courgette/disassembler_elf_32.cc - chromium/src - Git at Google

 // Copyright 2013 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.h"

 #include <stddef.h>
 #include <stdint.h>

 #include <algorithm>
 #include <string>
 #include <vector>

 #include "base/logging.h"
 #include "base/memory/scoped_vector.h"

 #include "courgette/assembly_program.h"
 #include "courgette/courgette.h"
 #include "courgette/encoded_program.h"

 namespace courgette {

 DisassemblerElf32::DisassemblerElf32(const void* start, size_t length)
   : Disassembler(start, length),
     header_(NULL),
     section_header_table_(NULL),
     section_header_table_size_(0),
     program_header_table_(NULL),
     program_header_table_size_(0),
     default_string_section_(NULL) {
 }

 bool DisassemblerElf32::ParseHeader() {
   if (length() < sizeof(Elf32_Ehdr))
     return Bad("Too small");

   header_ = (Elf32_Ehdr *)start();

   // Have magic for elf header?
   if (header_->e_ident[0] != 0x7f ||
       header_->e_ident[1] != 'E' ||
       header_->e_ident[2] != 'L' ||
       header_->e_ident[3] != 'F')
     return Bad("No Magic Number");

   if (header_->e_type != ET_EXEC &&
       header_->e_type != ET_DYN)
     return Bad("Not an executable file or shared library");

   if (header_->e_machine != ElfEM())
     return Bad("Not a supported architecture");

   if (header_->e_version != 1)
     return Bad("Unknown file version");

   if (header_->e_shentsize != sizeof(Elf32_Shdr))
     return Bad("Unexpected section header size");

   if (!IsArrayInBounds(header_->e_shoff, header_->e_shnum, sizeof(Elf32_Shdr)))
     return Bad("Out of bounds section header table");

   section_header_table_ = (Elf32_Shdr *)OffsetToPointer(header_->e_shoff);
   section_header_table_size_ = header_->e_shnum;

   if (!IsArrayInBounds(header_->e_phoff, header_->e_phnum, sizeof(Elf32_Phdr)))
     return Bad("Out of bounds program header table");

   program_header_table_ = (Elf32_Phdr *)OffsetToPointer(header_->e_phoff);
   program_header_table_size_ = header_->e_phnum;

   if (header_->e_shstrndx >= header_->e_shnum)
     return Bad("Out of bounds string section index");

   default_string_section_ = (const char *)SectionBody((int)header_->e_shstrndx);

   if (!UpdateLength()) {
     return Bad("Out of bounds section or segment");
   }

   return Good();
 }

 bool DisassemblerElf32::Disassemble(AssemblyProgram* target) {
   if (!ok())
     return false;

   // The Image Base is always 0 for ELF Executables
   target->set_image_base(0);

   if (!ParseAbs32Relocs())
     return false;

   if (!ParseRel32RelocsFromSections())
     return false;

   if (!ParseFile(target))
     return false;

   target->DefaultAssignIndexes();

   return true;
 }

 bool DisassemblerElf32::UpdateLength() {
   Elf32_Off result = 0;

   // Find the end of the last section
   for (int section_id = 0; section_id < SectionHeaderCount(); section_id++) {
     const Elf32_Shdr *section_header = SectionHeader(section_id);

     if (section_header->sh_type == SHT_NOBITS)
       continue;

     if (!IsArrayInBounds(section_header->sh_offset, section_header->sh_size, 1))
       return false;

     Elf32_Off section_end = section_header->sh_offset + section_header->sh_size;
     result = std::max(result, section_end);
   }

   // Find the end of the last segment
   for (int i = 0; i < ProgramSegmentHeaderCount(); i++) {
     const Elf32_Phdr *segment_header = ProgramSegmentHeader(i);

     if (!IsArrayInBounds(segment_header->p_offset, segment_header->p_filesz, 1))
       return false;

     Elf32_Off segment_end = segment_header->p_offset + segment_header->p_filesz;
     result = std::max(result, segment_end);
   }

   Elf32_Off section_table_end = header_->e_shoff +
                                 (header_->e_shnum * sizeof(Elf32_Shdr));
   result = std::max(result, section_table_end);

   Elf32_Off segment_table_end = header_->e_phoff +
                                 (header_->e_phnum * sizeof(Elf32_Phdr));
   result = std::max(result, segment_table_end);

   ReduceLength(result);
   return true;
 }

 CheckBool DisassemblerElf32::IsValidRVA(RVA rva) const {
   if (rva == kUnassignedRVA)
     return false;

   // It's valid if it's contained in any program segment
   for (int i = 0; i < ProgramSegmentHeaderCount(); i++) {
     const Elf32_Phdr *segment_header = ProgramSegmentHeader(i);

     if (segment_header->p_type != PT_LOAD)
       continue;

     Elf32_Addr begin = segment_header->p_vaddr;
     Elf32_Addr end = segment_header->p_vaddr + segment_header->p_memsz;

     if (rva >= begin && rva < end)
       return true;
   }

   return false;
 }

 CheckBool DisassemblerElf32::RVAToFileOffset(RVA rva,
                                              size_t* result) const {
   for (int i = 0; i < SectionHeaderCount(); i++) {
     const Elf32_Shdr *section_header = SectionHeader(i);
     // These can appear to have a size in the file, but don't.
     if (section_header->sh_type == SHT_NOBITS)
       continue;
     Elf32_Addr begin = section_header->sh_addr;
     Elf32_Addr end = begin + section_header->sh_size;

     if (rva >= begin && rva < end) {
       *result = section_header->sh_offset + (rva - begin);
       return true;
     }
   }
   return false;
 }

 RVA DisassemblerElf32::FileOffsetToRVA(size_t offset) const {
   // File offsets can be 64 bit values, but we are dealing with 32
   // bit executables and so only need to support 32bit file sizes.
   uint32_t offset32 = (uint32_t)offset;

   for (int i = 0; i < SectionHeaderCount(); i++) {

     const Elf32_Shdr *section_header = SectionHeader(i);

     // These can appear to have a size in the file, but don't.
     if (section_header->sh_type == SHT_NOBITS)
       continue;

     Elf32_Off section_begin = section_header->sh_offset;
     Elf32_Off section_end = section_begin + section_header->sh_size;

     if (offset32 >= section_begin && offset32 < section_end) {
       return section_header->sh_addr + (offset32 - section_begin);
     }
   }

   return 0;
 }

 CheckBool DisassemblerElf32::RVAsToOffsets(std::vector<RVA>* rvas,
                                            std::vector<size_t>* offsets) {
   offsets->clear();

   for (std::vector<RVA>::iterator rva = rvas->begin();
        rva != rvas->end();
        rva++) {

     size_t offset;

     if (!RVAToFileOffset(*rva, &offset))
       return false;

     offsets->push_back(offset);
   }

   return true;
 }

 CheckBool DisassemblerElf32::RVAsToOffsets(ScopedVector<TypedRVA>* rvas) {
   for (ScopedVector<TypedRVA>::iterator rva = rvas->begin();
        rva != rvas->end();
        rva++) {

     size_t offset;

     if (!RVAToFileOffset((*rva)->rva(), &offset))
       return false;

     (*rva)->set_offset(offset);
   }

   return true;
 }

 CheckBool DisassemblerElf32::ParseFile(AssemblyProgram* program) {
   // Walk all the bytes in the file, whether or not in a section.
   uint32_t file_offset = 0;

   std::vector<size_t> abs_offsets;

   if (!RVAsToOffsets(&abs32_locations_, &abs_offsets))
     return false;

   if (!RVAsToOffsets(&rel32_locations_))
     return false;

   std::vector<size_t>::iterator current_abs_offset = abs_offsets.begin();
   ScopedVector<TypedRVA>::iterator current_rel = rel32_locations_.begin();

   std::vector<size_t>::iterator end_abs_offset = abs_offsets.end();
   ScopedVector<TypedRVA>::iterator end_rel = rel32_locations_.end();

   for (int section_id = 0;
        section_id < SectionHeaderCount();
        section_id++) {

     const Elf32_Shdr *section_header = SectionHeader(section_id);

     if (section_header->sh_type == SHT_NOBITS)
       continue;

     if (!ParseSimpleRegion(file_offset,
                            section_header->sh_offset,
                            program))
       return false;
     file_offset = section_header->sh_offset;

     switch (section_header->sh_type) {
       case SHT_REL:
         if (!ParseRelocationSection(section_header, program))
           return false;
         file_offset = section_header->sh_offset + section_header->sh_size;
         break;
       case SHT_PROGBITS:
         if (!ParseProgbitsSection(section_header,
                                   &current_abs_offset, end_abs_offset,
                                   &current_rel, end_rel,
                                   program))
           return false;
         file_offset = section_header->sh_offset + section_header->sh_size;
         break;
       case SHT_INIT_ARRAY:
         // Fall through
       case SHT_FINI_ARRAY:
         while (current_abs_offset != end_abs_offset &&
                *current_abs_offset >= section_header->sh_offset &&
                *current_abs_offset <
                (section_header->sh_offset + section_header->sh_size)) {
           // Skip any abs_offsets appear in the unsupported INIT_ARRAY section
           VLOG(1) << "Skipping relocation entry for unsupported section: " <<
             section_header->sh_type;
           current_abs_offset++;
         }
         break;
       default:
         if (current_abs_offset != end_abs_offset &&
                *current_abs_offset >= section_header->sh_offset &&
                *current_abs_offset <
                (section_header->sh_offset + section_header->sh_size))
           VLOG(1) << "Relocation address in unrecognized ELF section: " << \
             section_header->sh_type;
       break;
     }
   }

   // Rest of the file past the last section
   if (!ParseSimpleRegion(file_offset,
                          length(),
                          program))
     return false;

   // Make certain we consume all of the relocations as expected
   return (current_abs_offset == end_abs_offset);
 }

 CheckBool DisassemblerElf32::ParseProgbitsSection(
     const Elf32_Shdr *section_header,
     std::vector<size_t>::iterator* current_abs_offset,
     std::vector<size_t>::iterator end_abs_offset,
     ScopedVector<TypedRVA>::iterator* current_rel,
     ScopedVector<TypedRVA>::iterator end_rel,
     AssemblyProgram* program) {

   // Walk all the bytes in the file, whether or not in a section.
   size_t file_offset = section_header->sh_offset;
   size_t section_end = section_header->sh_offset + section_header->sh_size;

   Elf32_Addr origin = section_header->sh_addr;
   size_t origin_offset = section_header->sh_offset;
   if (!program->EmitOriginInstruction(origin))
     return false;

   while (file_offset < section_end) {

     if (*current_abs_offset != end_abs_offset &&
         file_offset > **current_abs_offset)
       return false;

     while (*current_rel != end_rel &&
            file_offset > (**current_rel)->get_offset()) {
       (*current_rel)++;
     }

     size_t next_relocation = section_end;

     if (*current_abs_offset != end_abs_offset &&
         next_relocation > **current_abs_offset)
       next_relocation = **current_abs_offset;

     // Rel offsets are heuristically derived, and might (incorrectly) overlap
     // an Abs value, or the end of the section, so +3 to make sure there is
     // room for the full 4 byte value.
     if (*current_rel != end_rel &&
         next_relocation > ((**current_rel)->get_offset() + 3))
       next_relocation = (**current_rel)->get_offset();

     if (next_relocation > file_offset) {
       if (!ParseSimpleRegion(file_offset, next_relocation, program))
         return false;

       file_offset = next_relocation;
       continue;
     }

     if (*current_abs_offset != end_abs_offset &&
         file_offset == **current_abs_offset) {
       const uint8_t* p = OffsetToPointer(file_offset);
       RVA target_rva = Read32LittleEndian(p);

       if (!program->EmitAbs32(program->FindOrMakeAbs32Label(target_rva)))
         return false;
       file_offset += sizeof(RVA);
       (*current_abs_offset)++;
       continue;
     }

     if (*current_rel != end_rel &&
         file_offset == (**current_rel)->get_offset()) {
       uint32_t relative_target = (**current_rel)->relative_target();
       // This cast is for 64 bit systems, and is only safe because we
       // are working on 32 bit executables.
       RVA target_rva = (RVA)(origin + (file_offset - origin_offset) +
                              relative_target);

       if (! (**current_rel)->EmitInstruction(program, target_rva))
         return false;
       file_offset += (**current_rel)->op_size();
       (*current_rel)++;
       continue;
     }
   }

   // Rest of the section (if any)
   return ParseSimpleRegion(file_offset, section_end, program);
 }

 CheckBool DisassemblerElf32::ParseSimpleRegion(
     size_t start_file_offset,
     size_t end_file_offset,
     AssemblyProgram* program) {
   // Callers don't guarantee start < end
   if (start_file_offset >= end_file_offset) return true;

   const size_t len = end_file_offset - start_file_offset;

   if (!program->EmitBytesInstruction(OffsetToPointer(start_file_offset), len))
     return false;

   return true;
 }

 CheckBool DisassemblerElf32::ParseAbs32Relocs() {
   abs32_locations_.clear();

   // Loop through sections for relocation sections
   for (int section_id = 0; section_id < SectionHeaderCount(); section_id++) {
     const Elf32_Shdr *section_header = SectionHeader(section_id);

     if (section_header->sh_type == SHT_REL) {

       Elf32_Rel *relocs_table = (Elf32_Rel *)SectionBody(section_id);

       int relocs_table_count = section_header->sh_size /
                                section_header->sh_entsize;

       // Elf32_Word relocation_section_id = section_header->sh_info;

       // Loop through relocation objects in the relocation section
       for (int rel_id = 0; rel_id < relocs_table_count; rel_id++) {
         RVA rva;

         // Quite a few of these conversions fail, and we simply skip
         // them, that's okay.
         if (RelToRVA(relocs_table[rel_id], &rva) && CheckSection(rva))
           abs32_locations_.push_back(rva);
       }
     }
   }

   std::sort(abs32_locations_.begin(), abs32_locations_.end());
   DCHECK(abs32_locations_.empty() ||
          abs32_locations_.back() != kUnassignedRVA);
   return true;
 }

 CheckBool DisassemblerElf32::CheckSection(RVA rva) {
   size_t offset;

   if (!RVAToFileOffset(rva, &offset)) {
     return false;
   }

   for (int section_id = 0;
        section_id < SectionHeaderCount();
        section_id++) {

     const Elf32_Shdr *section_header = SectionHeader(section_id);

     if (offset >= section_header->sh_offset &&
         offset < (section_header->sh_offset + section_header->sh_size)) {
       switch (section_header->sh_type) {
         case SHT_REL:
           // Fall-through
         case SHT_PROGBITS:
           return true;
       }
     }
   }

   return false;
 }

 CheckBool DisassemblerElf32::ParseRel32RelocsFromSections() {

   rel32_locations_.clear();

   // Loop through sections for relocation sections
   for (int section_id = 0;
        section_id < SectionHeaderCount();
        section_id++) {

     const Elf32_Shdr *section_header = SectionHeader(section_id);

     // Some debug sections can have sh_type=SHT_PROGBITS but sh_addr=0.
     if (section_header->sh_type != SHT_PROGBITS ||
         section_header->sh_addr == 0)
       continue;

     if (!ParseRel32RelocsFromSection(section_header))
       return false;
   }

   std::sort(rel32_locations_.begin(),
             rel32_locations_.end(),
             TypedRVA::IsLessThan);
   DCHECK(rel32_locations_.empty() ||
          rel32_locations_.back()->rva() != kUnassignedRVA);
   return true;
 }

 }  // namespace courgette
	// Copyright 2013 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.h"

	#include <stddef.h>
	#include <stdint.h>

	#include <algorithm>
	#include <string>
	#include <vector>

	#include "base/logging.h"
	#include "base/memory/scoped_vector.h"

	#include "courgette/assembly_program.h"
	#include "courgette/courgette.h"
	#include "courgette/encoded_program.h"

	namespace courgette {

	DisassemblerElf32::DisassemblerElf32(const void* start, size_t length)
	: Disassembler(start, length),
	header_(NULL),
	section_header_table_(NULL),
	section_header_table_size_(0),
	program_header_table_(NULL),
	program_header_table_size_(0),
	default_string_section_(NULL) {
	}

	bool DisassemblerElf32::ParseHeader() {
	if (length() < sizeof(Elf32_Ehdr))
	return Bad("Too small");

	header_ = (Elf32_Ehdr *)start();

	// Have magic for elf header?
	if (header_->e_ident[0] != 0x7f \|\|
	header_->e_ident[1] != 'E' \|\|
	header_->e_ident[2] != 'L' \|\|
	header_->e_ident[3] != 'F')
	return Bad("No Magic Number");

	if (header_->e_type != ET_EXEC &&
	header_->e_type != ET_DYN)
	return Bad("Not an executable file or shared library");

	if (header_->e_machine != ElfEM())
	return Bad("Not a supported architecture");

	if (header_->e_version != 1)
	return Bad("Unknown file version");

	if (header_->e_shentsize != sizeof(Elf32_Shdr))
	return Bad("Unexpected section header size");

	if (!IsArrayInBounds(header_->e_shoff, header_->e_shnum, sizeof(Elf32_Shdr)))
	return Bad("Out of bounds section header table");

	section_header_table_ = (Elf32_Shdr *)OffsetToPointer(header_->e_shoff);
	section_header_table_size_ = header_->e_shnum;

	if (!IsArrayInBounds(header_->e_phoff, header_->e_phnum, sizeof(Elf32_Phdr)))
	return Bad("Out of bounds program header table");

	program_header_table_ = (Elf32_Phdr *)OffsetToPointer(header_->e_phoff);
	program_header_table_size_ = header_->e_phnum;

	if (header_->e_shstrndx >= header_->e_shnum)
	return Bad("Out of bounds string section index");

	default_string_section_ = (const char *)SectionBody((int)header_->e_shstrndx);

	if (!UpdateLength()) {
	return Bad("Out of bounds section or segment");
	}

	return Good();
	}

	bool DisassemblerElf32::Disassemble(AssemblyProgram* target) {
	if (!ok())
	return false;

	// The Image Base is always 0 for ELF Executables
	target->set_image_base(0);

	if (!ParseAbs32Relocs())
	return false;

	if (!ParseRel32RelocsFromSections())
	return false;

	if (!ParseFile(target))
	return false;

	target->DefaultAssignIndexes();

	return true;
	}

	bool DisassemblerElf32::UpdateLength() {
	Elf32_Off result = 0;

	// Find the end of the last section
	for (int section_id = 0; section_id < SectionHeaderCount(); section_id++) {
	const Elf32_Shdr *section_header = SectionHeader(section_id);

	if (section_header->sh_type == SHT_NOBITS)
	continue;

	if (!IsArrayInBounds(section_header->sh_offset, section_header->sh_size, 1))
	return false;

	Elf32_Off section_end = section_header->sh_offset + section_header->sh_size;
	result = std::max(result, section_end);
	}

	// Find the end of the last segment
	for (int i = 0; i < ProgramSegmentHeaderCount(); i++) {
	const Elf32_Phdr *segment_header = ProgramSegmentHeader(i);

	if (!IsArrayInBounds(segment_header->p_offset, segment_header->p_filesz, 1))
	return false;

	Elf32_Off segment_end = segment_header->p_offset + segment_header->p_filesz;
	result = std::max(result, segment_end);
	}

	Elf32_Off section_table_end = header_->e_shoff +
	(header_->e_shnum * sizeof(Elf32_Shdr));
	result = std::max(result, section_table_end);

	Elf32_Off segment_table_end = header_->e_phoff +
	(header_->e_phnum * sizeof(Elf32_Phdr));
	result = std::max(result, segment_table_end);

	ReduceLength(result);
	return true;
	}

	CheckBool DisassemblerElf32::IsValidRVA(RVA rva) const {
	if (rva == kUnassignedRVA)
	return false;

	// It's valid if it's contained in any program segment
	for (int i = 0; i < ProgramSegmentHeaderCount(); i++) {
	const Elf32_Phdr *segment_header = ProgramSegmentHeader(i);

	if (segment_header->p_type != PT_LOAD)
	continue;

	Elf32_Addr begin = segment_header->p_vaddr;
	Elf32_Addr end = segment_header->p_vaddr + segment_header->p_memsz;

	if (rva >= begin && rva < end)
	return true;
	}

	return false;
	}

	CheckBool DisassemblerElf32::RVAToFileOffset(RVA rva,
	size_t* result) const {
	for (int i = 0; i < SectionHeaderCount(); i++) {
	const Elf32_Shdr *section_header = SectionHeader(i);
	// These can appear to have a size in the file, but don't.
	if (section_header->sh_type == SHT_NOBITS)
	continue;
	Elf32_Addr begin = section_header->sh_addr;
	Elf32_Addr end = begin + section_header->sh_size;

	if (rva >= begin && rva < end) {
	*result = section_header->sh_offset + (rva - begin);
	return true;
	}
	}
	return false;
	}

	RVA DisassemblerElf32::FileOffsetToRVA(size_t offset) const {
	// File offsets can be 64 bit values, but we are dealing with 32
	// bit executables and so only need to support 32bit file sizes.
	uint32_t offset32 = (uint32_t)offset;

	for (int i = 0; i < SectionHeaderCount(); i++) {

	const Elf32_Shdr *section_header = SectionHeader(i);

	// These can appear to have a size in the file, but don't.
	if (section_header->sh_type == SHT_NOBITS)
	continue;

	Elf32_Off section_begin = section_header->sh_offset;
	Elf32_Off section_end = section_begin + section_header->sh_size;

	if (offset32 >= section_begin && offset32 < section_end) {
	return section_header->sh_addr + (offset32 - section_begin);
	}
	}

	return 0;
	}

	CheckBool DisassemblerElf32::RVAsToOffsets(std::vector<RVA>* rvas,
	std::vector<size_t>* offsets) {
	offsets->clear();

	for (std::vector<RVA>::iterator rva = rvas->begin();
	rva != rvas->end();
	rva++) {

	size_t offset;

	if (!RVAToFileOffset(*rva, &offset))
	return false;

	offsets->push_back(offset);
	}

	return true;
	}

	CheckBool DisassemblerElf32::RVAsToOffsets(ScopedVector<TypedRVA>* rvas) {
	for (ScopedVector<TypedRVA>::iterator rva = rvas->begin();
	rva != rvas->end();
	rva++) {

	size_t offset;

	if (!RVAToFileOffset((*rva)->rva(), &offset))
	return false;

	(*rva)->set_offset(offset);
	}

	return true;
	}

	CheckBool DisassemblerElf32::ParseFile(AssemblyProgram* program) {
	// Walk all the bytes in the file, whether or not in a section.
	uint32_t file_offset = 0;

	std::vector<size_t> abs_offsets;

	if (!RVAsToOffsets(&abs32_locations_, &abs_offsets))
	return false;

	if (!RVAsToOffsets(&rel32_locations_))
	return false;

	std::vector<size_t>::iterator current_abs_offset = abs_offsets.begin();
	ScopedVector<TypedRVA>::iterator current_rel = rel32_locations_.begin();

	std::vector<size_t>::iterator end_abs_offset = abs_offsets.end();
	ScopedVector<TypedRVA>::iterator end_rel = rel32_locations_.end();

	for (int section_id = 0;
	section_id < SectionHeaderCount();
	section_id++) {

	const Elf32_Shdr *section_header = SectionHeader(section_id);

	if (section_header->sh_type == SHT_NOBITS)
	continue;

	if (!ParseSimpleRegion(file_offset,
	section_header->sh_offset,
	program))
	return false;
	file_offset = section_header->sh_offset;

	switch (section_header->sh_type) {
	case SHT_REL:
	if (!ParseRelocationSection(section_header, program))
	return false;
	file_offset = section_header->sh_offset + section_header->sh_size;
	break;
	case SHT_PROGBITS:
	if (!ParseProgbitsSection(section_header,
	&current_abs_offset, end_abs_offset,
	&current_rel, end_rel,
	program))
	return false;
	file_offset = section_header->sh_offset + section_header->sh_size;
	break;
	case SHT_INIT_ARRAY:
	// Fall through
	case SHT_FINI_ARRAY:
	while (current_abs_offset != end_abs_offset &&
	*current_abs_offset >= section_header->sh_offset &&
	*current_abs_offset <
	(section_header->sh_offset + section_header->sh_size)) {
	// Skip any abs_offsets appear in the unsupported INIT_ARRAY section
	VLOG(1) << "Skipping relocation entry for unsupported section: " <<
	section_header->sh_type;
	current_abs_offset++;
	}
	break;
	default:
	if (current_abs_offset != end_abs_offset &&
	*current_abs_offset >= section_header->sh_offset &&
	*current_abs_offset <
	(section_header->sh_offset + section_header->sh_size))
	VLOG(1) << "Relocation address in unrecognized ELF section: " << \
	section_header->sh_type;
	break;
	}
	}

	// Rest of the file past the last section
	if (!ParseSimpleRegion(file_offset,
	length(),
	program))
	return false;

	// Make certain we consume all of the relocations as expected
	return (current_abs_offset == end_abs_offset);
	}

	CheckBool DisassemblerElf32::ParseProgbitsSection(
	const Elf32_Shdr *section_header,
	std::vector<size_t>::iterator* current_abs_offset,
	std::vector<size_t>::iterator end_abs_offset,
	ScopedVector<TypedRVA>::iterator* current_rel,
	ScopedVector<TypedRVA>::iterator end_rel,
	AssemblyProgram* program) {

	// Walk all the bytes in the file, whether or not in a section.
	size_t file_offset = section_header->sh_offset;
	size_t section_end = section_header->sh_offset + section_header->sh_size;

	Elf32_Addr origin = section_header->sh_addr;
	size_t origin_offset = section_header->sh_offset;
	if (!program->EmitOriginInstruction(origin))
	return false;

	while (file_offset < section_end) {

	if (*current_abs_offset != end_abs_offset &&
	file_offset > **current_abs_offset)
	return false;

	while (*current_rel != end_rel &&
	file_offset > (**current_rel)->get_offset()) {
	(*current_rel)++;
	}

	size_t next_relocation = section_end;

	if (*current_abs_offset != end_abs_offset &&
	next_relocation > **current_abs_offset)
	next_relocation = **current_abs_offset;

	// Rel offsets are heuristically derived, and might (incorrectly) overlap
	// an Abs value, or the end of the section, so +3 to make sure there is
	// room for the full 4 byte value.
	if (*current_rel != end_rel &&
	next_relocation > ((**current_rel)->get_offset() + 3))
	next_relocation = (**current_rel)->get_offset();

	if (next_relocation > file_offset) {
	if (!ParseSimpleRegion(file_offset, next_relocation, program))
	return false;

	file_offset = next_relocation;
	continue;
	}

	if (*current_abs_offset != end_abs_offset &&
	file_offset == **current_abs_offset) {
	const uint8_t* p = OffsetToPointer(file_offset);
	RVA target_rva = Read32LittleEndian(p);

	if (!program->EmitAbs32(program->FindOrMakeAbs32Label(target_rva)))
	return false;
	file_offset += sizeof(RVA);
	(*current_abs_offset)++;
	continue;
	}

	if (*current_rel != end_rel &&
	file_offset == (**current_rel)->get_offset()) {
	uint32_t relative_target = (**current_rel)->relative_target();
	// This cast is for 64 bit systems, and is only safe because we
	// are working on 32 bit executables.
	RVA target_rva = (RVA)(origin + (file_offset - origin_offset) +
	relative_target);

	if (! (**current_rel)->EmitInstruction(program, target_rva))
	return false;
	file_offset += (**current_rel)->op_size();
	(*current_rel)++;
	continue;
	}
	}

	// Rest of the section (if any)
	return ParseSimpleRegion(file_offset, section_end, program);
	}

	CheckBool DisassemblerElf32::ParseSimpleRegion(
	size_t start_file_offset,
	size_t end_file_offset,
	AssemblyProgram* program) {
	// Callers don't guarantee start < end
	if (start_file_offset >= end_file_offset) return true;

	const size_t len = end_file_offset - start_file_offset;

	if (!program->EmitBytesInstruction(OffsetToPointer(start_file_offset), len))
	return false;

	return true;
	}

	CheckBool DisassemblerElf32::ParseAbs32Relocs() {
	abs32_locations_.clear();

	// Loop through sections for relocation sections
	for (int section_id = 0; section_id < SectionHeaderCount(); section_id++) {
	const Elf32_Shdr *section_header = SectionHeader(section_id);

	if (section_header->sh_type == SHT_REL) {

	Elf32_Rel relocs_table = (Elf32_Rel )SectionBody(section_id);

	int relocs_table_count = section_header->sh_size /
	section_header->sh_entsize;

	// Elf32_Word relocation_section_id = section_header->sh_info;

	// Loop through relocation objects in the relocation section
	for (int rel_id = 0; rel_id < relocs_table_count; rel_id++) {
	RVA rva;

	// Quite a few of these conversions fail, and we simply skip
	// them, that's okay.
	if (RelToRVA(relocs_table[rel_id], &rva) && CheckSection(rva))
	abs32_locations_.push_back(rva);
	}
	}
	}

	std::sort(abs32_locations_.begin(), abs32_locations_.end());
	DCHECK(abs32_locations_.empty() \|\|
	abs32_locations_.back() != kUnassignedRVA);
	return true;
	}

	CheckBool DisassemblerElf32::CheckSection(RVA rva) {
	size_t offset;

	if (!RVAToFileOffset(rva, &offset)) {
	return false;
	}

	for (int section_id = 0;
	section_id < SectionHeaderCount();
	section_id++) {

	const Elf32_Shdr *section_header = SectionHeader(section_id);

	if (offset >= section_header->sh_offset &&
	offset < (section_header->sh_offset + section_header->sh_size)) {
	switch (section_header->sh_type) {
	case SHT_REL:
	// Fall-through
	case SHT_PROGBITS:
	return true;
	}
	}
	}

	return false;
	}

	CheckBool DisassemblerElf32::ParseRel32RelocsFromSections() {

	rel32_locations_.clear();

	// Loop through sections for relocation sections
	for (int section_id = 0;
	section_id < SectionHeaderCount();
	section_id++) {

	const Elf32_Shdr *section_header = SectionHeader(section_id);

	// Some debug sections can have sh_type=SHT_PROGBITS but sh_addr=0.
	if (section_header->sh_type != SHT_PROGBITS \|\|
	section_header->sh_addr == 0)
	continue;

	if (!ParseRel32RelocsFromSection(section_header))
	return false;
	}

	std::sort(rel32_locations_.begin(),
	rel32_locations_.end(),
	TypedRVA::IsLessThan);
	DCHECK(rel32_locations_.empty() \|\|
	rel32_locations_.back()->rva() != kUnassignedRVA);
	return true;
	}

	} // namespace courgette