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// Copyright 2021 Code Intelligence GmbH
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.code_intelligence.jazzer.runtime;
import static com.code_intelligence.jazzer.runtime.Constants.IS_ANDROID;
import com.code_intelligence.jazzer.utils.UnsafeProvider;
import com.github.fmeum.rules_jni.RulesJni;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import sun.misc.Unsafe;
/**
* Represents the Java view on a libFuzzer 8 bit counter coverage map. By using a direct ByteBuffer,
* the counters are shared directly with native code.
*/
final public class CoverageMap {
static {
RulesJni.loadLibrary("jazzer_driver", "/com/code_intelligence/jazzer/driver");
}
private static final String ENV_MAX_NUM_COUNTERS = "JAZZER_MAX_NUM_COUNTERS";
private static final int MAX_NUM_COUNTERS = System.getenv(ENV_MAX_NUM_COUNTERS) != null
? Integer.parseInt(System.getenv(ENV_MAX_NUM_COUNTERS))
: 1 << 20;
private static final Unsafe UNSAFE = UnsafeProvider.getUnsafe();
private static final Class<?> LOG;
private static final MethodHandle LOG_INFO;
private static final MethodHandle LOG_ERROR;
static {
try {
LOG = Class.forName(
"com.code_intelligence.jazzer.utils.Log", false, ClassLoader.getSystemClassLoader());
LOG_INFO = MethodHandles.lookup().findStatic(
LOG, "info", MethodType.methodType(void.class, String.class));
LOG_ERROR = MethodHandles.lookup().findStatic(
LOG, "error", MethodType.methodType(void.class, String.class, Throwable.class));
} catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException e) {
throw new RuntimeException(e);
}
}
/**
* The collection of coverage counters directly interacted with by classes that are instrumented
* for coverage. The instrumentation assumes that this is always one contiguous block of memory,
* so it is allocated once at maximum size. Using a larger number here increases the memory usage
* of all fuzz targets, but has otherwise no impact on performance.
*/
public static final long countersAddress = UNSAFE.allocateMemory(MAX_NUM_COUNTERS);
static {
UNSAFE.setMemory(countersAddress, MAX_NUM_COUNTERS, (byte) 0);
initialize(countersAddress);
}
private static final int INITIAL_NUM_COUNTERS = 1 << 9;
static {
registerNewCounters(0, INITIAL_NUM_COUNTERS);
}
/**
* The number of coverage counters that are currently registered with libFuzzer. This number grows
* dynamically as classes are instrumented and should be kept as low as possible as libFuzzer has
* to iterate over the whole map for every execution.
*/
private static int currentNumCounters = INITIAL_NUM_COUNTERS;
// Called via reflection.
@SuppressWarnings("unused")
public static void enlargeIfNeeded(int nextId) {
int newNumCounters = currentNumCounters;
while (nextId >= newNumCounters) {
newNumCounters = 2 * newNumCounters;
if (newNumCounters > MAX_NUM_COUNTERS) {
logError(
String.format(
"Maximum number (%s) of coverage counters exceeded. Try to limit the scope of a single fuzz target as "
+ "much as possible to keep the fuzzer fast. If that is not possible, the maximum number of "
+ "counters can be increased via the %s environment variable.",
MAX_NUM_COUNTERS, ENV_MAX_NUM_COUNTERS),
null);
System.exit(1);
}
}
if (newNumCounters > currentNumCounters) {
registerNewCounters(currentNumCounters, newNumCounters);
currentNumCounters = newNumCounters;
logInfo("New number of coverage counters: " + currentNumCounters);
}
}
// Called by the coverage instrumentation.
@SuppressWarnings("unused")
public static void recordCoverage(final int id) {
if (IS_ANDROID) {
enlargeIfNeeded(id);
}
final long address = countersAddress + id;
final byte counter = UNSAFE.getByte(address);
UNSAFE.putByte(address, (byte) (counter == -1 ? 1 : counter + 1));
}
public static Set<Integer> getCoveredIds() {
Set<Integer> coveredIds = new HashSet<>();
for (int id = 0; id < currentNumCounters; id++) {
if (UNSAFE.getByte(countersAddress + id) > 0) {
coveredIds.add(id);
}
}
return Collections.unmodifiableSet(coveredIds);
}
public static void replayCoveredIds(Set<Integer> coveredIds) {
for (int id : coveredIds) {
UNSAFE.putByte(countersAddress + id, (byte) 1);
}
}
private static void logInfo(String message) {
try {
LOG_INFO.invokeExact(message);
} catch (Throwable error) {
// Should not be reached, Log.error does not throw.
error.printStackTrace();
System.err.println("Failed to call Log.info:");
System.err.println(message);
}
}
private static void logError(String message, Throwable t) {
try {
LOG_ERROR.invokeExact(message, t);
} catch (Throwable error) {
// Should not be reached, Log.error does not throw.
error.printStackTrace();
System.err.println("Failed to call Log.error:");
System.err.println(message);
}
}
// Returns the IDs of all blocks that have been covered in at least one run (not just the current
// one).
public static native int[] getEverCoveredIds();
private static native void initialize(long countersAddress);
private static native void registerNewCounters(int oldNumCounters, int newNumCounters);
}
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