1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#pragma once
30
31#include <stdint.h>
32#include <sys/param.h>
33#include <sys/system_properties.h>
34
35#include "contexts.h"
36#include "contexts_pre_split.h"
37#include "contexts_serialized.h"
38#include "contexts_split.h"
39
40constexpr int PROP_FILENAME_MAX = 1024;
41
42class SystemProperties {
43 public:
44  friend struct LocalPropertyTestState;
45  friend class SystemPropertiesTest;
46  // Note that system properties are initialized before libc calls static initializers, so
47  // doing any initialization in this constructor is an error.  Even a Constructor that zero
48  // initializes this class will clobber the previous property initialization.
49  // We rely on the static SystemProperties in libc to be placed in .bss and zero initialized.
50  SystemProperties() = default;
51  // Special constructor for testing that also zero initializes the important members.
52  explicit SystemProperties(bool initialized) : initialized_(initialized) {
53  }
54
55  DISALLOW_COPY_AND_ASSIGN(SystemProperties);
56
57  bool Init(const char* filename);
58  bool AreaInit(const char* filename, bool* fsetxattr_failed);
59  uint32_t AreaSerial();
60  const prop_info* Find(const char* name);
61  int Read(const prop_info* pi, char* name, char* value);
62  void ReadCallback(const prop_info* pi,
63                    void (*callback)(void* cookie, const char* name, const char* value,
64                                     uint32_t serial),
65                    void* cookie);
66  int Get(const char* name, char* value);
67  int Update(prop_info* pi, const char* value, unsigned int len);
68  int Add(const char* name, unsigned int namelen, const char* value, unsigned int valuelen);
69  uint32_t Serial(const prop_info* pi);
70  uint32_t WaitAny(uint32_t old_serial);
71  bool Wait(const prop_info* pi, uint32_t old_serial, uint32_t* new_serial_ptr,
72            const timespec* relative_timeout);
73  const prop_info* FindNth(unsigned n);
74  int Foreach(void (*propfn)(const prop_info* pi, void* cookie), void* cookie);
75
76 private:
77  // We don't want to use new or malloc in properties (b/31659220), and we don't want to waste a
78  // full page by using mmap(), so we set aside enough space to create any context of the three
79  // contexts.
80  static constexpr size_t kMaxContextsAlign =
81      MAX(alignof(ContextsSerialized), MAX(alignof(ContextsSplit), alignof(ContextsPreSplit)));
82  static constexpr size_t kMaxContextsSize =
83      MAX(sizeof(ContextsSerialized), MAX(sizeof(ContextsSplit), sizeof(ContextsPreSplit)));
84  alignas(kMaxContextsAlign) char contexts_data_[kMaxContextsSize];
85  Contexts* contexts_;
86
87  bool initialized_;
88  char property_filename_[PROP_FILENAME_MAX];
89};
90