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450 lines
16 KiB
450 lines
16 KiB
//===- Writer.cpp ---------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "Writer.h"
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#include "Object.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/BinaryFormat/COFF.h"
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#include "llvm/Object/COFF.h"
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#include "llvm/Support/ErrorHandling.h"
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#include <cstddef>
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#include <cstdint>
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namespace llvm {
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namespace objcopy {
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namespace coff {
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using namespace object;
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using namespace COFF;
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Error COFFWriter::finalizeRelocTargets() {
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for (Section &Sec : Obj.getMutableSections()) {
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for (Relocation &R : Sec.Relocs) {
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const Symbol *Sym = Obj.findSymbol(R.Target);
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if (Sym == nullptr)
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return createStringError(object_error::invalid_symbol_index,
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"relocation target '%s' (%zu) not found",
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R.TargetName.str().c_str(), R.Target);
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R.Reloc.SymbolTableIndex = Sym->RawIndex;
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}
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}
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return Error::success();
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}
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Error COFFWriter::finalizeSymbolContents() {
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for (Symbol &Sym : Obj.getMutableSymbols()) {
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if (Sym.TargetSectionId <= 0) {
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// Undefined, or a special kind of symbol. These negative values
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// are stored in the SectionNumber field which is unsigned.
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Sym.Sym.SectionNumber = static_cast<uint32_t>(Sym.TargetSectionId);
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} else {
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const Section *Sec = Obj.findSection(Sym.TargetSectionId);
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if (Sec == nullptr)
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return createStringError(object_error::invalid_symbol_index,
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"symbol '%s' points to a removed section",
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Sym.Name.str().c_str());
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Sym.Sym.SectionNumber = Sec->Index;
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if (Sym.Sym.NumberOfAuxSymbols == 1 &&
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Sym.Sym.StorageClass == IMAGE_SYM_CLASS_STATIC) {
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coff_aux_section_definition *SD =
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reinterpret_cast<coff_aux_section_definition *>(
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Sym.AuxData[0].Opaque);
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uint32_t SDSectionNumber;
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if (Sym.AssociativeComdatTargetSectionId == 0) {
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// Not a comdat associative section; just set the Number field to
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// the number of the section itself.
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SDSectionNumber = Sec->Index;
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} else {
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Sec = Obj.findSection(Sym.AssociativeComdatTargetSectionId);
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if (Sec == nullptr)
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return createStringError(
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object_error::invalid_symbol_index,
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"symbol '%s' is associative to a removed section",
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Sym.Name.str().c_str());
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SDSectionNumber = Sec->Index;
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}
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// Update the section definition with the new section number.
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SD->NumberLowPart = static_cast<uint16_t>(SDSectionNumber);
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SD->NumberHighPart = static_cast<uint16_t>(SDSectionNumber >> 16);
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}
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}
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// Check that we actually have got AuxData to match the weak symbol target
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// we want to set. Only >= 1 would be required, but only == 1 makes sense.
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if (Sym.WeakTargetSymbolId && Sym.Sym.NumberOfAuxSymbols == 1) {
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coff_aux_weak_external *WE =
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reinterpret_cast<coff_aux_weak_external *>(Sym.AuxData[0].Opaque);
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const Symbol *Target = Obj.findSymbol(*Sym.WeakTargetSymbolId);
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if (Target == nullptr)
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return createStringError(object_error::invalid_symbol_index,
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"symbol '%s' is missing its weak target",
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Sym.Name.str().c_str());
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WE->TagIndex = Target->RawIndex;
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}
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}
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return Error::success();
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}
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void COFFWriter::layoutSections() {
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for (auto &S : Obj.getMutableSections()) {
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if (S.Header.SizeOfRawData > 0)
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S.Header.PointerToRawData = FileSize;
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FileSize += S.Header.SizeOfRawData; // For executables, this is already
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// aligned to FileAlignment.
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if (S.Relocs.size() >= 0xffff) {
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S.Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
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S.Header.NumberOfRelocations = 0xffff;
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S.Header.PointerToRelocations = FileSize;
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FileSize += sizeof(coff_relocation);
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} else {
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S.Header.NumberOfRelocations = S.Relocs.size();
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S.Header.PointerToRelocations = S.Relocs.size() ? FileSize : 0;
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}
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FileSize += S.Relocs.size() * sizeof(coff_relocation);
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FileSize = alignTo(FileSize, FileAlignment);
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if (S.Header.Characteristics & IMAGE_SCN_CNT_INITIALIZED_DATA)
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SizeOfInitializedData += S.Header.SizeOfRawData;
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}
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}
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size_t COFFWriter::finalizeStringTable() {
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for (const auto &S : Obj.getSections())
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if (S.Name.size() > COFF::NameSize)
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StrTabBuilder.add(S.Name);
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for (const auto &S : Obj.getSymbols())
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if (S.Name.size() > COFF::NameSize)
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StrTabBuilder.add(S.Name);
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StrTabBuilder.finalize();
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for (auto &S : Obj.getMutableSections()) {
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memset(S.Header.Name, 0, sizeof(S.Header.Name));
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if (S.Name.size() > COFF::NameSize) {
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snprintf(S.Header.Name, sizeof(S.Header.Name), "/%d",
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(int)StrTabBuilder.getOffset(S.Name));
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} else {
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memcpy(S.Header.Name, S.Name.data(), S.Name.size());
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}
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}
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for (auto &S : Obj.getMutableSymbols()) {
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if (S.Name.size() > COFF::NameSize) {
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S.Sym.Name.Offset.Zeroes = 0;
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S.Sym.Name.Offset.Offset = StrTabBuilder.getOffset(S.Name);
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} else {
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strncpy(S.Sym.Name.ShortName, S.Name.data(), COFF::NameSize);
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}
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}
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return StrTabBuilder.getSize();
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}
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template <class SymbolTy>
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std::pair<size_t, size_t> COFFWriter::finalizeSymbolTable() {
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size_t RawSymIndex = 0;
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for (auto &S : Obj.getMutableSymbols()) {
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// Symbols normally have NumberOfAuxSymbols set correctly all the time.
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// For file symbols, we need to know the output file's symbol size to be
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// able to calculate the number of slots it occupies.
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if (!S.AuxFile.empty())
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S.Sym.NumberOfAuxSymbols =
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alignTo(S.AuxFile.size(), sizeof(SymbolTy)) / sizeof(SymbolTy);
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S.RawIndex = RawSymIndex;
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RawSymIndex += 1 + S.Sym.NumberOfAuxSymbols;
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}
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return std::make_pair(RawSymIndex * sizeof(SymbolTy), sizeof(SymbolTy));
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}
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Error COFFWriter::finalize(bool IsBigObj) {
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size_t SymTabSize, SymbolSize;
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std::tie(SymTabSize, SymbolSize) = IsBigObj
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? finalizeSymbolTable<coff_symbol32>()
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: finalizeSymbolTable<coff_symbol16>();
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if (Error E = finalizeRelocTargets())
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return E;
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if (Error E = finalizeSymbolContents())
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return E;
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size_t SizeOfHeaders = 0;
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FileAlignment = 1;
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size_t PeHeaderSize = 0;
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if (Obj.IsPE) {
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Obj.DosHeader.AddressOfNewExeHeader =
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sizeof(Obj.DosHeader) + Obj.DosStub.size();
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SizeOfHeaders += Obj.DosHeader.AddressOfNewExeHeader + sizeof(PEMagic);
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FileAlignment = Obj.PeHeader.FileAlignment;
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Obj.PeHeader.NumberOfRvaAndSize = Obj.DataDirectories.size();
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PeHeaderSize = Obj.Is64 ? sizeof(pe32plus_header) : sizeof(pe32_header);
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SizeOfHeaders +=
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PeHeaderSize + sizeof(data_directory) * Obj.DataDirectories.size();
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}
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Obj.CoffFileHeader.NumberOfSections = Obj.getSections().size();
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SizeOfHeaders +=
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IsBigObj ? sizeof(coff_bigobj_file_header) : sizeof(coff_file_header);
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SizeOfHeaders += sizeof(coff_section) * Obj.getSections().size();
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SizeOfHeaders = alignTo(SizeOfHeaders, FileAlignment);
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Obj.CoffFileHeader.SizeOfOptionalHeader =
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PeHeaderSize + sizeof(data_directory) * Obj.DataDirectories.size();
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FileSize = SizeOfHeaders;
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SizeOfInitializedData = 0;
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layoutSections();
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if (Obj.IsPE) {
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Obj.PeHeader.SizeOfHeaders = SizeOfHeaders;
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Obj.PeHeader.SizeOfInitializedData = SizeOfInitializedData;
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if (!Obj.getSections().empty()) {
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const Section &S = Obj.getSections().back();
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Obj.PeHeader.SizeOfImage =
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alignTo(S.Header.VirtualAddress + S.Header.VirtualSize,
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Obj.PeHeader.SectionAlignment);
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}
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// If the PE header had a checksum, clear it, since it isn't valid
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// any longer. (We don't calculate a new one.)
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Obj.PeHeader.CheckSum = 0;
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}
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size_t StrTabSize = finalizeStringTable();
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size_t PointerToSymbolTable = FileSize;
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// StrTabSize <= 4 is the size of an empty string table, only consisting
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// of the length field.
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if (SymTabSize == 0 && StrTabSize <= 4 && Obj.IsPE) {
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// For executables, don't point to the symbol table and skip writing
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// the length field, if both the symbol and string tables are empty.
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PointerToSymbolTable = 0;
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StrTabSize = 0;
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}
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size_t NumRawSymbols = SymTabSize / SymbolSize;
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Obj.CoffFileHeader.PointerToSymbolTable = PointerToSymbolTable;
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Obj.CoffFileHeader.NumberOfSymbols = NumRawSymbols;
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FileSize += SymTabSize + StrTabSize;
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FileSize = alignTo(FileSize, FileAlignment);
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return Error::success();
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}
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void COFFWriter::writeHeaders(bool IsBigObj) {
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uint8_t *Ptr = Buf.getBufferStart();
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if (Obj.IsPE) {
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memcpy(Ptr, &Obj.DosHeader, sizeof(Obj.DosHeader));
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Ptr += sizeof(Obj.DosHeader);
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memcpy(Ptr, Obj.DosStub.data(), Obj.DosStub.size());
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Ptr += Obj.DosStub.size();
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memcpy(Ptr, PEMagic, sizeof(PEMagic));
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Ptr += sizeof(PEMagic);
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}
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if (!IsBigObj) {
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memcpy(Ptr, &Obj.CoffFileHeader, sizeof(Obj.CoffFileHeader));
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Ptr += sizeof(Obj.CoffFileHeader);
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} else {
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// Generate a coff_bigobj_file_header, filling it in with the values
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// from Obj.CoffFileHeader. All extra fields that don't exist in
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// coff_file_header can be set to hardcoded values.
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coff_bigobj_file_header BigObjHeader;
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BigObjHeader.Sig1 = IMAGE_FILE_MACHINE_UNKNOWN;
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BigObjHeader.Sig2 = 0xffff;
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BigObjHeader.Version = BigObjHeader::MinBigObjectVersion;
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BigObjHeader.Machine = Obj.CoffFileHeader.Machine;
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BigObjHeader.TimeDateStamp = Obj.CoffFileHeader.TimeDateStamp;
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memcpy(BigObjHeader.UUID, BigObjMagic, sizeof(BigObjMagic));
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BigObjHeader.unused1 = 0;
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BigObjHeader.unused2 = 0;
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BigObjHeader.unused3 = 0;
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BigObjHeader.unused4 = 0;
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// The value in Obj.CoffFileHeader.NumberOfSections is truncated, thus
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// get the original one instead.
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BigObjHeader.NumberOfSections = Obj.getSections().size();
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BigObjHeader.PointerToSymbolTable = Obj.CoffFileHeader.PointerToSymbolTable;
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BigObjHeader.NumberOfSymbols = Obj.CoffFileHeader.NumberOfSymbols;
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memcpy(Ptr, &BigObjHeader, sizeof(BigObjHeader));
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Ptr += sizeof(BigObjHeader);
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}
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if (Obj.IsPE) {
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if (Obj.Is64) {
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memcpy(Ptr, &Obj.PeHeader, sizeof(Obj.PeHeader));
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Ptr += sizeof(Obj.PeHeader);
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} else {
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pe32_header PeHeader;
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copyPeHeader(PeHeader, Obj.PeHeader);
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// The pe32plus_header (stored in Object) lacks the BaseOfData field.
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PeHeader.BaseOfData = Obj.BaseOfData;
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memcpy(Ptr, &PeHeader, sizeof(PeHeader));
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Ptr += sizeof(PeHeader);
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}
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for (const auto &DD : Obj.DataDirectories) {
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memcpy(Ptr, &DD, sizeof(DD));
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Ptr += sizeof(DD);
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}
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}
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for (const auto &S : Obj.getSections()) {
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memcpy(Ptr, &S.Header, sizeof(S.Header));
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Ptr += sizeof(S.Header);
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}
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}
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void COFFWriter::writeSections() {
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for (const auto &S : Obj.getSections()) {
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uint8_t *Ptr = Buf.getBufferStart() + S.Header.PointerToRawData;
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ArrayRef<uint8_t> Contents = S.getContents();
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std::copy(Contents.begin(), Contents.end(), Ptr);
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// For executable sections, pad the remainder of the raw data size with
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// 0xcc, which is int3 on x86.
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if ((S.Header.Characteristics & IMAGE_SCN_CNT_CODE) &&
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S.Header.SizeOfRawData > Contents.size())
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memset(Ptr + Contents.size(), 0xcc,
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S.Header.SizeOfRawData - Contents.size());
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Ptr += S.Header.SizeOfRawData;
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if (S.Relocs.size() >= 0xffff) {
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object::coff_relocation R;
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R.VirtualAddress = S.Relocs.size() + 1;
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R.SymbolTableIndex = 0;
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R.Type = 0;
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memcpy(Ptr, &R, sizeof(R));
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Ptr += sizeof(R);
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}
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for (const auto &R : S.Relocs) {
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memcpy(Ptr, &R.Reloc, sizeof(R.Reloc));
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Ptr += sizeof(R.Reloc);
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}
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}
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}
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template <class SymbolTy> void COFFWriter::writeSymbolStringTables() {
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uint8_t *Ptr = Buf.getBufferStart() + Obj.CoffFileHeader.PointerToSymbolTable;
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for (const auto &S : Obj.getSymbols()) {
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// Convert symbols back to the right size, from coff_symbol32.
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copySymbol<SymbolTy, coff_symbol32>(*reinterpret_cast<SymbolTy *>(Ptr),
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S.Sym);
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Ptr += sizeof(SymbolTy);
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if (!S.AuxFile.empty()) {
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// For file symbols, just write the string into the aux symbol slots,
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// assuming that the unwritten parts are initialized to zero in the memory
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// mapped file.
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std::copy(S.AuxFile.begin(), S.AuxFile.end(), Ptr);
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Ptr += S.Sym.NumberOfAuxSymbols * sizeof(SymbolTy);
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} else {
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// For other auxillary symbols, write their opaque payload into one symbol
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// table slot each. For big object files, the symbols are larger than the
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// opaque auxillary symbol struct and we leave padding at the end of each
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// entry.
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for (const AuxSymbol &AuxSym : S.AuxData) {
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ArrayRef<uint8_t> Ref = AuxSym.getRef();
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std::copy(Ref.begin(), Ref.end(), Ptr);
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Ptr += sizeof(SymbolTy);
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}
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}
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}
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if (StrTabBuilder.getSize() > 4 || !Obj.IsPE) {
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// Always write a string table in object files, even an empty one.
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StrTabBuilder.write(Ptr);
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Ptr += StrTabBuilder.getSize();
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}
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}
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Error COFFWriter::write(bool IsBigObj) {
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if (Error E = finalize(IsBigObj))
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return E;
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if (Error E = Buf.allocate(FileSize))
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return E;
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writeHeaders(IsBigObj);
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writeSections();
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if (IsBigObj)
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writeSymbolStringTables<coff_symbol32>();
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else
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writeSymbolStringTables<coff_symbol16>();
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if (Obj.IsPE)
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if (Error E = patchDebugDirectory())
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return E;
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return Buf.commit();
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}
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Expected<uint32_t> COFFWriter::virtualAddressToFileAddress(uint32_t RVA) {
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for (const auto &S : Obj.getSections()) {
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if (RVA >= S.Header.VirtualAddress &&
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RVA < S.Header.VirtualAddress + S.Header.SizeOfRawData)
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return S.Header.PointerToRawData + RVA - S.Header.VirtualAddress;
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}
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return createStringError(object_error::parse_failed,
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"debug directory payload not found");
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}
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// Locate which sections contain the debug directories, iterate over all
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// the debug_directory structs in there, and set the PointerToRawData field
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// in all of them, according to their new physical location in the file.
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Error COFFWriter::patchDebugDirectory() {
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if (Obj.DataDirectories.size() < DEBUG_DIRECTORY)
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return Error::success();
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const data_directory *Dir = &Obj.DataDirectories[DEBUG_DIRECTORY];
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if (Dir->Size <= 0)
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return Error::success();
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for (const auto &S : Obj.getSections()) {
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if (Dir->RelativeVirtualAddress >= S.Header.VirtualAddress &&
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Dir->RelativeVirtualAddress <
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S.Header.VirtualAddress + S.Header.SizeOfRawData) {
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if (Dir->RelativeVirtualAddress + Dir->Size >
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S.Header.VirtualAddress + S.Header.SizeOfRawData)
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return createStringError(object_error::parse_failed,
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"debug directory extends past end of section");
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size_t Offset = Dir->RelativeVirtualAddress - S.Header.VirtualAddress;
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uint8_t *Ptr = Buf.getBufferStart() + S.Header.PointerToRawData + Offset;
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uint8_t *End = Ptr + Dir->Size;
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while (Ptr < End) {
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debug_directory *Debug = reinterpret_cast<debug_directory *>(Ptr);
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if (!Debug->AddressOfRawData)
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return createStringError(object_error::parse_failed,
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"debug directory payload outside of "
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"mapped sections not supported");
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if (Expected<uint32_t> FilePosOrErr =
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virtualAddressToFileAddress(Debug->AddressOfRawData))
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Debug->PointerToRawData = *FilePosOrErr;
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else
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return FilePosOrErr.takeError();
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Ptr += sizeof(debug_directory);
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Offset += sizeof(debug_directory);
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}
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// Debug directory found and patched, all done.
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return Error::success();
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}
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}
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return createStringError(object_error::parse_failed,
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"debug directory not found");
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}
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Error COFFWriter::write() {
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bool IsBigObj = Obj.getSections().size() > MaxNumberOfSections16;
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if (IsBigObj && Obj.IsPE)
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return createStringError(object_error::parse_failed,
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"too many sections for executable");
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return write(IsBigObj);
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}
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} // end namespace coff
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} // end namespace objcopy
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} // end namespace llvm
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