[Courgette] Clean up Disassembler; fix ELF Memory leaks.

courgette/disassembler_elf_32_x86.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "courgette/disassembler_elf_32_x86.h"
 
-#include <stddef.h>
-#include <stdint.h>
-
-#include <algorithm>
-#include <string>
 #include <vector>
 
 #include "base/logging.h"
-
+#include "base/memory/scoped_ptr.h"
 #include "courgette/assembly_program.h"
 #include "courgette/courgette.h"
-#include "courgette/encoded_program.h"
 
 namespace courgette {
 
-DisassemblerElf32X86::DisassemblerElf32X86(const void* start, size_t length)
-  : DisassemblerElf32(start, length) {
+CheckBool DisassemblerElf32X86::TypedRVAX86::ComputeRelativeTarget(
+    const uint8_t* op_pointer) {
+  set_relative_target(Read32LittleEndian(op_pointer) + 4);
+  return true;
 }
 
-// Convert an ELF relocation struction into an RVA
+CheckBool DisassemblerElf32X86::TypedRVAX86::EmitInstruction(
+    AssemblyProgram* program,
+    RVA target_rva) {
+  return program->EmitRel32(program->FindOrMakeRel32Label(target_rva));
+}
+
+uint16_t DisassemblerElf32X86::TypedRVAX86::op_size() const {
+  return 4;
+}
+
+DisassemblerElf32X86::DisassemblerElf32X86(const void* start, size_t length)
+    : DisassemblerElf32(start, length) {
+}
+
+// Convert an ELF relocation struction into an RVA.
 CheckBool DisassemblerElf32X86::RelToRVA(Elf32_Rel rel, RVA* result) const {
+  // The rightmost byte of r_info is the type.
+  elf32_rel_386_type_values type =
+      static_cast<elf32_rel_386_type_values>(rel.r_info & 0xFF);
 
-  // The rightmost byte of r_info is the type...
-  elf32_rel_386_type_values type =
-      (elf32_rel_386_type_values)(unsigned char)rel.r_info;
-
-  // The other 3 bytes of r_info are the symbol
+  // The other 3 bytes of r_info are the symbol.
   uint32_t symbol = rel.r_info >> 8;
 
-  switch(type)
-  {
+  switch(type) {
     case R_386_NONE:
     case R_386_32:
     case R_386_PC32:
     case R_386_GOT32:
     case R_386_PLT32:
     case R_386_COPY:
     case R_386_GLOB_DAT:
     case R_386_JMP_SLOT:
       return false;
 
     case R_386_RELATIVE:
       if (symbol != 0)
         return false;
 
-      // This is a basic ABS32 relocation address
+      // This is a basic ABS32 relocation address.
       *result = rel.r_offset;
       return true;
 
     case R_386_GOTOFF:
     case R_386_GOTPC:
     case R_386_TLS_TPOFF:
       return false;
   }
 
   return false;
 }
 
 CheckBool DisassemblerElf32X86::ParseRelocationSection(
-    const Elf32_Shdr *section_header,
-      AssemblyProgram* program) {
-  // We can reproduce the R_386_RELATIVE entries in one of the relocation
-  // table based on other information in the patch, given these
-  // conditions....
+    const Elf32_Shdr* section_header,
+    AssemblyProgram* program) {
+  // We can reproduce the R_386_RELATIVE entries in one of the relocation table
+  // based on other information in the patch, given these conditions:
   //
   // All R_386_RELATIVE entries are:
   //   1) In the same relocation table
   //   2) Are consecutive
   //   3) Are sorted in memory address order
   //
-  // Happily, this is normally the case, but it's not required by spec
-  // so we check, and just don't do it if we don't match up.
+  // Happily, this is normally the case, but it's not required by spec, so we
+  // check, and just don't do it if we don't match up.
 
-  // The expectation is that one relocation section will contain
-  // all of our R_386_RELATIVE entries in the expected order followed
-  // by assorted other entries we can't use special handling for.
+  // The expectation is that one relocation section will contain all of our
+  // R_386_RELATIVE entries in the expected order followed by assorted other
+  // entries we can't use special handling for.
 
   bool match = true;
 
-  // Walk all the bytes in the section, matching relocation table or not
-  size_t file_offset = section_header->sh_offset;
-  size_t section_end = section_header->sh_offset + section_header->sh_size;
+  // Walk all the bytes in the section, matching relocation table or not.
+  FileOffset file_offset = section_header->sh_offset;
+  FileOffset section_end = file_offset + section_header->sh_size;
 
-  Elf32_Rel *section_relocs_iter =
-      (Elf32_Rel *)OffsetToPointer(section_header->sh_offset);
+  const Elf32_Rel* section_relocs_iter = reinterpret_cast<const Elf32_Rel*>(
+      FileOffsetToPointer(section_header->sh_offset));
 
   uint32_t section_relocs_count =
       section_header->sh_size / section_header->sh_entsize;
 
   if (abs32_locations_.empty())
     match = false;
 
   if (abs32_locations_.size() > section_relocs_count)
     match = false;
 
   std::vector<RVA>::iterator reloc_iter = abs32_locations_.begin();
 
-  while (match && (reloc_iter !=  abs32_locations_.end())) {
+  while (match && (reloc_iter != abs32_locations_.end())) {
     if (section_relocs_iter->r_info != R_386_RELATIVE ||
         section_relocs_iter->r_offset != *reloc_iter)
       match = false;
-    section_relocs_iter++;
-    reloc_iter++;
+    ++section_relocs_iter;
+    ++reloc_iter;
   }
 
   if (match) {
-    // Skip over relocation tables
+    // Skip over relocation tables.
     if (!program->EmitElfRelocationInstruction())
       return false;
     file_offset += sizeof(Elf32_Rel) * abs32_locations_.size();
   }
 
   return ParseSimpleRegion(file_offset, section_end, program);
 }
 
+// TODO(huangs): Detect and avoid overlap with abs32 addresses.
 CheckBool DisassemblerElf32X86::ParseRel32RelocsFromSection(
     const Elf32_Shdr* section_header) {
-  uint32_t start_file_offset = section_header->sh_offset;
-  uint32_t end_file_offset = start_file_offset + section_header->sh_size;
+  FileOffset start_file_offset = section_header->sh_offset;
+  FileOffset end_file_offset = start_file_offset + section_header->sh_size;
 
-  const uint8_t* start_pointer = OffsetToPointer(start_file_offset);
-  const uint8_t* end_pointer = OffsetToPointer(end_file_offset);
+  const uint8_t* start_pointer = FileOffsetToPointer(start_file_offset);
+  const uint8_t* end_pointer = FileOffsetToPointer(end_file_offset);
 
   // Quick way to convert from Pointer to RVA within a single Section is to
-  // subtract 'pointer_to_rva'.
+  // subtract |pointer_to_rva|.
   const uint8_t* const adjust_pointer_to_rva =
       start_pointer - section_header->sh_addr;
 
   // Find the rel32 relocations.
   const uint8_t* p = start_pointer;
   while (p < end_pointer) {
-    //RVA current_rva = static_cast<RVA>(p - adjust_pointer_to_rva);
-
     // Heuristic discovery of rel32 locations in instruction stream: are the
     // next few bytes the start of an instruction containing a rel32
     // addressing mode?
-    const uint8_t* rel32 = NULL;
+    const uint8_t* rel32 = nullptr;
 
     if (p + 5 <= end_pointer) {
       if (*p == 0xE8 || *p == 0xE9) {  // jmp rel32 and call rel32
         rel32 = p + 1;
       }
     }
     if (p + 6 <= end_pointer) {
-      if (*p == 0x0F  &&  (*(p+1) & 0xF0) == 0x80) {  // Jcc long form
+      if (*p == 0x0F && (p[1] & 0xF0) == 0x80) {  // Jcc long form
         if (p[1] != 0x8A && p[1] != 0x8B)  // JPE/JPO unlikely
           rel32 = p + 2;
       }
     }
     if (rel32) {
       RVA rva = static_cast<RVA>(rel32 - adjust_pointer_to_rva);
-      TypedRVAX86* rel32_rva = new TypedRVAX86(rva);
+      scoped_ptr<TypedRVAX86> rel32_rva(new TypedRVAX86(rva));
 
-      if (!rel32_rva->ComputeRelativeTarget(rel32)) {
-        delete rel32_rva;
+      if (!rel32_rva->ComputeRelativeTarget(rel32))
         return false;
-      }
 
       RVA target_rva = rel32_rva->rva() + rel32_rva->relative_target();
-      // To be valid, rel32 target must be within image, and within this
-      // section.
-      if (IsValidRVA(target_rva)) {
-        rel32_locations_.push_back(rel32_rva);
+      if (IsValidTargetRVA(target_rva)) {
+        rel32_locations_.push_back(rel32_rva.release());
 #if COURGETTE_HISTOGRAM_TARGETS
         ++rel32_target_rvas_[target_rva];
 #endif
         p = rel32 + 4;
         continue;
-      } else {
-        delete rel32_rva;
       }
     }
     p += 1;
   }
 
   return true;
 }
 
 }  // namespace courgette