Android添加系统属性之SystemProperties

最新推荐文章于 2025-07-04 13:36:01 发布

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本文介绍了Android系统中添加SystemProperty属性的方法，包括其命名规则和权限限制。SystemProperty属性受系统严格控制，如ro和persist开头的属性代表只读和持久化。权限涉及到AID_SYSTEM、AID_MEDIA和AID_RADIO等，而添加自定义属性通常需要在system.prop文件中进行。

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android添加系统属性有两种，一种是System.Setting类的属性，这种属性其实是存在SettingProvider数据库中的，也就是framework/base/packages/settingprovider/src/com/android/providers/settings/DatabaseHelper.java所load的那些，添加这种类型的系统属性下篇再写。现在先写下如何添加另外一种，也就是SystemProperty属性，SystemProperty属性是被系统严格限制的，首先是它的命名，必须以system/core/init/Property_services.c中定义的

/* White list of permissions for setting property services. */
struct {
    const char *prefix;
    unsigned int uid;
    unsigned int gid;
} property_perms[] = {
    { "net.rmnet0.",      AID_RADIO,    0 },
    { "net.gprs.",        AID_RADIO,    0 },
    { "net.ppp",          AID_RADIO,    0 },
    { "net.qmi",          AID_RADIO,    0 },
    { "net.lte",          AID_RADIO,    0 },
    { "net.cdma",         AID_RADIO,    0 },
    { "ril.",             AID_RADIO,    0 },
    { "mux.",             AID_RADIO,    0 },
    { "gsm.",             AID_RADIO,    0 },
    { "persist.radio",    AID_RADIO,    0 },
    { "net.dns",          AID_RADIO,    0 },
    { "sys.usb.config",   AID_RADIO,    0 },
    { "net.",             AID_SYSTEM,   0 },
    { "dev.",             AID_SYSTEM,   0 },
    { "runtime.",         AID_SYSTEM,   0 },
    { "hw.",              AID_SYSTEM,   0 },
    { "sys.",             AID_SYSTEM,   0 },
    { "service.",         AID_SYSTEM,   0 },
    { "wlan.",            AID_SYSTEM,   0 },
    { "dhcp.",            AID_SYSTEM,   0 },
    { "dhcp.",            AID_DHCP,     0 },
    { "debug.",           AID_SHELL,    0 },
    { "log.",             AID_SHELL,    0 },
    { "service.adb.root", AID_SHELL,    0 },
    { "service.adb.tcp.port", AID_SHELL,    0 },
    { "persist.sys.",     AID_SYSTEM,   0 },
    { "persist.service.", AID_SYSTEM,   0 },
    { "persist.security.", AID_SYSTEM,   0 },
    { "mediatek.",        AID_RADIO,    0 },
    { "gps.",             AID_GPS,   AID_SYSTEM },
    { "cdma.",            AID_RADIO,    0 },
    { "af.",              AID_MEDIA,   0 },
    { "a2dp.",            AID_MEDIA,   0 },
    { "streamin.",        AID_MEDIA,   0 },
    { "streamout.",       AID_MEDIA,   0 },
    { NULL, 0, 0 }
};其中ro开头表示只读属性，presist开头的表示可存储，也就是以文件的形式保存的，开关机不会失效的。其中AID_SYSTEM,AID_MEDIA，AID_RADIO等代表的权限，也就是程序签名以及所在的进程ID，比如系统的Settings所拥有的权限android:sharedUserId="android.uid.system“以及Android.mk中的平台签名LOCAL_CERTIFICATE := platform使得Settings具有system权限，对应的AID_SYSTEM类型。