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| 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 | */ |
| 11 | |
| 12 | #include <stdio.h> |
| 13 | #include <string.h> |
| 14 | |
| 15 | #include "bpf-helper.h" |
| 16 | |
| 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; |
| 22 | |
| 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 | } |
| 60 | |
| 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 | } |
| 82 | |
| 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 | } |
| 90 |
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
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v3.9
