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_ARG_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_COMP_LEN) 74 75 #define bpf_comp_jeq bpf_comp_jeq32 76 #define bpf_comp_jset bpf_comp_jset32 77 78 #define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) 79 80 #elif defined(BITS64) 81 /* 82 * On 64 bits, comparisons take 7 instructions: 4 for loading the argument, 83 * and 3 for the actual comparison. 84 */ 85 #define BPF_LOAD_ARG_LEN 4U 86 #define BPF_COMP_LEN 3U 87 #define BPF_ARG_COMP_LEN (BPF_LOAD_ARG_LEN + BPF_COMP_LEN) 88 89 #define bpf_comp_jeq bpf_comp_jeq64 90 #define bpf_comp_jset bpf_comp_jset64 91 92 /* Ensure that we load the logically correct offset. */ 93 #if defined(__LITTLE_ENDIAN__) || __BYTE_ORDER == __LITTLE_ENDIAN 94 #define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) 95 #define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32) 96 #else 97 #error "Unsupported endianness" 98 #endif 99 100 #else 101 #error "Unknown bit width" 102 103 #endif 104 105 /* Common jump targets. */ 106 #define NEXT 0 107 #define SKIP 1 108 #define SKIPN(_n) (_n) 109 110 /* Support for labels in BPF programs. */ 111 #define JUMP_JT 0xff 112 #define JUMP_JF 0xff 113 #define LABEL_JT 0xfe 114 #define LABEL_JF 0xfe 115 116 #define MAX_BPF_LABEL_LEN 32 117 118 #define BPF_LABELS_MAX 512U /* Each syscall could have an argument block. */ 119 struct bpf_labels { 120 size_t count; 121 struct __bpf_label { 122 const char *label; 123 unsigned int location; 124 } labels[BPF_LABELS_MAX]; 125 }; 126 127 /* BPF instruction manipulation functions and macros. */ 128 static inline size_t set_bpf_instr(struct sock_filter *instr, 129 unsigned short code, unsigned int k, 130 unsigned char jt, unsigned char jf) 131 { 132 instr->code = code; 133 instr->k = k; 134 instr->jt = jt; 135 instr->jf = jf; 136 return 1U; 137 } 138 139 #define set_bpf_stmt(_block, _code, _k) \ 140 set_bpf_instr((_block), (_code), (_k), 0, 0) 141 142 #define set_bpf_jump(_block, _code, _k, _jt, _jf) \ 143 set_bpf_instr((_block), (_code), (_k), (_jt), (_jf)) 144 145 #define set_bpf_lbl(_block, _lbl_id) \ 146 set_bpf_jump((_block), BPF_JMP+BPF_JA, (_lbl_id), \ 147 LABEL_JT, LABEL_JF) 148 149 #define set_bpf_jump_lbl(_block, _lbl_id) \ 150 set_bpf_jump((_block), BPF_JMP+BPF_JA, (_lbl_id), \ 151 JUMP_JT, JUMP_JF) 152 153 #define set_bpf_ret_kill(_block) \ 154 set_bpf_stmt((_block), BPF_RET+BPF_K, SECCOMP_RET_KILL) 155 156 #define set_bpf_ret_trap(_block) \ 157 set_bpf_stmt((_block), BPF_RET+BPF_K, SECCOMP_RET_TRAP) 158 159 #define set_bpf_ret_errno(_block, _errno) \ 160 set_bpf_stmt((_block), BPF_RET+BPF_K, \ 161 SECCOMP_RET_ERRNO | ((_errno) & SECCOMP_RET_DATA)) 162 163 #define set_bpf_ret_allow(_block) \ 164 set_bpf_stmt((_block), BPF_RET+BPF_K, SECCOMP_RET_ALLOW) 165 166 #define bpf_load_syscall_nr(_filter) \ 167 set_bpf_stmt((_filter), BPF_LD+BPF_W+BPF_ABS, syscall_nr) 168 169 /* BPF label functions. */ 170 int bpf_resolve_jumps(struct bpf_labels *labels, 171 struct sock_filter *filter, size_t count); 172 int bpf_label_id(struct bpf_labels *labels, const char *label); 173 void free_label_strings(struct bpf_labels *labels); 174 175 /* BPF helper functions. */ 176 size_t bpf_load_arg(struct sock_filter *filter, int argidx); 177 size_t bpf_comp_jeq(struct sock_filter *filter, unsigned long c, 178 unsigned char jt, unsigned char jf); 179 size_t bpf_comp_jset(struct sock_filter *filter, unsigned long mask, 180 unsigned char jt, unsigned char jf); 181 size_t bpf_comp_jin(struct sock_filter *filter, unsigned long mask, 182 unsigned char jt, unsigned char jf); 183 184 /* Functions called by syscall_filter.c */ 185 #define ARCH_VALIDATION_LEN 3U 186 #define ALLOW_SYSCALL_LEN 2U 187 188 size_t bpf_arg_comp(struct sock_filter **pfilter, 189 int op, int argidx, unsigned long c, unsigned int label_id); 190 size_t bpf_validate_arch(struct sock_filter *filter); 191 size_t bpf_allow_syscall(struct sock_filter *filter, int nr); 192 size_t bpf_allow_syscall_args(struct sock_filter *filter, 193 int nr, unsigned int id); 194 195 /* Debug functions. */ 196 void dump_bpf_prog(struct sock_fprog *fprog); 197 void dump_bpf_filter(struct sock_filter *filter, unsigned short len); 198 199 #ifdef __cplusplus 200 }; /* extern "C" */ 201 #endif 202 203 #endif /* BPF_H */ 204
