llvm-project/lld/COFF/Chunks.h

713 lines
24 KiB
C++

//===- Chunks.h -------------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#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/PointerIntPair.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;
// The log base 2 of the largest section alignment, which is log2(8192), or 13.
enum : unsigned { Log2MaxSectionAlignment = 13 };
// 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 : uint8_t { SectionKind, OtherKind, ImportThunkKind };
Kind kind() const { return chunkKind; }
// Returns the size of this chunk (even if this is a common or BSS.)
size_t getSize() const;
// Returns chunk alignment in power of two form. Value values are powers of
// two from 1 to 8192.
uint32_t getAlignment() const { return 1U << p2Align; }
// Update the chunk section alignment measured in bytes. Internally alignment
// is stored in log2.
void setAlignment(uint32_t align) {
// Treat zero byte alignment as 1 byte alignment.
align = align ? align : 1;
assert(llvm::isPowerOf2_32(align) && "alignment is not a power of 2");
p2Align = llvm::Log2_32(align);
assert(p2Align <= Log2MaxSectionAlignment &&
"impossible requested alignment");
}
// 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.
void writeTo(uint8_t *buf) const;
// The writer sets and uses the addresses. In practice, PE images cannot be
// larger than 2GB. Chunks are always laid as part of the image, so Chunk RVAs
// can be stored with 32 bits.
uint32_t getRVA() const { return rva; }
void setRVA(uint64_t v) {
// This may truncate. The writer checks for overflow later.
rva = (uint32_t)v;
}
// Returns readable/writable/executable bits.
uint32_t getOutputCharacteristics() const;
// Returns the section name if this is a section chunk.
// It is illegal to call this function on non-section chunks.
StringRef getSectionName() const;
// An output section has pointers to chunks in the section, and each
// chunk has a back pointer to an output section.
void setOutputSectionIdx(uint16_t o) { osidx = o; }
uint16_t getOutputSectionIdx() const { return osidx; }
OutputSection *getOutputSection() const;
// Windows-specific.
// Collect all locations that contain absolute addresses for base relocations.
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.
StringRef getDebugName() const;
// Return true if this file has the hotpatch flag set to true in the
// S_COMPILE3 record in codeview debug info. Also returns true for some thunks
// synthesized by the linker.
bool isHotPatchable() const;
protected:
Chunk(Kind k = OtherKind) : chunkKind(k), hasData(true), p2Align(0) {}
const Kind chunkKind;
public:
// 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. Corresponds to the
// IMAGE_SCN_CNT_UNINITIALIZED_DATA section characteristic bit.
uint8_t hasData : 1;
public:
// The alignment of this chunk, stored in log2 form. The writer uses the
// value.
uint8_t p2Align : 7;
// The output section index for this chunk. The first valid section number is
// one.
uint16_t osidx = 0;
// The RVA of this chunk in the output. The writer sets a value.
uint32_t rva = 0;
};
class NonSectionChunk : public Chunk {
public:
virtual ~NonSectionChunk() = default;
// Returns the size of this chunk (even if this is a common or BSS.)
virtual size_t getSize() const = 0;
virtual uint32_t getOutputCharacteristics() const { return 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 {}
// 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");
}
// 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() const { return ""; }
static bool classof(const Chunk *c) { return c->kind() != SectionKind; }
protected:
NonSectionChunk(Kind k = OtherKind) : Chunk(k) {}
};
// 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; }
size_t getSize() const { return header->SizeOfRawData; }
ArrayRef<uint8_t> getContents() const;
void writeTo(uint8_t *buf) const;
// Defend against unsorted relocations. This may be overly conservative.
void sortRelocations();
// Write and relocate a portion of the section. This is intended to be called
// in a loop. Relocations must be sorted first.
void writeAndRelocateSubsection(ArrayRef<uint8_t> sec,
ArrayRef<uint8_t> subsec,
uint32_t &nextRelocIndex, uint8_t *buf) const;
uint32_t getOutputCharacteristics() const {
return header->Characteristics & (permMask | typeMask);
}
StringRef getSectionName() const {
return StringRef(sectionNameData, sectionNameSize);
}
void getBaserels(std::vector<Baserel> *res);
bool isCOMDAT() const;
void applyRelocation(uint8_t *off, const coff_relocation &rel) 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() const;
// 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 getSectionName() == ".debug" || getSectionName().startswith(".debug$");
}
// True if this is a DWARF debug info or exception handling chunk.
bool isDWARF() const {
return getSectionName().startswith(".debug_") || getSectionName() == ".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, relocsData),
symbol_iterator(file, relocsData + relocsSize));
}
ArrayRef<coff_relocation> getRelocs() const {
return llvm::makeArrayRef(relocsData, relocsSize);
}
// Reloc setter used by ARM range extension thunk insertion.
void setRelocs(ArrayRef<coff_relocation> newRelocs) {
relocsData = newRelocs.data();
relocsSize = newRelocs.size();
assert(relocsSize == newRelocs.size() && "reloc size truncation");
}
// Single linked list iterator for associated comdat children.
class AssociatedIterator
: public llvm::iterator_facade_base<
AssociatedIterator, std::forward_iterator_tag, SectionChunk> {
public:
AssociatedIterator() = default;
AssociatedIterator(SectionChunk *head) : cur(head) {}
bool operator==(const AssociatedIterator &r) const { return cur == r.cur; }
// FIXME: Wrong const-ness, but it makes filter ranges work.
SectionChunk &operator*() const { return *cur; }
SectionChunk &operator*() { return *cur; }
AssociatedIterator &operator++() {
cur = cur->assocChildren;
return *this;
}
private:
SectionChunk *cur = nullptr;
};
// Allow iteration over the associated child chunks for this section.
llvm::iterator_range<AssociatedIterator> children() const {
// Associated sections do not have children. The assocChildren field is
// part of the parent's list of children.
bool isAssoc = selection == llvm::COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
return llvm::make_range(
AssociatedIterator(isAssoc ? nullptr : assocChildren),
AssociatedIterator(nullptr));
}
// The section ID this chunk belongs to in its Obj.
uint32_t getSectionNumber() const;
ArrayRef<uint8_t> consumeDebugMagic();
static ArrayRef<uint8_t> consumeDebugMagic(ArrayRef<uint8_t> data,
StringRef sectionName);
static SectionChunk *findByName(ArrayRef<SectionChunk *> sections,
StringRef name);
// The file that this chunk was created from.
ObjFile *file;
// Pointer to the COFF section header in the input file.
const coff_section *header;
// The COMDAT leader symbol if this is a COMDAT chunk.
DefinedRegular *sym = nullptr;
// 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;
// Used by the garbage collector.
bool live;
// 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;
// The COMDAT selection if this is a COMDAT chunk.
llvm::COFF::COMDATType selection = (llvm::COFF::COMDATType)0;
// 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;
private:
SectionChunk *assocChildren = nullptr;
// Used for ICF (Identical COMDAT Folding)
void replace(SectionChunk *other);
uint32_t eqClass[2] = {0, 0};
// Relocations for this section. Size is stored below.
const coff_relocation *relocsData;
// Section name string. Size is stored below.
const char *sectionNameData;
uint32_t relocsSize = 0;
uint32_t sectionNameSize = 0;
};
// Inline methods to implement faux-virtual dispatch for SectionChunk.
inline size_t Chunk::getSize() const {
if (isa<SectionChunk>(this))
return static_cast<const SectionChunk *>(this)->getSize();
else
return static_cast<const NonSectionChunk *>(this)->getSize();
}
inline uint32_t Chunk::getOutputCharacteristics() const {
if (isa<SectionChunk>(this))
return static_cast<const SectionChunk *>(this)->getOutputCharacteristics();
else
return static_cast<const NonSectionChunk *>(this)
->getOutputCharacteristics();
}
inline void Chunk::writeTo(uint8_t *buf) const {
if (isa<SectionChunk>(this))
static_cast<const SectionChunk *>(this)->writeTo(buf);
else
static_cast<const NonSectionChunk *>(this)->writeTo(buf);
}
inline StringRef Chunk::getSectionName() const {
if (isa<SectionChunk>(this))
return static_cast<const SectionChunk *>(this)->getSectionName();
else
return static_cast<const NonSectionChunk *>(this)->getSectionName();
}
inline void Chunk::getBaserels(std::vector<Baserel> *res) {
if (isa<SectionChunk>(this))
static_cast<SectionChunk *>(this)->getBaserels(res);
else
static_cast<NonSectionChunk *>(this)->getBaserels(res);
}
inline StringRef Chunk::getDebugName() const {
if (isa<SectionChunk>(this))
return static_cast<const SectionChunk *>(this)->getDebugName();
else
return static_cast<const NonSectionChunk *>(this)->getDebugName();
}
// 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 NonSectionChunk {
public:
MergeChunk(uint32_t alignment);
static void addSection(SectionChunk *c);
void finalizeContents();
void assignSubsectionRVAs();
uint32_t getOutputCharacteristics() const override;
StringRef getSectionName() const override { return ".rdata"; }
size_t getSize() const override;
void writeTo(uint8_t *buf) const override;
static MergeChunk *instances[Log2MaxSectionAlignment + 1];
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 NonSectionChunk {
public:
CommonChunk(const COFFSymbolRef sym);
size_t getSize() const override { return sym.getValue(); }
uint32_t getOutputCharacteristics() const override;
StringRef getSectionName() const override { return ".bss"; }
private:
const COFFSymbolRef sym;
};
// A chunk for linker-created strings.
class StringChunk : public NonSectionChunk {
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 ImportThunkChunk : public NonSectionChunk {
public:
ImportThunkChunk(Defined *s)
: NonSectionChunk(ImportThunkKind), impSymbol(s) {}
static bool classof(const Chunk *c) { return c->kind() == ImportThunkKind; }
protected:
Defined *impSymbol;
};
class ImportThunkChunkX64 : public ImportThunkChunk {
public:
explicit ImportThunkChunkX64(Defined *s);
size_t getSize() const override { return sizeof(importThunkX86); }
void writeTo(uint8_t *buf) const override;
};
class ImportThunkChunkX86 : public ImportThunkChunk {
public:
explicit ImportThunkChunkX86(Defined *s) : ImportThunkChunk(s) {}
size_t getSize() const override { return sizeof(importThunkX86); }
void getBaserels(std::vector<Baserel> *res) override;
void writeTo(uint8_t *buf) const override;
};
class ImportThunkChunkARM : public ImportThunkChunk {
public:
explicit ImportThunkChunkARM(Defined *s) : ImportThunkChunk(s) {
setAlignment(2);
}
size_t getSize() const override { return sizeof(importThunkARM); }
void getBaserels(std::vector<Baserel> *res) override;
void writeTo(uint8_t *buf) const override;
};
class ImportThunkChunkARM64 : public ImportThunkChunk {
public:
explicit ImportThunkChunkARM64(Defined *s) : ImportThunkChunk(s) {
setAlignment(4);
}
size_t getSize() const override { return sizeof(importThunkARM64); }
void writeTo(uint8_t *buf) const override;
};
class RangeExtensionThunkARM : public NonSectionChunk {
public:
explicit RangeExtensionThunkARM(Defined *t) : target(t) { setAlignment(2); }
size_t getSize() const override;
void writeTo(uint8_t *buf) const override;
Defined *target;
};
class RangeExtensionThunkARM64 : public NonSectionChunk {
public:
explicit RangeExtensionThunkARM64(Defined *t) : target(t) { setAlignment(4); }
size_t getSize() const override;
void writeTo(uint8_t *buf) const override;
Defined *target;
};
// Windows-specific.
// See comments for DefinedLocalImport class.
class LocalImportChunk : public NonSectionChunk {
public:
explicit LocalImportChunk(Defined *s) : sym(s) {
setAlignment(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 NonSectionChunk {
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;
};
// Table which contains symbol RVAs with flags. Used for /guard:ehcont.
class RVAFlagTableChunk : public NonSectionChunk {
public:
explicit RVAFlagTableChunk(SymbolRVASet s) : syms(std::move(s)) {}
size_t getSize() const override { return syms.size() * 5; }
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 NonSectionChunk {
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 NonSectionChunk {
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 NonSectionChunk {
public:
PseudoRelocTableChunk(std::vector<RuntimePseudoReloc> &relocs)
: relocs(std::move(relocs)) {
setAlignment(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 NonSectionChunk {
public:
AbsolutePointerChunk(uint64_t value) : value(value) {
setAlignment(getSize());
}
size_t getSize() const override;
void writeTo(uint8_t *buf) const override;
private:
uint64_t value;
};
// Return true if this file has the hotpatch flag set to true in the S_COMPILE3
// record in codeview debug info. Also returns true for some thunks synthesized
// by the linker.
inline bool Chunk::isHotPatchable() const {
if (auto *sc = dyn_cast<SectionChunk>(this))
return sc->file->hotPatchable;
else if (isa<ImportThunkChunk>(this))
return true;
return false;
}
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