Reland "[llvm-objcopy] Add support for .dynamic, .dynsym, and .dynstr"
I overzealously landed this before I was sure that another change
wouldn't break the build that this change depends on.
This change adds support for sections involved in dynamic loading such
as SHT_DYNAMIC, SHT_DYNSYM, and allocated string tables.
The two added binaries used for tests can be downloaded here and here
Differential Revision: https://reviews.llvm.org/D36560
llvm-svn: 313767
diff --git a/llvm/tools/llvm-objcopy/Object.cpp b/llvm/tools/llvm-objcopy/Object.cpp
index 16bfdfd..28323f4 100644
--- a/llvm/tools/llvm-objcopy/Object.cpp
+++ b/llvm/tools/llvm-objcopy/Object.cpp
@@ -228,6 +228,12 @@
writeRel(reinterpret_cast<Elf_Rela *>(Buf));
}
+bool SectionWithStrTab::classof(const SectionBase *S) {
+ return isa<DynamicSymbolTableSection>(S) || isa<DynamicSection>(S);
+}
+
+void SectionWithStrTab::finalize() { this->Link = StrTab->Index; }
+
// Returns true IFF a section is wholly inside the range of a segment
static bool sectionWithinSegment(const SectionBase &Section,
const Segment &Segment) {
@@ -308,16 +314,12 @@
SymbolTableSection *SymTab) {
SymTab->Size = 0;
- if (SymbolTable->Link - 1 >= Sections.size())
- error("Symbol table has link index of " + Twine(SymbolTable->Link) +
- " which is not a valid index");
-
- if (auto StrTab =
- dyn_cast<StringTableSection>(Sections[SymbolTable->Link - 1].get()))
- SymTab->setStrTab(StrTab);
- else
- error("Symbol table has link index of " + Twine(SymbolTable->Link) +
- "which is not a string table");
+ 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"));
const Elf_Shdr &Shdr = *unwrapOrError(ElfFile.getSection(SymTab->Index));
StringRef StrTabData = unwrapOrError(ElfFile.getStringTableForSymtab(Shdr));
@@ -325,6 +327,7 @@
for (const auto &Sym : unwrapOrError(ElfFile.symbols(&Shdr))) {
SectionBase *DefSection = nullptr;
StringRef Name = unwrapOrError(Sym.getName(StrTabData));
+
if (Sym.st_shndx >= SHN_LORESERVE) {
if (!isValidReservedSectionIndex(Sym.st_shndx, Machine)) {
error(
@@ -333,12 +336,12 @@
Twine(Sym.st_shndx));
}
} else if (Sym.st_shndx != SHN_UNDEF) {
- if (Sym.st_shndx >= Sections.size())
- error("Symbol '" + Name +
- "' is defined in invalid section with index " +
+ DefSection = getSection(
+ Sym.st_shndx,
+ "Symbol '" + Name + "' is defined in invalid section with index " +
Twine(Sym.st_shndx));
- DefSection = Sections[Sym.st_shndx - 1].get();
}
+
SymTab->addSymbol(Name, Sym.getBinding(), Sym.getType(), DefSection,
Sym.getValue(), Sym.st_shndx, Sym.st_size);
}
@@ -366,6 +369,22 @@
}
template <class ELFT>
+SectionBase *Object<ELFT>::getSection(uint16_t Index, Twine ErrMsg) {
+ if (Index == SHN_UNDEF || Index > Sections.size())
+ error(ErrMsg);
+ return Sections[Index - 1].get();
+}
+
+template <class ELFT>
+template <class T>
+T *Object<ELFT>::getSectionOfType(uint16_t Index, Twine IndexErrMsg,
+ Twine TypeErrMsg) {
+ if (T *TSec = llvm::dyn_cast<T>(getSection(Index, IndexErrMsg)))
+ return TSec;
+ error(TypeErrMsg);
+}
+
+template <class ELFT>
std::unique_ptr<SectionBase>
Object<ELFT>::makeSection(const llvm::object::ELFFile<ELFT> &ElfFile,
const Elf_Shdr &Shdr) {
@@ -375,7 +394,26 @@
case SHT_RELA:
return llvm::make_unique<RelocationSection<ELFT>>();
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 llvm::make_unique<Section>(Data);
+ }
return llvm::make_unique<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 llvm::make_unique<Section>(Data);
+ case SHT_DYNSYM:
+ Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
+ return llvm::make_unique<DynamicSymbolTableSection>(Data);
+ case SHT_DYNAMIC:
+ Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
+ return llvm::make_unique<DynamicSection>(Data);
case SHT_SYMTAB: {
auto SymTab = llvm::make_unique<SymbolTableSectionImpl<ELFT>>();
SymbolTable = SymTab.get();
@@ -423,28 +461,35 @@
// relocation sections.
for (auto &Section : Sections) {
if (auto RelSec = dyn_cast<RelocationSection<ELFT>>(Section.get())) {
- if (RelSec->Link - 1 >= Sections.size() || RelSec->Link == 0) {
- error("Link field value " + Twine(RelSec->Link) + " in section " +
- RelSec->Name + " is invalid");
- }
- if (RelSec->Info - 1 >= Sections.size() || RelSec->Info == 0) {
- error("Info field value " + Twine(RelSec->Link) + " in section " +
- RelSec->Name + " is invalid");
- }
- auto SymTab =
- dyn_cast<SymbolTableSection>(Sections[RelSec->Link - 1].get());
- if (SymTab == nullptr) {
- error("Link field of relocation section " + RelSec->Name +
- " is not a symbol table");
- }
+
+ 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(Sections[RelSec->Info - 1].get());
+
+ 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)));
else
initRelocations(RelSec, SymTab, unwrapOrError(ElfFile.relas(Shdr)));
}
+
+ if (auto Sec = dyn_cast<SectionWithStrTab>(Section.get())) {
+ Sec->setStrTab(getSectionOfType<StringTableSection>(
+ Sec->Link,
+ "Link field value " + Twine(Sec->Link) + " in section " + Sec->Name +
+ " is invalid",
+ "Link field value " + Twine(Sec->Link) + " in section " + Sec->Name +
+ " is not a string table"));
+ }
}
}
@@ -462,8 +507,12 @@
readSectionHeaders(ElfFile);
readProgramHeaders(ElfFile);
- SectionNames =
- dyn_cast<StringTableSection>(Sections[Ehdr.e_shstrndx - 1].get());
+ SectionNames = getSectionOfType<StringTableSection>(
+ Ehdr.e_shstrndx,
+ "e_shstrndx field value " + Twine(Ehdr.e_shstrndx) + " in elf header " +
+ " is invalid",
+ "e_shstrndx field value " + Twine(Ehdr.e_shstrndx) + " in elf header " +
+ " is not a string table");
}
template <class ELFT>