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llvm-mirror/tools/llvm-objcopy/ELF/Object.cpp
Georgii Rymar 29cf2215d1 [llvm-objcopy] - Do not crash on object that has relocations but no symbol table. 
It was revealed by D69260.

Tool crashed when scanned relocations in a object without a symbol table.
This patch teaches it either to handle such objects (when relocations
does not use symbols we do not need a symbol table to proceed)
or to show an appropriate error otherwise.

Differential revision: https://reviews.llvm.org/D69304
2019-10-30 13:17:22 +03:00

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//===- Object.cpp ---------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "Object.h"
#include "llvm-objcopy.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/MC/MCTargetOptions.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Support/Compression.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FileOutputBuffer.h"
#include "llvm/Support/Path.h"
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <iterator>
#include <unordered_set>
#include <utility>
#include <vector>
namespace llvm {
namespace objcopy {
namespace elf {
using namespace object;
using namespace ELF;
template <class ELFT> void ELFWriter<ELFT>::writePhdr(const Segment &Seg) {
uint8_t *B = Buf.getBufferStart() + Obj.ProgramHdrSegment.Offset +
Seg.Index * sizeof(Elf_Phdr);
Elf_Phdr &Phdr = *reinterpret_cast<Elf_Phdr *>(B);
Phdr.p_type = Seg.Type;
Phdr.p_flags = Seg.Flags;
Phdr.p_offset = Seg.Offset;
Phdr.p_vaddr = Seg.VAddr;
Phdr.p_paddr = Seg.PAddr;
Phdr.p_filesz = Seg.FileSize;
Phdr.p_memsz = Seg.MemSize;
Phdr.p_align = Seg.Align;
}
Error SectionBase::removeSectionReferences(
bool AllowBrokenLinks,
function_ref<bool(const SectionBase *)> ToRemove) {
return Error::success();
}
Error SectionBase::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {
return Error::success();
}
void SectionBase::initialize(SectionTableRef SecTable) {}
void SectionBase::finalize() {}
void SectionBase::markSymbols() {}
void SectionBase::replaceSectionReferences(
const DenseMap<SectionBase *, SectionBase *> &) {}
template <class ELFT> void ELFWriter<ELFT>::writeShdr(const SectionBase &Sec) {
uint8_t *B = Buf.getBufferStart() + Sec.HeaderOffset;
Elf_Shdr &Shdr = *reinterpret_cast<Elf_Shdr *>(B);
Shdr.sh_name = Sec.NameIndex;
Shdr.sh_type = Sec.Type;
Shdr.sh_flags = Sec.Flags;
Shdr.sh_addr = Sec.Addr;
Shdr.sh_offset = Sec.Offset;
Shdr.sh_size = Sec.Size;
Shdr.sh_link = Sec.Link;
Shdr.sh_info = Sec.Info;
Shdr.sh_addralign = Sec.Align;
Shdr.sh_entsize = Sec.EntrySize;
}
template <class ELFT> void ELFSectionSizer<ELFT>::visit(Section &Sec) {}
template <class ELFT>
void ELFSectionSizer<ELFT>::visit(OwnedDataSection &Sec) {}
template <class ELFT>
void ELFSectionSizer<ELFT>::visit(StringTableSection &Sec) {}
template <class ELFT>
void ELFSectionSizer<ELFT>::visit(DynamicRelocationSection &Sec) {}
template <class ELFT>
void ELFSectionSizer<ELFT>::visit(SymbolTableSection &Sec) {
Sec.EntrySize = sizeof(Elf_Sym);
Sec.Size = Sec.Symbols.size() * Sec.EntrySize;
// Align to the largest field in Elf_Sym.
Sec.Align = ELFT::Is64Bits ? sizeof(Elf_Xword) : sizeof(Elf_Word);
}
template <class ELFT>
void ELFSectionSizer<ELFT>::visit(RelocationSection &Sec) {
Sec.EntrySize = Sec.Type == SHT_REL ? sizeof(Elf_Rel) : sizeof(Elf_Rela);
Sec.Size = Sec.Relocations.size() * Sec.EntrySize;
// Align to the largest field in Elf_Rel(a).
Sec.Align = ELFT::Is64Bits ? sizeof(Elf_Xword) : sizeof(Elf_Word);
}
template <class ELFT>
void ELFSectionSizer<ELFT>::visit(GnuDebugLinkSection &Sec) {}
template <class ELFT> void ELFSectionSizer<ELFT>::visit(GroupSection &Sec) {}
template <class ELFT>
void ELFSectionSizer<ELFT>::visit(SectionIndexSection &Sec) {}
template <class ELFT>
void ELFSectionSizer<ELFT>::visit(CompressedSection &Sec) {}
template <class ELFT>
void ELFSectionSizer<ELFT>::visit(DecompressedSection &Sec) {}
void BinarySectionWriter::visit(const SectionIndexSection &Sec) {
error("cannot write symbol section index table '" + Sec.Name + "' ");
}
void BinarySectionWriter::visit(const SymbolTableSection &Sec) {
error("cannot write symbol table '" + Sec.Name + "' out to binary");
}
void BinarySectionWriter::visit(const RelocationSection &Sec) {
error("cannot write relocation section '" + Sec.Name + "' out to binary");
}
void BinarySectionWriter::visit(const GnuDebugLinkSection &Sec) {
error("cannot write '" + Sec.Name + "' out to binary");
}
void BinarySectionWriter::visit(const GroupSection &Sec) {
error("cannot write '" + Sec.Name + "' out to binary");
}
void SectionWriter::visit(const Section &Sec) {
if (Sec.Type != SHT_NOBITS)
llvm::copy(Sec.Contents, Out.getBufferStart() + Sec.Offset);
}
static bool addressOverflows32bit(uint64_t Addr) {
// Sign extended 32 bit addresses (e.g 0xFFFFFFFF80000000) are ok
return Addr > UINT32_MAX && Addr + 0x80000000 > UINT32_MAX;
}
template <class T> static T checkedGetHex(StringRef S) {
T Value;
bool Fail = S.getAsInteger(16, Value);
assert(!Fail);
(void)Fail;
return Value;
}
// Fills exactly Len bytes of buffer with hexadecimal characters
// representing value 'X'
template <class T, class Iterator>
static Iterator utohexstr(T X, Iterator It, size_t Len) {
// Fill range with '0'
std::fill(It, It + Len, '0');
for (long I = Len - 1; I >= 0; --I) {
unsigned char Mod = static_cast<unsigned char>(X) & 15;
*(It + I) = hexdigit(Mod, false);
X >>= 4;
}
assert(X == 0);
return It + Len;
}
uint8_t IHexRecord::getChecksum(StringRef S) {
assert((S.size() & 1) == 0);
uint8_t Checksum = 0;
while (!S.empty()) {
Checksum += checkedGetHex<uint8_t>(S.take_front(2));
S = S.drop_front(2);
}
return -Checksum;
}
IHexLineData IHexRecord::getLine(uint8_t Type, uint16_t Addr,
ArrayRef<uint8_t> Data) {
IHexLineData Line(getLineLength(Data.size()));
assert(Line.size());
auto Iter = Line.begin();
*Iter++ = ':';
Iter = utohexstr(Data.size(), Iter, 2);
Iter = utohexstr(Addr, Iter, 4);
Iter = utohexstr(Type, Iter, 2);
for (uint8_t X : Data)
Iter = utohexstr(X, Iter, 2);
StringRef S(Line.data() + 1, std::distance(Line.begin() + 1, Iter));
Iter = utohexstr(getChecksum(S), Iter, 2);
*Iter++ = '\r';
*Iter++ = '\n';
assert(Iter == Line.end());
return Line;
}
static Error checkRecord(const IHexRecord &R) {
switch (R.Type) {
case IHexRecord::Data:
if (R.HexData.size() == 0)
return createStringError(
errc::invalid_argument,
"zero data length is not allowed for data records");
break;
case IHexRecord::EndOfFile:
break;
case IHexRecord::SegmentAddr:
// 20-bit segment address. Data length must be 2 bytes
// (4 bytes in hex)
if (R.HexData.size() != 4)
return createStringError(
errc::invalid_argument,
"segment address data should be 2 bytes in size");
break;
case IHexRecord::StartAddr80x86:
case IHexRecord::StartAddr:
if (R.HexData.size() != 8)
return createStringError(errc::invalid_argument,
"start address data should be 4 bytes in size");
// According to Intel HEX specification '03' record
// only specifies the code address within the 20-bit
// segmented address space of the 8086/80186. This
// means 12 high order bits should be zeroes.
if (R.Type == IHexRecord::StartAddr80x86 &&
R.HexData.take_front(3) != "000")
return createStringError(errc::invalid_argument,
"start address exceeds 20 bit for 80x86");
break;
case IHexRecord::ExtendedAddr:
// 16-31 bits of linear base address
if (R.HexData.size() != 4)
return createStringError(
errc::invalid_argument,
"extended address data should be 2 bytes in size");
break;
default:
// Unknown record type
return createStringError(errc::invalid_argument, "unknown record type: %u",
static_cast<unsigned>(R.Type));
}
return Error::success();
}
// Checks that IHEX line contains valid characters.
// This allows converting hexadecimal data to integers
// without extra verification.
static Error checkChars(StringRef Line) {
assert(!Line.empty());
if (Line[0] != ':')
return createStringError(errc::invalid_argument,
"missing ':' in the beginning of line.");
for (size_t Pos = 1; Pos < Line.size(); ++Pos)
if (hexDigitValue(Line[Pos]) == -1U)
return createStringError(errc::invalid_argument,
"invalid character at position %zu.", Pos + 1);
return Error::success();
}
Expected<IHexRecord> IHexRecord::parse(StringRef Line) {
assert(!Line.empty());
// ':' + Length + Address + Type + Checksum with empty data ':LLAAAATTCC'
if (Line.size() < 11)
return createStringError(errc::invalid_argument,
"line is too short: %zu chars.", Line.size());
if (Error E = checkChars(Line))
return std::move(E);
IHexRecord Rec;
size_t DataLen = checkedGetHex<uint8_t>(Line.substr(1, 2));
if (Line.size() != getLength(DataLen))
return createStringError(errc::invalid_argument,
"invalid line length %zu (should be %zu)",
Line.size(), getLength(DataLen));
Rec.Addr = checkedGetHex<uint16_t>(Line.substr(3, 4));
Rec.Type = checkedGetHex<uint8_t>(Line.substr(7, 2));
Rec.HexData = Line.substr(9, DataLen * 2);
if (getChecksum(Line.drop_front(1)) != 0)
return createStringError(errc::invalid_argument, "incorrect checksum.");
if (Error E = checkRecord(Rec))
return std::move(E);
return Rec;
}
static uint64_t sectionPhysicalAddr(const SectionBase *Sec) {
Segment *Seg = Sec->ParentSegment;
if (Seg && Seg->Type != ELF::PT_LOAD)
Seg = nullptr;
return Seg ? Seg->PAddr + Sec->OriginalOffset - Seg->OriginalOffset
: Sec->Addr;
}
void IHexSectionWriterBase::writeSection(const SectionBase *Sec,
ArrayRef<uint8_t> Data) {
assert(Data.size() == Sec->Size);
const uint32_t ChunkSize = 16;
uint32_t Addr = sectionPhysicalAddr(Sec) & 0xFFFFFFFFU;
while (!Data.empty()) {
uint64_t DataSize = std::min<uint64_t>(Data.size(), ChunkSize);
if (Addr > SegmentAddr + BaseAddr + 0xFFFFU) {
if (Addr > 0xFFFFFU) {
// Write extended address record, zeroing segment address
// if needed.
if (SegmentAddr != 0)
SegmentAddr = writeSegmentAddr(0U);
BaseAddr = writeBaseAddr(Addr);
} else {
// We can still remain 16-bit
SegmentAddr = writeSegmentAddr(Addr);
}
}
uint64_t SegOffset = Addr - BaseAddr - SegmentAddr;
assert(SegOffset <= 0xFFFFU);
DataSize = std::min(DataSize, 0x10000U - SegOffset);
writeData(0, SegOffset, Data.take_front(DataSize));
Addr += DataSize;
Data = Data.drop_front(DataSize);
}
}
uint64_t IHexSectionWriterBase::writeSegmentAddr(uint64_t Addr) {
assert(Addr <= 0xFFFFFU);
uint8_t Data[] = {static_cast<uint8_t>((Addr & 0xF0000U) >> 12), 0};
writeData(2, 0, Data);
return Addr & 0xF0000U;
}
uint64_t IHexSectionWriterBase::writeBaseAddr(uint64_t Addr) {
assert(Addr <= 0xFFFFFFFFU);
uint64_t Base = Addr & 0xFFFF0000U;
uint8_t Data[] = {static_cast<uint8_t>(Base >> 24),
static_cast<uint8_t>((Base >> 16) & 0xFF)};
writeData(4, 0, Data);
return Base;
}
void IHexSectionWriterBase::writeData(uint8_t Type, uint16_t Addr,
ArrayRef<uint8_t> Data) {
Offset += IHexRecord::getLineLength(Data.size());
}
void IHexSectionWriterBase::visit(const Section &Sec) {
writeSection(&Sec, Sec.Contents);
}
void IHexSectionWriterBase::visit(const OwnedDataSection &Sec) {
writeSection(&Sec, Sec.Data);
}
void IHexSectionWriterBase::visit(const StringTableSection &Sec) {
// Check that sizer has already done its work
assert(Sec.Size == Sec.StrTabBuilder.getSize());
// We are free to pass an invalid pointer to writeSection as long
// as we don't actually write any data. The real writer class has
// to override this method .
writeSection(&Sec, {nullptr, static_cast<size_t>(Sec.Size)});
}
void IHexSectionWriterBase::visit(const DynamicRelocationSection &Sec) {
writeSection(&Sec, Sec.Contents);
}
void IHexSectionWriter::writeData(uint8_t Type, uint16_t Addr,
ArrayRef<uint8_t> Data) {
IHexLineData HexData = IHexRecord::getLine(Type, Addr, Data);
memcpy(Out.getBufferStart() + Offset, HexData.data(), HexData.size());
Offset += HexData.size();
}
void IHexSectionWriter::visit(const StringTableSection &Sec) {
assert(Sec.Size == Sec.StrTabBuilder.getSize());
std::vector<uint8_t> Data(Sec.Size);
Sec.StrTabBuilder.write(Data.data());
writeSection(&Sec, Data);
}
void Section::accept(SectionVisitor &Visitor) const { Visitor.visit(*this); }
void Section::accept(MutableSectionVisitor &Visitor) { Visitor.visit(*this); }
void SectionWriter::visit(const OwnedDataSection &Sec) {
llvm::copy(Sec.Data, Out.getBufferStart() + Sec.Offset);
}
static constexpr std::array<uint8_t, 4> ZlibGnuMagic = {{'Z', 'L', 'I', 'B'}};
static bool isDataGnuCompressed(ArrayRef<uint8_t> Data) {
return Data.size() > ZlibGnuMagic.size() &&
std::equal(ZlibGnuMagic.begin(), ZlibGnuMagic.end(), Data.data());
}
template <class ELFT>
static std::tuple<uint64_t, uint64_t>
getDecompressedSizeAndAlignment(ArrayRef<uint8_t> Data) {
const bool IsGnuDebug = isDataGnuCompressed(Data);
const uint64_t DecompressedSize =
IsGnuDebug
? support::endian::read64be(Data.data() + ZlibGnuMagic.size())
: reinterpret_cast<const Elf_Chdr_Impl<ELFT> *>(Data.data())->ch_size;
const uint64_t DecompressedAlign =
IsGnuDebug ? 1
: reinterpret_cast<const Elf_Chdr_Impl<ELFT> *>(Data.data())
->ch_addralign;
return std::make_tuple(DecompressedSize, DecompressedAlign);
}
template <class ELFT>
void ELFSectionWriter<ELFT>::visit(const DecompressedSection &Sec) {
const size_t DataOffset = isDataGnuCompressed(Sec.OriginalData)
? (ZlibGnuMagic.size() + sizeof(Sec.Size))
: sizeof(Elf_Chdr_Impl<ELFT>);
StringRef CompressedContent(
reinterpret_cast<const char *>(Sec.OriginalData.data()) + DataOffset,
Sec.OriginalData.size() - DataOffset);
SmallVector<char, 128> DecompressedContent;
if (Error E = zlib::uncompress(CompressedContent, DecompressedContent,
static_cast<size_t>(Sec.Size)))
reportError(Sec.Name, std::move(E));
uint8_t *Buf = Out.getBufferStart() + Sec.Offset;
std::copy(DecompressedContent.begin(), DecompressedContent.end(), Buf);
}
void BinarySectionWriter::visit(const DecompressedSection &Sec) {
error("cannot write compressed section '" + Sec.Name + "' ");
}
void DecompressedSection::accept(SectionVisitor &Visitor) const {
Visitor.visit(*this);
}
void DecompressedSection::accept(MutableSectionVisitor &Visitor) {
Visitor.visit(*this);
}
void OwnedDataSection::accept(SectionVisitor &Visitor) const {
Visitor.visit(*this);
}
void OwnedDataSection::accept(MutableSectionVisitor &Visitor) {
Visitor.visit(*this);
}
void OwnedDataSection::appendHexData(StringRef HexData) {
assert((HexData.size() & 1) == 0);
while (!HexData.empty()) {
Data.push_back(checkedGetHex<uint8_t>(HexData.take_front(2)));
HexData = HexData.drop_front(2);
}
Size = Data.size();
}
void BinarySectionWriter::visit(const CompressedSection &Sec) {
error("cannot write compressed section '" + Sec.Name + "' ");
}
template <class ELFT>
void ELFSectionWriter<ELFT>::visit(const CompressedSection &Sec) {
uint8_t *Buf = Out.getBufferStart() + Sec.Offset;
if (Sec.CompressionType == DebugCompressionType::None) {
std::copy(Sec.OriginalData.begin(), Sec.OriginalData.end(), Buf);
return;
}
if (Sec.CompressionType == DebugCompressionType::GNU) {
const char *Magic = "ZLIB";
memcpy(Buf, Magic, strlen(Magic));
Buf += strlen(Magic);
const uint64_t DecompressedSize =
support::endian::read64be(&Sec.DecompressedSize);
memcpy(Buf, &DecompressedSize, sizeof(DecompressedSize));
Buf += sizeof(DecompressedSize);
} else {
Elf_Chdr_Impl<ELFT> Chdr;
Chdr.ch_type = ELF::ELFCOMPRESS_ZLIB;
Chdr.ch_size = Sec.DecompressedSize;
Chdr.ch_addralign = Sec.DecompressedAlign;
memcpy(Buf, &Chdr, sizeof(Chdr));
Buf += sizeof(Chdr);
}
std::copy(Sec.CompressedData.begin(), Sec.CompressedData.end(), Buf);
}
CompressedSection::CompressedSection(const SectionBase &Sec,
DebugCompressionType CompressionType)
: SectionBase(Sec), CompressionType(CompressionType),
DecompressedSize(Sec.OriginalData.size()), DecompressedAlign(Sec.Align) {
if (Error E = zlib::compress(
StringRef(reinterpret_cast<const char *>(OriginalData.data()),
OriginalData.size()),
CompressedData))
reportError(Name, std::move(E));
size_t ChdrSize;
if (CompressionType == DebugCompressionType::GNU) {
Name = ".z" + Sec.Name.substr(1);
ChdrSize = sizeof("ZLIB") - 1 + sizeof(uint64_t);
} else {
Flags |= ELF::SHF_COMPRESSED;
ChdrSize =
std::max(std::max(sizeof(object::Elf_Chdr_Impl<object::ELF64LE>),
sizeof(object::Elf_Chdr_Impl<object::ELF64BE>)),
std::max(sizeof(object::Elf_Chdr_Impl<object::ELF32LE>),
sizeof(object::Elf_Chdr_Impl<object::ELF32BE>)));
}
Size = ChdrSize + CompressedData.size();
Align = 8;
}
CompressedSection::CompressedSection(ArrayRef<uint8_t> CompressedData,
uint64_t DecompressedSize,
uint64_t DecompressedAlign)
: CompressionType(DebugCompressionType::None),
DecompressedSize(DecompressedSize), DecompressedAlign(DecompressedAlign) {
OriginalData = CompressedData;
}
void CompressedSection::accept(SectionVisitor &Visitor) const {
Visitor.visit(*this);
}
void CompressedSection::accept(MutableSectionVisitor &Visitor) {
Visitor.visit(*this);
}
void StringTableSection::addString(StringRef Name) { StrTabBuilder.add(Name); }
uint32_t StringTableSection::findIndex(StringRef Name) const {
return StrTabBuilder.getOffset(Name);
}
void StringTableSection::prepareForLayout() {
StrTabBuilder.finalize();
Size = StrTabBuilder.getSize();
}
void SectionWriter::visit(const StringTableSection &Sec) {
Sec.StrTabBuilder.write(Out.getBufferStart() + Sec.Offset);
}
void StringTableSection::accept(SectionVisitor &Visitor) const {
Visitor.visit(*this);
}
void StringTableSection::accept(MutableSectionVisitor &Visitor) {
Visitor.visit(*this);
}
template <class ELFT>
void ELFSectionWriter<ELFT>::visit(const SectionIndexSection &Sec) {
uint8_t *Buf = Out.getBufferStart() + Sec.Offset;
llvm::copy(Sec.Indexes, reinterpret_cast<Elf_Word *>(Buf));
}
void SectionIndexSection::initialize(SectionTableRef SecTable) {
Size = 0;
setSymTab(SecTable.getSectionOfType<SymbolTableSection>(
Link,
"Link field value " + Twine(Link) + " in section " + Name + " is invalid",
"Link field value " + Twine(Link) + " in section " + Name +
" is not a symbol table"));
Symbols->setShndxTable(this);
}
void SectionIndexSection::finalize() { Link = Symbols->Index; }
void SectionIndexSection::accept(SectionVisitor &Visitor) const {
Visitor.visit(*this);
}
void SectionIndexSection::accept(MutableSectionVisitor &Visitor) {
Visitor.visit(*this);
}
static bool isValidReservedSectionIndex(uint16_t Index, uint16_t Machine) {
switch (Index) {
case SHN_ABS:
case SHN_COMMON:
return true;
}
if (Machine == EM_AMDGPU) {
return Index == SHN_AMDGPU_LDS;
}
if (Machine == EM_HEXAGON) {
switch (Index) {
case SHN_HEXAGON_SCOMMON:
case SHN_HEXAGON_SCOMMON_2:
case SHN_HEXAGON_SCOMMON_4:
case SHN_HEXAGON_SCOMMON_8:
return true;
}
}
return false;
}
// Large indexes force us to clarify exactly what this function should do. This
// function should return the value that will appear in st_shndx when written
// out.
uint16_t Symbol::getShndx() const {
if (DefinedIn != nullptr) {
if (DefinedIn->Index >= SHN_LORESERVE)
return SHN_XINDEX;
return DefinedIn->Index;
}
if (ShndxType == SYMBOL_SIMPLE_INDEX) {
// This means that we don't have a defined section but we do need to
// output a legitimate section index.
return SHN_UNDEF;
}
assert(ShndxType == SYMBOL_ABS || ShndxType == SYMBOL_COMMON ||
(ShndxType >= SYMBOL_LOPROC && ShndxType <= SYMBOL_HIPROC) ||
(ShndxType >= SYMBOL_LOOS && ShndxType <= SYMBOL_HIOS));
return static_cast<uint16_t>(ShndxType);
}
bool Symbol::isCommon() const { return getShndx() == SHN_COMMON; }
void SymbolTableSection::assignIndices() {
uint32_t Index = 0;
for (auto &Sym : Symbols)
Sym->Index = Index++;
}
void SymbolTableSection::addSymbol(Twine Name, uint8_t Bind, uint8_t Type,
SectionBase *DefinedIn, uint64_t Value,
uint8_t Visibility, uint16_t Shndx,
uint64_t SymbolSize) {
Symbol Sym;
Sym.Name = Name.str();
Sym.Binding = Bind;
Sym.Type = Type;
Sym.DefinedIn = DefinedIn;
if (DefinedIn != nullptr)
DefinedIn->HasSymbol = true;
if (DefinedIn == nullptr) {
if (Shndx >= SHN_LORESERVE)
Sym.ShndxType = static_cast<SymbolShndxType>(Shndx);
else
Sym.ShndxType = SYMBOL_SIMPLE_INDEX;
}
Sym.Value = Value;
Sym.Visibility = Visibility;
Sym.Size = SymbolSize;
Sym.Index = Symbols.size();
Symbols.emplace_back(std::make_unique<Symbol>(Sym));
Size += this->EntrySize;
}
Error SymbolTableSection::removeSectionReferences(
bool AllowBrokenLinks,
function_ref<bool(const SectionBase *)> ToRemove) {
if (ToRemove(SectionIndexTable))
SectionIndexTable = nullptr;
if (ToRemove(SymbolNames)) {
if (!AllowBrokenLinks)
return createStringError(
llvm::errc::invalid_argument,
"string table '%s' cannot be removed because it is "
"referenced by the symbol table '%s'",
SymbolNames->Name.data(), this->Name.data());
SymbolNames = nullptr;
}
return removeSymbols(
[ToRemove](const Symbol &Sym) { return ToRemove(Sym.DefinedIn); });
}
void SymbolTableSection::updateSymbols(function_ref<void(Symbol &)> Callable) {
std::for_each(std::begin(Symbols) + 1, std::end(Symbols),
[Callable](SymPtr &Sym) { Callable(*Sym); });
std::stable_partition(
std::begin(Symbols), std::end(Symbols),
[](const SymPtr &Sym) { return Sym->Binding == STB_LOCAL; });
assignIndices();
}
Error SymbolTableSection::removeSymbols(
function_ref<bool(const Symbol &)> ToRemove) {
Symbols.erase(
std::remove_if(std::begin(Symbols) + 1, std::end(Symbols),
[ToRemove](const SymPtr &Sym) { return ToRemove(*Sym); }),
std::end(Symbols));
Size = Symbols.size() * EntrySize;
assignIndices();
return Error::success();
}
void SymbolTableSection::replaceSectionReferences(
const DenseMap<SectionBase *, SectionBase *> &FromTo) {
for (std::unique_ptr<Symbol> &Sym : Symbols)
if (SectionBase *To = FromTo.lookup(Sym->DefinedIn))
Sym->DefinedIn = To;
}
void SymbolTableSection::initialize(SectionTableRef SecTable) {
Size = 0;
setStrTab(SecTable.getSectionOfType<StringTableSection>(
Link,
"Symbol table has link index of " + Twine(Link) +
" which is not a valid index",
"Symbol table has link index of " + Twine(Link) +
" which is not a string table"));
}
void SymbolTableSection::finalize() {
uint32_t MaxLocalIndex = 0;
for (std::unique_ptr<Symbol> &Sym : Symbols) {
Sym->NameIndex =
SymbolNames == nullptr ? 0 : SymbolNames->findIndex(Sym->Name);
if (Sym->Binding == STB_LOCAL)
MaxLocalIndex = std::max(MaxLocalIndex, Sym->Index);
}
// Now we need to set the Link and Info fields.
Link = SymbolNames == nullptr ? 0 : SymbolNames->Index;
Info = MaxLocalIndex + 1;
}
void SymbolTableSection::prepareForLayout() {
// Reserve proper amount of space in section index table, so we can
// layout sections correctly. We will fill the table with correct
// indexes later in fillShdnxTable.
if (SectionIndexTable)
SectionIndexTable->reserve(Symbols.size());
// Add all of our strings to SymbolNames so that SymbolNames has the right
// size before layout is decided.
// If the symbol names section has been removed, don't try to add strings to
// the table.
if (SymbolNames != nullptr)
for (std::unique_ptr<Symbol> &Sym : Symbols)
SymbolNames->addString(Sym->Name);
}
void SymbolTableSection::fillShndxTable() {
if (SectionIndexTable == nullptr)
return;
// Fill section index table with real section indexes. This function must
// be called after assignOffsets.
for (const std::unique_ptr<Symbol> &Sym : Symbols) {
if (Sym->DefinedIn != nullptr && Sym->DefinedIn->Index >= SHN_LORESERVE)
SectionIndexTable->addIndex(Sym->DefinedIn->Index);
else
SectionIndexTable->addIndex(SHN_UNDEF);
}
}
const Symbol *SymbolTableSection::getSymbolByIndex(uint32_t Index) const {
if (Symbols.size() <= Index)
error("invalid symbol index: " + Twine(Index));
return Symbols[Index].get();
}
Symbol *SymbolTableSection::getSymbolByIndex(uint32_t Index) {
return const_cast<Symbol *>(
static_cast<const SymbolTableSection *>(this)->getSymbolByIndex(Index));
}
template <class ELFT>
void ELFSectionWriter<ELFT>::visit(const SymbolTableSection &Sec) {
Elf_Sym *Sym = reinterpret_cast<Elf_Sym *>(Out.getBufferStart() + Sec.Offset);
// Loop though symbols setting each entry of the symbol table.
for (const std::unique_ptr<Symbol> &Symbol : Sec.Symbols) {
Sym->st_name = Symbol->NameIndex;
Sym->st_value = Symbol->Value;
Sym->st_size = Symbol->Size;
Sym->st_other = Symbol->Visibility;
Sym->setBinding(Symbol->Binding);
Sym->setType(Symbol->Type);
Sym->st_shndx = Symbol->getShndx();
++Sym;
}
}
void SymbolTableSection::accept(SectionVisitor &Visitor) const {
Visitor.visit(*this);
}
void SymbolTableSection::accept(MutableSectionVisitor &Visitor) {
Visitor.visit(*this);
}
Error RelocationSection::removeSectionReferences(
bool AllowBrokenLinks,
function_ref<bool(const SectionBase *)> ToRemove) {
if (ToRemove(Symbols)) {
if (!AllowBrokenLinks)
return createStringError(
llvm::errc::invalid_argument,
"symbol table '%s' cannot be removed because it is "
"referenced by the relocation section '%s'",
Symbols->Name.data(), this->Name.data());
Symbols = nullptr;
}
for (const Relocation &R : Relocations) {
if (!R.RelocSymbol || !R.RelocSymbol->DefinedIn ||
!ToRemove(R.RelocSymbol->DefinedIn))
continue;
return createStringError(llvm::errc::invalid_argument,
"section '%s' cannot be removed: (%s+0x%" PRIx64
") has relocation against symbol '%s'",
R.RelocSymbol->DefinedIn->Name.data(),
SecToApplyRel->Name.data(), R.Offset,
R.RelocSymbol->Name.c_str());
}
return Error::success();
}
template <class SymTabType>
void RelocSectionWithSymtabBase<SymTabType>::initialize(
SectionTableRef SecTable) {
if (Link != SHN_UNDEF)
setSymTab(SecTable.getSectionOfType<SymTabType>(
Link,
"Link field value " + Twine(Link) + " in section " + Name +
" is invalid",
"Link field value " + Twine(Link) + " in section " + Name +
" is not a symbol table"));
if (Info != SHN_UNDEF)
setSection(SecTable.getSection(Info, "Info field value " + Twine(Info) +
" in section " + Name +
" is invalid"));
else
setSection(nullptr);
}
template <class SymTabType>
void RelocSectionWithSymtabBase<SymTabType>::finalize() {
this->Link = Symbols ? Symbols->Index : 0;
if (SecToApplyRel != nullptr)
this->Info = SecToApplyRel->Index;
}
template <class ELFT>
static void setAddend(Elf_Rel_Impl<ELFT, false> &Rel, uint64_t Addend) {}
template <class ELFT>
static void setAddend(Elf_Rel_Impl<ELFT, true> &Rela, uint64_t Addend) {
Rela.r_addend = Addend;
}
template <class RelRange, class T>
static void writeRel(const RelRange &Relocations, T *Buf) {
for (const auto &Reloc : Relocations) {
Buf->r_offset = Reloc.Offset;
setAddend(*Buf, Reloc.Addend);
Buf->setSymbolAndType(Reloc.RelocSymbol ? Reloc.RelocSymbol->Index : 0,
Reloc.Type, false);
++Buf;
}
}
template <class ELFT>
void ELFSectionWriter<ELFT>::visit(const RelocationSection &Sec) {
uint8_t *Buf = Out.getBufferStart() + Sec.Offset;
if (Sec.Type == SHT_REL)
writeRel(Sec.Relocations, reinterpret_cast<Elf_Rel *>(Buf));
else
writeRel(Sec.Relocations, reinterpret_cast<Elf_Rela *>(Buf));
}
void RelocationSection::accept(SectionVisitor &Visitor) const {
Visitor.visit(*this);
}
void RelocationSection::accept(MutableSectionVisitor &Visitor) {
Visitor.visit(*this);
}
Error RelocationSection::removeSymbols(
function_ref<bool(const Symbol &)> ToRemove) {
for (const Relocation &Reloc : Relocations)
if (Reloc.RelocSymbol && ToRemove(*Reloc.RelocSymbol))
return createStringError(
llvm::errc::invalid_argument,
"not stripping symbol '%s' because it is named in a relocation",
Reloc.RelocSymbol->Name.data());
return Error::success();
}
void RelocationSection::markSymbols() {
for (const Relocation &Reloc : Relocations)
if (Reloc.RelocSymbol)
Reloc.RelocSymbol->Referenced = true;
}
void RelocationSection::replaceSectionReferences(
const DenseMap<SectionBase *, SectionBase *> &FromTo) {
// Update the target section if it was replaced.
if (SectionBase *To = FromTo.lookup(SecToApplyRel))
SecToApplyRel = To;
}
void SectionWriter::visit(const DynamicRelocationSection &Sec) {
llvm::copy(Sec.Contents, Out.getBufferStart() + Sec.Offset);
}
void DynamicRelocationSection::accept(SectionVisitor &Visitor) const {
Visitor.visit(*this);
}
void DynamicRelocationSection::accept(MutableSectionVisitor &Visitor) {
Visitor.visit(*this);
}
Error DynamicRelocationSection::removeSectionReferences(
bool AllowBrokenLinks, function_ref<bool(const SectionBase *)> ToRemove) {
if (ToRemove(Symbols)) {
if (!AllowBrokenLinks)
return createStringError(
llvm::errc::invalid_argument,
"symbol table '%s' cannot be removed because it is "
"referenced by the relocation section '%s'",
Symbols->Name.data(), this->Name.data());
Symbols = nullptr;
}
// SecToApplyRel contains a section referenced by sh_info field. It keeps
// a section to which the relocation section applies. When we remove any
// sections we also remove their relocation sections. Since we do that much
// earlier, this assert should never be triggered.
assert(!SecToApplyRel || !ToRemove(SecToApplyRel));
return Error::success();
}
Error Section::removeSectionReferences(
bool AllowBrokenDependency,
function_ref<bool(const SectionBase *)> ToRemove) {
if (ToRemove(LinkSection)) {
if (!AllowBrokenDependency)
return createStringError(llvm::errc::invalid_argument,
"section '%s' cannot be removed because it is "
"referenced by the section '%s'",
LinkSection->Name.data(), this->Name.data());
LinkSection = nullptr;
}
return Error::success();
}
void GroupSection::finalize() {
this->Info = Sym->Index;
this->Link = SymTab->Index;
}
Error GroupSection::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {
if (ToRemove(*Sym))
return createStringError(llvm::errc::invalid_argument,
"symbol '%s' cannot be removed because it is "
"referenced by the section '%s[%d]'",
Sym->Name.data(), this->Name.data(), this->Index);
return Error::success();
}
void GroupSection::markSymbols() {
if (Sym)
Sym->Referenced = true;
}
void GroupSection::replaceSectionReferences(
const DenseMap<SectionBase *, SectionBase *> &FromTo) {
for (SectionBase *&Sec : GroupMembers)
if (SectionBase *To = FromTo.lookup(Sec))
Sec = To;
}
void Section::initialize(SectionTableRef SecTable) {
if (Link == ELF::SHN_UNDEF)
return;
LinkSection =
SecTable.getSection(Link, "Link field value " + Twine(Link) +
" in section " + Name + " is invalid");
if (LinkSection->Type == ELF::SHT_SYMTAB)
LinkSection = nullptr;
}
void Section::finalize() { this->Link = LinkSection ? LinkSection->Index : 0; }
void GnuDebugLinkSection::init(StringRef File) {
FileName = sys::path::filename(File);
// The format for the .gnu_debuglink starts with the file name and is
// followed by a null terminator and then the CRC32 of the file. The CRC32
// should be 4 byte aligned. So we add the FileName size, a 1 for the null
// byte, and then finally push the size to alignment and add 4.
Size = alignTo(FileName.size() + 1, 4) + 4;
// The CRC32 will only be aligned if we align the whole section.
Align = 4;
Type = ELF::SHT_PROGBITS;
Name = ".gnu_debuglink";
// For sections not found in segments, OriginalOffset is only used to
// establish the order that sections should go in. By using the maximum
// possible offset we cause this section to wind up at the end.
OriginalOffset = std::numeric_limits<uint64_t>::max();
}
GnuDebugLinkSection::GnuDebugLinkSection(StringRef File,
uint32_t PrecomputedCRC)
: FileName(File), CRC32(PrecomputedCRC) {
init(File);
}
template <class ELFT>
void ELFSectionWriter<ELFT>::visit(const GnuDebugLinkSection &Sec) {
unsigned char *Buf = Out.getBufferStart() + Sec.Offset;
Elf_Word *CRC =
reinterpret_cast<Elf_Word *>(Buf + Sec.Size - sizeof(Elf_Word));
*CRC = Sec.CRC32;
llvm::copy(Sec.FileName, Buf);
}
void GnuDebugLinkSection::accept(SectionVisitor &Visitor) const {
Visitor.visit(*this);
}
void GnuDebugLinkSection::accept(MutableSectionVisitor &Visitor) {
Visitor.visit(*this);
}
template <class ELFT>
void ELFSectionWriter<ELFT>::visit(const GroupSection &Sec) {
ELF::Elf32_Word *Buf =
reinterpret_cast<ELF::Elf32_Word *>(Out.getBufferStart() + Sec.Offset);
*Buf++ = Sec.FlagWord;
for (SectionBase *S : Sec.GroupMembers)
support::endian::write32<ELFT::TargetEndianness>(Buf++, S->Index);
}
void GroupSection::accept(SectionVisitor &Visitor) const {
Visitor.visit(*this);
}
void GroupSection::accept(MutableSectionVisitor &Visitor) {
Visitor.visit(*this);
}
// Returns true IFF a section is wholly inside the range of a segment
static bool sectionWithinSegment(const SectionBase &Sec, const Segment &Seg) {
// If a section is empty it should be treated like it has a size of 1. This is
// to clarify the case when an empty section lies on a boundary between two
// segments and ensures that the section "belongs" to the second segment and
// not the first.
uint64_t SecSize = Sec.Size ? Sec.Size : 1;
if (Sec.Type == SHT_NOBITS) {
if (!(Sec.Flags & SHF_ALLOC))
return false;
bool SectionIsTLS = Sec.Flags & SHF_TLS;
bool SegmentIsTLS = Seg.Type == PT_TLS;
if (SectionIsTLS != SegmentIsTLS)
return false;
return Seg.VAddr <= Sec.Addr &&
Seg.VAddr + Seg.MemSize >= Sec.Addr + SecSize;
}
return Seg.Offset <= Sec.OriginalOffset &&
Seg.Offset + Seg.FileSize >= Sec.OriginalOffset + SecSize;
}
// Returns true IFF a segment's original offset is inside of another segment's
// range.
static bool segmentOverlapsSegment(const Segment &Child,
const Segment &Parent) {
return Parent.OriginalOffset <= Child.OriginalOffset &&
Parent.OriginalOffset + Parent.FileSize > Child.OriginalOffset;
}
static bool compareSegmentsByOffset(const Segment *A, const Segment *B) {
// Any segment without a parent segment should come before a segment
// that has a parent segment.
if (A->OriginalOffset < B->OriginalOffset)
return true;
if (A->OriginalOffset > B->OriginalOffset)
return false;
return A->Index < B->Index;
}
static bool compareSegmentsByPAddr(const Segment *A, const Segment *B) {
if (A->PAddr < B->PAddr)
return true;
if (A->PAddr > B->PAddr)
return false;
return A->Index < B->Index;
}
void BasicELFBuilder::initFileHeader() {
Obj->Flags = 0x0;
Obj->Type = ET_REL;
Obj->OSABI = ELFOSABI_NONE;
Obj->ABIVersion = 0;
Obj->Entry = 0x0;
Obj->Machine = EM_NONE;
Obj->Version = 1;
}
void BasicELFBuilder::initHeaderSegment() { Obj->ElfHdrSegment.Index = 0; }
StringTableSection *BasicELFBuilder::addStrTab() {
auto &StrTab = Obj->addSection<StringTableSection>();
StrTab.Name = ".strtab";
Obj->SectionNames = &StrTab;
return &StrTab;
}
SymbolTableSection *BasicELFBuilder::addSymTab(StringTableSection *StrTab) {
auto &SymTab = Obj->addSection<SymbolTableSection>();
SymTab.Name = ".symtab";
SymTab.Link = StrTab->Index;
// The symbol table always needs a null symbol
SymTab.addSymbol("", 0, 0, nullptr, 0, 0, 0, 0);
Obj->SymbolTable = &SymTab;
return &SymTab;
}
void BasicELFBuilder::initSections() {
for (SectionBase &Sec : Obj->sections())
Sec.initialize(Obj->sections());
}
void BinaryELFBuilder::addData(SymbolTableSection *SymTab) {
auto Data = ArrayRef<uint8_t>(
reinterpret_cast<const uint8_t *>(MemBuf->getBufferStart()),
MemBuf->getBufferSize());
auto &DataSection = Obj->addSection<Section>(Data);
DataSection.Name = ".data";
DataSection.Type = ELF::SHT_PROGBITS;
DataSection.Size = Data.size();
DataSection.Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
std::string SanitizedFilename = MemBuf->getBufferIdentifier().str();
std::replace_if(std::begin(SanitizedFilename), std::end(SanitizedFilename),
[](char C) { return !isalnum(C); }, '_');
Twine Prefix = Twine("_binary_") + SanitizedFilename;
SymTab->addSymbol(Prefix + "_start", STB_GLOBAL, STT_NOTYPE, &DataSection,
/*Value=*/0, NewSymbolVisibility, 0, 0);
SymTab->addSymbol(Prefix + "_end", STB_GLOBAL, STT_NOTYPE, &DataSection,
/*Value=*/DataSection.Size, NewSymbolVisibility, 0, 0);
SymTab->addSymbol(Prefix + "_size", STB_GLOBAL, STT_NOTYPE, nullptr,
/*Value=*/DataSection.Size, NewSymbolVisibility, SHN_ABS,
0);
}
std::unique_ptr<Object> BinaryELFBuilder::build() {
initFileHeader();
initHeaderSegment();
SymbolTableSection *SymTab = addSymTab(addStrTab());
initSections();
addData(SymTab);
return std::move(Obj);
}
// Adds sections from IHEX data file. Data should have been
// fully validated by this time.
void IHexELFBuilder::addDataSections() {
OwnedDataSection *Section = nullptr;
uint64_t SegmentAddr = 0, BaseAddr = 0;
uint32_t SecNo = 1;
for (const IHexRecord &R : Records) {
uint64_t RecAddr;
switch (R.Type) {
case IHexRecord::Data:
// Ignore empty data records
if (R.HexData.empty())
continue;
RecAddr = R.Addr + SegmentAddr + BaseAddr;
if (!Section || Section->Addr + Section->Size != RecAddr)
// OriginalOffset field is only used to sort section properly, so
// instead of keeping track of real offset in IHEX file, we use
// section number.
Section = &Obj->addSection<OwnedDataSection>(
".sec" + std::to_string(SecNo++), RecAddr,
ELF::SHF_ALLOC | ELF::SHF_WRITE, SecNo);
Section->appendHexData(R.HexData);
break;
case IHexRecord::EndOfFile:
break;
case IHexRecord::SegmentAddr:
// 20-bit segment address.
SegmentAddr = checkedGetHex<uint16_t>(R.HexData) << 4;
break;
case IHexRecord::StartAddr80x86:
case IHexRecord::StartAddr:
Obj->Entry = checkedGetHex<uint32_t>(R.HexData);
assert(Obj->Entry <= 0xFFFFFU);
break;
case IHexRecord::ExtendedAddr:
// 16-31 bits of linear base address
BaseAddr = checkedGetHex<uint16_t>(R.HexData) << 16;
break;
default:
llvm_unreachable("unknown record type");
}
}
}
std::unique_ptr<Object> IHexELFBuilder::build() {
initFileHeader();
initHeaderSegment();
StringTableSection *StrTab = addStrTab();
addSymTab(StrTab);
initSections();
addDataSections();
return std::move(Obj);
}
template <class ELFT> void ELFBuilder<ELFT>::setParentSegment(Segment &Child) {
for (Segment &Parent : Obj.segments()) {
// Every segment will overlap with itself but we don't want a segment to
// be it's own parent so we avoid that situation.
if (&Child != &Parent && segmentOverlapsSegment(Child, Parent)) {
// We want a canonical "most parental" segment but this requires
// inspecting the ParentSegment.
if (compareSegmentsByOffset(&Parent, &Child))
if (Child.ParentSegment == nullptr ||
compareSegmentsByOffset(&Parent, Child.ParentSegment)) {
Child.ParentSegment = &Parent;
}
}
}
}
template <class ELFT> void ELFBuilder<ELFT>::findEhdrOffset() {
if (!ExtractPartition)
return;
for (const SectionBase &Sec : Obj.sections()) {
if (Sec.Type == SHT_LLVM_PART_EHDR && Sec.Name == *ExtractPartition) {
EhdrOffset = Sec.Offset;
return;
}
}
error("could not find partition named '" + *ExtractPartition + "'");
}
template <class ELFT>
void ELFBuilder<ELFT>::readProgramHeaders(const ELFFile<ELFT> &HeadersFile) {
uint32_t Index = 0;
for (const auto &Phdr : unwrapOrError(HeadersFile.program_headers())) {
if (Phdr.p_offset + Phdr.p_filesz > HeadersFile.getBufSize())
error("program header with offset 0x" + Twine::utohexstr(Phdr.p_offset) +
" and file size 0x" + Twine::utohexstr(Phdr.p_filesz) +
" goes past the end of the file");
ArrayRef<uint8_t> Data{HeadersFile.base() + Phdr.p_offset,
(size_t)Phdr.p_filesz};
Segment &Seg = Obj.addSegment(Data);
Seg.Type = Phdr.p_type;
Seg.Flags = Phdr.p_flags;
Seg.OriginalOffset = Phdr.p_offset + EhdrOffset;
Seg.Offset = Phdr.p_offset + EhdrOffset;
Seg.VAddr = Phdr.p_vaddr;
Seg.PAddr = Phdr.p_paddr;
Seg.FileSize = Phdr.p_filesz;
Seg.MemSize = Phdr.p_memsz;
Seg.Align = Phdr.p_align;
Seg.Index = Index++;
for (SectionBase &Sec : Obj.sections())
if (sectionWithinSegment(Sec, Seg)) {
Seg.addSection(&Sec);
if (!Sec.ParentSegment || Sec.ParentSegment->Offset > Seg.Offset)
Sec.ParentSegment = &Seg;
}
}
auto &ElfHdr = Obj.ElfHdrSegment;
ElfHdr.Index = Index++;
ElfHdr.OriginalOffset = ElfHdr.Offset = EhdrOffset;
const auto &Ehdr = *HeadersFile.getHeader();
auto &PrHdr = Obj.ProgramHdrSegment;
PrHdr.Type = PT_PHDR;
PrHdr.Flags = 0;
// The spec requires us to have p_vaddr % p_align == p_offset % p_align.
// Whereas this works automatically for ElfHdr, here OriginalOffset is
// always non-zero and to ensure the equation we assign the same value to
// VAddr as well.
PrHdr.OriginalOffset = PrHdr.Offset = PrHdr.VAddr = EhdrOffset + Ehdr.e_phoff;
PrHdr.PAddr = 0;
PrHdr.FileSize = PrHdr.MemSize = Ehdr.e_phentsize * Ehdr.e_phnum;
// The spec requires us to naturally align all the fields.
PrHdr.Align = sizeof(Elf_Addr);
PrHdr.Index = Index++;
// Now we do an O(n^2) loop through the segments in order to match up
// segments.
for (Segment &Child : Obj.segments())
setParentSegment(Child);
setParentSegment(ElfHdr);
setParentSegment(PrHdr);
}
template <class ELFT>
void ELFBuilder<ELFT>::initGroupSection(GroupSection *GroupSec) {
if (GroupSec->Align % sizeof(ELF::Elf32_Word) != 0)
error("invalid alignment " + Twine(GroupSec->Align) + " of group section '" +
GroupSec->Name + "'");
SectionTableRef SecTable = Obj.sections();
auto SymTab = SecTable.template getSectionOfType<SymbolTableSection>(
GroupSec->Link,
"link field value '" + Twine(GroupSec->Link) + "' in section '" +
GroupSec->Name + "' is invalid",
"link field value '" + Twine(GroupSec->Link) + "' in section '" +
GroupSec->Name + "' is not a symbol table");
Symbol *Sym = SymTab->getSymbolByIndex(GroupSec->Info);
if (!Sym)
error("info field value '" + Twine(GroupSec->Info) + "' in section '" +
GroupSec->Name + "' is not a valid symbol index");
GroupSec->setSymTab(SymTab);
GroupSec->setSymbol(Sym);
if (GroupSec->Contents.size() % sizeof(ELF::Elf32_Word) ||
GroupSec->Contents.empty())
error("the content of the section " + GroupSec->Name + " is malformed");
const ELF::Elf32_Word *Word =
reinterpret_cast<const ELF::Elf32_Word *>(GroupSec->Contents.data());
const ELF::Elf32_Word *End =
Word + GroupSec->Contents.size() / sizeof(ELF::Elf32_Word);
GroupSec->setFlagWord(*Word++);
for (; Word != End; ++Word) {
uint32_t Index = support::endian::read32<ELFT::TargetEndianness>(Word);
GroupSec->addMember(SecTable.getSection(
Index, "group member index " + Twine(Index) + " in section '" +
GroupSec->Name + "' is invalid"));
}
}
template <class ELFT>
void ELFBuilder<ELFT>::initSymbolTable(SymbolTableSection *SymTab) {
const Elf_Shdr &Shdr = *unwrapOrError(ElfFile.getSection(SymTab->Index));
StringRef StrTabData = unwrapOrError(ElfFile.getStringTableForSymtab(Shdr));
ArrayRef<Elf_Word> ShndxData;
auto Symbols = unwrapOrError(ElfFile.symbols(&Shdr));
for (const auto &Sym : Symbols) {
SectionBase *DefSection = nullptr;
StringRef Name = unwrapOrError(Sym.getName(StrTabData));
if (Sym.st_shndx == SHN_XINDEX) {
if (SymTab->getShndxTable() == nullptr)
error("symbol '" + Name +
"' has index SHN_XINDEX but no SHT_SYMTAB_SHNDX section exists");
if (ShndxData.data() == nullptr) {
const Elf_Shdr &ShndxSec =
*unwrapOrError(ElfFile.getSection(SymTab->getShndxTable()->Index));
ShndxData = unwrapOrError(
ElfFile.template getSectionContentsAsArray<Elf_Word>(&ShndxSec));
if (ShndxData.size() != Symbols.size())
error("symbol section index table does not have the same number of "
"entries as the symbol table");
}
Elf_Word Index = ShndxData[&Sym - Symbols.begin()];
DefSection = Obj.sections().getSection(
Index,
"symbol '" + Name + "' has invalid section index " + Twine(Index));
} else if (Sym.st_shndx >= SHN_LORESERVE) {
if (!isValidReservedSectionIndex(Sym.st_shndx, Obj.Machine)) {
error(
"symbol '" + Name +
"' has unsupported value greater than or equal to SHN_LORESERVE: " +
Twine(Sym.st_shndx));
}
} else if (Sym.st_shndx != SHN_UNDEF) {
DefSection = Obj.sections().getSection(
Sym.st_shndx, "symbol '" + Name +
"' is defined has invalid section index " +
Twine(Sym.st_shndx));
}
SymTab->addSymbol(Name, Sym.getBinding(), Sym.getType(), DefSection,
Sym.getValue(), Sym.st_other, Sym.st_shndx, Sym.st_size);
}
}
template <class ELFT>
static void getAddend(uint64_t &ToSet, const Elf_Rel_Impl<ELFT, false> &Rel) {}
template <class ELFT>
static void getAddend(uint64_t &ToSet, const Elf_Rel_Impl<ELFT, true> &Rela) {
ToSet = Rela.r_addend;
}
template <class T>
static void initRelocations(RelocationSection *Relocs,
SymbolTableSection *SymbolTable, T RelRange) {
for (const auto &Rel : RelRange) {
Relocation ToAdd;
ToAdd.Offset = Rel.r_offset;
getAddend(ToAdd.Addend, Rel);
ToAdd.Type = Rel.getType(false);
if (uint32_t Sym = Rel.getSymbol(false)) {
if (!SymbolTable)
error("'" + Relocs->Name +
"': relocation references symbol with index " + Twine(Sym) +
", but there is no symbol table");
ToAdd.RelocSymbol = SymbolTable->getSymbolByIndex(Sym);
}
Relocs->addRelocation(ToAdd);
}
}
SectionBase *SectionTableRef::getSection(uint32_t Index, Twine ErrMsg) {
if (Index == SHN_UNDEF || Index > Sections.size())
error(ErrMsg);
return Sections[Index - 1].get();
}
template <class T>
T *SectionTableRef::getSectionOfType(uint32_t Index, Twine IndexErrMsg,
Twine TypeErrMsg) {
if (T *Sec = dyn_cast<T>(getSection(Index, IndexErrMsg)))
return Sec;
error(TypeErrMsg);
}
template <class ELFT>
SectionBase &ELFBuilder<ELFT>::makeSection(const Elf_Shdr &Shdr) {
ArrayRef<uint8_t> Data;
switch (Shdr.sh_type) {
case SHT_REL:
case SHT_RELA:
if (Shdr.sh_flags & SHF_ALLOC) {
Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
return Obj.addSection<DynamicRelocationSection>(Data);
}
return Obj.addSection<RelocationSection>();
case SHT_STRTAB:
// If a string table is allocated we don't want to mess with it. That would
// mean altering the memory image. There are no special link types or
// anything so we can just use a Section.
if (Shdr.sh_flags & SHF_ALLOC) {
Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
return Obj.addSection<Section>(Data);
}
return Obj.addSection<StringTableSection>();
case SHT_HASH:
case SHT_GNU_HASH:
// Hash tables should refer to SHT_DYNSYM which we're not going to change.
// Because of this we don't need to mess with the hash tables either.
Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
return Obj.addSection<Section>(Data);
case SHT_GROUP:
Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
return Obj.addSection<GroupSection>(Data);
case SHT_DYNSYM:
Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
return Obj.addSection<DynamicSymbolTableSection>(Data);
case SHT_DYNAMIC:
Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
return Obj.addSection<DynamicSection>(Data);
case SHT_SYMTAB: {
auto &SymTab = Obj.addSection<SymbolTableSection>();
Obj.SymbolTable = &SymTab;
return SymTab;
}
case SHT_SYMTAB_SHNDX: {
auto &ShndxSection = Obj.addSection<SectionIndexSection>();
Obj.SectionIndexTable = &ShndxSection;
return ShndxSection;
}
case SHT_NOBITS:
return Obj.addSection<Section>(Data);
default: {
Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
StringRef Name = unwrapOrError(ElfFile.getSectionName(&Shdr));
if (Name.startswith(".zdebug") || (Shdr.sh_flags & ELF::SHF_COMPRESSED)) {
uint64_t DecompressedSize, DecompressedAlign;
std::tie(DecompressedSize, DecompressedAlign) =
getDecompressedSizeAndAlignment<ELFT>(Data);
return Obj.addSection<CompressedSection>(Data, DecompressedSize,
DecompressedAlign);
}
return Obj.addSection<Section>(Data);
}
}
}
template <class ELFT> void ELFBuilder<ELFT>::readSectionHeaders() {
uint32_t Index = 0;
for (const auto &Shdr : unwrapOrError(ElfFile.sections())) {
if (Index == 0) {
++Index;
continue;
}
auto &Sec = makeSection(Shdr);
Sec.Name = unwrapOrError(ElfFile.getSectionName(&Shdr));
Sec.Type = Shdr.sh_type;
Sec.Flags = Shdr.sh_flags;
Sec.Addr = Shdr.sh_addr;
Sec.Offset = Shdr.sh_offset;
Sec.OriginalOffset = Shdr.sh_offset;
Sec.Size = Shdr.sh_size;
Sec.Link = Shdr.sh_link;
Sec.Info = Shdr.sh_info;
Sec.Align = Shdr.sh_addralign;
Sec.EntrySize = Shdr.sh_entsize;
Sec.Index = Index++;
Sec.OriginalData =
ArrayRef<uint8_t>(ElfFile.base() + Shdr.sh_offset,
(Shdr.sh_type == SHT_NOBITS) ? 0 : Shdr.sh_size);
}
}
template <class ELFT> void ELFBuilder<ELFT>::readSections(bool EnsureSymtab) {
// If a section index table exists we'll need to initialize it before we
// initialize the symbol table because the symbol table might need to
// reference it.
if (Obj.SectionIndexTable)
Obj.SectionIndexTable->initialize(Obj.sections());
// Now that all of the sections have been added we can fill out some extra
// details about symbol tables. We need the symbol table filled out before
// any relocations.
if (Obj.SymbolTable) {
Obj.SymbolTable->initialize(Obj.sections());
initSymbolTable(Obj.SymbolTable);
} else if (EnsureSymtab) {
// Reuse the existing SHT_STRTAB section if exists.
StringTableSection *StrTab = nullptr;
for (auto &Sec : Obj.sections()) {
if (Sec.Type == ELF::SHT_STRTAB && !(Sec.Flags & SHF_ALLOC)) {
StrTab = static_cast<StringTableSection *>(&Sec);
// Prefer .strtab to .shstrtab.
if (Obj.SectionNames != &Sec)
break;
}
}
if (!StrTab)
StrTab = &Obj.addSection<StringTableSection>();
SymbolTableSection &SymTab = Obj.addSection<SymbolTableSection>();
SymTab.Name = ".symtab";
SymTab.Link = StrTab->Index;
SymTab.initialize(Obj.sections());
SymTab.addSymbol("", 0, 0, nullptr, 0, 0, 0, 0);
Obj.SymbolTable = &SymTab;
}
// Now that all sections and symbols have been added we can add
// relocations that reference symbols and set the link and info fields for
// relocation sections.
for (auto &Sec : Obj.sections()) {
if (&Sec == Obj.SymbolTable)
continue;
Sec.initialize(Obj.sections());
if (auto RelSec = dyn_cast<RelocationSection>(&Sec)) {
auto Shdr = unwrapOrError(ElfFile.sections()).begin() + RelSec->Index;
if (RelSec->Type == SHT_REL)
initRelocations(RelSec, Obj.SymbolTable,
unwrapOrError(ElfFile.rels(Shdr)));
else
initRelocations(RelSec, Obj.SymbolTable,
unwrapOrError(ElfFile.relas(Shdr)));
} else if (auto GroupSec = dyn_cast<GroupSection>(&Sec)) {
initGroupSection(GroupSec);
}
}
uint32_t ShstrIndex = ElfFile.getHeader()->e_shstrndx;
if (ShstrIndex == SHN_XINDEX)
ShstrIndex = unwrapOrError(ElfFile.getSection(0))->sh_link;
if (ShstrIndex == SHN_UNDEF)
Obj.HadShdrs = false;
else
Obj.SectionNames =
Obj.sections().template getSectionOfType<StringTableSection>(
ShstrIndex,
"e_shstrndx field value " + Twine(ShstrIndex) + " in elf header " +
" is invalid",
"e_shstrndx field value " + Twine(ShstrIndex) + " in elf header " +
" is not a string table");
}
template <class ELFT> void ELFBuilder<ELFT>::build(bool EnsureSymtab) {
readSectionHeaders();
findEhdrOffset();
// The ELFFile whose ELF headers and program headers are copied into the
// output file. Normally the same as ElfFile, but if we're extracting a
// loadable partition it will point to the partition's headers.
ELFFile<ELFT> HeadersFile = unwrapOrError(ELFFile<ELFT>::create(toStringRef(
{ElfFile.base() + EhdrOffset, ElfFile.getBufSize() - EhdrOffset})));
auto &Ehdr = *HeadersFile.getHeader();
Obj.OSABI = Ehdr.e_ident[EI_OSABI];
Obj.ABIVersion = Ehdr.e_ident[EI_ABIVERSION];
Obj.Type = Ehdr.e_type;
Obj.Machine = Ehdr.e_machine;
Obj.Version = Ehdr.e_version;
Obj.Entry = Ehdr.e_entry;
Obj.Flags = Ehdr.e_flags;
readSections(EnsureSymtab);
readProgramHeaders(HeadersFile);
}
Writer::~Writer() {}
Reader::~Reader() {}
std::unique_ptr<Object> BinaryReader::create(bool /*EnsureSymtab*/) const {
return BinaryELFBuilder(MemBuf, NewSymbolVisibility).build();
}
Expected<std::vector<IHexRecord>> IHexReader::parse() const {
SmallVector<StringRef, 16> Lines;
std::vector<IHexRecord> Records;
bool HasSections = false;
MemBuf->getBuffer().split(Lines, '\n');
Records.reserve(Lines.size());
for (size_t LineNo = 1; LineNo <= Lines.size(); ++LineNo) {
StringRef Line = Lines[LineNo - 1].trim();
if (Line.empty())
continue;
Expected<IHexRecord> R = IHexRecord::parse(Line);
if (!R)
return parseError(LineNo, R.takeError());
if (R->Type == IHexRecord::EndOfFile)
break;
HasSections |= (R->Type == IHexRecord::Data);
Records.push_back(*R);
}
if (!HasSections)
return parseError(-1U, "no sections");
return std::move(Records);
}
std::unique_ptr<Object> IHexReader::create(bool /*EnsureSymtab*/) const {
std::vector<IHexRecord> Records = unwrapOrError(parse());
return IHexELFBuilder(Records).build();
}
std::unique_ptr<Object> ELFReader::create(bool EnsureSymtab) const {
auto Obj = std::make_unique<Object>();
if (auto *O = dyn_cast<ELFObjectFile<ELF32LE>>(Bin)) {
ELFBuilder<ELF32LE> Builder(*O, *Obj, ExtractPartition);
Builder.build(EnsureSymtab);
return Obj;
} else if (auto *O = dyn_cast<ELFObjectFile<ELF64LE>>(Bin)) {
ELFBuilder<ELF64LE> Builder(*O, *Obj, ExtractPartition);
Builder.build(EnsureSymtab);
return Obj;
} else if (auto *O = dyn_cast<ELFObjectFile<ELF32BE>>(Bin)) {
ELFBuilder<ELF32BE> Builder(*O, *Obj, ExtractPartition);
Builder.build(EnsureSymtab);
return Obj;
} else if (auto *O = dyn_cast<ELFObjectFile<ELF64BE>>(Bin)) {
ELFBuilder<ELF64BE> Builder(*O, *Obj, ExtractPartition);
Builder.build(EnsureSymtab);
return Obj;
}
error("invalid file type");
}
template <class ELFT> void ELFWriter<ELFT>::writeEhdr() {
Elf_Ehdr &Ehdr = *reinterpret_cast<Elf_Ehdr *>(Buf.getBufferStart());
std::fill(Ehdr.e_ident, Ehdr.e_ident + 16, 0);
Ehdr.e_ident[EI_MAG0] = 0x7f;
Ehdr.e_ident[EI_MAG1] = 'E';
Ehdr.e_ident[EI_MAG2] = 'L';
Ehdr.e_ident[EI_MAG3] = 'F';
Ehdr.e_ident[EI_CLASS] = ELFT::Is64Bits ? ELFCLASS64 : ELFCLASS32;
Ehdr.e_ident[EI_DATA] =
ELFT::TargetEndianness == support::big ? ELFDATA2MSB : ELFDATA2LSB;
Ehdr.e_ident[EI_VERSION] = EV_CURRENT;
Ehdr.e_ident[EI_OSABI] = Obj.OSABI;
Ehdr.e_ident[EI_ABIVERSION] = Obj.ABIVersion;
Ehdr.e_type = Obj.Type;
Ehdr.e_machine = Obj.Machine;
Ehdr.e_version = Obj.Version;
Ehdr.e_entry = Obj.Entry;
// We have to use the fully-qualified name llvm::size
// since some compilers complain on ambiguous resolution.
Ehdr.e_phnum = llvm::size(Obj.segments());
Ehdr.e_phoff = (Ehdr.e_phnum != 0) ? Obj.ProgramHdrSegment.Offset : 0;
Ehdr.e_phentsize = (Ehdr.e_phnum != 0) ? sizeof(Elf_Phdr) : 0;
Ehdr.e_flags = Obj.Flags;
Ehdr.e_ehsize = sizeof(Elf_Ehdr);
if (WriteSectionHeaders && Obj.sections().size() != 0) {
Ehdr.e_shentsize = sizeof(Elf_Shdr);
Ehdr.e_shoff = Obj.SHOff;
// """
// If the number of sections is greater than or equal to
// SHN_LORESERVE (0xff00), this member has the value zero and the actual
// number of section header table entries is contained in the sh_size field
// of the section header at index 0.
// """
auto Shnum = Obj.sections().size() + 1;
if (Shnum >= SHN_LORESERVE)
Ehdr.e_shnum = 0;
else
Ehdr.e_shnum = Shnum;
// """
// If the section name string table section index is greater than or equal
// to SHN_LORESERVE (0xff00), this member has the value SHN_XINDEX (0xffff)
// and the actual index of the section name string table section is
// contained in the sh_link field of the section header at index 0.
// """
if (Obj.SectionNames->Index >= SHN_LORESERVE)
Ehdr.e_shstrndx = SHN_XINDEX;
else
Ehdr.e_shstrndx = Obj.SectionNames->Index;
} else {
Ehdr.e_shentsize = 0;
Ehdr.e_shoff = 0;
Ehdr.e_shnum = 0;
Ehdr.e_shstrndx = 0;
}
}
template <class ELFT> void ELFWriter<ELFT>::writePhdrs() {
for (auto &Seg : Obj.segments())
writePhdr(Seg);
}
template <class ELFT> void ELFWriter<ELFT>::writeShdrs() {
// This reference serves to write the dummy section header at the begining
// of the file. It is not used for anything else
Elf_Shdr &Shdr =
*reinterpret_cast<Elf_Shdr *>(Buf.getBufferStart() + Obj.SHOff);
Shdr.sh_name = 0;
Shdr.sh_type = SHT_NULL;
Shdr.sh_flags = 0;
Shdr.sh_addr = 0;
Shdr.sh_offset = 0;
// See writeEhdr for why we do this.
uint64_t Shnum = Obj.sections().size() + 1;
if (Shnum >= SHN_LORESERVE)
Shdr.sh_size = Shnum;
else
Shdr.sh_size = 0;
// See writeEhdr for why we do this.
if (Obj.SectionNames != nullptr && Obj.SectionNames->Index >= SHN_LORESERVE)
Shdr.sh_link = Obj.SectionNames->Index;
else
Shdr.sh_link = 0;
Shdr.sh_info = 0;
Shdr.sh_addralign = 0;
Shdr.sh_entsize = 0;
for (SectionBase &Sec : Obj.sections())
writeShdr(Sec);
}
template <class ELFT> void ELFWriter<ELFT>::writeSectionData() {
for (SectionBase &Sec : Obj.sections())
// Segments are responsible for writing their contents, so only write the
// section data if the section is not in a segment. Note that this renders
// sections in segments effectively immutable.
if (Sec.ParentSegment == nullptr)
Sec.accept(*SecWriter);
}
template <class ELFT> void ELFWriter<ELFT>::writeSegmentData() {
for (Segment &Seg : Obj.segments()) {
uint8_t *B = Buf.getBufferStart() + Seg.Offset;
assert(Seg.FileSize == Seg.getContents().size() &&
"Segment size must match contents size");
std::memcpy(B, Seg.getContents().data(), Seg.FileSize);
}
// Iterate over removed sections and overwrite their old data with zeroes.
for (auto &Sec : Obj.removedSections()) {
Segment *Parent = Sec.ParentSegment;
if (Parent == nullptr || Sec.Type == SHT_NOBITS || Sec.Size == 0)
continue;
uint64_t Offset =
Sec.OriginalOffset - Parent->OriginalOffset + Parent->Offset;
std::memset(Buf.getBufferStart() + Offset, 0, Sec.Size);
}
}
template <class ELFT>
ELFWriter<ELFT>::ELFWriter(Object &Obj, Buffer &Buf, bool WSH)
: Writer(Obj, Buf), WriteSectionHeaders(WSH && Obj.HadShdrs) {}
Error Object::removeSections(bool AllowBrokenLinks,
std::function<bool(const SectionBase &)> ToRemove) {
auto Iter = std::stable_partition(
std::begin(Sections), std::end(Sections), [=](const SecPtr &Sec) {
if (ToRemove(*Sec))
return false;
if (auto RelSec = dyn_cast<RelocationSectionBase>(Sec.get())) {
if (auto ToRelSec = RelSec->getSection())
return !ToRemove(*ToRelSec);
}
return true;
});
if (SymbolTable != nullptr && ToRemove(*SymbolTable))
SymbolTable = nullptr;
if (SectionNames != nullptr && ToRemove(*SectionNames))
SectionNames = nullptr;
if (SectionIndexTable != nullptr && ToRemove(*SectionIndexTable))
SectionIndexTable = nullptr;
// Now make sure there are no remaining references to the sections that will
// be removed. Sometimes it is impossible to remove a reference so we emit
// an error here instead.
std::unordered_set<const SectionBase *> RemoveSections;
RemoveSections.reserve(std::distance(Iter, std::end(Sections)));
for (auto &RemoveSec : make_range(Iter, std::end(Sections))) {
for (auto &Segment : Segments)
Segment->removeSection(RemoveSec.get());
RemoveSections.insert(RemoveSec.get());
}
// For each section that remains alive, we want to remove the dead references.
// This either might update the content of the section (e.g. remove symbols
// from symbol table that belongs to removed section) or trigger an error if
// a live section critically depends on a section being removed somehow
// (e.g. the removed section is referenced by a relocation).
for (auto &KeepSec : make_range(std::begin(Sections), Iter)) {
if (Error E = KeepSec->removeSectionReferences(AllowBrokenLinks,
[&RemoveSections](const SectionBase *Sec) {
return RemoveSections.find(Sec) != RemoveSections.end();
}))
return E;
}
// Transfer removed sections into the Object RemovedSections container for use
// later.
std::move(Iter, Sections.end(), std::back_inserter(RemovedSections));
// Now finally get rid of them all together.
Sections.erase(Iter, std::end(Sections));
return Error::success();
}
Error Object::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {
if (SymbolTable)
for (const SecPtr &Sec : Sections)
if (Error E = Sec->removeSymbols(ToRemove))
return E;
return Error::success();
}
void Object::sortSections() {
// Use stable_sort to maintain the original ordering as closely as possible.
llvm::stable_sort(Sections, [](const SecPtr &A, const SecPtr &B) {
// Put SHT_GROUP sections first, since group section headers must come
// before the sections they contain. This also matches what GNU objcopy
// does.
if (A->Type != B->Type &&
(A->Type == ELF::SHT_GROUP || B->Type == ELF::SHT_GROUP))
return A->Type == ELF::SHT_GROUP;
// For all other sections, sort by offset order.
return A->OriginalOffset < B->OriginalOffset;
});
}
// Orders segments such that if x = y->ParentSegment then y comes before x.
static void orderSegments(std::vector<Segment *> &Segments) {
llvm::stable_sort(Segments, compareSegmentsByOffset);
}
// This function finds a consistent layout for a list of segments starting from
// an Offset. It assumes that Segments have been sorted by orderSegments and
// returns an Offset one past the end of the last segment.
static uint64_t layoutSegments(std::vector<Segment *> &Segments,
uint64_t Offset) {
assert(std::is_sorted(std::begin(Segments), std::end(Segments),
compareSegmentsByOffset));
// The only way a segment should move is if a section was between two
// segments and that section was removed. If that section isn't in a segment
// then it's acceptable, but not ideal, to simply move it to after the
// segments. So we can simply layout segments one after the other accounting
// for alignment.
for (Segment *Seg : Segments) {
// We assume that segments have been ordered by OriginalOffset and Index
// such that a parent segment will always come before a child segment in
// OrderedSegments. This means that the Offset of the ParentSegment should
// already be set and we can set our offset relative to it.
if (Seg->ParentSegment != nullptr) {
Segment *Parent = Seg->ParentSegment;
Seg->Offset =
Parent->Offset + Seg->OriginalOffset - Parent->OriginalOffset;
} else {
Seg->Offset =
alignTo(Offset, std::max<uint64_t>(Seg->Align, 1), Seg->VAddr);
}
Offset = std::max(Offset, Seg->Offset + Seg->FileSize);
}
return Offset;
}
// This function finds a consistent layout for a list of sections. It assumes
// that the ->ParentSegment of each section has already been laid out. The
// supplied starting Offset is used for the starting offset of any section that
// does not have a ParentSegment. It returns either the offset given if all
// sections had a ParentSegment or an offset one past the last section if there
// was a section that didn't have a ParentSegment.
template <class Range>
static uint64_t layoutSections(Range Sections, uint64_t Offset) {
// Now the offset of every segment has been set we can assign the offsets
// of each section. For sections that are covered by a segment we should use
// the segment's original offset and the section's original offset to compute
// the offset from the start of the segment. Using the offset from the start
// of the segment we can assign a new offset to the section. For sections not
// covered by segments we can just bump Offset to the next valid location.
uint32_t Index = 1;
for (auto &Sec : Sections) {
Sec.Index = Index++;
if (Sec.ParentSegment != nullptr) {
auto Segment = *Sec.ParentSegment;
Sec.Offset =
Segment.Offset + (Sec.OriginalOffset - Segment.OriginalOffset);
} else {
Offset = alignTo(Offset, Sec.Align == 0 ? 1 : Sec.Align);
Sec.Offset = Offset;
if (Sec.Type != SHT_NOBITS)
Offset += Sec.Size;
}
}
return Offset;
}
template <class ELFT> void ELFWriter<ELFT>::initEhdrSegment() {
Segment &ElfHdr = Obj.ElfHdrSegment;
ElfHdr.Type = PT_PHDR;
ElfHdr.Flags = 0;
ElfHdr.VAddr = 0;
ElfHdr.PAddr = 0;
ElfHdr.FileSize = ElfHdr.MemSize = sizeof(Elf_Ehdr);
ElfHdr.Align = 0;
}
template <class ELFT> void ELFWriter<ELFT>::assignOffsets() {
// We need a temporary list of segments that has a special order to it
// so that we know that anytime ->ParentSegment is set that segment has
// already had its offset properly set.
std::vector<Segment *> OrderedSegments;
for (Segment &Segment : Obj.segments())
OrderedSegments.push_back(&Segment);
OrderedSegments.push_back(&Obj.ElfHdrSegment);
OrderedSegments.push_back(&Obj.ProgramHdrSegment);
orderSegments(OrderedSegments);
// Offset is used as the start offset of the first segment to be laid out.
// Since the ELF Header (ElfHdrSegment) must be at the start of the file,
// we start at offset 0.
uint64_t Offset = 0;
Offset = layoutSegments(OrderedSegments, Offset);
Offset = layoutSections(Obj.sections(), Offset);
// If we need to write the section header table out then we need to align the
// Offset so that SHOffset is valid.
if (WriteSectionHeaders)
Offset = alignTo(Offset, sizeof(Elf_Addr));
Obj.SHOff = Offset;
}
template <class ELFT> size_t ELFWriter<ELFT>::totalSize() const {
// We already have the section header offset so we can calculate the total
// size by just adding up the size of each section header.
if (!WriteSectionHeaders)
return Obj.SHOff;
size_t ShdrCount = Obj.sections().size() + 1; // Includes null shdr.
return Obj.SHOff + ShdrCount * sizeof(Elf_Shdr);
}
template <class ELFT> Error ELFWriter<ELFT>::write() {
// Segment data must be written first, so that the ELF header and program
// header tables can overwrite it, if covered by a segment.
writeSegmentData();
writeEhdr();
writePhdrs();
writeSectionData();
if (WriteSectionHeaders)
writeShdrs();
return Buf.commit();
}
static Error removeUnneededSections(Object &Obj) {
// We can remove an empty symbol table from non-relocatable objects.
// Relocatable objects typically have relocation sections whose
// sh_link field points to .symtab, so we can't remove .symtab
// even if it is empty.
if (Obj.isRelocatable() || Obj.SymbolTable == nullptr ||
!Obj.SymbolTable->empty())
return Error::success();
// .strtab can be used for section names. In such a case we shouldn't
// remove it.
auto *StrTab = Obj.SymbolTable->getStrTab() == Obj.SectionNames
? nullptr
: Obj.SymbolTable->getStrTab();
return Obj.removeSections(false, [&](const SectionBase &Sec) {
return &Sec == Obj.SymbolTable || &Sec == StrTab;
});
}
template <class ELFT> Error ELFWriter<ELFT>::finalize() {
// It could happen that SectionNames has been removed and yet the user wants
// a section header table output. We need to throw an error if a user tries
// to do that.
if (Obj.SectionNames == nullptr && WriteSectionHeaders)
return createStringError(llvm::errc::invalid_argument,
"cannot write section header table because "
"section header string table was removed");
if (Error E = removeUnneededSections(Obj))
return E;
Obj.sortSections();
// We need to assign indexes before we perform layout because we need to know
// if we need large indexes or not. We can assign indexes first and check as
// we go to see if we will actully need large indexes.
bool NeedsLargeIndexes = false;
if (Obj.sections().size() >= SHN_LORESERVE) {
SectionTableRef Sections = Obj.sections();
NeedsLargeIndexes =
std::any_of(Sections.begin() + SHN_LORESERVE, Sections.end(),
[](const SectionBase &Sec) { return Sec.HasSymbol; });
// TODO: handle case where only one section needs the large index table but
// only needs it because the large index table hasn't been removed yet.
}
if (NeedsLargeIndexes) {
// This means we definitely need to have a section index table but if we
// already have one then we should use it instead of making a new one.
if (Obj.SymbolTable != nullptr && Obj.SectionIndexTable == nullptr) {
// Addition of a section to the end does not invalidate the indexes of
// other sections and assigns the correct index to the new section.
auto &Shndx = Obj.addSection<SectionIndexSection>();
Obj.SymbolTable->setShndxTable(&Shndx);
Shndx.setSymTab(Obj.SymbolTable);
}
} else {
// Since we don't need SectionIndexTable we should remove it and all
// references to it.
if (Obj.SectionIndexTable != nullptr) {
// We do not support sections referring to the section index table.
if (Error E = Obj.removeSections(false /*AllowBrokenLinks*/,
[this](const SectionBase &Sec) {
return &Sec == Obj.SectionIndexTable;
}))
return E;
}
}
// Make sure we add the names of all the sections. Importantly this must be
// done after we decide to add or remove SectionIndexes.
if (Obj.SectionNames != nullptr)
for (const SectionBase &Sec : Obj.sections())
Obj.SectionNames->addString(Sec.Name);
initEhdrSegment();
// Before we can prepare for layout the indexes need to be finalized.
// Also, the output arch may not be the same as the input arch, so fix up
// size-related fields before doing layout calculations.
uint64_t Index = 0;
auto SecSizer = std::make_unique<ELFSectionSizer<ELFT>>();
for (SectionBase &Sec : Obj.sections()) {
Sec.Index = Index++;
Sec.accept(*SecSizer);
}
// The symbol table does not update all other sections on update. For
// instance, symbol names are not added as new symbols are added. This means
// that some sections, like .strtab, don't yet have their final size.
if (Obj.SymbolTable != nullptr)
Obj.SymbolTable->prepareForLayout();
// Now that all strings are added we want to finalize string table builders,
// because that affects section sizes which in turn affects section offsets.
for (SectionBase &Sec : Obj.sections())
if (auto StrTab = dyn_cast<StringTableSection>(&Sec))
StrTab->prepareForLayout();
assignOffsets();
// layoutSections could have modified section indexes, so we need
// to fill the index table after assignOffsets.
if (Obj.SymbolTable != nullptr)
Obj.SymbolTable->fillShndxTable();
// Finally now that all offsets and indexes have been set we can finalize any
// remaining issues.
uint64_t Offset = Obj.SHOff + sizeof(Elf_Shdr);
for (SectionBase &Sec : Obj.sections()) {
Sec.HeaderOffset = Offset;
Offset += sizeof(Elf_Shdr);
if (WriteSectionHeaders)
Sec.NameIndex = Obj.SectionNames->findIndex(Sec.Name);
Sec.finalize();
}
if (Error E = Buf.allocate(totalSize()))
return E;
SecWriter = std::make_unique<ELFSectionWriter<ELFT>>(Buf);
return Error::success();
}
Error BinaryWriter::write() {
for (const SectionBase &Sec : Obj.allocSections())
Sec.accept(*SecWriter);
return Buf.commit();
}
Error BinaryWriter::finalize() {
// We need a temporary list of segments that has a special order to it
// so that we know that anytime ->ParentSegment is set that segment has
// already had it's offset properly set. We only want to consider the segments
// that will affect layout of allocated sections so we only add those.
std::vector<Segment *> OrderedSegments;
for (const SectionBase &Sec : Obj.allocSections())
if (Sec.ParentSegment != nullptr)
OrderedSegments.push_back(Sec.ParentSegment);
// For binary output, we're going to use physical addresses instead of
// virtual addresses, since a binary output is used for cases like ROM
// loading and physical addresses are intended for ROM loading.
// However, if no segment has a physical address, we'll fallback to using
// virtual addresses for all.
if (all_of(OrderedSegments,
[](const Segment *Seg) { return Seg->PAddr == 0; }))
for (Segment *Seg : OrderedSegments)
Seg->PAddr = Seg->VAddr;
llvm::stable_sort(OrderedSegments, compareSegmentsByPAddr);
// Because we add a ParentSegment for each section we might have duplicate
// segments in OrderedSegments. If there were duplicates then layoutSegments
// would do very strange things.
auto End =
std::unique(std::begin(OrderedSegments), std::end(OrderedSegments));
OrderedSegments.erase(End, std::end(OrderedSegments));
uint64_t Offset = 0;
// Modify the first segment so that there is no gap at the start. This allows
// our layout algorithm to proceed as expected while not writing out the gap
// at the start.
if (!OrderedSegments.empty()) {
Segment *Seg = OrderedSegments[0];
const SectionBase *Sec = Seg->firstSection();
auto Diff = Sec->OriginalOffset - Seg->OriginalOffset;
Seg->OriginalOffset += Diff;
// The size needs to be shrunk as well.
Seg->FileSize -= Diff;
// The PAddr needs to be increased to remove the gap before the first
// section.
Seg->PAddr += Diff;
uint64_t LowestPAddr = Seg->PAddr;
for (Segment *Segment : OrderedSegments) {
Segment->Offset = Segment->PAddr - LowestPAddr;
Offset = std::max(Offset, Segment->Offset + Segment->FileSize);
}
}
layoutSections(Obj.allocSections(), Offset);
// Now that every section has been laid out we just need to compute the total
// file size. This might not be the same as the offset returned by
// layoutSections, because we want to truncate the last segment to the end of
// its last section, to match GNU objcopy's behaviour.
TotalSize = 0;
for (const SectionBase &Sec : Obj.allocSections())
if (Sec.Type != SHT_NOBITS)
TotalSize = std::max(TotalSize, Sec.Offset + Sec.Size);
if (Error E = Buf.allocate(TotalSize))
return E;
SecWriter = std::make_unique<BinarySectionWriter>(Buf);
return Error::success();
}
bool IHexWriter::SectionCompare::operator()(const SectionBase *Lhs,
const SectionBase *Rhs) const {
return (sectionPhysicalAddr(Lhs) & 0xFFFFFFFFU) <
(sectionPhysicalAddr(Rhs) & 0xFFFFFFFFU);
}
uint64_t IHexWriter::writeEntryPointRecord(uint8_t *Buf) {
IHexLineData HexData;
uint8_t Data[4] = {};
// We don't write entry point record if entry is zero.
if (Obj.Entry == 0)
return 0;
if (Obj.Entry <= 0xFFFFFU) {
Data[0] = ((Obj.Entry & 0xF0000U) >> 12) & 0xFF;
support::endian::write(&Data[2], static_cast<uint16_t>(Obj.Entry),
support::big);
HexData = IHexRecord::getLine(IHexRecord::StartAddr80x86, 0, Data);
} else {
support::endian::write(Data, static_cast<uint32_t>(Obj.Entry),
support::big);
HexData = IHexRecord::getLine(IHexRecord::StartAddr, 0, Data);
}
memcpy(Buf, HexData.data(), HexData.size());
return HexData.size();
}
uint64_t IHexWriter::writeEndOfFileRecord(uint8_t *Buf) {
IHexLineData HexData = IHexRecord::getLine(IHexRecord::EndOfFile, 0, {});
memcpy(Buf, HexData.data(), HexData.size());
return HexData.size();
}
Error IHexWriter::write() {
IHexSectionWriter Writer(Buf);
// Write sections.
for (const SectionBase *Sec : Sections)
Sec->accept(Writer);
uint64_t Offset = Writer.getBufferOffset();
// Write entry point address.
Offset += writeEntryPointRecord(Buf.getBufferStart() + Offset);
// Write EOF.
Offset += writeEndOfFileRecord(Buf.getBufferStart() + Offset);
assert(Offset == TotalSize);
return Buf.commit();
}
Error IHexWriter::checkSection(const SectionBase &Sec) {
uint64_t Addr = sectionPhysicalAddr(&Sec);
if (addressOverflows32bit(Addr) || addressOverflows32bit(Addr + Sec.Size - 1))
return createStringError(
errc::invalid_argument,
"Section '%s' address range [0x%llx, 0x%llx] is not 32 bit", Sec.Name.c_str(),
Addr, Addr + Sec.Size - 1);
return Error::success();
}
Error IHexWriter::finalize() {
bool UseSegments = false;
auto ShouldWrite = [](const SectionBase &Sec) {
return (Sec.Flags & ELF::SHF_ALLOC) && (Sec.Type != ELF::SHT_NOBITS);
};
auto IsInPtLoad = [](const SectionBase &Sec) {
return Sec.ParentSegment && Sec.ParentSegment->Type == ELF::PT_LOAD;
};
// We can't write 64-bit addresses.
if (addressOverflows32bit(Obj.Entry))
return createStringError(errc::invalid_argument,
"Entry point address 0x%llx overflows 32 bits.",
Obj.Entry);
// If any section we're to write has segment then we
// switch to using physical addresses. Otherwise we
// use section virtual address.
for (const SectionBase &Sec : Obj.sections())
if (ShouldWrite(Sec) && IsInPtLoad(Sec)) {
UseSegments = true;
break;
}
for (const SectionBase &Sec : Obj.sections())
if (ShouldWrite(Sec) && (!UseSegments || IsInPtLoad(Sec))) {
if (Error E = checkSection(Sec))
return E;
Sections.insert(&Sec);
}
IHexSectionWriterBase LengthCalc(Buf);
for (const SectionBase *Sec : Sections)
Sec->accept(LengthCalc);
// We need space to write section records + StartAddress record
// (if start adress is not zero) + EndOfFile record.
TotalSize = LengthCalc.getBufferOffset() +
(Obj.Entry ? IHexRecord::getLineLength(4) : 0) +
IHexRecord::getLineLength(0);
if (Error E = Buf.allocate(TotalSize))
return E;
return Error::success();
}
template class ELFBuilder<ELF64LE>;
template class ELFBuilder<ELF64BE>;
template class ELFBuilder<ELF32LE>;
template class ELFBuilder<ELF32BE>;
template class ELFWriter<ELF64LE>;
template class ELFWriter<ELF64BE>;
template class ELFWriter<ELF32LE>;
template class ELFWriter<ELF32BE>;
} // end namespace elf
} // end namespace objcopy
} // end namespace llvm
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