llvm-project/lld/wasm/InputChunks.h

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//===- InputChunks.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
//
//===----------------------------------------------------------------------===//
//
// An InputChunks represents an indivisible opaque region of a input wasm file.
// i.e. a single wasm data segment or a single wasm function.
//
// They are written directly to the mmap'd output file after which relocations
// are applied. Because each Chunk is independent they can be written in
// parallel.
//
// Chunks are also unit on which garbage collection (--gc-sections) operates.
//
//===----------------------------------------------------------------------===//
#ifndef LLD_WASM_INPUT_CHUNKS_H
#define LLD_WASM_INPUT_CHUNKS_H
#include "Config.h"
#include "InputFiles.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/LLVM.h"
#include "llvm/Object/Wasm.h"
namespace lld {
namespace wasm {
class ObjFile;
class OutputSegment;
class OutputSection;
class InputChunk {
public:
enum Kind { DataSegment, Function, SyntheticFunction, Section };
Kind kind() const { return sectionKind; }
virtual uint32_t getSize() const { return data().size(); }
virtual uint32_t getInputSize() const { return getSize(); };
virtual void writeTo(uint8_t *sectionStart) const;
ArrayRef<WasmRelocation> getRelocations() const { return relocations; }
void setRelocations(ArrayRef<WasmRelocation> rs) { relocations = rs; }
virtual StringRef getName() const = 0;
virtual StringRef getDebugName() const = 0;
virtual uint32_t getComdat() const = 0;
StringRef getComdatName() const;
virtual uint32_t getInputSectionOffset() const = 0;
size_t getNumRelocations() const { return relocations.size(); }
void writeRelocations(llvm::raw_ostream &os) const;
ObjFile *file;
int32_t outputOffset = 0;
// Signals that the section is part of the output. The garbage collector,
// and COMDAT handling can set a sections' Live bit.
// If GC is disabled, all sections start out as live by default.
unsigned live : 1;
// Signals the chunk was discarded by COMDAT handling.
unsigned discarded : 1;
protected:
InputChunk(ObjFile *f, Kind k)
: file(f), live(!config->gcSections), discarded(false), sectionKind(k) {}
virtual ~InputChunk() = default;
virtual ArrayRef<uint8_t> data() const = 0;
// Verifies the existing data at relocation targets matches our expectations.
// This is performed only debug builds as an extra sanity check.
void verifyRelocTargets() const;
ArrayRef<WasmRelocation> relocations;
Kind sectionKind;
};
// Represents a WebAssembly data segment which can be included as part of
// an output data segments. Note that in WebAssembly, unlike ELF and other
// formats, used the term "data segment" to refer to the continous regions of
// memory that make on the data section. See:
// https://webassembly.github.io/spec/syntax/modules.html#syntax-data
//
// For example, by default, clang will produce a separate data section for
// each global variable.
class InputSegment : public InputChunk {
public:
InputSegment(const WasmSegment &seg, ObjFile *f)
: InputChunk(f, InputChunk::DataSegment), segment(seg) {}
static bool classof(const InputChunk *c) { return c->kind() == DataSegment; }
void generateRelocationCode(raw_ostream &os) const;
uint32_t getAlignment() const { return segment.Data.Alignment; }
StringRef getName() const override { return segment.Data.Name; }
StringRef getDebugName() const override { return StringRef(); }
uint32_t getComdat() const override { return segment.Data.Comdat; }
uint32_t getInputSectionOffset() const override {
return segment.SectionOffset;
}
const OutputSegment *outputSeg = nullptr;
int32_t outputSegmentOffset = 0;
protected:
ArrayRef<uint8_t> data() const override { return segment.Data.Content; }
const WasmSegment &segment;
};
// Represents a single wasm function within and input file. These are
// combined to create the final output CODE section.
class InputFunction : public InputChunk {
public:
InputFunction(const WasmSignature &s, const WasmFunction *func, ObjFile *f)
: InputChunk(f, InputChunk::Function), signature(s), function(func) {}
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static bool classof(const InputChunk *c) {
return c->kind() == InputChunk::Function ||
c->kind() == InputChunk::SyntheticFunction;
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}
void writeTo(uint8_t *sectionStart) const override;
StringRef getName() const override { return function->SymbolName; }
StringRef getDebugName() const override { return function->DebugName; }
uint32_t getComdat() const override { return function->Comdat; }
uint32_t getFunctionInputOffset() const { return getInputSectionOffset(); }
uint32_t getFunctionCodeOffset() const { return function->CodeOffset; }
uint32_t getSize() const override {
if (config->compressRelocations && file) {
assert(compressedSize);
return compressedSize;
}
return data().size();
}
uint32_t getInputSize() const override { return function->Size; }
uint32_t getFunctionIndex() const { return functionIndex.getValue(); }
bool hasFunctionIndex() const { return functionIndex.hasValue(); }
void setFunctionIndex(uint32_t index);
uint32_t getInputSectionOffset() const override {
return function->CodeSectionOffset;
}
uint32_t getTableIndex() const { return tableIndex.getValue(); }
bool hasTableIndex() const { return tableIndex.hasValue(); }
void setTableIndex(uint32_t index);
// The size of a given input function can depend on the values of the
// LEB relocations within it. This finalizeContents method is called after
// all the symbol values have be calcualted but before getSize() is ever
// called.
void calculateSize();
const WasmSignature &signature;
protected:
ArrayRef<uint8_t> data() const override {
assert(!config->compressRelocations);
return file->codeSection->Content.slice(getInputSectionOffset(),
function->Size);
}
const WasmFunction *function;
llvm::Optional<uint32_t> functionIndex;
llvm::Optional<uint32_t> tableIndex;
uint32_t compressedFuncSize = 0;
uint32_t compressedSize = 0;
};
class SyntheticFunction : public InputFunction {
public:
SyntheticFunction(const WasmSignature &s, StringRef name,
StringRef debugName = {})
: InputFunction(s, nullptr, nullptr), name(name), debugName(debugName) {
sectionKind = InputChunk::SyntheticFunction;
}
static bool classof(const InputChunk *c) {
return c->kind() == InputChunk::SyntheticFunction;
}
StringRef getName() const override { return name; }
StringRef getDebugName() const override { return debugName; }
uint32_t getComdat() const override { return UINT32_MAX; }
void setBody(ArrayRef<uint8_t> body_) { body = body_; }
protected:
ArrayRef<uint8_t> data() const override { return body; }
StringRef name;
StringRef debugName;
ArrayRef<uint8_t> body;
};
// Represents a single Wasm Section within an input file.
class InputSection : public InputChunk {
public:
InputSection(const WasmSection &s, ObjFile *f)
: InputChunk(f, InputChunk::Section), section(s) {
assert(section.Type == llvm::wasm::WASM_SEC_CUSTOM);
}
StringRef getName() const override { return section.Name; }
StringRef getDebugName() const override { return StringRef(); }
uint32_t getComdat() const override { return UINT32_MAX; }
OutputSection *outputSec = nullptr;
protected:
ArrayRef<uint8_t> data() const override { return section.Content; }
// Offset within the input section. This is only zero since this chunk
// type represents an entire input section, not part of one.
uint32_t getInputSectionOffset() const override { return 0; }
const WasmSection &section;
};
} // namespace wasm
std::string toString(const wasm::InputChunk *);
StringRef relocTypeToString(uint8_t relocType);
} // namespace lld
#endif // LLD_WASM_INPUT_CHUNKS_H