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ELFEmitter.cpp
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ELFEmitter.cpp
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//===- yaml2elf - Convert YAML to a ELF object file -----------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
///
/// \file
/// The ELF component of yaml2obj.
///
//===----------------------------------------------------------------------===//
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/ObjectYAML/ELFYAML.h"
#include "llvm/ObjectYAML/yaml2obj.h"
#include "llvm/Support/EndianStream.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/WithColor.h"
#include "llvm/Support/YAMLTraits.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
// This class is used to build up a contiguous binary blob while keeping
// track of an offset in the output (which notionally begins at
// `InitialOffset`).
namespace {
class ContiguousBlobAccumulator {
const uint64_t InitialOffset;
SmallVector<char, 128> Buf;
raw_svector_ostream OS;
public:
ContiguousBlobAccumulator(uint64_t InitialOffset_)
: InitialOffset(InitialOffset_), Buf(), OS(Buf) {}
template <class Integer>
raw_ostream &getOSAndAlignedOffset(Integer &Offset, unsigned Align) {
Offset = padToAlignment(Align);
return OS;
}
/// \returns The new offset.
uint64_t padToAlignment(unsigned Align) {
if (Align == 0)
Align = 1;
uint64_t CurrentOffset = InitialOffset + OS.tell();
uint64_t AlignedOffset = alignTo(CurrentOffset, Align);
OS.write_zeros(AlignedOffset - CurrentOffset);
return AlignedOffset; // == CurrentOffset;
}
void writeBlobToStream(raw_ostream &Out) { Out << OS.str(); }
};
// Used to keep track of section and symbol names, so that in the YAML file
// sections and symbols can be referenced by name instead of by index.
class NameToIdxMap {
StringMap<unsigned> Map;
public:
/// \Returns false if name is already present in the map.
bool addName(StringRef Name, unsigned Ndx) {
return Map.insert({Name, Ndx}).second;
}
/// \Returns false if name is not present in the map.
bool lookup(StringRef Name, unsigned &Idx) const {
auto I = Map.find(Name);
if (I == Map.end())
return false;
Idx = I->getValue();
return true;
}
/// Asserts if name is not present in the map.
unsigned get(StringRef Name) const {
unsigned Idx;
if (lookup(Name, Idx))
return Idx;
assert(false && "Expected section not found in index");
return 0;
}
unsigned size() const { return Map.size(); }
};
namespace {
struct Fragment {
uint64_t Offset;
uint64_t Size;
uint32_t Type;
uint64_t AddrAlign;
};
} // namespace
/// "Single point of truth" for the ELF file construction.
/// TODO: This class still has a ways to go before it is truly a "single
/// point of truth".
template <class ELFT> class ELFState {
typedef typename ELFT::Ehdr Elf_Ehdr;
typedef typename ELFT::Phdr Elf_Phdr;
typedef typename ELFT::Shdr Elf_Shdr;
typedef typename ELFT::Sym Elf_Sym;
typedef typename ELFT::Rel Elf_Rel;
typedef typename ELFT::Rela Elf_Rela;
typedef typename ELFT::Relr Elf_Relr;
typedef typename ELFT::Dyn Elf_Dyn;
typedef typename ELFT::uint uintX_t;
enum class SymtabType { Static, Dynamic };
/// The future ".strtab" section.
StringTableBuilder DotStrtab{StringTableBuilder::ELF};
/// The future ".shstrtab" section.
StringTableBuilder DotShStrtab{StringTableBuilder::ELF};
/// The future ".dynstr" section.
StringTableBuilder DotDynstr{StringTableBuilder::ELF};
NameToIdxMap SN2I;
NameToIdxMap SymN2I;
NameToIdxMap DynSymN2I;
ELFYAML::Object &Doc;
uint64_t LocationCounter = 0;
bool HasError = false;
yaml::ErrorHandler ErrHandler;
void reportError(const Twine &Msg);
std::vector<Elf_Sym> toELFSymbols(ArrayRef<ELFYAML::Symbol> Symbols,
const StringTableBuilder &Strtab);
unsigned toSectionIndex(StringRef S, StringRef LocSec, StringRef LocSym = "");
unsigned toSymbolIndex(StringRef S, StringRef LocSec, bool IsDynamic);
void buildSectionIndex();
void buildSymbolIndexes();
void initProgramHeaders(std::vector<Elf_Phdr> &PHeaders);
bool initImplicitHeader(ContiguousBlobAccumulator &CBA, Elf_Shdr &Header,
StringRef SecName, ELFYAML::Section *YAMLSec);
void initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
ContiguousBlobAccumulator &CBA);
void initSymtabSectionHeader(Elf_Shdr &SHeader, SymtabType STType,
ContiguousBlobAccumulator &CBA,
ELFYAML::Section *YAMLSec);
void initStrtabSectionHeader(Elf_Shdr &SHeader, StringRef Name,
StringTableBuilder &STB,
ContiguousBlobAccumulator &CBA,
ELFYAML::Section *YAMLSec);
void setProgramHeaderLayout(std::vector<Elf_Phdr> &PHeaders,
std::vector<Elf_Shdr> &SHeaders);
std::vector<Fragment>
getPhdrFragments(const ELFYAML::ProgramHeader &Phdr,
ArrayRef<typename ELFT::Shdr> SHeaders);
void finalizeStrings();
void writeELFHeader(ContiguousBlobAccumulator &CBA, raw_ostream &OS);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::RawContentSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::RelocationSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::RelrSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader, const ELFYAML::Group &Group,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::SymtabShndxSection &Shndx,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::SymverSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::VerneedSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::VerdefSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::MipsABIFlags &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::DynamicSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::StackSizesSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::HashSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::AddrsigSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::NoteSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::GnuHashSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::LinkerOptionsSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::DependentLibrariesSection &Section,
ContiguousBlobAccumulator &CBA);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::CallGraphProfileSection &Section,
ContiguousBlobAccumulator &CBA);
void writeFill(ELFYAML::Fill &Fill, ContiguousBlobAccumulator &CBA);
ELFState(ELFYAML::Object &D, yaml::ErrorHandler EH);
void assignSectionAddress(Elf_Shdr &SHeader, ELFYAML::Section *YAMLSec);
public:
static bool writeELF(raw_ostream &OS, ELFYAML::Object &Doc,
yaml::ErrorHandler EH);
};
} // end anonymous namespace
template <class T> static size_t arrayDataSize(ArrayRef<T> A) {
return A.size() * sizeof(T);
}
template <class T> static void writeArrayData(raw_ostream &OS, ArrayRef<T> A) {
OS.write((const char *)A.data(), arrayDataSize(A));
}
template <class T> static void zero(T &Obj) { memset(&Obj, 0, sizeof(Obj)); }
template <class ELFT>
ELFState<ELFT>::ELFState(ELFYAML::Object &D, yaml::ErrorHandler EH)
: Doc(D), ErrHandler(EH) {
std::vector<ELFYAML::Section *> Sections = Doc.getSections();
StringSet<> DocSections;
for (const ELFYAML::Section *Sec : Sections)
if (!Sec->Name.empty())
DocSections.insert(Sec->Name);
// Insert SHT_NULL section implicitly when it is not defined in YAML.
if (Sections.empty() || Sections.front()->Type != ELF::SHT_NULL)
Doc.Chunks.insert(
Doc.Chunks.begin(),
std::make_unique<ELFYAML::Section>(
ELFYAML::Chunk::ChunkKind::RawContent, /*IsImplicit=*/true));
std::vector<StringRef> ImplicitSections;
if (Doc.DynamicSymbols)
ImplicitSections.insert(ImplicitSections.end(), {".dynsym", ".dynstr"});
if (Doc.Symbols)
ImplicitSections.push_back(".symtab");
ImplicitSections.insert(ImplicitSections.end(), {".strtab", ".shstrtab"});
// Insert placeholders for implicit sections that are not
// defined explicitly in YAML.
for (StringRef SecName : ImplicitSections) {
if (DocSections.count(SecName))
continue;
std::unique_ptr<ELFYAML::Chunk> Sec = std::make_unique<ELFYAML::Section>(
ELFYAML::Chunk::ChunkKind::RawContent, true /*IsImplicit*/);
Sec->Name = SecName;
Doc.Chunks.push_back(std::move(Sec));
}
}
template <class ELFT>
void ELFState<ELFT>::writeELFHeader(ContiguousBlobAccumulator &CBA, raw_ostream &OS) {
using namespace llvm::ELF;
Elf_Ehdr Header;
zero(Header);
Header.e_ident[EI_MAG0] = 0x7f;
Header.e_ident[EI_MAG1] = 'E';
Header.e_ident[EI_MAG2] = 'L';
Header.e_ident[EI_MAG3] = 'F';
Header.e_ident[EI_CLASS] = ELFT::Is64Bits ? ELFCLASS64 : ELFCLASS32;
Header.e_ident[EI_DATA] = Doc.Header.Data;
Header.e_ident[EI_VERSION] = EV_CURRENT;
Header.e_ident[EI_OSABI] = Doc.Header.OSABI;
Header.e_ident[EI_ABIVERSION] = Doc.Header.ABIVersion;
Header.e_type = Doc.Header.Type;
Header.e_machine = Doc.Header.Machine;
Header.e_version = EV_CURRENT;
Header.e_entry = Doc.Header.Entry;
Header.e_phoff = Doc.ProgramHeaders.size() ? sizeof(Header) : 0;
Header.e_flags = Doc.Header.Flags;
Header.e_ehsize = sizeof(Elf_Ehdr);
Header.e_phentsize = Doc.ProgramHeaders.size() ? sizeof(Elf_Phdr) : 0;
Header.e_phnum = Doc.ProgramHeaders.size();
Header.e_shentsize =
Doc.Header.SHEntSize ? (uint16_t)*Doc.Header.SHEntSize : sizeof(Elf_Shdr);
// Immediately following the ELF header and program headers.
// Align the start of the section header and write the ELF header.
uint64_t SHOff;
CBA.getOSAndAlignedOffset(SHOff, sizeof(typename ELFT::uint));
Header.e_shoff =
Doc.Header.SHOff ? typename ELFT::uint(*Doc.Header.SHOff) : SHOff;
Header.e_shnum =
Doc.Header.SHNum ? (uint16_t)*Doc.Header.SHNum : Doc.getSections().size();
Header.e_shstrndx = Doc.Header.SHStrNdx ? (uint16_t)*Doc.Header.SHStrNdx
: SN2I.get(".shstrtab");
OS.write((const char *)&Header, sizeof(Header));
}
template <class ELFT>
void ELFState<ELFT>::initProgramHeaders(std::vector<Elf_Phdr> &PHeaders) {
for (const auto &YamlPhdr : Doc.ProgramHeaders) {
Elf_Phdr Phdr;
Phdr.p_type = YamlPhdr.Type;
Phdr.p_flags = YamlPhdr.Flags;
Phdr.p_vaddr = YamlPhdr.VAddr;
Phdr.p_paddr = YamlPhdr.PAddr;
PHeaders.push_back(Phdr);
}
}
template <class ELFT>
unsigned ELFState<ELFT>::toSectionIndex(StringRef S, StringRef LocSec,
StringRef LocSym) {
unsigned Index;
if (SN2I.lookup(S, Index) || to_integer(S, Index))
return Index;
assert(LocSec.empty() || LocSym.empty());
if (!LocSym.empty())
reportError("unknown section referenced: '" + S + "' by YAML symbol '" +
LocSym + "'");
else
reportError("unknown section referenced: '" + S + "' by YAML section '" +
LocSec + "'");
return 0;
}
template <class ELFT>
unsigned ELFState<ELFT>::toSymbolIndex(StringRef S, StringRef LocSec,
bool IsDynamic) {
const NameToIdxMap &SymMap = IsDynamic ? DynSymN2I : SymN2I;
unsigned Index;
// Here we try to look up S in the symbol table. If it is not there,
// treat its value as a symbol index.
if (!SymMap.lookup(S, Index) && !to_integer(S, Index)) {
reportError("unknown symbol referenced: '" + S + "' by YAML section '" +
LocSec + "'");
return 0;
}
return Index;
}
template <class ELFT>
static void overrideFields(ELFYAML::Section *From, typename ELFT::Shdr &To) {
if (!From)
return;
if (From->ShFlags)
To.sh_flags = *From->ShFlags;
if (From->ShName)
To.sh_name = *From->ShName;
if (From->ShOffset)
To.sh_offset = *From->ShOffset;
if (From->ShSize)
To.sh_size = *From->ShSize;
}
template <class ELFT>
bool ELFState<ELFT>::initImplicitHeader(ContiguousBlobAccumulator &CBA,
Elf_Shdr &Header, StringRef SecName,
ELFYAML::Section *YAMLSec) {
// Check if the header was already initialized.
if (Header.sh_offset)
return false;
if (SecName == ".symtab")
initSymtabSectionHeader(Header, SymtabType::Static, CBA, YAMLSec);
else if (SecName == ".strtab")
initStrtabSectionHeader(Header, SecName, DotStrtab, CBA, YAMLSec);
else if (SecName == ".shstrtab")
initStrtabSectionHeader(Header, SecName, DotShStrtab, CBA, YAMLSec);
else if (SecName == ".dynsym")
initSymtabSectionHeader(Header, SymtabType::Dynamic, CBA, YAMLSec);
else if (SecName == ".dynstr")
initStrtabSectionHeader(Header, SecName, DotDynstr, CBA, YAMLSec);
else
return false;
LocationCounter += Header.sh_size;
// Override section fields if requested.
overrideFields<ELFT>(YAMLSec, Header);
return true;
}
StringRef llvm::ELFYAML::dropUniqueSuffix(StringRef S) {
size_t SuffixPos = S.rfind(" [");
if (SuffixPos == StringRef::npos)
return S;
return S.substr(0, SuffixPos);
}
template <class ELFT>
void ELFState<ELFT>::initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
ContiguousBlobAccumulator &CBA) {
// Ensure SHN_UNDEF entry is present. An all-zero section header is a
// valid SHN_UNDEF entry since SHT_NULL == 0.
SHeaders.resize(Doc.getSections().size());
size_t SecNdx = -1;
for (const std::unique_ptr<ELFYAML::Chunk> &D : Doc.Chunks) {
if (auto S = dyn_cast<ELFYAML::Fill>(D.get())) {
writeFill(*S, CBA);
LocationCounter += S->Size;
continue;
}
++SecNdx;
ELFYAML::Section *Sec = cast<ELFYAML::Section>(D.get());
if (SecNdx == 0 && Sec->IsImplicit)
continue;
// We have a few sections like string or symbol tables that are usually
// added implicitly to the end. However, if they are explicitly specified
// in the YAML, we need to write them here. This ensures the file offset
// remains correct.
Elf_Shdr &SHeader = SHeaders[SecNdx];
if (initImplicitHeader(CBA, SHeader, Sec->Name,
Sec->IsImplicit ? nullptr : Sec))
continue;
assert(Sec && "It can't be null unless it is an implicit section. But all "
"implicit sections should already have been handled above.");
SHeader.sh_name =
DotShStrtab.getOffset(ELFYAML::dropUniqueSuffix(Sec->Name));
SHeader.sh_type = Sec->Type;
if (Sec->Flags)
SHeader.sh_flags = *Sec->Flags;
SHeader.sh_addralign = Sec->AddressAlign;
assignSectionAddress(SHeader, Sec);
if (!Sec->Link.empty())
SHeader.sh_link = toSectionIndex(Sec->Link, Sec->Name);
if (SecNdx == 0) {
if (auto RawSec = dyn_cast<ELFYAML::RawContentSection>(Sec)) {
// We do not write any content for special SHN_UNDEF section.
if (RawSec->Size)
SHeader.sh_size = *RawSec->Size;
if (RawSec->Info)
SHeader.sh_info = *RawSec->Info;
}
if (Sec->EntSize)
SHeader.sh_entsize = *Sec->EntSize;
} else if (auto S = dyn_cast<ELFYAML::RawContentSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::SymtabShndxSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::RelocationSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::RelrSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::Group>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::MipsABIFlags>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::NoBitsSection>(Sec)) {
SHeader.sh_entsize = 0;
SHeader.sh_size = S->Size;
// SHT_NOBITS section does not have content
// so just to setup the section offset.
CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
} else if (auto S = dyn_cast<ELFYAML::DynamicSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::SymverSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::VerneedSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::VerdefSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::StackSizesSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::HashSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::AddrsigSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::LinkerOptionsSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::NoteSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::GnuHashSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::DependentLibrariesSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else if (auto S = dyn_cast<ELFYAML::CallGraphProfileSection>(Sec)) {
writeSectionContent(SHeader, *S, CBA);
} else {
llvm_unreachable("Unknown section type");
}
LocationCounter += SHeader.sh_size;
// Override section fields if requested.
overrideFields<ELFT>(Sec, SHeader);
}
}
template <class ELFT>
void ELFState<ELFT>::assignSectionAddress(Elf_Shdr &SHeader,
ELFYAML::Section *YAMLSec) {
if (YAMLSec && YAMLSec->Address) {
SHeader.sh_addr = *YAMLSec->Address;
LocationCounter = *YAMLSec->Address;
return;
}
// sh_addr represents the address in the memory image of a process. Sections
// in a relocatable object file or non-allocatable sections do not need
// sh_addr assignment.
if (Doc.Header.Type.value == ELF::ET_REL ||
!(SHeader.sh_flags & ELF::SHF_ALLOC))
return;
LocationCounter =
alignTo(LocationCounter, SHeader.sh_addralign ? SHeader.sh_addralign : 1);
SHeader.sh_addr = LocationCounter;
}
static size_t findFirstNonGlobal(ArrayRef<ELFYAML::Symbol> Symbols) {
for (size_t I = 0; I < Symbols.size(); ++I)
if (Symbols[I].Binding.value != ELF::STB_LOCAL)
return I;
return Symbols.size();
}
static uint64_t writeContent(raw_ostream &OS,
const Optional<yaml::BinaryRef> &Content,
const Optional<llvm::yaml::Hex64> &Size) {
size_t ContentSize = 0;
if (Content) {
Content->writeAsBinary(OS);
ContentSize = Content->binary_size();
}
if (!Size)
return ContentSize;
OS.write_zeros(*Size - ContentSize);
return *Size;
}
template <class ELFT>
std::vector<typename ELFT::Sym>
ELFState<ELFT>::toELFSymbols(ArrayRef<ELFYAML::Symbol> Symbols,
const StringTableBuilder &Strtab) {
std::vector<Elf_Sym> Ret;
Ret.resize(Symbols.size() + 1);
size_t I = 0;
for (const ELFYAML::Symbol &Sym : Symbols) {
Elf_Sym &Symbol = Ret[++I];
// If NameIndex, which contains the name offset, is explicitly specified, we
// use it. This is useful for preparing broken objects. Otherwise, we add
// the specified Name to the string table builder to get its offset.
if (Sym.StName)
Symbol.st_name = *Sym.StName;
else if (!Sym.Name.empty())
Symbol.st_name = Strtab.getOffset(ELFYAML::dropUniqueSuffix(Sym.Name));
Symbol.setBindingAndType(Sym.Binding, Sym.Type);
if (!Sym.Section.empty())
Symbol.st_shndx = toSectionIndex(Sym.Section, "", Sym.Name);
else if (Sym.Index)
Symbol.st_shndx = *Sym.Index;
Symbol.st_value = Sym.Value;
Symbol.st_other = Sym.Other ? *Sym.Other : 0;
Symbol.st_size = Sym.Size;
}
return Ret;
}
template <class ELFT>
void ELFState<ELFT>::initSymtabSectionHeader(Elf_Shdr &SHeader,
SymtabType STType,
ContiguousBlobAccumulator &CBA,
ELFYAML::Section *YAMLSec) {
bool IsStatic = STType == SymtabType::Static;
ArrayRef<ELFYAML::Symbol> Symbols;
if (IsStatic && Doc.Symbols)
Symbols = *Doc.Symbols;
else if (!IsStatic && Doc.DynamicSymbols)
Symbols = *Doc.DynamicSymbols;
ELFYAML::RawContentSection *RawSec =
dyn_cast_or_null<ELFYAML::RawContentSection>(YAMLSec);
if (RawSec && (RawSec->Content || RawSec->Size)) {
bool HasSymbolsDescription =
(IsStatic && Doc.Symbols) || (!IsStatic && Doc.DynamicSymbols);
if (HasSymbolsDescription) {
StringRef Property = (IsStatic ? "`Symbols`" : "`DynamicSymbols`");
if (RawSec->Content)
reportError("cannot specify both `Content` and " + Property +
" for symbol table section '" + RawSec->Name + "'");
if (RawSec->Size)
reportError("cannot specify both `Size` and " + Property +
" for symbol table section '" + RawSec->Name + "'");
return;
}
}
zero(SHeader);
SHeader.sh_name = DotShStrtab.getOffset(IsStatic ? ".symtab" : ".dynsym");
if (YAMLSec)
SHeader.sh_type = YAMLSec->Type;
else
SHeader.sh_type = IsStatic ? ELF::SHT_SYMTAB : ELF::SHT_DYNSYM;
if (RawSec && !RawSec->Link.empty()) {
// If the Link field is explicitly defined in the document,
// we should use it.
SHeader.sh_link = toSectionIndex(RawSec->Link, RawSec->Name);
} else {
// When we describe the .dynsym section in the document explicitly, it is
// allowed to omit the "DynamicSymbols" tag. In this case .dynstr is not
// added implicitly and we should be able to leave the Link zeroed if
// .dynstr is not defined.
unsigned Link = 0;
if (IsStatic)
Link = SN2I.get(".strtab");
else
SN2I.lookup(".dynstr", Link);
SHeader.sh_link = Link;
}
if (YAMLSec && YAMLSec->Flags)
SHeader.sh_flags = *YAMLSec->Flags;
else if (!IsStatic)
SHeader.sh_flags = ELF::SHF_ALLOC;
// If the symbol table section is explicitly described in the YAML
// then we should set the fields requested.
SHeader.sh_info = (RawSec && RawSec->Info) ? (unsigned)(*RawSec->Info)
: findFirstNonGlobal(Symbols) + 1;
SHeader.sh_entsize = (YAMLSec && YAMLSec->EntSize)
? (uint64_t)(*YAMLSec->EntSize)
: sizeof(Elf_Sym);
SHeader.sh_addralign = YAMLSec ? (uint64_t)YAMLSec->AddressAlign : 8;
assignSectionAddress(SHeader, YAMLSec);
auto &OS = CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
if (RawSec && (RawSec->Content || RawSec->Size)) {
assert(Symbols.empty());
SHeader.sh_size = writeContent(OS, RawSec->Content, RawSec->Size);
return;
}
std::vector<Elf_Sym> Syms =
toELFSymbols(Symbols, IsStatic ? DotStrtab : DotDynstr);
writeArrayData(OS, makeArrayRef(Syms));
SHeader.sh_size = arrayDataSize(makeArrayRef(Syms));
}
template <class ELFT>
void ELFState<ELFT>::initStrtabSectionHeader(Elf_Shdr &SHeader, StringRef Name,
StringTableBuilder &STB,
ContiguousBlobAccumulator &CBA,
ELFYAML::Section *YAMLSec) {
zero(SHeader);
SHeader.sh_name = DotShStrtab.getOffset(Name);
SHeader.sh_type = YAMLSec ? YAMLSec->Type : ELF::SHT_STRTAB;
SHeader.sh_addralign = YAMLSec ? (uint64_t)YAMLSec->AddressAlign : 1;
ELFYAML::RawContentSection *RawSec =
dyn_cast_or_null<ELFYAML::RawContentSection>(YAMLSec);
auto &OS = CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
if (RawSec && (RawSec->Content || RawSec->Size)) {
SHeader.sh_size = writeContent(OS, RawSec->Content, RawSec->Size);
} else {
STB.write(OS);
SHeader.sh_size = STB.getSize();
}
if (YAMLSec && YAMLSec->EntSize)
SHeader.sh_entsize = *YAMLSec->EntSize;
if (RawSec && RawSec->Info)
SHeader.sh_info = *RawSec->Info;
if (YAMLSec && YAMLSec->Flags)
SHeader.sh_flags = *YAMLSec->Flags;
else if (Name == ".dynstr")
SHeader.sh_flags = ELF::SHF_ALLOC;
assignSectionAddress(SHeader, YAMLSec);
}
template <class ELFT> void ELFState<ELFT>::reportError(const Twine &Msg) {
ErrHandler(Msg);
HasError = true;
}
template <class ELFT>
std::vector<Fragment>
ELFState<ELFT>::getPhdrFragments(const ELFYAML::ProgramHeader &Phdr,
ArrayRef<typename ELFT::Shdr> SHeaders) {
DenseMap<StringRef, ELFYAML::Fill *> NameToFill;
for (const std::unique_ptr<ELFYAML::Chunk> &D : Doc.Chunks)
if (auto S = dyn_cast<ELFYAML::Fill>(D.get()))
NameToFill[S->Name] = S;
std::vector<Fragment> Ret;
for (const ELFYAML::SectionName &SecName : Phdr.Sections) {
unsigned Index;
if (SN2I.lookup(SecName.Section, Index)) {
const typename ELFT::Shdr &H = SHeaders[Index];
Ret.push_back({H.sh_offset, H.sh_size, H.sh_type, H.sh_addralign});
continue;
}
if (ELFYAML::Fill *Fill = NameToFill.lookup(SecName.Section)) {
Ret.push_back({Fill->ShOffset, Fill->Size, llvm::ELF::SHT_PROGBITS,
/*ShAddrAlign=*/1});
continue;
}
reportError("unknown section or fill referenced: '" + SecName.Section +
"' by program header");
}
return Ret;
}
template <class ELFT>
void ELFState<ELFT>::setProgramHeaderLayout(std::vector<Elf_Phdr> &PHeaders,
std::vector<Elf_Shdr> &SHeaders) {
uint32_t PhdrIdx = 0;
for (auto &YamlPhdr : Doc.ProgramHeaders) {
Elf_Phdr &PHeader = PHeaders[PhdrIdx++];
std::vector<Fragment> Fragments = getPhdrFragments(YamlPhdr, SHeaders);
if (!llvm::is_sorted(Fragments, [](const Fragment &A, const Fragment &B) {
return A.Offset < B.Offset;
}))
reportError("sections in the program header with index " +
Twine(PhdrIdx) + " are not sorted by their file offset");
uint64_t PhdrFileOffset = Fragments.empty() ? 0 : Fragments.front().Offset;
if (YamlPhdr.Offset) {
if (!Fragments.empty() && *YamlPhdr.Offset > PhdrFileOffset)
reportError("'Offset' for segment with index " + Twine(PhdrIdx) +
" must be less than or equal to the minimum file offset of "
"all included sections (0x" +
Twine::utohexstr(PhdrFileOffset) + ")");
PhdrFileOffset = *YamlPhdr.Offset;
}
PHeader.p_offset = PhdrFileOffset;
// Find the maximum offset of the end of a section in order to set p_filesz
// and p_memsz. When setting p_filesz, trailing SHT_NOBITS sections are not
// counted.
uint64_t FileOffset = PHeader.p_offset, MemOffset = PHeader.p_offset;
for (const Fragment &F : Fragments) {
uint64_t End = F.Offset + F.Size;
MemOffset = std::max(MemOffset, End);
if (F.Type != llvm::ELF::SHT_NOBITS)
FileOffset = std::max(FileOffset, End);
}
// Set the file size and the memory size if not set explicitly.
PHeader.p_filesz = YamlPhdr.FileSize ? uint64_t(*YamlPhdr.FileSize)
: FileOffset - PHeader.p_offset;
PHeader.p_memsz = YamlPhdr.MemSize ? uint64_t(*YamlPhdr.MemSize)
: MemOffset - PHeader.p_offset;
if (YamlPhdr.Align) {
PHeader.p_align = *YamlPhdr.Align;
} else {
// Set the alignment of the segment to be the maximum alignment of the
// sections so that by default the segment has a valid and sensible
// alignment.
PHeader.p_align = 1;
for (const Fragment &F : Fragments)
PHeader.p_align = std::max((uint64_t)PHeader.p_align, F.AddrAlign);
}
}
}
template <class ELFT>
void ELFState<ELFT>::writeSectionContent(
Elf_Shdr &SHeader, const ELFYAML::RawContentSection &Section,
ContiguousBlobAccumulator &CBA) {
raw_ostream &OS =
CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
SHeader.sh_size = writeContent(OS, Section.Content, Section.Size);
if (Section.EntSize)
SHeader.sh_entsize = *Section.EntSize;
if (Section.Info)
SHeader.sh_info = *Section.Info;
}
static bool isMips64EL(const ELFYAML::Object &Doc) {
return Doc.Header.Machine == ELFYAML::ELF_EM(llvm::ELF::EM_MIPS) &&
Doc.Header.Class == ELFYAML::ELF_ELFCLASS(ELF::ELFCLASS64) &&
Doc.Header.Data == ELFYAML::ELF_ELFDATA(ELF::ELFDATA2LSB);
}
template <class ELFT>
void ELFState<ELFT>::writeSectionContent(
Elf_Shdr &SHeader, const ELFYAML::RelocationSection &Section,
ContiguousBlobAccumulator &CBA) {
assert((Section.Type == llvm::ELF::SHT_REL ||
Section.Type == llvm::ELF::SHT_RELA) &&
"Section type is not SHT_REL nor SHT_RELA");
bool IsRela = Section.Type == llvm::ELF::SHT_RELA;
if (Section.EntSize)
SHeader.sh_entsize = *Section.EntSize;
else
SHeader.sh_entsize = IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
SHeader.sh_size = (IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel)) *
Section.Relocations.size();
// For relocation section set link to .symtab by default.
unsigned Link = 0;
if (Section.Link.empty() && SN2I.lookup(".symtab", Link))
SHeader.sh_link = Link;
if (!Section.RelocatableSec.empty())
SHeader.sh_info = toSectionIndex(Section.RelocatableSec, Section.Name);
auto &OS = CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
for (const auto &Rel : Section.Relocations) {
unsigned SymIdx = Rel.Symbol ? toSymbolIndex(*Rel.Symbol, Section.Name,
Section.Link == ".dynsym")
: 0;
if (IsRela) {
Elf_Rela REntry;
zero(REntry);
REntry.r_offset = Rel.Offset;
REntry.r_addend = Rel.Addend;
REntry.setSymbolAndType(SymIdx, Rel.Type, isMips64EL(Doc));
OS.write((const char *)&REntry, sizeof(REntry));
} else {
Elf_Rel REntry;
zero(REntry);
REntry.r_offset = Rel.Offset;
REntry.setSymbolAndType(SymIdx, Rel.Type, isMips64EL(Doc));
OS.write((const char *)&REntry, sizeof(REntry));
}
}
}
template <class ELFT>
void ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::RelrSection &Section,
ContiguousBlobAccumulator &CBA) {
raw_ostream &OS =
CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
SHeader.sh_entsize =
Section.EntSize ? uint64_t(*Section.EntSize) : sizeof(Elf_Relr);
if (Section.Content) {
SHeader.sh_size = writeContent(OS, Section.Content, None);
return;
}
if (!Section.Entries)
return;
for (llvm::yaml::Hex64 E : *Section.Entries) {
if (!ELFT::Is64Bits && E > UINT32_MAX)
reportError(Section.Name + ": the value is too large for 32-bits: 0x" +
Twine::utohexstr(E));
support::endian::write<uintX_t>(OS, E, ELFT::TargetEndianness);
}
SHeader.sh_size = sizeof(uintX_t) * Section.Entries->size();
}
template <class ELFT>
void ELFState<ELFT>::writeSectionContent(
Elf_Shdr &SHeader, const ELFYAML::SymtabShndxSection &Shndx,
ContiguousBlobAccumulator &CBA) {
raw_ostream &OS =
CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
for (uint32_t E : Shndx.Entries)
support::endian::write<uint32_t>(OS, E, ELFT::TargetEndianness);
SHeader.sh_entsize = Shndx.EntSize ? (uint64_t)*Shndx.EntSize : 4;
SHeader.sh_size = Shndx.Entries.size() * SHeader.sh_entsize;
}
template <class ELFT>
void ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::Group &Section,
ContiguousBlobAccumulator &CBA) {
assert(Section.Type == llvm::ELF::SHT_GROUP &&
"Section type is not SHT_GROUP");
unsigned Link = 0;
if (Section.Link.empty() && SN2I.lookup(".symtab", Link))
SHeader.sh_link = Link;
SHeader.sh_entsize = 4;
SHeader.sh_size = SHeader.sh_entsize * Section.Members.size();
if (Section.Signature)
SHeader.sh_info =
toSymbolIndex(*Section.Signature, Section.Name, /*IsDynamic=*/false);
raw_ostream &OS =
CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
for (const ELFYAML::SectionOrType &Member : Section.Members) {
unsigned int SectionIndex = 0;
if (Member.sectionNameOrType == "GRP_COMDAT")
SectionIndex = llvm::ELF::GRP_COMDAT;
else
SectionIndex = toSectionIndex(Member.sectionNameOrType, Section.Name);
support::endian::write<uint32_t>(OS, SectionIndex, ELFT::TargetEndianness);
}
}
template <class ELFT>
void ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::SymverSection &Section,
ContiguousBlobAccumulator &CBA) {
raw_ostream &OS =
CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
for (uint16_t Version : Section.Entries)
support::endian::write<uint16_t>(OS, Version, ELFT::TargetEndianness);
SHeader.sh_entsize = Section.EntSize ? (uint64_t)*Section.EntSize : 2;
SHeader.sh_size = Section.Entries.size() * SHeader.sh_entsize;
}
template <class ELFT>
void ELFState<ELFT>::writeSectionContent(
Elf_Shdr &SHeader, const ELFYAML::StackSizesSection &Section,
ContiguousBlobAccumulator &CBA) {
raw_ostream &OS =
CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
if (Section.Content || Section.Size) {
SHeader.sh_size = writeContent(OS, Section.Content, Section.Size);
return;
}
for (const ELFYAML::StackSizeEntry &E : *Section.Entries) {
support::endian::write<uintX_t>(OS, E.Address, ELFT::TargetEndianness);
SHeader.sh_size += sizeof(uintX_t) + encodeULEB128(E.Size, OS);
}
}
template <class ELFT>
void ELFState<ELFT>::writeSectionContent(
Elf_Shdr &SHeader, const ELFYAML::LinkerOptionsSection &Section,
ContiguousBlobAccumulator &CBA) {
raw_ostream &OS =
CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
if (Section.Content) {
SHeader.sh_size = writeContent(OS, Section.Content, None);
return;
}
if (!Section.Options)
return;
for (const ELFYAML::LinkerOption &LO : *Section.Options) {
OS.write(LO.Key.data(), LO.Key.size());
OS.write('\0');
OS.write(LO.Value.data(), LO.Value.size());
OS.write('\0');
SHeader.sh_size += (LO.Key.size() + LO.Value.size() + 2);
}
}
template <class ELFT>
void ELFState<ELFT>::writeSectionContent(
Elf_Shdr &SHeader, const ELFYAML::DependentLibrariesSection &Section,