1 /* 2 * Example wrapper around BPF macros. 3 * 4 * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org> 5 * Author: Will Drewry <wad@chromium.org> 6 * 7 * The code may be used by anyone for any purpose, 8 * and can serve as a starting point for developing 9 * applications using prctl(PR_SET_SECCOMP, 2, ...). 10 * 11 * No guarantees are provided with respect to the correctness 12 * or functionality of this code. 13 */ 14 #ifndef __BPF_HELPER_H__ 15 #define __BPF_HELPER_H__ 16 17 #include <asm/bitsperlong.h> /* for __BITS_PER_LONG */ 18 #include <endian.h> 19 #include <linux/filter.h> 20 #include <linux/seccomp.h> /* for seccomp_data */ 21 #include <linux/types.h> 22 #include <linux/unistd.h> 23 #include <stddef.h> 24 25 #define BPF_LABELS_MAX 256 26 struct bpf_labels { 27 int count; 28 struct __bpf_label { 29 const char *label; 30 __u32 location; 31 } labels[BPF_LABELS_MAX]; 32 }; 33 34 int bpf_resolve_jumps(struct bpf_labels *labels, 35 struct sock_filter *filter, size_t count); 36 __u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label); 37 void seccomp_bpf_print(struct sock_filter *filter, size_t count); 38 39 #define JUMP_JT 0xff 40 #define JUMP_JF 0xff 41 #define LABEL_JT 0xfe 42 #define LABEL_JF 0xfe 43 44 #define ALLOW \ 45 BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW) 46 #define DENY \ 47 BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL) 48 #define JUMP(labels, label) \ 49 BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \ 50 JUMP_JT, JUMP_JF) 51 #define LABEL(labels, label) \ 52 BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \ 53 LABEL_JT, LABEL_JF) 54 #define SYSCALL(nr, jt) \ 55 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (nr), 0, 1), \ 56 jt 57 58 /* Lame, but just an example */ 59 #define FIND_LABEL(labels, label) seccomp_bpf_label((labels), #label) 60 61 #define EXPAND(...) __VA_ARGS__ 62 63 /* Ensure that we load the logically correct offset. */ 64 #if __BYTE_ORDER == __LITTLE_ENDIAN 65 #define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) 66 #elif __BYTE_ORDER == __BIG_ENDIAN 67 #define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32) 68 #else 69 #error "Unknown endianness" 70 #endif 71 72 /* Map all width-sensitive operations */ 73 #if __BITS_PER_LONG == 32 74 75 #define JEQ(x, jt) JEQ32(x, EXPAND(jt)) 76 #define JNE(x, jt) JNE32(x, EXPAND(jt)) 77 #define JGT(x, jt) JGT32(x, EXPAND(jt)) 78 #define JLT(x, jt) JLT32(x, EXPAND(jt)) 79 #define JGE(x, jt) JGE32(x, EXPAND(jt)) 80 #define JLE(x, jt) JLE32(x, EXPAND(jt)) 81 #define JA(x, jt) JA32(x, EXPAND(jt)) 82 #define ARG(i) ARG_32(i) 83 84 #elif __BITS_PER_LONG == 64 85 86 /* Ensure that we load the logically correct offset. */ 87 #if __BYTE_ORDER == __LITTLE_ENDIAN 88 #define ENDIAN(_lo, _hi) _lo, _hi 89 #define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32) 90 #elif __BYTE_ORDER == __BIG_ENDIAN 91 #define ENDIAN(_lo, _hi) _hi, _lo 92 #define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) 93 #endif 94 95 union arg64 { 96 struct { 97 __u32 ENDIAN(lo32, hi32); 98 }; 99 __u64 u64; 100 }; 101 102 #define JEQ(x, jt) \ 103 JEQ64(((union arg64){.u64 = (x)}).lo32, \ 104 ((union arg64){.u64 = (x)}).hi32, \ 105 EXPAND(jt)) 106 #define JGT(x, jt) \ 107 JGT64(((union arg64){.u64 = (x)}).lo32, \ 108 ((union arg64){.u64 = (x)}).hi32, \ 109 EXPAND(jt)) 110 #define JGE(x, jt) \ 111 JGE64(((union arg64){.u64 = (x)}).lo32, \ 112 ((union arg64){.u64 = (x)}).hi32, \ 113 EXPAND(jt)) 114 #define JNE(x, jt) \ 115 JNE64(((union arg64){.u64 = (x)}).lo32, \ 116 ((union arg64){.u64 = (x)}).hi32, \ 117 EXPAND(jt)) 118 #define JLT(x, jt) \ 119 JLT64(((union arg64){.u64 = (x)}).lo32, \ 120 ((union arg64){.u64 = (x)}).hi32, \ 121 EXPAND(jt)) 122 #define JLE(x, jt) \ 123 JLE64(((union arg64){.u64 = (x)}).lo32, \ 124 ((union arg64){.u64 = (x)}).hi32, \ 125 EXPAND(jt)) 126 127 #define JA(x, jt) \ 128 JA64(((union arg64){.u64 = (x)}).lo32, \ 129 ((union arg64){.u64 = (x)}).hi32, \ 130 EXPAND(jt)) 131 #define ARG(i) ARG_64(i) 132 133 #else 134 #error __BITS_PER_LONG value unusable. 135 #endif 136 137 /* Loads the arg into A */ 138 #define ARG_32(idx) \ 139 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)) 140 141 /* Loads hi into A and lo in X */ 142 #define ARG_64(idx) \ 143 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)), \ 144 BPF_STMT(BPF_ST, 0), /* lo -> M[0] */ \ 145 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, HI_ARG(idx)), \ 146 BPF_STMT(BPF_ST, 1) /* hi -> M[1] */ 147 148 #define JEQ32(value, jt) \ 149 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 0, 1), \ 150 jt 151 152 #define JNE32(value, jt) \ 153 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 1, 0), \ 154 jt 155 156 /* Checks the lo, then swaps to check the hi. A=lo,X=hi */ 157 #define JEQ64(lo, hi, jt) \ 158 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 159 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 160 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \ 161 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 162 jt, \ 163 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 164 165 #define JNE64(lo, hi, jt) \ 166 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 5, 0), \ 167 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 168 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \ 169 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 170 jt, \ 171 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 172 173 #define JA32(value, jt) \ 174 BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \ 175 jt 176 177 #define JA64(lo, hi, jt) \ 178 BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \ 179 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 180 BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \ 181 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 182 jt, \ 183 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 184 185 #define JGE32(value, jt) \ 186 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \ 187 jt 188 189 #define JLT32(value, jt) \ 190 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \ 191 jt 192 193 /* Shortcut checking if hi > arg.hi. */ 194 #define JGE64(lo, hi, jt) \ 195 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \ 196 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 197 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 198 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \ 199 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 200 jt, \ 201 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 202 203 #define JLT64(lo, hi, jt) \ 204 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \ 205 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 206 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 207 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \ 208 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 209 jt, \ 210 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 211 212 #define JGT32(value, jt) \ 213 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \ 214 jt 215 216 #define JLE32(value, jt) \ 217 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \ 218 jt 219 220 /* Check hi > args.hi first, then do the GE checking */ 221 #define JGT64(lo, hi, jt) \ 222 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \ 223 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 224 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 225 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \ 226 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 227 jt, \ 228 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 229 230 #define JLE64(lo, hi, jt) \ 231 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 6, 0), \ 232 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \ 233 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 234 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \ 235 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 236 jt, \ 237 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 238 239 #define LOAD_SYSCALL_NR \ 240 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \ 241 offsetof(struct seccomp_data, nr)) 242 243 #endif /* __BPF_HELPER_H__ */ 244