Skip to content

Commit

Permalink
[llvm-objcopy] Refactor code to include initialize method
Browse files Browse the repository at this point in the history 
This change refactors some of the code to allow for some code
deduplication in later diffs as well as just to make adding a new
section type more self contained to the class itself. The idea for this
was first mentioned by James in D 37915 and will be used in that change
as recommended.

This change follows changes for dynamic sections but precedes support
for dynamic relocations.

Differential Revision: https://reviews.llvm.org/D38008

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@314148 91177308-0d34-0410-b5e6-96231b3b80d8
  • Loading branch information
@jakehehrlich
jakehehrlich committed Sep 25, 2017
1 parent 00b5bff commit 408651e
Show file tree
Hide file tree
Showing 2 changed files with 92 additions and 34 deletions.
100 changes: 68 additions & 32 deletions tools/llvm-objcopy/Object.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,7 @@ void Segment::writeSegment(FileOutputBuffer &Out) const {
std::copy(std::begin(Contents), std::end(Contents), Buf);
}

void SectionBase::initialize(SectionTableRef SecTable) {}
void SectionBase::finalize() {}

template <class ELFT>
Expand Down Expand Up @@ -149,6 +150,16 @@ void SymbolTableSection::addSymbol(StringRef Name, uint8_t Bind, uint8_t Type,
Size += this->EntrySize;
}

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() {
// Make sure SymbolNames is finalized before getting name indexes.
SymbolNames->finalize();
Expand Down Expand Up @@ -195,6 +206,19 @@ void SymbolTableSectionImpl<ELFT>::writeSection(
}
}

template <class ELFT>
void RelocationSection<ELFT>::initialize(SectionTableRef SecTable) {
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"));

setSection(SecTable.getSection(Info,
"Info field value " + Twine(Info) +
" in section " + Name + " is invalid"));
}

template <class ELFT> void RelocationSection<ELFT>::finalize() {
this->Link = Symbols->Index;
this->Info = SecToApplyRel->Index;
Expand Down Expand Up @@ -232,6 +256,14 @@ bool SectionWithStrTab::classof(const SectionBase *S) {
return isa<DynamicSymbolTableSection>(S) || isa<DynamicSection>(S);
}

void SectionWithStrTab::initialize(SectionTableRef SecTable) {
setStrTab(SecTable.getSectionOfType<StringTableSection>(
Link,
"Link field value " + Twine(Link) + " in section " + Name + " is invalid",
"Link field value " + Twine(Link) + " in section " + Name +
" is not a string table"));
}

void SectionWithStrTab::finalize() { this->Link = StrTab->Index; }

// Returns true IFF a section is wholly inside the range of a segment
Expand Down Expand Up @@ -311,15 +343,8 @@ void Object<ELFT>::readProgramHeaders(const ELFFile<ELFT> &ElfFile) {

template <class ELFT>
void Object<ELFT>::initSymbolTable(const llvm::object::ELFFile<ELFT> &ElfFile,
SymbolTableSection *SymTab) {

SymTab->Size = 0;
SymTab->setStrTab(getSectionOfType<StringTableSection>(
SymbolTable->Link,
"Symbol table has link index of " + Twine(SymTab->Link) +
" which is not a valid index",
"Symbol table has link index of " + Twine(SymTab->Link) +
" which is not a string table"));
SymbolTableSection *SymTab,
SectionTableRef SecTable) {

const Elf_Shdr &Shdr = *unwrapOrError(ElfFile.getSection(SymTab->Index));
StringRef StrTabData = unwrapOrError(ElfFile.getStringTableForSymtab(Shdr));
Expand All @@ -336,7 +361,7 @@ void Object<ELFT>::initSymbolTable(const llvm::object::ELFFile<ELFT> &ElfFile,
Twine(Sym.st_shndx));
}
} else if (Sym.st_shndx != SHN_UNDEF) {
DefSection = getSection(
DefSection = SecTable.getSection(
Sym.st_shndx,
"Symbol '" + Name + "' is defined in invalid section with index " +
Twine(Sym.st_shndx));
Expand Down Expand Up @@ -368,6 +393,20 @@ void initRelocations(RelocationSection<ELFT> *Relocs,
}
}

SectionBase *SectionTableRef::getSection(uint16_t Index, Twine ErrMsg) {
if (Index == SHN_UNDEF || Index > Sections.size())
error(ErrMsg);
return Sections[Index - 1].get();
}

template <class T>
T *SectionTableRef::getSectionOfType(uint16_t Index, Twine IndexErrMsg,
Twine TypeErrMsg) {
if (T *Sec = llvm::dyn_cast<T>(getSection(Index, IndexErrMsg)))
return Sec;
error(TypeErrMsg);
}

template <class ELFT>
SectionBase *Object<ELFT>::getSection(uint16_t Index, Twine ErrMsg) {
if (Index == SHN_UNDEF || Index > Sections.size())
Expand Down Expand Up @@ -428,7 +467,7 @@ Object<ELFT>::makeSection(const llvm::object::ELFFile<ELFT> &ElfFile,
}

template <class ELFT>
void Object<ELFT>::readSectionHeaders(const ELFFile<ELFT> &ElfFile) {
SectionTableRef Object<ELFT>::readSectionHeaders(const ELFFile<ELFT> &ElfFile) {
uint32_t Index = 0;
for (const auto &Shdr : unwrapOrError(ElfFile.sections())) {
if (Index == 0) {
Expand All @@ -451,35 +490,30 @@ void Object<ELFT>::readSectionHeaders(const ELFFile<ELFT> &ElfFile) {
Sections.push_back(std::move(Sec));
}

SectionTableRef SecTable(Sections);

// Now that all of the sections have been added we can fill out some extra
// details about symbol tables.
if (SymbolTable)
initSymbolTable(ElfFile, SymbolTable);
// details about symbol tables. We need the symbol table filled out before
// any relocations.
if (SymbolTable) {
SymbolTable->initialize(SecTable);
initSymbolTable(ElfFile, SymbolTable, SecTable);
}

// 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 &Section : Sections) {
if (Section.get() == SymbolTable)
continue;
Section->initialize(SecTable);
if (auto RelSec = dyn_cast<RelocationSection<ELFT>>(Section.get())) {

auto SymTab = getSectionOfType<SymbolTableSection>(
RelSec->Link,
"Link field value " + Twine(RelSec->Link) + " in section " +
RelSec->Name + " is invalid",
"Link field value " + Twine(RelSec->Link) + " in section " +
RelSec->Name + " is not a symbol table");
RelSec->setSymTab(SymTab);

RelSec->setSection(getSection(RelSec->Info,
"Info field value " + Twine(RelSec->Link) +
" in section " + RelSec->Name +
" is invalid"));

auto Shdr = unwrapOrError(ElfFile.sections()).begin() + RelSec->Index;
if (RelSec->Type == SHT_REL)
initRelocations(RelSec, SymTab, unwrapOrError(ElfFile.rels(Shdr)));
initRelocations(RelSec, SymbolTable, unwrapOrError(ElfFile.rels(Shdr)));
else
initRelocations(RelSec, SymTab, unwrapOrError(ElfFile.relas(Shdr)));
initRelocations(RelSec, SymbolTable,
unwrapOrError(ElfFile.relas(Shdr)));
}

if (auto Sec = dyn_cast<SectionWithStrTab>(Section.get())) {
Expand All @@ -491,6 +525,8 @@ void Object<ELFT>::readSectionHeaders(const ELFFile<ELFT> &ElfFile) {
" is not a string table"));
}
}

return SecTable;
}

template <class ELFT> Object<ELFT>::Object(const ELFObjectFile<ELFT> &Obj) {
Expand All @@ -504,10 +540,10 @@ template <class ELFT> Object<ELFT>::Object(const ELFObjectFile<ELFT> &Obj) {
Entry = Ehdr.e_entry;
Flags = Ehdr.e_flags;

readSectionHeaders(ElfFile);
SectionTableRef SecTable = readSectionHeaders(ElfFile);
readProgramHeaders(ElfFile);

SectionNames = getSectionOfType<StringTableSection>(
SectionNames = SecTable.getSectionOfType<StringTableSection>(
Ehdr.e_shstrndx,
"e_shstrndx field value " + Twine(Ehdr.e_shstrndx) + " in elf header " +
" is invalid",
Expand Down
26 changes: 24 additions & 2 deletions tools/llvm-objcopy/Object.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,24 @@
#include <set>

class Segment;
class SectionBase;

class SectionTableRef {
private:
llvm::ArrayRef<std::unique_ptr<SectionBase>> Sections;

public:
SectionTableRef(llvm::ArrayRef<std::unique_ptr<SectionBase>> Secs)
: Sections(Secs) {}
SectionTableRef(const SectionTableRef &) = default;

SectionBase *getSection(uint16_t Index, llvm::Twine ErrMsg);

template <class T>

T *getSectionOfType(uint16_t Index, llvm::Twine IndexErrMsg,
llvm::Twine TypeErrMsg);
};

class SectionBase {
public:
Expand All @@ -39,6 +57,7 @@ class SectionBase {
uint64_t Type = llvm::ELF::SHT_NULL;

virtual ~SectionBase() {}
virtual void initialize(SectionTableRef SecTable);
virtual void finalize();
template <class ELFT> void writeHeader(llvm::FileOutputBuffer &Out) const;
virtual void writeSection(llvm::FileOutputBuffer &Out) const = 0;
Expand Down Expand Up @@ -154,6 +173,7 @@ class SymbolTableSection : public SectionBase {
uint64_t Sz);
void addSymbolNames();
const Symbol *getSymbolByIndex(uint32_t Index) const;
void initialize(SectionTableRef SecTable) override;
void finalize() override;
static bool classof(const SectionBase *S) {
return S->Type == llvm::ELF::SHT_SYMTAB;
Expand Down Expand Up @@ -187,6 +207,7 @@ template <class ELFT> class RelocationSection : public SectionBase {
void setSymTab(SymbolTableSection *StrTab) { Symbols = StrTab; }
void setSection(SectionBase *Sec) { SecToApplyRel = Sec; }
void addRelocation(Relocation Rel) { Relocations.push_back(Rel); }
void initialize(SectionTableRef SecTable) override;
void finalize() override;
void writeSection(llvm::FileOutputBuffer &Out) const override;
static bool classof(const SectionBase *S) {
Expand All @@ -201,6 +222,7 @@ class SectionWithStrTab : public Section {
public:
SectionWithStrTab(llvm::ArrayRef<uint8_t> Data) : Section(Data) {}
void setStrTab(StringTableSection *StringTable) { StrTab = StringTable; }
void initialize(SectionTableRef SecTable) override;
void finalize() override;
static bool classof(const SectionBase *S);
};
Expand Down Expand Up @@ -232,11 +254,11 @@ template <class ELFT> class Object {
typedef typename ELFT::Phdr Elf_Phdr;

void initSymbolTable(const llvm::object::ELFFile<ELFT> &ElfFile,
SymbolTableSection *SymTab);
SymbolTableSection *SymTab, SectionTableRef SecTable);
SecPtr makeSection(const llvm::object::ELFFile<ELFT> &ElfFile,
const Elf_Shdr &Shdr);
void readProgramHeaders(const llvm::object::ELFFile<ELFT> &ElfFile);
void readSectionHeaders(const llvm::object::ELFFile<ELFT> &ElfFile);
SectionTableRef readSectionHeaders(const llvm::object::ELFFile<ELFT> &ElfFile);

SectionBase *getSection(uint16_t Index, llvm::Twine ErrMsg);

Expand Down

0 comments on commit 408651e

Please sign in to comment.