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[/] [lxp32/] [trunk/] [tools/] [src/] [lxp32asm/] [linker.cpp] - Rev 8
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/* * Copyright (c) 2016 by Alex I. Kuznetsov. * * Part of the LXP32 CPU IP core. * * This module implements members of the Linker class. */ #include "linker.h" #include "linkableobject.h" #include "utils.h" #include <iostream> #include <fstream> #include <sstream> #include <map> #include <stdexcept> #include <cassert> #include <algorithm> void Linker::addObject(LinkableObject &obj) { _objects.push_back(&obj); } void Linker::link(OutputWriter &writer) { if(_objects.empty()) throw std::runtime_error("Object set is empty"); // Merge symbol tables buildSymbolTable(); // Determine entry point if(_objects.size()==1) _entryObject=_objects[0]; else if(_entryObject==nullptr) throw std::runtime_error("Entry point not defined: cannot find \"entry\" or \"Entry\" symbol"); // Assign virtual addresses placeObjects(); // Perform relocations for(auto &obj: _objects) relocateObject(obj); // Write binary data writeObjects(writer); _bytesWritten=writer.size(); } void Linker::setBase(LinkableObject::Word base) { _base=base; } void Linker::setAlignment(std::size_t align) { _align=align; } void Linker::setImageSize(std::size_t size) { _imageSize=size; } void Linker::generateMap(std::ostream &s) { // Calculate the maximum length of a symbol name std::size_t len=0; for(auto const &obj: _objects) { for(auto const &sym: obj->symbols()) { if(sym.second.type!=LinkableObject::Imported) len=std::max(len,sym.first.size()); } } len=std::max(len+3,std::size_t(8)); // width of the first column s<<"Image base address: "<<Utils::hex(_base)<<std::endl; s<<"Object alignment: "<<_align<<std::endl; s<<"Image size: "<<(_bytesWritten/4)<<" words"<<std::endl; s<<"Number of objects: "<<_objects.size()<<std::endl; s<<std::endl; for(auto const &obj: _objects) { s<<"Object \""<<obj->name()<<"\" at address "<<Utils::hex(obj->virtualAddress())<<std::endl; s<<std::endl; std::multimap<LinkableObject::Word,std::pair<std::string,LinkableObject::SymbolData> > sorted; for(auto const &sym: obj->symbols()) sorted.emplace(sym.second.rva,sym); for(auto const &sym: sorted) { if(sym.second.second.type==LinkableObject::Imported) continue; s<<sym.second.first; s<<std::string(len-sym.second.first.size(),' '); s<<Utils::hex(obj->virtualAddress()+sym.second.second.rva); if(sym.second.second.type==LinkableObject::Local) s<<" Local"; else s<<" Exported"; s<<std::endl; } s<<std::endl; } } /* * Private members */ void Linker::buildSymbolTable() { _globalSymbolTable.clear(); // Build a table of exported symbols from all modules for(auto const &obj: _objects) { auto const &table=obj->symbols(); for(auto const &item: table) { if((item.first=="entry"||item.first=="Entry")&&item.second.type!=LinkableObject::Imported) { if(_entryObject) { std::ostringstream msg; msg<<obj->name()<<": Duplicate definition of the entry symbol "; msg<<"(previously defined in "<<_entryObject->name()<<")"; throw std::runtime_error(msg.str()); } if(item.second.rva!=0) { std::ostringstream msg; msg<<obj->name()<<": "; msg<<"Entry point must refer to the start of the object"; throw std::runtime_error(msg.str()); } _entryObject=obj; } if(item.second.type==LinkableObject::Local) continue; // Insert item to the global symbol table if it doesn't exist yet auto it=_globalSymbolTable.emplace(item.first,GlobalSymbolData()).first; // Check that the symbol has not been already defined in another object if(item.second.type==LinkableObject::Exported) { if(it->second.obj) { std::ostringstream msg; msg<<obj->name()<<": Duplicate definition of \""<<item.first; msg<<"\" (previously defined in "<<it->second.obj->name()<<")"; throw std::runtime_error(msg.str()); } it->second.obj=obj; it->second.rva=item.second.rva; } if(!item.second.refs.empty()) it->second.refs.insert(obj); } } // Check that local symbols don't shadow the public ones for(auto const &obj: _objects) { auto const &table=obj->symbols(); for(auto const &item: table) { if(item.second.type!=LinkableObject::Local) continue; auto it=_globalSymbolTable.find(item.first); if(it==_globalSymbolTable.end()) continue; if(!it->second.obj) continue; if(item.first==it->first) { std::ostringstream msg; msg<<obj->name()<<": Local symbol \""<<item.first<<"\" shadows the public one "; msg<<"(defined in "<<it->second.obj->name()<<")"; throw std::runtime_error(msg.str()); } } } // Check that no undefined symbols remain for(auto const &item: _globalSymbolTable) { if(item.second.obj==nullptr&&!item.second.refs.empty()) { std::ostringstream msg; msg<<"Undefined symbol: \""<<item.first<<"\""; auto const it=item.second.refs.begin(); msg<<" (referenced from "<<(*it)->name()<<")"; throw std::runtime_error(msg.str()); } } } void Linker::placeObjects() { auto currentBase=_base; // Make entry object the first if(_objects.size()>1) { for(auto it=_objects.begin();it!=_objects.end();++it) { if(*it==_entryObject) { _objects.erase(it); break; } } _objects.insert(_objects.begin(),_entryObject); } // Remove unreferenced objects if(_objects.size()>1) { std::set<const LinkableObject*> used; markAsUsed(_objects[0],used); for(auto it=_objects.begin();it!=_objects.end();) { if(used.find(*it)==used.end()) { std::cerr<<"Linker warning: skipping an unreferenced object \""; std::cerr<<(*it)->name()<<"\""<<std::endl; for(auto sym=_globalSymbolTable.begin();sym!=_globalSymbolTable.end();) { if(sym->second.obj==*it) sym=_globalSymbolTable.erase(sym); else ++sym; } it=_objects.erase(it); } else ++it; } } // Set base addresses for(auto it=_objects.begin();it!=_objects.end();++it) { (*it)->setVirtualAddress(currentBase); if(it+1!=_objects.end()) (*it)->addPadding(_align); else (*it)->addPadding(); currentBase+=static_cast<LinkableObject::Word>((*it)->codeSize()); } } void Linker::relocateObject(LinkableObject *obj) { for(auto const &sym: obj->symbols()) { LinkableObject::Word addr; if(sym.second.refs.empty()) continue; if(sym.second.type==LinkableObject::Local) addr=obj->virtualAddress()+sym.second.rva; else { auto it=_globalSymbolTable.find(sym.first); assert(it!=_globalSymbolTable.end()); assert(it->second.obj); addr=it->second.obj->virtualAddress()+it->second.rva; } for(auto const &ref: sym.second.refs) { if(ref.type==LinkableObject::Regular) obj->replaceWord(ref.rva,addr+ref.offset); else { auto target=static_cast<LinkableObject::Word>(addr+ref.offset); if(target>0xFFFFF&&target<0xFFF00000) { std::ostringstream msg; msg<<"Address 0x"<<Utils::hex(target)<<" is out of the range for a short reference"; msg<<" (referenced from "<<ref.source<<":"<<ref.line<<")"; throw std::runtime_error(msg.str()); } target&=0x1FFFFF; auto w=obj->getWord(ref.rva); w|=(target&0xFFFF); w|=((target<<8)&0x1F000000); obj->replaceWord(ref.rva,w); } } } } void Linker::writeObjects(OutputWriter &writer) { std::size_t currentSize=0; // Write entry object writer.write(reinterpret_cast<const char*>(_entryObject->code()),_entryObject->codeSize()); currentSize+=_entryObject->codeSize(); // Write other objects for(auto const &obj: _objects) { if(obj==_entryObject) continue; writer.write(reinterpret_cast<const char*>(obj->code()),obj->codeSize()); currentSize+=obj->codeSize(); } // Pad file if requested if(_imageSize>0) { if(currentSize>_imageSize) throw std::runtime_error("Image size exceeds the specified value"); else if(currentSize<_imageSize) writer.pad(_imageSize-currentSize); } } void Linker::markAsUsed(const LinkableObject *obj,std::set<const LinkableObject*> &used) { if(used.find(obj)!=used.end()) return; // already processed used.insert(obj); for(auto const &sym: _globalSymbolTable) { for(auto const &ref: sym.second.refs) { if(ref==obj) markAsUsed(sym.second.obj,used); } } }
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