Revert "Add dwarf5 compilation-unit header handling."

This reverts commit dbd454dbe4.

Reason for revert: The parent CL is causing breakage on CrOS due to
unhandled enums.  Before we can revert that, we need to revert this.

Bug: google-breakpad:812
Change-Id: I7c2446f3cd8ed9f6411e90dbdd2434bc463b2f6c
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/2095798
Reviewed-by: Mark Mentovai <mark@chromium.org>

src/common/dwarf/dwarf2enums.h

@@ -686,7 +686,7 @@ enum DwarfLanguage
     DW_LANG_ObjC_plus_plus           =0x0011,
     DW_LANG_UPC                      =0x0012,
     DW_LANG_D                        =0x0013,
-    DW_LANG_Python                   =0x0014,
+    DW_LANG__Python                  =0x0014,
     DW_LANG_OpenCL                   =0x0015,
     DW_LANG_Go                       =0x0016,
     DW_LANG_Modula3                  =0x0017,

src/common/dwarf/dwarf2reader.cc

@@ -243,51 +243,11 @@ const uint8_t *CompilationUnit::SkipAttribute(const uint8_t *start,
   return NULL;
 }
 
-// Read the abbreviation offset from a compilation unit header.
+// Read a DWARF2/3 header.
-int CompilationUnit::ReadAbbrevOffset(const uint8_t *headerptr) {
+// The header is variable length in DWARF3 (and DWARF2 as extended by
-  assert(headerptr + reader_->OffsetSize() < buffer_ + buffer_length_);
-  header_.abbrev_offset = reader_->ReadOffset(headerptr);
-  return reader_->OffsetSize();
-}
-
-// Read the address size from a compilation unit header.
-int CompilationUnit::ReadAddressSize(const uint8_t *headerptr) {
-  // Compare against less than or equal because this may be the last
-  // section in the file.
-  assert(headerptr + 1 <= buffer_ + buffer_length_);
-  header_.address_size = reader_->ReadOneByte(headerptr);
-  reader_->SetAddressSize(header_.address_size);
-  return 1;
-}
-
-// Read the DWO id from a split or skeleton compilation unit header.
-int CompilationUnit::ReadDwoId(const uint8_t *headerptr) {
-  assert(headerptr + 8 <= buffer_ + buffer_length_);
-  dwo_id_ = reader_->ReadEightBytes(headerptr);
-  return 8;
-}
-
-// Read the type signature from a type or split type compilation unit header.
-int CompilationUnit::ReadTypeSignature(const uint8_t *headerptr) {
-  assert(headerptr + 8 <= buffer_ + buffer_length_);
-  type_signature_ = reader_->ReadEightBytes(headerptr);
-  return 8;
-}
-
-// Read the DWO id from a split or skeleton compilation unit header.
-int CompilationUnit::ReadTypeOffset(const uint8_t *headerptr) {
-  assert(headerptr + reader_->OffsetSize() < buffer_ + buffer_length_);
-  type_offset_ = reader_->ReadOffset(headerptr);
-  return reader_->OffsetSize();
-}
-
-
-// Read a DWARF header.
-// The header is variable length in DWARF3 and DWARF4 (and DWARF2 as extended by
 // most compilers), and consists of an length field, a version number,
 // the offset in the .debug_abbrev section for our abbrevs, and an
-// address size. DWARF5 adds a unit_type to distinguish between
+// address size.
-// partial-, full-, skeleton-, split-, and type- compilation units.
 void CompilationUnit::ReadHeader() {
   const uint8_t *headerptr = buffer_;
   size_t initial_length_size;
@@ -302,33 +262,17 @@ void CompilationUnit::ReadHeader() {
   header_.version = reader_->ReadTwoBytes(headerptr);
   headerptr += 2;
 
-  if (header_.version <= 4) {
+  assert(headerptr + reader_->OffsetSize() < buffer_ + buffer_length_);
-    // Older versions of dwarf have a relatively simple structure.
+  header_.abbrev_offset = reader_->ReadOffset(headerptr);
-    headerptr += ReadAbbrevOffset(headerptr);
+  headerptr += reader_->OffsetSize();
-    headerptr += ReadAddressSize(headerptr);
+
-  } else {
+  // Compare against less than or equal because this may be the last
-    // DWARF5 adds a unit_type field, and various fields based on unit_type.
+  // section in the file.
-    assert(headerptr + 1 < buffer_ + buffer_length_);
+  assert(headerptr + 1 <= buffer_ + buffer_length_);
-    int unit_type = reader_->ReadOneByte(headerptr);
+  header_.address_size = reader_->ReadOneByte(headerptr);
+  reader_->SetAddressSize(header_.address_size);
   headerptr += 1;
-    headerptr += ReadAddressSize(headerptr);
+
-    headerptr += ReadAbbrevOffset(headerptr);
-    switch (unit_type) {
-      case DW_UT_compile:
-      case DW_UT_partial:
-        // nothing else to read
-        break;
-      case DW_UT_skeleton:
-      case DW_UT_split_compile:
-        headerptr += ReadDwoId(headerptr);;
-        break;
-      case DW_UT_type:
-      case DW_UT_split_type:
-        headerptr += ReadTypeSignature(headerptr);;
-        headerptr += ReadTypeOffset(headerptr);;
-        break;
-    }
-  }
   after_header_ = headerptr;
 
   // This check ensures that we don't have to do checking during the

src/common/dwarf/dwarf2reader.h

@@ -410,21 +410,6 @@ class CompilationUnit {
   // Reads the DWARF2/3 abbreviations for this compilation unit
   void ReadAbbrevs();
 
-  // Read the abbreviation offset for this compilation unit
-  int ReadAbbrevOffset(const uint8_t *headerptr);
-
-  // Read the address size for this compilation unit
-  int ReadAddressSize(const uint8_t *headerptr);
-
-  // Read the DWO id from a split or skeleton compilation unit header
-  int ReadDwoId(const uint8_t *headerptr);
-
-  // Read the type signature from a type or split type compilation unit header
-  int ReadTypeSignature(const uint8_t *headerptr);
-
-  // Read the DWO id from a split or skeleton compilation unit header
-  int ReadTypeOffset(const uint8_t *headerptr);
-
   // Processes a single DIE for this compilation unit and return a new
   // pointer just past the end of it
   const uint8_t *ProcessDIE(uint64 dieoffset,
@@ -579,12 +564,6 @@ class CompilationUnit {
   // The value of the DW_AT_GNU_dwo_id attribute, if any.
   uint64 dwo_id_;
 
-  // The value of the DW_AT_GNU_type_signature attribute, if any.
-  uint64 type_signature_;
-
-  // The value of the DW_AT_GNU_type_offset attribute, if any.
-  size_t type_offset_;
-
   // The value of the DW_AT_GNU_dwo_name attribute, if any.
   const char* dwo_name_;
 

src/common/dwarf/dwarf2reader_die_unittest.cc

@@ -217,8 +217,6 @@ INSTANTIATE_TEST_CASE_P(
                       DwarfHeaderParams(kLittleEndian, 8, 3, 8),
                       DwarfHeaderParams(kLittleEndian, 8, 4, 4),
                       DwarfHeaderParams(kLittleEndian, 8, 4, 8),
-                      DwarfHeaderParams(kLittleEndian, 8, 5, 4),
-                      DwarfHeaderParams(kLittleEndian, 8, 5, 8),
                       DwarfHeaderParams(kBigEndian,    4, 2, 4),
                       DwarfHeaderParams(kBigEndian,    4, 2, 8),
                       DwarfHeaderParams(kBigEndian,    4, 3, 4),
@@ -230,9 +228,7 @@ INSTANTIATE_TEST_CASE_P(
                       DwarfHeaderParams(kBigEndian,    8, 3, 4),
                       DwarfHeaderParams(kBigEndian,    8, 3, 8),
                       DwarfHeaderParams(kBigEndian,    8, 4, 4),
-                      DwarfHeaderParams(kBigEndian,    8, 4, 8),
+                      DwarfHeaderParams(kBigEndian,    8, 4, 8)));
-                      DwarfHeaderParams(kBigEndian,    8, 5, 4),
-                      DwarfHeaderParams(kBigEndian,    8, 5, 8)));
 
 struct DwarfFormsFixture: public DIEFixture {
   // Start a compilation unit, as directed by |params|, containing one

src/common/dwarf/dwarf2reader_test_common.h

@@ -80,14 +80,8 @@ class TestCompilationUnit: public google_breakpad::test_assembler::Section {
     }
     post_length_offset_ = Size();
     D16(version);
-    if (version <= 4) {
     SectionOffset(abbrev_offset);
     D8(address_size);
-    } else {
-      D8(0x01);  // DW_UT_compile
-      D8(address_size);
-      SectionOffset(abbrev_offset);
-    }
     return *this;
   }