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system_property_set.cpp
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system_property_set.cpp
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/*
* Copyright (C) 2017 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 <poll.h>
#include <stdatomic.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/un.h>
#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
//#include <sys/_system_properties.h>
#include "private/_system_properties.h"
#include <unistd.h>
#include <async_safe/log.h>
#include "private/bionic_defs.h"
#include "private/bionic_macros.h"
static const char property_service_socket[] = "/dev/socket/" PROP_SERVICE_NAME;
static const char* kServiceVersionPropertyName = "ro.property_service.version";
#define CHECK(x) /* NOP */
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 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 && strncmp(key, "ro.", 3) != 0) 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;
}
}