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 <algorithm>
18 #include <iterator>
19 #include <string>
20 #include <vector>
21
22 #include <android-base/file.h>
23 #include <android-base/stringprintf.h>
24 #include <android-base/strings.h>
25 #include <android-base/properties.h>
26
27 #include "fs_mgr_priv.h"
28
fs_mgr_parse_boot_config(const std::string & cmdline)29 std::vector<std::pair<std::string, std::string>> fs_mgr_parse_boot_config(const std::string& cmdline) {
30 static constexpr char quote = '"';
31
32 std::vector<std::pair<std::string, std::string>> result;
33 size_t base = 0;
34 while (true) {
35 // skip quoted spans
36 auto found = base;
37 while (((found = cmdline.find_first_of(" \"", found)) != cmdline.npos) &&
38 (cmdline[found] == quote)) {
39 // unbalanced quote is ok
40 if ((found = cmdline.find(quote, found + 1)) == cmdline.npos) break;
41 ++found;
42 }
43 std::string piece;
44 auto source = cmdline.substr(base, found - base);
45 std::remove_copy(source.begin(), source.end(),
46 std::back_insert_iterator<std::string>(piece), quote);
47 auto equal_sign = piece.find('=');
48 if (equal_sign == piece.npos) {
49 if (!piece.empty()) {
50 // no difference between <key> and <key>=
51 result.emplace_back(std::move(piece), "");
52 }
53 } else {
54 result.emplace_back(piece.substr(0, equal_sign), piece.substr(equal_sign + 1));
55 }
56 if (found == cmdline.npos) break;
57 base = found + 1;
58 }
59
60 return result;
61 }
62
fs_mgr_get_boot_config_from_kernel(const std::string & cmdline,const std::string & android_key,std::string * out_val)63 bool fs_mgr_get_boot_config_from_kernel(const std::string& cmdline, const std::string& android_key,
64 std::string* out_val) {
65 FS_MGR_CHECK(out_val != nullptr);
66
67 const std::string cmdline_key("androidboot." + android_key);
68 for (const auto& [key, value] : fs_mgr_parse_boot_config(cmdline)) {
69 if (key == cmdline_key) {
70 *out_val = value;
71 return true;
72 }
73 }
74
75 *out_val = "";
76 return false;
77 }
78
79 // Tries to get the given boot config value from kernel cmdline.
80 // Returns true if successfully found, false otherwise.
fs_mgr_get_boot_config_from_kernel_cmdline(const std::string & key,std::string * out_val)81 bool fs_mgr_get_boot_config_from_kernel_cmdline(const std::string& key, std::string* out_val) {
82 std::string cmdline;
83 if (!android::base::ReadFileToString("/proc/cmdline", &cmdline)) return false;
84 if (!cmdline.empty() && cmdline.back() == '\n') {
85 cmdline.pop_back();
86 }
87 return fs_mgr_get_boot_config_from_kernel(cmdline, key, out_val);
88 }
89
90 // Tries to get the boot config value in device tree, properties and
91 // kernel cmdline (in that order). Returns 'true' if successfully
92 // found, 'false' otherwise.
fs_mgr_get_boot_config(const std::string & key,std::string * out_val)93 bool fs_mgr_get_boot_config(const std::string& key, std::string* out_val) {
94 FS_MGR_CHECK(out_val != nullptr);
95
96 // firstly, check the device tree
97 if (is_dt_compatible()) {
98 std::string file_name = get_android_dt_dir() + "/" + key;
99 if (android::base::ReadFileToString(file_name, out_val)) {
100 if (!out_val->empty()) {
101 out_val->pop_back(); // Trims the trailing '\0' out.
102 return true;
103 }
104 }
105 }
106
107 // next, check if we have "ro.boot" property already
108 *out_val = android::base::GetProperty("ro.boot." + key, "");
109 if (!out_val->empty()) {
110 return true;
111 }
112
113 // finally, fallback to kernel cmdline, properties may not be ready yet
114 if (fs_mgr_get_boot_config_from_kernel_cmdline(key, out_val)) {
115 return true;
116 }
117
118 return false;
119 }
120