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/*
* Copyright (c) 2020, 2022, 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 "cds/archiveUtils.hpp"
#include "cds/archiveBuilder.hpp"
#include "cds/cppVtables.hpp"
#include "cds/metaspaceShared.hpp"
#include "logging/log.hpp"
#include "oops/instanceClassLoaderKlass.hpp"
#include "oops/instanceMirrorKlass.hpp"
#include "oops/instanceRefKlass.hpp"
#include "oops/instanceStackChunkKlass.hpp"
#include "oops/methodData.hpp"
#include "oops/objArrayKlass.hpp"
#include "oops/typeArrayKlass.hpp"
#include "runtime/arguments.hpp"
#include "utilities/globalDefinitions.hpp"
// Objects of the Metadata types (such as Klass and ConstantPool) have C++ vtables.
// (In GCC this is the field <Type>::_vptr, i.e., first word in the object.)
//
// Addresses of the vtables and the methods may be different across JVM runs,
// if libjvm.so is dynamically loaded at a different base address.
//
// To ensure that the Metadata objects in the CDS archive always have the correct vtable:
//
// + at dump time: we redirect the _vptr to point to our own vtables inside
// the CDS image
// + at run time: we clone the actual contents of the vtables from libjvm.so
// into our own tables.
// Currently, the archive contains ONLY the following types of objects that have C++ vtables.
#define CPP_VTABLE_TYPES_DO(f) \
f(ConstantPool) \
f(InstanceKlass) \
f(InstanceClassLoaderKlass) \
f(InstanceMirrorKlass) \
f(InstanceRefKlass) \
f(InstanceStackChunkKlass) \
f(Method) \
f(ObjArrayKlass) \
f(TypeArrayKlass)
class CppVtableInfo {
intptr_t _vtable_size;
intptr_t _cloned_vtable[1];
public:
static int num_slots(int vtable_size) {
return 1 + vtable_size; // Need to add the space occupied by _vtable_size;
}
int vtable_size() { return int(uintx(_vtable_size)); }
void set_vtable_size(int n) { _vtable_size = intptr_t(n); }
intptr_t* cloned_vtable() { return &_cloned_vtable[0]; }
void zero() { memset(_cloned_vtable, 0, sizeof(intptr_t) * vtable_size()); }
// Returns the address of the next CppVtableInfo that can be placed immediately after this CppVtableInfo
static size_t byte_size(int vtable_size) {
CppVtableInfo i;
return pointer_delta(&i._cloned_vtable[vtable_size], &i, sizeof(u1));
}
};
static inline intptr_t* vtable_of(const Metadata* m) {
return *((intptr_t**)m);
}
template <class T> class CppVtableCloner {
static int get_vtable_length(const char* name);
public:
// Allocate a clone of the vtable of T from the shared metaspace;
// Initialize the contents of this clone.
static CppVtableInfo* allocate_and_initialize(const char* name);
// Copy the contents of the vtable of T into info->_cloned_vtable;
static void initialize(const char* name, CppVtableInfo* info);
static void init_orig_cpp_vtptr(int kind);
};
template <class T>
CppVtableInfo* CppVtableCloner<T>::allocate_and_initialize(const char* name) {
int n = get_vtable_length(name);
CppVtableInfo* info =
(CppVtableInfo*)ArchiveBuilder::current()->rw_region()->allocate(CppVtableInfo::byte_size(n));
info->set_vtable_size(n);
initialize(name, info);
return info;
}
template <class T>
void CppVtableCloner<T>::initialize(const char* name, CppVtableInfo* info) {
T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
int n = info->vtable_size();
intptr_t* srcvtable = vtable_of(&tmp);
intptr_t* dstvtable = info->cloned_vtable();
// We already checked (and, if necessary, adjusted n) when the vtables were allocated, so we are
// safe to do memcpy.
log_debug(cds, vtables)("Copying %3d vtable entries for %s", n, name);
memcpy(dstvtable, srcvtable, sizeof(intptr_t) * n);
}
// To determine the size of the vtable for each type, we use the following
// trick by declaring 2 subclasses:
//
// class CppVtableTesterA: public InstanceKlass {virtual int last_virtual_method() {return 1;} };
// class CppVtableTesterB: public InstanceKlass {virtual void* last_virtual_method() {return NULL}; };
//
// CppVtableTesterA and CppVtableTesterB's vtables have the following properties:
// - Their size (N+1) is exactly one more than the size of InstanceKlass's vtable (N)
// - The first N entries have are exactly the same as in InstanceKlass's vtable.
// - Their last entry is different.
//
// So to determine the value of N, we just walk CppVtableTesterA and CppVtableTesterB's tables
// and find the first entry that's different.
//
// This works on all C++ compilers supported by Oracle, but you may need to tweak it for more
// esoteric compilers.
template <class T> class CppVtableTesterB: public T {
public:
virtual int last_virtual_method() {return 1;}
};
template <class T> class CppVtableTesterA : public T {
public:
virtual void* last_virtual_method() {
// Make this different than CppVtableTesterB::last_virtual_method so the C++
// compiler/linker won't alias the two functions.
return NULL;
}
};
template <class T>
int CppVtableCloner<T>::get_vtable_length(const char* name) {
CppVtableTesterA<T> a;
CppVtableTesterB<T> b;
intptr_t* avtable = vtable_of(&a);
intptr_t* bvtable = vtable_of(&b);
// Start at slot 1, because slot 0 may be RTTI (on Solaris/Sparc)
int vtable_len = 1;
for (; ; vtable_len++) {
if (avtable[vtable_len] != bvtable[vtable_len]) {
break;
}
}
log_debug(cds, vtables)("Found %3d vtable entries for %s", vtable_len, name);
return vtable_len;
}
#define ALLOCATE_AND_INITIALIZE_VTABLE(c) \
_index[c##_Kind] = CppVtableCloner<c>::allocate_and_initialize(#c); \
ArchivePtrMarker::mark_pointer(&_index[c##_Kind]);
#define INITIALIZE_VTABLE(c) \
CppVtableCloner<c>::initialize(#c, _index[c##_Kind]);
#define INIT_ORIG_CPP_VTPTRS(c) \
CppVtableCloner<c>::init_orig_cpp_vtptr(c##_Kind);
#define DECLARE_CLONED_VTABLE_KIND(c) c ## _Kind,
enum ClonedVtableKind {
// E.g., ConstantPool_Kind == 0, InstanceKlass_Kind == 1, etc.
CPP_VTABLE_TYPES_DO(DECLARE_CLONED_VTABLE_KIND)
_num_cloned_vtable_kinds
};
// This is a map of all the original vtptrs. E.g., for
// ConstantPool *cp = new (...) ConstantPool(...) ; // a dynamically allocated constant pool
// the following holds true:
// _orig_cpp_vtptrs[ConstantPool_Kind] == ((intptr_t**)cp)[0]
static intptr_t* _orig_cpp_vtptrs[_num_cloned_vtable_kinds];
static bool _orig_cpp_vtptrs_inited = false;
template <class T>
void CppVtableCloner<T>::init_orig_cpp_vtptr(int kind) {
assert(kind < _num_cloned_vtable_kinds, "sanity");
T tmp; // Allocate temporary dummy metadata object to get to the original vtable.
intptr_t* srcvtable = vtable_of(&tmp);
_orig_cpp_vtptrs[kind] = srcvtable;
}
// This is the index of all the cloned vtables. E.g., for
// ConstantPool* cp = ....; // an archived constant pool
// InstanceKlass* ik = ....;// an archived class
// the following holds true:
// _index[ConstantPool_Kind]->cloned_vtable() == ((intptr_t**)cp)[0]
// _index[InstanceKlass_Kind]->cloned_vtable() == ((intptr_t**)ik)[0]
CppVtableInfo** CppVtables::_index = NULL;
char* CppVtables::dumptime_init(ArchiveBuilder* builder) {
assert(DumpSharedSpaces, "must");
size_t vtptrs_bytes = _num_cloned_vtable_kinds * sizeof(CppVtableInfo*);
_index = (CppVtableInfo**)builder->rw_region()->allocate(vtptrs_bytes);
CPP_VTABLE_TYPES_DO(ALLOCATE_AND_INITIALIZE_VTABLE);
size_t cpp_tables_size = builder->rw_region()->top() - builder->rw_region()->base();
builder->alloc_stats()->record_cpp_vtables((int)cpp_tables_size);
return (char*)_index;
}
void CppVtables::serialize(SerializeClosure* soc) {
soc->do_ptr((void**)&_index);
if (soc->reading()) {
CPP_VTABLE_TYPES_DO(INITIALIZE_VTABLE);
}
}
intptr_t* CppVtables::get_archived_vtable(MetaspaceObj::Type msotype, address obj) {
if (!_orig_cpp_vtptrs_inited) {
CPP_VTABLE_TYPES_DO(INIT_ORIG_CPP_VTPTRS);
_orig_cpp_vtptrs_inited = true;
}
Arguments::assert_is_dumping_archive();
int kind = -1;
switch (msotype) {
case MetaspaceObj::SymbolType:
case MetaspaceObj::TypeArrayU1Type:
case MetaspaceObj::TypeArrayU2Type:
case MetaspaceObj::TypeArrayU4Type:
case MetaspaceObj::TypeArrayU8Type:
case MetaspaceObj::TypeArrayOtherType:
case MetaspaceObj::ConstMethodType:
case MetaspaceObj::ConstantPoolCacheType:
case MetaspaceObj::AnnotationsType:
case MetaspaceObj::MethodCountersType:
case MetaspaceObj::RecordComponentType:
// These have no vtables.
break;
case MetaspaceObj::MethodDataType:
// We don't archive MethodData <-- should have been removed in removed_unsharable_info
ShouldNotReachHere();
break;
default:
for (kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
if (vtable_of((Metadata*)obj) == _orig_cpp_vtptrs[kind]) {
break;
}
}
if (kind >= _num_cloned_vtable_kinds) {
fatal("Cannot find C++ vtable for " INTPTR_FORMAT " -- you probably added"
" a new subtype of Klass or MetaData without updating CPP_VTABLE_TYPES_DO",
p2i(obj));
}
}
if (kind >= 0) {
assert(kind < _num_cloned_vtable_kinds, "must be");
return _index[kind]->cloned_vtable();
} else {
return NULL;
}
}
void CppVtables::zero_archived_vtables() {
assert(DumpSharedSpaces, "dump-time only");
for (int kind = 0; kind < _num_cloned_vtable_kinds; kind ++) {
_index[kind]->zero();
}
}
bool CppVtables::is_valid_shared_method(const Method* m) {
assert(MetaspaceShared::is_in_shared_metaspace(m), "must be");
return vtable_of(m) == _index[Method_Kind]->cloned_vtable();
}
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