Add support for processing class loader contexts
Initial support for recognizing the class loader contexts.
In order to correctly compile dex files which at runtime are loaded with
a non-trivial class loader chain we need to make dex2oat aware of the
precise runtime context.
This CL adds the infrastructure to process arbitrary and arbitrary chain
of class loaders. ClassLoaderContext is able to parse a class loader
spec from a string and create the runtime structure based on it.
The integration with dex2oat and oat file assistant will follow up.
The string specification looks like
"PCL[lib1.dex:lib2.dex];DLC[lib3.dex]"
It describes how the class loader chain should be build in order to
ensure classes are resolved during dex2aot as they would be resolved at
runtime. This spec will be encoded in the oat file. If at runtime the
dex file will be loaded in a different context, the oat file will be
rejected.
The chain is interpreted in the natural 'parent order', meaning that
class loader 'i+1' will be the parent of class loader 'i'. The
compilation sources will be added to the classpath of the last class
loader. This allows the compiled dex files to be loaded at runtime in a
class loader that contains other dex files as well (e.g. shared
libraries).
Note that we accept chains for which the source dex files specified
with --dex-file are found in the classpath. In this case the source dex
files will be removed from the any class loader's classpath possibly
resulting in empty class loaders.
* This is the first CL, which adds the infrastructure for processing
a class loader context. Currently it CHECKS that only a single
PathClassLoader is created.
Test: m test-art-host
Bug: 38138251
Change-Id: I312aa12b5732288f3c1df4746b5775a32e0bfb04
diff --git a/runtime/class_loader_context.h b/runtime/class_loader_context.h
new file mode 100644
index 0000000..4af5017
--- /dev/null
+++ b/runtime/class_loader_context.h
@@ -0,0 +1,150 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#ifndef ART_RUNTIME_CLASS_LOADER_CONTEXT_H_
+#define ART_RUNTIME_CLASS_LOADER_CONTEXT_H_
+
+#include <string>
+#include <vector>
+
+#include "arch/instruction_set.h"
+#include "base/dchecked_vector.h"
+#include "jni.h"
+
+namespace art {
+
+class DexFile;
+class OatFile;
+
+// Utility class which holds the class loader context used during compilation/verification.
+class ClassLoaderContext {
+ public:
+ // Creates an empty context (with no class loaders).
+ ClassLoaderContext();
+
+ // Opens requested class path files and appends them to ClassLoaderInfo::opened_dex_files.
+ // If the dex files have been stripped, the method opens them from their oat files which are added
+ // to ClassLoaderInfo::opened_oat_files. The 'classpath_dir' argument specifies the directory to
+ // use for the relative class paths.
+ // Returns true if all dex files where successfully opened.
+ // It may be called only once per ClassLoaderContext. The second call will abort.
+ //
+ // Note that a "false" return could mean that either an apk/jar contained no dex files or
+ // that we hit a I/O or checksum mismatch error.
+ // TODO(calin): Currently there's no easy way to tell the difference.
+ //
+ // TODO(calin): we're forced to complicate the flow in this class with a different
+ // OpenDexFiles step because the current dex2oat flow requires the dex files be opened before
+ // the class loader is created. Consider reworking the dex2oat part.
+ bool OpenDexFiles(InstructionSet isa, const std::string& classpath_dir);
+
+ // Remove the specified compilation sources from all classpaths present in this context.
+ // Should only be called before the first call to OpenDexFiles().
+ bool RemoveLocationsFromClassPaths(const dchecked_vector<std::string>& compilation_sources);
+
+ // Creates the entire class loader hierarchy according to the current context.
+ // The compilation sources are appended to the classpath of the top class loader
+ // (i.e the class loader whose parent is the BootClassLoader).
+ // Should only be called if OpenDexFiles() returned true.
+ jobject CreateClassLoader(const std::vector<const DexFile*>& compilation_sources) const;
+
+ // Encodes the context as a string suitable to be added in oat files.
+ // (so that it can be read and verified at runtime against the actual class
+ // loader hierarchy).
+ // Should only be called if OpenDexFiles() returned true.
+ // E.g. if the context is PCL[a.dex:b.dex] this will return "a.dex*a_checksum*b.dex*a_checksum".
+ std::string EncodeContextForOatFile(const std::string& base_dir) const;
+
+ // Flattens the opened dex files into the given vector.
+ // Should only be called if OpenDexFiles() returned true.
+ std::vector<const DexFile*> FlattenOpenedDexFiles() const;
+
+ // Creates the class loader context from the given string.
+ // The format: ClassLoaderType1[ClasspathElem1:ClasspathElem2...];ClassLoaderType2[...]...
+ // ClassLoaderType is either "PCL" (PathClassLoader) or "DLC" (DelegateLastClassLoader).
+ // ClasspathElem is the path of dex/jar/apk file.
+ // Note that we allowed class loaders with an empty class path in order to support a custom
+ // class loader for the source dex files.
+ static std::unique_ptr<ClassLoaderContext> Create(const std::string& spec);
+
+ private:
+ enum ClassLoaderType {
+ kInvalidClassLoader = 0,
+ kPathClassLoader = 1,
+ kDelegateLastClassLoader = 2
+ };
+
+ struct ClassLoaderInfo {
+ // The type of this class loader.
+ ClassLoaderType type;
+ // The list of class path elements that this loader loads.
+ // Note that this list may contain relative paths.
+ std::vector<std::string> classpath;
+ // After OpenDexFiles is called this holds the opened dex files.
+ std::vector<std::unique_ptr<const DexFile>> opened_dex_files;
+ // After OpenDexFiles, in case some of the dex files were opened from their oat files
+ // this holds the list of opened oat files.
+ std::vector<std::unique_ptr<OatFile>> opened_oat_files;
+
+ explicit ClassLoaderInfo(ClassLoaderType cl_type) : type(cl_type) {}
+ };
+
+ // Reads the class loader spec in place and returns true if the spec is valid and the
+ // compilation context was constructed.
+ bool Parse(const std::string& spec);
+
+ // Attempts to parse a single class loader spec for the given class_loader_type.
+ // If successful the class loader spec will be added to the chain.
+ // Returns whether or not the operation was successful.
+ bool ParseClassLoaderSpec(const std::string& class_loader_spec,
+ ClassLoaderType class_loader_type);
+
+ // Extracts the class loader type from the given spec.
+ // Return ClassLoaderContext::kInvalidClassLoader if the class loader type is not
+ // recognized.
+ static ClassLoaderType ExtractClassLoaderType(const std::string& class_loader_spec);
+
+ // Returns the string representation of the class loader type.
+ // The returned format can be used when parsing a context spec.
+ static const char* GetClassLoaderTypeName(ClassLoaderType type);
+
+ // CHECKs that the dex files were opened (OpenDexFiles was called). Aborts if not.
+ void CheckDexFilesOpened(const std::string& calling_method) const;
+
+ // The class loader chain represented as a vector.
+ // The parent of class_loader_chain_[i] is class_loader_chain_[i++].
+ // The parent of the last element is assumed to be the boot class loader.
+ std::vector<ClassLoaderInfo> class_loader_chain_;
+
+ // Whether or not the class loader context should be ignored at runtime when loading the oat
+ // files. When true, dex2oat will use OatFile::kSpecialSharedLibrary as the classpath key in
+ // the oat file.
+ // TODO(calin): Can we get rid of this and cover all relevant use cases?
+ // (e.g. packages using prebuild system packages as shared libraries b/36480683)
+ bool special_shared_library_;
+
+ // Whether or not OpenDexFiles() was called.
+ bool dex_files_open_attempted_;
+ // The result of the last OpenDexFiles() operation.
+ bool dex_files_open_result_;
+
+ friend class ClassLoaderContextTest;
+
+ DISALLOW_COPY_AND_ASSIGN(ClassLoaderContext);
+};
+
+} // namespace art
+#endif // ART_RUNTIME_CLASS_LOADER_CONTEXT_H_