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
9import optparse
10import lldb
11import re
12import 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
16def 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.
54def 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  if this_module != None:
73    module_list.append (this_module)
74  if cur_thread.GetNumFrames() < 2:
75    return
76
77  cur_fp = process.ReadPointerFromMemory (initial_fp, lldb.SBError())
78  cur_pc = process.ReadPointerFromMemory (initial_fp + process.GetAddressByteSize(), lldb.SBError())
79
80  frame_num = 1
81
82  while cur_pc != 0 and cur_fp != 0 and cur_pc != lldb.LLDB_INVALID_ADDRESS and cur_fp != lldb.LLDB_INVALID_ADDRESS:
83    address_list.append (cur_pc)
84    this_module = backtrace_print_frame (target, frame_num, cur_pc, cur_fp)
85    if this_module != None:
86      module_list.append (this_module)
87    frame_num = frame_num + 1
88    next_pc = 0
89    next_fp = 0
90    if target.triple[0:6] == "x86_64" or target.triple[0:4] == "i386" or target.triple[0:3] == "arm":
91      error = lldb.SBError()
92      next_pc = process.ReadPointerFromMemory(cur_fp + process.GetAddressByteSize(), error)
93      if not error.Success():
94        next_pc = 0
95      next_fp = process.ReadPointerFromMemory(cur_fp, error)
96      if not error.Success():
97        next_fp = 0
98    # Clear the 0th bit for arm frames - this indicates it is a thumb frame
99    if target.triple[0:3] == "arm" and (next_pc & 1) == 1:
100      next_pc = next_pc & ~1
101    cur_pc = next_pc
102    cur_fp = next_fp
103  this_module = backtrace_print_frame (target, frame_num, cur_pc, cur_fp)
104  if this_module != None:
105    module_list.append (this_module)
106  return [module_list, address_list]
107
108def diagnose_unwind(debugger, command, result, dict):
109  """
110Gather diagnostic information to help debug incorrect unwind (backtrace)
111behavior in lldb.  When there is a backtrace that doesn't look
112correct, run this command with the correct thread selected and a
113large amount of diagnostic information will be printed, it is likely
114to be helpful when reporting the problem.
115  """
116
117  command_args = shlex.split(command)
118  parser = create_diagnose_unwind_options()
119  try:
120    (options, args) = parser.parse_args(command_args)
121  except:
122   return
123  target = debugger.GetSelectedTarget()
124  if target:
125    process = target.GetProcess()
126    if process:
127      thread = process.GetSelectedThread()
128      if thread:
129        lldb_versions_match = re.search(r'[lL][lL][dD][bB]-(\d+)([.](\d+))?([.](\d+))?', debugger.GetVersionString())
130        lldb_version = 0
131        lldb_minor = 0
132        if len(lldb_versions_match.groups()) >= 1 and lldb_versions_match.groups()[0]:
133          lldb_major = int(lldb_versions_match.groups()[0])
134        if len(lldb_versions_match.groups()) >= 5 and lldb_versions_match.groups()[4]:
135          lldb_minor = int(lldb_versions_match.groups()[4])
136
137        modules_seen = []
138        addresses_seen = []
139
140        print 'LLDB version %s' % debugger.GetVersionString()
141        print 'Unwind diagnostics for thread %d' % thread.GetIndexID()
142        print ""
143        print "============================================================================================="
144        print ""
145        print "OS plugin setting:"
146        debugger.HandleCommand("settings show target.process.python-os-plugin-path")
147        print ""
148        print "Live register context:"
149        thread.SetSelectedFrame(0)
150        debugger.HandleCommand("register read")
151        print ""
152        print "============================================================================================="
153        print ""
154        print "lldb's unwind algorithm:"
155        print ""
156        frame_num = 0
157        for frame in thread.frames:
158          if not frame.IsInlined():
159            this_module = backtrace_print_frame (target, frame_num, frame.GetPC(), frame.GetFP())
160            if this_module != None:
161              modules_seen.append (this_module)
162            addresses_seen.append (frame.GetPC())
163            frame_num = frame_num + 1
164        print ""
165        print "============================================================================================="
166        print ""
167        print "Simple stack walk algorithm:"
168        print ""
169        simple_bt_modules_and_addresses = simple_backtrace(debugger)
170        modules_seen += simple_bt_modules_and_addresses[0]
171        addresses_seen = set(addresses_seen)
172        addresses_seen.update(set(simple_bt_modules_and_addresses[1]))
173
174        print ""
175        print "============================================================================================="
176        print ""
177        print "Modules seen in stack walks:"
178        print ""
179        modules_already_seen = set()
180        for module in modules_seen:
181          if module != None and module.GetFileSpec().GetFilename() != None:
182            if not module.GetFileSpec().GetFilename() in modules_already_seen:
183              debugger.HandleCommand('image list %s' % module.GetFileSpec().GetFilename())
184              modules_already_seen.add(module.GetFileSpec().GetFilename())
185
186        print ""
187        print "============================================================================================="
188        print ""
189        print "Disassembly ofaddresses seen in stack walks:"
190        print ""
191        additional_addresses_to_disassemble = addresses_seen
192        for frame in thread.frames:
193          if not frame.IsInlined():
194            print "--------------------------------------------------------------------------------------"
195            print ""
196            print "Disassembly of %s, frame %d, address 0x%x" % (frame.GetFunctionName(), frame.GetFrameID(), frame.GetPC())
197            print ""
198            if target.triple[0:6] == "x86_64" or target.triple[0:4] == "i386":
199              debugger.HandleCommand('disassemble -F att -a 0x%x' % frame.GetPC())
200            else:
201              debugger.HandleCommand('disassemble -a 0x%x' % frame.GetPC())
202            if frame.GetPC() in additional_addresses_to_disassemble:
203              additional_addresses_to_disassemble.remove (frame.GetPC())
204
205        for address in list(additional_addresses_to_disassemble):
206          print "--------------------------------------------------------------------------------------"
207          print ""
208          print "Disassembly of 0x%x" % address
209          print ""
210          if target.triple[0:6] == "x86_64" or target.triple[0:4] == "i386":
211            debugger.HandleCommand('disassemble -F att -a 0x%x' % address)
212          else:
213            debugger.HandleCommand('disassemble -a 0x%x' % address)
214
215        print ""
216        print "============================================================================================="
217        print ""
218        additional_addresses_to_show_unwind = addresses_seen
219        for frame in thread.frames:
220          if not frame.IsInlined():
221            print "--------------------------------------------------------------------------------------"
222            print ""
223            print "Unwind instructions for %s, frame %d" % (frame.GetFunctionName(), frame.GetFrameID())
224            print ""
225            debugger.HandleCommand('image show-unwind -a "0x%x"' % frame.GetPC())
226            if frame.GetPC() in additional_addresses_to_show_unwind:
227              additional_addresses_to_show_unwind.remove (frame.GetPC())
228
229        for address in list(additional_addresses_to_show_unwind):
230          print "--------------------------------------------------------------------------------------"
231          print ""
232          print "Unwind instructions for 0x%x" % address
233          print ""
234          debugger.HandleCommand('image show-unwind -a "0x%x"' % address)
235
236def create_diagnose_unwind_options():
237  usage = "usage: %prog"
238  description='''Print diagnostic information about a thread backtrace which will help to debug unwind problems'''
239  parser = optparse.OptionParser(description=description, prog='diagnose_unwind',usage=usage)
240  return parser
241
242lldb.debugger.HandleCommand('command script add -f %s.diagnose_unwind diagnose-unwind' % __name__)
243print 'The "diagnose-unwind" command has been installed, type "help diagnose-unwind" for detailed help.'
244