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 40 constexpr int PROP_FILENAME_MAX = 1024; 41 42 class 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. SystemProperties(bool initialized)52 explicit SystemProperties(bool initialized) : initialized_(initialized) { 53 } 54 55 BIONIC_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