1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Example wrapper around BPF macros. 4 * 5 * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org> 6 * Author: Will Drewry <wad@chromium.org> 7 * 8 * The code may be used by anyone for any purpose, 9 * and can serve as a starting point for developing 10 * applications using prctl(PR_SET_SECCOMP, 2, ...). 11 * 12 * No guarantees are provided with respect to the correctness 13 * or functionality of this code. 14 */ 15 #ifndef __BPF_HELPER_H__ 16 #define __BPF_HELPER_H__ 17 18 #include <asm/bitsperlong.h> /* for __BITS_PER_LONG */ 19 #include <endian.h> 20 #include <linux/filter.h> 21 #include <linux/seccomp.h> /* for seccomp_data */ 22 #include <linux/types.h> 23 #include <linux/unistd.h> 24 #include <stddef.h> 25 26 #define BPF_LABELS_MAX 256 27 struct bpf_labels { 28 int count; 29 struct __bpf_label { 30 const char *label; 31 __u32 location; 32 } labels[BPF_LABELS_MAX]; 33 }; 34 35 int bpf_resolve_jumps(struct bpf_labels *labels, 36 struct sock_filter *filter, size_t count); 37 __u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label); 38 void seccomp_bpf_print(struct sock_filter *filter, size_t count); 39 40 #define JUMP_JT 0xff 41 #define JUMP_JF 0xff 42 #define LABEL_JT 0xfe 43 #define LABEL_JF 0xfe 44 45 #define ALLOW \ 46 BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW) 47 #define DENY \ 48 BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL) 49 #define JUMP(labels, label) \ 50 BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \ 51 JUMP_JT, JUMP_JF) 52 #define LABEL(labels, label) \ 53 BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \ 54 LABEL_JT, LABEL_JF) 55 #define SYSCALL(nr, jt) \ 56 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (nr), 0, 1), \ 57 jt 58 59 /* Lame, but just an example */ 60 #define FIND_LABEL(labels, label) seccomp_bpf_label((labels), #label) 61 62 #define EXPAND(...) __VA_ARGS__ 63 64 /* Ensure that we load the logically correct offset. */ 65 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ 66 #define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) 67 #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ 68 #define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32) 69 #else 70 #error "Unknown endianness" 71 #endif 72 73 /* Map all width-sensitive operations */ 74 #if __BITS_PER_LONG == 32 75 76 #define JEQ(x, jt) JEQ32(x, EXPAND(jt)) 77 #define JNE(x, jt) JNE32(x, EXPAND(jt)) 78 #define JGT(x, jt) JGT32(x, EXPAND(jt)) 79 #define JLT(x, jt) JLT32(x, EXPAND(jt)) 80 #define JGE(x, jt) JGE32(x, EXPAND(jt)) 81 #define JLE(x, jt) JLE32(x, EXPAND(jt)) 82 #define JA(x, jt) JA32(x, EXPAND(jt)) 83 #define ARG(i) ARG_32(i) 84 85 #elif __BITS_PER_LONG == 64 86 87 /* Ensure that we load the logically correct offset. */ 88 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ 89 #define ENDIAN(_lo, _hi) _lo, _hi 90 #define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32) 91 #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ 92 #define ENDIAN(_lo, _hi) _hi, _lo 93 #define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) 94 #endif 95 96 union arg64 { 97 struct { 98 __u32 ENDIAN(lo32, hi32); 99 }; 100 __u64 u64; 101 }; 102 103 #define JEQ(x, jt) \ 104 JEQ64(((union arg64){.u64 = (x)}).lo32, \ 105 ((union arg64){.u64 = (x)}).hi32, \ 106 EXPAND(jt)) 107 #define JGT(x, jt) \ 108 JGT64(((union arg64){.u64 = (x)}).lo32, \ 109 ((union arg64){.u64 = (x)}).hi32, \ 110 EXPAND(jt)) 111 #define JGE(x, jt) \ 112 JGE64(((union arg64){.u64 = (x)}).lo32, \ 113 ((union arg64){.u64 = (x)}).hi32, \ 114 EXPAND(jt)) 115 #define JNE(x, jt) \ 116 JNE64(((union arg64){.u64 = (x)}).lo32, \ 117 ((union arg64){.u64 = (x)}).hi32, \ 118 EXPAND(jt)) 119 #define JLT(x, jt) \ 120 JLT64(((union arg64){.u64 = (x)}).lo32, \ 121 ((union arg64){.u64 = (x)}).hi32, \ 122 EXPAND(jt)) 123 #define JLE(x, jt) \ 124 JLE64(((union arg64){.u64 = (x)}).lo32, \ 125 ((union arg64){.u64 = (x)}).hi32, \ 126 EXPAND(jt)) 127 128 #define JA(x, jt) \ 129 JA64(((union arg64){.u64 = (x)}).lo32, \ 130 ((union arg64){.u64 = (x)}).hi32, \ 131 EXPAND(jt)) 132 #define ARG(i) ARG_64(i) 133 134 #else 135 #error __BITS_PER_LONG value unusable. 136 #endif 137 138 /* Loads the arg into A */ 139 #define ARG_32(idx) \ 140 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)) 141 142 /* Loads lo into M[0] and hi into M[1] and A */ 143 #define ARG_64(idx) \ 144 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)), \ 145 BPF_STMT(BPF_ST, 0), /* lo -> M[0] */ \ 146 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, HI_ARG(idx)), \ 147 BPF_STMT(BPF_ST, 1) /* hi -> M[1] */ 148 149 #define JEQ32(value, jt) \ 150 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 0, 1), \ 151 jt 152 153 #define JNE32(value, jt) \ 154 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 1, 0), \ 155 jt 156 157 #define JA32(value, jt) \ 158 BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \ 159 jt 160 161 #define JGE32(value, jt) \ 162 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \ 163 jt 164 165 #define JGT32(value, jt) \ 166 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \ 167 jt 168 169 #define JLE32(value, jt) \ 170 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \ 171 jt 172 173 #define JLT32(value, jt) \ 174 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \ 175 jt 176 177 /* 178 * All the JXX64 checks assume lo is saved in M[0] and hi is saved in both 179 * A and M[1]. This invariant is kept by restoring A if necessary. 180 */ 181 #define JEQ64(lo, hi, jt) \ 182 /* if (hi != arg.hi) goto NOMATCH; */ \ 183 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 184 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ 185 /* if (lo != arg.lo) goto NOMATCH; */ \ 186 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \ 187 BPF_STMT(BPF_LD+BPF_MEM, 1), \ 188 jt, \ 189 BPF_STMT(BPF_LD+BPF_MEM, 1) 190 191 #define JNE64(lo, hi, jt) \ 192 /* if (hi != arg.hi) goto MATCH; */ \ 193 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \ 194 BPF_STMT(BPF_LD+BPF_MEM, 0), \ 195 /* if (lo != arg.lo) goto MATCH; */ \ 196 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \ 197 BPF_STMT(BPF_LD+BPF_MEM, 1), \ 198 jt, \ 199 BPF_STMT(BPF_LD+BPF_MEM, 1) 200 201 #define JA64(lo, hi, jt) \ 202 /* if (hi & arg.hi) goto MATCH; */ \ 203 BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \ 204 BPF_STMT(BPF_LD+BPF_MEM, 0), \ 205 /* if (lo & arg.lo) goto MATCH; */ \ 206 BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \ 207 BPF_STMT(BPF_LD+BPF_MEM, 1), \ 208 jt, \ 209 BPF_STMT(BPF_LD+BPF_MEM, 1) 210 211 #define JGE64(lo, hi, jt) \ 212 /* if (hi > arg.hi) goto MATCH; */ \ 213 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \ 214 /* if (hi != arg.hi) goto NOMATCH; */ \ 215 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 216 BPF_STMT(BPF_LD+BPF_MEM, 0), \ 217 /* if (lo >= arg.lo) goto MATCH; */ \ 218 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \ 219 BPF_STMT(BPF_LD+BPF_MEM, 1), \ 220 jt, \ 221 BPF_STMT(BPF_LD+BPF_MEM, 1) 222 223 #define JGT64(lo, hi, jt) \ 224 /* if (hi > arg.hi) goto MATCH; */ \ 225 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \ 226 /* if (hi != arg.hi) goto NOMATCH; */ \ 227 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 228 BPF_STMT(BPF_LD+BPF_MEM, 0), \ 229 /* if (lo > arg.lo) goto MATCH; */ \ 230 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \ 231 BPF_STMT(BPF_LD+BPF_MEM, 1), \ 232 jt, \ 233 BPF_STMT(BPF_LD+BPF_MEM, 1) 234 235 #define JLE64(lo, hi, jt) \ 236 /* if (hi < arg.hi) goto MATCH; */ \ 237 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \ 238 /* if (hi != arg.hi) goto NOMATCH; */ \ 239 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 240 BPF_STMT(BPF_LD+BPF_MEM, 0), \ 241 /* if (lo <= arg.lo) goto MATCH; */ \ 242 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \ 243 BPF_STMT(BPF_LD+BPF_MEM, 1), \ 244 jt, \ 245 BPF_STMT(BPF_LD+BPF_MEM, 1) 246 247 #define JLT64(lo, hi, jt) \ 248 /* if (hi < arg.hi) goto MATCH; */ \ 249 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \ 250 /* if (hi != arg.hi) goto NOMATCH; */ \ 251 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ 252 BPF_STMT(BPF_LD+BPF_MEM, 0), \ 253 /* if (lo < arg.lo) goto MATCH; */ \ 254 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 2, 0), \ 255 BPF_STMT(BPF_LD+BPF_MEM, 1), \ 256 jt, \ 257 BPF_STMT(BPF_LD+BPF_MEM, 1) 258 259 #define LOAD_SYSCALL_NR \ 260 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \ 261 offsetof(struct seccomp_data, nr)) 262 263 #endif /* __BPF_HELPER_H__ */ 264