5cf32de7a0
Move the implementation of writing to the system property area
from init to bionic, next to the reader implementation. This
will allow full property testing to be added to bionic tests.
Add new accessor and waiting functions to hide the implementation
from watchprops and various bionic users.
Also hide some of the implementation details of the property area
from init by moving them into _system_properties.h, and other details
from everybody by moving them into system_properties.h.
(cherry picked from commit dc1038b790)
Change-Id: I192d3825ee276c5047bc751039fe6cfe226a7cca
142 lines
4.9 KiB
C
142 lines
4.9 KiB
C
/*
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* Copyright (C) 2008 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef _INCLUDE_SYS__SYSTEM_PROPERTIES_H
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#define _INCLUDE_SYS__SYSTEM_PROPERTIES_H
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#ifndef _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
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#error you should #include <sys/system_properties.h> instead
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#else
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#include <sys/system_properties.h>
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typedef struct prop_msg prop_msg;
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#define PROP_AREA_MAGIC 0x504f5250
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#define PROP_AREA_VERSION 0x45434f76
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#define PROP_SERVICE_NAME "property_service"
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#define PROP_FILENAME "/dev/__properties__"
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/* (8 header words + 247 toc words) = 1020 bytes */
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/* 1024 bytes header and toc + 247 prop_infos @ 128 bytes = 32640 bytes */
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#define PA_COUNT_MAX 247
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#define PA_INFO_START 1024
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#define PA_SIZE 32768
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#define TOC_NAME_LEN(toc) ((toc) >> 24)
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#define TOC_TO_INFO(area, toc) ((prop_info*) (((char*) area) + ((toc) & 0xFFFFFF)))
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#define SERIAL_VALUE_LEN(serial) ((serial) >> 24)
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#define SERIAL_DIRTY(serial) ((serial) & 1)
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__BEGIN_DECLS
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struct prop_msg
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{
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unsigned cmd;
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char name[PROP_NAME_MAX];
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char value[PROP_VALUE_MAX];
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};
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#define PROP_MSG_SETPROP 1
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/*
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** Rules:
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**
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** - there is only one writer, but many readers
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** - prop_area.count will never decrease in value
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** - once allocated, a prop_info's name will not change
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** - once allocated, a prop_info's offset will not change
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** - reading a value requires the following steps
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** 1. serial = pi->serial
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** 2. if SERIAL_DIRTY(serial), wait*, then goto 1
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** 3. memcpy(local, pi->value, SERIAL_VALUE_LEN(serial) + 1)
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** 4. if pi->serial != serial, goto 2
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**
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** - writing a value requires the following steps
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** 1. pi->serial = pi->serial | 1
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** 2. memcpy(pi->value, local_value, value_len)
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** 3. pi->serial = (value_len << 24) | ((pi->serial + 1) & 0xffffff)
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**
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** Improvements:
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** - maintain the toc sorted by pi->name to allow lookup
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** by binary search
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**
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*/
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#define PROP_PATH_RAMDISK_DEFAULT "/default.prop"
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#define PROP_PATH_SYSTEM_BUILD "/system/build.prop"
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#define PROP_PATH_SYSTEM_DEFAULT "/system/default.prop"
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#define PROP_PATH_LOCAL_OVERRIDE "/data/local.prop"
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#define PROP_PATH_FACTORY "/factory/factory.prop"
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/*
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** Initialize the area to be used to store properties. Can
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** only be done by a single process that has write access to
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** the property area.
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*/
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void __system_property_area_init(void *data);
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/* Add a new system property. Can only be done by a single
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** process that has write access to the property area, and
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** that process must handle sequencing to ensure the property
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** does not already exist and that only one property is added
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** or updated at a time.
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**
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** Returns 0 on success, -1 if the property area is full.
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*/
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int __system_property_add(const char *name, unsigned int namelen,
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const char *value, unsigned int valuelen);
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/* Update the value of a system property returned by
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** __system_property_find. Can only be done by a single process
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** that has write access to the property area, and that process
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** must handle sequencing to ensure that only one property is
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** updated at a time.
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**
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** Returns 0 on success, -1 if the parameters are incorrect.
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*/
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int __system_property_update(prop_info *pi, const char *value, unsigned int len);
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/* Read the serial number of a system property returned by
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** __system_property_find.
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**
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** Returns the serial number on success, -1 on error.
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*/
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unsigned int __system_property_serial(const prop_info *pi);
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/* Wait for any system property to be updated. Caller must pass
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** in 0 the first time, and the previous return value on each
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** successive call. */
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unsigned int __system_property_wait_any(unsigned int serial);
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__END_DECLS
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#endif
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#endif
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