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1// SPDX-License-Identifier: GPL-2.02/*3 * Seccomp BPF helper functions4 *5 * Copyright (c) 2012 The Chromium OS Authors <chromium-os-dev@chromium.org>6 * Author: Will Drewry <wad@chromium.org>7 *8 * The code may be used by anyone for any purpose,9 * and can serve as a starting point for developing10 * applications using prctl(PR_ATTACH_SECCOMP_FILTER).11 */12 13#include <stdio.h>14#include <stdlib.h>15#include <string.h>16 17#include "bpf-helper.h"18 19int bpf_resolve_jumps(struct bpf_labels *labels,20 struct sock_filter *filter, size_t count)21{22 size_t i;23 24 if (count < 1 || count > BPF_MAXINSNS)25 return -1;26 /*27 * Walk it once, backwards, to build the label table and do fixups.28 * Since backward jumps are disallowed by BPF, this is easy.29 */30 for (i = 0; i < count; ++i) {31 size_t offset = count - i - 1;32 struct sock_filter *instr = &filter[offset];33 if (instr->code != (BPF_JMP+BPF_JA))34 continue;35 switch ((instr->jt<<8)|instr->jf) {36 case (JUMP_JT<<8)|JUMP_JF:37 if (labels->labels[instr->k].location == 0xffffffff) {38 fprintf(stderr, "Unresolved label: '%s'\n",39 labels->labels[instr->k].label);40 return 1;41 }42 instr->k = labels->labels[instr->k].location -43 (offset + 1);44 instr->jt = 0;45 instr->jf = 0;46 continue;47 case (LABEL_JT<<8)|LABEL_JF:48 if (labels->labels[instr->k].location != 0xffffffff) {49 fprintf(stderr, "Duplicate label use: '%s'\n",50 labels->labels[instr->k].label);51 return 1;52 }53 labels->labels[instr->k].location = offset;54 instr->k = 0; /* fall through */55 instr->jt = 0;56 instr->jf = 0;57 continue;58 }59 }60 return 0;61}62 63/* Simple lookup table for labels. */64__u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label)65{66 struct __bpf_label *begin = labels->labels, *end;67 int id;68 69 if (labels->count == BPF_LABELS_MAX) {70 fprintf(stderr, "Too many labels\n");71 exit(1);72 }73 if (labels->count == 0) {74 begin->label = label;75 begin->location = 0xffffffff;76 labels->count++;77 return 0;78 }79 end = begin + labels->count;80 for (id = 0; begin < end; ++begin, ++id) {81 if (!strcmp(label, begin->label))82 return id;83 }84 begin->label = label;85 begin->location = 0xffffffff;86 labels->count++;87 return id;88}89 90void seccomp_bpf_print(struct sock_filter *filter, size_t count)91{92 struct sock_filter *end = filter + count;93 for ( ; filter < end; ++filter)94 printf("{ code=%u,jt=%u,jf=%u,k=%u },\n",95 filter->code, filter->jt, filter->jf, filter->k);96}97