关键字： android, settings, cmd

20180822 tjy

转载请注明出处

Android 中有一个可执行文件settings，可以使得调试变得方便。

查看settings的代码，会有其他额外发现。

文件位置

device-name:/system/bin # ls -l settings

ls -l settings

-rwxr-xr-x 1 root shell 35 2018-08-03 04:17 settings

device-name:/system/bin #

settings用法

device-name:/ # settings

settings

Settings provider (settings) commands:

help

Print this help text.

get [--user | current] NAMESPACE KEY

Retrieve the current value of KEY.

put [--user | current] NAMESPACE KEY VALUE [TAG] [default]

Change the contents of KEY to VALUE.

TAG to associate with the setting.

{default} to set as the default, case-insensitive only for global/secure namespace

delete NAMESPACE KEY

Delete the entry for KEY.

reset [--user | current] NAMESPACE {PACKAGE_NAME | RESET_MODE}

Reset the global/secure table for a package with mode.

RESET_MODE is one of {untrusted_defaults, untrusted_clear, trusted_defaults}, case-insensitive

list NAMESPACE

Print all defined keys.

NAMESPACE is one of {system, secure, global}, case-insensitive

settings list命令

device-name:/ # settings list global

settings list global

adb_enabled=1

add_users_when_locked=0

airplane_mode_on=0

airplane_mode_radios=cell,bluetooth,wifi,nfc,wimax

airplane_mode_toggleable_radios=bluetooth,wifi,nfc

assisted_gps_enabled=1

att_wifi_call_enable=0

audio_safe_volume_state=3

auto_time=1

auto_time_zone=1

bluetooth_disabled_profiles=0

bluetooth_on=0

boot_count=5

call_auto_retry=0

captive_portal_mode=1

car_dock_sound=/system/media/audio/ui/Dock.ogg

car_undock_sound=/system/media/audio/ui/Undock.ogg

cdma_cell_broadcast_sms=1

data_roaming0=1

data_roaming=1

default_install_location=0

default_restrict_background_data=0

desk_dock_sound=/system/media/audio/ui/Dock.ogg

desk_undock_sound=/system/media/audio/ui/Undock.ogg

development_settings_enabled=1

device_provisioned=1

dock_audio_media_enabled=1

dock_sounds_enabled=0

dock_sounds_enabled_when_accessbility=0

emergency_affordance_needed=0

emergency_tone=0

heads_up_notifications_enabled=1

lock_sound=/system/media/audio/ui/Lock.ogg

low_battery_sound=/system/media/audio/ui/LowBattery.ogg

low_battery_sound_timeout=0

mobile_data0=1

mobile_data=1

mobile_data_always_on=0

mode_ringer=2

netstats_enabled=1

network_recommendations_enabled=0

package_verifier_enable=1

power_sounds_enabled=1

preferred_network_mode=10

set_install_location=0

stay_on_while_plugged_in=0

subscription_mode=0

theater_mode_on=0

trusted_sound=/system/media/audio/ui/Trusted.ogg

unlock_sound=/system/media/audio/ui/Unlock.ogg

usb_mass_storage_enabled=1

verifier_verify_adb_installs=0

volte_vt_enabled=1

wfc_ims_enabled=0

wfc_ims_mode=1

wifi_display_on=0

wifi_max_dhcp_retry_count=9

wifi_networks_available_notification_on=1

wifi_on=0

wifi_scan_always_enabled=0

wifi_sleep_policy=2

wifi_wakeup_available=0

wifi_wakeup_enabled=1

wireless_charging_started_sound=/system/media/audio/ui/WirelessChargingStarted.ogg

settings put和get

device-name:/ # settings get global bluetooth_on

settings get global bluetooth_on

0

device-name:/ # settings put global bluetooth_on 1

settings put global bluetooth_on 1

device-name:/ #

代码位置在frameworks/base/cmds/settings/settings，打开这个文件，发现它是一个shell，调用了cmd命令，cmd命令又在哪里呢？

//from http://androidxref.com/8.1.0_r33/xref/frameworks/base/cmds/settings/settings

#!/system/bin/sh

cmd settings "$@"

在frameworks/native/cmds/cmd/cmd.cpp中，代码如下。

cmd通过IServiceManager去实现操作。

通过看代码，cmd -l可以把service都列出来。

cmd settings是通过调用 service settings中的方法来完成的。

//from http://androidxref.com/8.1.0_r33/xref/frameworks/native/cmds/cmd/cmd.cpp

int main(int argc, char* const argv[])

{

signal(SIGPIPE, SIG_IGN);

sp proc = ProcessState::self();

// setThreadPoolMaxThreadCount(0) actually tells the kernel it's

// not allowed to spawn any additional threads, but we still spawn

// a binder thread from userspace when we call startThreadPool().

// This is safe because we only have 2 callbacks, neither of which

// block.

// See b/36066697 for rationale

proc->setThreadPoolMaxThreadCount(0);

proc->startThreadPool();

sp sm = defaultServiceManager();

fflush(stdout);

if (sm == NULL) {

ALOGW("Unable to get default service manager!");

aerr << "cmd: Unable to get default service manager!" << endl;

return 20;

}

if (argc == 1) {

aerr << "cmd: No service specified; use -l to list all services" << endl;

return 20;

}

if ((argc == 2) && (strcmp(argv[1], "-l") == 0)) {

Vector services = sm->listServices();

services.sort(sort_func);

aout << "Currently running services:" << endl;

for (size_t i=0; i

sp service = sm->checkService(services[i]);

if (service != NULL) {

aout << " " << services[i] << endl;

}

}

return 0;

}

Vector args;

for (int i=2; i

args.add(String16(argv[i]));

}

String16 cmd = String16(argv[1]);

sp service = sm->checkService(cmd);

if (service == NULL) {

ALOGW("Can't find service %s", argv[1]);

aerr << "cmd: Can't find service: " << argv[1] << endl;

return 20;

}

sp cb = new MyShellCallback();

sp result = new MyResultReceiver();

#if DEBUG

ALOGD("cmd: Invoking %s in=%d, out=%d, err=%d", argv[1], STDIN_FILENO, STDOUT_FILENO,

STDERR_FILENO);

#endif

// TODO: block until a result is returned to MyResultReceiver.

status_t err = IBinder::shellCommand(service, STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO, args,

cb, result);

if (err < 0) {

const char* errstr;

switch (err) {

case BAD_TYPE: errstr = "Bad type"; break;

case FAILED_TRANSACTION: errstr = "Failed transaction"; break;

case FDS_NOT_ALLOWED: errstr = "File descriptors not allowed"; break;

case UNEXPECTED_NULL: errstr = "Unexpected null"; break;

default: errstr = strerror(-err); break;

}

ALOGW("Failure calling service %s: %s (%d)", argv[1], errstr, -err);

aout << "cmd: Failure calling service " << argv[1] << ": " << errstr << " ("

<< (-err) << ")" << endl;

return err;

}

cb->mActive = false;

status_t res = result->waitForResult();

#if DEBUG

ALOGD("result=%d", (int)res);

#endif

return res;

}

继续追一下IBinder::shellCommand代码，定义在frameworks/native/libs/binder/Binder.cpp。

后续补充Binder的逻辑。

//from http://androidxref.com/8.1.0_r33/xref/frameworks/native/libs/binder/Binder.cpp#65

status_t IBinder::shellCommand(const sp& target, int in, int out, int err,

Vector& args, const sp& callback,

const sp& resultReceiver)

{

Parcel send;

Parcel reply;

send.writeFileDescriptor(in);

send.writeFileDescriptor(out);

send.writeFileDescriptor(err);

const size_t numArgs = args.size();

send.writeInt32(numArgs);

for (size_t i = 0; i < numArgs; i++) {

send.writeString16(args[i]);

}

send.writeStrongBinder(callback != NULL ? IInterface::asBinder(callback) : NULL);

send.writeStrongBinder(resultReceiver != NULL ? IInterface::asBinder(resultReceiver) : NULL);

return target->transact(SHELL_COMMAND_TRANSACTION, send, &reply);

}