From caae381b3501c654f985127a1c3e1bda742ee2a3 Mon Sep 17 00:00:00 2001 From: Jason Molenda Date: Tue, 23 Apr 2013 03:40:32 +0000 Subject: [PATCH] Add a new python file to help diagnose backtrace failures in the field. It will be installed in the LLDB.framework and can be loaded with (lldb) script import lldb.macosx after which a "unwind-diagnose" command will be registered. Select the thread which has a bad backtrace and run this command -- a lot of information about the stack frames, and an alternate backtrace algorithm, will be used. The information will often be sufficient for a remote person to figure out why the backtrace failed. llvm-svn: 180077 --- lldb/examples/python/unwind_diagnose.py | 197 ++++++++++++++++++++++++ 1 file changed, 197 insertions(+) create mode 100644 lldb/examples/python/unwind_diagnose.py diff --git a/lldb/examples/python/unwind_diagnose.py b/lldb/examples/python/unwind_diagnose.py new file mode 100644 index 000000000000..ee2069b9f639 --- /dev/null +++ b/lldb/examples/python/unwind_diagnose.py @@ -0,0 +1,197 @@ +#!/usr/bin/python + +# This implements the unwind-diagnose command, usually installed in the debug session like +# script import lldb.macosx +# 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 commands +import optparse +import os +import platform +import re +import shlex +import sys + +try: + # Just try for LLDB in case PYTHONPATH is already correctly setup + import lldb +except ImportError: + lldb_python_dirs = list() + # lldb is not in the PYTHONPATH, try some defaults for the current platform + platform_system = platform.system() + if platform_system == 'Darwin': + # On Darwin, try the currently selected Xcode directory + xcode_dir = commands.getoutput("xcode-select --print-path") + if xcode_dir: + lldb_python_dirs.append(os.path.realpath(xcode_dir + '/../SharedFrameworks/LLDB.framework/Resources/Python')) + lldb_python_dirs.append(xcode_dir + '/Library/PrivateFrameworks/LLDB.framework/Resources/Python') + lldb_python_dirs.append('/System/Library/PrivateFrameworks/LLDB.framework/Resources/Python') + success = False + for lldb_python_dir in lldb_python_dirs: + if os.path.exists(lldb_python_dir): + if not (sys.path.__contains__(lldb_python_dir)): + sys.path.append(lldb_python_dir) + try: + import lldb + except ImportError: + pass + else: + print 'imported lldb from: "%s"' % (lldb_python_dir) + success = True + break + if not success: + print "error: couldn't locate the 'lldb' module, please set PYTHONPATH correctly" + sys.exit(1) + +# Print the frame number, pc, frame pointer, module UUID and function name +def backtrace_print_frame (target, frame_num, addr, fp): + process = target.GetProcess() + addr_for_printing = addr + if frame_num > 0: + addr = addr - 1 + + sbaddr = lldb.SBAddress() + 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) + + addr_width = process.GetAddressByteSize() * 2 + 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) + +# A simple stack walk algorithm that follows the frame chain after the first two frames. +def simple_backtrace(debugger): + target = debugger.GetSelectedTarget() + process = target.GetProcess() + cur_thread = process.GetSelectedThread() + + backtrace_print_frame (target, 0, cur_thread.GetFrameAtIndex(0).GetPC(), cur_thread.GetFrameAtIndex(0).GetFP()) + if cur_thread.GetNumFrames() < 2: + return + + cur_fp = cur_thread.GetFrameAtIndex(1).GetFP() + cur_pc = cur_thread.GetFrameAtIndex(1).GetPC() + + # If the pseudoreg "fp" isn't recognized, on arm hardcode to r7 which is correct for Darwin programs. + if cur_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": + cur_fp = int (reg.GetValue(), 16) + + 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: + backtrace_print_frame (target, frame_num, cur_pc, cur_fp) + 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 + backtrace_print_frame (target, frame_num, cur_pc, cur_fp) + +def unwind_diagnose(debugger, command, result, dict): + # Use the Shell Lexer to properly parse up command options just like a + # shell would + command_args = shlex.split(command) + parser = create_unwind_diagnose_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'lldb-(\d+)([.](\d+))?([.](\d+))?', debugger.GetVersionString()) + lldb_version = 0 + lldb_minor = 0 + if len(lldb_versions_match.groups()) >= 1: + lldb_major = lldb_versions_match.groups(1) + if len(lldb_versions_match.groups()) >= 5: + lldb_minor = lldb_versions_match.groups(5) + + print 'Unwind diagnostics for thread %d' % thread.GetIndexID() + print "" + print "lldb's unwind algorithm:" + print "" + frame_num = 0 + for frame in thread.frames: + if not frame.IsInlined(): + backtrace_print_frame (target, frame_num, frame.GetPC(), frame.GetFP()) + frame_num = frame_num + 1 + print "" + print "=============================================================================================" + print "" + print "Simple stack walk algorithm:" + print "" + simple_backtrace(debugger) + print "" + print "=============================================================================================" + print "" + for frame in thread.frames: + if not frame.IsInlined(): + print "--------------------------------------------------------------------------------------" + print "" + print "Disassembly of %s, frame %d" % (frame.GetFunctionName(), frame.GetFrameID()) + print "" + if lldb_major > 300 or (lldb_major == 300 and lldb_minor >= 18): + 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()) + else: + debugger.HandleCommand('disassemble -n "%s"' % frame.GetFunctionName()) + print "" + print "=============================================================================================" + print "" + 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 -n "%s"' % frame.GetFunctionName()) + +def create_unwind_diagnose_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='unwind_diagnose',usage=usage) + return parser + +if __name__ == '__main__': + print 'This is not meant to be run from the command line, import it into lldb with a command like "script import lldb.macosx"' +elif getattr(lldb, 'debugger', None): + lldb.debugger.HandleCommand('command script add -f lldb.macosx.unwind_diagnose.unwind_diagnose unwind-diagnose') + print 'The "unwind-diagnose" command has been installed, type "help unwind-diagnose" for detailed help.' -- GitLab