sandboxed-api/sandboxed_api/sandbox2/util/bpf_helper.c
Sandboxed API Team 5aa13876a4 Formatting fixes.
PiperOrigin-RevId: 239159980
Change-Id: Ic6185368392622bf3f4c661e37f6b9fcca0d60a6
2019-03-19 03:41:32 -07:00

109 lines
3.0 KiB
C

// Copyright 2019 Google LLC. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Seccomp BPF helper functions, modified from the Chromium OS version. The
// original notice is below.
//
// 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 "sandboxed_api/sandbox2/util/bpf_helper.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.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);
}