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 /* Map all width-sensitive operations */ 63 #if __BITS_PER_LONG == 32 64 65 #define JEQ(x, jt) JEQ32(x, EXPAND(jt)) 66 #define JNE(x, jt) JNE32(x, EXPAND(jt)) 67 #define JGT(x, jt) JGT32(x, EXPAND(jt)) 68 #define JLT(x, jt) JLT32(x, EXPAND(jt)) 69 #define JGE(x, jt) JGE32(x, EXPAND(jt)) 70 #define JLE(x, jt) JLE32(x, EXPAND(jt)) 71 #define JA(x, jt) JA32(x, EXPAND(jt)) 72 #define ARG(i) ARG_32(i) 73 #define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) 74 75 #elif __BITS_PER_LONG == 64 76 77 /* Ensure that we load the logically correct offset. */ 78 #if __BYTE_ORDER == __LITTLE_ENDIAN 79 #define ENDIAN(_lo, _hi) _lo, _hi 80 #define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) 81 #define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32) 82 #elif __BYTE_ORDER == __BIG_ENDIAN 83 #define ENDIAN(_lo, _hi) _hi, _lo 84 #define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32) 85 #define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) 86 #else 87 #error "Unknown endianness" 88 #endif 89 90 union arg64 { 91 struct { 92 __u32 ENDIAN(lo32, hi32); 93 }; 94 __u64 u64; 95 }; 96 97 #define JEQ(x, jt) \ 98 JEQ64(((union arg64){.u64 = (x)}).lo32, \ 99 ((union arg64){.u64 = (x)}).hi32, \ 100 EXPAND(jt)) 101 #define JGT(x, jt) \ 102 JGT64(((union arg64){.u64 = (x)}).lo32, \ 103 ((union arg64){.u64 = (x)}).hi32, \ 104 EXPAND(jt)) 105 #define JGE(x, jt) \ 106 JGE64(((union arg64){.u64 = (x)}).lo32, \ 107 ((union arg64){.u64 = (x)}).hi32, \ 108 EXPAND(jt)) 109 #define JNE(x, jt) \ 110 JNE64(((union arg64){.u64 = (x)}).lo32, \ 111 ((union arg64){.u64 = (x)}).hi32, \ 112 EXPAND(jt)) 113 #define JLT(x, jt) \ 114 JLT64(((union arg64){.u64 = (x)}).lo32, \ 115 ((union arg64){.u64 = (x)}).hi32, \ 116 EXPAND(jt)) 117 #define JLE(x, jt) \ 118 JLE64(((union arg64){.u64 = (x)}).lo32, \ 119 ((union arg64){.u64 = (x)}).hi32, \ 120 EXPAND(jt)) 121 122 #define JA(x, jt) \ 123 JA64(((union arg64){.u64 = (x)}).lo32, \ 124 ((union arg64){.u64 = (x)}).hi32, \ 125 EXPAND(jt)) 126 #define ARG(i) ARG_64(i) 127 128 #else 129 #error __BITS_PER_LONG value unusable. 130 #endif 131 132 /* Loads the arg into A */ 133 #define ARG_32(idx) \ 134 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)) 135 136 /* Loads hi into A and lo in X */ 137 #define ARG_64(idx) \ 138 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)), \ 139 BPF_STMT(BPF_ST, 0), /* lo -> M[0] */ \ 140 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, HI_ARG(idx)), \ 141 BPF_STMT(BPF_ST, 1) /* hi -> M[1] */ 142 143 #define JEQ32(value, jt) \ 144 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 0, 1), \ 145 jt 146 147 #define JNE32(value, jt) \ 148 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 1, 0), \ 149 jt 150 151 /* Checks the lo, then swaps to check the hi. A=lo,X=hi */ 152 #define JEQ64(lo, hi, jt) \ 153 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 154 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 155 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \ 156 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 157 jt, \ 158 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 159 160 #define JNE64(lo, hi, jt) \ 161 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 5, 0), \ 162 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 163 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \ 164 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 165 jt, \ 166 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 167 168 #define JA32(value, jt) \ 169 BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \ 170 jt 171 172 #define JA64(lo, hi, jt) \ 173 BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \ 174 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 175 BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \ 176 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 177 jt, \ 178 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 179 180 #define JGE32(value, jt) \ 181 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \ 182 jt 183 184 #define JLT32(value, jt) \ 185 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \ 186 jt 187 188 /* Shortcut checking if hi > arg.hi. */ 189 #define JGE64(lo, hi, jt) \ 190 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \ 191 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 192 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 193 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \ 194 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 195 jt, \ 196 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 197 198 #define JLT64(lo, hi, jt) \ 199 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \ 200 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 201 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 202 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \ 203 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 204 jt, \ 205 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 206 207 #define JGT32(value, jt) \ 208 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \ 209 jt 210 211 #define JLE32(value, jt) \ 212 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \ 213 jt 214 215 /* Check hi > args.hi first, then do the GE checking */ 216 #define JGT64(lo, hi, jt) \ 217 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \ 218 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 219 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 220 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \ 221 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 222 jt, \ 223 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 224 225 #define JLE64(lo, hi, jt) \ 226 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 6, 0), \ 227 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \ 228 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 229 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \ 230 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ 231 jt, \ 232 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ 233 234 #define LOAD_SYSCALL_NR \ 235 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \ 236 offsetof(struct seccomp_data, nr)) 237 238 #endif /* __BPF_HELPER_H__ */ 239