use a single file for storing persistent properties
We have seen that storing persistent properties in separate files
causes increased boot latency compared to if they were stored in a
single contiguous file.
This change creates a simple format for a contiguously stored property
file, and adds the support for arbitrary characters in the names of
persistent properties, which previously had been restricted. It has a
mechanism for converting older devices to the new format as well.
Bug: 64392887
Test: boot bullhead with new properties
Test: boot bullhead and verify old properties are converted to the new
property file
Test: corrupt property file and ensure that it gets recovered from memory
Test: new unit tests
Change-Id: I60d8201d655ce5c97b33faae81d5ca8dbbb21a14
diff --git a/init/persistent_properties.cpp b/init/persistent_properties.cpp
new file mode 100644
index 0000000..66fa011
--- /dev/null
+++ b/init/persistent_properties.cpp
@@ -0,0 +1,341 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include "persistent_properties.h"
+
+#include <dirent.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/system_properties.h>
+#include <sys/types.h>
+
+#include <memory>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/strings.h>
+#include <android-base/unique_fd.h>
+
+#include "util.h"
+
+using android::base::ReadFdToString;
+using android::base::StartsWith;
+using android::base::WriteStringToFd;
+using android::base::unique_fd;
+
+namespace android {
+namespace init {
+
+std::string persistent_property_filename = "/data/property/persistent_properties";
+
+namespace {
+
+constexpr const uint32_t kMagic = 0x8495E0B4;
+constexpr const char kLegacyPersistentPropertyDir[] = "/data/property";
+
+Result<std::vector<std::pair<std::string, std::string>>> LoadLegacyPersistentProperties() {
+ std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(kLegacyPersistentPropertyDir), closedir);
+ if (!dir) {
+ return ErrnoError() << "Unable to open persistent property directory \""
+ << kLegacyPersistentPropertyDir << "\"";
+ }
+
+ std::vector<std::pair<std::string, std::string>> persistent_properties;
+ dirent* entry;
+ while ((entry = readdir(dir.get())) != nullptr) {
+ if (!StartsWith(entry->d_name, "persist.")) {
+ continue;
+ }
+ if (entry->d_type != DT_REG) {
+ continue;
+ }
+
+ unique_fd fd(openat(dirfd(dir.get()), entry->d_name, O_RDONLY | O_NOFOLLOW));
+ if (fd == -1) {
+ PLOG(ERROR) << "Unable to open persistent property file \"" << entry->d_name << "\"";
+ continue;
+ }
+
+ struct stat sb;
+ if (fstat(fd, &sb) == -1) {
+ PLOG(ERROR) << "fstat on property file \"" << entry->d_name << "\" failed";
+ continue;
+ }
+
+ // File must not be accessible to others, be owned by root/root, and
+ // not be a hard link to any other file.
+ if (((sb.st_mode & (S_IRWXG | S_IRWXO)) != 0) || sb.st_uid != 0 || sb.st_gid != 0 ||
+ sb.st_nlink != 1) {
+ PLOG(ERROR) << "skipping insecure property file " << entry->d_name
+ << " (uid=" << sb.st_uid << " gid=" << sb.st_gid << " nlink=" << sb.st_nlink
+ << " mode=" << std::oct << sb.st_mode << ")";
+ continue;
+ }
+
+ std::string value;
+ if (ReadFdToString(fd, &value)) {
+ persistent_properties.emplace_back(entry->d_name, value);
+ } else {
+ PLOG(ERROR) << "Unable to read persistent property file " << entry->d_name;
+ }
+ }
+ return persistent_properties;
+}
+
+void RemoveLegacyPersistentPropertyFiles() {
+ std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(kLegacyPersistentPropertyDir), closedir);
+ if (!dir) {
+ PLOG(ERROR) << "Unable to open persistent property directory \""
+ << kLegacyPersistentPropertyDir << "\"";
+ return;
+ }
+
+ dirent* entry;
+ while ((entry = readdir(dir.get())) != nullptr) {
+ if (!StartsWith(entry->d_name, "persist.")) {
+ continue;
+ }
+ if (entry->d_type != DT_REG) {
+ continue;
+ }
+ unlinkat(dirfd(dir.get()), entry->d_name, 0);
+ }
+}
+
+std::vector<std::pair<std::string, std::string>> LoadPersistentPropertiesFromMemory() {
+ std::vector<std::pair<std::string, std::string>> properties;
+ __system_property_foreach(
+ [](const prop_info* pi, void* cookie) {
+ __system_property_read_callback(
+ pi,
+ [](void* cookie, const char* name, const char* value, unsigned serial) {
+ if (StartsWith(name, "persist.")) {
+ auto properties =
+ reinterpret_cast<std::vector<std::pair<std::string, std::string>>*>(
+ cookie);
+ properties->emplace_back(name, value);
+ }
+ },
+ cookie);
+ },
+ &properties);
+ return properties;
+}
+
+class PersistentPropertyFileParser {
+ public:
+ PersistentPropertyFileParser(const std::string& contents) : contents_(contents), position_(0) {}
+ Result<std::vector<std::pair<std::string, std::string>>> Parse();
+
+ private:
+ Result<std::string> ReadString();
+ Result<uint32_t> ReadUint32();
+
+ const std::string& contents_;
+ size_t position_;
+};
+
+Result<std::vector<std::pair<std::string, std::string>>> PersistentPropertyFileParser::Parse() {
+ std::vector<std::pair<std::string, std::string>> result;
+
+ if (auto magic = ReadUint32(); magic) {
+ if (*magic != kMagic) {
+ return Error() << "Magic value '0x" << std::hex << *magic
+ << "' does not match expected value '0x" << kMagic << "'";
+ }
+ } else {
+ return Error() << "Could not read magic value: " << magic.error();
+ }
+
+ if (auto version = ReadUint32(); version) {
+ if (*version != 1) {
+ return Error() << "Version '" << *version
+ << "' does not match any compatible version: (1)";
+ }
+ } else {
+ return Error() << "Could not read version: " << version.error();
+ }
+
+ auto num_properties = ReadUint32();
+ if (!num_properties) {
+ return Error() << "Could not read num_properties: " << num_properties.error();
+ }
+
+ while (position_ < contents_.size()) {
+ auto key = ReadString();
+ if (!key) {
+ return Error() << "Could not read key: " << key.error();
+ }
+ if (!StartsWith(*key, "persist.")) {
+ return Error() << "Property '" << *key << "' does not starts with 'persist.'";
+ }
+ auto value = ReadString();
+ if (!value) {
+ return Error() << "Could not read value: " << value.error();
+ }
+ result.emplace_back(*key, *value);
+ }
+
+ if (result.size() != *num_properties) {
+ return Error() << "Mismatch of number of persistent properties read, " << result.size()
+ << " and number of persistent properties expected, " << *num_properties;
+ }
+
+ return result;
+}
+
+Result<std::string> PersistentPropertyFileParser::ReadString() {
+ auto string_length = ReadUint32();
+ if (!string_length) {
+ return Error() << "Could not read size for string";
+ }
+
+ if (position_ + *string_length > contents_.size()) {
+ return Error() << "String size would cause it to overflow the input buffer";
+ }
+ auto result = std::string(contents_, position_, *string_length);
+ position_ += *string_length;
+ return result;
+}
+
+Result<uint32_t> PersistentPropertyFileParser::ReadUint32() {
+ if (position_ + 3 > contents_.size()) {
+ return Error() << "Input buffer not large enough to read uint32_t";
+ }
+ uint32_t result = *reinterpret_cast<const uint32_t*>(&contents_[position_]);
+ position_ += sizeof(uint32_t);
+ return result;
+}
+
+} // namespace
+
+Result<std::vector<std::pair<std::string, std::string>>> LoadPersistentPropertyFile() {
+ const std::string temp_filename = persistent_property_filename + ".tmp";
+ if (access(temp_filename.c_str(), F_OK) == 0) {
+ LOG(INFO)
+ << "Found temporary property file while attempting to persistent system properties"
+ " a previous persistent property write may have failed";
+ unlink(temp_filename.c_str());
+ }
+ auto file_contents = ReadFile(persistent_property_filename);
+ if (!file_contents) {
+ return Error() << "Unable to read persistent property file: " << file_contents.error();
+ }
+ auto parsed_contents = PersistentPropertyFileParser(*file_contents).Parse();
+ if (!parsed_contents) {
+ // If the file cannot be parsed, then we don't have any recovery mechanisms, so we delete
+ // it to allow for future writes to take place successfully.
+ unlink(persistent_property_filename.c_str());
+ return Error() << "Unable to parse persistent property file: " << parsed_contents.error();
+ }
+ return parsed_contents;
+}
+
+std::string GenerateFileContents(
+ const std::vector<std::pair<std::string, std::string>>& persistent_properties) {
+ std::string result;
+
+ uint32_t magic = kMagic;
+ result.append(reinterpret_cast<char*>(&magic), sizeof(uint32_t));
+
+ uint32_t version = 1;
+ result.append(reinterpret_cast<char*>(&version), sizeof(uint32_t));
+
+ uint32_t num_properties = persistent_properties.size();
+ result.append(reinterpret_cast<char*>(&num_properties), sizeof(uint32_t));
+
+ for (const auto& [key, value] : persistent_properties) {
+ uint32_t key_length = key.length();
+ result.append(reinterpret_cast<char*>(&key_length), sizeof(uint32_t));
+ result.append(key);
+ uint32_t value_length = value.length();
+ result.append(reinterpret_cast<char*>(&value_length), sizeof(uint32_t));
+ result.append(value);
+ }
+ return result;
+}
+
+Result<Success> WritePersistentPropertyFile(
+ const std::vector<std::pair<std::string, std::string>>& persistent_properties) {
+ auto file_contents = GenerateFileContents(persistent_properties);
+
+ const std::string temp_filename = persistent_property_filename + ".tmp";
+ unique_fd fd(TEMP_FAILURE_RETRY(
+ open(temp_filename.c_str(), O_WRONLY | O_CREAT | O_NOFOLLOW | O_TRUNC | O_CLOEXEC, 0600)));
+ if (fd == -1) {
+ return ErrnoError() << "Could not open temporary properties file";
+ }
+ if (!WriteStringToFd(file_contents, fd)) {
+ return ErrnoError() << "Unable to write file contents";
+ }
+ fsync(fd);
+ fd.reset();
+
+ if (rename(temp_filename.c_str(), persistent_property_filename.c_str())) {
+ int saved_errno = errno;
+ unlink(temp_filename.c_str());
+ return Error(saved_errno) << "Unable to rename persistent property file";
+ }
+ return Success();
+}
+
+// Persistent properties are not written often, so we rather not keep any data in memory and read
+// then rewrite the persistent property file for each update.
+void WritePersistentProperty(const std::string& name, const std::string& value) {
+ auto persistent_properties = LoadPersistentPropertyFile();
+ if (!persistent_properties) {
+ LOG(ERROR) << "Recovering persistent properties from memory: "
+ << persistent_properties.error();
+ persistent_properties = LoadPersistentPropertiesFromMemory();
+ }
+ auto it = std::find_if(persistent_properties->begin(), persistent_properties->end(),
+ [&name](const auto& entry) { return entry.first == name; });
+ if (it != persistent_properties->end()) {
+ *it = {name, value};
+ } else {
+ persistent_properties->emplace_back(name, value);
+ }
+
+ if (auto result = WritePersistentPropertyFile(*persistent_properties); !result) {
+ LOG(ERROR) << "Could not store persistent property: " << result.error();
+ }
+}
+
+std::vector<std::pair<std::string, std::string>> LoadPersistentProperties() {
+ auto persistent_properties = LoadPersistentPropertyFile();
+
+ if (!persistent_properties) {
+ LOG(ERROR) << "Could not load single persistent property file, trying legacy directory: "
+ << persistent_properties.error();
+ persistent_properties = LoadLegacyPersistentProperties();
+ if (!persistent_properties) {
+ LOG(ERROR) << "Unable to load legacy persistent properties: "
+ << persistent_properties.error();
+ return {};
+ }
+ if (auto result = WritePersistentPropertyFile(*persistent_properties); result) {
+ RemoveLegacyPersistentPropertyFiles();
+ } else {
+ LOG(ERROR) << "Unable to write single persistent property file: " << result.error();
+ // Fall through so that we still set the properties that we've read.
+ }
+ }
+
+ return *persistent_properties;
+}
+
+} // namespace init
+} // namespace android