diff options
Diffstat (limited to 'arch/powerpc/net/bpf_jit_comp.c')
| -rw-r--r-- | arch/powerpc/net/bpf_jit_comp.c | 694 |
1 files changed, 694 insertions, 0 deletions
diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c new file mode 100644 index 000000000000..73619d3aeb6c --- /dev/null +++ b/arch/powerpc/net/bpf_jit_comp.c @@ -0,0 +1,694 @@ +/* bpf_jit_comp.c: BPF JIT compiler for PPC64 + * + * Copyright 2011 Matt Evans <matt@ozlabs.org>, 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 <linux/moduleloader.h> +#include <asm/cacheflush.h> +#include <linux/netdevice.h> +#include <linux/filter.h> +#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(0)); + 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(1) | __PPC_RA(1) | + (-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_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(); +} + +/* 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 = reciprocal_divide(A, K); */ + PPC_LI32(r_scratch1, K); + /* Top 32 bits of 64bit result -> A */ + PPC_MULHWU(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_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_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 = sk_load_word; + goto common_load; + case BPF_S_LD_H_ABS: + func = sk_load_half; + goto common_load; + case BPF_S_LD_B_ABS: + func = sk_load_byte; + common_load: + /* + * Load from [K]. Reference with the (negative) + * SKF_NET_OFF/SKF_LL_OFF offsets is unsupported. + */ + ctx->seen |= SEEN_DATAREF; + if ((int)K < 0) + return -ENOTSUPP; + 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, and result in a 'ret 0'. + */ + 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: + /* + * x86 version drops packet (RET 0) when K<0, whereas + * interpreter does allow K<0 (__load_pointer, special + * ancillary data). common_load returns ENOTSUPP if K<0, + * so we fall back to interpreter & filter works. + */ + func = 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(max_t(unsigned int, alloclen, + sizeof(struct work_struct))); + 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) + pr_info("flen=%d proglen=%u pass=%d image=%p\n", + flen, proglen, pass, image); + + if (image) { + if (bpf_jit_enable > 1) + print_hex_dump(KERN_ERR, "JIT code: ", + DUMP_PREFIX_ADDRESS, + 16, 1, code_base, + proglen, false); + + 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; +} + +static void jit_free_defer(struct work_struct *arg) +{ + module_free(NULL, arg); +} + +/* run from softirq, we must use a work_struct to call + * module_free() from process context + */ +void bpf_jit_free(struct sk_filter *fp) +{ + if (fp->bpf_func != sk_run_filter) { + struct work_struct *work = (struct work_struct *)fp->bpf_func; + + INIT_WORK(work, jit_free_defer); + schedule_work(work); + } +} |