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