systemDictionary.hpp revision 1833
/*
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* published by the Free Software Foundation.
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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// The system dictionary stores all loaded classes and maps:
//
// [class name,class loader] -> class i.e. [symbolOop,oop] -> klassOop
//
// Classes are loaded lazily. The default VM class loader is
// represented as NULL.
// The underlying data structure is an open hash table with a fixed number
// of buckets. During loading the loader object is locked, (for the VM loader
// a private lock object is used). Class loading can thus be done concurrently,
// but only by different loaders.
//
// During loading a placeholder (name, loader) is temporarily placed in
// a side data structure, and is used to detect ClassCircularityErrors
// and to perform verification during GC. A GC can occur in the midst
// of class loading, as we call out to Java, have to take locks, etc.
//
// When class loading is finished, a new entry is added to the system
// dictionary and the place holder is removed. Note that the protection
// domain field of the system dictionary has not yet been filled in when
// the "real" system dictionary entry is created.
//
// Clients of this class who are interested in finding if a class has
// been completely loaded -- not classes in the process of being loaded --
// can read the SystemDictionary unlocked. This is safe because
// - entries are only deleted at safepoints
// - readers cannot come to a safepoint while actively examining
// an entry (an entry cannot be deleted from under a reader)
// - entries must be fully formed before they are available to concurrent
// readers (we must ensure write ordering)
//
// Note that placeholders are deleted at any time, as they are removed
// when a class is completely loaded. Therefore, readers as well as writers
// of placeholders must hold the SystemDictionary_lock.
//
class Dictionary;
class PlaceholderTable;
class LoaderConstraintTable;
class HashtableBucket;
class ResolutionErrorTable;
class SymbolPropertyTable;
// Certain classes are preloaded, such as java.lang.Object and java.lang.String.
// They are all "well-known", in the sense that no class loader is allowed
// to provide a different definition.
//
// These klasses must all have names defined in vmSymbols.
// Each well-known class has a short klass name (like object_klass),
// a vmSymbol name (like java_lang_Object), and a flag word
// that makes some minor distinctions, like whether the klass
// is preloaded, optional, release-specific, etc.
// The order of these definitions is significant; it is the order in which
// preloading is actually performed by initialize_preloaded_classes.
#define WK_KLASSES_DO(template) \
/* well-known classes */ \
\
/* Preload ref klasses and set reference types */ \
\
\
/* NOTE: needed too early in bootstrapping process to have checks based on JDK version */ \
/* Universe::is_gte_jdk14x_version() is not set up by this point. */ \
/* It's okay if this turns out to be NULL in non-1.4 JDKs. */ \
template(reflect_ConstructorAccessorImpl_klass, sun_reflect_ConstructorAccessorImpl, Opt_Only_JDK14NewRef) \
template(reflect_UnsafeStaticFieldAccessorImpl_klass, sun_reflect_UnsafeStaticFieldAccessorImpl, Opt_Only_JDK15) \
\
/* support for dynamic typing; it's OK if these are NULL in earlier JDKs */ \
/* Note: MethodHandle must be first, and InvokeDynamic last in group */ \
\
\
/* It's NULL in non-1.4 JDKs. */ \
/* Universe::is_gte_jdk14x_version() is not set up by this point. */ \
/* It's okay if this turns out to be NULL in non-1.4 JDKs. */ \
\
/* If this class isn't present, it won't be referenced. */ \
\
\
/* Preload boxing klasses */ \
/*end*/
class SystemDictionary : AllStatic {
friend class VMStructs;
friend class CompactingPermGenGen;
friend class SystemDictionaryHandles;
NOT_PRODUCT(friend class instanceKlassKlass;)
public:
enum WKID {
NO_WKID = 0,
};
enum InitOption {
Pre, // preloaded; error if not present
// Order is significant. Options before this point require resolve_or_fail.
// Options after this point will use resolve_or_null instead.
Opt, // preload tried; NULL if not present
Opt_Only_JDK14NewRef, // preload tried; use only with NewReflection
Opt_Only_JDK15, // preload tried; use only with JDK1.5+
Opt_Kernel, // preload tried only #ifdef KERNEL
};
// Returns a class with a given class name and class loader. Loads the
// class if needed. If not found a NoClassDefFoundError or a
// ClassNotFoundException is thrown, depending on the value on the
// throw_error flag. For most uses the throw_error argument should be set
// to true.
static klassOop resolve_or_fail(symbolHandle class_name, Handle class_loader, Handle protection_domain, bool throw_error, TRAPS);
// Convenient call for null loader and protection domain.
private:
// handle error translation for resolve_or_null results
static klassOop handle_resolution_exception(symbolHandle class_name, Handle class_loader, Handle protection_domain, bool throw_error, KlassHandle klass_h, TRAPS);
public:
// Returns a class with a given class name and class loader.
// Loads the class if needed. If not found NULL is returned.
static klassOop resolve_or_null(symbolHandle class_name, Handle class_loader, Handle protection_domain, TRAPS);
// Version with null loader and protection domain
// Resolve a superclass or superinterface. Called from ClassFileParser,
// parse_interfaces, resolve_instance_class_or_null, load_shared_class
// "child_name" is the class whose super class or interface is being resolved.
bool is_superclass,
TRAPS);
// Parse new stream. This won't update the system dictionary or
// class hierarchy, simply parse the stream. Used by JVMTI RedefineClasses.
TRAPS) {
}
TRAPS);
// Resolve from stream (called by jni_DefineClass and JVM_DefineClass)
// Lookup an already loaded class. If not found NULL is returned.
static klassOop find(symbolHandle class_name, Handle class_loader, Handle protection_domain, TRAPS);
// Lookup an already loaded instance or array class.
// Do not make any queries to class loaders; consult only the cache.
// If not found NULL is returned.
TRAPS);
// If the given name is known to vmSymbols, return the well-know klass:
// Lookup an instance or array class that has already been loaded
// either into the given class loader, or else into another class
// loader that is constrained (via loader constraints) to produce
// a consistent class. Do not take protection domains into account.
// Do not make any queries to class loaders; consult only the cache.
// Return NULL if the class is not found.
//
// This function is a strict superset of find_instance_or_array_klass.
// This function (the unchecked version) makes a conservative prediction
// of the result of the checked version, assuming successful lookup.
// If both functions return non-null, they must return the same value.
// Also, the unchecked version may sometimes be non-null where the
// checked version is null. This can occur in several ways:
// 1. No query has yet been made to the class loader.
// 2. The class loader was queried, but chose not to delegate.
// 3. ClassLoader.checkPackageAccess rejected a proposed protection domain.
// 4. Loading was attempted, but there was a linkage error of some sort.
// In all of these cases, the loader constraints on this type are
// satisfied, and it is safe for classes in the given class loader
// to manipulate strongly-typed values of the found class, subject
// to local linkage and access checks.
TRAPS);
// Iterate over all klasses in dictionary
// Just the classes from defining class loaders
static void classes_do(void f(klassOop));
// Added for initialize_itable_for_klass to handle exceptions
// All classes, and their class loaders
// All classes, and their class loaders
// (added for helpers that use HandleMarks and ResourceMarks)
// All entries in the placeholder table and their class loaders
// Iterate over all methods in all klasses in dictionary
static void methods_do(void f(methodOop));
// Garbage collection support
// This method applies "blk->do_oop" to all the pointers to "system"
// classes and loaders.
// This method applies "blk->do_oop" to all the placeholders.
// Unload (that is, break root links to) all unmarked classes and
// loaders. Returns "true" iff something was unloaded.
// Applies "f->do_oop" to all root oops in the system dictionary.
static void oops_do(OopClosure* f);
// System loader lock
private:
// Traverses preloaded oops: various system classes. These are
// guaranteed to be in the perm gen.
static void preloaded_oops_do(OopClosure* f);
static void lazily_loaded_oops_do(OopClosure* f);
public:
// Sharing support.
static void reorder_dictionary();
static void reverse();
int number_of_entries);
// Printing
static void print() PRODUCT_RETURN;
static void print_class_statistics() PRODUCT_RETURN;
static void print_method_statistics() PRODUCT_RETURN;
// Number of contained klasses
// This is both fully loaded classes and classes in the process
// of being loaded
static int number_of_classes();
// Monotonically increasing counter which grows as classes are
// of breakpoints are performed
static inline int number_of_modifications() { assert_locked_or_safepoint(Compile_lock); return _number_of_modifications; }
// Needed by evolution and breakpoint code
static inline void notice_modification() { assert_locked_or_safepoint(Compile_lock); ++_number_of_modifications; }
// Verification
static void verify();
#ifdef ASSERT
#endif
// Verify class is in dictionary
// Initialization
static void initialize(TRAPS);
// Fast access to commonly used classes (preloaded)
return k;
}
return k;
}
// despite the optional loading, if you use this it must be present:
return check_klass(k);
}
}
public:
static klassOop name() { return check_klass_##option(_well_known_klasses[WK_KLASS_ENUM_NAME(name)]); }
// Local definition for direct access to the private array:
return check_klass(_box_klasses[t]);
}
// methods returning lazily loaded klasses
// The corresponding method to load the class must be called before calling them.
static klassOop abstract_ownable_synchronizer_klass() { return check_klass(_abstract_ownable_synchronizer_klass); }
static void load_abstract_ownable_synchronizer_klass(TRAPS);
private:
// Tells whether ClassLoader.loadClassInternal is present
static bool has_loadClassInternal() { return _has_loadClassInternal; }
public:
// Tells whether ClassLoader.checkPackageAccess is present
static bool has_checkPackageAccess() { return _has_checkPackageAccess; }
// Returns default system loader
static oop java_system_loader();
// Compute the default system loader
static void compute_java_system_loader(TRAPS);
private:
// Mirrors for primitive classes (created eagerly)
return m;
}
public:
// Note: java_lang_Class::primitive_type is the inverse of java_mirror
// Check class loader constraints
// JSR 292
// find the java.dyn.MethodHandles::invoke method for a given signature
TRAPS);
// ask Java to compute a java.dyn.MethodType object for a given signature
bool for_invokeGeneric,
bool& return_bcp_flag,
TRAPS);
// ask Java to compute a java.dyn.MethodHandle object for a given CP entry
int ref_kind, //e.g., JVM_REF_invokeVirtual
TRAPS);
// ask Java to create a dynamic call site, while linking an invokedynamic op
// Callee information:
// Caller information:
int caller_bci,
TRAPS);
// coordinate with Java about bootstrap methods
int caller_bci, // N.B. must be an invokedynamic
int cache_index, // must be corresponding main_entry
TRAPS);
// Utility for printing loader "name" as part of tracing constraints
}
// Record the error when the first attempt to resolve a reference from a constant
// pool entry to a class fails.
private:
enum Constants {
};
// Static variables
// Hashtable holding loaded classes.
static Dictionary* _dictionary;
// Hashtable holding placeholders for classes being loaded.
static PlaceholderTable* _placeholders;
// Hashtable holding classes from the shared archive.
static Dictionary* _shared_dictionary;
// Monotonically increasing counter which grows with
// _number_of_classes as well as hot-swapping and breakpoint setting
// and removal.
static int _number_of_modifications;
// Lock object for system class loader
static oop _system_loader_lock_obj;
// Constraints on class loaders
static LoaderConstraintTable* _loader_constraints;
// Resolution errors
static ResolutionErrorTable* _resolution_errors;
// Invoke methods (JSR 292)
static SymbolPropertyTable* _invoke_method_table;
public:
// for VM_CounterDecay iteration support
friend class CounterDecay;
static klassOop try_get_next_class();
private:
friend class VM_PopulateDumpSharedSpace;
friend class TraversePlaceholdersClosure;
// Basic loading operations
static klassOop resolve_instance_class_or_null(symbolHandle class_name, Handle class_loader, Handle protection_domain, TRAPS);
static klassOop resolve_array_class_or_null(symbolHandle class_name, Handle class_loader, Handle protection_domain, TRAPS);
static instanceKlassHandle handle_parallel_super_load(symbolHandle class_name, symbolHandle supername, Handle class_loader, Handle protection_domain, Handle lockObject, TRAPS);
// Wait on SystemDictionary_lock; unlocks lockObject before
// waiting; relocks lockObject with correct recursion count
// after waiting, but before reentering SystemDictionary_lock
// to preserve lock order semantics.
instanceKlassHandle k, TRAPS);
static instanceKlassHandle load_instance_class(symbolHandle class_name, Handle class_loader, TRAPS);
// Setup link to hierarchy
private:
// We pass in the hashtable index so we can calculate it outside of
// the SystemDictionary_lock.
// Basic find on loaded classes
// Basic find on classes in the midst of being loaded
// Basic find operation of loaded classes and classes in the midst
// of loading; used for assertions and verification only.
// Updating entry in dictionary
// Add a completely loaded class
// Add a placeholder for a class being loaded
static void add_placeholder(int index,
static void remove_placeholder(int index,
// Performs cleanups after resolve_super_or_fail. This typically needs
// to be called on failure.
// Won't throw, but can block.
TRAPS);
// Initialization
static void initialize_preloaded_classes(TRAPS);
// Class loader constraints
// Variables holding commonly used klasses (preloaded)
static klassOop _well_known_klasses[];
// Lazily loaded klasses
static volatile klassOop _abstract_ownable_synchronizer_klass;
// table of box klasses (int_klass, etc.)
static oop _java_system_loader;
static bool _has_loadClassInternal;
static bool _has_checkPackageAccess;
};
// Cf. vmSymbols vs. vmSymbolHandles
class SystemDictionaryHandles : AllStatic {
public:
static KlassHandle name() { \
SystemDictionary::name(); \
klassOop* loc = &SystemDictionary::_well_known_klasses[SystemDictionary::WK_KLASS_ENUM_NAME(name)]; \
return KlassHandle(loc, true); \
}
};