Small native code reorganization

native/jni/systemproperties/Android.mk

@@ -10,6 +10,8 @@ LOCAL_SRC_FILES := \
 	prop_area.cpp \
 	prop_info.cpp \
 	system_properties.cpp \
+	system_property_api.cpp \
+	system_property_set.cpp \
 	property_info_parser.cpp
 
 include $(BUILD_STATIC_LIBRARY)

native/jni/systemproperties/include/_system_properties.h

@@ -0,0 +1,144 @@
+/*
+ * 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.
+ */
+
+#ifndef _INCLUDE_SYS__SYSTEM_PROPERTIES_H
+#define _INCLUDE_SYS__SYSTEM_PROPERTIES_H
+
+#include <sys/cdefs.h>
+#include <stdint.h>
+
+#ifndef _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
+#error you should #include <sys/system_properties.h> instead
+#endif
+
+//#include <sys/system_properties.h>
+#include "system_properties.h"
+
+__BEGIN_DECLS
+
+#define PROP_SERVICE_NAME "property_service"
+#define PROP_FILENAME "/dev/__properties__"
+
+#define PROP_MSG_SETPROP 1
+#define PROP_MSG_SETPROP2 0x00020001
+
+#define PROP_SUCCESS 0
+#define PROP_ERROR_READ_CMD 0x0004
+#define PROP_ERROR_READ_DATA 0x0008
+#define PROP_ERROR_READ_ONLY_PROPERTY 0x000B
+#define PROP_ERROR_INVALID_NAME 0x0010
+#define PROP_ERROR_INVALID_VALUE 0x0014
+#define PROP_ERROR_PERMISSION_DENIED 0x0018
+#define PROP_ERROR_INVALID_CMD 0x001B
+#define PROP_ERROR_HANDLE_CONTROL_MESSAGE 0x0020
+#define PROP_ERROR_SET_FAILED 0x0024
+
+/*
+** This was previously for testing, but now that SystemProperties is its own testable class,
+** there is never a reason to call this function and its implementation simply returns -1.
+*/
+int __system_property_set_filename(const char* __filename);
+
+/*
+** Initialize the area to be used to store properties.  Can
+** only be done by a single process that has write access to
+** the property area.
+*/
+int __system_property_area_init(void);
+
+/* Read the global serial number of the system properties
+**
+** Called to predict if a series of cached __system_property_find
+** objects will have seen __system_property_serial values change.
+** But also aids the converse, as changes in the global serial can
+** also be used to predict if a failed __system_property_find
+** could in-turn now find a new object; thus preventing the
+** cycles of effort to poll __system_property_find.
+**
+** Typically called at beginning of a cache cycle to signal if _any_ possible
+** changes have occurred since last. If there is, one may check each individual
+** __system_property_serial to confirm dirty, or __system_property_find
+** to check if the property now exists. If a call to __system_property_add
+** or __system_property_update has completed between two calls to
+** __system_property_area_serial then the second call will return a larger
+** value than the first call. Beware of race conditions as changes to the
+** properties are not atomic, the main value of this call is to determine
+** whether the expensive __system_property_find is worth retrying to see if
+** a property now exists.
+**
+** Returns the serial number on success, -1 on error.
+*/
+uint32_t __system_property_area_serial(void);
+
+/* Add a new system property.  Can only be done by a single
+** process that has write access to the property area, and
+** that process must handle sequencing to ensure the property
+** does not already exist and that only one property is added
+** or updated at a time.
+**
+** Returns 0 on success, -1 if the property area is full.
+*/
+int __system_property_add(const char* __name, unsigned int __name_length, const char* __value, unsigned int __value_length);
+
+/* Delete a system property. Added in resetprop
+**
+** Returns 0 on success, -1 if the property area is full.
+*/
+int __system_property_del(const char *__name);
+
+/* Update the value of a system property returned by
+** __system_property_find.  Can only be done by a single process
+** that has write access to the property area, and that process
+** must handle sequencing to ensure that only one property is
+** updated at a time.
+**
+** Returns 0 on success, -1 if the parameters are incorrect.
+*/
+int __system_property_update(prop_info* __pi, const char* __value, unsigned int __value_length);
+
+/* Read the serial number of a system property returned by
+** __system_property_find.
+**
+** Returns the serial number on success, -1 on error.
+*/
+uint32_t __system_property_serial(const prop_info* __pi);
+
+/* Initialize the system properties area in read only mode.
+ * Should be done by all processes that need to read system
+ * properties.
+ *
+ * Returns 0 on success, -1 otherwise.
+ */
+int __system_properties_init(void);
+
+/* Deprecated: use __system_property_wait instead. */
+uint32_t __system_property_wait_any(uint32_t __old_serial);
+
+__END_DECLS
+
+#endif

native/jni/systemproperties/include/hacks.h

@@ -1,14 +0,0 @@
-#pragma once
-
-#include <stdio.h>
-#include <syscall.h>
-
-#ifndef PR_SET_VMA
-#define PR_SET_VMA 0x53564d41
-#endif
-#ifndef PR_SET_VMA_ANON_NAME
-#define PR_SET_VMA_ANON_NAME 0
-#endif
-#define getline __getline
-#define fsetxattr(...) syscall(__NR_fsetxattr, __VA_ARGS__)
-ssize_t __getline(char **, size_t *, FILE *);

native/jni/systemproperties/include/private/bionic_defs.h

@@ -0,0 +1,39 @@
+/*
+ * 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.
+ */
+
+#ifndef __BIONIC_PRIVATE_BIONIC_DEFS_H_
+#define __BIONIC_PRIVATE_BIONIC_DEFS_H_
+
+/*
+ * This label is used to mark libc/libdl symbols that may need to be replaced
+ * by native bridge implementation.
+ */
+#define __BIONIC_WEAK_FOR_NATIVE_BRIDGE __attribute__((__weak__, __noinline__))
+#define __BIONIC_WEAK_VARIABLE_FOR_NATIVE_BRIDGE __attribute__((__weak__))
+
+#endif /* __BIONIC_PRIVATE_BIONIC_DEFS_H_ */

native/jni/systemproperties/include/private/hacks.h

@@ -0,0 +1,35 @@
+#pragma once
+
+#include <stdio.h>
+#include <syscall.h>
+
+// Missing defines
+#ifndef PR_SET_VMA
+#define PR_SET_VMA 0x53564d41
+#endif
+#ifndef PR_SET_VMA_ANON_NAME
+#define PR_SET_VMA_ANON_NAME 0
+#endif
+
+// Missing functions
+#define fsetxattr(...) syscall(__NR_fsetxattr, __VA_ARGS__)
+#define getline __getline
+ssize_t __getline(char **, size_t *, FILE *);
+
+// Rename symbols
+#pragma redefine_extname __system_property_set _system_property_set2
+#pragma redefine_extname __system_property_find _system_property_find2
+#pragma redefine_extname __system_property_read_callback _system_property_read_callback2
+#pragma redefine_extname __system_property_foreach __system_property_foreach2
+#pragma redefine_extname __system_property_wait __system_property_wait2
+#pragma redefine_extname __system_property_read __system_property_read2
+#pragma redefine_extname __system_property_get __system_property_get2
+#pragma redefine_extname __system_property_find_nth __system_property_find_nth2
+#pragma redefine_extname __system_property_set_filename __system_property_set_filename2
+#pragma redefine_extname __system_property_area_init __system_property_area_init2
+#pragma redefine_extname __system_property_area_serial __system_property_area_serial2
+#pragma redefine_extname __system_property_add __system_property_add2
+#pragma redefine_extname __system_property_update __system_property_update2
+#pragma redefine_extname __system_property_serial __system_property_serial2
+#pragma redefine_extname __system_properties_init __system_properties_init2
+#pragma redefine_extname __system_property_wait_any __system_property_wait_any2

native/jni/systemproperties/include/system_properties.h

@@ -0,0 +1,101 @@
+/*
+ * 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.
+ */
+
+#ifndef _INCLUDE_SYS_SYSTEM_PROPERTIES_H
+#define _INCLUDE_SYS_SYSTEM_PROPERTIES_H
+
+#include <sys/cdefs.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "private/hacks.h"
+
+__BEGIN_DECLS
+
+typedef struct prop_info prop_info;
+
+#define PROP_VALUE_MAX  92
+
+/*
+ * Sets system property `name` to `value`, creating the system property if it doesn't already exist.
+ */
+int __system_property_set(const char* __name, const char* __value) __INTRODUCED_IN(12);
+
+/*
+ * Returns a `prop_info` corresponding system property `name`, or nullptr if it doesn't exist.
+ * Use __system_property_read_callback to query the current value.
+ *
+ * Property lookup is expensive, so it can be useful to cache the result of this function.
+ */
+const prop_info* __system_property_find(const char* __name);
+
+/*
+ * Calls `callback` with a consistent trio of name, value, and serial number for property `pi`.
+ */
+void __system_property_read_callback(const prop_info* __pi,
+    void (*__callback)(void* __cookie, const char* __name, const char* __value, uint32_t __serial),
+    void* __cookie) __INTRODUCED_IN(26);
+
+/*
+ * Passes a `prop_info` for each system property to the provided
+ * callback.  Use __system_property_read_callback() to read the value.
+ *
+ * This method is for inspecting and debugging the property system, and not generally useful.
+ */
+int __system_property_foreach(void (*__callback)(const prop_info* __pi, void* __cookie), void* __cookie)
+  __INTRODUCED_IN(19);
+
+/*
+ * Waits for the specific system property identified by `pi` to be updated
+ * past `old_serial`. Waits no longer than `relative_timeout`, or forever
+ * if `relaive_timeout` is null.
+ *
+ * If `pi` is null, waits for the global serial number instead.
+ *
+ * If you don't know the current serial, use 0.
+ *
+ * Returns true and updates `*new_serial_ptr` on success, or false if the call
+ * timed out.
+ */
+struct timespec;
+bool __system_property_wait(const prop_info* __pi, uint32_t __old_serial, uint32_t* __new_serial_ptr, const struct timespec* __relative_timeout)
+    __INTRODUCED_IN(26);
+
+/* Deprecated. In Android O and above, there's no limit on property name length. */
+#define PROP_NAME_MAX   32
+/* Deprecated. Use __system_property_read_callback instead. */
+int __system_property_read(const prop_info* __pi, char* __name, char* __value);
+/* Deprecated. Use __system_property_read_callback instead. */
+int __system_property_get(const char* __name, char* __value);
+/* Deprecated. Use __system_property_foreach instead. */
+const prop_info* __system_property_find_nth(unsigned __n);
+
+__END_DECLS
+
+#endif

native/jni/systemproperties/include/system_properties/prop_info.h

@@ -30,10 +30,10 @@
 
 #include <stdatomic.h>
 #include <stdint.h>
-#include <sys/system_properties.h>
+//#include <sys/system_properties.h>
+#include "../system_properties.h"
 
 #include "private/bionic_macros.h"
-#include "hacks.h"
 
 // The C11 standard doesn't allow atomic loads from const fields,
 // though C++11 does.  Fudge it until standards get straightened out.

native/jni/systemproperties/include/system_properties/system_properties.h

@@ -30,7 +30,8 @@
 
 #include <stdint.h>
 #include <sys/param.h>
-#include <sys/system_properties.h>
+//#include <sys/system_properties.h>
+#include "../system_properties.h"
 
 #include "contexts.h"
 #include "contexts_pre_split.h"

native/jni/systemproperties/system_property_api.cpp

@@ -0,0 +1,131 @@
+/*
+ * 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.
+ */
+
+#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
+//#include <sys/_system_properties.h>
+#include <_system_properties.h>
+
+#include <system_properties/prop_area.h>
+#include <system_properties/system_properties.h>
+
+#include "private/bionic_defs.h"
+
+static SystemProperties system_properties;
+static_assert(__is_trivially_constructible(SystemProperties),
+              "System Properties must be trivially constructable");
+
+// This is public because it was exposed in the NDK. As of 2017-01, ~60 apps reference this symbol.
+// It is set to nullptr and never modified.
+__BIONIC_WEAK_VARIABLE_FOR_NATIVE_BRIDGE
+prop_area* __system_property_area__ = nullptr;
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_properties_init() {
+  return system_properties.Init(PROP_FILENAME) ? 0 : -1;
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_set_filename(const char*) {
+  return -1;
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_area_init() {
+  bool fsetxattr_failed = false;
+  return system_properties.AreaInit(PROP_FILENAME, &fsetxattr_failed) && !fsetxattr_failed ? 0 : -1;
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+uint32_t __system_property_area_serial() {
+  return system_properties.AreaSerial();
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+const prop_info* __system_property_find(const char* name) {
+  return system_properties.Find(name);
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_read(const prop_info* pi, char* name, char* value) {
+  return system_properties.Read(pi, name, value);
+}
+
+__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) {
+  return system_properties.ReadCallback(pi, callback, cookie);
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_get(const char* name, char* value) {
+  return system_properties.Get(name, value);
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_update(prop_info* pi, const char* value, unsigned int len) {
+  return system_properties.Update(pi, value, len);
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_add(const char* name, unsigned int namelen, const char* value,
+                          unsigned int valuelen) {
+  return system_properties.Add(name, namelen, value, valuelen);
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_del(const char* name) {
+  return system_properties.Delete(name);
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+uint32_t __system_property_serial(const prop_info* pi) {
+  return system_properties.Serial(pi);
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+uint32_t __system_property_wait_any(uint32_t old_serial) {
+  return system_properties.WaitAny(old_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) {
+  return system_properties.Wait(pi, old_serial, new_serial_ptr, relative_timeout);
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+const prop_info* __system_property_find_nth(unsigned n) {
+  return system_properties.FindNth(n);
+}
+
+__BIONIC_WEAK_FOR_NATIVE_BRIDGE
+int __system_property_foreach(void (*propfn)(const prop_info* pi, void* cookie), void* cookie) {
+  return system_properties.Foreach(propfn, cookie);
+}

native/jni/systemproperties/system_property_set.cpp

@@ -0,0 +1,317 @@
+/*
+ * 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 <_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_;
+
+  BIONIC_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;
+  }
+}