1 /* 2 * Copyright (C) 2016 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ART_COMPILER_DEBUG_ELF_DEBUG_LINE_WRITER_H_ 18 #define ART_COMPILER_DEBUG_ELF_DEBUG_LINE_WRITER_H_ 19 20 #include <unordered_set> 21 #include <vector> 22 23 #include "debug/dwarf/debug_line_opcode_writer.h" 24 #include "debug/dwarf/headers.h" 25 #include "debug/elf_compilation_unit.h" 26 #include "debug/src_map_elem.h" 27 #include "dex/dex_file-inl.h" 28 #include "linker/elf_builder.h" 29 #include "oat_file.h" 30 #include "stack_map.h" 31 32 namespace art { 33 namespace debug { 34 35 typedef std::vector<DexFile::PositionInfo> PositionInfos; 36 37 static bool PositionInfoCallback(void* ctx, const DexFile::PositionInfo& entry) { 38 static_cast<PositionInfos*>(ctx)->push_back(entry); 39 return false; 40 } 41 42 template<typename ElfTypes> 43 class ElfDebugLineWriter { 44 using Elf_Addr = typename ElfTypes::Addr; 45 46 public: 47 explicit ElfDebugLineWriter(linker::ElfBuilder<ElfTypes>* builder) : builder_(builder) { 48 } 49 50 void Start() { 51 builder_->GetDebugLine()->Start(); 52 } 53 54 // Write line table for given set of methods. 55 // Returns the number of bytes written. 56 size_t WriteCompilationUnit(ElfCompilationUnit& compilation_unit) { 57 const InstructionSet isa = builder_->GetIsa(); 58 const bool is64bit = Is64BitInstructionSet(isa); 59 const Elf_Addr base_address = compilation_unit.is_code_address_text_relative 60 ? builder_->GetText()->GetAddress() 61 : 0; 62 63 compilation_unit.debug_line_offset = builder_->GetDebugLine()->GetPosition(); 64 65 std::vector<dwarf::FileEntry> files; 66 std::unordered_map<std::string, size_t> files_map; 67 std::vector<std::string> directories; 68 std::unordered_map<std::string, size_t> directories_map; 69 int code_factor_bits_ = 0; 70 int dwarf_isa = -1; 71 switch (isa) { 72 case InstructionSet::kArm: // arm actually means thumb2. 73 case InstructionSet::kThumb2: 74 code_factor_bits_ = 1; // 16-bit instuctions 75 dwarf_isa = 1; // DW_ISA_ARM_thumb. 76 break; 77 case InstructionSet::kArm64: 78 case InstructionSet::kMips: 79 case InstructionSet::kMips64: 80 code_factor_bits_ = 2; // 32-bit instructions 81 break; 82 case InstructionSet::kNone: 83 case InstructionSet::kX86: 84 case InstructionSet::kX86_64: 85 break; 86 } 87 std::unordered_set<uint64_t> seen_addresses(compilation_unit.methods.size()); 88 dwarf::DebugLineOpCodeWriter<> opcodes(is64bit, code_factor_bits_); 89 for (const MethodDebugInfo* mi : compilation_unit.methods) { 90 // Ignore function if we have already generated line table for the same address. 91 // It would confuse the debugger and the DWARF specification forbids it. 92 // We allow the line table for method to be replicated in different compilation unit. 93 // This ensures that each compilation unit contains line table for all its methods. 94 if (!seen_addresses.insert(mi->code_address).second) { 95 continue; 96 } 97 98 uint32_t prologue_end = std::numeric_limits<uint32_t>::max(); 99 std::vector<SrcMapElem> pc2dex_map; 100 if (mi->code_info != nullptr) { 101 // Use stack maps to create mapping table from pc to dex. 102 const CodeInfo code_info(mi->code_info); 103 const CodeInfoEncoding encoding = code_info.ExtractEncoding(); 104 pc2dex_map.reserve(code_info.GetNumberOfStackMaps(encoding)); 105 for (uint32_t s = 0; s < code_info.GetNumberOfStackMaps(encoding); s++) { 106 StackMap stack_map = code_info.GetStackMapAt(s, encoding); 107 DCHECK(stack_map.IsValid()); 108 const uint32_t pc = stack_map.GetNativePcOffset(encoding.stack_map.encoding, isa); 109 const int32_t dex = stack_map.GetDexPc(encoding.stack_map.encoding); 110 pc2dex_map.push_back({pc, dex}); 111 if (stack_map.HasDexRegisterMap(encoding.stack_map.encoding)) { 112 // Guess that the first map with local variables is the end of prologue. 113 prologue_end = std::min(prologue_end, pc); 114 } 115 } 116 std::sort(pc2dex_map.begin(), pc2dex_map.end()); 117 } 118 119 if (pc2dex_map.empty()) { 120 continue; 121 } 122 123 // Compensate for compiler's off-by-one-instruction error. 124 // 125 // The compiler generates stackmap with PC *after* the branch instruction 126 // (because this is the PC which is easier to obtain when unwinding). 127 // 128 // However, the debugger is more clever and it will ask us for line-number 129 // mapping at the location of the branch instruction (since the following 130 // instruction could belong to other line, this is the correct thing to do). 131 // 132 // So we really want to just decrement the PC by one instruction so that the 133 // branch instruction is covered as well. However, we do not know the size 134 // of the previous instruction, and we can not subtract just a fixed amount 135 // (the debugger would trust us that the PC is valid; it might try to set 136 // breakpoint there at some point, and setting breakpoint in mid-instruction 137 // would make the process crash in spectacular way). 138 // 139 // Therefore, we say that the PC which the compiler gave us for the stackmap 140 // is the end of its associated address range, and we use the PC from the 141 // previous stack map as the start of the range. This ensures that the PC is 142 // valid and that the branch instruction is covered. 143 // 144 // This ensures we have correct line number mapping at call sites (which is 145 // important for backtraces), but there is nothing we can do for non-call 146 // sites (so stepping through optimized code in debugger is not possible). 147 // 148 // We do not adjust the stackmaps if the code was compiled as debuggable. 149 // In that case, the stackmaps should accurately cover all instructions. 150 if (!mi->is_native_debuggable) { 151 for (size_t i = pc2dex_map.size() - 1; i > 0; --i) { 152 pc2dex_map[i].from_ = pc2dex_map[i - 1].from_; 153 } 154 pc2dex_map[0].from_ = 0; 155 } 156 157 Elf_Addr method_address = base_address + mi->code_address; 158 159 PositionInfos dex2line_map; 160 DCHECK(mi->dex_file != nullptr); 161 const DexFile* dex = mi->dex_file; 162 CodeItemDebugInfoAccessor accessor(*dex, mi->code_item, mi->dex_method_index); 163 const uint32_t debug_info_offset = accessor.DebugInfoOffset(); 164 if (!dex->DecodeDebugPositionInfo(debug_info_offset, PositionInfoCallback, &dex2line_map)) { 165 continue; 166 } 167 168 if (dex2line_map.empty()) { 169 continue; 170 } 171 172 opcodes.SetAddress(method_address); 173 if (dwarf_isa != -1) { 174 opcodes.SetISA(dwarf_isa); 175 } 176 177 // Get and deduplicate directory and filename. 178 int file_index = 0; // 0 - primary source file of the compilation. 179 auto& dex_class_def = dex->GetClassDef(mi->class_def_index); 180 const char* source_file = dex->GetSourceFile(dex_class_def); 181 if (source_file != nullptr) { 182 std::string file_name(source_file); 183 size_t file_name_slash = file_name.find_last_of('/'); 184 std::string class_name(dex->GetClassDescriptor(dex_class_def)); 185 size_t class_name_slash = class_name.find_last_of('/'); 186 std::string full_path(file_name); 187 188 // Guess directory from package name. 189 int directory_index = 0; // 0 - current directory of the compilation. 190 if (file_name_slash == std::string::npos && // Just filename. 191 class_name.front() == 'L' && // Type descriptor for a class. 192 class_name_slash != std::string::npos) { // Has package name. 193 std::string package_name = class_name.substr(1, class_name_slash - 1); 194 auto it = directories_map.find(package_name); 195 if (it == directories_map.end()) { 196 directory_index = 1 + directories.size(); 197 directories_map.emplace(package_name, directory_index); 198 directories.push_back(package_name); 199 } else { 200 directory_index = it->second; 201 } 202 full_path = package_name + "/" + file_name; 203 } 204 205 // Add file entry. 206 auto it2 = files_map.find(full_path); 207 if (it2 == files_map.end()) { 208 file_index = 1 + files.size(); 209 files_map.emplace(full_path, file_index); 210 files.push_back(dwarf::FileEntry { 211 file_name, 212 directory_index, 213 0, // Modification time - NA. 214 0, // File size - NA. 215 }); 216 } else { 217 file_index = it2->second; 218 } 219 } 220 opcodes.SetFile(file_index); 221 222 // Generate mapping opcodes from PC to Java lines. 223 if (file_index != 0) { 224 // If the method was not compiled as native-debuggable, we still generate all available 225 // lines, but we try to prevent the debugger from stepping and setting breakpoints since 226 // the information is too inaccurate for that (breakpoints would be set after the calls). 227 const bool default_is_stmt = mi->is_native_debuggable; 228 bool first = true; 229 for (SrcMapElem pc2dex : pc2dex_map) { 230 uint32_t pc = pc2dex.from_; 231 int dex_pc = pc2dex.to_; 232 // Find mapping with address with is greater than our dex pc; then go back one step. 233 auto dex2line = std::upper_bound( 234 dex2line_map.begin(), 235 dex2line_map.end(), 236 dex_pc, 237 [](uint32_t address, const DexFile::PositionInfo& entry) { 238 return address < entry.address_; 239 }); 240 // Look for first valid mapping after the prologue. 241 if (dex2line != dex2line_map.begin() && pc >= prologue_end) { 242 int line = (--dex2line)->line_; 243 if (first) { 244 first = false; 245 if (pc > 0) { 246 // Assume that any preceding code is prologue. 247 int first_line = dex2line_map.front().line_; 248 // Prologue is not a sensible place for a breakpoint. 249 opcodes.SetIsStmt(false); 250 opcodes.AddRow(method_address, first_line); 251 opcodes.SetPrologueEnd(); 252 } 253 opcodes.SetIsStmt(default_is_stmt); 254 opcodes.AddRow(method_address + pc, line); 255 } else if (line != opcodes.CurrentLine()) { 256 opcodes.SetIsStmt(default_is_stmt); 257 opcodes.AddRow(method_address + pc, line); 258 } 259 } 260 } 261 } else { 262 // line 0 - instruction cannot be attributed to any source line. 263 opcodes.AddRow(method_address, 0); 264 } 265 266 opcodes.AdvancePC(method_address + mi->code_size); 267 opcodes.EndSequence(); 268 } 269 std::vector<uint8_t> buffer; 270 buffer.reserve(opcodes.data()->size() + KB); 271 size_t offset = builder_->GetDebugLine()->GetPosition(); 272 WriteDebugLineTable(directories, files, opcodes, offset, &buffer, &debug_line_patches_); 273 builder_->GetDebugLine()->WriteFully(buffer.data(), buffer.size()); 274 return buffer.size(); 275 } 276 277 void End(bool write_oat_patches) { 278 builder_->GetDebugLine()->End(); 279 if (write_oat_patches) { 280 builder_->WritePatches(".debug_line.oat_patches", 281 ArrayRef<const uintptr_t>(debug_line_patches_)); 282 } 283 } 284 285 private: 286 linker::ElfBuilder<ElfTypes>* builder_; 287 std::vector<uintptr_t> debug_line_patches_; 288 }; 289 290 } // namespace debug 291 } // namespace art 292 293 #endif // ART_COMPILER_DEBUG_ELF_DEBUG_LINE_WRITER_H_ 294 295
