Split system_properties.cpp into its component pieces
system_properties.cpp is a little bit unmanageable in its current
form, and is overdue for a refactoring into more clearly defined
components.
Of particular interest, is creating of a Contexts interface that
handles mapping of system property name -> SEContext and its
associated prop_area, and creating two classes that implement the
current and legacy functionality. This is needed as there will likely
be a third even newer way to do this mapping.
Bug: 36001741
Test: boot bullhead, system property unit tests
Change-Id: Ie75ec6fea1a95f90813918f54669d533e51327c6
diff --git a/libc/system_properties/system_properties.cpp b/libc/system_properties/system_properties.cpp
new file mode 100644
index 0000000..5d13404
--- /dev/null
+++ b/libc/system_properties/system_properties.cpp
@@ -0,0 +1,656 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <netinet/in.h>
+#include <poll.h>
+#include <stdatomic.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/select.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
+#include <sys/_system_properties.h>
+#include <sys/system_properties.h>
+
+#include <async_safe/log.h>
+
+#include "private/ErrnoRestorer.h"
+#include "private/bionic_defs.h"
+#include "private/bionic_futex.h"
+#include "private/bionic_macros.h"
+#include "private/bionic_sdk_version.h"
+
+#include "context_node.h"
+#include "contexts.h"
+#include "contexts_pre_split.h"
+#include "contexts_split.h"
+#include "prop_area.h"
+#include "prop_info.h"
+#include "system_property_globals.h"
+
+// We don't want to use new or malloc in properties (b/31659220), and since these classes are
+// small enough and don't have non-trivial constructors, it's easier to just statically declare
+// them than anything else.
+static ContextsSplit contexts_split;
+static ContextsPreSplit contexts_pre_split;
+static Contexts* contexts = nullptr;
+
+#define SERIAL_DIRTY(serial) ((serial)&1)
+#define SERIAL_VALUE_LEN(serial) ((serial) >> 24)
+
+static const char property_service_socket[] = "/dev/socket/" PROP_SERVICE_NAME;
+static const char* kServiceVersionPropertyName = "ro.property_service.version";
+
+// This is public because it was exposed in the NDK. As of 2017-01, ~60 apps reference this symbol.
+__BIONIC_WEAK_VARIABLE_FOR_NATIVE_BRIDGE
+prop_area* __system_property_area__ = nullptr;
+
+char property_filename[PROP_FILENAME_MAX] = PROP_FILENAME;
+size_t pa_size;
+
+class PropertyServiceConnection {
+ public:
+ PropertyServiceConnection() : last_error_(0) {
+ socket_ = ::socket(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0);
+ if (socket_ == -1) {
+ last_error_ = errno;
+ return;
+ }
+
+ const size_t namelen = strlen(property_service_socket);
+ sockaddr_un addr;
+ memset(&addr, 0, sizeof(addr));
+ strlcpy(addr.sun_path, property_service_socket, sizeof(addr.sun_path));
+ addr.sun_family = AF_LOCAL;
+ socklen_t alen = namelen + offsetof(sockaddr_un, sun_path) + 1;
+
+ if (TEMP_FAILURE_RETRY(connect(socket_, reinterpret_cast<sockaddr*>(&addr), alen)) == -1) {
+ last_error_ = errno;
+ close(socket_);
+ socket_ = -1;
+ }
+ }
+
+ bool IsValid() {
+ return socket_ != -1;
+ }
+
+ int GetLastError() {
+ return last_error_;
+ }
+
+ bool RecvInt32(int32_t* value) {
+ int result = TEMP_FAILURE_RETRY(recv(socket_, value, sizeof(*value), MSG_WAITALL));
+ return CheckSendRecvResult(result, sizeof(*value));
+ }
+
+ int socket() {
+ return socket_;
+ }
+
+ ~PropertyServiceConnection() {
+ if (socket_ != -1) {
+ close(socket_);
+ }
+ }
+
+ private:
+ bool CheckSendRecvResult(int result, int expected_len) {
+ if (result == -1) {
+ last_error_ = errno;
+ } else if (result != expected_len) {
+ last_error_ = -1;
+ } else {
+ last_error_ = 0;
+ }
+
+ return last_error_ == 0;
+ }
+
+ int socket_;
+ int last_error_;
+
+ friend class SocketWriter;
+};
+
+class SocketWriter {
+ public:
+ explicit SocketWriter(PropertyServiceConnection* connection)
+ : connection_(connection), iov_index_(0), uint_buf_index_(0) {
+ }
+
+ SocketWriter& WriteUint32(uint32_t value) {
+ CHECK(uint_buf_index_ < kUintBufSize);
+ CHECK(iov_index_ < kIovSize);
+ uint32_t* ptr = uint_buf_ + uint_buf_index_;
+ uint_buf_[uint_buf_index_++] = value;
+ iov_[iov_index_].iov_base = ptr;
+ iov_[iov_index_].iov_len = sizeof(*ptr);
+ ++iov_index_;
+ return *this;
+ }
+
+ SocketWriter& WriteString(const char* value) {
+ uint32_t valuelen = strlen(value);
+ WriteUint32(valuelen);
+ if (valuelen == 0) {
+ return *this;
+ }
+
+ CHECK(iov_index_ < kIovSize);
+ iov_[iov_index_].iov_base = const_cast<char*>(value);
+ iov_[iov_index_].iov_len = valuelen;
+ ++iov_index_;
+
+ return *this;
+ }
+
+ bool Send() {
+ if (!connection_->IsValid()) {
+ return false;
+ }
+
+ if (writev(connection_->socket(), iov_, iov_index_) == -1) {
+ connection_->last_error_ = errno;
+ return false;
+ }
+
+ iov_index_ = uint_buf_index_ = 0;
+ return true;
+ }
+
+ private:
+ static constexpr size_t kUintBufSize = 8;
+ static constexpr size_t kIovSize = 8;
+
+ PropertyServiceConnection* connection_;
+ iovec iov_[kIovSize];
+ size_t iov_index_;
+ uint32_t uint_buf_[kUintBufSize];
+ size_t uint_buf_index_;
+
+ DISALLOW_IMPLICIT_CONSTRUCTORS(SocketWriter);
+};
+
+struct prop_msg {
+ unsigned cmd;
+ char name[PROP_NAME_MAX];
+ char value[PROP_VALUE_MAX];
+};
+
+static int send_prop_msg(const prop_msg* msg) {
+ PropertyServiceConnection connection;
+ if (!connection.IsValid()) {
+ return connection.GetLastError();
+ }
+
+ int result = -1;
+ int s = connection.socket();
+
+ const int num_bytes = TEMP_FAILURE_RETRY(send(s, msg, sizeof(prop_msg), 0));
+ if (num_bytes == sizeof(prop_msg)) {
+ // We successfully wrote to the property server but now we
+ // wait for the property server to finish its work. It
+ // acknowledges its completion by closing the socket so we
+ // poll here (on nothing), waiting for the socket to close.
+ // If you 'adb shell setprop foo bar' you'll see the POLLHUP
+ // once the socket closes. Out of paranoia we cap our poll
+ // at 250 ms.
+ pollfd pollfds[1];
+ pollfds[0].fd = s;
+ pollfds[0].events = 0;
+ const int poll_result = TEMP_FAILURE_RETRY(poll(pollfds, 1, 250 /* ms */));
+ if (poll_result == 1 && (pollfds[0].revents & POLLHUP) != 0) {
+ result = 0;
+ } else {
+ // Ignore the timeout and treat it like a success anyway.
+ // The init process is single-threaded and its property
+ // service is sometimes slow to respond (perhaps it's off
+ // starting a child process or something) and thus this
+ // times out and the caller thinks it failed, even though
+ // it's still getting around to it. So we fake it here,
+ // mostly for ctl.* properties, but we do try and wait 250
+ // ms so callers who do read-after-write can reliably see
+ // what they've written. Most of the time.
+ // TODO: fix the system properties design.
+ async_safe_format_log(ANDROID_LOG_WARN, "libc",
+ "Property service has timed out while trying to set \"%s\" to \"%s\"",
+ msg->name, msg->value);
+ result = 0;
+ }
+ }
+
+ return result;
+}
+
+static bool is_dir(const char* pathname) {
+ struct stat info;
+ if (stat(pathname, &info) == -1) {
+ return false;
+ }
+ return S_ISDIR(info.st_mode);
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_properties_init() {
+ // This is called from __libc_init_common, and should leave errno at 0 (http://b/37248982).
+ ErrnoRestorer errno_restorer;
+
+ if (contexts != nullptr) {
+ contexts->ResetAccess();
+ return 0;
+ }
+ contexts = nullptr;
+ if (is_dir(property_filename)) {
+ if (!contexts_split.Initialize(false)) {
+ return -1;
+ }
+ contexts = &contexts_split;
+ } else {
+ if (!contexts_pre_split.Initialize(false)) {
+ return -1;
+ }
+ contexts = &contexts_pre_split;
+ }
+ return 0;
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_set_filename(const char* filename) {
+ size_t len = strlen(filename);
+ if (len >= sizeof(property_filename)) return -1;
+
+ strcpy(property_filename, filename);
+ return 0;
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_area_init() {
+ if (contexts != nullptr) {
+ contexts->FreeAndUnmap();
+ }
+ // We set this unconditionally as we want tests to continue on regardless of if this failed
+ // and property_service will abort on an error condition, so no harm done.
+ contexts = &contexts_split;
+ if (!contexts_split.Initialize(true)) {
+ return -1;
+ }
+ return 0;
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+uint32_t __system_property_area_serial() {
+ prop_area* pa = __system_property_area__;
+ if (!pa) {
+ return -1;
+ }
+ // Make sure this read fulfilled before __system_property_serial
+ return atomic_load_explicit(pa->serial(), memory_order_acquire);
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+const prop_info* __system_property_find(const char* name) {
+ if (contexts == nullptr) {
+ return nullptr;
+ }
+
+ prop_area* pa = contexts->GetPropAreaForName(name);
+ if (!pa) {
+ async_safe_format_log(ANDROID_LOG_ERROR, "libc", "Access denied finding property \"%s\"", name);
+ return nullptr;
+ }
+
+ return pa->find(name);
+}
+
+static bool is_read_only(const char* name) {
+ return strncmp(name, "ro.", 3) == 0;
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_read(const prop_info* pi, char* name, char* value) {
+ while (true) {
+ uint32_t serial = __system_property_serial(pi); // acquire semantics
+ size_t len = SERIAL_VALUE_LEN(serial);
+ memcpy(value, pi->value, len + 1);
+ // TODO: Fix the synchronization scheme here.
+ // There is no fully supported way to implement this kind
+ // of synchronization in C++11, since the memcpy races with
+ // updates to pi, and the data being accessed is not atomic.
+ // The following fence is unintuitive, but would be the
+ // correct one if memcpy used memory_order_relaxed atomic accesses.
+ // In practice it seems unlikely that the generated code would
+ // would be any different, so this should be OK.
+ atomic_thread_fence(memory_order_acquire);
+ if (serial == load_const_atomic(&(pi->serial), memory_order_relaxed)) {
+ if (name != nullptr) {
+ size_t namelen = strlcpy(name, pi->name, PROP_NAME_MAX);
+ if (namelen >= PROP_NAME_MAX) {
+ async_safe_format_log(ANDROID_LOG_ERROR, "libc",
+ "The property name length for \"%s\" is >= %d;"
+ " please use __system_property_read_callback"
+ " to read this property. (the name is truncated to \"%s\")",
+ pi->name, PROP_NAME_MAX - 1, name);
+ }
+ }
+ if (is_read_only(pi->name) && pi->is_long()) {
+ async_safe_format_log(
+ ANDROID_LOG_ERROR, "libc",
+ "The property \"%s\" has a value with length %zu that is too large for"
+ " __system_property_get()/__system_property_read(); use"
+ " __system_property_read_callback() instead.",
+ pi->name, strlen(pi->long_value()));
+ }
+ return len;
+ }
+ }
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+void __system_property_read_callback(const prop_info* pi,
+ void (*callback)(void* cookie, const char* name,
+ const char* value, uint32_t serial),
+ void* cookie) {
+ // Read only properties don't need to copy the value to a temporary buffer, since it can never
+ // change.
+ if (is_read_only(pi->name)) {
+ uint32_t serial = __system_property_serial(pi);
+ if (pi->is_long()) {
+ callback(cookie, pi->name, pi->long_value(), serial);
+ } else {
+ callback(cookie, pi->name, pi->value, serial);
+ }
+ return;
+ }
+
+ while (true) {
+ uint32_t serial = __system_property_serial(pi); // acquire semantics
+ size_t len = SERIAL_VALUE_LEN(serial);
+ char value_buf[len + 1];
+
+ memcpy(value_buf, pi->value, len);
+ value_buf[len] = '\0';
+
+ // TODO: see todo in __system_property_read function
+ atomic_thread_fence(memory_order_acquire);
+ if (serial == load_const_atomic(&(pi->serial), memory_order_relaxed)) {
+ callback(cookie, pi->name, value_buf, serial);
+ return;
+ }
+ }
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_get(const char* name, char* value) {
+ const prop_info* pi = __system_property_find(name);
+
+ if (pi != 0) {
+ return __system_property_read(pi, nullptr, value);
+ } else {
+ value[0] = 0;
+ return 0;
+ }
+}
+
+static constexpr uint32_t kProtocolVersion1 = 1;
+static constexpr uint32_t kProtocolVersion2 = 2; // current
+
+static atomic_uint_least32_t g_propservice_protocol_version = 0;
+
+static void detect_protocol_version() {
+ char value[PROP_VALUE_MAX];
+ if (__system_property_get(kServiceVersionPropertyName, value) == 0) {
+ g_propservice_protocol_version = kProtocolVersion1;
+ async_safe_format_log(ANDROID_LOG_WARN, "libc",
+ "Using old property service protocol (\"%s\" is not set)",
+ kServiceVersionPropertyName);
+ } else {
+ uint32_t version = static_cast<uint32_t>(atoll(value));
+ if (version >= kProtocolVersion2) {
+ g_propservice_protocol_version = kProtocolVersion2;
+ } else {
+ async_safe_format_log(ANDROID_LOG_WARN, "libc",
+ "Using old property service protocol (\"%s\"=\"%s\")",
+ kServiceVersionPropertyName, value);
+ g_propservice_protocol_version = kProtocolVersion1;
+ }
+ }
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_set(const char* key, const char* value) {
+ if (key == nullptr) return -1;
+ if (value == nullptr) value = "";
+
+ if (g_propservice_protocol_version == 0) {
+ detect_protocol_version();
+ }
+
+ if (g_propservice_protocol_version == kProtocolVersion1) {
+ // Old protocol does not support long names or values
+ if (strlen(key) >= PROP_NAME_MAX) return -1;
+ if (strlen(value) >= PROP_VALUE_MAX) return -1;
+
+ prop_msg msg;
+ memset(&msg, 0, sizeof msg);
+ msg.cmd = PROP_MSG_SETPROP;
+ strlcpy(msg.name, key, sizeof msg.name);
+ strlcpy(msg.value, value, sizeof msg.value);
+
+ return send_prop_msg(&msg);
+ } else {
+ // New protocol only allows long values for ro. properties only.
+ if (strlen(value) >= PROP_VALUE_MAX && !is_read_only(key)) return -1;
+ // Use proper protocol
+ PropertyServiceConnection connection;
+ if (!connection.IsValid()) {
+ errno = connection.GetLastError();
+ async_safe_format_log(
+ ANDROID_LOG_WARN, "libc",
+ "Unable to set property \"%s\" to \"%s\": connection failed; errno=%d (%s)", key, value,
+ errno, strerror(errno));
+ return -1;
+ }
+
+ SocketWriter writer(&connection);
+ if (!writer.WriteUint32(PROP_MSG_SETPROP2).WriteString(key).WriteString(value).Send()) {
+ errno = connection.GetLastError();
+ async_safe_format_log(ANDROID_LOG_WARN, "libc",
+ "Unable to set property \"%s\" to \"%s\": write failed; errno=%d (%s)",
+ key, value, errno, strerror(errno));
+ return -1;
+ }
+
+ int result = -1;
+ if (!connection.RecvInt32(&result)) {
+ errno = connection.GetLastError();
+ async_safe_format_log(ANDROID_LOG_WARN, "libc",
+ "Unable to set property \"%s\" to \"%s\": recv failed; errno=%d (%s)",
+ key, value, errno, strerror(errno));
+ return -1;
+ }
+
+ if (result != PROP_SUCCESS) {
+ async_safe_format_log(ANDROID_LOG_WARN, "libc",
+ "Unable to set property \"%s\" to \"%s\": error code: 0x%x", key, value,
+ result);
+ return -1;
+ }
+
+ return 0;
+ }
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_update(prop_info* pi, const char* value, unsigned int len) {
+ if (len >= PROP_VALUE_MAX) {
+ return -1;
+ }
+
+ prop_area* pa = __system_property_area__;
+
+ if (!pa) {
+ return -1;
+ }
+
+ uint32_t serial = atomic_load_explicit(&pi->serial, memory_order_relaxed);
+ serial |= 1;
+ atomic_store_explicit(&pi->serial, serial, memory_order_relaxed);
+ // The memcpy call here also races. Again pretend it
+ // used memory_order_relaxed atomics, and use the analogous
+ // counterintuitive fence.
+ atomic_thread_fence(memory_order_release);
+ strlcpy(pi->value, value, len + 1);
+
+ atomic_store_explicit(&pi->serial, (len << 24) | ((serial + 1) & 0xffffff), memory_order_release);
+ __futex_wake(&pi->serial, INT32_MAX);
+
+ atomic_store_explicit(pa->serial(), atomic_load_explicit(pa->serial(), memory_order_relaxed) + 1,
+ memory_order_release);
+ __futex_wake(pa->serial(), INT32_MAX);
+
+ return 0;
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_add(const char* name, unsigned int namelen, const char* value,
+ unsigned int valuelen) {
+ if (valuelen >= PROP_VALUE_MAX && !is_read_only(name)) {
+ return -1;
+ }
+
+ if (namelen < 1) {
+ return -1;
+ }
+
+ if (__system_property_area__ == nullptr || contexts == nullptr) {
+ return -1;
+ }
+
+ prop_area* pa = contexts->GetPropAreaForName(name);
+
+ if (!pa) {
+ async_safe_format_log(ANDROID_LOG_ERROR, "libc", "Access denied adding property \"%s\"", name);
+ return -1;
+ }
+
+ bool ret = pa->add(name, namelen, value, valuelen);
+ if (!ret) {
+ return -1;
+ }
+
+ // There is only a single mutator, but we want to make sure that
+ // updates are visible to a reader waiting for the update.
+ atomic_store_explicit(
+ __system_property_area__->serial(),
+ atomic_load_explicit(__system_property_area__->serial(), memory_order_relaxed) + 1,
+ memory_order_release);
+ __futex_wake(__system_property_area__->serial(), INT32_MAX);
+ return 0;
+}
+
+// Wait for non-locked serial, and retrieve it with acquire semantics.
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+uint32_t __system_property_serial(const prop_info* pi) {
+ uint32_t serial = load_const_atomic(&pi->serial, memory_order_acquire);
+ while (SERIAL_DIRTY(serial)) {
+ __futex_wait(const_cast<_Atomic(uint_least32_t)*>(&pi->serial), serial, nullptr);
+ serial = load_const_atomic(&pi->serial, memory_order_acquire);
+ }
+ return serial;
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+uint32_t __system_property_wait_any(uint32_t old_serial) {
+ uint32_t new_serial;
+ __system_property_wait(nullptr, old_serial, &new_serial, nullptr);
+ return new_serial;
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+bool __system_property_wait(const prop_info* pi, uint32_t old_serial, uint32_t* new_serial_ptr,
+ const timespec* relative_timeout) {
+ // Are we waiting on the global serial or a specific serial?
+ atomic_uint_least32_t* serial_ptr;
+ if (pi == nullptr) {
+ if (__system_property_area__ == nullptr) return -1;
+ serial_ptr = __system_property_area__->serial();
+ } else {
+ serial_ptr = const_cast<atomic_uint_least32_t*>(&pi->serial);
+ }
+
+ uint32_t new_serial;
+ do {
+ int rc;
+ if ((rc = __futex_wait(serial_ptr, old_serial, relative_timeout)) != 0 && rc == -ETIMEDOUT) {
+ return false;
+ }
+ new_serial = load_const_atomic(serial_ptr, memory_order_acquire);
+ } while (new_serial == old_serial);
+
+ *new_serial_ptr = new_serial;
+ return true;
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+const prop_info* __system_property_find_nth(unsigned n) {
+ struct find_nth {
+ const uint32_t sought;
+ uint32_t current;
+ const prop_info* result;
+
+ explicit find_nth(uint32_t n) : sought(n), current(0), result(nullptr) {
+ }
+ static void fn(const prop_info* pi, void* ptr) {
+ find_nth* self = reinterpret_cast<find_nth*>(ptr);
+ if (self->current++ == self->sought) self->result = pi;
+ }
+ } state(n);
+ __system_property_foreach(find_nth::fn, &state);
+ return state.result;
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_foreach(void (*propfn)(const prop_info* pi, void* cookie), void* cookie) {
+ if (contexts == nullptr) {
+ return -1;
+ }
+
+ contexts->ForEach(propfn, cookie);
+
+ return 0;
+}