Hongyi Zhang | 50a4e01 | 2018-09-26 21:20:03 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2018 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 | package com.android.server.am; |
| 18 | |
| 19 | import android.content.ContentResolver; |
| 20 | import android.database.ContentObserver; |
| 21 | import android.net.Uri; |
| 22 | import android.os.Build; |
| 23 | import android.os.SystemProperties; |
| 24 | import android.provider.Settings; |
| 25 | import android.text.TextUtils; |
| 26 | import android.util.Slog; |
| 27 | |
| 28 | import com.android.internal.annotations.VisibleForTesting; |
| 29 | |
| 30 | import java.io.BufferedReader; |
| 31 | import java.io.File; |
| 32 | import java.io.FileReader; |
| 33 | import java.io.IOException; |
| 34 | import java.util.HashSet; |
| 35 | |
| 36 | /** |
| 37 | * Maps system settings to system properties. |
| 38 | * <p>The properties are dynamically updated when settings change. |
| 39 | */ |
| 40 | class SettingsToPropertiesMapper { |
| 41 | |
| 42 | private static final String TAG = "SettingsToPropertiesMapper"; |
| 43 | |
| 44 | private static final String SYSTEM_PROPERTY_PREFIX = "persist.device_config."; |
| 45 | |
| 46 | private static final String RESET_PERFORMED_PROPERTY = "device_config.reset_performed"; |
| 47 | |
| 48 | private static final String RESET_RECORD_FILE_PATH = |
| 49 | "/data/server_configurable_flags/reset_flags"; |
| 50 | |
| 51 | private static final String SYSTEM_PROPERTY_VALID_CHARACTERS_REGEX = "^[\\w\\.\\-@:]*$"; |
| 52 | |
| 53 | private static final String SYSTEM_PROPERTY_INVALID_SUBSTRING = ".."; |
| 54 | |
| 55 | private static final int SYSTEM_PROPERTY_MAX_LENGTH = 92; |
| 56 | |
| 57 | // experiment flags added to Global.Settings(before new "Config" provider table is available) |
| 58 | // will be added under this category. |
| 59 | private static final String GLOBAL_SETTINGS_CATEGORY = "global_settings"; |
| 60 | |
| 61 | // Add the global setting you want to push to native level as experiment flag into this list. |
| 62 | // |
| 63 | // NOTE: please grant write permission system property prefix |
| 64 | // with format persist.experiment.[experiment_category_name]. in system_server.te and grant read |
| 65 | // permission in the corresponding .te file your feature belongs to. |
| 66 | @VisibleForTesting |
| 67 | static final String[] sGlobalSettings = new String[] { |
| 68 | }; |
| 69 | |
| 70 | @VisibleForTesting |
| 71 | static final String[] sDeviceConfigScopes = new String[] { |
| 72 | }; |
| 73 | |
| 74 | private final String[] mGlobalSettings; |
| 75 | |
| 76 | private final String[] mDeviceConfigScopes; |
| 77 | |
| 78 | private final ContentResolver mContentResolver; |
| 79 | |
| 80 | @VisibleForTesting |
| 81 | protected SettingsToPropertiesMapper(ContentResolver contentResolver, |
| 82 | String[] globalSettings, |
| 83 | String[] deviceConfigScopes) { |
| 84 | mContentResolver = contentResolver; |
| 85 | mGlobalSettings = globalSettings; |
| 86 | mDeviceConfigScopes = deviceConfigScopes; |
| 87 | } |
| 88 | |
| 89 | @VisibleForTesting |
| 90 | void updatePropertiesFromSettings() { |
| 91 | for (String globalSetting : mGlobalSettings) { |
| 92 | Uri settingUri = Settings.Global.getUriFor(globalSetting); |
| 93 | String propName = makePropertyName(GLOBAL_SETTINGS_CATEGORY, globalSetting); |
| 94 | if (settingUri == null) { |
| 95 | log("setting uri is null for globalSetting " + globalSetting); |
| 96 | continue; |
| 97 | } |
| 98 | if (propName == null) { |
| 99 | log("invalid prop name for globalSetting " + globalSetting); |
| 100 | continue; |
| 101 | } |
| 102 | |
| 103 | ContentObserver co = new ContentObserver(null) { |
| 104 | @Override |
| 105 | public void onChange(boolean selfChange) { |
| 106 | updatePropertyFromSetting(globalSetting, propName, true); |
| 107 | } |
| 108 | }; |
| 109 | |
| 110 | // only updating on starting up when no native flags reset is performed during current |
| 111 | // booting. |
| 112 | if (!isNativeFlagsResetPerformed()) { |
| 113 | updatePropertyFromSetting(globalSetting, propName, true); |
| 114 | } |
| 115 | mContentResolver.registerContentObserver(settingUri, false, co); |
| 116 | } |
| 117 | |
| 118 | // TODO: address sDeviceConfigScopes after DeviceConfig APIs are available. |
| 119 | } |
| 120 | |
| 121 | public static SettingsToPropertiesMapper start(ContentResolver contentResolver) { |
| 122 | SettingsToPropertiesMapper mapper = new SettingsToPropertiesMapper( |
| 123 | contentResolver, sGlobalSettings, sDeviceConfigScopes); |
| 124 | mapper.updatePropertiesFromSettings(); |
| 125 | return mapper; |
| 126 | } |
| 127 | |
| 128 | /** |
| 129 | * If native level flags reset has been performed as an attempt to recover from a crash loop |
| 130 | * during current device booting. |
| 131 | * @return |
| 132 | */ |
| 133 | public boolean isNativeFlagsResetPerformed() { |
| 134 | String value = systemPropertiesGet(RESET_PERFORMED_PROPERTY); |
| 135 | return "true".equals(value); |
| 136 | } |
| 137 | |
| 138 | /** |
| 139 | * return an array of native flag categories under which flags got reset during current device |
| 140 | * booting. |
| 141 | * @return |
| 142 | */ |
| 143 | public String[] getResetNativeCategories() { |
| 144 | if (!isNativeFlagsResetPerformed()) { |
| 145 | return new String[0]; |
| 146 | } |
| 147 | |
| 148 | String content = getResetFlagsFileContent(); |
| 149 | if (TextUtils.isEmpty(content)) { |
| 150 | return new String[0]; |
| 151 | } |
| 152 | |
| 153 | String[] property_names = content.split(";"); |
| 154 | HashSet<String> categories = new HashSet<>(); |
| 155 | for (String property_name : property_names) { |
| 156 | String[] segments = property_name.split("\\."); |
| 157 | if (segments.length < 3) { |
| 158 | log("failed to extract category name from property " + property_name); |
| 159 | continue; |
| 160 | } |
| 161 | categories.add(segments[2]); |
| 162 | } |
| 163 | return categories.toArray(new String[0]); |
| 164 | } |
| 165 | |
| 166 | /** |
| 167 | * system property name constructing rule: "persist.device_config.[category_name].[flag_name]". |
| 168 | * If the name contains invalid characters or substrings for system property name, |
| 169 | * will return null. |
| 170 | * @param categoryName |
| 171 | * @param flagName |
| 172 | * @return |
| 173 | */ |
| 174 | @VisibleForTesting |
| 175 | static String makePropertyName(String categoryName, String flagName) { |
| 176 | String propertyName = SYSTEM_PROPERTY_PREFIX + categoryName + "." + flagName; |
| 177 | |
| 178 | if (!propertyName.matches(SYSTEM_PROPERTY_VALID_CHARACTERS_REGEX) |
| 179 | || propertyName.contains(SYSTEM_PROPERTY_INVALID_SUBSTRING)) { |
| 180 | return null; |
| 181 | } |
| 182 | |
| 183 | return propertyName; |
| 184 | } |
| 185 | |
| 186 | private String getSetting(String name, boolean isGlobalSetting) { |
| 187 | if (isGlobalSetting) { |
| 188 | return Settings.Global.getString(mContentResolver, name); |
| 189 | } else { |
| 190 | // TODO: complete the code after DeviceConfig APIs implemented. |
| 191 | return null; |
| 192 | } |
| 193 | } |
| 194 | |
| 195 | private void setProperty(String key, String value) { |
| 196 | // Check if need to clear the property |
| 197 | if (value == null) { |
| 198 | // It's impossible to remove system property, therefore we check previous value to |
| 199 | // avoid setting an empty string if the property wasn't set. |
| 200 | if (TextUtils.isEmpty(systemPropertiesGet(key))) { |
| 201 | return; |
| 202 | } |
| 203 | value = ""; |
| 204 | } else if (value.length() > SYSTEM_PROPERTY_MAX_LENGTH) { |
| 205 | log(value + " exceeds system property max length."); |
| 206 | return; |
| 207 | } |
| 208 | |
| 209 | try { |
| 210 | systemPropertiesSet(key, value); |
| 211 | } catch (Exception e) { |
| 212 | // Failure to set a property can be caused by SELinux denial. This usually indicates |
| 213 | // that the property wasn't whitelisted in sepolicy. |
| 214 | // No need to report it on all user devices, only on debug builds. |
| 215 | log("Unable to set property " + key + " value '" + value + "'", e); |
| 216 | } |
| 217 | } |
| 218 | |
| 219 | private static void log(String msg, Exception e) { |
| 220 | if (Build.IS_DEBUGGABLE) { |
| 221 | Slog.wtf(TAG, msg, e); |
| 222 | } else { |
| 223 | Slog.e(TAG, msg, e); |
| 224 | } |
| 225 | } |
| 226 | |
| 227 | private static void log(String msg) { |
| 228 | if (Build.IS_DEBUGGABLE) { |
| 229 | Slog.wtf(TAG, msg); |
| 230 | } else { |
| 231 | Slog.e(TAG, msg); |
| 232 | } |
| 233 | } |
| 234 | |
| 235 | @VisibleForTesting |
| 236 | protected String systemPropertiesGet(String key) { |
| 237 | return SystemProperties.get(key); |
| 238 | } |
| 239 | |
| 240 | @VisibleForTesting |
| 241 | protected void systemPropertiesSet(String key, String value) { |
| 242 | SystemProperties.set(key, value); |
| 243 | } |
| 244 | |
| 245 | @VisibleForTesting |
| 246 | protected String getResetFlagsFileContent() { |
| 247 | String content = null; |
| 248 | try { |
| 249 | File reset_flag_file = new File(RESET_RECORD_FILE_PATH); |
| 250 | BufferedReader br = new BufferedReader(new FileReader(reset_flag_file)); |
| 251 | content = br.readLine(); |
| 252 | |
| 253 | br.close(); |
| 254 | } catch (IOException ioe) { |
| 255 | log("failed to read file " + RESET_RECORD_FILE_PATH, ioe); |
| 256 | } |
| 257 | return content; |
| 258 | } |
| 259 | |
| 260 | @VisibleForTesting |
| 261 | void updatePropertyFromSetting(String settingName, String propName, boolean isGlobalSetting) { |
| 262 | String settingValue = getSetting(settingName, isGlobalSetting); |
| 263 | setProperty(propName, settingValue); |
| 264 | } |
| 265 | } |