Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 1 | /* Copyright (c) 2012 The Chromium OS Authors. All rights reserved. |
| 2 | * Use of this source code is governed by a BSD-style license that can be |
| 3 | * found in the LICENSE file. |
| 4 | */ |
| 5 | |
| 6 | #include <stdint.h> |
| 7 | #include <stdio.h> |
| 8 | #include <stdlib.h> |
| 9 | #include <string.h> |
| 10 | |
| 11 | #include "bpf.h" |
| 12 | |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 13 | /* Architecture validation. */ |
| 14 | size_t bpf_validate_arch(struct sock_filter *filter) |
| 15 | { |
| 16 | struct sock_filter *curr_block = filter; |
| 17 | set_bpf_stmt(curr_block++, BPF_LD+BPF_W+BPF_ABS, arch_nr); |
| 18 | set_bpf_jump(curr_block++, |
| 19 | BPF_JMP+BPF_JEQ+BPF_K, ARCH_NR, SKIP, NEXT); |
| 20 | set_bpf_ret_kill(curr_block++); |
| 21 | return curr_block - filter; |
| 22 | } |
| 23 | |
| 24 | /* Syscall number eval functions. */ |
| 25 | size_t bpf_allow_syscall(struct sock_filter *filter, int nr) |
| 26 | { |
| 27 | struct sock_filter *curr_block = filter; |
| 28 | set_bpf_jump(curr_block++, BPF_JMP+BPF_JEQ+BPF_K, nr, NEXT, SKIP); |
| 29 | set_bpf_stmt(curr_block++, BPF_RET+BPF_K, SECCOMP_RET_ALLOW); |
| 30 | return curr_block - filter; |
| 31 | } |
| 32 | |
| 33 | size_t bpf_allow_syscall_args(struct sock_filter *filter, |
| 34 | int nr, unsigned int id) |
| 35 | { |
| 36 | struct sock_filter *curr_block = filter; |
| 37 | set_bpf_jump(curr_block++, BPF_JMP+BPF_JEQ+BPF_K, nr, NEXT, SKIP); |
| 38 | set_bpf_jump_lbl(curr_block++, id); |
| 39 | return curr_block - filter; |
| 40 | } |
| 41 | |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 42 | /* Size-aware arg loaders. */ |
| 43 | #if defined(BITS32) |
| 44 | size_t bpf_load_arg(struct sock_filter *filter, int argidx) |
| 45 | { |
| 46 | set_bpf_stmt(filter, BPF_LD+BPF_W+BPF_ABS, LO_ARG(argidx)); |
| 47 | return 1U; |
| 48 | } |
| 49 | #elif defined(BITS64) |
| 50 | size_t bpf_load_arg(struct sock_filter *filter, int argidx) |
| 51 | { |
| 52 | struct sock_filter *curr_block = filter; |
| 53 | set_bpf_stmt(curr_block++, BPF_LD+BPF_W+BPF_ABS, LO_ARG(argidx)); |
| 54 | set_bpf_stmt(curr_block++, BPF_ST, 0); /* lo -> M[0] */ |
| 55 | set_bpf_stmt(curr_block++, BPF_LD+BPF_W+BPF_ABS, HI_ARG(argidx)); |
| 56 | set_bpf_stmt(curr_block++, BPF_ST, 1); /* hi -> M[1] */ |
| 57 | return curr_block - filter; |
| 58 | } |
| 59 | #endif |
| 60 | |
Jorge Lucangeli Obes | ffec891 | 2012-11-30 14:46:23 -0800 | [diff] [blame] | 61 | /* Size-aware equality comparison. */ |
Jorge Lucangeli Obes | edb1d8e | 2012-04-26 10:05:09 -0700 | [diff] [blame] | 62 | size_t bpf_comp_jeq32(struct sock_filter *filter, unsigned long c, |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 63 | unsigned char jt, unsigned char jf) |
| 64 | { |
Jorge Lucangeli Obes | edb1d8e | 2012-04-26 10:05:09 -0700 | [diff] [blame] | 65 | unsigned int lo = (unsigned int)(c & 0xFFFFFFFF); |
| 66 | set_bpf_jump(filter, BPF_JMP+BPF_JEQ+BPF_K, lo, jt, jf); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 67 | return 1U; |
| 68 | } |
| 69 | |
Jorge Lucangeli Obes | ffec891 | 2012-11-30 14:46:23 -0800 | [diff] [blame] | 70 | /* |
| 71 | * On 64 bits, we have to do two 32-bit comparisons. |
| 72 | * We jump true when *both* comparisons are true. |
| 73 | */ |
Jorge Lucangeli Obes | 8a56ec2 | 2013-02-04 10:03:43 -0800 | [diff] [blame] | 74 | #if defined(BITS64) |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 75 | size_t bpf_comp_jeq64(struct sock_filter *filter, uint64_t c, |
| 76 | unsigned char jt, unsigned char jf) |
| 77 | { |
| 78 | unsigned int lo = (unsigned int)(c & 0xFFFFFFFF); |
| 79 | unsigned int hi = (unsigned int)(c >> 32); |
| 80 | |
| 81 | struct sock_filter *curr_block = filter; |
| 82 | |
| 83 | /* bpf_load_arg leaves |hi| in A */ |
| 84 | curr_block += bpf_comp_jeq32(curr_block, hi, NEXT, SKIPN(2) + jf); |
Jorge Lucangeli Obes | ffec891 | 2012-11-30 14:46:23 -0800 | [diff] [blame] | 85 | set_bpf_stmt(curr_block++, BPF_LD+BPF_MEM, 0); /* swap in |lo| */ |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 86 | curr_block += bpf_comp_jeq32(curr_block, lo, jt, jf); |
| 87 | |
| 88 | return curr_block - filter; |
| 89 | } |
Jorge Lucangeli Obes | 8a56ec2 | 2013-02-04 10:03:43 -0800 | [diff] [blame] | 90 | #endif |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 91 | |
Jorge Lucangeli Obes | ffec891 | 2012-11-30 14:46:23 -0800 | [diff] [blame] | 92 | /* Size-aware bitwise AND. */ |
| 93 | size_t bpf_comp_jset32(struct sock_filter *filter, unsigned long mask, |
| 94 | unsigned char jt, unsigned char jf) |
| 95 | { |
| 96 | unsigned int mask_lo = (unsigned int)(mask & 0xFFFFFFFF); |
| 97 | set_bpf_jump(filter, BPF_JMP+BPF_JSET+BPF_K, mask_lo, jt, jf); |
| 98 | return 1U; |
| 99 | } |
| 100 | |
| 101 | /* |
| 102 | * On 64 bits, we have to do two 32-bit bitwise ANDs. |
| 103 | * We jump true when *either* bitwise AND is true (non-zero). |
| 104 | */ |
Jorge Lucangeli Obes | 8a56ec2 | 2013-02-04 10:03:43 -0800 | [diff] [blame] | 105 | #if defined(BITS64) |
Jorge Lucangeli Obes | ffec891 | 2012-11-30 14:46:23 -0800 | [diff] [blame] | 106 | size_t bpf_comp_jset64(struct sock_filter *filter, uint64_t mask, |
| 107 | unsigned char jt, unsigned char jf) |
| 108 | { |
| 109 | unsigned int mask_lo = (unsigned int)(mask & 0xFFFFFFFF); |
| 110 | unsigned int mask_hi = (unsigned int)(mask >> 32); |
| 111 | |
| 112 | struct sock_filter *curr_block = filter; |
| 113 | |
| 114 | /* bpf_load_arg leaves |hi| in A */ |
| 115 | curr_block += bpf_comp_jset32(curr_block, mask_hi, SKIPN(2) + jt, NEXT); |
| 116 | set_bpf_stmt(curr_block++, BPF_LD+BPF_MEM, 0); /* swap in |lo| */ |
| 117 | curr_block += bpf_comp_jset32(curr_block, mask_lo, jt, jf); |
| 118 | |
| 119 | return curr_block - filter; |
| 120 | } |
Jorge Lucangeli Obes | 8a56ec2 | 2013-02-04 10:03:43 -0800 | [diff] [blame] | 121 | #endif |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 122 | |
| 123 | size_t bpf_arg_comp(struct sock_filter **pfilter, |
| 124 | int op, int argidx, unsigned long c, unsigned int label_id) |
| 125 | { |
| 126 | struct sock_filter *filter = calloc(BPF_ARG_COMP_LEN + 1, |
| 127 | sizeof(struct sock_filter)); |
| 128 | struct sock_filter *curr_block = filter; |
Jorge Lucangeli Obes | ffec891 | 2012-11-30 14:46:23 -0800 | [diff] [blame] | 129 | size_t (*comp_function)(struct sock_filter *filter, unsigned long k, |
| 130 | unsigned char jt, unsigned char jf); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 131 | int flip = 0; |
| 132 | |
| 133 | /* Load arg */ |
| 134 | curr_block += bpf_load_arg(curr_block, argidx); |
| 135 | |
| 136 | /* Jump type */ |
| 137 | switch (op) { |
| 138 | case EQ: |
Jorge Lucangeli Obes | ffec891 | 2012-11-30 14:46:23 -0800 | [diff] [blame] | 139 | comp_function = bpf_comp_jeq; |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 140 | flip = 0; |
| 141 | break; |
| 142 | case NE: |
Jorge Lucangeli Obes | ffec891 | 2012-11-30 14:46:23 -0800 | [diff] [blame] | 143 | comp_function = bpf_comp_jeq; |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 144 | flip = 1; |
| 145 | break; |
Jorge Lucangeli Obes | ffec891 | 2012-11-30 14:46:23 -0800 | [diff] [blame] | 146 | case SET: |
| 147 | comp_function = bpf_comp_jset; |
| 148 | flip = 0; |
| 149 | break; |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 150 | default: |
| 151 | *pfilter = NULL; |
| 152 | return 0; |
| 153 | } |
| 154 | |
| 155 | /* |
| 156 | * It's easier for the rest of the code to have the true branch |
| 157 | * skip and the false branch fall through. |
| 158 | */ |
| 159 | unsigned char jt = flip ? NEXT : SKIP; |
| 160 | unsigned char jf = flip ? SKIP : NEXT; |
Jorge Lucangeli Obes | ffec891 | 2012-11-30 14:46:23 -0800 | [diff] [blame] | 161 | curr_block += comp_function(curr_block, c, jt, jf); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 162 | curr_block += set_bpf_jump_lbl(curr_block, label_id); |
| 163 | |
| 164 | *pfilter = filter; |
| 165 | return curr_block - filter; |
| 166 | } |
| 167 | |
| 168 | void dump_bpf_filter(struct sock_filter *filter, unsigned short len) |
| 169 | { |
| 170 | int i = 0; |
| 171 | |
| 172 | printf("len == %d\n", len); |
| 173 | printf("filter:\n"); |
| 174 | for (i = 0; i < len; i++) { |
Jorge Lucangeli Obes | f16d6d1 | 2016-09-29 20:25:27 -0400 | [diff] [blame] | 175 | printf("%d: \t{ code=%#x, jt=%u, jf=%u, k=%#x \t}\n", i, |
| 176 | filter[i].code, filter[i].jt, filter[i].jf, filter[i].k); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 177 | } |
| 178 | } |
| 179 | |
| 180 | void dump_bpf_prog(struct sock_fprog *fprog) |
| 181 | { |
| 182 | struct sock_filter *filter = fprog->filter; |
| 183 | unsigned short len = fprog->len; |
| 184 | dump_bpf_filter(filter, len); |
| 185 | } |
| 186 | |
Jorge Lucangeli Obes | f16d6d1 | 2016-09-29 20:25:27 -0400 | [diff] [blame] | 187 | int bpf_resolve_jumps(struct bpf_labels *labels, struct sock_filter *filter, |
| 188 | size_t len) |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 189 | { |
Jorge Lucangeli Obes | f16d6d1 | 2016-09-29 20:25:27 -0400 | [diff] [blame] | 190 | size_t insn; |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 191 | struct sock_filter *begin = filter; |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 192 | |
Jorge Lucangeli Obes | f16d6d1 | 2016-09-29 20:25:27 -0400 | [diff] [blame] | 193 | /* This needs at least two instructions: one jump and one label. */ |
| 194 | if (len < 2) |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 195 | return -1; |
Jorge Lucangeli Obes | f16d6d1 | 2016-09-29 20:25:27 -0400 | [diff] [blame] | 196 | |
| 197 | if (len > BPF_MAXINSNS) |
| 198 | return -1; |
| 199 | |
| 200 | insn = len - 1; |
| 201 | |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 202 | /* |
| 203 | * Walk it once, backwards, to build the label table and do fixups. |
| 204 | * Since backward jumps are disallowed by BPF, this is easy. |
| 205 | */ |
| 206 | for (filter += insn; filter >= begin; --insn, --filter) { |
Jorge Lucangeli Obes | f16d6d1 | 2016-09-29 20:25:27 -0400 | [diff] [blame] | 207 | if (filter->code != (BPF_JMP + BPF_JA)) |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 208 | continue; |
Jorge Lucangeli Obes | f16d6d1 | 2016-09-29 20:25:27 -0400 | [diff] [blame] | 209 | switch ((filter->jt << 8) | filter->jf) { |
| 210 | case (JUMP_JT << 8) | JUMP_JF: |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 211 | if (labels->labels[filter->k].location == 0xffffffff) { |
| 212 | fprintf(stderr, "Unresolved label: '%s'\n", |
| 213 | labels->labels[filter->k].label); |
| 214 | return 1; |
| 215 | } |
Jorge Lucangeli Obes | f16d6d1 | 2016-09-29 20:25:27 -0400 | [diff] [blame] | 216 | filter->k = |
| 217 | labels->labels[filter->k].location - (insn + 1); |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 218 | filter->jt = 0; |
| 219 | filter->jf = 0; |
| 220 | continue; |
Jorge Lucangeli Obes | f16d6d1 | 2016-09-29 20:25:27 -0400 | [diff] [blame] | 221 | case (LABEL_JT << 8) | LABEL_JF: |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 222 | if (labels->labels[filter->k].location != 0xffffffff) { |
| 223 | fprintf(stderr, "Duplicate label use: '%s'\n", |
| 224 | labels->labels[filter->k].label); |
| 225 | return 1; |
| 226 | } |
| 227 | labels->labels[filter->k].location = insn; |
Jorge Lucangeli Obes | f16d6d1 | 2016-09-29 20:25:27 -0400 | [diff] [blame] | 228 | filter->k = 0; /* Fall through. */ |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 229 | filter->jt = 0; |
| 230 | filter->jf = 0; |
| 231 | continue; |
| 232 | } |
| 233 | } |
| 234 | return 0; |
| 235 | } |
| 236 | |
| 237 | /* Simple lookup table for labels. */ |
| 238 | int bpf_label_id(struct bpf_labels *labels, const char *label) |
| 239 | { |
| 240 | struct __bpf_label *begin = labels->labels, *end; |
| 241 | int id; |
| 242 | if (labels->count == 0) { |
| 243 | begin->label = strndup(label, MAX_BPF_LABEL_LEN); |
| 244 | if (!begin->label) { |
| 245 | return -1; |
| 246 | } |
| 247 | begin->location = 0xffffffff; |
| 248 | labels->count++; |
| 249 | return 0; |
| 250 | } |
| 251 | end = begin + labels->count; |
| 252 | for (id = 0; begin < end; ++begin, ++id) { |
| 253 | if (!strcmp(label, begin->label)) |
| 254 | return id; |
| 255 | } |
Jorge Lucangeli Obes | f16d6d1 | 2016-09-29 20:25:27 -0400 | [diff] [blame] | 256 | |
| 257 | /* The label wasn't found. Insert it only if there's space. */ |
| 258 | if (labels->count == BPF_LABELS_MAX) { |
| 259 | return -1; |
| 260 | } |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 261 | begin->label = strndup(label, MAX_BPF_LABEL_LEN); |
| 262 | if (!begin->label) { |
| 263 | return -1; |
| 264 | } |
| 265 | begin->location = 0xffffffff; |
| 266 | labels->count++; |
| 267 | return id; |
| 268 | } |
| 269 | |
| 270 | /* Free label strings. */ |
| 271 | void free_label_strings(struct bpf_labels *labels) |
| 272 | { |
Jorge Lucangeli Obes | d446726 | 2012-03-23 16:19:59 -0700 | [diff] [blame] | 273 | if (labels->count == 0) |
| 274 | return; |
| 275 | |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 276 | struct __bpf_label *begin = labels->labels, *end; |
| 277 | |
| 278 | end = begin + labels->count; |
| 279 | for (; begin < end; ++begin) { |
| 280 | if (begin->label) |
| 281 | free((void*)(begin->label)); |
| 282 | } |
Jorge Lucangeli Obes | a67bd6a | 2016-08-19 15:33:48 -0400 | [diff] [blame] | 283 | |
| 284 | labels->count = 0; |
Jorge Lucangeli Obes | fc8ab53 | 2012-03-20 10:14:31 -0700 | [diff] [blame] | 285 | } |