Revert "libelffile: move to DWARF3 when writing .debug_frame."

This reverts commit 546243375d7e129aa02ca7ea9663ed7c40b4880e.

Reason for revert: DWARF-64 is supposed to be used for libraries
over 4GB in size.  It is unrelated to pointer sizes and linked bug.
(the spec explicitly says that it should not be used in our case)

Bug: 192012848
Change-Id: Iaf4679b6d4cb27d049277ef7bdc6606771390a6b

5 files changed, 29 insertions, 83 deletions

diff --git a/compiler/debug/dwarf/dwarf_test.cc b/compiler/debug/dwarf/dwarf_test.cc
index 8fdc7ca63a..8897e45584 100644
--- a/compiler/debug/dwarf/dwarf_test.cc
+++ b/compiler/debug/dwarf/dwarf_test.cc
@@ -131,7 +131,7 @@ TEST_F(DwarfTest, DebugFrame) {
   CheckObjdumpOutput(is64bit, "-debug-frame");
 }
 
-TEST_F(DwarfTest, DebugFrame64) {
+TEST_F(DwarfTest, DISABLED_DebugFrame64) {
   constexpr bool is64bit = true;
   DebugFrameOpCodeWriter<> initial_opcodes;
   WriteCIE(is64bit, Reg(16), initial_opcodes, &debug_frame_data_);
@@ -143,7 +143,7 @@ TEST_F(DwarfTest, DebugFrame64) {
            0x0200000000000000,
            ArrayRef<const uint8_t>(*opcodes.data()),
            &debug_frame_data_);
-  DW_CHECK("FDE cie=00000000 pc=100000000000000...300000000000000");
+  DW_CHECK("FDE cie=00000000 pc=100000000000000..300000000000000");
 
   CheckObjdumpOutput(is64bit, "-debug-frame");
 }
@@ -158,7 +158,7 @@ TEST_F(DwarfTest, x86_64_RegisterMapping) {
     opcodes.RelOffset(Reg::X86_64Core(i), 0);
   }
   DW_CHECK("FDE");
-  DW_CHECK_NEXT("DWARF64");
+  DW_CHECK_NEXT("DWARF32");
   DW_CHECK_NEXT("DW_CFA_nop:");  // TODO: Why is a nop here.
   DW_CHECK_NEXT("DW_CFA_offset: RAX 0");
   DW_CHECK_NEXT("DW_CFA_offset: RCX 0");
diff --git a/compiler/debug/elf_debug_writer.cc b/compiler/debug/elf_debug_writer.cc
index d0ca6db005..765a81d4f8 100644
--- a/compiler/debug/elf_debug_writer.cc
+++ b/compiler/debug/elf_debug_writer.cc
@@ -215,8 +215,8 @@ std::vector<uint8_t> MakeElfFileForJIT(
     reader.VisitDebugFrame([&](const Reader::CIE* cie ATTRIBUTE_UNUSED) {
       num_cies++;
     }, [&](const Reader::FDE* fde, const Reader::CIE* cie ATTRIBUTE_UNUSED) {
-      DCHECK_EQ(fde->sym_addr(), method_info.code_address);
-      DCHECK_EQ(fde->sym_size(), method_info.code_size);
+      DCHECK_EQ(fde->sym_addr, method_info.code_address);
+      DCHECK_EQ(fde->sym_size, method_info.code_size);
       num_fdes++;
     });
     DCHECK_EQ(num_syms, 1u);
@@ -308,8 +308,8 @@ std::vector<uint8_t> PackElfFileForJIT(
         }
       }, [&](const Reader::FDE* fde, const Reader::CIE* cie ATTRIBUTE_UNUSED) {
         DCHECK(copied_cie);
-        DCHECK_EQ(fde->cie_pointer(), 0);
-        if (!is_removed_symbol(fde->sym_addr())) {
+        DCHECK_EQ(fde->cie_pointer, 0);
+        if (!is_removed_symbol(fde->sym_addr)) {
           debug_frame->WriteFully(fde->data(), fde->size());
         }
       });
diff --git a/libelffile/dwarf/headers.h b/libelffile/dwarf/headers.h
index b48d089bc4..d77012ffe3 100644
--- a/libelffile/dwarf/headers.h
+++ b/libelffile/dwarf/headers.h
@@ -46,26 +46,22 @@ void WriteCIE(bool is64bit,
 
   Writer<> writer(buffer);
   size_t cie_header_start_ = writer.data()->size();
-  if (is64bit) {
-    writer.PushUint32(0xFFFFFFFF);
-    writer.PushUint64(0);  // Length placeholder.
-    writer.PushUint64(0xFFFFFFFFFFFFFFFFull);  // CIE id.
-  } else {
-    writer.PushUint32(0);  // Length placeholder.
-    writer.PushUint32(0xFFFFFFFF);  // CIE id.
-  }
-  writer.PushUint8(3);   // Version.
-  writer.PushString("");  // Augmentation.
+  writer.PushUint32(0);  // Length placeholder.
+  writer.PushUint32(0xFFFFFFFF);  // CIE id.
+  writer.PushUint8(1);   // Version.
+  writer.PushString("zR");
   writer.PushUleb128(DebugFrameOpCodeWriter<Vector>::kCodeAlignmentFactor);
   writer.PushSleb128(DebugFrameOpCodeWriter<Vector>::kDataAlignmentFactor);
   writer.PushUleb128(return_address_register.num());  // ubyte in DWARF2.
-  writer.PushData(opcodes.data());
-  writer.Pad(is64bit ? 8 : 4);
+  writer.PushUleb128(1);  // z: Augmentation data size.
   if (is64bit) {
-    writer.UpdateUint64(cie_header_start_ + 4, writer.data()->size() - cie_header_start_ - 12);
+    writer.PushUint8(DW_EH_PE_absptr | DW_EH_PE_udata8);  // R: Pointer encoding.
   } else {
-    writer.UpdateUint32(cie_header_start_, writer.data()->size() - cie_header_start_ - 4);
+    writer.PushUint8(DW_EH_PE_absptr | DW_EH_PE_udata4);  // R: Pointer encoding.
   }
+  writer.PushData(opcodes.data());
+  writer.Pad(is64bit ? 8 : 4);
+  writer.UpdateUint32(cie_header_start_, writer.data()->size() - cie_header_start_ - 4);
 }
 
 // Write frame description entry (FDE) to .debug_frame or .eh_frame section.
@@ -78,27 +74,20 @@ void WriteFDE(bool is64bit,
               /*inout*/ std::vector<uint8_t>* buffer) {
   Writer<> writer(buffer);
   size_t fde_header_start = writer.data()->size();
+  writer.PushUint32(0);  // Length placeholder.
+  writer.PushUint32(cie_pointer);
   // Relocate code_address if it has absolute value.
   if (is64bit) {
-    writer.PushUint32(0xFFFFFFFF);
-    writer.PushUint64(0);  // Length placeholder.
-    writer.PushUint64(cie_pointer);
     writer.PushUint64(code_address);
     writer.PushUint64(code_size);
   } else {
-    writer.PushUint32(0);  // Length placeholder.
-    writer.PushUint32(cie_pointer);
     writer.PushUint32(code_address);
     writer.PushUint32(code_size);
   }
   writer.PushUleb128(0);  // Augmentation data size.
   writer.PushData(opcodes.data(), opcodes.size());
   writer.Pad(is64bit ? 8 : 4);
-  if (is64bit) {
-    writer.UpdateUint64(fde_header_start + 4, writer.data()->size() - fde_header_start - 12);
-  } else {
-    writer.UpdateUint32(fde_header_start, writer.data()->size() - fde_header_start - 4);
-  }
+  writer.UpdateUint32(fde_header_start, writer.data()->size() - fde_header_start - 4);
 }
 
 // Write compilation unit (CU) to .debug_info section.
diff --git a/libelffile/elf/elf_debug_reader.h b/libelffile/elf/elf_debug_reader.h
index 54aade7fe7..266c638473 100644
--- a/libelffile/elf/elf_debug_reader.h
+++ b/libelffile/elf/elf_debug_reader.h
@@ -43,41 +43,11 @@ class ElfDebugReader {
 
   // Call Frame Information.
   struct CFI {
-    const uint8_t* data() const { return reinterpret_cast<const uint8_t*>(this); }
-    const uint32_t* data_u32() const { return reinterpret_cast<const uint32_t*>(this); }
-    uint32_t* data_u32() { return reinterpret_cast<uint32_t*>(this); }
-
-    bool is_64bit() const {
-      return data_u32()[0] == 0xFFFFFFFF;
-    }
-
-    size_t size() const {
-      const uint32_t* s = data_u32();
-      if (is_64bit()) {
-        return 12 + (static_cast<uint64_t>(s[2]) << 32) + s[1];
-      }
-      return 4 + s[0];
-    }
-
-    // Offset in the section or -1 for CIE.
-    int64_t cie_pointer() const {
-      const uint32_t* s = data_u32();
-      if (is_64bit()) {
-        return static_cast<int64_t>((static_cast<uint64_t>(s[4]) << 32) + s[3]);
-      }
-      return static_cast<int32_t>(s[1]);
-    }
-
-    void set_cie_pointer(uint64_t cie_pointer) {
-      uint32_t* s = data_u32();
-      if (is_64bit()) {
-        s[3] = cie_pointer & 0xFFFFFFFF;
-        s[4] = cie_pointer >> 32;
-      } else {
-        s[1] = static_cast<uint32_t>(cie_pointer);
-      }
-    }
+    uint32_t length;  // Length excluding the size of this field.
+    int32_t cie_pointer;  // Offset in the section or -1 for CIE.
 
+    const uint8_t* data() const { return reinterpret_cast<const uint8_t*>(this); }
+    size_t size() const { return sizeof(uint32_t) + length; }
   } PACKED(1);
 
   // Common Information Entry.
@@ -86,21 +56,8 @@ class ElfDebugReader {
 
   // Frame Description Entry.
   struct FDE : public CFI {
-    Elf_Addr sym_addr() const {
-      const uint32_t* s = this->data_u32();
-      if (this->is_64bit()) {
-        return (static_cast<uint64_t>(s[6]) << 32) + s[5];
-      }
-      return s[2];
-    }
-
-    Elf_Addr sym_size() const {
-      const uint32_t* s = this->data_u32();
-      if (this->is_64bit()) {
-        return (static_cast<uint64_t>(s[8]) << 32) + s[7];
-      }
-      return s[3];
-    }
+    Elf_Addr sym_addr;
+    Elf_Addr sym_size;
   } PACKED(1);
 
   explicit ElfDebugReader(ArrayRef<const uint8_t> file) : file_(file) {
@@ -200,11 +157,11 @@ class ElfDebugReader {
       for (size_t offset = 0; offset < debug_frame->sh_size;) {
         const CFI* entry = Read<CFI>(debug_frame->sh_offset + offset);
         DCHECK_LE(entry->size(), debug_frame->sh_size - offset);
-        if (entry->cie_pointer() == -1) {
+        if (entry->cie_pointer == -1) {
           visit_cie(Read<CIE>(debug_frame->sh_offset + offset));
         } else {
           const FDE* fde = Read<FDE>(debug_frame->sh_offset + offset);
-          visit_fde(fde, Read<CIE>(debug_frame->sh_offset + fde->cie_pointer()));
+          visit_fde(fde, Read<CIE>(debug_frame->sh_offset + fde->cie_pointer));
         }
         offset += entry->size();
       }
diff --git a/tools/create_minidebuginfo/create_minidebuginfo.cc b/tools/create_minidebuginfo/create_minidebuginfo.cc
index 14cd6a8619..506661a377 100644
--- a/tools/create_minidebuginfo/create_minidebuginfo.cc
+++ b/tools/create_minidebuginfo/create_minidebuginfo.cc
@@ -122,7 +122,7 @@ static void WriteMinidebugInfo(const std::vector<uint8_t>& input, std::vector<ui
       const FDE* fde = entry.first;
       const CIE* cie = entry.second;
       FDE new_header = *fde;
-      new_header.set_cie_pointer(new_cie_offset[cie]);
+      new_header.cie_pointer = new_cie_offset[cie];
       debug_frame->WriteFully(&new_header, sizeof(FDE));
       debug_frame->WriteFully(fde->data() + sizeof(FDE), fde->size() - sizeof(FDE));
     }