llvm-project/lld/COFF/Chunks.h

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//===- Chunks.h -----------------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLD_COFF_CHUNKS_H
#define LLD_COFF_CHUNKS_H
#include "lld/Core/LLVM.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/Object/COFF.h"
#include <map>
#include <vector>
namespace lld {
namespace coff {
using llvm::COFF::ImportDirectoryTableEntry;
using llvm::object::COFFSymbolRef;
using llvm::object::SectionRef;
using llvm::object::coff_relocation;
using llvm::object::coff_section;
using llvm::sys::fs::file_magic;
class Defined;
class DefinedImportData;
class ObjectFile;
class OutputSection;
// A Chunk represents a chunk of data that will occupy space in the
// output (if the resolver chose that). It may or may not be backed by
// a section of an input file. It could be linker-created data, or
// doesn't even have actual data (if common or bss).
class Chunk {
public:
virtual ~Chunk() = default;
// Returns the pointer to data. It is illegal to call this function if
// this is a common or BSS chunk.
virtual const uint8_t *getData() const {
llvm_unreachable("unimplemented getData");
}
// Returns the size of this chunk (even if this is a common or BSS.)
virtual size_t getSize() const = 0;
// The writer sets and uses the addresses.
uint64_t getRVA() { return RVA; }
uint64_t getFileOff() { return FileOff; }
uint32_t getAlign() { return Align; }
void setRVA(uint64_t V) { RVA = V; }
void setFileOff(uint64_t V) { FileOff = V; }
// Applies relocations, assuming Buffer points to beginning of an
// mmap'ed output file. Because this function uses file offsets and
// RVA values of other chunks, you need to set them properly before
// calling this function.
virtual void applyRelocations(uint8_t *Buf) {}
// Returns true if getData() returns a valid pointer to data.
// BSS chunks return false. If false is returned, the space occupied
// by this chunk is filled with zeros.
virtual bool hasData() const { return true; }
// Returns readable/writable/executable bits.
virtual uint32_t getPermissions() const { return 0; }
// Returns the section name if this is a section chunk.
// It is illegal to call this function on non-section chunks.
virtual StringRef getSectionName() const {
llvm_unreachable("unimplemented getSectionName");
}
// Called if the garbage collector decides to not include this chunk
// in a final output. It's supposed to print out a log message to stderr.
// It is illegal to call this function on non-section chunks because
// only section chunks are subject of garbage collection.
virtual void printDiscardedMessage() {
llvm_unreachable("unimplemented printDiscardedMessage");
}
// Returns true if this is a COMDAT section. Usually, it is an error
// if there are more than one defined symbols having the same name,
// but symbols at begining of COMDAT sections allowed to duplicate.
virtual bool isCOMDAT() const { return false; }
// Used by the garbage collector.
virtual bool isRoot() { return false; }
virtual bool isLive() { return true; }
virtual void markLive() {}
// An output section has pointers to chunks in the section, and each
// chunk has a back pointer to an output section.
void setOutputSection(OutputSection *O) { Out = O; }
OutputSection *getOutputSection() { return Out; }
protected:
// The RVA of this chunk in the output. The writer sets a value.
uint64_t RVA = 0;
// The offset from beginning of the output file. The writer sets a value.
uint64_t FileOff = 0;
// The alignment of this chunk. The writer uses the value.
uint32_t Align = 1;
// The output section for this chunk.
OutputSection *Out = nullptr;
};
// A chunk corresponding a section of an input file.
class SectionChunk : public Chunk {
public:
SectionChunk(ObjectFile *File, const coff_section *Header,
uint32_t SectionIndex);
const uint8_t *getData() const override;
size_t getSize() const override { return Header->SizeOfRawData; }
void applyRelocations(uint8_t *Buf) override;
bool hasData() const override;
uint32_t getPermissions() const override;
StringRef getSectionName() const override { return SectionName; }
void printDiscardedMessage() override;
bool isCOMDAT() const override;
bool isRoot() override;
void markLive() override;
bool isLive() override { return Live; }
// Adds COMDAT associative sections to this COMDAT section. A chunk
// and its children are treated as a group by the garbage collector.
void addAssociative(SectionChunk *Child);
private:
SectionRef getSectionRef();
void applyReloc(uint8_t *Buf, const coff_relocation *Rel);
// A file this chunk was created from.
ObjectFile *File;
const coff_section *Header;
uint32_t SectionIndex;
StringRef SectionName;
bool Live = false;
std::vector<Chunk *> AssocChildren;
bool IsAssocChild = false;
};
// A chunk for common symbols. Common chunks don't have actual data.
class CommonChunk : public Chunk {
public:
CommonChunk(const COFFSymbolRef S) : Sym(S) {}
size_t getSize() const override { return Sym.getValue(); }
bool hasData() const override { return false; }
uint32_t getPermissions() const override;
StringRef getSectionName() const override { return ".bss"; }
private:
const COFFSymbolRef Sym;
};
// A chunk for linker-created strings.
class StringChunk : public Chunk {
public:
explicit StringChunk(StringRef S);
const uint8_t *getData() const override { return &Data[0]; }
size_t getSize() const override { return Data.size(); }
private:
std::vector<uint8_t> Data;
};
// All chunks below are for the DLL import descriptor table and
// Windows-specific. You may need to read the Microsoft PE/COFF spec
// to understand details about the data structures.
static const uint8_t ImportThunkData[] = {
0xff, 0x25, 0x00, 0x00, 0x00, 0x00, // JMP *0x0
};
// A chunk for DLL import jump table entry. In a final output, it's
// contents will be a JMP instruction to some __imp_ symbol.
class ImportThunkChunk : public Chunk {
public:
explicit ImportThunkChunk(Defined *S) : ImpSymbol(S) {}
const uint8_t *getData() const override { return ImportThunkData; }
size_t getSize() const override { return sizeof(ImportThunkData); }
void applyRelocations(uint8_t *Buf) override;
private:
Defined *ImpSymbol;
};
// A chunk for the import descriptor table.
class HintNameChunk : public Chunk {
public:
explicit HintNameChunk(StringRef Name);
const uint8_t *getData() const override { return Data.data(); }
size_t getSize() const override { return Data.size(); }
private:
std::vector<uint8_t> Data;
};
// A chunk for the import descriptor table.
class LookupChunk : public Chunk {
public:
explicit LookupChunk(HintNameChunk *H) : HintName(H) {}
bool hasData() const override { return false; }
size_t getSize() const override { return sizeof(uint64_t); }
void applyRelocations(uint8_t *Buf) override;
HintNameChunk *HintName;
};
// A chunk for the import descriptor table.
class DirectoryChunk : public Chunk {
public:
explicit DirectoryChunk(StringChunk *N) : DLLName(N) {}
bool hasData() const override { return false; }
size_t getSize() const override { return sizeof(ImportDirectoryTableEntry); }
void applyRelocations(uint8_t *Buf) override;
StringChunk *DLLName;
LookupChunk *LookupTab;
LookupChunk *AddressTab;
};
// A chunk for the import descriptor table representing.
// Contents of this chunk is always null bytes.
// This is used for terminating import tables.
class NullChunk : public Chunk {
public:
explicit NullChunk(size_t N) : Size(N) {}
bool hasData() const override { return false; }
size_t getSize() const override { return Size; }
private:
size_t Size;
};
// ImportTable creates a set of import table chunks for a given
// DLL-imported symbols.
class ImportTable {
public:
ImportTable(StringRef DLLName, std::vector<DefinedImportData *> &Symbols);
StringChunk *DLLName;
DirectoryChunk *DirTab;
std::vector<LookupChunk *> LookupTables;
std::vector<LookupChunk *> AddressTables;
std::vector<HintNameChunk *> HintNameTables;
};
} // namespace coff
} // namespace lld
#endif