r_X); break; /*** Constant loads/M[] access ***/ case BPF_S_LD_IMM: /* A = K */ PPC_LI32(r_A, K); break; case BPF_S_LDX_IMM: /* X = K */ PPC_LI32(r_X, K); break; case BPF_S_LD_MEM: /* A = mem[K] */ PPC_MR(r_A, r_M + (K & 0xf)); ctx->seen |= SEEN_MEM | (1<<(K & 0xf)); break; case BPF_S_LDX_MEM: /* X = mem[K] */ PPC_MR(r_X, r_M + (K & 0xf)); ctx->seen |= SEEN_MEM | (1<<(K & 0xf)); break; case BPF_S_ST: /* mem[K] = A */ PPC_MR(r_M + (K & 0xf), r_A); ctx->seen |= SEEN_MEM | (1<<(K & 0xf)); break; case BPF_S_STX: /* mem[K] = X */ PPC_MR(r_M + (K & 0xf), r_X); ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf)); break; case BPF_S_LD_W_LEN: /* A = skb->len; */ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4); PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, len)); break; case BPF_S_LDX_W_LEN: /* X = skb->len; */ PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len)); break; /*** Ancillary info loads ***/ /* None of the BPF_S_ANC* codes appear to be passed by * sk_chk_filter(). The interpreter and the x86 BPF * compiler implement them so we do too -- they may be * planted in future. */ case BPF_S_ANC_PROTOCOL: /* A = ntohs(skb->protocol); */ BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2); PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, protocol)); /* ntohs is a NOP with BE loads. */ break; case BPF_S_ANC_IFINDEX: PPC_LD_OFFS(r_scratch1, r_skb, offsetof(struct sk_buff, dev)); PPC_CMPDI(r_scratch1, 0); if (ctx->pc_ret0 != -1) { PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]); } else { /* Exit, returning 0; first pass hits here. */ PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12); PPC_LI(r_ret, 0); PPC_JMP(exit_addr); } BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4); PPC_LWZ_OFFS(r_A, r_scratch1, offsetof(struct net_device, ifindex)); break; case BPF_S_ANC_MARK: BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4); PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, mark)); break; case BPF_S_ANC_RXHASH: BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, rxhash) != 4); PPC_LWZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, rxhash)); break; case BPF_S_ANC_VLAN_TAG: case BPF_S_ANC_VLAN_TAG_PRESENT: BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2); PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, vlan_tci)); if (filter[i].code == BPF_S_ANC_VLAN_TAG) PPC_ANDI(r_A, r_A, VLAN_VID_MASK); else PPC_ANDI(r_A, r_A, VLAN_TAG_PRESENT); break; case BPF_S_ANC_QUEUE: BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, queue_mapping) != 2); PPC_LHZ_OFFS(r_A, r_skb, offsetof(struct sk_buff, queue_mapping)); break; case BPF_S_ANC_CPU: #ifdef CONFIG_SMP /* * PACA ptr is r13: * raw_smp_processor_id() = local_paca->paca_index */ BUILD_BUG_ON(FIELD_SIZEOF(struct paca_struct, paca_index) != 2); PPC_LHZ_OFFS(r_A, 13, offsetof(struct paca_struct, paca_index)); #else PPC_LI(r_A, 0); #endif break; /*** Absolute loads from packet header/data ***/ case BPF_S_LD_W_ABS: func = CHOOSE_LOAD_FUNC(K, sk_load_word); goto common_load; case BPF_S_LD_H_ABS: func = CHOOSE_LOAD_FUNC(K, sk_load_half); goto common_load; case BPF_S_LD_B_ABS: func = CHOOSE_LOAD_FUNC(K, sk_load_byte); common_load: /* Load from [K]. */ ctx->seen |= SEEN_DATAREF; PPC_LI64(r_scratch1, func); PPC_MTLR(r_scratch1); PPC_LI32(r_addr, K); PPC_BLRL(); /* * Helper returns 'lt' condition on error, and an * appropriate return value in r3 */ PPC_BCC(COND_LT, exit_addr); break; /*** Indirect loads from packet header/data ***/ case BPF_S_LD_W_IND: func = sk_load_word; goto common_load_ind; case BPF_S_LD_H_IND: func = sk_load_half; goto common_load_ind; case BPF_S_LD_B_IND: func = sk_load_byte; common_load_ind: /* * Load from [X + K]. Negative offsets are tested for * in the helper functions. */ ctx->seen |= SEEN_DATAREF | SEEN_XREG; PPC_LI64(r_scratch1, func); PPC_MTLR(r_scratch1); PPC_ADDI(r_addr, r_X, IMM_L(K)); if (K >= 32768) PPC_ADDIS(r_addr, r_addr, IMM_HA(K)); PPC_BLRL(); /* If error, cr0.LT set */ PPC_BCC(COND_LT, exit_addr); break; case BPF_S_LDX_B_MSH: func = CHOOSE_LOAD_FUNC(K, sk_load_byte_msh); goto common_load; break; /*** Jump and branches ***/ case BPF_S_JMP_JA: if (K != 0) PPC_JMP(addrs[i + 1 + K]); break; case BPF_S_JMP_JGT_K: case BPF_S_JMP_JGT_X: true_cond = COND_GT; goto cond_branch; case BPF_S_JMP_JGE_K: case BPF_S_JMP_JGE_X: true_cond = COND_GE; goto cond_branch; case BPF_S_JMP_JEQ_K: case BPF_S_JMP_JEQ_X: true_cond = COND_EQ; goto cond_branch; case BPF_S_JMP_JSET_K: case BPF_S_JMP_JSET_X: true_cond = COND_NE; /* Fall through */ cond_branch: /* same targets, can avoid doing the test :) */ if (filter[i].jt == filter[i].jf) { if (filter[i].jt > 0) PPC_JMP(addrs[i + 1 + filter[i].jt]); break; } switch (filter[i].code) { case BPF_S_JMP_JGT_X: case BPF_S_JMP_JGE_X: case BPF_S_JMP_JEQ_X: ctx->seen |= SEEN_XREG; PPC_CMPLW(r_A, r_X); break; case BPF_S_JMP_JSET_X: ctx->seen |= SEEN_XREG; PPC_AND_DOT(r_scratch1, r_A, r_X); break; case BPF_S_JMP_JEQ_K: case BPF_S_JMP_JGT_K: case BPF_S_JMP_JGE_K: if (K < 32768) PPC_CMPLWI(r_A, K); else { PPC_LI32(r_scratch1, K); PPC_CMPLW(r_A, r_scratch1); } break; case BPF_S_JMP_JSET_K: if (K < 32768) /* PPC_ANDI is /only/ dot-form */ PPC_ANDI(r_scratch1, r_A, K); else { PPC_LI32(r_scratch1, K); PPC_AND_DOT(r_scratch1, r_A, r_scratch1); } break; } /* Sometimes branches are constructed "backward", with * the false path being the branch and true path being * a fallthrough to the next instruction. */ if (filter[i].jt == 0) /* Swap the sense of the branch */ PPC_BCC(true_cond ^ COND_CMP_TRUE, addrs[i + 1 + filter[i].jf]); else { PPC_BCC(true_cond, addrs[i + 1 + filter[i].jt]); if (filter[i].jf != 0) PPC_JMP(addrs[i + 1 + filter[i].jf]); } break; default: /* The filter contains something cruel & unusual. * We don't handle it, but also there shouldn't be * anything missing from our list. */ if (printk_ratelimit()) pr_err("BPF filter opcode %04x (@%d) unsupported\n", filter[i].code, i); return -ENOTSUPP; } } /* Set end-of-body-code address for exit. */ addrs[i] = ctx->idx * 4; return 0; } void bpf_jit_compile(struct sk_filter *fp) { unsigned int proglen; unsigned int alloclen; u32 *image = NULL; u32 *code_base; unsigned int *addrs; struct codegen_context cgctx; int pass; int flen = fp->len; if (!bpf_jit_enable) return; addrs = kzalloc((flen+1) * sizeof(*addrs), GFP_KERNEL); if (addrs == NULL) return; /* * There are multiple assembly passes as the generated code will change * size as it settles down, figuring out the max branch offsets/exit * paths required. * * The range of standard conditional branches is +/- 32Kbytes. Since * BPF_MAXINSNS = 4096, we can only jump from (worst case) start to * finish with 8 bytes/instruction. Not feasible, so long jumps are * used, distinct from short branches. * * Current: * * For now, both branch types assemble to 2 words (short branches padded * with a NOP); this is less efficient, but assembly will always complete * after exactly 3 passes: * * First pass: No code buffer; Program is "faux-generated" -- no code * emitted but maximum size of output determined (and addrs[] filled * in). Also, we note whether we use M[], whether we use skb data, etc. * All generation choices assumed to be 'worst-case', e.g. branches all * far (2 instructions), return path code reduction not available, etc. * * Second pass: Code buffer allocated with size determined previously. * Prologue generated to support features we have seen used. Exit paths * determined and addrs[] is filled in again, as code may be slightly * smaller as a result. * * Third pass: Code generated 'for real', and branch destinations * determined from now-accurate addrs[] map. * * Ideal: * * If we optimise this, near branches will be shorter. On the * first assembly pass, we should err on the side of caution and * generate the biggest code. On subsequent passes, branches will be * generated short or long and code size will reduce. With smaller * code, more branches may fall into the short category, and code will * reduce more. * * Finally, if we see one pass generate code the same size as the * previous pass we have converged and should now generate code for * real. Allocating at the end will also save the memory that would * otherwise be wasted by the (small) current code shrinkage. * Preferably, we should do a small number of passes (e.g. 5) and if we * haven't converged by then, get impatient and force code to generate * as-is, even if the odd branch would be left long. The chances of a * long jump are tiny with all but the most enormous of BPF filter * inputs, so we should usually converge on the third pass. */ cgctx.idx = 0; cgctx.seen = 0; cgctx.pc_ret0 = -1; /* Scouting faux-generate pass 0 */ if (bpf_jit_build_body(fp, 0, &cgctx, addrs)) /* We hit something illegal or unsupported. */ goto out; /* * Pretend to build prologue, given the features we've seen. This will * update ctgtx.idx as it pretends to output instructions, then we can * calculate total size from idx. */ bpf_jit_build_prologue(fp, 0, &cgctx); bpf_jit_build_epilogue(0, &cgctx); proglen = cgctx.idx * 4; alloclen = proglen + FUNCTION_DESCR_SIZE; image = module_alloc(alloclen); if (!image) goto out; code_base = image + (FUNCTION_DESCR_SIZE/4); /* Code generation passes 1-2 */ for (pass = 1; pass < 3; pass++) { /* Now build the prologue, body code & epilogue for real. */ cgctx.idx = 0; bpf_jit_build_prologue(fp, code_base, &cgctx); bpf_jit_build_body(fp, code_base, &cgctx, addrs); bpf_jit_build_epilogue(code_base, &cgctx); if (bpf_jit_enable > 1) pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass, proglen - (cgctx.idx * 4), cgctx.seen); } if (bpf_jit_enable > 1) /* Note that we output the base address of the code_base * rather than image, since opcodes are in code_base. */ bpf_jit_dump(flen, proglen, pass, code_base); if (image) { bpf_flush_icache(code_base, code_base + (proglen/4)); /* Function descriptor nastiness: Address + TOC */ ((u64 *)image)[0] = (u64)code_base; ((u64 *)image)[1] = local_paca->kernel_toc; fp->bpf_func = (void *)image; } out: kfree(addrs); return; } void bpf_jit_free(struct sk_filter *fp) { if (fp->bpf_func != sk_run_filter) module_free(NULL, fp->bpf_func); kfree(fp); }