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TOMOYO Linux Cross Reference
Linux/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
 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__
 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 
 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)
 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
 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
 92 #define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
 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__ */
244 

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