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/*
* Copyright (c) 1997, 2019, 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.
*
*/
#ifndef SHARE_CODE_STUBS_HPP
#define SHARE_CODE_STUBS_HPP
#include "asm/codeBuffer.hpp"
#include "memory/allocation.hpp"
class Mutex;
// The classes in this file provide a simple framework for the
// management of little pieces of machine code - or stubs -
// created on the fly and frequently discarded. In this frame-
// work stubs are stored in a queue.
// Stub serves as abstract base class. A concrete stub
// implementation is a subclass of Stub, implementing
// all (non-virtual!) functions required sketched out
// in the Stub class.
//
// A concrete stub layout may look like this (both data
// and code sections could be empty as well):
//
//
// stub -->|--------| <--+ <--- aligned by alignment()
// | | |
// | data | |
// | | |
// code_begin -->|--------| | <--- aligned by CodeEntryAlignment
// | | |
// | | |
// | code | | size
// | | |
// | | |
// code_end -->|--------| <--+
//
class Stub {
public:
// Initialization/finalization
void initialize(int size) { ShouldNotCallThis(); } // called to initialize/specify the stub's size
void finalize() { ShouldNotCallThis(); } // called before the stub is deallocated
// General info/converters
int size() const { ShouldNotCallThis(); return 0; } // must return the size provided by initialize
// Code info
address code_begin() const { ShouldNotCallThis(); return NULL; } // points to the first byte of the code
address code_end() const { ShouldNotCallThis(); return NULL; } // points to the first byte after the code
// Debugging
void verify() { ShouldNotCallThis(); } // verifies the Stub
void print() { ShouldNotCallThis(); } // prints some information about the stub
};
// A stub interface defines the interface between a stub queue
// and the stubs it queues. In order to avoid a vtable and
// (and thus the extra word) in each stub, a concrete stub
// interface object is created and associated with a stub
// buffer which in turn uses the stub interface to interact
// with its stubs.
//
// StubInterface serves as an abstract base class. A concrete
// stub interface implementation is a subclass of StubInterface,
// forwarding its virtual function calls to non-virtual calls
// of the concrete stub (see also macro below). There's exactly
// one stub interface instance required per stub queue.
class StubInterface: public CHeapObj<mtCode> {
public:
// Initialization/finalization
virtual void initialize(Stub* self, int size) = 0; // called after creation (called twice if allocated via (request, commit))
virtual void finalize(Stub* self) = 0; // called before deallocation
// General info/converters
virtual int size(Stub* self) const = 0; // the total size of the stub in bytes (must be a multiple of HeapWordSize)
virtual int alignment() const = 0; // computes the alignment
// Code info
virtual address code_begin(Stub* self) const = 0; // points to the first code byte
virtual address code_end(Stub* self) const = 0; // points to the first byte after the code
// Debugging
virtual void verify(Stub* self) = 0; // verifies the stub
virtual void print(Stub* self) = 0; // prints information about the stub
};
// DEF_STUB_INTERFACE is used to create a concrete stub interface
// class, forwarding stub interface calls to the corresponding
// stub calls.
#define DEF_STUB_INTERFACE(stub) \
class stub##Interface: public StubInterface { \
private: \
static stub* cast(Stub* self) { return (stub*)self; } \
\
public: \
/* Initialization/finalization */ \
virtual void initialize(Stub* self, int size) { cast(self)->initialize(size); } \
virtual void finalize(Stub* self) { cast(self)->finalize(); } \
\
/* General info */ \
virtual int size(Stub* self) const { return cast(self)->size(); } \
virtual int alignment() const { return stub::alignment(); } \
\
/* Code info */ \
virtual address code_begin(Stub* self) const { return cast(self)->code_begin(); } \
virtual address code_end(Stub* self) const { return cast(self)->code_end(); } \
\
/* Debugging */ \
virtual void verify(Stub* self) { cast(self)->verify(); } \
virtual void print(Stub* self) { cast(self)->print(); } \
};
// A StubQueue maintains a queue of stubs.
// Note: All sizes (spaces) are given in bytes.
class StubQueue: public CHeapObj<mtCode> {
friend class VMStructs;
private:
StubInterface* _stub_interface; // the interface prototype
address _stub_buffer; // where all stubs are stored
int _buffer_size; // the buffer size in bytes
int _buffer_limit; // the (byte) index of the actual buffer limit (_buffer_limit <= _buffer_size)
int _queue_begin; // the (byte) index of the first queue entry (word-aligned)
int _queue_end; // the (byte) index of the first entry after the queue (word-aligned)
int _number_of_stubs; // the number of buffered stubs
Mutex* const _mutex; // the lock used for a (request, commit) transaction
void check_index(int i) const { assert(0 <= i && i < _buffer_limit && i % stub_alignment() == 0, "illegal index"); }
bool is_contiguous() const { return _queue_begin <= _queue_end; }
int index_of(Stub* s) const { int i = (address)s - _stub_buffer; check_index(i); return i; }
Stub* stub_at(int i) const { check_index(i); return (Stub*)(_stub_buffer + i); }
Stub* current_stub() const { return stub_at(_queue_end); }
// Stub functionality accessed via interface
void stub_initialize(Stub* s, int size) { assert(size % stub_alignment() == 0, "size not aligned"); _stub_interface->initialize(s, size); }
void stub_finalize(Stub* s) { _stub_interface->finalize(s); }
int stub_size(Stub* s) const { return _stub_interface->size(s); }
bool stub_contains(Stub* s, address pc) const { return _stub_interface->code_begin(s) <= pc && pc < _stub_interface->code_end(s); }
int stub_alignment() const { return _stub_interface->alignment(); }
address stub_code_begin(Stub* s) const { return _stub_interface->code_begin(s); }
void stub_verify(Stub* s) { _stub_interface->verify(s); }
void stub_print(Stub* s) { _stub_interface->print(s); }
// Helpers
int compute_stub_size(Stub* stub, int code_size);
public:
StubQueue(StubInterface* stub_interface, int buffer_size, Mutex* lock,
const char* name);
~StubQueue();
// General queue info
bool is_empty() const { return _queue_begin == _queue_end; }
int total_space() const { return _buffer_size - 1; }
int available_space() const { int d = _queue_begin - _queue_end - 1; return d < 0 ? d + _buffer_size : d; }
int used_space() const { return total_space() - available_space(); }
int number_of_stubs() const { return _number_of_stubs; }
bool contains(address pc) const { return _stub_buffer <= pc && pc < _stub_buffer + _buffer_limit; }
Stub* stub_containing(address pc) const;
address code_start() const { return _stub_buffer; }
address code_end() const { return _stub_buffer + _buffer_limit; }
// Stub allocation (atomic transactions)
Stub* request_committed(int code_size); // request a stub that provides exactly code_size space for code
Stub* request(int requested_code_size); // request a stub with a (maximum) code space - locks the queue
void commit (int committed_code_size); // commit the previously requested stub - unlocks the queue
// Stub deallocation
void remove_first(); // remove the first stub in the queue
void remove_first(int n); // remove the first n stubs in the queue
void remove_all(); // remove all stubs in the queue
void deallocate_unused_tail(); // deallocate the unused tail of the underlying CodeBlob
// only used from TemplateInterpreter::initialize()
// Iteration
Stub* first() const { return number_of_stubs() > 0 ? stub_at(_queue_begin) : NULL; }
Stub* next(Stub* s) const { int i = index_of(s) + stub_size(s);
// Only wrap around in the non-contiguous case (see stubss.cpp)
if (i == _buffer_limit && _queue_end < _buffer_limit) i = 0;
return (i == _queue_end) ? NULL : stub_at(i);
}
// Debugging/printing
void verify(); // verifies the stub queue
void print(); // prints information about the stub queue
};
#endif // SHARE_CODE_STUBS_HPP
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