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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 | ||
141 | /* Loads hi into A and lo in X */ | |
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 | ||
156 | /* Checks the lo, then swaps to check the hi. A=lo,X=hi */ | |
157 | #define JEQ64(lo, hi, jt) \ | |
158 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ | |
159 | BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ | |
160 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \ | |
161 | BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ | |
162 | jt, \ | |
163 | BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ | |
164 | ||
165 | #define JNE64(lo, hi, jt) \ | |
166 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 5, 0), \ | |
167 | BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ | |
168 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \ | |
169 | BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ | |
170 | jt, \ | |
171 | BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ | |
172 | ||
173 | #define JA32(value, jt) \ | |
174 | BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \ | |
175 | jt | |
176 | ||
177 | #define JA64(lo, hi, jt) \ | |
178 | BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \ | |
179 | BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ | |
180 | BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \ | |
181 | BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ | |
182 | jt, \ | |
183 | BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ | |
184 | ||
185 | #define JGE32(value, jt) \ | |
186 | BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \ | |
187 | jt | |
188 | ||
189 | #define JLT32(value, jt) \ | |
190 | BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \ | |
191 | jt | |
192 | ||
193 | /* Shortcut checking if hi > arg.hi. */ | |
194 | #define JGE64(lo, hi, jt) \ | |
195 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \ | |
196 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ | |
197 | BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ | |
198 | BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \ | |
199 | BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ | |
200 | jt, \ | |
201 | BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ | |
202 | ||
203 | #define JLT64(lo, hi, jt) \ | |
204 | BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \ | |
205 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ | |
206 | BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ | |
207 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \ | |
208 | BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ | |
209 | jt, \ | |
210 | BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ | |
211 | ||
212 | #define JGT32(value, jt) \ | |
213 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \ | |
214 | jt | |
215 | ||
216 | #define JLE32(value, jt) \ | |
217 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \ | |
218 | jt | |
219 | ||
220 | /* Check hi > args.hi first, then do the GE checking */ | |
221 | #define JGT64(lo, hi, jt) \ | |
222 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \ | |
223 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \ | |
224 | BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ | |
225 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \ | |
226 | BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ | |
227 | jt, \ | |
228 | BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ | |
229 | ||
230 | #define JLE64(lo, hi, jt) \ | |
231 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 6, 0), \ | |
232 | BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \ | |
233 | BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \ | |
234 | BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \ | |
235 | BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \ | |
236 | jt, \ | |
237 | BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */ | |
238 | ||
239 | #define LOAD_SYSCALL_NR \ | |
240 | BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \ | |
241 | offsetof(struct seccomp_data, nr)) | |
242 | ||
243 | #endif /* __BPF_HELPER_H__ */ |