1 # This implements the "diagnose-unwind" command, usually installed 2 # in the debug session like 3 # command script import lldb.diagnose 4 # it is used when lldb's backtrace fails -- it collects and prints 5 # information about the stack frames, and tries an alternate unwind 6 # algorithm, that will help to understand why lldb's unwind algorithm 7 # did not succeed. 8 9 import optparse 10 import lldb 11 import re 12 import shlex 13 14 # Print the frame number, pc, frame pointer, module UUID and function name 15 # Returns the SBModule that contains the PC, if it could be found 16 def backtrace_print_frame (target, frame_num, addr, fp): 17 process = target.GetProcess() 18 addr_for_printing = addr 19 addr_width = process.GetAddressByteSize() * 2 20 if frame_num > 0: 21 addr = addr - 1 22 23 sbaddr = lldb.SBAddress() 24 try: 25 sbaddr.SetLoadAddress(addr, target) 26 module_description = "" 27 if sbaddr.GetModule(): 28 module_filename = "" 29 module_uuid_str = sbaddr.GetModule().GetUUIDString() 30 if module_uuid_str == None: 31 module_uuid_str = "" 32 if sbaddr.GetModule().GetFileSpec(): 33 module_filename = sbaddr.GetModule().GetFileSpec().GetFilename() 34 if module_filename == None: 35 module_filename = "" 36 if module_uuid_str != "" or module_filename != "": 37 module_description = '%s %s' % (module_filename, module_uuid_str) 38 except Exception: 39 print '%2d: pc==0x%-*x fp==0x%-*x' % (frame_num, addr_width, addr_for_printing, addr_width, fp) 40 return 41 42 sym_ctx = target.ResolveSymbolContextForAddress(sbaddr, lldb.eSymbolContextEverything) 43 if sym_ctx.IsValid() and sym_ctx.GetSymbol().IsValid(): 44 function_start = sym_ctx.GetSymbol().GetStartAddress().GetLoadAddress(target) 45 offset = addr - function_start 46 print '%2d: pc==0x%-*x fp==0x%-*x %s %s + %d' % (frame_num, addr_width, addr_for_printing, addr_width, fp, module_description, sym_ctx.GetSymbol().GetName(), offset) 47 else: 48 print '%2d: pc==0x%-*x fp==0x%-*x %s' % (frame_num, addr_width, addr_for_printing, addr_width, fp, module_description) 49 return sbaddr.GetModule() 50 51 # A simple stack walk algorithm that follows the frame chain. 52 # Returns a two-element list; the first element is a list of modules 53 # seen and the second element is a list of addresses seen during the backtrace. 54 def simple_backtrace(debugger): 55 target = debugger.GetSelectedTarget() 56 process = target.GetProcess() 57 cur_thread = process.GetSelectedThread() 58 59 initial_fp = cur_thread.GetFrameAtIndex(0).GetFP() 60 61 # If the pseudoreg "fp" isn't recognized, on arm hardcode to r7 which is correct for Darwin programs. 62 if initial_fp == lldb.LLDB_INVALID_ADDRESS and target.triple[0:3] == "arm": 63 for reggroup in cur_thread.GetFrameAtIndex(1).registers: 64 if reggroup.GetName() == "General Purpose Registers": 65 for reg in reggroup: 66 if reg.GetName() == "r7": 67 initial_fp = int (reg.GetValue(), 16) 68 69 module_list = [] 70 address_list = [cur_thread.GetFrameAtIndex(0).GetPC()] 71 this_module = backtrace_print_frame (target, 0, cur_thread.GetFrameAtIndex(0).GetPC(), initial_fp) 72 print_stack_frame (process, initial_fp) 73 print "" 74 if this_module != None: 75 module_list.append (this_module) 76 if cur_thread.GetNumFrames() < 2: 77 return [module_list, address_list] 78 79 cur_fp = process.ReadPointerFromMemory (initial_fp, lldb.SBError()) 80 cur_pc = process.ReadPointerFromMemory (initial_fp + process.GetAddressByteSize(), lldb.SBError()) 81 82 frame_num = 1 83 84 while cur_pc != 0 and cur_fp != 0 and cur_pc != lldb.LLDB_INVALID_ADDRESS and cur_fp != lldb.LLDB_INVALID_ADDRESS: 85 address_list.append (cur_pc) 86 this_module = backtrace_print_frame (target, frame_num, cur_pc, cur_fp) 87 print_stack_frame (process, cur_fp) 88 print "" 89 if this_module != None: 90 module_list.append (this_module) 91 frame_num = frame_num + 1 92 next_pc = 0 93 next_fp = 0 94 if target.triple[0:6] == "x86_64" or target.triple[0:4] == "i386" or target.triple[0:3] == "arm": 95 error = lldb.SBError() 96 next_pc = process.ReadPointerFromMemory(cur_fp + process.GetAddressByteSize(), error) 97 if not error.Success(): 98 next_pc = 0 99 next_fp = process.ReadPointerFromMemory(cur_fp, error) 100 if not error.Success(): 101 next_fp = 0 102 # Clear the 0th bit for arm frames - this indicates it is a thumb frame 103 if target.triple[0:3] == "arm" and (next_pc & 1) == 1: 104 next_pc = next_pc & ~1 105 cur_pc = next_pc 106 cur_fp = next_fp 107 this_module = backtrace_print_frame (target, frame_num, cur_pc, cur_fp) 108 print_stack_frame (process, cur_fp) 109 print "" 110 if this_module != None: 111 module_list.append (this_module) 112 return [module_list, address_list] 113 114 def print_stack_frame(process, fp): 115 if fp == 0 or fp == lldb.LLDB_INVALID_ADDRESS or fp == 1: 116 return 117 addr_size = process.GetAddressByteSize() 118 addr = fp - (2 * addr_size) 119 i = 0 120 outline = "Stack frame from $fp-%d: " % (2 * addr_size) 121 error = lldb.SBError() 122 try: 123 while i < 5 and error.Success(): 124 address = process.ReadPointerFromMemory(addr + (i * addr_size), error) 125 outline += " 0x%x" % address 126 i += 1 127 print outline 128 except Exception: 129 return 130 131 def diagnose_unwind(debugger, command, result, dict): 132 """ 133 Gather diagnostic information to help debug incorrect unwind (backtrace) 134 behavior in lldb. When there is a backtrace that doesn't look 135 correct, run this command with the correct thread selected and a 136 large amount of diagnostic information will be printed, it is likely 137 to be helpful when reporting the problem. 138 """ 139 140 command_args = shlex.split(command) 141 parser = create_diagnose_unwind_options() 142 try: 143 (options, args) = parser.parse_args(command_args) 144 except: 145 return 146 target = debugger.GetSelectedTarget() 147 if target: 148 process = target.GetProcess() 149 if process: 150 thread = process.GetSelectedThread() 151 if thread: 152 lldb_versions_match = re.search(r'[lL][lL][dD][bB]-(\d+)([.](\d+))?([.](\d+))?', debugger.GetVersionString()) 153 lldb_version = 0 154 lldb_minor = 0 155 if len(lldb_versions_match.groups()) >= 1 and lldb_versions_match.groups()[0]: 156 lldb_major = int(lldb_versions_match.groups()[0]) 157 if len(lldb_versions_match.groups()) >= 5 and lldb_versions_match.groups()[4]: 158 lldb_minor = int(lldb_versions_match.groups()[4]) 159 160 modules_seen = [] 161 addresses_seen = [] 162 163 print 'LLDB version %s' % debugger.GetVersionString() 164 print 'Unwind diagnostics for thread %d' % thread.GetIndexID() 165 print "" 166 print "=============================================================================================" 167 print "" 168 print "OS plugin setting:" 169 debugger.HandleCommand("settings show target.process.python-os-plugin-path") 170 print "" 171 print "Live register context:" 172 thread.SetSelectedFrame(0) 173 debugger.HandleCommand("register read") 174 print "" 175 print "=============================================================================================" 176 print "" 177 print "lldb's unwind algorithm:" 178 print "" 179 frame_num = 0 180 for frame in thread.frames: 181 if not frame.IsInlined(): 182 this_module = backtrace_print_frame (target, frame_num, frame.GetPC(), frame.GetFP()) 183 print_stack_frame (process, frame.GetFP()) 184 print "" 185 if this_module != None: 186 modules_seen.append (this_module) 187 addresses_seen.append (frame.GetPC()) 188 frame_num = frame_num + 1 189 print "" 190 print "=============================================================================================" 191 print "" 192 print "Simple stack walk algorithm:" 193 print "" 194 (module_list, address_list) = simple_backtrace(debugger) 195 if module_list and module_list != None: 196 modules_seen += module_list 197 if address_list and address_list != None: 198 addresses_seen = set(addresses_seen) 199 addresses_seen.update(set(address_list)) 200 201 print "" 202 print "=============================================================================================" 203 print "" 204 print "Modules seen in stack walks:" 205 print "" 206 modules_already_seen = set() 207 for module in modules_seen: 208 if module != None and module.GetFileSpec().GetFilename() != None: 209 if not module.GetFileSpec().GetFilename() in modules_already_seen: 210 debugger.HandleCommand('image list %s' % module.GetFileSpec().GetFilename()) 211 modules_already_seen.add(module.GetFileSpec().GetFilename()) 212 213 print "" 214 print "=============================================================================================" 215 print "" 216 print "Disassembly ofaddresses seen in stack walks:" 217 print "" 218 additional_addresses_to_disassemble = addresses_seen 219 for frame in thread.frames: 220 if not frame.IsInlined(): 221 print "--------------------------------------------------------------------------------------" 222 print "" 223 print "Disassembly of %s, frame %d, address 0x%x" % (frame.GetFunctionName(), frame.GetFrameID(), frame.GetPC()) 224 print "" 225 if target.triple[0:6] == "x86_64" or target.triple[0:4] == "i386": 226 debugger.HandleCommand('disassemble -F att -a 0x%x' % frame.GetPC()) 227 else: 228 debugger.HandleCommand('disassemble -a 0x%x' % frame.GetPC()) 229 if frame.GetPC() in additional_addresses_to_disassemble: 230 additional_addresses_to_disassemble.remove (frame.GetPC()) 231 232 for address in list(additional_addresses_to_disassemble): 233 print "--------------------------------------------------------------------------------------" 234 print "" 235 print "Disassembly of 0x%x" % address 236 print "" 237 if target.triple[0:6] == "x86_64" or target.triple[0:4] == "i386": 238 debugger.HandleCommand('disassemble -F att -a 0x%x' % address) 239 else: 240 debugger.HandleCommand('disassemble -a 0x%x' % address) 241 242 print "" 243 print "=============================================================================================" 244 print "" 245 additional_addresses_to_show_unwind = addresses_seen 246 for frame in thread.frames: 247 if not frame.IsInlined(): 248 print "--------------------------------------------------------------------------------------" 249 print "" 250 print "Unwind instructions for %s, frame %d" % (frame.GetFunctionName(), frame.GetFrameID()) 251 print "" 252 debugger.HandleCommand('image show-unwind -a "0x%x"' % frame.GetPC()) 253 if frame.GetPC() in additional_addresses_to_show_unwind: 254 additional_addresses_to_show_unwind.remove (frame.GetPC()) 255 256 for address in list(additional_addresses_to_show_unwind): 257 print "--------------------------------------------------------------------------------------" 258 print "" 259 print "Unwind instructions for 0x%x" % address 260 print "" 261 debugger.HandleCommand('image show-unwind -a "0x%x"' % address) 262 263 def create_diagnose_unwind_options(): 264 usage = "usage: %prog" 265 description='''Print diagnostic information about a thread backtrace which will help to debug unwind problems''' 266 parser = optparse.OptionParser(description=description, prog='diagnose_unwind',usage=usage) 267 return parser 268 269 lldb.debugger.HandleCommand('command script add -f %s.diagnose_unwind diagnose-unwind' % __name__) 270 print 'The "diagnose-unwind" command has been installed, type "help diagnose-unwind" for detailed help.' 271
