Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * 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

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 #include "precompiled.hpp"

 #include "classfile/dictionary.hpp"

 #include "classfile/loaderConstraints.hpp"

 #include "classfile/placeholders.hpp"

 #include "classfile/symbolTable.hpp"

 #include "classfile/systemDictionary.hpp"

 #include "code/codeCache.hpp"

 #include "memory/filemap.hpp"

 #include "memory/gcLocker.hpp"

 #include "memory/metaspace.hpp"

 #include "memory/metaspaceShared.hpp"

 #include "oops/objArrayOop.hpp"

 #include "oops/oop.inline.hpp"

 #include "runtime/signature.hpp"

 #include "runtime/vm_operations.hpp"

 #include "runtime/vmThread.hpp"

 #include "utilities/hashtable.inline.hpp"

 int MetaspaceShared::_max_alignment = 0;

 int MetaspaceShared::max_alignment()                   { return _max_alignment; }

 void MetaspaceShared::set_max_alignment(int alignment) { _max_alignment = alignment; }

 // Accessor functions to save shared space created for metadata, which has

 // extra space allocated at the end for miscellaneous data and code.

 ReservedSpace* MetaspaceShared::_shared_rs = NULL;

 ReservedSpace* MetaspaceShared::shared_rs()            { return _shared_rs; }

 void MetaspaceShared::set_shared_rs(ReservedSpace* rs) { _shared_rs = rs; }

 // Read/write a data stream for restoring/preserving metadata pointers and

 // miscellaneous data from/to the shared archive file.

 void MetaspaceShared::serialize(SerializeClosure* soc) {

   int tag = 0;

   soc->do_tag(--tag);

   assert(!UseCompressedOops, "UseCompressedOops doesn't work with shared archive");

   // Verify the sizes of various metadata in the system.

   soc->do_tag(sizeof(Method));

   soc->do_tag(sizeof(ConstMethod));

   soc->do_tag(arrayOopDesc::base_offset_in_bytes(T_BYTE));

   soc->do_tag(sizeof(ConstantPool));

   soc->do_tag(sizeof(ConstantPoolCache));

   soc->do_tag(objArrayOopDesc::base_offset_in_bytes());

   soc->do_tag(typeArrayOopDesc::base_offset_in_bytes(T_BYTE));

   soc->do_tag(sizeof(Symbol));

   // Dump/restore miscellaneous metadata.

   Universe::serialize(soc, true);

   soc->do_tag(--tag);

   // Dump/restore references to commonly used names and signatures.

   vmSymbols::serialize(soc);

   soc->do_tag(--tag);

   soc->do_tag(666);

 }

 // CDS code for dumping shared archive.

 // Global object for holding classes that have been loaded.  Since this

 // is run at a safepoint just before exit, this is the entire set of classes.

 static GrowableArray<Klass*>* _global_klass_objects;

 static void collect_classes(Klass* k) {

   _global_klass_objects->append_if_missing(k);

   if (k->oop_is_instance()) {

     // Add in the array classes too

     InstanceKlass* ik = InstanceKlass::cast(k);

     ik->array_klasses_do(collect_classes);

   }

 }

 static void remove_unshareable_in_classes() {

   for (int i = 0; i < _global_klass_objects->length(); i++) {

     Klass* k = _global_klass_objects->at(i);

     k->remove_unshareable_info();

   }

 }

 // Walk all methods in the class list and assign a fingerprint.

 // so that this part of the ConstMethod* is read only.

 static void calculate_fingerprints() {

   for (int i = 0; i < _global_klass_objects->length(); i++) {

     Klass* k = _global_klass_objects->at(i);

     if (k->oop_is_instance()) {

       InstanceKlass* ik = InstanceKlass::cast(k);

       for (int i = 0; i < ik->methods()->length(); i++) {

         ResourceMark rm;

         Method* m = ik->methods()->at(i);

         (new Fingerprinter(m))->fingerprint();

       }

     }

   }

 }

 // Patch C++ vtable pointer in metadata.

 // Klass and other metadata objects contain references to c++ vtables in the

 // JVM library.

 // Fix them to point to our constructed vtables.  However, don't iterate

 // across the space while doing this, as that causes the vtables to be

 // patched, undoing our useful work.  Instead, iterate to make a list,

 // then use the list to do the fixing.

 //

 // Our constructed vtables:

 // Dump time:

 //  1. init_self_patching_vtbl_list: table of pointers to current virtual method addrs

 //  2. generate_vtable_methods: create jump table, appended to above vtbl_list

 //  3. patch_klass_vtables: for Klass list, patch the vtable entry in klass and

 //     associated metadata to point to jump table rather than to current vtbl

 // Table layout: NOTE FIXED SIZE

 //   1. vtbl pointers

 //   2. #Klass X #virtual methods per Klass

 //   1 entry for each, in the order:

 //   Klass1:method1 entry, Klass1:method2 entry, ... Klass1:method<num_virtuals> entry

 //   Klass2:method1 entry, Klass2:method2 entry, ... Klass2:method<num_virtuals> entry

 //   ...

 //   Klass<vtbl_list_size>:method1 entry, Klass<vtbl_list_size>:method2 entry,

 //       ... Klass<vtbl_list_size>:method<num_virtuals> entry

 //  Sample entry: (Sparc):

 //   save(sp, -256, sp)

 //   ba,pt common_code

 //   mov XXX, %L0       %L0 gets: Klass index <<8 + method index (note: max method index 255)

 //

 // Restore time:

 //   1. initialize_shared_space: reserve space for table

 //   2. init_self_patching_vtbl_list: update pointers to NEW virtual method addrs in text

 //

 // Execution time:

 //   First virtual method call for any object of these metadata types:

 //   1. object->klass

 //   2. vtable entry for that klass points to the jump table entries

 //   3. branches to common_code with %O0/klass, %L0: Klass index <<8 + method index

 //   4. common_code:

 //      Get address of new vtbl pointer for this Klass from updated table

 //      Update new vtbl pointer in the Klass: future virtual calls go direct

 //      Jump to method, using new vtbl pointer and method index

 static void* find_matching_vtbl_ptr(void** vtbl_list, void* new_vtable_start, void* obj) {

   void* old_vtbl_ptr = *(void**)obj;

   for (int i = 0; i < MetaspaceShared::vtbl_list_size; i++) {

     if (vtbl_list[i] == old_vtbl_ptr) {

       return (void**)new_vtable_start + i * MetaspaceShared::num_virtuals;

     }

   }

   ShouldNotReachHere();

   return NULL;

 }

 // Assumes the vtable is in first slot in object.

 static void patch_klass_vtables(void** vtbl_list, void* new_vtable_start) {

   int n = _global_klass_objects->length();

   for (int i = 0; i < n; i++) {

     Klass* obj = _global_klass_objects->at(i);

     // Note oop_is_instance() is a virtual call.  After patching vtables

     // all virtual calls on the dummy vtables will restore the original!

     if (obj->oop_is_instance()) {

       InstanceKlass* ik = InstanceKlass::cast(obj);

       *(void**)ik = find_matching_vtbl_ptr(vtbl_list, new_vtable_start, ik);

       ConstantPool* cp = ik->constants();

       *(void**)cp = find_matching_vtbl_ptr(vtbl_list, new_vtable_start, cp);

       for (int j = 0; j < ik->methods()->length(); j++) {

         Method* m = ik->methods()->at(j);

         *(void**)m = find_matching_vtbl_ptr(vtbl_list, new_vtable_start, m);

       }

     } else {

       // Array klasses

       Klass* k = obj;

       *(void**)k = find_matching_vtbl_ptr(vtbl_list, new_vtable_start, k);

     }

   }

 }

 // Closure for serializing initialization data out to a data area to be

 // written to the shared file.

 class WriteClosure : public SerializeClosure {

 private:

   intptr_t* top;

   char* end;

   inline void check_space() {

     if ((char*)top + sizeof(intptr_t) > end) {

       report_out_of_shared_space(SharedMiscData);

     }

   }

 public:

   WriteClosure(char* md_top, char* md_end) {

     top = (intptr_t*)md_top;

     end = md_end;

   }

   char* get_top() { return (char*)top; }

   void do_ptr(void** p) {

     check_space();

     *top = (intptr_t)*p;

     ++top;

   }

   void do_tag(int tag) {

     check_space();

     *top = (intptr_t)tag;

     ++top;

   }

   void do_region(u_char* start, size_t size) {

     if ((char*)top + size > end) {

       report_out_of_shared_space(SharedMiscData);

     }

     assert((intptr_t)start % sizeof(intptr_t) == 0, "bad alignment");

     assert(size % sizeof(intptr_t) == 0, "bad size");

     do_tag((int)size);

     while (size > 0) {

       *top = *(intptr_t*)start;

       ++top;

       start += sizeof(intptr_t);

       size -= sizeof(intptr_t);

     }

   }

   bool reading() const { return false; }

 };

 // Populate the shared space.

 class VM_PopulateDumpSharedSpace: public VM_Operation {

 private:

   ClassLoaderData* _loader_data;

   GrowableArray<Klass*> *_class_promote_order;

   VirtualSpace _md_vs;

   VirtualSpace _mc_vs;

 public:

   VM_PopulateDumpSharedSpace(ClassLoaderData* loader_data,

                              GrowableArray<Klass*> *class_promote_order) :

     _loader_data(loader_data) {

     // Split up and initialize the misc code and data spaces

     ReservedSpace* shared_rs = MetaspaceShared::shared_rs();

     int metadata_size = SharedReadOnlySize+SharedReadWriteSize;

     ReservedSpace shared_ro_rw = shared_rs->first_part(metadata_size);

     ReservedSpace misc_section = shared_rs->last_part(metadata_size);

     // Now split into misc sections.

     ReservedSpace md_rs   = misc_section.first_part(SharedMiscDataSize);

     ReservedSpace mc_rs   = misc_section.last_part(SharedMiscDataSize);

     _md_vs.initialize(md_rs, SharedMiscDataSize);

     _mc_vs.initialize(mc_rs, SharedMiscCodeSize);

     _class_promote_order = class_promote_order;

   }

   VMOp_Type type() const { return VMOp_PopulateDumpSharedSpace; }

   void doit();   // outline because gdb sucks

 }; // class VM_PopulateDumpSharedSpace

 void VM_PopulateDumpSharedSpace::doit() {

   Thread* THREAD = VMThread::vm_thread();

   NOT_PRODUCT(SystemDictionary::verify();)

   // The following guarantee is meant to ensure that no loader constraints

   // exist yet, since the constraints table is not shared.  This becomes

   // more important now that we don't re-initialize vtables/itables for

   // shared classes at runtime, where constraints were previously created.

   guarantee(SystemDictionary::constraints()->number_of_entries() == 0,

             "loader constraints are not saved");

   guarantee(SystemDictionary::placeholders()->number_of_entries() == 0,

           "placeholders are not saved");

   // Revisit and implement this if we prelink method handle call sites:

   guarantee(SystemDictionary::invoke_method_table() == NULL ||

             SystemDictionary::invoke_method_table()->number_of_entries() == 0,

             "invoke method table is not saved");

   // At this point, many classes have been loaded.

   // Gather systemDictionary classes in a global array and do everything to

   // that so we don't have to walk the SystemDictionary again.

   _global_klass_objects = new GrowableArray<Klass*>(1000);

   Universe::basic_type_classes_do(collect_classes);

   SystemDictionary::classes_do(collect_classes);

   tty->print_cr("Number of classes %d", _global_klass_objects->length());

   // Update all the fingerprints in the shared methods.

   tty->print("Calculating fingerprints ... ");

   calculate_fingerprints();

   tty->print_cr("done. ");

   // Remove all references outside the metadata

   tty->print("Removing unshareable information ... ");

   remove_unshareable_in_classes();

   tty->print_cr("done. ");

   // Set up the share data and shared code segments.

   char* md_low = _md_vs.low();

   char* md_top = md_low;

   char* md_end = _md_vs.high();

   char* mc_low = _mc_vs.low();

   char* mc_top = mc_low;

   char* mc_end = _mc_vs.high();

   // Reserve space for the list of Klass*s whose vtables are used

   // for patching others as needed.

   void** vtbl_list = (void**)md_top;

   int vtbl_list_size = MetaspaceShared::vtbl_list_size;

   Universe::init_self_patching_vtbl_list(vtbl_list, vtbl_list_size);

   md_top += vtbl_list_size * sizeof(void*);

   void* vtable = md_top;

   // Reserve space for a new dummy vtable for klass objects in the

   // heap.  Generate self-patching vtable entries.

   MetaspaceShared::generate_vtable_methods(vtbl_list, &vtable,

                                      &md_top, md_end,

                                      &mc_top, mc_end);

   // Reorder the system dictionary.  (Moving the symbols affects

   // how the hash table indices are calculated.)

   // Not doing this either.

   SystemDictionary::reorder_dictionary();

   NOT_PRODUCT(SystemDictionary::verify();)

   // Copy the the symbol table, and the system dictionary to the shared

   // space in usable form.  Copy the hastable

   // buckets first [read-write], then copy the linked lists of entries

   // [read-only].

   SymbolTable::reverse(md_top);

   NOT_PRODUCT(SymbolTable::verify());

   SymbolTable::copy_buckets(&md_top, md_end);

   SystemDictionary::reverse();

   SystemDictionary::copy_buckets(&md_top, md_end);

   ClassLoader::verify();

   ClassLoader::copy_package_info_buckets(&md_top, md_end);

   ClassLoader::verify();

   SymbolTable::copy_table(&md_top, md_end);

   SystemDictionary::copy_table(&md_top, md_end);

   ClassLoader::verify();

   ClassLoader::copy_package_info_table(&md_top, md_end);

   ClassLoader::verify();

   // Write the other data to the output array.

   WriteClosure wc(md_top, md_end);

   MetaspaceShared::serialize(&wc);

   md_top = wc.get_top();

   // Print shared spaces all the time

   const char* fmt = "%s space: " PTR_FORMAT " out of " PTR_FORMAT " words allocated at " PTR_FORMAT ".";

   Metaspace* ro_space = _loader_data->ro_metaspace();

   Metaspace* rw_space = _loader_data->rw_metaspace();

   tty->print_cr(fmt, "ro", ro_space->used_words(Metaspace::NonClassType),

                 ro_space->capacity_words(Metaspace::NonClassType),

                 ro_space->bottom());

   tty->print_cr(fmt, "rw", rw_space->used_words(Metaspace::NonClassType),

                 rw_space->capacity_words(Metaspace::NonClassType),

                 rw_space->bottom());

   tty->print_cr(fmt, "md", md_top - md_low, md_end-md_low, md_low);

   tty->print_cr(fmt, "mc", mc_top - mc_low, mc_end-mc_low, mc_low);

   // Update the vtable pointers in all of the Klass objects in the

   // heap. They should point to newly generated vtable.

   patch_klass_vtables(vtbl_list, vtable);

   // dunno what this is for.

   char* saved_vtbl = (char*)os::malloc(vtbl_list_size * sizeof(void*), mtClass);

   memmove(saved_vtbl, vtbl_list, vtbl_list_size * sizeof(void*));

   memset(vtbl_list, 0, vtbl_list_size * sizeof(void*));

   // Create and write the archive file that maps the shared spaces.

   FileMapInfo* mapinfo = new FileMapInfo();

   mapinfo->populate_header(MetaspaceShared::max_alignment());

   // Pass 1 - update file offsets in header.

   mapinfo->write_header();

   mapinfo->write_space(MetaspaceShared::ro, _loader_data->ro_metaspace(), true);

   mapinfo->write_space(MetaspaceShared::rw, _loader_data->rw_metaspace(), false);

   mapinfo->write_region(MetaspaceShared::md, _md_vs.low(),

                         pointer_delta(md_top, _md_vs.low(), sizeof(char)),

                         SharedMiscDataSize,

                         false, false);

   mapinfo->write_region(MetaspaceShared::mc, _mc_vs.low(),

                         pointer_delta(mc_top, _mc_vs.low(), sizeof(char)),

                         SharedMiscCodeSize,

                         true, true);

   // Pass 2 - write data.

   mapinfo->open_for_write();

   mapinfo->write_header();

   mapinfo->write_space(MetaspaceShared::ro, _loader_data->ro_metaspace(), true);

   mapinfo->write_space(MetaspaceShared::rw, _loader_data->rw_metaspace(), false);

   mapinfo->write_region(MetaspaceShared::md, _md_vs.low(),

                         pointer_delta(md_top, _md_vs.low(), sizeof(char)),

                         SharedMiscDataSize,

                         false, false);

   mapinfo->write_region(MetaspaceShared::mc, _mc_vs.low(),

                         pointer_delta(mc_top, _mc_vs.low(), sizeof(char)),

                         SharedMiscCodeSize,

                         true, true);

   mapinfo->close();

   memmove(vtbl_list, saved_vtbl, vtbl_list_size * sizeof(void*));

 }

 static void link_shared_classes(Klass* obj, TRAPS) {

   Klass* k = Klass::cast(obj);

   if (k->oop_is_instance()) {

     InstanceKlass* ik = (InstanceKlass*) k;

     // Link the class to cause the bytecodes to be rewritten and the

     // cpcache to be created.

     if (ik->init_state() < InstanceKlass::linked) {

       ik->link_class(THREAD);

       guarantee(!HAS_PENDING_EXCEPTION, "exception in class rewriting");

     }

   }

 }

 // Support for a simple checksum of the contents of the class list

 // file to prevent trivial tampering. The algorithm matches that in

 // the MakeClassList program used by the J2SE build process.

 #define JSUM_SEED ((jlong)CONST64(0xcafebabebabecafe))

 static jlong

 jsum(jlong start, const char *buf, const int len)

 {

     jlong h = start;

     char *p = (char *)buf, *e = p + len;

     while (p < e) {

         char c = *p++;

         if (c <= ' ') {

             /* Skip spaces and control characters */

             continue;

         }

         h = 31 * h + c;

     }

     return h;

 }

 // Preload classes from a list, populate the shared spaces and dump to a

 // file.

 void MetaspaceShared::preload_and_dump(TRAPS) {

   TraceTime timer("Dump Shared Spaces", TraceStartupTime);

   ResourceMark rm;

   // Lock out GC - is it necessary? I don't think we care.

   No_GC_Verifier no_gc;

   // Preload classes to be shared.

   // Should use some os:: method rather than fopen() here. aB.

   // Construct the path to the class list (in jre/lib)

   // Walk up two directories from the location of the VM and

   // optionally tack on "lib" (depending on platform)

   char class_list_path[JVM_MAXPATHLEN];

   os::jvm_path(class_list_path, sizeof(class_list_path));

   for (int i = 0; i < 3; i++) {

     char *end = strrchr(class_list_path, *os::file_separator());

     if (end != NULL) *end = '\0';

   }

   int class_list_path_len = (int)strlen(class_list_path);

   if (class_list_path_len >= 3) {

     if (strcmp(class_list_path + class_list_path_len - 3, "lib") != 0) {

       strcat(class_list_path, os::file_separator());

       strcat(class_list_path, "lib");

     }

   }

   strcat(class_list_path, os::file_separator());

   strcat(class_list_path, "classlist");

   FILE* file = fopen(class_list_path, "r");

   if (file != NULL) {

     jlong computed_jsum  = JSUM_SEED;

     jlong file_jsum      = 0;

     char class_name[256];

     int class_count = 0;

     GrowableArray<Klass*>* class_promote_order = new GrowableArray<Klass*>();

     // sun.io.Converters

     static const char obj_array_sig[] = "[[Ljava/lang/Object;";

     SymbolTable::new_permanent_symbol(obj_array_sig, THREAD);

     // java.util.HashMap

     static const char map_entry_array_sig[] = "[Ljava/util/Map$Entry;";

     SymbolTable::new_permanent_symbol(map_entry_array_sig, THREAD);

     tty->print("Loading classes to share ... ");

     while ((fgets(class_name, sizeof class_name, file)) != NULL) {

       if (*class_name == '#') {

         jint fsh, fsl;

         if (sscanf(class_name, "# %8x%8x\n", &fsh, &fsl) == 2) {

           file_jsum = ((jlong)(fsh) << 32) | (fsl & 0xffffffff);

         }

         continue;

       }

       // Remove trailing newline

       size_t name_len = strlen(class_name);

       class_name[name_len-1] = '\0';

       computed_jsum = jsum(computed_jsum, class_name, (const int)name_len - 1);

       // Got a class name - load it.

       TempNewSymbol class_name_symbol = SymbolTable::new_permanent_symbol(class_name, THREAD);

       guarantee(!HAS_PENDING_EXCEPTION, "Exception creating a symbol.");

       Klass* klass = SystemDictionary::resolve_or_null(class_name_symbol,

                                                          THREAD);

       guarantee(!HAS_PENDING_EXCEPTION, "Exception resolving a class.");

       if (klass != NULL) {

         if (PrintSharedSpaces && Verbose && WizardMode) {

           tty->print_cr("Shared spaces preloaded: %s", class_name);

         }

         InstanceKlass* ik = InstanceKlass::cast(klass);

         // Should be class load order as per -XX:+TraceClassLoadingPreorder

         class_promote_order->append(ik);

         // Link the class to cause the bytecodes to be rewritten and the

         // cpcache to be created. The linking is done as soon as classes

         // are loaded in order that the related data structures (klass and

         // cpCache) are located together.

         if (ik->init_state() < InstanceKlass::linked) {

           ik->link_class(THREAD);

           guarantee(!(HAS_PENDING_EXCEPTION), "exception in class rewriting");

         }

         // TODO: Resolve klasses in constant pool

         ik->constants()->resolve_class_constants(THREAD);

         class_count++;

       } else {

         if (PrintSharedSpaces && Verbose && WizardMode) {

           tty->cr();

           tty->print_cr(" Preload failed: %s", class_name);

         }

       }

       file_jsum = 0; // Checksum must be on last line of file

     }

     if (computed_jsum != file_jsum) {

       tty->cr();

       tty->print_cr("Preload failed: checksum of class list was incorrect.");

       exit(1);

     }

     tty->print_cr("done. ");

     if (PrintSharedSpaces) {

       tty->print_cr("Shared spaces: preloaded %d classes", class_count);

     }

     // Rewrite and unlink classes.

     tty->print("Rewriting and linking classes ... ");

     // Link any classes which got missed.  (It's not quite clear why

     // they got missed.)  This iteration would be unsafe if we weren't

     // single-threaded at this point; however we can't do it on the VM

     // thread because it requires object allocation.

     SystemDictionary::classes_do(link_shared_classes, CATCH);

     tty->print_cr("done. ");

     // Create and dump the shared spaces.   Everything so far is loaded

     // with the null class loader.

     ClassLoaderData* loader_data = ClassLoaderData::the_null_class_loader_data();

     VM_PopulateDumpSharedSpace op(loader_data, class_promote_order);

     VMThread::execute(&op);

   } else {

     char errmsg[JVM_MAXPATHLEN];

     os::lasterror(errmsg, JVM_MAXPATHLEN);

     tty->print_cr("Loading classlist failed: %s", errmsg);

     exit(1);

   }

   // Since various initialization steps have been undone by this process,

   // it is not reasonable to continue running a java process.

   exit(0);

 }

 // Closure for serializing initialization data in from a data area

 // (ptr_array) read from the shared file.

 class ReadClosure : public SerializeClosure {

 private:

   intptr_t** _ptr_array;

   inline intptr_t nextPtr() {

     return *(*_ptr_array)++;

   }

 public:

   ReadClosure(intptr_t** ptr_array) { _ptr_array = ptr_array; }

   void do_ptr(void** p) {

     assert(*p == NULL, "initializing previous initialized pointer.");

     intptr_t obj = nextPtr();

     assert((intptr_t)obj >= 0 || (intptr_t)obj < -100,

            "hit tag while initializing ptrs.");

     *p = (void*)obj;

   }

   void do_tag(int tag) {

     int old_tag;

     old_tag = (int)(intptr_t)nextPtr();

     // do_int(&old_tag);

     assert(tag == old_tag, "old tag doesn't match");

     FileMapInfo::assert_mark(tag == old_tag);

   }

   void do_region(u_char* start, size_t size) {

     assert((intptr_t)start % sizeof(intptr_t) == 0, "bad alignment");

     assert(size % sizeof(intptr_t) == 0, "bad size");

     do_tag((int)size);

     while (size > 0) {

       *(intptr_t*)start = nextPtr();

       start += sizeof(intptr_t);

       size -= sizeof(intptr_t);

     }

   }

   bool reading() const { return true; }

 };

 // Save bounds of shared spaces mapped in.

 static char* _ro_base = NULL;

 static char* _rw_base = NULL;

 static char* _md_base = NULL;

 static char* _mc_base = NULL;

 // Return true if given address is in the mapped shared space.

 bool MetaspaceShared::is_in_shared_space(const void* p) {

   if (_ro_base == NULL || _rw_base == NULL) {

     return false;

   } else {

     return ((p > _ro_base && p < (_ro_base + SharedReadOnlySize)) ||

             (p > _rw_base && p < (_rw_base + SharedReadWriteSize)));

   }

 }

 void MetaspaceShared::print_shared_spaces() {

   gclog_or_tty->print_cr("Shared Spaces:");

   gclog_or_tty->print("  read-only " INTPTR_FORMAT "-" INTPTR_FORMAT,

     _ro_base, _ro_base + SharedReadOnlySize);

   gclog_or_tty->print("  read-write " INTPTR_FORMAT "-" INTPTR_FORMAT,

     _rw_base, _rw_base + SharedReadWriteSize);

   gclog_or_tty->cr();

   gclog_or_tty->print("  misc-data " INTPTR_FORMAT "-" INTPTR_FORMAT,

     _md_base, _md_base + SharedMiscDataSize);

   gclog_or_tty->print("  misc-code " INTPTR_FORMAT "-" INTPTR_FORMAT,

     _mc_base, _mc_base + SharedMiscCodeSize);

   gclog_or_tty->cr();

 }

 // Map shared spaces at requested addresses and return if succeeded.

 // Need to keep the bounds of the ro and rw space for the Metaspace::contains

 // call, or is_in_shared_space.

 bool MetaspaceShared::map_shared_spaces(FileMapInfo* mapinfo) {

   size_t image_alignment = mapinfo->alignment();

   // Map in the shared memory and then map the regions on top of it

   ReservedSpace shared_rs = mapinfo->reserve_shared_memory();

   if (!shared_rs.is_reserved()) return false;

   // Split reserved memory into pieces (windows needs this)

   ReservedSpace ro_rs   = shared_rs.first_part(SharedReadOnlySize);

   ReservedSpace tmp_rs1 = shared_rs.last_part(SharedReadOnlySize);

   ReservedSpace rw_rs   = tmp_rs1.first_part(SharedReadWriteSize);

   ReservedSpace tmp_rs2 = tmp_rs1.last_part(SharedReadWriteSize);

   ReservedSpace md_rs   = tmp_rs2.first_part(SharedMiscDataSize);

   ReservedSpace mc_rs   = tmp_rs2.last_part(SharedMiscDataSize);

   // Map each shared region

   if ((_ro_base = mapinfo->map_region(ro)) != NULL &&

       (_rw_base = mapinfo->map_region(rw)) != NULL &&

       (_md_base = mapinfo->map_region(md)) != NULL &&

       (_mc_base = mapinfo->map_region(mc)) != NULL &&

       (image_alignment == (size_t)max_alignment())) {

     // Success (no need to do anything)

     return true;

   } else {

     // If there was a failure in mapping any of the spaces, unmap the ones

     // that succeeded

     if (_ro_base != NULL) mapinfo->unmap_region(ro);

     if (_rw_base != NULL) mapinfo->unmap_region(rw);

     if (_md_base != NULL) mapinfo->unmap_region(md);

     if (_mc_base != NULL) mapinfo->unmap_region(mc);

     // Release the entire mapped region

     shared_rs.release();

     // If -Xshare:on is specified, print out the error message and exit VM,

     // otherwise, set UseSharedSpaces to false and continue.

     if (RequireSharedSpaces) {

       vm_exit_during_initialization("Unable to use shared archive.", NULL);

     } else {

       FLAG_SET_DEFAULT(UseSharedSpaces, false);

     }

     return false;

   }

 }

 // Read the miscellaneous data from the shared file, and

 // serialize it out to its various destinations.

 void MetaspaceShared::initialize_shared_spaces() {

   FileMapInfo *mapinfo = FileMapInfo::current_info();

   char* buffer = mapinfo->region_base(md);

   // Skip over (reserve space for) a list of addresses of C++ vtables

   // for Klass objects.  They get filled in later.

   void** vtbl_list = (void**)buffer;

   buffer += MetaspaceShared::vtbl_list_size * sizeof(void*);

   Universe::init_self_patching_vtbl_list(vtbl_list, vtbl_list_size);

   // Skip over (reserve space for) dummy C++ vtables Klass objects.

   // They are used as is.

   intptr_t vtable_size = *(intptr_t*)buffer;

   buffer += sizeof(intptr_t);

   buffer += vtable_size;

   // Create the symbol table using the bucket array at this spot in the

   // misc data space.  Since the symbol table is often modified, this

   // region (of mapped pages) will be copy-on-write.

   int symbolTableLen = *(intptr_t*)buffer;

   buffer += sizeof(intptr_t);

   int number_of_entries = *(intptr_t*)buffer;

   buffer += sizeof(intptr_t);

   SymbolTable::create_table((HashtableBucket<mtSymbol>*)buffer, symbolTableLen,

                             number_of_entries);

   buffer += symbolTableLen;

   // Create the shared dictionary using the bucket array at this spot in

   // the misc data space.  Since the shared dictionary table is never

   // modified, this region (of mapped pages) will be (effectively, if

   // not explicitly) read-only.

   int sharedDictionaryLen = *(intptr_t*)buffer;

   buffer += sizeof(intptr_t);

   number_of_entries = *(intptr_t*)buffer;

   buffer += sizeof(intptr_t);

   SystemDictionary::set_shared_dictionary((HashtableBucket<mtClass>*)buffer,

                                           sharedDictionaryLen,

                                           number_of_entries);

   buffer += sharedDictionaryLen;

   // Create the package info table using the bucket array at this spot in

   // the misc data space.  Since the package info table is never

   // modified, this region (of mapped pages) will be (effectively, if

   // not explicitly) read-only.

   int pkgInfoLen = *(intptr_t*)buffer;

   buffer += sizeof(intptr_t);

   number_of_entries = *(intptr_t*)buffer;

   buffer += sizeof(intptr_t);

   ClassLoader::create_package_info_table((HashtableBucket<mtClass>*)buffer, pkgInfoLen,

                                          number_of_entries);

   buffer += pkgInfoLen;

   ClassLoader::verify();

   // The following data in the shared misc data region are the linked

   // list elements (HashtableEntry objects) for the symbol table, string

   // table, and shared dictionary.  The heap objects refered to by the

   // symbol table, string table, and shared dictionary are permanent and

   // unmovable.  Since new entries added to the string and symbol tables

   // are always added at the beginning of the linked lists, THESE LINKED

   // LIST ELEMENTS ARE READ-ONLY.

   int len = *(intptr_t*)buffer; // skip over symbol table entries

   buffer += sizeof(intptr_t);

   buffer += len;

   len = *(intptr_t*)buffer;     // skip over shared dictionary entries

   buffer += sizeof(intptr_t);

   buffer += len;

   len = *(intptr_t*)buffer;     // skip over package info table entries

   buffer += sizeof(intptr_t);

   buffer += len;

   len = *(intptr_t*)buffer;     // skip over package info table char[] arrays.

   buffer += sizeof(intptr_t);

   buffer += len;

   intptr_t* array = (intptr_t*)buffer;

   ReadClosure rc(&array);

   serialize(&rc);

   // Close the mapinfo file

   mapinfo->close();

 }

 // JVM/TI RedefineClasses() support:

 bool MetaspaceShared::remap_shared_readonly_as_readwrite() {

   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");

   if (UseSharedSpaces) {

     // remap the shared readonly space to shared readwrite, private

     FileMapInfo* mapinfo = FileMapInfo::current_info();

     if (!mapinfo->remap_shared_readonly_as_readwrite()) {

       return false;

     }

   }

   return true;

 }