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8ac270d1 WD |
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__ | |
de4bb3b9 HC |
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 | ||
8ac270d1 WD |
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) | |
8ac270d1 WD |
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 | |
8ac270d1 WD |
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 | |
8ac270d1 | 92 | #define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) |
8ac270d1 WD |
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 | ||
916cafdc | 141 | /* Loads lo into M[0] and hi into M[1] and A */ |
8ac270d1 WD |
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 | ||
916cafdc MS |
156 | #define JA32(value, jt) \ |
157 | BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \ | |
158 | jt | |
159 | ||
160 | #define JGE32(value, jt) \ | |
161 | BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \ | |
162 | jt | |
163 | ||
164 | #define JGT32(value, jt) \ | |
165 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \ | |
166 | jt | |
167 | ||
168 | #define JLE32(value, jt) \ | |
169 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \ | |
170 | jt | |
171 | ||
172 | #define JLT32(value, jt) \ | |
173 | BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \ | |
174 | jt | |
175 | ||
176 | /* | |
177 | * All the JXX64 checks assume lo is saved in M[0] and hi is saved in both | |
178 | * A and M[1]. This invariant is kept by restoring A if necessary. | |
179 | */ | |
8ac270d1 | 180 | #define JEQ64(lo, hi, jt) \ |
916cafdc | 181 | /* if (hi != arg.hi) goto NOMATCH; */ \ |
8ac270d1 WD |
182 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ |
183 | BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ | |
916cafdc | 184 | /* if (lo != arg.lo) goto NOMATCH; */ \ |
8ac270d1 | 185 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \ |
916cafdc | 186 | BPF_STMT(BPF_LD+BPF_MEM, 1), \ |
8ac270d1 | 187 | jt, \ |
916cafdc | 188 | BPF_STMT(BPF_LD+BPF_MEM, 1) |
8ac270d1 WD |
189 | |
190 | #define JNE64(lo, hi, jt) \ | |
916cafdc MS |
191 | /* if (hi != arg.hi) goto MATCH; */ \ |
192 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \ | |
193 | BPF_STMT(BPF_LD+BPF_MEM, 0), \ | |
194 | /* if (lo != arg.lo) goto MATCH; */ \ | |
8ac270d1 | 195 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \ |
916cafdc | 196 | BPF_STMT(BPF_LD+BPF_MEM, 1), \ |
8ac270d1 | 197 | jt, \ |
916cafdc | 198 | BPF_STMT(BPF_LD+BPF_MEM, 1) |
8ac270d1 WD |
199 | |
200 | #define JA64(lo, hi, jt) \ | |
916cafdc | 201 | /* if (hi & arg.hi) goto MATCH; */ \ |
8ac270d1 | 202 | BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \ |
916cafdc MS |
203 | BPF_STMT(BPF_LD+BPF_MEM, 0), \ |
204 | /* if (lo & arg.lo) goto MATCH; */ \ | |
8ac270d1 | 205 | BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \ |
916cafdc | 206 | BPF_STMT(BPF_LD+BPF_MEM, 1), \ |
8ac270d1 | 207 | jt, \ |
916cafdc | 208 | BPF_STMT(BPF_LD+BPF_MEM, 1) |
8ac270d1 | 209 | |
8ac270d1 | 210 | #define JGE64(lo, hi, jt) \ |
916cafdc | 211 | /* if (hi > arg.hi) goto MATCH; */ \ |
8ac270d1 | 212 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \ |
916cafdc | 213 | /* if (hi != arg.hi) goto NOMATCH; */ \ |
8ac270d1 | 214 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ |
916cafdc MS |
215 | BPF_STMT(BPF_LD+BPF_MEM, 0), \ |
216 | /* if (lo >= arg.lo) goto MATCH; */ \ | |
8ac270d1 | 217 | BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \ |
916cafdc | 218 | BPF_STMT(BPF_LD+BPF_MEM, 1), \ |
8ac270d1 | 219 | jt, \ |
916cafdc | 220 | BPF_STMT(BPF_LD+BPF_MEM, 1) |
8ac270d1 | 221 | |
8ac270d1 | 222 | #define JGT64(lo, hi, jt) \ |
916cafdc | 223 | /* if (hi > arg.hi) goto MATCH; */ \ |
8ac270d1 | 224 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \ |
916cafdc | 225 | /* if (hi != arg.hi) goto NOMATCH; */ \ |
8ac270d1 | 226 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ |
916cafdc MS |
227 | BPF_STMT(BPF_LD+BPF_MEM, 0), \ |
228 | /* if (lo > arg.lo) goto MATCH; */ \ | |
8ac270d1 | 229 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \ |
916cafdc | 230 | BPF_STMT(BPF_LD+BPF_MEM, 1), \ |
8ac270d1 | 231 | jt, \ |
916cafdc | 232 | BPF_STMT(BPF_LD+BPF_MEM, 1) |
8ac270d1 WD |
233 | |
234 | #define JLE64(lo, hi, jt) \ | |
916cafdc MS |
235 | /* if (hi < arg.hi) goto MATCH; */ \ |
236 | BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \ | |
237 | /* if (hi != arg.hi) goto NOMATCH; */ \ | |
238 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ | |
239 | BPF_STMT(BPF_LD+BPF_MEM, 0), \ | |
240 | /* if (lo <= arg.lo) goto MATCH; */ \ | |
8ac270d1 | 241 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \ |
916cafdc MS |
242 | BPF_STMT(BPF_LD+BPF_MEM, 1), \ |
243 | jt, \ | |
244 | BPF_STMT(BPF_LD+BPF_MEM, 1) | |
245 | ||
246 | #define JLT64(lo, hi, jt) \ | |
247 | /* if (hi < arg.hi) goto MATCH; */ \ | |
248 | BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \ | |
249 | /* if (hi != arg.hi) goto NOMATCH; */ \ | |
250 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ | |
251 | BPF_STMT(BPF_LD+BPF_MEM, 0), \ | |
252 | /* if (lo < arg.lo) goto MATCH; */ \ | |
253 | BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 2, 0), \ | |
254 | BPF_STMT(BPF_LD+BPF_MEM, 1), \ | |
8ac270d1 | 255 | jt, \ |
916cafdc | 256 | BPF_STMT(BPF_LD+BPF_MEM, 1) |
8ac270d1 WD |
257 | |
258 | #define LOAD_SYSCALL_NR \ | |
259 | BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \ | |
260 | offsetof(struct seccomp_data, nr)) | |
261 | ||
262 | #endif /* __BPF_HELPER_H__ */ |