3 files changed, 60 insertions, 1 deletions

diff --git a/lld/lib/ReaderWriter/ELF/DefaultLayout.h b/lld/lib/ReaderWriter/ELF/DefaultLayout.h
index 85420c4bf23..c980c533aca 100644
--- a/lld/lib/ReaderWriter/ELF/DefaultLayout.h
+++ b/lld/lib/ReaderWriter/ELF/DefaultLayout.h
@@ -439,7 +439,6 @@ Layout::SegmentType DefaultLayout<ELFT>::getSegmentType(
   case ORDER_FINI:
   case ORDER_RODATA:
   case ORDER_EH_FRAME:
-  case ORDER_EH_FRAMEHDR:
     return llvm::ELF::PT_LOAD;
 
   case ORDER_RO_NOTE:
@@ -453,6 +452,9 @@ Layout::SegmentType DefaultLayout<ELFT>::getSegmentType(
   case ORDER_DTORS:
     return llvm::ELF::PT_GNU_RELRO;
 
+  case ORDER_EH_FRAMEHDR:
+    return llvm::ELF::PT_GNU_EH_FRAME;
+
   case ORDER_GOT:
   case ORDER_GOT_PLT:
   case ORDER_DATA:
diff --git a/lld/lib/ReaderWriter/ELF/OutputELFWriter.h b/lld/lib/ReaderWriter/ELF/OutputELFWriter.h
index cc044002c4f..d8319da09df 100644
--- a/lld/lib/ReaderWriter/ELF/OutputELFWriter.h
+++ b/lld/lib/ReaderWriter/ELF/OutputELFWriter.h
@@ -105,6 +105,7 @@ protected:
   LLD_UNIQUE_BUMP_PTR(StringTable<ELFT>) _strtab;
   LLD_UNIQUE_BUMP_PTR(StringTable<ELFT>) _shstrtab;
   LLD_UNIQUE_BUMP_PTR(SectionHeader<ELFT>) _shdrtab;
+  LLD_UNIQUE_BUMP_PTR(EHFrameHeader<ELFT>) _ehFrameHeader;
   /// \name Dynamic sections.
   /// @{
   LLD_UNIQUE_BUMP_PTR(DynamicTable<ELFT>) _dynamicTable;
@@ -267,6 +268,15 @@ template <class ELFT> void OutputELFWriter<ELFT>::createDefaultSections() {
   _symtab->setStringSection(_strtab.get());
   _layout->addSection(_shdrtab.get());
 
+  for (auto sec : _layout->sections()) {
+    if (sec->name() != ".eh_frame")
+      continue;
+    _ehFrameHeader.reset(new (_alloc) EHFrameHeader<ELFT>(
+        _context, ".eh_frame_hdr", DefaultLayout<ELFT>::ORDER_EH_FRAMEHDR));
+    _layout->addSection(_ehFrameHeader.get());
+    break;
+  }
+
   if (_context.isDynamic()) {
     _dynamicTable.reset(new (_alloc) DynamicTable<ELFT>(
         _context, ".dynamic", DefaultLayout<ELFT>::ORDER_DYNAMIC));
diff --git a/lld/lib/ReaderWriter/ELF/SectionChunks.h b/lld/lib/ReaderWriter/ELF/SectionChunks.h
index 2e61ad33b1b..a6bc9478b87 100644
--- a/lld/lib/ReaderWriter/ELF/SectionChunks.h
+++ b/lld/lib/ReaderWriter/ELF/SectionChunks.h
@@ -26,6 +26,7 @@
 #include "llvm/Object/ELF.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/Dwarf.h"
 #include "llvm/Support/ELF.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileOutputBuffer.h"
@@ -1284,6 +1285,52 @@ private:
   std::vector<uint32_t> _chains;
   const DynamicSymbolTable<ELFT> *_symbolTable;
 };
+
+template <class ELFT> class EHFrameHeader : public Section<ELFT> {
+public:
+  EHFrameHeader(const ELFLinkingContext &context, StringRef name, int32_t order)
+      : Section<ELFT>(context, name) {
+    this->setOrder(order);
+    this->_entSize = 0;
+    this->_type = SHT_PROGBITS;
+    this->_flags = SHF_ALLOC;
+    // Set the alignment properly depending on the target architecture
+    if (context.is64Bits())
+      this->_align2 = 8;
+    else
+      this->_align2 = 4;
+    // Minimum size for empty .eh_frame_hdr.
+    this->_fsize = 1 + 1 + 1 + 1 + 4;
+    this->_msize = this->_fsize;
+  }
+
+  virtual void doPreFlight() LLVM_OVERRIDE {
+    // TODO: Generate a proper binary search table.
+  }
+
+  virtual void finalize() LLVM_OVERRIDE {
+    MergedSections<ELFT> *s = this->_context.template getTargetHandler<ELFT>()
+                                  .targetLayout()
+                                  .findOutputSection(".eh_frame");
+    _ehFrameAddr = s ? s->virtualAddr() : 0;
+  }
+
+  virtual void write(ELFWriter *writer,
+                     llvm::FileOutputBuffer &buffer) LLVM_OVERRIDE {
+    uint8_t *chunkBuffer = buffer.getBufferStart();
+    uint8_t *dest = chunkBuffer + this->fileOffset();
+    int pos = 0;
+    dest[pos++] = 1; // version
+    dest[pos++] = llvm::dwarf::DW_EH_PE_udata4; // eh_frame_ptr_enc
+    dest[pos++] = llvm::dwarf::DW_EH_PE_omit; // fde_count_enc
+    dest[pos++] = llvm::dwarf::DW_EH_PE_omit; // table_enc
+    *reinterpret_cast<typename llvm::object::ELFFile<ELFT>::Elf_Word *>(
+         dest + pos) = (uint32_t)_ehFrameAddr;
+  }
+
+private:
+  uint64_t _ehFrameAddr;
+};
 } // end namespace elf
 } // end namespace lld