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-rw-r--r--samples/seccomp/bpf-helper.h238
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diff --git a/samples/seccomp/bpf-helper.h b/samples/seccomp/bpf-helper.h
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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
26struct bpf_labels {
27 int count;
28 struct __bpf_label {
29 const char *label;
30 __u32 location;
31 } labels[BPF_LABELS_MAX];
32};
33
34int 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);
37void 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__
62/* Map all width-sensitive operations */
63#if __BITS_PER_LONG == 32
64
65#define JEQ(x, jt) JEQ32(x, EXPAND(jt))
66#define JNE(x, jt) JNE32(x, EXPAND(jt))
67#define JGT(x, jt) JGT32(x, EXPAND(jt))
68#define JLT(x, jt) JLT32(x, EXPAND(jt))
69#define JGE(x, jt) JGE32(x, EXPAND(jt))
70#define JLE(x, jt) JLE32(x, EXPAND(jt))
71#define JA(x, jt) JA32(x, EXPAND(jt))
72#define ARG(i) ARG_32(i)
73#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
74
75#elif __BITS_PER_LONG == 64
76
77/* Ensure that we load the logically correct offset. */
78#if __BYTE_ORDER == __LITTLE_ENDIAN
79#define ENDIAN(_lo, _hi) _lo, _hi
80#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
81#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32)
82#elif __BYTE_ORDER == __BIG_ENDIAN
83#define ENDIAN(_lo, _hi) _hi, _lo
84#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32)
85#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
86#else
87#error "Unknown endianness"
88#endif
89
90union arg64 {
91 struct {
92 __u32 ENDIAN(lo32, hi32);
93 };
94 __u64 u64;
95};
96
97#define JEQ(x, jt) \
98 JEQ64(((union arg64){.u64 = (x)}).lo32, \
99 ((union arg64){.u64 = (x)}).hi32, \
100 EXPAND(jt))
101#define JGT(x, jt) \
102 JGT64(((union arg64){.u64 = (x)}).lo32, \
103 ((union arg64){.u64 = (x)}).hi32, \
104 EXPAND(jt))
105#define JGE(x, jt) \
106 JGE64(((union arg64){.u64 = (x)}).lo32, \
107 ((union arg64){.u64 = (x)}).hi32, \
108 EXPAND(jt))
109#define JNE(x, jt) \
110 JNE64(((union arg64){.u64 = (x)}).lo32, \
111 ((union arg64){.u64 = (x)}).hi32, \
112 EXPAND(jt))
113#define JLT(x, jt) \
114 JLT64(((union arg64){.u64 = (x)}).lo32, \
115 ((union arg64){.u64 = (x)}).hi32, \
116 EXPAND(jt))
117#define JLE(x, jt) \
118 JLE64(((union arg64){.u64 = (x)}).lo32, \
119 ((union arg64){.u64 = (x)}).hi32, \
120 EXPAND(jt))
121
122#define JA(x, jt) \
123 JA64(((union arg64){.u64 = (x)}).lo32, \
124 ((union arg64){.u64 = (x)}).hi32, \
125 EXPAND(jt))
126#define ARG(i) ARG_64(i)
127
128#else
129#error __BITS_PER_LONG value unusable.
130#endif
131
132/* Loads the arg into A */
133#define ARG_32(idx) \
134 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx))
135
136/* Loads hi into A and lo in X */
137#define ARG_64(idx) \
138 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)), \
139 BPF_STMT(BPF_ST, 0), /* lo -> M[0] */ \
140 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, HI_ARG(idx)), \
141 BPF_STMT(BPF_ST, 1) /* hi -> M[1] */
142
143#define JEQ32(value, jt) \
144 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 0, 1), \
145 jt
146
147#define JNE32(value, jt) \
148 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 1, 0), \
149 jt
150
151/* Checks the lo, then swaps to check the hi. A=lo,X=hi */
152#define JEQ64(lo, hi, jt) \
153 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
154 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
155 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \
156 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
157 jt, \
158 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
159
160#define JNE64(lo, hi, jt) \
161 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 5, 0), \
162 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
163 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \
164 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
165 jt, \
166 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
167
168#define JA32(value, jt) \
169 BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \
170 jt
171
172#define JA64(lo, hi, jt) \
173 BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \
174 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
175 BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \
176 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
177 jt, \
178 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
179
180#define JGE32(value, jt) \
181 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \
182 jt
183
184#define JLT32(value, jt) \
185 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \
186 jt
187
188/* Shortcut checking if hi > arg.hi. */
189#define JGE64(lo, hi, jt) \
190 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
191 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
192 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
193 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \
194 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
195 jt, \
196 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
197
198#define JLT64(lo, hi, jt) \
199 BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \
200 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
201 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
202 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
203 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
204 jt, \
205 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
206
207#define JGT32(value, jt) \
208 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \
209 jt
210
211#define JLE32(value, jt) \
212 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \
213 jt
214
215/* Check hi > args.hi first, then do the GE checking */
216#define JGT64(lo, hi, jt) \
217 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
218 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
219 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
220 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \
221 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
222 jt, \
223 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
224
225#define JLE64(lo, hi, jt) \
226 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 6, 0), \
227 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \
228 BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
229 BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
230 BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
231 jt, \
232 BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
233
234#define LOAD_SYSCALL_NR \
235 BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
236 offsetof(struct seccomp_data, nr))
237
238#endif /* __BPF_HELPER_H__ */
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