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Add ELF dynamic symbol support to yaml2obj/obj2yaml

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Summary:
This change introduces a `DynamicSymbols` field to the ELF specific YAML
supported by `yaml2obj` and `obj2yaml`. This grouping of symbols provides a way
to represent ELF dynamic symbols. The `DynamicSymbols` structure is identical to
the existing `Symbols`.

Reviewers: compnerd, jakehehrlich, silvas

Reviewed By: silvas

Subscribers: silvas, jakehehrlich, llvm-commits

Differential Revision: https://reviews.llvm.org/D39582

llvm-svn: 318433
This commit is contained in:
Dave Lee 2017-11-16 18:10:15 +00:00
parent d1dcda1969
commit 67b4966ccd
6 changed files with 135 additions and 40 deletions
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1
llvm/include/llvm/ObjectYAML/ELFYAML.h
View File

@ -207,6 +207,7 @@ struct Object {
// top-level key, which automatically ensures that invariants like there
// being a single SHT_SYMTAB section are upheld.
LocalGlobalWeakSymbols Symbols;
LocalGlobalWeakSymbols DynamicSymbols;
};
} // end namespace ELFYAML

1
llvm/lib/ObjectYAML/ELFYAML.cpp
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@ -933,6 +933,7 @@ void MappingTraits<ELFYAML::Object>::mapping(IO &IO, ELFYAML::Object &Object) {
IO.mapOptional("ProgramHeaders", Object.ProgramHeaders);
IO.mapOptional("Sections", Object.Sections);
IO.mapOptional("Symbols", Object.Symbols);
IO.mapOptional("DynamicSymbols", Object.DynamicSymbols);
IO.setContext(nullptr);
}

41
llvm/test/tools/yaml2obj/dynamic-symbols.yaml Normal file
View File

@ -0,0 +1,41 @@
# Ensures that implicitly added sections can be ordered within Sections.
# RUN: yaml2obj %s -o %t
# RUN: llvm-readobj -sections %t | FileCheck %s --check-prefix=SECTION
# RUN: llvm-nm -dynamic %t | FileCheck %s --check-prefix=SYMBOL
!ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_DYN
Machine: EM_X86_64
Sections:
- Name: .data
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC, SHF_WRITE ]
DynamicSymbols:
Global:
- Name: dynglobal
Type: STT_OBJECT
Section: .data
Weak:
- Name: dynweak
Type: STT_OBJECT
Section: .data
Local:
- Name: dynlocal
Type: STT_OBJECT
Section: .data
# SECTION: Name: .dynsym
# SECTION-NEXT: Type: SHT_DYNSYM
# SECTION-NEXT: Flags
# SECTION-NEXT: SHF_ALLOC
# SECTION: Name: .dynstr
# SECTION-NEXT: Type: SHT_STRTAB
# SECTION-NEXT: Flags
# SECTION-NEXT: SHF_ALLOC
# SYMBOL-DAG: D dynglobal
# SYMBOL-DAG: V dynweak
# SYMBOL-DAG: d dynlocal

1
llvm/tools/llvm-readobj/ELFDumper.cpp
View File

@ -1322,6 +1322,7 @@ ELFDumper<ELFT>::ELFDumper(const ELFFile<ELFT> *Obj, ScopedPrinter &Writer)
DynSymRegion = createDRIFrom(&Sec);
// This is only used (if Elf_Shdr present)for naming section in GNU style
DynSymtabName = unwrapOrError(Obj->getSectionName(&Sec));
DynamicStringTable = unwrapOrError(Obj->getStringTableForSymtab(Sec));
break;
case ELF::SHT_SYMTAB_SHNDX:
ShndxTable = unwrapOrError(Obj->getSHNDXTable(Sec));

42
llvm/tools/obj2yaml/elf2yaml.cpp
View File

@ -42,6 +42,8 @@ class ELFDumper {
const object::ELFFile<ELFT> &Obj;
ArrayRef<Elf_Word> ShndxTable;
std::error_code dumpSymbols(const Elf_Shdr *Symtab,
ELFYAML::LocalGlobalWeakSymbols &Symbols);
std::error_code dumpSymbol(const Elf_Sym *Sym, const Elf_Shdr *SymTab,
StringRef StrTable, ELFYAML::Symbol &S);
std::error_code dumpCommonSection(const Elf_Shdr *Shdr, ELFYAML::Section &S);
@ -119,6 +121,7 @@ template <class ELFT> ErrorOr<ELFYAML::Object *> ELFDumper<ELFT>::dump() {
Y->Header.Entry = Obj.getHeader()->e_entry;
const Elf_Shdr *Symtab = nullptr;
const Elf_Shdr *DynSymtab = nullptr;
// Dump sections
auto SectionsOrErr = Obj.sections();
@ -129,13 +132,15 @@ template <class ELFT> ErrorOr<ELFYAML::Object *> ELFDumper<ELFT>::dump() {
for (const Elf_Shdr &Sec : Sections) {
switch (Sec.sh_type) {
case ELF::SHT_NULL:
case ELF::SHT_DYNSYM:
case ELF::SHT_STRTAB:
// Do not dump these sections.
break;
case ELF::SHT_SYMTAB:
Symtab = &Sec;
break;
case ELF::SHT_DYNSYM:
DynSymtab = &Sec;
break;
case ELF::SHT_SYMTAB_SHNDX: {
auto TableOrErr = Obj.getSHNDXTable(Sec);
if (!TableOrErr)
@ -187,46 +192,57 @@ template <class ELFT> ErrorOr<ELFYAML::Object *> ELFDumper<ELFT>::dump() {
}
}
// Dump symbols
if (auto EC = dumpSymbols(Symtab, Y->Symbols))
return EC;
if (auto EC = dumpSymbols(DynSymtab, Y->DynamicSymbols))
return EC;
return Y.release();
}
template <class ELFT>
std::error_code
ELFDumper<ELFT>::dumpSymbols(const Elf_Shdr *Symtab,
ELFYAML::LocalGlobalWeakSymbols &Symbols) {
if (!Symtab)
return Y.release(); // if the symbol table is missing return early
return std::error_code();
auto StrTableOrErr = Obj.getStringTableForSymtab(*Symtab);
if (!StrTableOrErr)
return errorToErrorCode(StrTableOrErr.takeError());
StringRef StrTable = *StrTableOrErr;
bool IsFirstSym = true;
auto SymtabOrErr = Obj.symbols(Symtab);
if (!SymtabOrErr)
return errorToErrorCode(SymtabOrErr.takeError());
for (const Elf_Sym &Sym : *SymtabOrErr) {
bool IsFirstSym = true;
for (const auto &Sym : *SymtabOrErr) {
if (IsFirstSym) {
IsFirstSym = false;
continue;
}
ELFYAML::Symbol S;
if (std::error_code EC =
ELFDumper<ELFT>::dumpSymbol(&Sym, Symtab, StrTable, S))
if (auto EC = dumpSymbol(&Sym, Symtab, StrTable, S))
return EC;
switch (Sym.getBinding())
{
switch (Sym.getBinding()) {
case ELF::STB_LOCAL:
Y->Symbols.Local.push_back(S);
Symbols.Local.push_back(S);
break;
case ELF::STB_GLOBAL:
Y->Symbols.Global.push_back(S);
Symbols.Global.push_back(S);
break;
case ELF::STB_WEAK:
Y->Symbols.Weak.push_back(S);
Symbols.Weak.push_back(S);
break;
default:
llvm_unreachable("Unknown ELF symbol binding");
}
}
return Y.release();
return std::error_code();
}
template <class ELFT>

89
llvm/tools/yaml2obj/yaml2elf.cpp
View File

@ -114,12 +114,17 @@ class ELFState {
typedef typename object::ELFFile<ELFT>::Elf_Rel Elf_Rel;
typedef typename object::ELFFile<ELFT>::Elf_Rela Elf_Rela;
enum class SymtabType { Static, Dynamic };
/// \brief The future ".strtab" section.
StringTableBuilder DotStrtab{StringTableBuilder::ELF};
/// \brief The future ".shstrtab" section.
StringTableBuilder DotShStrtab{StringTableBuilder::ELF};
/// \brief The future ".dynstr" section.
StringTableBuilder DotDynstr{StringTableBuilder::ELF};
NameToIdxMap SN2I;
NameToIdxMap SymN2I;
const ELFYAML::Object &Doc;
@ -131,7 +136,7 @@ class ELFState {
void initProgramHeaders(std::vector<Elf_Phdr> &PHeaders);
bool initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
ContiguousBlobAccumulator &CBA);
void initSymtabSectionHeader(Elf_Shdr &SHeader,
void initSymtabSectionHeader(Elf_Shdr &SHeader, SymtabType STType,
ContiguousBlobAccumulator &CBA);
void initStrtabSectionHeader(Elf_Shdr &SHeader, StringRef Name,
StringTableBuilder &STB,
@ -139,7 +144,8 @@ class ELFState {
void setProgramHeaderLayout(std::vector<Elf_Phdr> &PHeaders,
std::vector<Elf_Shdr> &SHeaders);
void addSymbols(const std::vector<ELFYAML::Symbol> &Symbols,
std::vector<Elf_Sym> &Syms, unsigned SymbolBinding);
std::vector<Elf_Sym> &Syms, unsigned SymbolBinding,
const StringTableBuilder &Strtab);
void writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::RawContentSection &Section,
ContiguousBlobAccumulator &CBA);
@ -151,14 +157,20 @@ class ELFState {
bool writeSectionContent(Elf_Shdr &SHeader,
const ELFYAML::MipsABIFlags &Section,
ContiguousBlobAccumulator &CBA);
bool hasDynamicSymbols() const;
SmallVector<const char *, 5> implicitSectionNames() const;
// - SHT_NULL entry (placed first, i.e. 0'th entry)
// - symbol table (.symtab) (defaults to third to last)
// - string table (.strtab) (defaults to second to last)
// - section header string table (.shstrtab) (defaults to last)
// - symbol table (.symtab) (defaults to after last yaml section)
// - string table (.strtab) (defaults to after .symtab)
// - section header string table (.shstrtab) (defaults to after .strtab)
// - dynamic symbol table (.dynsym) (defaults to after .shstrtab)
// - dynamic string table (.dynstr) (defaults to after .dynsym)
unsigned getDotSymTabSecNo() const { return SN2I.get(".symtab"); }
unsigned getDotStrTabSecNo() const { return SN2I.get(".strtab"); }
unsigned getDotShStrTabSecNo() const { return SN2I.get(".shstrtab"); }
unsigned getDotDynSymSecNo() const { return SN2I.get(".dynsym"); }
unsigned getDotDynStrSecNo() const { return SN2I.get(".dynstr"); }
unsigned getSectionCount() const { return SN2I.size() + 1; }
ELFState(const ELFYAML::Object &D) : Doc(D) {}
@ -166,8 +178,6 @@ class ELFState {
public:
static int writeELF(raw_ostream &OS, const ELFYAML::Object &Doc);
};
static const char * const ImplicitSecNames[] = {".symtab", ".strtab", ".shstrtab"};
} // end anonymous namespace
template <class ELFT>
@ -288,13 +298,17 @@ bool ELFState<ELFT>::initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
template <class ELFT>
void ELFState<ELFT>::initSymtabSectionHeader(Elf_Shdr &SHeader,
SymtabType STType,
ContiguousBlobAccumulator &CBA) {
zero(SHeader);
SHeader.sh_name = DotShStrtab.getOffset(".symtab");
SHeader.sh_type = ELF::SHT_SYMTAB;
SHeader.sh_link = getDotStrTabSecNo();
bool IsStatic = STType == SymtabType::Static;
SHeader.sh_name = DotShStrtab.getOffset(IsStatic ? ".symtab" : ".dynsym");
SHeader.sh_type = IsStatic ? ELF::SHT_SYMTAB : ELF::SHT_DYNSYM;
SHeader.sh_link = IsStatic ? getDotStrTabSecNo() : getDotDynStrSecNo();
const auto &Symbols = IsStatic ? Doc.Symbols : Doc.DynamicSymbols;
auto &Strtab = IsStatic ? DotStrtab : DotDynstr;
// One greater than symbol table index of the last local symbol.
SHeader.sh_info = Doc.Symbols.Local.size() + 1;
SHeader.sh_info = Symbols.Local.size() + 1;
SHeader.sh_entsize = sizeof(Elf_Sym);
SHeader.sh_addralign = 8;
@ -306,18 +320,18 @@ void ELFState<ELFT>::initSymtabSectionHeader(Elf_Shdr &SHeader,
Syms.push_back(Sym);
}
// Add symbol names to .strtab.
for (const auto &Sym : Doc.Symbols.Local)
DotStrtab.add(Sym.Name);
for (const auto &Sym : Doc.Symbols.Global)
DotStrtab.add(Sym.Name);
for (const auto &Sym : Doc.Symbols.Weak)
DotStrtab.add(Sym.Name);
DotStrtab.finalize();
// Add symbol names to .strtab or .dynstr.
for (const auto &Sym : Symbols.Local)
Strtab.add(Sym.Name);
for (const auto &Sym : Symbols.Global)
Strtab.add(Sym.Name);
for (const auto &Sym : Symbols.Weak)
Strtab.add(Sym.Name);
Strtab.finalize();
addSymbols(Doc.Symbols.Local, Syms, ELF::STB_LOCAL);
addSymbols(Doc.Symbols.Global, Syms, ELF::STB_GLOBAL);
addSymbols(Doc.Symbols.Weak, Syms, ELF::STB_WEAK);
addSymbols(Symbols.Local, Syms, ELF::STB_LOCAL, Strtab);
addSymbols(Symbols.Global, Syms, ELF::STB_GLOBAL, Strtab);
addSymbols(Symbols.Weak, Syms, ELF::STB_WEAK, Strtab);
writeArrayData(
CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign),
@ -405,12 +419,13 @@ void ELFState<ELFT>::setProgramHeaderLayout(std::vector<Elf_Phdr> &PHeaders,
template <class ELFT>
void ELFState<ELFT>::addSymbols(const std::vector<ELFYAML::Symbol> &Symbols,
std::vector<Elf_Sym> &Syms,
unsigned SymbolBinding) {
unsigned SymbolBinding,
const StringTableBuilder &Strtab) {
for (const auto &Sym : Symbols) {
Elf_Sym Symbol;
zero(Symbol);
if (!Sym.Name.empty())
Symbol.st_name = DotStrtab.getOffset(Sym.Name);
Symbol.st_name = Strtab.getOffset(Sym.Name);
Symbol.setBindingAndType(SymbolBinding, Sym.Type);
if (!Sym.Section.empty()) {
unsigned Index;
@ -567,7 +582,7 @@ template <class ELFT> bool ELFState<ELFT>::buildSectionIndex() {
auto SecNo = 1 + Doc.Sections.size();
// Add special sections after input sections, if necessary.
for (const auto &Name : ImplicitSecNames)
for (const auto &Name : implicitSectionNames())
if (!SN2I.addName(Name, SecNo)) {
// Account for this section, since it wasn't in the Doc
++SecNo;
@ -626,17 +641,25 @@ int ELFState<ELFT>::writeELF(raw_ostream &OS, const ELFYAML::Object &Doc) {
return 1;
// Populate SHeaders with implicit sections not present in the Doc
for (const auto &Name : ImplicitSecNames)
for (const auto &Name : State.implicitSectionNames())
if (State.SN2I.get(Name) >= SHeaders.size())
SHeaders.push_back({});
// Initialize the implicit sections
auto Index = State.SN2I.get(".symtab");
State.initSymtabSectionHeader(SHeaders[Index], CBA);
State.initSymtabSectionHeader(SHeaders[Index], SymtabType::Static, CBA);
Index = State.SN2I.get(".strtab");
State.initStrtabSectionHeader(SHeaders[Index], ".strtab", State.DotStrtab, CBA);
Index = State.SN2I.get(".shstrtab");
State.initStrtabSectionHeader(SHeaders[Index], ".shstrtab", State.DotShStrtab, CBA);
if (State.hasDynamicSymbols()) {
Index = State.SN2I.get(".dynsym");
State.initSymtabSectionHeader(SHeaders[Index], SymtabType::Dynamic, CBA);
SHeaders[Index].sh_flags |= ELF::SHF_ALLOC;
Index = State.SN2I.get(".dynstr");
State.initStrtabSectionHeader(SHeaders[Index], ".dynstr", State.DotDynstr, CBA);
SHeaders[Index].sh_flags |= ELF::SHF_ALLOC;
}
// Now we can decide segment offsets
State.setProgramHeaderLayout(PHeaders, SHeaders);
@ -648,6 +671,18 @@ int ELFState<ELFT>::writeELF(raw_ostream &OS, const ELFYAML::Object &Doc) {
return 0;
}
template <class ELFT> bool ELFState<ELFT>::hasDynamicSymbols() const {
return Doc.DynamicSymbols.Global.size() > 0 ||
Doc.DynamicSymbols.Weak.size() > 0 ||
Doc.DynamicSymbols.Local.size() > 0;
}
template <class ELFT> SmallVector<const char *, 5> ELFState<ELFT>::implicitSectionNames() const {
if (!hasDynamicSymbols())
return {".symtab", ".strtab", ".shstrtab"};
return {".symtab", ".strtab", ".shstrtab", ".dynsym", ".dynstr"};
}
static bool is64Bit(const ELFYAML::Object &Doc) {
return Doc.Header.Class == ELFYAML::ELF_ELFCLASS(ELF::ELFCLASS64);
}