1 /* bpf.h 2 * Copyright (c) 2012 The Chromium OS Authors. All rights reserved. 3 * Use of this source code is governed by a BSD-style license that can be 4 * found in the LICENSE file. 5 * 6 * Berkeley Packet Filter functions. 7 */ 8 9 #ifndef BPF_H 10 #define BPF_H 11 12 #include <asm/bitsperlong.h> /* for __BITS_PER_LONG */ 13 #include <endian.h> 14 #include <linux/audit.h> 15 #include <linux/filter.h> 16 #include <stddef.h> 17 #include <sys/user.h> 18 19 #ifdef __cplusplus 20 extern "C" { 21 #endif 22 23 #include "arch.h" 24 25 #if __BITS_PER_LONG == 32 || defined(__ILP32__) 26 #define BITS32 27 #elif __BITS_PER_LONG == 64 28 #define BITS64 29 #endif 30 31 /* Constants for comparison operators. */ 32 #define MIN_OPERATOR 128 33 enum { 34 EQ = MIN_OPERATOR, 35 NE, 36 LT, 37 LE, 38 GT, 39 GE, 40 SET, 41 IN 42 }; 43 44 /* 45 * BPF return values and data structures, 46 * since they're not yet in the kernel. 47 */ 48 #define SECCOMP_RET_KILL 0x00000000U /* kill the task immediately */ 49 #define SECCOMP_RET_TRAP 0x00030000U /* return SIGSYS */ 50 #define SECCOMP_RET_ERRNO 0x00050000U /* return -1 and set errno */ 51 #define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ 52 53 #define SECCOMP_RET_DATA 0x0000ffffU /* mask for return value */ 54 55 struct seccomp_data { 56 int nr; 57 __u32 arch; 58 __u64 instruction_pointer; 59 __u64 args[6]; 60 }; 61 62 #define syscall_nr (offsetof(struct seccomp_data, nr)) 63 #define arch_nr (offsetof(struct seccomp_data, arch)) 64 65 /* Size-dependent defines. */ 66 #if defined(BITS32) 67 /* 68 * On 32 bits, comparisons take 2 instructions: 1 for loading the argument, 69 * 1 for the actual comparison. 70 */ 71 #define BPF_LOAD_ARG_LEN 1U 72 #define BPF_COMP_LEN 1U 73 #define BPF_SHORT_GT_GE_COMP_LEN 1U 74 #define BPF_GT_GE_COMP_LEN 1U 75 #define BPF_ARG_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_COMP_LEN) 76 #define BPF_ARG_SHORT_GT_GE_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_SHORT_GT_GE_COMP_LEN) 77 #define BPF_ARG_GT_GE_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_GT_GE_COMP_LEN) 78 79 #define bpf_comp_jeq bpf_comp_jeq32 80 #define bpf_comp_jgt bpf_comp_jgt32 81 #define bpf_comp_jge bpf_comp_jge32 82 #define bpf_comp_jset bpf_comp_jset32 83 84 #define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) 85 86 #elif defined(BITS64) 87 /* 88 * On 64 bits, comparisons take 7-8 instructions: 4 for loading the argument, 89 * and 3-4 for the actual comparison. 90 */ 91 #define BPF_LOAD_ARG_LEN 4U 92 #define BPF_COMP_LEN 3U 93 #define BPF_SHORT_GT_GE_COMP_LEN 3U 94 #define BPF_GT_GE_COMP_LEN 4U 95 #define BPF_ARG_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_COMP_LEN) 96 #define BPF_ARG_SHORT_GT_GE_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_SHORT_GT_GE_COMP_LEN) 97 #define BPF_ARG_GT_GE_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_GT_GE_COMP_LEN) 98 99 #define bpf_comp_jeq bpf_comp_jeq64 100 #define bpf_comp_jgt bpf_comp_jgt64 101 #define bpf_comp_jge bpf_comp_jge64 102 #define bpf_comp_jset bpf_comp_jset64 103 104 /* Ensure that we load the logically correct offset. */ 105 #if defined(__LITTLE_ENDIAN__) || __BYTE_ORDER == __LITTLE_ENDIAN 106 #define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) 107 #define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32) 108 #else 109 #error "Unsupported endianness" 110 #endif 111 112 #else 113 #error "Unknown bit width" 114 115 #endif 116 117 /* Common jump targets. */ 118 #define NEXT 0 119 #define SKIP 1 120 #define SKIPN(_n) (_n) 121 122 /* Support for labels in BPF programs. */ 123 #define JUMP_JT 0xff 124 #define JUMP_JF 0xff 125 #define LABEL_JT 0xfe 126 #define LABEL_JF 0xfe 127 128 #define MAX_BPF_LABEL_LEN 32 129 130 #define BPF_LABELS_MAX 512U /* Each syscall could have an argument block. */ 131 struct bpf_labels { 132 size_t count; 133 struct __bpf_label { 134 const char *label; 135 unsigned int location; 136 } labels[BPF_LABELS_MAX]; 137 }; 138 139 /* BPF instruction manipulation functions and macros. */ 140 static inline size_t set_bpf_instr(struct sock_filter *instr, 141 unsigned short code, unsigned int k, 142 unsigned char jt, unsigned char jf) 143 { 144 instr->code = code; 145 instr->k = k; 146 instr->jt = jt; 147 instr->jf = jf; 148 return 1U; 149 } 150 151 #define set_bpf_stmt(_block, _code, _k) \ 152 set_bpf_instr((_block), (_code), (_k), 0, 0) 153 154 #define set_bpf_jump(_block, _code, _k, _jt, _jf) \ 155 set_bpf_instr((_block), (_code), (_k), (_jt), (_jf)) 156 157 #define set_bpf_lbl(_block, _lbl_id) \ 158 set_bpf_jump((_block), BPF_JMP+BPF_JA, (_lbl_id), \ 159 LABEL_JT, LABEL_JF) 160 161 #define set_bpf_jump_lbl(_block, _lbl_id) \ 162 set_bpf_jump((_block), BPF_JMP+BPF_JA, (_lbl_id), \ 163 JUMP_JT, JUMP_JF) 164 165 #define set_bpf_ret_kill(_block) \ 166 set_bpf_stmt((_block), BPF_RET+BPF_K, SECCOMP_RET_KILL) 167 168 #define set_bpf_ret_trap(_block) \ 169 set_bpf_stmt((_block), BPF_RET+BPF_K, SECCOMP_RET_TRAP) 170 171 #define set_bpf_ret_errno(_block, _errno) \ 172 set_bpf_stmt((_block), BPF_RET+BPF_K, \ 173 SECCOMP_RET_ERRNO | ((_errno) & SECCOMP_RET_DATA)) 174 175 #define set_bpf_ret_allow(_block) \ 176 set_bpf_stmt((_block), BPF_RET+BPF_K, SECCOMP_RET_ALLOW) 177 178 #define bpf_load_syscall_nr(_filter) \ 179 set_bpf_stmt((_filter), BPF_LD+BPF_W+BPF_ABS, syscall_nr) 180 181 /* BPF label functions. */ 182 int bpf_resolve_jumps(struct bpf_labels *labels, 183 struct sock_filter *filter, size_t count); 184 int bpf_label_id(struct bpf_labels *labels, const char *label); 185 void free_label_strings(struct bpf_labels *labels); 186 187 /* BPF helper functions. */ 188 size_t bpf_load_arg(struct sock_filter *filter, int argidx); 189 size_t bpf_comp_jeq(struct sock_filter *filter, unsigned long c, 190 unsigned char jt, unsigned char jf); 191 size_t bpf_comp_jgt(struct sock_filter *filter, unsigned long c, 192 unsigned char jt, unsigned char jf); 193 size_t bpf_comp_jge(struct sock_filter *filter, unsigned long c, 194 unsigned char jt, unsigned char jf); 195 size_t bpf_comp_jset(struct sock_filter *filter, unsigned long mask, 196 unsigned char jt, unsigned char jf); 197 size_t bpf_comp_jin(struct sock_filter *filter, unsigned long mask, 198 unsigned char jt, unsigned char jf); 199 200 /* Functions called by syscall_filter.c */ 201 #define ARCH_VALIDATION_LEN 3U 202 #define ALLOW_SYSCALL_LEN 2U 203 204 size_t bpf_arg_comp(struct sock_filter **pfilter, 205 int op, int argidx, unsigned long c, unsigned int label_id); 206 size_t bpf_validate_arch(struct sock_filter *filter); 207 size_t bpf_allow_syscall(struct sock_filter *filter, int nr); 208 size_t bpf_allow_syscall_args(struct sock_filter *filter, 209 int nr, unsigned int id); 210 211 #ifdef __cplusplus 212 }; /* extern "C" */ 213 #endif 214 215 #endif /* BPF_H */ 216
