[PATCH] [lld][ELF][Writer] Add dynamic table.

[Michael Spencer]

Hi shankarke,

This adds the dynamic table section and program header.

http://llvm-reviews.chandlerc.com/D427

Files:
  include/lld/ReaderWriter/ELFTargetInfo.h
  lib/ReaderWriter/ELF/HeaderChunks.h
  lib/ReaderWriter/ELF/SectionChunks.h
  lib/ReaderWriter/ELF/Writer.cpp
  lib/ReaderWriter/ELF/X86_64/X86_64TargetHandler.cpp
  test/elf/dynamic-table.test

Index: include/lld/ReaderWriter/ELFTargetInfo.h
===================================================================
--- include/lld/ReaderWriter/ELFTargetInfo.h
+++ include/lld/ReaderWriter/ELFTargetInfo.h
@@ -49,6 +49,12 @@
     return false;
   }
 
+  /// \brief Does the output have dynamic sections.
+  bool isDynamic() const {
+    return _options._outputKind == OutputKind::DynamicExecutable ||
+           _options._outputKind == OutputKind::Shared;
+  }
+
   virtual ErrorOr<Reader &> getReader(const LinkerInput &input) const;
 
   virtual ErrorOr<Writer &> getWriter() const;
Index: lib/ReaderWriter/ELF/HeaderChunks.h
===================================================================
--- lib/ReaderWriter/ELF/HeaderChunks.h
+++ lib/ReaderWriter/ELF/HeaderChunks.h
@@ -182,7 +182,8 @@
   bool allocatedNew = false;
   for (auto slice : segment->slices()) {
     // If we have a TLS segment, emit a LOAD first.
-    if (segment->segmentType() == llvm::ELF::PT_TLS) {
+    if (segment->segmentType() == llvm::ELF::PT_TLS ||
+        segment->segmentType() == llvm::ELF::PT_DYNAMIC) {
       auto phdr = allocateProgramHeader();
       if (phdr.second)
         allocatedNew = true;
@@ -193,7 +194,7 @@
       phdr.first->p_filesz = slice->fileSize();
       phdr.first->p_memsz = slice->memSize();
       phdr.first->p_flags = segment->flags();
-      phdr.first->p_align = slice->align2();
+      phdr.first->p_align = segment->pageSize();
     }
     auto phdr = allocateProgramHeader();
     if (phdr.second)
Index: lib/ReaderWriter/ELF/SectionChunks.h
===================================================================
--- lib/ReaderWriter/ELF/SectionChunks.h
+++ lib/ReaderWriter/ELF/SectionChunks.h
@@ -716,6 +716,48 @@
 private:
   std::vector<std::pair<const DefinedAtom *, const Reference *>> _relocs;
 };
+
+template <class ELFT> class DynamicTable : public Section<ELFT> {
+  typedef llvm::object::Elf_Dyn_Impl<ELFT> Elf_Dyn;
+  typedef std::vector<Elf_Dyn> EntriesT;
+
+public:
+  DynamicTable(const ELFTargetInfo &ti, StringRef str, int32_t order)
+      : Section<ELFT>(ti, str) {
+    this->setOrder(order);
+    this->_entSize = sizeof(Elf_Dyn);
+    this->_align2 = llvm::alignOf<Elf_Dyn>();
+    // Reserve space for the DT_NULL entry.
+    this->_fsize = sizeof(Elf_Dyn);
+    this->_msize = sizeof(Elf_Dyn);
+    this->_type = SHT_DYNAMIC;
+    this->_flags = SHF_ALLOC;
+  }
+
+  range<typename EntriesT::iterator> entries() { return _entries; }
+
+  /// \returns the index of the entry. 
+  std::size_t addEntry(Elf_Dyn e) {
+    _entries.push_back(e);
+    this->_fsize = (_entries.size() * sizeof(Elf_Dyn)) + sizeof(Elf_Dyn);
+    this->_msize = this->_fsize;
+    return _entries.size() - 1;
+  }
+
+  void write(ELFWriter *writer, llvm::FileOutputBuffer &buffer) {
+    uint8_t *chunkBuffer = buffer.getBufferStart();
+    uint8_t *dest = chunkBuffer + this->fileOffset();
+    // Add the null entry.
+    Elf_Dyn d;
+    d.d_tag = 0;
+    d.d_un.d_val = 0;
+    _entries.push_back(d);
+    std::memcpy(dest, _entries.data(), this->_fsize);
+  }
+
+private:
+  EntriesT _entries;
+};
 } // end namespace elf
 } // end namespace lld
 
Index: lib/ReaderWriter/ELF/Writer.cpp
===================================================================
--- lib/ReaderWriter/ELF/Writer.cpp
+++ lib/ReaderWriter/ELF/Writer.cpp
@@ -66,6 +66,10 @@
   LLD_UNIQUE_BUMP_PTR(StringTable<ELFT>) _strtab;
   LLD_UNIQUE_BUMP_PTR(StringTable<ELFT>) _shstrtab;
   LLD_UNIQUE_BUMP_PTR(SectionHeader<ELFT>) _shdrtab;
+  /// \name Dynamic sections.
+  /// @{
+  LLD_UNIQUE_BUMP_PTR(DynamicTable<ELFT>) _dynamicTable;
+  /// @}
   CRuntimeFile<ELFT> _runtimeFile;
 };
 
@@ -330,6 +334,12 @@
   _symtab->setStringSection(_strtab.get());
   _layout->addSection(_shdrtab.get());
 
+  if (_targetInfo.isDynamic()) {
+    _dynamicTable.reset(new (_alloc) DynamicTable<ELFT>(
+        _targetInfo, ".dynamic", DefaultLayout<ELFT>::ORDER_DYNAMIC));
+    _layout->addSection(_dynamicTable.get());
+  }
+
   // give a chance for the target to add sections
   _targetHandler.createDefaultSections();
 }
Index: lib/ReaderWriter/ELF/X86_64/X86_64TargetHandler.cpp
===================================================================
--- lib/ReaderWriter/ELF/X86_64/X86_64TargetHandler.cpp
+++ lib/ReaderWriter/ELF/X86_64/X86_64TargetHandler.cpp
@@ -97,6 +97,7 @@
     break;
   }
   // Runtime only relocations. Ignore here.
+  case R_X86_64_RELATIVE:
   case R_X86_64_IRELATIVE:
     break;
 
Index: test/elf/dynamic-table.test
===================================================================
--- /dev/null
+++ test/elf/dynamic-table.test
@@ -0,0 +1,9 @@
+RUN: lld -core -target x86_64-linux %p/Inputs/use-shared.x86-64 \
+RUN:   %p/Inputs/shared.so-x86-64 -output=%t -entry=main \
+RUN:   -output-type=dynamic
+RUN: llvm-readobj %t | FileCheck %s
+
+CHECK: Dynamic section contains 1 entries
+CHECK:   Tag                Type                 Name/Value
+CHECK:  0x0000000000000000 (NULL)               0x0
+CHECK:   Total: 1
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