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Commit 38bf5146 authored by Greg Hackmann's avatar Greg Hackmann
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Move time setting code from SystemClock to AlarmManagerService 



On devices using /dev/rtc instead of /dev/alarm, updating the
time-of-day clock and RTC are separate syscalls.  Hence the clock and
RTC could be left in inconsistent states if two threads called
SystemClock.setCurrentTimeMillis() simultaneously.

By moving this code into AlarmManagerService, we can put a global lock
around AlarmManagerService.setTime() and prevent the race condition.

Note that access to SystemClock.setCurrentTimeMillis() is now gated by
android.permission.SET_TIME, where before it was gated by filesystem
permissions (i.e., could the process write to /dev/alarm or /dev/rtc).

Change-Id: Ia34899a4cde983656305fd2ef466dfe908ed23c8
Signed-off-by: default avatarGreg Hackmann <ghackmann@google.com>
parent 05cebdc2

core/java/android/app/IAlarmManager.aidl

+1 −1
Original line number Diff line number Diff line
@@ -28,7 +28,7 @@ interface IAlarmManager { 
	/** windowLength == 0 means exact; windowLength < 0 means the let the OS decide */

    void set(int type, long triggerAtTime, long windowLength,

            long interval, in PendingIntent operation, in WorkSource workSource);

    void setTime(long millis);

    boolean setTime(long millis);

    void setTimeZone(String zone);

    void remove(in PendingIntent operation);

}

core/java/android/os/SystemClock.java

+22 −1
Original line number Diff line number Diff line
@@ -16,6 +16,9 @@ 


package android.os;



import android.app.IAlarmManager;

import android.content.Context;

import android.util.Slog;



/**

 * Core timekeeping facilities.
@@ -89,6 +92,8 @@ package android.os; 
 * </ul>

 */

public final class SystemClock {

    private static final String TAG = "SystemClock";



    /**

     * This class is uninstantiable.

     */
@@ -134,7 +139,23 @@ public final class SystemClock { 
     *

     * @return if the clock was successfully set to the specified time.

     */

    native public static boolean setCurrentTimeMillis(long millis);

    public static boolean setCurrentTimeMillis(long millis) {

        IBinder b = ServiceManager.getService(Context.ALARM_SERVICE);

        IAlarmManager mgr = IAlarmManager.Stub.asInterface(b);

        if (mgr == null) {

            return false;

        }



        try {

            return mgr.setTime(millis);

        } catch (RemoteException e) {

            Slog.e(TAG, "Unable to set RTC", e);

        } catch (SecurityException e) {

            Slog.e(TAG, "Unable to set RTC", e);

        }



        return false;

    }



    /**

     * Returns milliseconds since boot, not counting time spent in deep sleep.

core/jni/android_os_SystemClock.cpp

+0 −112
Original line number Diff line number Diff line
@@ -19,13 +19,6 @@ 
 * System clock functions.

 */



#ifdef HAVE_ANDROID_OS

#include <linux/ioctl.h>

#include <linux/rtc.h>

#include <utils/Atomic.h>

#include <linux/android_alarm.h>

#endif



#include <sys/time.h>

#include <limits.h>

#include <fcntl.h>
@@ -43,109 +36,6 @@ 


namespace android {



static int setCurrentTimeMillisAlarmDriver(struct timeval *tv)

{

    struct timespec ts;

    int fd;

    int res;



    fd = open("/dev/alarm", O_RDWR);

    if(fd < 0) {

        ALOGV("Unable to open alarm driver: %s\n", strerror(errno));

        return -1;

    }

    ts.tv_sec = tv->tv_sec;

    ts.tv_nsec = tv->tv_usec * 1000;

    res = ioctl(fd, ANDROID_ALARM_SET_RTC, &ts);

    if (res < 0)

        ALOGV("ANDROID_ALARM_SET_RTC ioctl failed: %s\n", strerror(errno));

    close(fd);

    return res;

}



static int setCurrentTimeMillisRtc(struct timeval *tv)

{

    struct rtc_time rtc;

    struct tm tm, *gmtime_res;

    int fd;

    int res;



    fd = open("/dev/rtc0", O_RDWR);

    if (fd < 0) {

        ALOGV("Unable to open RTC driver: %s\n", strerror(errno));

        return -1;

    }



    res = settimeofday(tv, NULL);

    if (res < 0) {

        ALOGV("settimeofday() failed: %s\n", strerror(errno));

        goto done;

    }



    gmtime_res = gmtime_r(&tv->tv_sec, &tm);

    if (!gmtime_res) {

        ALOGV("gmtime_r() failed: %s\n", strerror(errno));

        res = -1;

        goto done;

    }



    memset(&rtc, 0, sizeof(rtc));

    rtc.tm_sec = tm.tm_sec;

    rtc.tm_min = tm.tm_min;

    rtc.tm_hour = tm.tm_hour;

    rtc.tm_mday = tm.tm_mday;

    rtc.tm_mon = tm.tm_mon;

    rtc.tm_year = tm.tm_year;

    rtc.tm_wday = tm.tm_wday;

    rtc.tm_yday = tm.tm_yday;

    rtc.tm_isdst = tm.tm_isdst;

    res = ioctl(fd, RTC_SET_TIME, &rtc);

    if (res < 0)

        ALOGV("RTC_SET_TIME ioctl failed: %s\n", strerror(errno));

done:

    close(fd);

    return res;

}



/*

 * Set the current time.  This only works when running as root.

 */

static int setCurrentTimeMillis(int64_t millis)

{

    struct timeval tv;

    int ret;



    if (millis <= 0 || millis / 1000LL >= INT_MAX) {

        return -1;

    }



    tv.tv_sec = (time_t) (millis / 1000LL);

    tv.tv_usec = (suseconds_t) ((millis % 1000LL) * 1000LL);



    ALOGD("Setting time of day to sec=%d\n", (int) tv.tv_sec);



    ret = setCurrentTimeMillisAlarmDriver(&tv);

    if (ret < 0)

        ret = setCurrentTimeMillisRtc(&tv);



    if(ret < 0) {

        ALOGW("Unable to set rtc to %ld: %s\n", tv.tv_sec, strerror(errno));

        ret = -1;

    }

    return ret;

}



/*

 * native public static void setCurrentTimeMillis(long millis)

 *

 * Set the current time.  This only works when running as root.

 */

static jboolean android_os_SystemClock_setCurrentTimeMillis(JNIEnv* env,

    jobject clazz, jlong millis)

{

    return (setCurrentTimeMillis(millis) == 0);

}



/*

 * native public static long uptimeMillis();

 */
@@ -230,8 +120,6 @@ static jlong android_os_SystemClock_elapsedRealtimeNano(JNIEnv* env, 
 */

static JNINativeMethod gMethods[] = {

    /* name, signature, funcPtr */

    { "setCurrentTimeMillis",      "(J)Z",

            (void*) android_os_SystemClock_setCurrentTimeMillis },

    { "uptimeMillis",      "()J",

            (void*) android_os_SystemClock_uptimeMillis },

    { "elapsedRealtime",      "()J",

services/java/com/android/server/AlarmManagerService.java

+10 −2
Original line number Diff line number Diff line
@@ -669,12 +669,19 @@ class AlarmManagerService extends IAlarmManager.Stub { 
        }

    }



    public void setTime(long millis) {

    public boolean setTime(long millis) {

        mContext.enforceCallingOrSelfPermission(

                "android.permission.SET_TIME",

                "setTime");



        SystemClock.setCurrentTimeMillis(millis);

        if (mNativeData == 0) {

            Slog.w(TAG, "Not setting time since no alarm driver is available.");

            return false;

        }



        synchronized (mLock) {

            return setKernelTime(mNativeData, millis) == 0;

        }

    }



    public void setTimeZone(String tz) {
@@ -1018,6 +1025,7 @@ class AlarmManagerService extends IAlarmManager.Stub { 
    private native void close(long nativeData);

    private native void set(long nativeData, int type, long seconds, long nanoseconds);

    private native int waitForAlarm(long nativeData);

    private native int setKernelTime(long nativeData, long millis);

    private native int setKernelTimezone(long nativeData, int minuteswest);



    private void triggerAlarmsLocked(ArrayList<Alarm> triggerList, long nowELAPSED, long nowRTC) {

services/jni/com_android_server_AlarmManagerService.cpp

+86 −0
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ 
#include <unistd.h>

#include <linux/ioctl.h>

#include <linux/android_alarm.h>

#include <linux/rtc.h>



namespace android {
@@ -58,6 +59,7 @@ public: 
    virtual ~AlarmImpl();



    virtual int set(int type, struct timespec *ts) = 0;

    virtual int setTime(struct timeval *tv) = 0;

    virtual int waitForAlarm() = 0;



protected:
@@ -71,6 +73,7 @@ public: 
    AlarmImplAlarmDriver(int fd) : AlarmImpl(&fd, 1) { }



    int set(int type, struct timespec *ts);

    int setTime(struct timeval *tv);

    int waitForAlarm();

};
@@ -82,6 +85,7 @@ public: 
    ~AlarmImplTimerFd();



    int set(int type, struct timespec *ts);

    int setTime(struct timeval *tv);

    int waitForAlarm();



private:
@@ -107,6 +111,19 @@ int AlarmImplAlarmDriver::set(int type, struct timespec *ts) 
    return ioctl(fds[0], ANDROID_ALARM_SET(type), ts);

}



int AlarmImplAlarmDriver::setTime(struct timeval *tv)

{

    struct timespec ts;

    int res;



    ts.tv_sec = tv->tv_sec;

    ts.tv_nsec = tv->tv_usec * 1000;

    res = ioctl(fds[0], ANDROID_ALARM_SET_RTC, &ts);

    if (res < 0)

        ALOGV("ANDROID_ALARM_SET_RTC ioctl failed: %s\n", strerror(errno));

    return res;

}



int AlarmImplAlarmDriver::waitForAlarm()

{

    return ioctl(fds[0], ANDROID_ALARM_WAIT);
@@ -140,6 +157,50 @@ int AlarmImplTimerFd::set(int type, struct timespec *ts) 
    return timerfd_settime(fds[type], TFD_TIMER_ABSTIME, &spec, NULL);

}



int AlarmImplTimerFd::setTime(struct timeval *tv)

{

    struct rtc_time rtc;

    struct tm tm, *gmtime_res;

    int fd;

    int res;



    fd = open("/dev/rtc0", O_RDWR);

    if (fd < 0) {

        ALOGV("Unable to open RTC driver: %s\n", strerror(errno));

        return -1;

    }



    res = settimeofday(tv, NULL);

    if (res < 0) {

        ALOGV("settimeofday() failed: %s\n", strerror(errno));

        goto done;

    }



    gmtime_res = gmtime_r(&tv->tv_sec, &tm);

    if (!gmtime_res) {

        ALOGV("gmtime_r() failed: %s\n", strerror(errno));

        res = -1;

        goto done;

    }



    memset(&rtc, 0, sizeof(rtc));

    rtc.tm_sec = tm.tm_sec;

    rtc.tm_min = tm.tm_min;

    rtc.tm_hour = tm.tm_hour;

    rtc.tm_mday = tm.tm_mday;

    rtc.tm_mon = tm.tm_mon;

    rtc.tm_year = tm.tm_year;

    rtc.tm_wday = tm.tm_wday;

    rtc.tm_yday = tm.tm_yday;

    rtc.tm_isdst = tm.tm_isdst;

    res = ioctl(fd, RTC_SET_TIME, &rtc);

    if (res < 0)

        ALOGV("RTC_SET_TIME ioctl failed: %s\n", strerror(errno));

done:

    close(fd);

    return res;

}



int AlarmImplTimerFd::waitForAlarm()

{

    epoll_event events[N_ANDROID_TIMERFDS];
@@ -168,6 +229,30 @@ int AlarmImplTimerFd::waitForAlarm() 
    return result;

}



static jint android_server_AlarmManagerService_setKernelTime(JNIEnv*, jobject, jlong nativeData, jlong millis)

{

    AlarmImpl *impl = reinterpret_cast<AlarmImpl *>(nativeData);

    struct timeval tv;

    int ret;



    if (millis <= 0 || millis / 1000LL >= INT_MAX) {

        return -1;

    }



    tv.tv_sec = (time_t) (millis / 1000LL);

    tv.tv_usec = (suseconds_t) ((millis % 1000LL) * 1000LL);



    ALOGD("Setting time of day to sec=%d\n", (int) tv.tv_sec);



    ret = impl->setTime(&tv);



    if(ret < 0) {

        ALOGW("Unable to set rtc to %ld: %s\n", tv.tv_sec, strerror(errno));

        ret = -1;

    }

    return ret;

}



static jint android_server_AlarmManagerService_setKernelTimezone(JNIEnv*, jobject, jlong, jint minswest)

{

    struct timezone tz;
@@ -309,6 +394,7 @@ static JNINativeMethod sMethods[] = { 
    {"close", "(J)V", (void*)android_server_AlarmManagerService_close},

    {"set", "(JIJJ)V", (void*)android_server_AlarmManagerService_set},

    {"waitForAlarm", "(J)I", (void*)android_server_AlarmManagerService_waitForAlarm},

    {"setKernelTime", "(JJ)I", (void*)android_server_AlarmManagerService_setKernelTime},

    {"setKernelTimezone", "(JI)I", (void*)android_server_AlarmManagerService_setKernelTimezone},

};