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96 lines
2.4 KiB
96 lines
2.4 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Seccomp BPF helper functions |
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* |
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* Copyright (c) 2012 The Chromium OS Authors <[email protected]> |
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* Author: Will Drewry <[email protected]> |
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* |
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* The code may be used by anyone for any purpose, |
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* and can serve as a starting point for developing |
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* applications using prctl(PR_ATTACH_SECCOMP_FILTER). |
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*/ |
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#include <stdio.h> |
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#include <stdlib.h> |
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#include <string.h> |
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#include "bpf-helper.h" |
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int bpf_resolve_jumps(struct bpf_labels *labels, |
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struct sock_filter *filter, size_t count) |
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{ |
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size_t i; |
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if (count < 1 || count > BPF_MAXINSNS) |
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return -1; |
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/* |
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* Walk it once, backwards, to build the label table and do fixups. |
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* Since backward jumps are disallowed by BPF, this is easy. |
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*/ |
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for (i = 0; i < count; ++i) { |
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size_t offset = count - i - 1; |
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struct sock_filter *instr = &filter[offset]; |
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if (instr->code != (BPF_JMP+BPF_JA)) |
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continue; |
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switch ((instr->jt<<8)|instr->jf) { |
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case (JUMP_JT<<8)|JUMP_JF: |
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if (labels->labels[instr->k].location == 0xffffffff) { |
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fprintf(stderr, "Unresolved label: '%s'\n", |
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labels->labels[instr->k].label); |
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return 1; |
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} |
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instr->k = labels->labels[instr->k].location - |
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(offset + 1); |
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instr->jt = 0; |
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instr->jf = 0; |
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continue; |
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case (LABEL_JT<<8)|LABEL_JF: |
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if (labels->labels[instr->k].location != 0xffffffff) { |
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fprintf(stderr, "Duplicate label use: '%s'\n", |
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labels->labels[instr->k].label); |
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return 1; |
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} |
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labels->labels[instr->k].location = offset; |
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instr->k = 0; /* fall through */ |
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instr->jt = 0; |
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instr->jf = 0; |
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continue; |
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} |
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} |
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return 0; |
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} |
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/* Simple lookup table for labels. */ |
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__u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label) |
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{ |
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struct __bpf_label *begin = labels->labels, *end; |
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int id; |
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if (labels->count == BPF_LABELS_MAX) { |
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fprintf(stderr, "Too many labels\n"); |
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exit(1); |
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} |
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if (labels->count == 0) { |
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begin->label = label; |
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begin->location = 0xffffffff; |
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labels->count++; |
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return 0; |
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} |
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end = begin + labels->count; |
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for (id = 0; begin < end; ++begin, ++id) { |
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if (!strcmp(label, begin->label)) |
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return id; |
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} |
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begin->label = label; |
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begin->location = 0xffffffff; |
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labels->count++; |
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return id; |
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} |
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void seccomp_bpf_print(struct sock_filter *filter, size_t count) |
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{ |
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struct sock_filter *end = filter + count; |
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for ( ; filter < end; ++filter) |
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printf("{ code=%u,jt=%u,jf=%u,k=%u },\n", |
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filter->code, filter->jt, filter->jf, filter->k); |
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}
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