1 files changed, 270 insertions, 0 deletions
diff --git a/examples/python/diagnose_unwind.py b/examples/python/diagnose_unwind.py
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+++ b/examples/python/diagnose_unwind.py
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+# This implements the "diagnose-unwind" command, usually installed
+# in the debug session like
+#   command script import lldb.diagnose
+# it is used when lldb's backtrace fails -- it collects and prints
+# information about the stack frames, and tries an alternate unwind
+# algorithm, that will help to understand why lldb's unwind algorithm
+# did not succeed.
+
+import optparse
+import lldb
+import re
+import shlex
+
+# Print the frame number, pc, frame pointer, module UUID and function name
+# Returns the SBModule that contains the PC, if it could be found
+def backtrace_print_frame (target, frame_num, addr, fp):
+  process = target.GetProcess()
+  addr_for_printing = addr
+  addr_width = process.GetAddressByteSize() * 2
+  if frame_num > 0:
+    addr = addr - 1
+
+  sbaddr = lldb.SBAddress()
+  try:
+    sbaddr.SetLoadAddress(addr, target)
+    module_description = ""
+    if sbaddr.GetModule():
+      module_filename = ""
+      module_uuid_str = sbaddr.GetModule().GetUUIDString()
+      if module_uuid_str == None:
+        module_uuid_str = ""
+      if sbaddr.GetModule().GetFileSpec():
+        module_filename = sbaddr.GetModule().GetFileSpec().GetFilename()
+        if module_filename == None:
+          module_filename = ""
+      if module_uuid_str != "" or module_filename != "":
+        module_description = '%s %s' % (module_filename, module_uuid_str)
+  except Exception:
+    print '%2d: pc==0x%-*x fp==0x%-*x' % (frame_num, addr_width, addr_for_printing, addr_width, fp)
+    return
+
+  sym_ctx = target.ResolveSymbolContextForAddress(sbaddr, lldb.eSymbolContextEverything)
+  if sym_ctx.IsValid() and sym_ctx.GetSymbol().IsValid():
+    function_start = sym_ctx.GetSymbol().GetStartAddress().GetLoadAddress(target)
+    offset = addr - function_start
+    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)
+  else:
+    print '%2d: pc==0x%-*x fp==0x%-*x %s' % (frame_num, addr_width, addr_for_printing, addr_width, fp, module_description)
+  return sbaddr.GetModule()
+
+# A simple stack walk algorithm that follows the frame chain.
+# Returns a two-element list; the first element is a list of modules
+# seen and the second element is a list of addresses seen during the backtrace.
+def simple_backtrace(debugger):
+  target = debugger.GetSelectedTarget()
+  process = target.GetProcess()
+  cur_thread = process.GetSelectedThread()
+
+  initial_fp = cur_thread.GetFrameAtIndex(0).GetFP()
+
+  # If the pseudoreg "fp" isn't recognized, on arm hardcode to r7 which is correct for Darwin programs.
+  if initial_fp == lldb.LLDB_INVALID_ADDRESS and target.triple[0:3] == "arm":
+    for reggroup in cur_thread.GetFrameAtIndex(1).registers:
+      if reggroup.GetName() == "General Purpose Registers":
+        for reg in reggroup:
+          if reg.GetName() == "r7":
+            initial_fp = int (reg.GetValue(), 16)
+
+  module_list = []
+  address_list = [cur_thread.GetFrameAtIndex(0).GetPC()]
+  this_module = backtrace_print_frame (target, 0, cur_thread.GetFrameAtIndex(0).GetPC(), initial_fp)
+  print_stack_frame (process, initial_fp)
+  print ""
+  if this_module != None:
+    module_list.append (this_module)
+  if cur_thread.GetNumFrames() < 2:
+    return [module_list, address_list]
+
+  cur_fp = process.ReadPointerFromMemory (initial_fp, lldb.SBError())
+  cur_pc = process.ReadPointerFromMemory (initial_fp + process.GetAddressByteSize(), lldb.SBError())
+
+  frame_num = 1
+
+  while cur_pc != 0 and cur_fp != 0 and cur_pc != lldb.LLDB_INVALID_ADDRESS and cur_fp != lldb.LLDB_INVALID_ADDRESS:
+    address_list.append (cur_pc)
+    this_module = backtrace_print_frame (target, frame_num, cur_pc, cur_fp)
+    print_stack_frame (process, cur_fp)
+    print ""
+    if this_module != None:
+      module_list.append (this_module)
+    frame_num = frame_num + 1
+    next_pc = 0
+    next_fp = 0
+    if target.triple[0:6] == "x86_64" or target.triple[0:4] == "i386" or target.triple[0:3] == "arm":
+      error = lldb.SBError()
+      next_pc = process.ReadPointerFromMemory(cur_fp + process.GetAddressByteSize(), error)
+      if not error.Success():
+        next_pc = 0
+      next_fp = process.ReadPointerFromMemory(cur_fp, error)
+      if not error.Success():
+        next_fp = 0
+    # Clear the 0th bit for arm frames - this indicates it is a thumb frame
+    if target.triple[0:3] == "arm" and (next_pc & 1) == 1:
+      next_pc = next_pc & ~1
+    cur_pc = next_pc
+    cur_fp = next_fp
+  this_module = backtrace_print_frame (target, frame_num, cur_pc, cur_fp)
+  print_stack_frame (process, cur_fp)
+  print ""
+  if this_module != None:
+    module_list.append (this_module)
+  return [module_list, address_list]
+
+def print_stack_frame(process, fp):
+  if fp == 0 or fp == lldb.LLDB_INVALID_ADDRESS or fp == 1:
+    return
+  addr_size = process.GetAddressByteSize()
+  addr = fp - (2 * addr_size)
+  i = 0
+  outline = "Stack frame from $fp-%d: " % (2 * addr_size)
+  error = lldb.SBError()
+  try:
+    while i < 5 and error.Success():
+      address = process.ReadPointerFromMemory(addr + (i * addr_size), error)
+      outline += " 0x%x" % address
+      i += 1
+    print outline
+  except Exception:
+    return
+
+def diagnose_unwind(debugger, command, result, dict):
+  """
+Gather diagnostic information to help debug incorrect unwind (backtrace) 
+behavior in lldb.  When there is a backtrace that doesn't look
+correct, run this command with the correct thread selected and a
+large amount of diagnostic information will be printed, it is likely
+to be helpful when reporting the problem.
+  """
+
+  command_args = shlex.split(command)
+  parser = create_diagnose_unwind_options()
+  try:
+    (options, args) = parser.parse_args(command_args)
+  except:
+   return
+  target = debugger.GetSelectedTarget()
+  if target:
+    process = target.GetProcess()
+    if process:
+      thread = process.GetSelectedThread()
+      if thread:
+        lldb_versions_match = re.search(r'[lL][lL][dD][bB]-(\d+)([.](\d+))?([.](\d+))?', debugger.GetVersionString())
+        lldb_version = 0
+        lldb_minor = 0
+        if len(lldb_versions_match.groups()) >= 1 and lldb_versions_match.groups()[0]:
+          lldb_major = int(lldb_versions_match.groups()[0])
+        if len(lldb_versions_match.groups()) >= 5 and lldb_versions_match.groups()[4]:
+          lldb_minor = int(lldb_versions_match.groups()[4])
+
+        modules_seen = []
+        addresses_seen = []
+
+        print 'LLDB version %s' % debugger.GetVersionString()
+        print 'Unwind diagnostics for thread %d' % thread.GetIndexID()
+        print ""
+        print "============================================================================================="
+        print ""
+        print "OS plugin setting:"
+        debugger.HandleCommand("settings show target.process.python-os-plugin-path")
+        print ""
+        print "Live register context:"
+        thread.SetSelectedFrame(0)
+        debugger.HandleCommand("register read")
+        print ""
+        print "============================================================================================="
+        print ""
+        print "lldb's unwind algorithm:"
+        print ""
+        frame_num = 0
+        for frame in thread.frames:
+          if not frame.IsInlined():
+            this_module = backtrace_print_frame (target, frame_num, frame.GetPC(), frame.GetFP())
+            print_stack_frame (process, frame.GetFP())
+            print ""
+            if this_module != None:
+              modules_seen.append (this_module)
+            addresses_seen.append (frame.GetPC())
+            frame_num = frame_num + 1
+        print ""
+        print "============================================================================================="
+        print ""
+        print "Simple stack walk algorithm:"
+        print ""
+        (module_list, address_list) = simple_backtrace(debugger)
+        if module_list and module_list != None:
+          modules_seen += module_list
+        if address_list and address_list != None:
+          addresses_seen = set(addresses_seen)
+          addresses_seen.update(set(address_list))
+
+        print ""
+        print "============================================================================================="
+        print ""
+        print "Modules seen in stack walks:"
+        print ""
+        modules_already_seen = set()
+        for module in modules_seen:
+          if module != None and module.GetFileSpec().GetFilename() != None:
+            if not module.GetFileSpec().GetFilename() in modules_already_seen:
+              debugger.HandleCommand('image list %s' % module.GetFileSpec().GetFilename())
+              modules_already_seen.add(module.GetFileSpec().GetFilename())
+
+        print ""
+        print "============================================================================================="
+        print ""
+        print "Disassembly ofaddresses seen in stack walks:"
+        print ""
+        additional_addresses_to_disassemble = addresses_seen
+        for frame in thread.frames:
+          if not frame.IsInlined():
+            print "--------------------------------------------------------------------------------------"
+            print ""
+            print "Disassembly of %s, frame %d, address 0x%x" % (frame.GetFunctionName(), frame.GetFrameID(), frame.GetPC())
+            print ""
+            if target.triple[0:6] == "x86_64" or target.triple[0:4] == "i386":
+              debugger.HandleCommand('disassemble -F att -a 0x%x' % frame.GetPC())
+            else:
+              debugger.HandleCommand('disassemble -a 0x%x' % frame.GetPC())
+            if frame.GetPC() in additional_addresses_to_disassemble:
+              additional_addresses_to_disassemble.remove (frame.GetPC())
+
+        for address in list(additional_addresses_to_disassemble):
+          print "--------------------------------------------------------------------------------------"
+          print ""
+          print "Disassembly of 0x%x" % address
+          print ""
+          if target.triple[0:6] == "x86_64" or target.triple[0:4] == "i386":
+            debugger.HandleCommand('disassemble -F att -a 0x%x' % address)
+          else:
+            debugger.HandleCommand('disassemble -a 0x%x' % address)
+
+        print ""
+        print "============================================================================================="
+        print ""
+        additional_addresses_to_show_unwind = addresses_seen
+        for frame in thread.frames:
+          if not frame.IsInlined():
+            print "--------------------------------------------------------------------------------------"
+            print ""
+            print "Unwind instructions for %s, frame %d" % (frame.GetFunctionName(), frame.GetFrameID())
+            print ""
+            debugger.HandleCommand('image show-unwind -a "0x%x"' % frame.GetPC())
+            if frame.GetPC() in additional_addresses_to_show_unwind:
+              additional_addresses_to_show_unwind.remove (frame.GetPC())
+
+        for address in list(additional_addresses_to_show_unwind):
+          print "--------------------------------------------------------------------------------------"
+          print ""
+          print "Unwind instructions for 0x%x" % address
+          print ""
+          debugger.HandleCommand('image show-unwind -a "0x%x"' % address)
+
+def create_diagnose_unwind_options():
+  usage = "usage: %prog"
+  description='''Print diagnostic information about a thread backtrace which will help to debug unwind problems'''
+  parser = optparse.OptionParser(description=description, prog='diagnose_unwind',usage=usage)
+  return parser
+
+lldb.debugger.HandleCommand('command script add -f %s.diagnose_unwind diagnose-unwind' % __name__)
+print 'The "diagnose-unwind" command has been installed, type "help diagnose-unwind" for detailed help.'