jdk

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/*
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 * Copyright (c) 2020, 2023, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 *
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 */
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#include "precompiled.hpp"
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#include "cds/archiveUtils.hpp"
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#include "cds/archiveBuilder.hpp"
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#include "cds/cdsConfig.hpp"
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#include "cds/cppVtables.hpp"
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#include "cds/metaspaceShared.hpp"
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#include "logging/log.hpp"
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#include "oops/instanceClassLoaderKlass.hpp"
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#include "oops/instanceMirrorKlass.hpp"
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#include "oops/instanceRefKlass.hpp"
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#include "oops/instanceStackChunkKlass.hpp"
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#include "oops/methodData.hpp"
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#include "oops/objArrayKlass.hpp"
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#include "oops/typeArrayKlass.hpp"
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#include "runtime/arguments.hpp"
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#include "utilities/globalDefinitions.hpp"
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// Objects of the Metadata types (such as Klass and ConstantPool) have C++ vtables.
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// (In GCC this is the field <Type>::_vptr, i.e., first word in the object.)
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//
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// Addresses of the vtables and the methods may be different across JVM runs,
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// if libjvm.so is dynamically loaded at a different base address.
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//
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// To ensure that the Metadata objects in the CDS archive always have the correct vtable:
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//
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// + at dump time:  we redirect the _vptr to point to our own vtables inside
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//                  the CDS image
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// + at run time:   we clone the actual contents of the vtables from libjvm.so
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//                  into our own tables.
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// Currently, the archive contains ONLY the following types of objects that have C++ vtables.
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#define CPP_VTABLE_TYPES_DO(f) \
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  f(ConstantPool) \
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  f(InstanceKlass) \
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  f(InstanceClassLoaderKlass) \
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  f(InstanceMirrorKlass) \
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  f(InstanceRefKlass) \
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  f(InstanceStackChunkKlass) \
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  f(Method) \
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  f(ObjArrayKlass) \
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  f(TypeArrayKlass)
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class CppVtableInfo {
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  intptr_t _vtable_size;
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  intptr_t _cloned_vtable[1]; // Pseudo flexible array member.
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  static size_t cloned_vtable_offset() { return offset_of(CppVtableInfo, _cloned_vtable); }
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public:
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  int vtable_size()           { return int(uintx(_vtable_size)); }
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  void set_vtable_size(int n) { _vtable_size = intptr_t(n); }
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  // Using _cloned_vtable[i] for i > 0 causes undefined behavior. We use address calculation instead.
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  intptr_t* cloned_vtable()   { return (intptr_t*)((char*)this + cloned_vtable_offset()); }
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  void zero()                 { memset(cloned_vtable(), 0, sizeof(intptr_t) * vtable_size()); }
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  // Returns the address of the next CppVtableInfo that can be placed immediately after this CppVtableInfo
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  static size_t byte_size(int vtable_size) {
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    return cloned_vtable_offset() + (sizeof(intptr_t) * vtable_size);
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  }
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};
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static inline intptr_t* vtable_of(const Metadata* m) {
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  return *((intptr_t**)m);
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}
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template <class T> class CppVtableCloner {
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  static int get_vtable_length(const char* name);
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public:
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  // Allocate a clone of the vtable of T from the shared metaspace;
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  // Initialize the contents of this clone.
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  static CppVtableInfo* allocate_and_initialize(const char* name);
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  // Copy the contents of the vtable of T into info->_cloned_vtable;
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  static void initialize(const char* name, CppVtableInfo* info);
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  static void init_orig_cpp_vtptr(int kind);
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};
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template <class T>
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CppVtableInfo* CppVtableCloner<T>::allocate_and_initialize(const char* name) {
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  int n = get_vtable_length(name);
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  CppVtableInfo* info =
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      (CppVtableInfo*)ArchiveBuilder::current()->rw_region()->allocate(CppVtableInfo::byte_size(n));
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  info->set_vtable_size(n);
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  initialize(name, info);
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  return info;
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}
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template <class T>
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void CppVtableCloner<T>::initialize(const char* name, CppVtableInfo* info) {
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  T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
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  int n = info->vtable_size();
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  intptr_t* srcvtable = vtable_of(&tmp);
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  intptr_t* dstvtable = info->cloned_vtable();
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  // We already checked (and, if necessary, adjusted n) when the vtables were allocated, so we are
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  // safe to do memcpy.
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  log_debug(cds, vtables)("Copying %3d vtable entries for %s", n, name);
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  memcpy(dstvtable, srcvtable, sizeof(intptr_t) * n);
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}
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// To determine the size of the vtable for each type, we use the following
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// trick by declaring 2 subclasses:
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//
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//   class CppVtableTesterA: public InstanceKlass {virtual int   last_virtual_method() {return 1;}    };
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//   class CppVtableTesterB: public InstanceKlass {virtual void* last_virtual_method() {return nullptr}; };
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//
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// CppVtableTesterA and CppVtableTesterB's vtables have the following properties:
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// - Their size (N+1) is exactly one more than the size of InstanceKlass's vtable (N)
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// - The first N entries have are exactly the same as in InstanceKlass's vtable.
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// - Their last entry is different.
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//
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// So to determine the value of N, we just walk CppVtableTesterA and CppVtableTesterB's tables
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// and find the first entry that's different.
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//
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// This works on all C++ compilers supported by Oracle, but you may need to tweak it for more
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// esoteric compilers.
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template <class T> class CppVtableTesterB: public T {
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public:
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  virtual int last_virtual_method() {return 1;}
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};
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template <class T> class CppVtableTesterA : public T {
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public:
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  virtual void* last_virtual_method() {
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    // Make this different than CppVtableTesterB::last_virtual_method so the C++
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    // compiler/linker won't alias the two functions.
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    return nullptr;
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  }
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};
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template <class T>
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int CppVtableCloner<T>::get_vtable_length(const char* name) {
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  CppVtableTesterA<T> a;
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  CppVtableTesterB<T> b;
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  intptr_t* avtable = vtable_of(&a);
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  intptr_t* bvtable = vtable_of(&b);
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  // Start at slot 1, because slot 0 may be RTTI (on Solaris/Sparc)
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  int vtable_len = 1;
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  for (; ; vtable_len++) {
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    if (avtable[vtable_len] != bvtable[vtable_len]) {
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      break;
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    }
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  }
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  log_debug(cds, vtables)("Found   %3d vtable entries for %s", vtable_len, name);
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  return vtable_len;
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}
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#define ALLOCATE_AND_INITIALIZE_VTABLE(c) \
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  _index[c##_Kind] = CppVtableCloner<c>::allocate_and_initialize(#c); \
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  ArchivePtrMarker::mark_pointer(&_index[c##_Kind]);
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#define INITIALIZE_VTABLE(c) \
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  CppVtableCloner<c>::initialize(#c, _index[c##_Kind]);
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#define INIT_ORIG_CPP_VTPTRS(c) \
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  CppVtableCloner<c>::init_orig_cpp_vtptr(c##_Kind);
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#define DECLARE_CLONED_VTABLE_KIND(c) c ## _Kind,
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enum ClonedVtableKind {
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  // E.g., ConstantPool_Kind == 0, InstanceKlass_Kind == 1, etc.
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  CPP_VTABLE_TYPES_DO(DECLARE_CLONED_VTABLE_KIND)
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  _num_cloned_vtable_kinds
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};
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// This is a map of all the original vtptrs. E.g., for
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//     ConstantPool *cp = new (...) ConstantPool(...) ; // a dynamically allocated constant pool
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// the following holds true:
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//     _orig_cpp_vtptrs[ConstantPool_Kind] ==  ((intptr_t**)cp)[0]
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static intptr_t* _orig_cpp_vtptrs[_num_cloned_vtable_kinds];
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static bool _orig_cpp_vtptrs_inited = false;
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template <class T>
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void CppVtableCloner<T>::init_orig_cpp_vtptr(int kind) {
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  assert(kind < _num_cloned_vtable_kinds, "sanity");
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  T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
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  intptr_t* srcvtable = vtable_of(&tmp);
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  _orig_cpp_vtptrs[kind] = srcvtable;
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}
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// This is the index of all the cloned vtables. E.g., for
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//     ConstantPool* cp = ....; // an archived constant pool
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//     InstanceKlass* ik = ....;// an archived class
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// the following holds true:
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//     _index[ConstantPool_Kind]->cloned_vtable()  == ((intptr_t**)cp)[0]
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//     _index[InstanceKlass_Kind]->cloned_vtable() == ((intptr_t**)ik)[0]
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static CppVtableInfo* _index[_num_cloned_vtable_kinds];
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// Vtables are all fixed offsets from ArchiveBuilder::current()->mapped_base()
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// E.g. ConstantPool is at offset 0x58. We can archive these offsets in the
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// RO region and use them to alculate their location at runtime without storing
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// the pointers in the RW region
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char* CppVtables::_vtables_serialized_base = nullptr;
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void CppVtables::dumptime_init(ArchiveBuilder* builder) {
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  assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
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  CPP_VTABLE_TYPES_DO(ALLOCATE_AND_INITIALIZE_VTABLE);
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  size_t cpp_tables_size = builder->rw_region()->top() - builder->rw_region()->base();
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  builder->alloc_stats()->record_cpp_vtables((int)cpp_tables_size);
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}
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void CppVtables::serialize(SerializeClosure* soc) {
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  if (!soc->reading()) {
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    _vtables_serialized_base = (char*)ArchiveBuilder::current()->buffer_top();
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  }
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  for (int i = 0; i < _num_cloned_vtable_kinds; i++) {
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    soc->do_ptr(&_index[i]);
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  }
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  if (soc->reading()) {
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    CPP_VTABLE_TYPES_DO(INITIALIZE_VTABLE);
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  }
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}
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intptr_t* CppVtables::get_archived_vtable(MetaspaceObj::Type msotype, address obj) {
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  if (!_orig_cpp_vtptrs_inited) {
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    CPP_VTABLE_TYPES_DO(INIT_ORIG_CPP_VTPTRS);
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    _orig_cpp_vtptrs_inited = true;
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  }
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  assert(CDSConfig::is_dumping_archive(), "sanity");
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  int kind = -1;
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  switch (msotype) {
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  case MetaspaceObj::SymbolType:
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  case MetaspaceObj::TypeArrayU1Type:
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  case MetaspaceObj::TypeArrayU2Type:
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  case MetaspaceObj::TypeArrayU4Type:
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  case MetaspaceObj::TypeArrayU8Type:
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  case MetaspaceObj::TypeArrayOtherType:
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  case MetaspaceObj::ConstMethodType:
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  case MetaspaceObj::ConstantPoolCacheType:
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  case MetaspaceObj::AnnotationsType:
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  case MetaspaceObj::MethodCountersType:
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  case MetaspaceObj::SharedClassPathEntryType:
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  case MetaspaceObj::RecordComponentType:
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    // These have no vtables.
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    break;
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  case MetaspaceObj::MethodDataType:
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    // We don't archive MethodData <-- should have been removed in removed_unsharable_info
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    ShouldNotReachHere();
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    break;
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  default:
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    for (kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
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      if (vtable_of((Metadata*)obj) == _orig_cpp_vtptrs[kind]) {
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        break;
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      }
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    }
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    if (kind >= _num_cloned_vtable_kinds) {
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      fatal("Cannot find C++ vtable for " INTPTR_FORMAT " -- you probably added"
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            " a new subtype of Klass or MetaData without updating CPP_VTABLE_TYPES_DO or the cases in this 'switch' statement",
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            p2i(obj));
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    }
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  }
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  if (kind >= 0) {
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    assert(kind < _num_cloned_vtable_kinds, "must be");
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    return _index[kind]->cloned_vtable();
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  } else {
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    return nullptr;
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  }
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}
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void CppVtables::zero_archived_vtables() {
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  assert(CDSConfig::is_dumping_static_archive(), "cpp tables are only dumped into static archive");
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  for (int kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
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    _index[kind]->zero();
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  }
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}
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bool CppVtables::is_valid_shared_method(const Method* m) {
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  assert(MetaspaceShared::is_in_shared_metaspace(m), "must be");
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  return vtable_of(m) == _index[Method_Kind]->cloned_vtable();
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}
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