Fixed gdb support and added some ElfFile functions

Fixed gdb support so that it would continue working even when debug
symbols or other sections are included in the elf file. Also made it
actually read parts of the DWARF information so it should work even if
there are minor changes to how and where DWARF information is written
out.

Added a dwarf.h file with the dwarf constants.

Added a FindSectionByName function, a FindDynamicSymbol function, and
the ability to specify the mmap protection and flags directly if we are
mapping in the whole file.

Modified elf_writer_quick.cc to use the dwarf constants from dwarf.h.

Change-Id: I09e15c425fab252b331a2e4719863552e8b6b137

1 files changed, 9 insertions, 33 deletions

diff --git a/compiler/elf_writer_quick.cc b/compiler/elf_writer_quick.cc
index 78757ec..e4dcaa7 100644
--- a/compiler/elf_writer_quick.cc
+++ b/compiler/elf_writer_quick.cc
@@ -20,6 +20,7 @@
 #include "base/unix_file/fd_file.h"
 #include "buffered_output_stream.h"
 #include "driver/compiler_driver.h"
+#include "dwarf.h"
 #include "elf_utils.h"
 #include "file_output_stream.h"
 #include "globals.h"
@@ -469,9 +470,9 @@ bool ElfWriterQuick::ElfBuilder::Write() {
   pieces.push_back(ElfFilePiece(".hash", hash_builder_.section_.sh_offset,
                                 hash.data(), hash.size() * sizeof(Elf32_Word)));
   pieces.push_back(ElfFilePiece(".rodata", rodata_builder_.section_.sh_offset,
-                                NULL, rodata_builder_.section_.sh_size));
+                                nullptr, rodata_builder_.section_.sh_size));
   pieces.push_back(ElfFilePiece(".text", text_builder_.section_.sh_offset,
-                                NULL, text_builder_.section_.sh_size));
+                                nullptr, text_builder_.section_.sh_size));
   if (IncludingDebugSymbols()) {
     pieces.push_back(ElfFilePiece(".symtab", symtab_builder_.section_.sh_offset,
                                   symtab.data(), symtab.size() * sizeof(Elf32_Sym)));
@@ -547,7 +548,7 @@ void ElfWriterQuick::ElfDynamicBuilder::AddDynamicTag(Elf32_Sword tag, Elf32_Wor
   if (tag == DT_NULL) {
     return;
   }
-  dynamics_.push_back({NULL, tag, d_un});
+  dynamics_.push_back({nullptr, tag, d_un});
 }
 
 void ElfWriterQuick::ElfDynamicBuilder::AddDynamicTag(Elf32_Sword tag, Elf32_Word d_un,
@@ -650,7 +651,7 @@ std::vector<Elf32_Word> ElfWriterQuick::ElfSymtabBuilder::GenerateHashContents()
   // Lets say the state is something like this.
   // +--------+       +--------+      +-----------+
   // | symtab |       | bucket |      |   chain   |
-  // |  NULL  |       | 1      |      | STN_UNDEF |
+  // |  nullptr  |       | 1      |      | STN_UNDEF |
   // | <sym1> |       | 4      |      | 2         |
   // | <sym2> |       |        |      | 5         |
   // | <sym3> |       |        |      | STN_UNDEF |
@@ -821,10 +822,10 @@ bool ElfWriterQuick::Write(OatWriter* oat_writer,
 
   bool generateDebugInformation = compiler_driver_->GetCallFrameInformation() != nullptr;
   if (generateDebugInformation) {
-    ElfRawSectionBuilder debug_info(".debug_info",   SHT_PROGBITS, 0, NULL, 0, 1, 0);
-    ElfRawSectionBuilder debug_abbrev(".debug_abbrev", SHT_PROGBITS, 0, NULL, 0, 1, 0);
-    ElfRawSectionBuilder debug_str(".debug_str",    SHT_PROGBITS, 0, NULL, 0, 1, 0);
-    ElfRawSectionBuilder debug_frame(".debug_frame",  SHT_PROGBITS, 0, NULL, 0, 4, 0);
+    ElfRawSectionBuilder debug_info(".debug_info",   SHT_PROGBITS, 0, nullptr, 0, 1, 0);
+    ElfRawSectionBuilder debug_abbrev(".debug_abbrev", SHT_PROGBITS, 0, nullptr, 0, 1, 0);
+    ElfRawSectionBuilder debug_str(".debug_str",    SHT_PROGBITS, 0, nullptr, 0, 1, 0);
+    ElfRawSectionBuilder debug_frame(".debug_frame",  SHT_PROGBITS, 0, nullptr, 0, 4, 0);
     debug_frame.SetBuffer(*compiler_driver_->GetCallFrameInformation());
 
     FillInCFIInformation(oat_writer, debug_info.GetBuffer(),
@@ -866,31 +867,6 @@ static void PushHalf(std::vector<uint8_t>*buf, int data) {
   buf->push_back((data >> 8) & 0xff);
 }
 
-// DWARF constants needed to generate CFI information.
-enum {
-  // Tag encodings.
-  DW_TAG_compile_unit = 0x11,
-  DW_TAG_subprogram = 0X2e,
-
-  // Attribute encodings.
-  DW_AT_name = 0x03,
-  DW_AT_low_pc = 0x11,
-  DW_AT_high_pc = 0x12,
-  DW_AT_language = 0x13,
-
-  // Constant encoding.
-  DW_CHILDREN_no = 0x00,
-  DW_CHILDREN_yes = 0x01,
-
-  // Attribute form encodings.
-  DW_FORM_addr = 0x01,
-  DW_FORM_data1 = 0x0b,
-  DW_FORM_strp = 0x0e,
-
-  // Language encoding.
-  DW_LANG_Java = 0x000b
-};
-
 void ElfWriterQuick::FillInCFIInformation(OatWriter* oat_writer,
                                           std::vector<uint8_t>* dbg_info,
                                           std::vector<uint8_t>* dbg_abbrev,