349 lines
11 KiB
C++
349 lines
11 KiB
C++
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//===- OutputSections.cpp -------------------------------------------------===//
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//
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// The LLVM Linker
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "OutputSections.h"
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#include "Config.h"
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#include "InputFiles.h"
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#include "OutputSegment.h"
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#include "SymbolTable.h"
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#include "lld/Common/ErrorHandler.h"
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#include "lld/Common/Memory.h"
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#include "lld/Common/Threads.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/Support/LEB128.h"
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#define DEBUG_TYPE "lld"
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using namespace llvm;
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using namespace llvm::wasm;
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using namespace lld;
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using namespace lld::wasm;
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enum class RelocEncoding {
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Uleb128,
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Sleb128,
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I32,
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};
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static StringRef sectionTypeToString(uint32_t SectionType) {
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switch (SectionType) {
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case WASM_SEC_CUSTOM:
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return "CUSTOM";
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case WASM_SEC_TYPE:
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return "TYPE";
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case WASM_SEC_IMPORT:
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return "IMPORT";
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case WASM_SEC_FUNCTION:
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return "FUNCTION";
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case WASM_SEC_TABLE:
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return "TABLE";
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case WASM_SEC_MEMORY:
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return "MEMORY";
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case WASM_SEC_GLOBAL:
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return "GLOBAL";
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case WASM_SEC_EXPORT:
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return "EXPORT";
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case WASM_SEC_START:
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return "START";
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case WASM_SEC_ELEM:
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return "ELEM";
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case WASM_SEC_CODE:
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return "CODE";
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case WASM_SEC_DATA:
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return "DATA";
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default:
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fatal("invalid section type");
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}
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}
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std::string lld::toString(const OutputSection &Section) {
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std::string rtn = Section.getSectionName();
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if (!Section.Name.empty())
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rtn += "(" + Section.Name + ")";
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return rtn;
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}
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static void applyRelocation(uint8_t *Buf, const OutputRelocation &Reloc) {
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DEBUG(dbgs() << "write reloc: type=" << Reloc.Reloc.Type
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<< " index=" << Reloc.Reloc.Index << " value=" << Reloc.Value
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<< " offset=" << Reloc.Reloc.Offset << "\n");
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Buf += Reloc.Reloc.Offset;
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int64_t ExistingValue;
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switch (Reloc.Reloc.Type) {
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case R_WEBASSEMBLY_TYPE_INDEX_LEB:
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case R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
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ExistingValue = decodeULEB128(Buf);
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if (ExistingValue != Reloc.Reloc.Index) {
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DEBUG(dbgs() << "existing value: " << decodeULEB128(Buf) << "\n");
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assert(decodeULEB128(Buf) == Reloc.Reloc.Index);
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}
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LLVM_FALLTHROUGH;
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case R_WEBASSEMBLY_MEMORY_ADDR_LEB:
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case R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
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encodeULEB128(Reloc.Value, Buf, 5);
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break;
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case R_WEBASSEMBLY_TABLE_INDEX_SLEB:
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ExistingValue = decodeSLEB128(Buf);
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if (ExistingValue != Reloc.Reloc.Index) {
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DEBUG(dbgs() << "existing value: " << decodeSLEB128(Buf) << "\n");
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assert(decodeSLEB128(Buf) == Reloc.Reloc.Index);
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}
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LLVM_FALLTHROUGH;
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case R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
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encodeSLEB128(static_cast<int32_t>(Reloc.Value), Buf, 5);
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break;
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case R_WEBASSEMBLY_TABLE_INDEX_I32:
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case R_WEBASSEMBLY_MEMORY_ADDR_I32:
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support::endian::write32<support::little>(Buf, Reloc.Value);
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break;
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default:
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llvm_unreachable("unknown relocation type");
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}
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}
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static void applyRelocations(uint8_t *Buf, ArrayRef<OutputRelocation> Relocs) {
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if (!Relocs.size())
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return;
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log("applyRelocations: count=" + Twine(Relocs.size()));
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for (const OutputRelocation &Reloc : Relocs)
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applyRelocation(Buf, Reloc);
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}
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// Relocations contain an index into the function, global or table index
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// space of the input file. This function takes a relocation and returns the
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// relocated index (i.e. translates from the input index space to the output
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// index space).
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static uint32_t calcNewIndex(const ObjFile &File, const WasmRelocation &Reloc) {
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switch (Reloc.Type) {
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case R_WEBASSEMBLY_TYPE_INDEX_LEB:
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return File.relocateTypeIndex(Reloc.Index);
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case R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
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return File.relocateFunctionIndex(Reloc.Index);
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case R_WEBASSEMBLY_TABLE_INDEX_I32:
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case R_WEBASSEMBLY_TABLE_INDEX_SLEB:
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return File.relocateTableIndex(Reloc.Index);
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case R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
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case R_WEBASSEMBLY_MEMORY_ADDR_LEB:
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case R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
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case R_WEBASSEMBLY_MEMORY_ADDR_I32:
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return File.relocateGlobalIndex(Reloc.Index);
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default:
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llvm_unreachable("unknown relocation type");
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}
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}
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// Take a vector of relocations from an input file and create output
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// relocations based on them. Calculates the updated index and offset for
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// each relocation as well as the value to write out in the final binary.
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static void calcRelocations(const ObjFile &File,
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ArrayRef<WasmRelocation> Relocs,
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std::vector<OutputRelocation> &OutputRelocs,
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int32_t OutputOffset) {
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log("calcRelocations: " + File.getName() + " offset=" + Twine(OutputOffset));
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for (const WasmRelocation &Reloc : Relocs) {
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OutputRelocation NewReloc;
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NewReloc.Reloc = Reloc;
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NewReloc.Reloc.Offset += OutputOffset;
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DEBUG(dbgs() << "reloc: type=" << Reloc.Type << " index=" << Reloc.Index
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<< " offset=" << Reloc.Offset
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<< " newOffset=" << NewReloc.Reloc.Offset << "\n");
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if (Config->EmitRelocs)
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NewReloc.NewIndex = calcNewIndex(File, Reloc);
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else
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NewReloc.NewIndex = UINT32_MAX;
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switch (Reloc.Type) {
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case R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
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case R_WEBASSEMBLY_MEMORY_ADDR_I32:
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case R_WEBASSEMBLY_MEMORY_ADDR_LEB:
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NewReloc.Value = File.getRelocatedAddress(Reloc.Index);
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if (NewReloc.Value != UINT32_MAX)
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NewReloc.Value += Reloc.Addend;
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break;
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default:
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NewReloc.Value = calcNewIndex(File, Reloc);
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break;
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}
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OutputRelocs.emplace_back(NewReloc);
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}
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}
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std::string OutputSection::getSectionName() const {
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return sectionTypeToString(Type);
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}
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std::string SubSection::getSectionName() const {
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return std::string("subsection <type=") + std::to_string(Type) + ">";
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}
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void OutputSection::createHeader(size_t BodySize) {
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raw_string_ostream OS(Header);
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debugWrite(OS.tell(), "section type [" + Twine(getSectionName()) + "]");
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writeUleb128(OS, Type, nullptr);
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writeUleb128(OS, BodySize, "section size");
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OS.flush();
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log("createHeader: " + toString(*this) + " body=" + Twine(BodySize) +
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" total=" + Twine(getSize()));
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}
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CodeSection::CodeSection(uint32_t NumFunctions, ArrayRef<ObjFile *> Objs)
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: OutputSection(WASM_SEC_CODE), InputObjects(Objs) {
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raw_string_ostream OS(CodeSectionHeader);
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writeUleb128(OS, NumFunctions, "function count");
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OS.flush();
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BodySize = CodeSectionHeader.size();
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for (ObjFile *File : InputObjects) {
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if (!File->CodeSection)
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continue;
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File->CodeOffset = BodySize;
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ArrayRef<uint8_t> Content = File->CodeSection->Content;
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unsigned HeaderSize = 0;
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decodeULEB128(Content.data(), &HeaderSize);
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calcRelocations(*File, File->CodeSection->Relocations,
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File->CodeRelocations, BodySize - HeaderSize);
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size_t PayloadSize = Content.size() - HeaderSize;
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BodySize += PayloadSize;
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}
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createHeader(BodySize);
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}
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void CodeSection::writeTo(uint8_t *Buf) {
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log("writing " + toString(*this));
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log(" size=" + Twine(getSize()));
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Buf += Offset;
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// Write section header
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memcpy(Buf, Header.data(), Header.size());
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Buf += Header.size();
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uint8_t *ContentsStart = Buf;
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// Write code section headers
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memcpy(Buf, CodeSectionHeader.data(), CodeSectionHeader.size());
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Buf += CodeSectionHeader.size();
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// Write code section bodies
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parallelForEach(InputObjects, [ContentsStart](ObjFile *File) {
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if (!File->CodeSection)
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return;
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ArrayRef<uint8_t> Content(File->CodeSection->Content);
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// Payload doesn't include the initial header (function count)
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unsigned HeaderSize = 0;
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decodeULEB128(Content.data(), &HeaderSize);
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size_t PayloadSize = Content.size() - HeaderSize;
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memcpy(ContentsStart + File->CodeOffset, Content.data() + HeaderSize,
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PayloadSize);
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log("applying relocations for: " + File->getName());
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applyRelocations(ContentsStart, File->CodeRelocations);
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});
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}
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uint32_t CodeSection::numRelocations() const {
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uint32_t Count = 0;
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for (ObjFile *File : InputObjects)
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Count += File->CodeRelocations.size();
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return Count;
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}
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void CodeSection::writeRelocations(raw_ostream &OS) const {
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for (ObjFile *File : InputObjects)
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for (const OutputRelocation &Reloc : File->CodeRelocations)
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writeReloc(OS, Reloc);
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}
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DataSection::DataSection(ArrayRef<OutputSegment *> Segments)
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: OutputSection(WASM_SEC_DATA), Segments(Segments) {
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raw_string_ostream OS(DataSectionHeader);
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writeUleb128(OS, Segments.size(), "data segment count");
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OS.flush();
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BodySize = DataSectionHeader.size();
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for (OutputSegment *Segment : Segments) {
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raw_string_ostream OS(Segment->Header);
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writeUleb128(OS, 0, "memory index");
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writeUleb128(OS, WASM_OPCODE_I32_CONST, "opcode:i32const");
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writeSleb128(OS, Segment->StartVA, "memory offset");
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writeUleb128(OS, WASM_OPCODE_END, "opcode:end");
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writeUleb128(OS, Segment->Size, "segment size");
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OS.flush();
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Segment->setSectionOffset(BodySize);
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BodySize += Segment->Header.size();
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log("Data segment: size=" + Twine(Segment->Size));
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for (InputSegment *InputSeg : Segment->InputSegments) {
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uint32_t InputOffset = InputSeg->getInputSectionOffset();
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uint32_t OutputOffset = Segment->getSectionOffset() +
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Segment->Header.size() +
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InputSeg->getOutputSegmentOffset();
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calcRelocations(*InputSeg->File, InputSeg->Relocations,
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InputSeg->OutRelocations, OutputOffset - InputOffset);
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}
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BodySize += Segment->Size;
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}
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createHeader(BodySize);
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}
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void DataSection::writeTo(uint8_t *Buf) {
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log("writing " + toString(*this) + " size=" + Twine(getSize()) +
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" body=" + Twine(BodySize));
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Buf += Offset;
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// Write section header
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memcpy(Buf, Header.data(), Header.size());
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Buf += Header.size();
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uint8_t *ContentsStart = Buf;
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// Write data section headers
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memcpy(Buf, DataSectionHeader.data(), DataSectionHeader.size());
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parallelForEach(Segments, [ContentsStart](const OutputSegment *Segment) {
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// Write data segment header
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uint8_t *SegStart = ContentsStart + Segment->getSectionOffset();
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memcpy(SegStart, Segment->Header.data(), Segment->Header.size());
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// Write segment data payload
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for (const InputSegment *Input : Segment->InputSegments) {
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ArrayRef<uint8_t> Content(Input->Segment->Data.Content);
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memcpy(SegStart + Segment->Header.size() +
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Input->getOutputSegmentOffset(),
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Content.data(), Content.size());
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applyRelocations(ContentsStart, Input->OutRelocations);
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}
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});
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}
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uint32_t DataSection::numRelocations() const {
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uint32_t Count = 0;
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for (const OutputSegment *Seg : Segments)
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for (const InputSegment *InputSeg : Seg->InputSegments)
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Count += InputSeg->OutRelocations.size();
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return Count;
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}
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void DataSection::writeRelocations(raw_ostream &OS) const {
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for (const OutputSegment *Seg : Segments)
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for (const InputSegment *InputSeg : Seg->InputSegments)
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for (const OutputRelocation &Reloc : InputSeg->OutRelocations)
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writeReloc(OS, Reloc);
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}
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