1 /*
2 * Copyright (C) 2015 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <stdio.h>
18
19 #include <string>
20
21 #include "fs_mgr.h"
22 #include "fs_mgr_priv.h"
23
24 // Realistically, this file should be part of the android::fs_mgr namespace;
25 using namespace android::fs_mgr;
26
27 // https://source.android.com/devices/tech/ota/ab/ab_implement#partitions
28 // All partitions that are A/B-ed should be named as follows (slots are always
29 // named a, b, etc.): boot_a, boot_b, system_a, system_b, vendor_a, vendor_b.
other_suffix(const std::string & slot_suffix)30 static std::string other_suffix(const std::string& slot_suffix) {
31 if (slot_suffix == "_a") {
32 return "_b";
33 }
34 if (slot_suffix == "_b") {
35 return "_a";
36 }
37 return "";
38 }
39
40 // Returns "_b" or "_a", which is *the other* slot of androidboot.slot_suffix
41 // in kernel cmdline, or an empty string if that parameter does not exist.
fs_mgr_get_other_slot_suffix()42 std::string fs_mgr_get_other_slot_suffix() {
43 return other_suffix(fs_mgr_get_slot_suffix());
44 }
45
46 // Returns "_a" or "_b" based on androidboot.slot_suffix in kernel cmdline, or an empty string
47 // if that parameter does not exist.
fs_mgr_get_slot_suffix()48 std::string fs_mgr_get_slot_suffix() {
49 std::string ab_suffix;
50
51 fs_mgr_get_boot_config("slot_suffix", &ab_suffix);
52 return ab_suffix;
53 }
54
55 // Updates |fstab| for slot_suffix. Returns true on success, false on error.
fs_mgr_update_for_slotselect(Fstab * fstab)56 bool fs_mgr_update_for_slotselect(Fstab* fstab) {
57 std::string ab_suffix;
58
59 for (auto& entry : *fstab) {
60 if (!entry.fs_mgr_flags.slot_select && !entry.fs_mgr_flags.slot_select_other) {
61 continue;
62 }
63
64 if (ab_suffix.empty()) {
65 ab_suffix = fs_mgr_get_slot_suffix();
66 // Return false if failed to get ab_suffix when MF_SLOTSELECT is specified.
67 if (ab_suffix.empty()) return false;
68 }
69
70 const auto& update_suffix =
71 entry.fs_mgr_flags.slot_select ? ab_suffix : other_suffix(ab_suffix);
72 entry.blk_device = entry.blk_device + update_suffix;
73 entry.logical_partition_name = entry.logical_partition_name + update_suffix;
74 }
75 return true;
76 }
77