| // Copyright (c) 2009 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.h" |
| |
| #include <algorithm> |
| #include <iostream> |
| #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" |
| #include "courgette/image_info.h" |
| |
| // COURGETTE_HISTOGRAM_TARGETS prints out a histogram of how frequently |
| // different target addresses are referenced. Purely for debugging. |
| #define COURGETTE_HISTOGRAM_TARGETS 0 |
| |
| namespace courgette { |
| |
| class DisassemblerWin32X86 : public Disassembler { |
| public: |
| explicit DisassemblerWin32X86(PEInfo* pe_info) |
| : pe_info_(pe_info), |
| incomplete_disassembly_(false) { |
| } |
| |
| virtual bool Disassemble(AssemblyProgram* target); |
| |
| virtual void Destroy() { delete this; } |
| |
| protected: |
| PEInfo& pe_info() { return *pe_info_; } |
| |
| void ParseFile(AssemblyProgram* target); |
| bool ParseAbs32Relocs(); |
| void ParseRel32RelocsFromSections(); |
| void ParseRel32RelocsFromSection(const Section* section); |
| |
| void ParseNonSectionFileRegion(uint32 start_file_offset, |
| uint32 end_file_offset, |
| AssemblyProgram* program); |
| void ParseFileRegion(const Section* section, |
| uint32 start_file_offset, uint32 end_file_offset, |
| AssemblyProgram* program); |
| |
| #if COURGETTE_HISTOGRAM_TARGETS |
| void HistogramTargets(const char* kind, const std::map<RVA, int>& map); |
| #endif |
| |
| PEInfo* pe_info_; |
| bool incomplete_disassembly_; // 'true' if can leave out 'uninteresting' bits |
| |
| std::vector<RVA> abs32_locations_; |
| std::vector<RVA> rel32_locations_; |
| |
| #if COURGETTE_HISTOGRAM_TARGETS |
| std::map<RVA, int> abs32_target_rvas_; |
| std::map<RVA, int> rel32_target_rvas_; |
| #endif |
| }; |
| |
| bool DisassemblerWin32X86::Disassemble(AssemblyProgram* target) { |
| if (!pe_info().ok()) |
| return false; |
| |
| target->set_image_base(pe_info().image_base()); |
| |
| if (!ParseAbs32Relocs()) |
| return false; |
| |
| ParseRel32RelocsFromSections(); |
| |
| ParseFile(target); |
| |
| target->DefaultAssignIndexes(); |
| return true; |
| } |
| |
| static uint32 Read32LittleEndian(const void* address) { |
| return *reinterpret_cast<const uint32*>(address); |
| } |
| |
| bool DisassemblerWin32X86::ParseAbs32Relocs() { |
| abs32_locations_.clear(); |
| if (!pe_info().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(pe_info().RVAToPointer(rva)); |
| ++abs32_target_rvas_[target_address - pe_info().image_base()]; |
| } |
| #endif |
| return true; |
| } |
| |
| void DisassemblerWin32X86::ParseRel32RelocsFromSections() { |
| uint32 file_offset = 0; |
| while (file_offset < pe_info().length()) { |
| const Section* section = pe_info().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 |
| LOG(INFO) << "abs32_locations_ " << abs32_locations_.size(); |
| LOG(INFO) << "rel32_locations_ " << rel32_locations_.size(); |
| LOG(INFO) << "abs32_target_rvas_ " << abs32_target_rvas_.size(); |
| LOG(INFO) << "rel32_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; |
| } |
| } |
| LOG(INFO) << "common " << common; |
| #endif |
| } |
| |
| void DisassemblerWin32X86::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 = pe_info().base_relocation_table().address_; |
| |
| const uint8* start_pointer = pe_info().FileOffsetToPointer(start_file_offset); |
| const uint8* end_pointer = pe_info().FileOffsetToPointer(end_file_offset); |
| |
| RVA start_rva = pe_info().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 = p - adjust_pointer_to_rva; |
| if (current_rva == relocs_start_rva) { |
| uint32 relocs_size = pe_info().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 = 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 (pe_info().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 += 4; |
| continue; |
| } |
| } |
| p += 1; |
| } |
| } |
| |
| void DisassemblerWin32X86::ParseFile(AssemblyProgram* program) { |
| // Walk all the bytes in the file, whether or not in a section. |
| uint32 file_offset = 0; |
| while (file_offset < pe_info().length()) { |
| const Section* section = pe_info().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; |
| ParseNonSectionFileRegion(file_offset, section_start_offset, program); |
| file_offset = section_start_offset; |
| } |
| uint32 end = file_offset + section->size_of_raw_data; |
| ParseFileRegion(section, file_offset, end, program); |
| file_offset = end; |
| } |
| |
| #if COURGETTE_HISTOGRAM_TARGETS |
| HistogramTargets("abs32 relocs", abs32_target_rvas_); |
| HistogramTargets("rel32 relocs", rel32_target_rvas_); |
| #endif |
| } |
| |
| void DisassemblerWin32X86::ParseNonSectionFileRegion( |
| uint32 start_file_offset, |
| uint32 end_file_offset, |
| AssemblyProgram* program) { |
| if (incomplete_disassembly_) |
| return; |
| |
| const uint8* start = pe_info().FileOffsetToPointer(start_file_offset); |
| const uint8* end = pe_info().FileOffsetToPointer(end_file_offset); |
| |
| const uint8* p = start; |
| |
| while (p < end) { |
| program->EmitByteInstruction(*p); |
| ++p; |
| } |
| } |
| |
| void DisassemblerWin32X86::ParseFileRegion( |
| const Section* section, |
| uint32 start_file_offset, uint32 end_file_offset, |
| AssemblyProgram* program) { |
| RVA relocs_start_rva = pe_info().base_relocation_table().address_; |
| |
| const uint8* start_pointer = pe_info().FileOffsetToPointer(start_file_offset); |
| const uint8* end_pointer = pe_info().FileOffsetToPointer(end_file_offset); |
| |
| RVA start_rva = pe_info().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(); |
| |
| program->EmitOriginInstruction(start_rva); |
| |
| const uint8* p = start_pointer; |
| |
| while (p < end_pointer) { |
| RVA current_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) { |
| program->EmitMakeRelocsInstruction(); |
| uint32 relocs_size = pe_info().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 - pe_info().image_base(); |
| // TODO(sra): target could be Label+offset. It is not clear how to guess |
| // which it might be. We assume offset==0. |
| program->EmitAbs32(program->FindOrMakeAbs32Label(target_rva)); |
| 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); |
| program->EmitRel32(program->FindOrMakeRel32Label(target_rva)); |
| 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; |
| } |
| } |
| |
| program->EmitByteInstruction(*p); |
| p += 1; |
| } |
| } |
| |
| #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 DisassemblerWin32X86::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 << " " << pe_info().DescribeRVA(p->second[i]); |
| } |
| std::cout << std::endl; |
| someSkipped = false; |
| } else { |
| someSkipped = true; |
| } |
| } |
| } |
| #endif // COURGETTE_HISTOGRAM_TARGETS |
| |
| Disassembler* Disassembler::MakeDisassemberWin32X86(PEInfo* pe_info) { |
| return new DisassemblerWin32X86(pe_info); |
| } |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| Status ParseWin32X86PE(const void* buffer, size_t length, |
| AssemblyProgram** output) { |
| *output = NULL; |
| |
| PEInfo* pe_info = new PEInfo(); |
| pe_info->Init(buffer, length); |
| |
| if (!pe_info->ParseHeader()) { |
| delete pe_info; |
| return C_INPUT_NOT_RECOGNIZED; |
| } |
| |
| Disassembler* disassembler = Disassembler::MakeDisassemberWin32X86(pe_info); |
| AssemblyProgram* program = new AssemblyProgram(); |
| |
| if (!disassembler->Disassemble(program)) { |
| delete program; |
| disassembler->Destroy(); |
| delete pe_info; |
| return C_DISASSEMBLY_FAILED; |
| } |
| |
| disassembler->Destroy(); |
| delete pe_info; |
| *output = program; |
| return C_OK; |
| } |
| |
| void DeleteAssemblyProgram(AssemblyProgram* program) { |
| delete program; |
| } |
| |
| } // namespace courgette |