llvm-project/lld/COFF/Chunks.h

519 lines
16 KiB
C++

//===- Chunks.h -------------------------------------------------*- C++ -*-===//
//
// 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 "Config.h"
#include "InputFiles.h"
#include "lld/Common/LLVM.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/iterator.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Object/COFF.h"
#include <utility>
#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;
class Baserel;
class Defined;
class DefinedImportData;
class DefinedRegular;
class ObjFile;
class OutputSection;
class RuntimePseudoReloc;
class Symbol;
// Mask for permissions (discardable, writable, readable, executable, etc).
const uint32_t PermMask = 0xFE000000;
// Mask for section types (code, data, bss).
const uint32_t TypeMask = 0x000000E0;
// 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:
enum Kind { SectionKind, OtherKind };
Kind kind() const { return ChunkKind; }
virtual ~Chunk() = default;
// Returns the size of this chunk (even if this is a common or BSS.)
virtual size_t getSize() const = 0;
// Write this chunk to a mmap'ed file, assuming Buf is pointing to
// beginning of the file. Because this function may use RVA values
// of other chunks for relocations, you need to set them properly
// before calling this function.
virtual void writeTo(uint8_t *Buf) const {}
// Called by the writer once before assigning addresses and writing
// the output.
virtual void readRelocTargets() {}
// Called if restarting thunk addition.
virtual void resetRelocTargets() {}
// Called by the writer after an RVA is assigned, but before calling
// getSize().
virtual void finalizeContents() {}
// The writer sets and uses the addresses.
uint64_t getRVA() const { return RVA; }
void setRVA(uint64_t V) { RVA = V; }
// Returns true if this has non-zero data. BSS chunks return
// false. If false is returned, the space occupied by this chunk
// will be filled with zeros.
virtual bool hasData() const { return true; }
// Returns readable/writable/executable bits.
virtual uint32_t getOutputCharacteristics() 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");
}
// 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() const { return Out; }
// Windows-specific.
// Collect all locations that contain absolute addresses for base relocations.
virtual void getBaserels(std::vector<Baserel> *Res) {}
// Returns a human-readable name of this chunk. Chunks are unnamed chunks of
// bytes, so this is used only for logging or debugging.
virtual StringRef getDebugName() { return ""; }
// The alignment of this chunk. The writer uses the value.
uint32_t Alignment = 1;
protected:
Chunk(Kind K = OtherKind) : ChunkKind(K) {}
const Kind ChunkKind;
// The RVA of this chunk in the output. The writer sets a value.
uint64_t RVA = 0;
// The output section for this chunk.
OutputSection *Out = nullptr;
public:
// The offset from beginning of the output section. The writer sets a value.
uint64_t OutputSectionOff = 0;
// Whether this section needs to be kept distinct from other sections during
// ICF. This is set by the driver using address-significance tables.
bool KeepUnique = false;
};
// A chunk corresponding a section of an input file.
class SectionChunk final : public Chunk {
// Identical COMDAT Folding feature accesses section internal data.
friend class ICF;
public:
class symbol_iterator : public llvm::iterator_adaptor_base<
symbol_iterator, const coff_relocation *,
std::random_access_iterator_tag, Symbol *> {
friend SectionChunk;
ObjFile *File;
symbol_iterator(ObjFile *File, const coff_relocation *I)
: symbol_iterator::iterator_adaptor_base(I), File(File) {}
public:
symbol_iterator() = default;
Symbol *operator*() const { return File->getSymbol(I->SymbolTableIndex); }
};
SectionChunk(ObjFile *File, const coff_section *Header);
static bool classof(const Chunk *C) { return C->kind() == SectionKind; }
void readRelocTargets() override;
void resetRelocTargets() override;
size_t getSize() const override { return Header->SizeOfRawData; }
ArrayRef<uint8_t> getContents() const;
void writeTo(uint8_t *Buf) const override;
bool hasData() const override;
uint32_t getOutputCharacteristics() const override;
StringRef getSectionName() const override { return SectionName; }
void getBaserels(std::vector<Baserel> *Res) override;
bool isCOMDAT() const;
void applyRelX64(uint8_t *Off, uint16_t Type, OutputSection *OS, uint64_t S,
uint64_t P) const;
void applyRelX86(uint8_t *Off, uint16_t Type, OutputSection *OS, uint64_t S,
uint64_t P) const;
void applyRelARM(uint8_t *Off, uint16_t Type, OutputSection *OS, uint64_t S,
uint64_t P) const;
void applyRelARM64(uint8_t *Off, uint16_t Type, OutputSection *OS, uint64_t S,
uint64_t P) const;
void getRuntimePseudoRelocs(std::vector<RuntimePseudoReloc> &Res);
// 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 stdout.
void printDiscardedMessage() const;
// 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);
StringRef getDebugName() override;
// True if this is a codeview debug info chunk. These will not be laid out in
// the image. Instead they will end up in the PDB, if one is requested.
bool isCodeView() const {
return SectionName == ".debug" || SectionName.startswith(".debug$");
}
// True if this is a DWARF debug info or exception handling chunk.
bool isDWARF() const {
return SectionName.startswith(".debug_") || SectionName == ".eh_frame";
}
// Allow iteration over the bodies of this chunk's relocated symbols.
llvm::iterator_range<symbol_iterator> symbols() const {
return llvm::make_range(symbol_iterator(File, Relocs.begin()),
symbol_iterator(File, Relocs.end()));
}
// Allow iteration over the associated child chunks for this section.
ArrayRef<SectionChunk *> children() const { return AssocChildren; }
// The section ID this chunk belongs to in its Obj.
uint32_t getSectionNumber() const;
// A pointer pointing to a replacement for this chunk.
// Initially it points to "this" object. If this chunk is merged
// with other chunk by ICF, it points to another chunk,
// and this chunk is considered as dead.
SectionChunk *Repl;
// The CRC of the contents as described in the COFF spec 4.5.5.
// Auxiliary Format 5: Section Definitions. Used for ICF.
uint32_t Checksum = 0;
const coff_section *Header;
// The file that this chunk was created from.
ObjFile *File;
// The COMDAT leader symbol if this is a COMDAT chunk.
DefinedRegular *Sym = nullptr;
ArrayRef<coff_relocation> Relocs;
// Used by the garbage collector.
bool Live;
// When inserting a thunk, we need to adjust a relocation to point to
// the thunk instead of the actual original target Symbol.
std::vector<Symbol *> RelocTargets;
private:
StringRef SectionName;
std::vector<SectionChunk *> AssocChildren;
// Used for ICF (Identical COMDAT Folding)
void replace(SectionChunk *Other);
uint32_t Class[2] = {0, 0};
};
// This class is used to implement an lld-specific feature (not implemented in
// MSVC) that minimizes the output size by finding string literals sharing tail
// parts and merging them.
//
// If string tail merging is enabled and a section is identified as containing a
// string literal, it is added to a MergeChunk with an appropriate alignment.
// The MergeChunk then tail merges the strings using the StringTableBuilder
// class and assigns RVAs and section offsets to each of the member chunks based
// on the offsets assigned by the StringTableBuilder.
class MergeChunk : public Chunk {
public:
MergeChunk(uint32_t Alignment);
static void addSection(SectionChunk *C);
void finalizeContents() override;
uint32_t getOutputCharacteristics() const override;
StringRef getSectionName() const override { return ".rdata"; }
size_t getSize() const override;
void writeTo(uint8_t *Buf) const override;
static std::map<uint32_t, MergeChunk *> Instances;
std::vector<SectionChunk *> Sections;
private:
llvm::StringTableBuilder Builder;
bool Finalized = false;
};
// A chunk for common symbols. Common chunks don't have actual data.
class CommonChunk : public Chunk {
public:
CommonChunk(const COFFSymbolRef Sym);
size_t getSize() const override { return Sym.getValue(); }
bool hasData() const override { return false; }
uint32_t getOutputCharacteristics() 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) : Str(S) {}
size_t getSize() const override { return Str.size() + 1; }
void writeTo(uint8_t *Buf) const override;
private:
StringRef Str;
};
static const uint8_t ImportThunkX86[] = {
0xff, 0x25, 0x00, 0x00, 0x00, 0x00, // JMP *0x0
};
static const uint8_t ImportThunkARM[] = {
0x40, 0xf2, 0x00, 0x0c, // mov.w ip, #0
0xc0, 0xf2, 0x00, 0x0c, // mov.t ip, #0
0xdc, 0xf8, 0x00, 0xf0, // ldr.w pc, [ip]
};
static const uint8_t ImportThunkARM64[] = {
0x10, 0x00, 0x00, 0x90, // adrp x16, #0
0x10, 0x02, 0x40, 0xf9, // ldr x16, [x16]
0x00, 0x02, 0x1f, 0xd6, // br x16
};
// Windows-specific.
// A chunk for DLL import jump table entry. In a final output, its
// contents will be a JMP instruction to some __imp_ symbol.
class ImportThunkChunkX64 : public Chunk {
public:
explicit ImportThunkChunkX64(Defined *S);
size_t getSize() const override { return sizeof(ImportThunkX86); }
void writeTo(uint8_t *Buf) const override;
private:
Defined *ImpSymbol;
};
class ImportThunkChunkX86 : public Chunk {
public:
explicit ImportThunkChunkX86(Defined *S) : ImpSymbol(S) {}
size_t getSize() const override { return sizeof(ImportThunkX86); }
void getBaserels(std::vector<Baserel> *Res) override;
void writeTo(uint8_t *Buf) const override;
private:
Defined *ImpSymbol;
};
class ImportThunkChunkARM : public Chunk {
public:
explicit ImportThunkChunkARM(Defined *S) : ImpSymbol(S) {}
size_t getSize() const override { return sizeof(ImportThunkARM); }
void getBaserels(std::vector<Baserel> *Res) override;
void writeTo(uint8_t *Buf) const override;
private:
Defined *ImpSymbol;
};
class ImportThunkChunkARM64 : public Chunk {
public:
explicit ImportThunkChunkARM64(Defined *S) : ImpSymbol(S) {}
size_t getSize() const override { return sizeof(ImportThunkARM64); }
void writeTo(uint8_t *Buf) const override;
private:
Defined *ImpSymbol;
};
class RangeExtensionThunk : public Chunk {
public:
explicit RangeExtensionThunk(Defined *T) : Target(T) {}
size_t getSize() const override;
void writeTo(uint8_t *Buf) const override;
Defined *Target;
};
// Windows-specific.
// See comments for DefinedLocalImport class.
class LocalImportChunk : public Chunk {
public:
explicit LocalImportChunk(Defined *S) : Sym(S) {
Alignment = Config->Wordsize;
}
size_t getSize() const override;
void getBaserels(std::vector<Baserel> *Res) override;
void writeTo(uint8_t *Buf) const override;
private:
Defined *Sym;
};
// Duplicate RVAs are not allowed in RVA tables, so unique symbols by chunk and
// offset into the chunk. Order does not matter as the RVA table will be sorted
// later.
struct ChunkAndOffset {
Chunk *InputChunk;
uint32_t Offset;
struct DenseMapInfo {
static ChunkAndOffset getEmptyKey() {
return {llvm::DenseMapInfo<Chunk *>::getEmptyKey(), 0};
}
static ChunkAndOffset getTombstoneKey() {
return {llvm::DenseMapInfo<Chunk *>::getTombstoneKey(), 0};
}
static unsigned getHashValue(const ChunkAndOffset &CO) {
return llvm::DenseMapInfo<std::pair<Chunk *, uint32_t>>::getHashValue(
{CO.InputChunk, CO.Offset});
}
static bool isEqual(const ChunkAndOffset &LHS, const ChunkAndOffset &RHS) {
return LHS.InputChunk == RHS.InputChunk && LHS.Offset == RHS.Offset;
}
};
};
using SymbolRVASet = llvm::DenseSet<ChunkAndOffset>;
// Table which contains symbol RVAs. Used for /safeseh and /guard:cf.
class RVATableChunk : public Chunk {
public:
explicit RVATableChunk(SymbolRVASet S) : Syms(std::move(S)) {}
size_t getSize() const override { return Syms.size() * 4; }
void writeTo(uint8_t *Buf) const override;
private:
SymbolRVASet Syms;
};
// Windows-specific.
// This class represents a block in .reloc section.
// See the PE/COFF spec 5.6 for details.
class BaserelChunk : public Chunk {
public:
BaserelChunk(uint32_t Page, Baserel *Begin, Baserel *End);
size_t getSize() const override { return Data.size(); }
void writeTo(uint8_t *Buf) const override;
private:
std::vector<uint8_t> Data;
};
class Baserel {
public:
Baserel(uint32_t V, uint8_t Ty) : RVA(V), Type(Ty) {}
explicit Baserel(uint32_t V) : Baserel(V, getDefaultType()) {}
uint8_t getDefaultType();
uint32_t RVA;
uint8_t Type;
};
// This is a placeholder Chunk, to allow attaching a DefinedSynthetic to a
// specific place in a section, without any data. This is used for the MinGW
// specific symbol __RUNTIME_PSEUDO_RELOC_LIST_END__, even though the concept
// of an empty chunk isn't MinGW specific.
class EmptyChunk : public Chunk {
public:
EmptyChunk() {}
size_t getSize() const override { return 0; }
void writeTo(uint8_t *Buf) const override {}
};
// MinGW specific, for the "automatic import of variables from DLLs" feature.
// This provides the table of runtime pseudo relocations, for variable
// references that turned out to need to be imported from a DLL even though
// the reference didn't use the dllimport attribute. The MinGW runtime will
// process this table after loading, before handling control over to user
// code.
class PseudoRelocTableChunk : public Chunk {
public:
PseudoRelocTableChunk(std::vector<RuntimePseudoReloc> &Relocs)
: Relocs(std::move(Relocs)) {
Alignment = 4;
}
size_t getSize() const override;
void writeTo(uint8_t *Buf) const override;
private:
std::vector<RuntimePseudoReloc> Relocs;
};
// MinGW specific; information about one individual location in the image
// that needs to be fixed up at runtime after loading. This represents
// one individual element in the PseudoRelocTableChunk table.
class RuntimePseudoReloc {
public:
RuntimePseudoReloc(Defined *Sym, SectionChunk *Target, uint32_t TargetOffset,
int Flags)
: Sym(Sym), Target(Target), TargetOffset(TargetOffset), Flags(Flags) {}
Defined *Sym;
SectionChunk *Target;
uint32_t TargetOffset;
// The Flags field contains the size of the relocation, in bits. No other
// flags are currently defined.
int Flags;
};
// MinGW specific. A Chunk that contains one pointer-sized absolute value.
class AbsolutePointerChunk : public Chunk {
public:
AbsolutePointerChunk(uint64_t Value) : Value(Value) {
Alignment = getSize();
}
size_t getSize() const override;
void writeTo(uint8_t *Buf) const override;
private:
uint64_t Value;
};
void applyMOV32T(uint8_t *Off, uint32_t V);
void applyBranch24T(uint8_t *Off, int32_t V);
void applyArm64Addr(uint8_t *Off, uint64_t S, uint64_t P, int Shift);
void applyArm64Imm(uint8_t *Off, uint64_t Imm, uint32_t RangeLimit);
void applyArm64Branch26(uint8_t *Off, int64_t V);
} // namespace coff
} // namespace lld
namespace llvm {
template <>
struct DenseMapInfo<lld::coff::ChunkAndOffset>
: lld::coff::ChunkAndOffset::DenseMapInfo {};
}
#endif