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104 lines
3.5 KiB
C++
104 lines
3.5 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* $URL$
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* $Id$
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*
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*/
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#if defined(DYNAMIC_MODULES) && defined(MIPS_TARGET)
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#ifndef SHORTS_SEGMENT_MANAGER_H
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#define SHORTS_SEGMENT_MANAGER_H
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#include "backends/plugins/elf32.h"
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#include "common/singleton.h"
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#include "common/list.h"
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#define ShortsMan ShortSegmentManager::instance()
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/**
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* ShortSegmentManager
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*
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* Since MIPS is limited to 32 bits per instruction, loading data that's further away than 16 bits
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* takes several instructions. Thus, small global data (which is likely to be accessed a lot from
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* multiple locations) is often put into a GP-relative area (GP standing for the global pointer register)
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* in MIPS processors. This class manages these segments of small global data, and is used by the
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* member functions of MIPSDLObject, which query in information from this manager in order to deal with
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* this segment during the loading/unloading of plugins.
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*
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* Since there's no true dynamic linker to change the GP register between plugins and the main engine,
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* custom ld linker scripts for both the main executable and the plugins ensure the GP-area is in the
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* same place for both. The ShortSegmentManager accesses this place via the symbols __plugin_hole_start
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* and __plugin_hole_end, which are defined in those custom ld linker scripts.
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*/
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class ShortSegmentManager : public Common::Singleton<ShortSegmentManager> {
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private:
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char *_shortsStart;
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char *_shortsEnd;
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public:
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char *getShortsStart() {
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return _shortsStart;
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}
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// Returns whether or not an absolute address is in the GP-relative section.
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bool inGeneralSegment(char *addr) {
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return ((char *)addr >= _shortsStart && (char *)addr < _shortsEnd);
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}
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class Segment {
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private:
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friend class ShortSegmentManager;
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Segment(char *start, int size, char *origAddr) : _startAddress(start), _size(size), _origAddress(origAddr) {}
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~Segment() {}
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char *_startAddress; // Start of shorts segment in memory
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int _size; // Size of shorts segment
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char *_origAddress; // Original address this segment was supposed to be at
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public:
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char *getStart() {
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return _startAddress;
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}
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char *getEnd() {
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return (_startAddress + _size);
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}
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Elf32_Addr getOffset() {
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return (Elf32_Addr)(_startAddress - _origAddress);
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}
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bool inSegment(char *addr) {
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return ((char *)addr >= _startAddress && (char *)addr <= _startAddress + _size);
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}
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};
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Segment *newSegment(int size, char *origAddr);
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void deleteSegment(Segment *);
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private:
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ShortSegmentManager();
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friend class Common::Singleton<ShortSegmentManager>;
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Common::List<Segment *> _list;
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char *_highestAddress;
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};
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#endif /* SHORTS_SEGMENT_MANAGER_H */
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#endif /* defined(DYNAMIC_MODULES) && defined(MIPS_TARGET) */
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