aboutsummaryrefslogtreecommitdiffstats
path: root/samples/seccomp/bpf-helper.h
blob: 38ee70f3cd5b970101edd6d2edb52b4df8d73d14 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
/*
 * Example wrapper around BPF macros.
 *
 * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>
 * Author: Will Drewry <wad@chromium.org>
 *
 * The code may be used by anyone for any purpose,
 * and can serve as a starting point for developing
 * applications using prctl(PR_SET_SECCOMP, 2, ...).
 *
 * No guarantees are provided with respect to the correctness
 * or functionality of this code.
 */
#ifndef __BPF_HELPER_H__
#define __BPF_HELPER_H__

#include <asm/bitsperlong.h>	/* for __BITS_PER_LONG */
#include <endian.h>
#include <linux/filter.h>
#include <linux/seccomp.h>	/* for seccomp_data */
#include <linux/types.h>
#include <linux/unistd.h>
#include <stddef.h>

#define BPF_LABELS_MAX 256
struct bpf_labels {
	int count;
	struct __bpf_label {
		const char *label;
		__u32 location;
	} labels[BPF_LABELS_MAX];
};

int bpf_resolve_jumps(struct bpf_labels *labels,
		      struct sock_filter *filter, size_t count);
__u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label);
void seccomp_bpf_print(struct sock_filter *filter, size_t count);

#define JUMP_JT 0xff
#define JUMP_JF 0xff
#define LABEL_JT 0xfe
#define LABEL_JF 0xfe

#define ALLOW \
	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW)
#define DENY \
	BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL)
#define JUMP(labels, label) \
	BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \
		 JUMP_JT, JUMP_JF)
#define LABEL(labels, label) \
	BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \
		 LABEL_JT, LABEL_JF)
#define SYSCALL(nr, jt) \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (nr), 0, 1), \
	jt

/* Lame, but just an example */
#define FIND_LABEL(labels, label) seccomp_bpf_label((labels), #label)

#define EXPAND(...) __VA_ARGS__

/* Ensure that we load the logically correct offset. */
#if __BYTE_ORDER == __LITTLE_ENDIAN
#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
#elif __BYTE_ORDER == __BIG_ENDIAN
#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32)
#else
#error "Unknown endianness"
#endif

/* Map all width-sensitive operations */
#if __BITS_PER_LONG == 32

#define JEQ(x, jt) JEQ32(x, EXPAND(jt))
#define JNE(x, jt) JNE32(x, EXPAND(jt))
#define JGT(x, jt) JGT32(x, EXPAND(jt))
#define JLT(x, jt) JLT32(x, EXPAND(jt))
#define JGE(x, jt) JGE32(x, EXPAND(jt))
#define JLE(x, jt) JLE32(x, EXPAND(jt))
#define JA(x, jt) JA32(x, EXPAND(jt))
#define ARG(i) ARG_32(i)

#elif __BITS_PER_LONG == 64

/* Ensure that we load the logically correct offset. */
#if __BYTE_ORDER == __LITTLE_ENDIAN
#define ENDIAN(_lo, _hi) _lo, _hi
#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32)
#elif __BYTE_ORDER == __BIG_ENDIAN
#define ENDIAN(_lo, _hi) _hi, _lo
#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
#endif

union arg64 {
	struct {
		__u32 ENDIAN(lo32, hi32);
	};
	__u64 u64;
};

#define JEQ(x, jt) \
	JEQ64(((union arg64){.u64 = (x)}).lo32, \
	      ((union arg64){.u64 = (x)}).hi32, \
	      EXPAND(jt))
#define JGT(x, jt) \
	JGT64(((union arg64){.u64 = (x)}).lo32, \
	      ((union arg64){.u64 = (x)}).hi32, \
	      EXPAND(jt))
#define JGE(x, jt) \
	JGE64(((union arg64){.u64 = (x)}).lo32, \
	      ((union arg64){.u64 = (x)}).hi32, \
	      EXPAND(jt))
#define JNE(x, jt) \
	JNE64(((union arg64){.u64 = (x)}).lo32, \
	      ((union arg64){.u64 = (x)}).hi32, \
	      EXPAND(jt))
#define JLT(x, jt) \
	JLT64(((union arg64){.u64 = (x)}).lo32, \
	      ((union arg64){.u64 = (x)}).hi32, \
	      EXPAND(jt))
#define JLE(x, jt) \
	JLE64(((union arg64){.u64 = (x)}).lo32, \
	      ((union arg64){.u64 = (x)}).hi32, \
	      EXPAND(jt))

#define JA(x, jt) \
	JA64(((union arg64){.u64 = (x)}).lo32, \
	       ((union arg64){.u64 = (x)}).hi32, \
	       EXPAND(jt))
#define ARG(i) ARG_64(i)

#else
#error __BITS_PER_LONG value unusable.
#endif

/* Loads the arg into A */
#define ARG_32(idx) \
	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx))

/* Loads hi into A and lo in X */
#define ARG_64(idx) \
	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)), \
	BPF_STMT(BPF_ST, 0), /* lo -> M[0] */ \
	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, HI_ARG(idx)), \
	BPF_STMT(BPF_ST, 1) /* hi -> M[1] */

#define JEQ32(value, jt) \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 0, 1), \
	jt

#define JNE32(value, jt) \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 1, 0), \
	jt

/* Checks the lo, then swaps to check the hi. A=lo,X=hi */
#define JEQ64(lo, hi, jt) \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \
	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
	jt, \
	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */

#define JNE64(lo, hi, jt) \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 5, 0), \
	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \
	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
	jt, \
	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */

#define JA32(value, jt) \
	BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \
	jt

#define JA64(lo, hi, jt) \
	BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \
	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
	BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \
	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
	jt, \
	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */

#define JGE32(value, jt) \
	BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \
	jt

#define JLT32(value, jt) \
	BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \
	jt

/* Shortcut checking if hi > arg.hi. */
#define JGE64(lo, hi, jt) \
	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
	BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \
	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
	jt, \
	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */

#define JLT64(lo, hi, jt) \
	BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
	jt, \
	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */

#define JGT32(value, jt) \
	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \
	jt

#define JLE32(value, jt) \
	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \
	jt

/* Check hi > args.hi first, then do the GE checking */
#define JGT64(lo, hi, jt) \
	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \
	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
	jt, \
	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */

#define JLE64(lo, hi, jt) \
	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 6, 0), \
	BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \
	BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
	BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
	BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
	jt, \
	BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */

#define LOAD_SYSCALL_NR \
	BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
		 offsetof(struct seccomp_data, nr))

#endif  /* __BPF_HELPER_H__ */