1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * Seccomp BPF helper functions
 4 *
 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 developing
10 * 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}

 
 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 <stdlib.h>
14#include <string.h>
15
16#include "bpf-helper.h"
17
18int bpf_resolve_jumps(struct bpf_labels *labels,
19		      struct sock_filter *filter, size_t count)
20{
21	size_t i;
22
23	if (count < 1 || count > BPF_MAXINSNS)
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	for (i = 0; i < count; ++i) {
30		size_t offset = count - i - 1;
31		struct sock_filter *instr = &filter[offset];
32		if (instr->code != (BPF_JMP+BPF_JA))
33			continue;
34		switch ((instr->jt<<8)|instr->jf) {
35		case (JUMP_JT<<8)|JUMP_JF:
36			if (labels->labels[instr->k].location == 0xffffffff) {
37				fprintf(stderr, "Unresolved label: '%s'\n",
38					labels->labels[instr->k].label);
39				return 1;
40			}
41			instr->k = labels->labels[instr->k].location -
42				    (offset + 1);
43			instr->jt = 0;
44			instr->jf = 0;
45			continue;
46		case (LABEL_JT<<8)|LABEL_JF:
47			if (labels->labels[instr->k].location != 0xffffffff) {
48				fprintf(stderr, "Duplicate label use: '%s'\n",
49					labels->labels[instr->k].label);
50				return 1;
51			}
52			labels->labels[instr->k].location = offset;
53			instr->k = 0; /* fall through */
54			instr->jt = 0;
55			instr->jf = 0;
56			continue;
57		}
58	}
59	return 0;
60}
61
62/* Simple lookup table for labels. */
63__u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label)
64{
65	struct __bpf_label *begin = labels->labels, *end;
66	int id;
67
68	if (labels->count == BPF_LABELS_MAX) {
69		fprintf(stderr, "Too many labels\n");
70		exit(1);
71	}
72	if (labels->count == 0) {
73		begin->label = label;
74		begin->location = 0xffffffff;
75		labels->count++;
76		return 0;
77	}
78	end = begin + labels->count;
79	for (id = 0; begin < end; ++begin, ++id) {
80		if (!strcmp(label, begin->label))
81			return id;
82	}
83	begin->label = label;
84	begin->location = 0xffffffff;
85	labels->count++;
86	return id;
87}
88
89void seccomp_bpf_print(struct sock_filter *filter, size_t count)
90{
91	struct sock_filter *end = filter + count;
92	for ( ; filter < end; ++filter)
93		printf("{ code=%u,jt=%u,jf=%u,k=%u },\n",
94			filter->code, filter->jt, filter->jf, filter->k);
95}