Merge branch '24-drivers-net'
[keystone-linux/linux.git] / samples / seccomp / bpf-helper.c
1 /*
2  * Seccomp BPF helper functions
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_ATTACH_SECCOMP_FILTER).
10  */
12 #include <stdio.h>
13 #include <string.h>
15 #include "bpf-helper.h"
17 int bpf_resolve_jumps(struct bpf_labels *labels,
18                       struct sock_filter *filter, size_t count)
19 {
20         struct sock_filter *begin = filter;
21         __u8 insn = count - 1;
23         if (count < 1)
24                 return -1;
25         /*
26         * Walk it once, backwards, to build the label table and do fixups.
27         * Since backward jumps are disallowed by BPF, this is easy.
28         */
29         filter += insn;
30         for (; filter >= begin; --insn, --filter) {
31                 if (filter->code != (BPF_JMP+BPF_JA))
32                         continue;
33                 switch ((filter->jt<<8)|filter->jf) {
34                 case (JUMP_JT<<8)|JUMP_JF:
35                         if (labels->labels[filter->k].location == 0xffffffff) {
36                                 fprintf(stderr, "Unresolved label: '%s'\n",
37                                         labels->labels[filter->k].label);
38                                 return 1;
39                         }
40                         filter->k = labels->labels[filter->k].location -
41                                     (insn + 1);
42                         filter->jt = 0;
43                         filter->jf = 0;
44                         continue;
45                 case (LABEL_JT<<8)|LABEL_JF:
46                         if (labels->labels[filter->k].location != 0xffffffff) {
47                                 fprintf(stderr, "Duplicate label use: '%s'\n",
48                                         labels->labels[filter->k].label);
49                                 return 1;
50                         }
51                         labels->labels[filter->k].location = insn;
52                         filter->k = 0; /* fall through */
53                         filter->jt = 0;
54                         filter->jf = 0;
55                         continue;
56                 }
57         }
58         return 0;
59 }
61 /* Simple lookup table for labels. */
62 __u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label)
63 {
64         struct __bpf_label *begin = labels->labels, *end;
65         int id;
66         if (labels->count == 0) {
67                 begin->label = label;
68                 begin->location = 0xffffffff;
69                 labels->count++;
70                 return 0;
71         }
72         end = begin + labels->count;
73         for (id = 0; begin < end; ++begin, ++id) {
74                 if (!strcmp(label, begin->label))
75                         return id;
76         }
77         begin->label = label;
78         begin->location = 0xffffffff;
79         labels->count++;
80         return id;
81 }
83 void seccomp_bpf_print(struct sock_filter *filter, size_t count)
84 {
85         struct sock_filter *end = filter + count;
86         for ( ; filter < end; ++filter)
87                 printf("{ code=%u,jt=%u,jf=%u,k=%u },\n",
88                         filter->code, filter->jt, filter->jf, filter->k);
89 }