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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package dalvik.system;
     18 
     19 import java.io.FileDescriptor;
     20 import java.io.FileNotFoundException;
     21 import java.io.FileOutputStream;
     22 import java.io.IOException;
     23 import java.math.BigInteger;
     24 import java.net.SocketException;
     25 import java.nio.charset.Charsets;
     26 
     27 /**
     28  * Mechanism to let threads set restrictions on what code is allowed
     29  * to do in their thread.
     30  *
     31  * <p>This is meant for applications to prevent certain blocking
     32  * operations from running on their main event loop (or "UI") threads.
     33  *
     34  * <p>Note that this is all best-effort to catch most accidental mistakes
     35  * and isn't intended to be a perfect mechanism, nor provide any sort of
     36  * security.
     37  *
     38  * @hide
     39  */
     40 public final class BlockGuard {
     41 
     42     // TODO: refactor class name to something more generic, since its scope is
     43     // growing beyond just blocking/logging.
     44 
     45     public static final int DISALLOW_DISK_WRITE = 0x01;
     46     public static final int DISALLOW_DISK_READ = 0x02;
     47     public static final int DISALLOW_NETWORK = 0x04;
     48     public static final int PASS_RESTRICTIONS_VIA_RPC = 0x08;
     49     public static final int PENALTY_LOG = 0x10;
     50     public static final int PENALTY_DIALOG = 0x20;
     51     public static final int PENALTY_DEATH = 0x40;
     52 
     53     public interface Policy {
     54         /**
     55          * Called on disk writes.
     56          */
     57         void onWriteToDisk();
     58 
     59         /**
     60          * Called on disk reads.
     61          */
     62         void onReadFromDisk();
     63 
     64         /**
     65          * Called on network operations.
     66          */
     67         void onNetwork();
     68 
     69         /**
     70          * Returns the policy bitmask, for shipping over Binder calls
     71          * to remote threads/processes and reinstantiating the policy
     72          * there.  The bits in the mask are from the DISALLOW_* and
     73          * PENALTY_* constants.
     74          */
     75         int getPolicyMask();
     76     }
     77 
     78     public static class BlockGuardPolicyException extends RuntimeException {
     79         // bitmask of DISALLOW_*, PENALTY_*, etc flags
     80         private final int mPolicyState;
     81         private final int mPolicyViolated;
     82         private final String mMessage;   // may be null
     83 
     84         public BlockGuardPolicyException(int policyState, int policyViolated) {
     85             this(policyState, policyViolated, null);
     86         }
     87 
     88         public BlockGuardPolicyException(int policyState, int policyViolated, String message) {
     89             mPolicyState = policyState;
     90             mPolicyViolated = policyViolated;
     91             mMessage = message;
     92             fillInStackTrace();
     93         }
     94 
     95         public int getPolicy() {
     96             return mPolicyState;
     97         }
     98 
     99         public int getPolicyViolation() {
    100             return mPolicyViolated;
    101         }
    102 
    103         public String getMessage() {
    104             // Note: do not change this format casually.  It's
    105             // somewhat unfortunately Parceled and passed around
    106             // Binder calls and parsed back into an Exception by
    107             // Android's StrictMode.  This was the least invasive
    108             // option and avoided a gross mix of Java Serialization
    109             // combined with Parcels.
    110             return "policy=" + mPolicyState + " violation=" + mPolicyViolated +
    111                     (mMessage == null ? "" : (" msg=" + mMessage));
    112         }
    113     }
    114 
    115     /**
    116      * The default, permissive policy that doesn't prevent any operations.
    117      */
    118     public static final Policy LAX_POLICY = new Policy() {
    119             public void onWriteToDisk() {}
    120             public void onReadFromDisk() {}
    121             public void onNetwork() {}
    122             public int getPolicyMask() {
    123                 return 0;
    124             }
    125         };
    126 
    127     private static ThreadLocal<Policy> threadPolicy = new ThreadLocal<Policy>() {
    128         @Override protected Policy initialValue() {
    129             return LAX_POLICY;
    130         }
    131     };
    132 
    133     /**
    134      * Get the current thread's policy.
    135      *
    136      * @return the current thread's policy.  Never returns null.
    137      *     Will return the LAX_POLICY instance if nothing else is set.
    138      */
    139     public static Policy getThreadPolicy() {
    140         return threadPolicy.get();
    141     }
    142 
    143     /**
    144      * Sets the current thread's block guard policy.
    145      *
    146      * @param policy policy to set.  May not be null.  Use the public LAX_POLICY
    147      *   if you want to unset the active policy.
    148      */
    149     public static void setThreadPolicy(Policy policy) {
    150         if (policy == null) {
    151             throw new NullPointerException("policy == null");
    152         }
    153         threadPolicy.set(policy);
    154     }
    155 
    156     private BlockGuard() {}
    157 }
    158