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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
* This program 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 for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*/
#ifndef SHORTS_SEGMENT_MANAGER_H
#define SHORTS_SEGMENT_MANAGER_H
#include "common/scummsys.h"
#if defined(DYNAMIC_MODULES) && defined(USE_ELF_LOADER) && defined(MIPS_TARGET)
#include "backends/plugins/elf/elf32.h"
#include "common/singleton.h"
#include "common/list.h"
#define ShortsMan ShortSegmentManager::instance()
/**
* ShortSegmentManager
*
* Since MIPS is limited to 32 bits per instruction, loading data that's further away than 16 bits
* takes several instructions. Thus, small global data (which is likely to be accessed a lot from
* multiple locations) is often put into a GP-relative area (GP standing for the global pointer register)
* in MIPS processors. This class manages these segments of small global data, and is used by the
* member functions of MIPSDLObject, which query in information from this manager in order to deal with
* this segment during the loading/unloading of plugins.
*
* Since there's no true dynamic linker to change the GP register between plugins and the main engine,
* custom ld linker scripts for both the main executable and the plugins ensure the GP-area is in the
* same place for both. The ShortSegmentManager accesses this place via the symbols __plugin_hole_start
* and __plugin_hole_end, which are defined in those custom ld linker scripts.
*/
class ShortSegmentManager : public Common::Singleton<ShortSegmentManager> {
private:
char *_shortsStart;
char *_shortsEnd;
public:
char *getShortsStart() {
return _shortsStart;
}
// Returns whether or not an absolute address is in the GP-relative section.
bool inGeneralSegment(char *addr) {
return (addr >= _shortsStart && addr < _shortsEnd);
}
class Segment {
private:
friend class ShortSegmentManager;
Segment(char *start, uint32 size, char *origAddr) :
_startAddress(start),
_size(size),
_origAddress(origAddr) {
}
virtual ~Segment() {
}
char *_startAddress; // Start of shorts segment in memory
uint32 _size; // Size of shorts segment
char *_origAddress; // Original address this segment was supposed to be at
public:
char *getStart() {
return _startAddress;
}
char *getEnd() {
return (_startAddress + _size);
}
Elf32_Addr getOffset() {
return (Elf32_Addr)(_startAddress - _origAddress);
}
bool inSegment(char *addr) {
return (addr >= _startAddress && addr <= _startAddress + _size);
}
};
Segment *newSegment(uint32 size, char *origAddr);
void deleteSegment(Segment *);
private:
ShortSegmentManager();
friend class Common::Singleton<ShortSegmentManager>;
Common::List<Segment *> _list;
char *_highestAddress;
};
#endif // defined(DYNAMIC_MODULES) && defined(USE_ELF_LOADER) && defined(MIPS_TARGET)
#endif /* SHORTS_SEGMENT_MANAGER_H */
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