1 // Copyright 2022 Code Intelligence GmbH
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 //      http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14 
15 package com.code_intelligence.jazzer.instrumentor;
16 
17 import java.lang.reflect.Field;
18 import sun.misc.Unsafe;
19 
20 public final class UnsafeBranchfreeCoverageMap {
21   private static final Unsafe UNSAFE;
22 
23   static {
24     Unsafe unsafe;
25     try {
26       Field f = Unsafe.class.getDeclaredField("theUnsafe");
27       f.setAccessible(true);
28       unsafe = (Unsafe) f.get(null);
29     } catch (IllegalAccessException | NoSuchFieldException e) {
30       e.printStackTrace();
31       System.exit(1);
32       // Not reached.
33       unsafe = null;
34     }
35     UNSAFE = unsafe;
36   }
37 
38   // The current target, JsonSanitizer, uses less than 2048 coverage counters.
39   private static final long NUM_COUNTERS = 4096;
40   private static final long countersAddress = UNSAFE.allocateMemory(NUM_COUNTERS);
41 
42   static {
UNSAFE.setMemory(countersAddress, NUM_COUNTERS, (byte) 0)43     UNSAFE.setMemory(countersAddress, NUM_COUNTERS, (byte) 0);
44   }
45 
enlargeIfNeeded(int nextId)46   public static void enlargeIfNeeded(int nextId) {
47     // Statically sized counters buffer.
48   }
49 
recordCoverage(final int id)50   public static void recordCoverage(final int id) {
51     final long address = countersAddress + id;
52     final int incrementedCounter = UNSAFE.getByte(address) + 1;
53     UNSAFE.putByte(address, (byte) (incrementedCounter ^ (incrementedCounter >>> 8)));
54   }
55 }
56