1 /*
2 * Copyright (C) 2017 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 <string>
18
19 #include <android-base/file.h>
20 #include <android-base/stringprintf.h>
21 #include <android-base/strings.h>
22 #include <android-base/properties.h>
23
24 #include "fs_mgr_priv.h"
25
26 // Tries to get the given boot config value from kernel cmdline.
27 // Returns true if successfully found, false otherwise.
fs_mgr_get_boot_config_from_kernel_cmdline(const std::string & key,std::string * out_val)28 bool fs_mgr_get_boot_config_from_kernel_cmdline(const std::string& key, std::string* out_val) {
29 FS_MGR_CHECK(out_val != nullptr);
30
31 std::string cmdline;
32 std::string cmdline_key("androidboot." + key);
33 if (android::base::ReadFileToString("/proc/cmdline", &cmdline)) {
34 for (const auto& entry : android::base::Split(android::base::Trim(cmdline), " ")) {
35 std::vector<std::string> pieces = android::base::Split(entry, "=");
36 if (pieces.size() == 2) {
37 if (pieces[0] == cmdline_key) {
38 *out_val = pieces[1];
39 return true;
40 }
41 }
42 }
43 }
44
45 return false;
46 }
47
48 // Tries to get the boot config value in properties, kernel cmdline and
49 // device tree (in that order). returns 'true' if successfully found, 'false'
50 // otherwise
fs_mgr_get_boot_config(const std::string & key,std::string * out_val)51 bool fs_mgr_get_boot_config(const std::string& key, std::string* out_val) {
52 FS_MGR_CHECK(out_val != nullptr);
53
54 // first check if we have "ro.boot" property already
55 *out_val = android::base::GetProperty("ro.boot." + key, "");
56 if (!out_val->empty()) {
57 return true;
58 }
59
60 // fallback to kernel cmdline, properties may not be ready yet
61 if (fs_mgr_get_boot_config_from_kernel_cmdline(key, out_val)) {
62 return true;
63 }
64
65 // lastly, check the device tree
66 if (is_dt_compatible()) {
67 std::string file_name = get_android_dt_dir() + "/" + key;
68 if (android::base::ReadFileToString(file_name, out_val)) {
69 if (!out_val->empty()) {
70 out_val->pop_back(); // Trims the trailing '\0' out.
71 return true;
72 }
73 }
74 }
75
76 return false;
77 }
78