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Diffstat (limited to 'courgette/disassembler_win32_x64.cc')
| -rw-r--r-- | courgette/disassembler_win32_x64.cc | 732 |
1 files changed, 732 insertions, 0 deletions
diff --git a/courgette/disassembler_win32_x64.cc b/courgette/disassembler_win32_x64.cc new file mode 100644 index 0000000..1da5951 --- /dev/null +++ b/courgette/disassembler_win32_x64.cc @@ -0,0 +1,732 @@ +// 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_win32_x64.h" + +#include <algorithm> +#include <string> +#include <vector> + +#include "base/basictypes.h" +#include "base/logging.h" + +#include "courgette/assembly_program.h" +#include "courgette/courgette.h" +#include "courgette/encoded_program.h" + +namespace courgette { + +DisassemblerWin32X64::DisassemblerWin32X64(const void* start, size_t length) + : Disassembler(start, length), + incomplete_disassembly_(false), + is_PE32_plus_(false), + optional_header_(NULL), + size_of_optional_header_(0), + offset_of_data_directories_(0), + machine_type_(0), + number_of_sections_(0), + sections_(NULL), + has_text_section_(false), + size_of_code_(0), + size_of_initialized_data_(0), + size_of_uninitialized_data_(0), + base_of_code_(0), + base_of_data_(0), + image_base_(0), + size_of_image_(0), + number_of_data_directories_(0) { +} + +// ParseHeader attempts to match up the buffer with the Windows data +// structures that exist within a Windows 'Portable Executable' format file. +// Returns 'true' if the buffer matches, and 'false' if the data looks +// suspicious. Rather than try to 'map' the buffer to the numerous windows +// structures, we extract the information we need into the courgette::PEInfo +// structure. +// +bool DisassemblerWin32X64::ParseHeader() { + if (length() < kOffsetOfFileAddressOfNewExeHeader + 4 /*size*/) + return Bad("Too small"); + + // Have 'MZ' magic for a DOS header? + if (start()[0] != 'M' || start()[1] != 'Z') + return Bad("Not MZ"); + + // offset from DOS header to PE header is stored in DOS header. + uint32 offset = ReadU32(start(), + kOffsetOfFileAddressOfNewExeHeader); + + if (offset >= length()) + return Bad("Bad offset to PE header"); + + const uint8* const pe_header = OffsetToPointer(offset); + const size_t kMinPEHeaderSize = 4 /*signature*/ + kSizeOfCoffHeader; + if (pe_header <= start() || + pe_header >= end() - kMinPEHeaderSize) + return Bad("Bad offset to PE header"); + + if (offset % 8 != 0) + return Bad("Misaligned PE header"); + + // The 'PE' header is an IMAGE_NT_HEADERS structure as defined in WINNT.H. + // See http://msdn.microsoft.com/en-us/library/ms680336(VS.85).aspx + // + // The first field of the IMAGE_NT_HEADERS is the signature. + if (!(pe_header[0] == 'P' && + pe_header[1] == 'E' && + pe_header[2] == 0 && + pe_header[3] == 0)) + return Bad("no PE signature"); + + // The second field of the IMAGE_NT_HEADERS is the COFF header. + // The COFF header is also called an IMAGE_FILE_HEADER + // http://msdn.microsoft.com/en-us/library/ms680313(VS.85).aspx + const uint8* const coff_header = pe_header + 4; + machine_type_ = ReadU16(coff_header, 0); + number_of_sections_ = ReadU16(coff_header, 2); + size_of_optional_header_ = ReadU16(coff_header, 16); + + // The rest of the IMAGE_NT_HEADERS is the IMAGE_OPTIONAL_HEADER(32|64) + const uint8* const optional_header = coff_header + kSizeOfCoffHeader; + optional_header_ = optional_header; + + if (optional_header + size_of_optional_header_ >= end()) + return Bad("optional header past end of file"); + + // Check we can read the magic. + if (size_of_optional_header_ < 2) + return Bad("optional header no magic"); + + uint16 magic = ReadU16(optional_header, 0); + + if (magic == kImageNtOptionalHdr32Magic) { + is_PE32_plus_ = false; + offset_of_data_directories_ = + kOffsetOfDataDirectoryFromImageOptionalHeader32; + } else if (magic == kImageNtOptionalHdr64Magic) { + is_PE32_plus_ = true; + offset_of_data_directories_ = + kOffsetOfDataDirectoryFromImageOptionalHeader64; + } else { + return Bad("unrecognized magic"); + } + + // Check that we can read the rest of the the fixed fields. Data directories + // directly follow the fixed fields of the IMAGE_OPTIONAL_HEADER. + if (size_of_optional_header_ < offset_of_data_directories_) + return Bad("optional header too short"); + + // The optional header is either an IMAGE_OPTIONAL_HEADER32 or + // IMAGE_OPTIONAL_HEADER64 + // http://msdn.microsoft.com/en-us/library/ms680339(VS.85).aspx + // + // Copy the fields we care about. + size_of_code_ = ReadU32(optional_header, 4); + size_of_initialized_data_ = ReadU32(optional_header, 8); + size_of_uninitialized_data_ = ReadU32(optional_header, 12); + base_of_code_ = ReadU32(optional_header, 20); + if (is_PE32_plus_) { + base_of_data_ = 0; + image_base_ = ReadU64(optional_header, 24); + } else { + base_of_data_ = ReadU32(optional_header, 24); + image_base_ = ReadU32(optional_header, 28); + } + size_of_image_ = ReadU32(optional_header, 56); + number_of_data_directories_ = + ReadU32(optional_header, (is_PE32_plus_ ? 108 : 92)); + + if (size_of_code_ >= length() || + size_of_initialized_data_ >= length() || + size_of_code_ + size_of_initialized_data_ >= length()) { + // This validation fires on some perfectly fine executables. + // return Bad("code or initialized data too big"); + } + + // TODO(sra): we can probably get rid of most of the data directories. + bool b = true; + // 'b &= ...' could be short circuit 'b = b && ...' but it is not necessary + // for correctness and it compiles smaller this way. + b &= ReadDataDirectory(0, &export_table_); + b &= ReadDataDirectory(1, &import_table_); + b &= ReadDataDirectory(2, &resource_table_); + b &= ReadDataDirectory(3, &exception_table_); + b &= ReadDataDirectory(5, &base_relocation_table_); + b &= ReadDataDirectory(11, &bound_import_table_); + b &= ReadDataDirectory(12, &import_address_table_); + b &= ReadDataDirectory(13, &delay_import_descriptor_); + b &= ReadDataDirectory(14, &clr_runtime_header_); + if (!b) { + return Bad("malformed data directory"); + } + + // Sections follow the optional header. + sections_ = + reinterpret_cast<const Section*>(optional_header + + size_of_optional_header_); + size_t detected_length = 0; + + for (int i = 0; i < number_of_sections_; ++i) { + const Section* section = §ions_[i]; + + // TODO(sra): consider using the 'characteristics' field of the section + // header to see if the section contains instructions. + if (memcmp(section->name, ".text", 6) == 0) + has_text_section_ = true; + + uint32 section_end = + section->file_offset_of_raw_data + section->size_of_raw_data; + if (section_end > detected_length) + detected_length = section_end; + } + + // Pretend our in-memory copy is only as long as our detected length. + ReduceLength(detected_length); + + if (is_32bit()) { + return Bad("32 bit executables are not supported by this disassembler"); + } + + if (!has_text_section()) { + return Bad("Resource-only executables are not yet supported"); + } + + return Good(); +} + +bool DisassemblerWin32X64::Disassemble(AssemblyProgram* target) { + if (!ok()) + return false; + + target->set_image_base(image_base()); + + if (!ParseAbs32Relocs()) + return false; + + ParseRel32RelocsFromSections(); + + if (!ParseFile(target)) + return false; + + target->DefaultAssignIndexes(); + + return true; +} + +//////////////////////////////////////////////////////////////////////////////// + +bool DisassemblerWin32X64::ParseRelocs(std::vector<RVA> *relocs) { + relocs->clear(); + + size_t relocs_size = base_relocation_table_.size_; + if (relocs_size == 0) + return true; + + // The format of the base relocation table is a sequence of variable sized + // IMAGE_BASE_RELOCATION blocks. Search for + // "The format of the base relocation data is somewhat quirky" + // at http://msdn.microsoft.com/en-us/library/ms809762.aspx + + const uint8* relocs_start = RVAToPointer(base_relocation_table_.address_); + const uint8* relocs_end = relocs_start + relocs_size; + + // Make sure entire base relocation table is within the buffer. + if (relocs_start < start() || + relocs_start >= end() || + relocs_end <= start() || + relocs_end > end()) { + return Bad(".relocs outside image"); + } + + const uint8* block = relocs_start; + + // Walk the variable sized blocks. + while (block + 8 < relocs_end) { + RVA page_rva = ReadU32(block, 0); + uint32 size = ReadU32(block, 4); + if (size < 8 || // Size includes header ... + size % 4 != 0) // ... and is word aligned. + return Bad("unreasonable relocs block"); + + const uint8* end_entries = block + size; + + if (end_entries <= block || + end_entries <= start() || + end_entries > end()) + return Bad(".relocs block outside image"); + + // Walk through the two-byte entries. + for (const uint8* p = block + 8; p < end_entries; p += 2) { + uint16 entry = ReadU16(p, 0); + int type = entry >> 12; + int offset = entry & 0xFFF; + + RVA rva = page_rva + offset; + if (type == 10) { // IMAGE_REL_BASED_DIR64 + relocs->push_back(rva); + } else if (type == 0) { // IMAGE_REL_BASED_ABSOLUTE + // Ignore, used as padding. + } else { + // Does not occur in Windows x64 executables. + return Bad("unknown type of reloc"); + } + } + + block += size; + } + + std::sort(relocs->begin(), relocs->end()); + + return true; +} + +const Section* DisassemblerWin32X64::RVAToSection(RVA rva) const { + for (int i = 0; i < number_of_sections_; i++) { + const Section* section = §ions_[i]; + uint32 offset = rva - section->virtual_address; + if (offset < section->virtual_size) { + return section; + } + } + return NULL; +} + +int DisassemblerWin32X64::RVAToFileOffset(RVA rva) const { + const Section* section = RVAToSection(rva); + if (section) { + uint32 offset = rva - section->virtual_address; + if (offset < section->size_of_raw_data) { + return section->file_offset_of_raw_data + offset; + } else { + return kNoOffset; // In section but not in file (e.g. uninit data). + } + } + + // Small RVA values point into the file header in the loaded image. + // RVA 0 is the module load address which Windows uses as the module handle. + // RVA 2 sometimes occurs, I'm not sure what it is, but it would map into the + // DOS header. + if (rva == 0 || rva == 2) + return rva; + + NOTREACHED(); + return kNoOffset; +} + +const uint8* DisassemblerWin32X64::RVAToPointer(RVA rva) const { + int file_offset = RVAToFileOffset(rva); + if (file_offset == kNoOffset) + return NULL; + else + return OffsetToPointer(file_offset); +} + +std::string DisassemblerWin32X64::SectionName(const Section* section) { + if (section == NULL) + return "<none>"; + char name[9]; + memcpy(name, section->name, 8); + name[8] = '\0'; // Ensure termination. + return name; +} + +CheckBool DisassemblerWin32X64::ParseFile(AssemblyProgram* program) { + // Walk all the bytes in the file, whether or not in a section. + uint32 file_offset = 0; + while (file_offset < length()) { + const Section* section = FindNextSection(file_offset); + if (section == NULL) { + // No more sections. There should not be extra stuff following last + // section. + // ParseNonSectionFileRegion(file_offset, pe_info().length(), program); + break; + } + if (file_offset < section->file_offset_of_raw_data) { + uint32 section_start_offset = section->file_offset_of_raw_data; + if(!ParseNonSectionFileRegion(file_offset, section_start_offset, + program)) + return false; + + file_offset = section_start_offset; + } + uint32 end = file_offset + section->size_of_raw_data; + if (!ParseFileRegion(section, file_offset, end, program)) + return false; + file_offset = end; + } + +#if COURGETTE_HISTOGRAM_TARGETS + HistogramTargets("abs32 relocs", abs32_target_rvas_); + HistogramTargets("rel32 relocs", rel32_target_rvas_); +#endif + + return true; +} + +bool DisassemblerWin32X64::ParseAbs32Relocs() { + abs32_locations_.clear(); + if (!ParseRelocs(&abs32_locations_)) + return false; + + std::sort(abs32_locations_.begin(), abs32_locations_.end()); + +#if COURGETTE_HISTOGRAM_TARGETS + for (size_t i = 0; i < abs32_locations_.size(); ++i) { + RVA rva = abs32_locations_[i]; + // The 4 bytes at the relocation are a reference to some address. + uint32 target_address = Read32LittleEndian(RVAToPointer(rva)); + ++abs32_target_rvas_[target_address - image_base()]; + } +#endif + return true; +} + +void DisassemblerWin32X64::ParseRel32RelocsFromSections() { + uint32 file_offset = 0; + while (file_offset < length()) { + const Section* section = FindNextSection(file_offset); + if (section == NULL) + break; + if (file_offset < section->file_offset_of_raw_data) + file_offset = section->file_offset_of_raw_data; + ParseRel32RelocsFromSection(section); + file_offset += section->size_of_raw_data; + } + std::sort(rel32_locations_.begin(), rel32_locations_.end()); + +#if COURGETTE_HISTOGRAM_TARGETS + VLOG(1) << "abs32_locations_ " << abs32_locations_.size() + << "\nrel32_locations_ " << rel32_locations_.size() + << "\nabs32_target_rvas_ " << abs32_target_rvas_.size() + << "\nrel32_target_rvas_ " << rel32_target_rvas_.size(); + + int common = 0; + std::map<RVA, int>::iterator abs32_iter = abs32_target_rvas_.begin(); + std::map<RVA, int>::iterator rel32_iter = rel32_target_rvas_.begin(); + while (abs32_iter != abs32_target_rvas_.end() && + rel32_iter != rel32_target_rvas_.end()) { + if (abs32_iter->first < rel32_iter->first) + ++abs32_iter; + else if (rel32_iter->first < abs32_iter->first) + ++rel32_iter; + else { + ++common; + ++abs32_iter; + ++rel32_iter; + } + } + VLOG(1) << "common " << common; +#endif +} + +void DisassemblerWin32X64::ParseRel32RelocsFromSection(const Section* section) { + // TODO(sra): use characteristic. + bool isCode = strcmp(section->name, ".text") == 0; + if (!isCode) + return; + + uint32 start_file_offset = section->file_offset_of_raw_data; + uint32 end_file_offset = start_file_offset + section->size_of_raw_data; + RVA relocs_start_rva = base_relocation_table().address_; + + const uint8* start_pointer = OffsetToPointer(start_file_offset); + const uint8* end_pointer = OffsetToPointer(end_file_offset); + + RVA start_rva = FileOffsetToRVA(start_file_offset); + RVA end_rva = start_rva + section->virtual_size; + + // Quick way to convert from Pointer to RVA within a single Section is to + // subtract 'pointer_to_rva'. + const uint8* const adjust_pointer_to_rva = start_pointer - start_rva; + + std::vector<RVA>::iterator abs32_pos = abs32_locations_.begin(); + + // Find the rel32 relocations. + const uint8* p = start_pointer; + while (p < end_pointer) { + RVA current_rva = static_cast<RVA>(p - adjust_pointer_to_rva); + if (current_rva == relocs_start_rva) { + uint32 relocs_size = base_relocation_table().size_; + if (relocs_size) { + p += relocs_size; + continue; + } + } + + //while (abs32_pos != abs32_locations_.end() && *abs32_pos < current_rva) + // ++abs32_pos; + + // 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* rel32 = NULL; + + 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[1] != 0x8A && p[1] != 0x8B) // JPE/JPO unlikely + rel32 = p + 2; + } + } + if (rel32) { + RVA rel32_rva = static_cast<RVA>(rel32 - adjust_pointer_to_rva); + + // Is there an abs32 reloc overlapping the candidate? + while (abs32_pos != abs32_locations_.end() && *abs32_pos < rel32_rva - 3) + ++abs32_pos; + // Now: (*abs32_pos > rel32_rva - 4) i.e. the lowest addressed 4-byte + // region that could overlap rel32_rva. + if (abs32_pos != abs32_locations_.end()) { + if (*abs32_pos < rel32_rva + 4) { + // Beginning of abs32 reloc is before end of rel32 reloc so they + // overlap. Skip four bytes past the abs32 reloc. + p += (*abs32_pos + 4) - current_rva; + continue; + } + } + + RVA target_rva = rel32_rva + 4 + Read32LittleEndian(rel32); + // To be valid, rel32 target must be within image, and within this + // section. + if (IsValidRVA(target_rva) && + start_rva <= target_rva && target_rva < end_rva) { + rel32_locations_.push_back(rel32_rva); +#if COURGETTE_HISTOGRAM_TARGETS + ++rel32_target_rvas_[target_rva]; +#endif + p = rel32 + 4; + continue; + } + } + p += 1; + } +} + +CheckBool DisassemblerWin32X64::ParseNonSectionFileRegion( + uint32 start_file_offset, + uint32 end_file_offset, + AssemblyProgram* program) { + if (incomplete_disassembly_) + return true; + + const uint8* start = OffsetToPointer(start_file_offset); + const uint8* end = OffsetToPointer(end_file_offset); + + const uint8* p = start; + + while (p < end) { + if (!program->EmitByteInstruction(*p)) + return false; + ++p; + } + + return true; +} + +CheckBool DisassemblerWin32X64::ParseFileRegion( + const Section* section, + uint32 start_file_offset, uint32 end_file_offset, + AssemblyProgram* program) { + RVA relocs_start_rva = base_relocation_table().address_; + + const uint8* start_pointer = OffsetToPointer(start_file_offset); + const uint8* end_pointer = OffsetToPointer(end_file_offset); + + RVA start_rva = FileOffsetToRVA(start_file_offset); + RVA end_rva = start_rva + section->virtual_size; + + // Quick way to convert from Pointer to RVA within a single Section is to + // subtract 'pointer_to_rva'. + const uint8* const adjust_pointer_to_rva = start_pointer - start_rva; + + std::vector<RVA>::iterator rel32_pos = rel32_locations_.begin(); + std::vector<RVA>::iterator abs32_pos = abs32_locations_.begin(); + + if (!program->EmitOriginInstruction(start_rva)) + return false; + + const uint8* p = start_pointer; + + while (p < end_pointer) { + RVA current_rva = static_cast<RVA>(p - adjust_pointer_to_rva); + + // The base relocation table is usually in the .relocs section, but it could + // actually be anywhere. Make sure we skip it because we will regenerate it + // during assembly. + if (current_rva == relocs_start_rva) { + if (!program->EmitPeRelocsInstruction()) + return false; + uint32 relocs_size = base_relocation_table().size_; + if (relocs_size) { + p += relocs_size; + continue; + } + } + + while (abs32_pos != abs32_locations_.end() && *abs32_pos < current_rva) + ++abs32_pos; + + if (abs32_pos != abs32_locations_.end() && *abs32_pos == current_rva) { + uint32 target_address = Read32LittleEndian(p); + RVA target_rva = target_address - image_base(); + // TODO(sra): target could be Label+offset. It is not clear how to guess + // which it might be. We assume offset==0. + if (!program->EmitAbs32(program->FindOrMakeAbs32Label(target_rva))) + return false; + p += 4; + continue; + } + + while (rel32_pos != rel32_locations_.end() && *rel32_pos < current_rva) + ++rel32_pos; + + if (rel32_pos != rel32_locations_.end() && *rel32_pos == current_rva) { + RVA target_rva = current_rva + 4 + Read32LittleEndian(p); + if (!program->EmitRel32(program->FindOrMakeRel32Label(target_rva))) + return false; + p += 4; + continue; + } + + if (incomplete_disassembly_) { + if ((abs32_pos == abs32_locations_.end() || end_rva <= *abs32_pos) && + (rel32_pos == rel32_locations_.end() || end_rva <= *rel32_pos) && + (end_rva <= relocs_start_rva || current_rva >= relocs_start_rva)) { + // No more relocs in this section, don't bother encoding bytes. + break; + } + } + + if (!program->EmitByteInstruction(*p)) + return false; + p += 1; + } + + return true; +} + +#if COURGETTE_HISTOGRAM_TARGETS +// Histogram is printed to std::cout. It is purely for debugging the algorithm +// and is only enabled manually in 'exploration' builds. I don't want to add +// command-line configuration for this feature because this code has to be +// small, which means compiled-out. +void DisassemblerWin32X64::HistogramTargets(const char* kind, + const std::map<RVA, int>& map) { + int total = 0; + std::map<int, std::vector<RVA> > h; + for (std::map<RVA, int>::const_iterator p = map.begin(); + p != map.end(); + ++p) { + h[p->second].push_back(p->first); + total += p->second; + } + + std::cout << total << " " << kind << " to " + << map.size() << " unique targets" << std::endl; + + std::cout << "indegree: #targets-with-indegree (example)" << std::endl; + const int kFirstN = 15; + bool someSkipped = false; + int index = 0; + for (std::map<int, std::vector<RVA> >::reverse_iterator p = h.rbegin(); + p != h.rend(); + ++p) { + ++index; + if (index <= kFirstN || p->first <= 3) { + if (someSkipped) { + std::cout << "..." << std::endl; + } + size_t count = p->second.size(); + std::cout << std::dec << p->first << ": " << count; + if (count <= 2) { + for (size_t i = 0; i < count; ++i) + std::cout << " " << DescribeRVA(p->second[i]); + } + std::cout << std::endl; + someSkipped = false; + } else { + someSkipped = true; + } + } +} +#endif // COURGETTE_HISTOGRAM_TARGETS + + +// DescribeRVA is for debugging only. I would put it under #ifdef DEBUG except +// that during development I'm finding I need to call it when compiled in +// Release mode. Hence: +// TODO(sra): make this compile only for debug mode. +std::string DisassemblerWin32X64::DescribeRVA(RVA rva) const { + const Section* section = RVAToSection(rva); + std::ostringstream s; + s << std::hex << rva; + if (section) { + s << " ("; + s << SectionName(section) << "+" + << std::hex << (rva - section->virtual_address) + << ")"; + } + return s.str(); +} + +const Section* DisassemblerWin32X64::FindNextSection(uint32 fileOffset) const { + const Section* best = 0; + for (int i = 0; i < number_of_sections_; i++) { + const Section* section = §ions_[i]; + if (section->size_of_raw_data > 0) { // i.e. has data in file. + if (fileOffset <= section->file_offset_of_raw_data) { + if (best == 0 || + section->file_offset_of_raw_data < best->file_offset_of_raw_data) { + best = section; + } + } + } + } + return best; +} + +RVA DisassemblerWin32X64::FileOffsetToRVA(uint32 file_offset) const { + for (int i = 0; i < number_of_sections_; i++) { + const Section* section = §ions_[i]; + uint32 offset = file_offset - section->file_offset_of_raw_data; + if (offset < section->size_of_raw_data) { + return section->virtual_address + offset; + } + } + return 0; +} + +bool DisassemblerWin32X64::ReadDataDirectory( + int index, + ImageDataDirectory* directory) { + + if (index < number_of_data_directories_) { + size_t offset = index * 8 + offset_of_data_directories_; + if (offset >= size_of_optional_header_) + return Bad("number of data directories inconsistent"); + const uint8* data_directory = optional_header_ + offset; + if (data_directory < start() || + data_directory + 8 >= end()) + return Bad("data directory outside image"); + RVA rva = ReadU32(data_directory, 0); + size_t size = ReadU32(data_directory, 4); + if (size > size_of_image_) + return Bad("data directory size too big"); + + // TODO(sra): validate RVA. + directory->address_ = rva; + directory->size_ = static_cast<uint32>(size); + return true; + } else { + directory->address_ = 0; + directory->size_ = 0; + return true; + } +} + +} // namespace courgette |