[llvm-objcopy] Add support for dynamic relocations

This change adds support for dynamic relocations (allocated
SHT_REL/SHT_RELA sections with a dynamic symbol table as their link).

The binary I added for the test is here:
https://drive.google.com/file/d/0B3gtIAmiMwZXSjJUZE9pUjd4M0k/view?usp=sharing

Unless support for dynamic symbol tables in yaml2obj is added this is
needed.

Differential Revision: https://reviews.llvm.org/D37915

llvm-svn: 314227

1 files changed, 21 insertions, 26 deletions

diff --git a/llvm/tools/llvm-objcopy/Object.cpp b/llvm/tools/llvm-objcopy/Object.cpp
index a8cd321086b..cb7fddeee77 100644
--- a/llvm/tools/llvm-objcopy/Object.cpp
+++ b/llvm/tools/llvm-objcopy/Object.cpp
@@ -206,22 +206,24 @@ void SymbolTableSectionImpl<ELFT>::writeSection(
   }
 }
 
-template <class ELFT>
-void RelocationSection<ELFT>::initialize(SectionTableRef SecTable) {
-  setSymTab(SecTable.getSectionOfType<SymbolTableSection>(
+template <class SymTabType>
+void RelocationSectionBase<SymTabType>::initialize(SectionTableRef SecTable) {
+  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"));
 
-  setSection(SecTable.getSection(Info,
-                                 "Info field value " + Twine(Info) +
-                                     " in section " + Name + " is invalid"));
+  if (Info != SHN_UNDEF)
+    setSection(SecTable.getSection(Info,
+                                   "Info field value " + Twine(Info) +
+                                       " in section " + Name + " is invalid"));
 }
 
-template <class ELFT> void RelocationSection<ELFT>::finalize() {
+template <class SymTabType> void RelocationSectionBase<SymTabType>::finalize() {
   this->Link = Symbols->Index;
-  this->Info = SecToApplyRel->Index;
+  if (SecToApplyRel != nullptr)
+    this->Info = SecToApplyRel->Index;
 }
 
 template <class ELFT>
@@ -252,6 +254,11 @@ void RelocationSection<ELFT>::writeSection(llvm::FileOutputBuffer &Out) const {
     writeRel(reinterpret_cast<Elf_Rela *>(Buf));
 }
 
+void DynamicRelocationSection::writeSection(llvm::FileOutputBuffer &Out) const {
+  std::copy(std::begin(Contents), std::end(Contents),
+            Out.getBufferStart() + Offset);
+}
+
 bool SectionWithStrTab::classof(const SectionBase *S) {
   return isa<DynamicSymbolTableSection>(S) || isa<DynamicSection>(S);
 }
@@ -401,29 +408,13 @@ SectionBase *SectionTableRef::getSection(uint16_t Index, Twine ErrMsg) {
 
 template <class T>
 T *SectionTableRef::getSectionOfType(uint16_t Index, Twine IndexErrMsg,
-                                  Twine TypeErrMsg) {
+                                     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())
-    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) {
@@ -431,6 +422,10 @@ Object<ELFT>::makeSection(const llvm::object::ELFFile<ELFT> &ElfFile,
   switch (Shdr.sh_type) {
   case SHT_REL:
   case SHT_RELA:
+    if (Shdr.sh_flags & SHF_ALLOC) {
+      Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
+      return llvm::make_unique<DynamicRelocationSection>(Data);
+    }
     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
@@ -517,7 +512,7 @@ SectionTableRef Object<ELFT>::readSectionHeaders(const ELFFile<ELFT> &ElfFile) {
     }
 
     if (auto Sec = dyn_cast<SectionWithStrTab>(Section.get())) {
-      Sec->setStrTab(getSectionOfType<StringTableSection>(
+      Sec->setStrTab(SecTable.getSectionOfType<StringTableSection>(
           Sec->Link,
           "Link field value " + Twine(Sec->Link) + " in section " + Sec->Name +
               " is invalid",