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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. <rdar://problem/13679300> llvm-svn: 180077
This commit is contained in:
Jason Molenda
197
lldb/examples/python/unwind_diagnose.py
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197
lldb/examples/python/unwind_diagnose.py
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#!/usr/bin/python
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# This implements the unwind-diagnose command, usually installed in the debug session like
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# script import lldb.macosx
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# it is used when lldb's backtrace fails -- it collects and prints information about the stack frames,
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# and tries an alternate unwind algorithm, that will help to understand why lldb's unwind algorithm did
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# not succeed.
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import commands
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import optparse
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import os
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import platform
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import re
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import shlex
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import sys
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try:
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# Just try for LLDB in case PYTHONPATH is already correctly setup
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import lldb
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except ImportError:
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lldb_python_dirs = list()
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# lldb is not in the PYTHONPATH, try some defaults for the current platform
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platform_system = platform.system()
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if platform_system == 'Darwin':
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# On Darwin, try the currently selected Xcode directory
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xcode_dir = commands.getoutput("xcode-select --print-path")
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if xcode_dir:
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lldb_python_dirs.append(os.path.realpath(xcode_dir + '/../SharedFrameworks/LLDB.framework/Resources/Python'))
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lldb_python_dirs.append(xcode_dir + '/Library/PrivateFrameworks/LLDB.framework/Resources/Python')
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lldb_python_dirs.append('/System/Library/PrivateFrameworks/LLDB.framework/Resources/Python')
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success = False
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for lldb_python_dir in lldb_python_dirs:
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if os.path.exists(lldb_python_dir):
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if not (sys.path.__contains__(lldb_python_dir)):
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sys.path.append(lldb_python_dir)
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try:
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import lldb
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except ImportError:
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pass
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else:
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print 'imported lldb from: "%s"' % (lldb_python_dir)
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success = True
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break
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if not success:
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print "error: couldn't locate the 'lldb' module, please set PYTHONPATH correctly"
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sys.exit(1)
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# Print the frame number, pc, frame pointer, module UUID and function name
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def backtrace_print_frame (target, frame_num, addr, fp):
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process = target.GetProcess()
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addr_for_printing = addr
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if frame_num > 0:
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addr = addr - 1
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sbaddr = lldb.SBAddress()
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sbaddr.SetLoadAddress(addr, target)
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module_description = ""
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if sbaddr.GetModule():
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module_filename = ""
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module_uuid_str = sbaddr.GetModule().GetUUIDString()
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if module_uuid_str == None:
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module_uuid_str = ""
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if sbaddr.GetModule().GetFileSpec():
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module_filename = sbaddr.GetModule().GetFileSpec().GetFilename()
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if module_filename == None:
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module_filename = ""
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if module_uuid_str != "" or module_filename != "":
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module_description = '%s %s' % (module_filename, module_uuid_str)
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addr_width = process.GetAddressByteSize() * 2
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sym_ctx = target.ResolveSymbolContextForAddress(sbaddr, lldb.eSymbolContextEverything)
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if sym_ctx.IsValid() and sym_ctx.GetSymbol().IsValid():
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function_start = sym_ctx.GetSymbol().GetStartAddress().GetLoadAddress(target)
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offset = addr - function_start
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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)
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else:
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print '%2d: pc==0x%-*x fp==0x%-*x %s' % (frame_num, addr_width, addr_for_printing, addr_width, fp, module_description)
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# A simple stack walk algorithm that follows the frame chain after the first two frames.
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def simple_backtrace(debugger):
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target = debugger.GetSelectedTarget()
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process = target.GetProcess()
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cur_thread = process.GetSelectedThread()
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backtrace_print_frame (target, 0, cur_thread.GetFrameAtIndex(0).GetPC(), cur_thread.GetFrameAtIndex(0).GetFP())
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if cur_thread.GetNumFrames() < 2:
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return
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cur_fp = cur_thread.GetFrameAtIndex(1).GetFP()
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cur_pc = cur_thread.GetFrameAtIndex(1).GetPC()
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# If the pseudoreg "fp" isn't recognized, on arm hardcode to r7 which is correct for Darwin programs.
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if cur_fp == lldb.LLDB_INVALID_ADDRESS and target.triple[0:3] == "arm":
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for reggroup in cur_thread.GetFrameAtIndex(1).registers:
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if reggroup.GetName() == "General Purpose Registers":
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for reg in reggroup:
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if reg.GetName() == "r7":
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cur_fp = int (reg.GetValue(), 16)
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frame_num = 1
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while cur_pc != 0 and cur_fp != 0 and cur_pc != lldb.LLDB_INVALID_ADDRESS and cur_fp != lldb.LLDB_INVALID_ADDRESS:
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backtrace_print_frame (target, frame_num, cur_pc, cur_fp)
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frame_num = frame_num + 1
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next_pc = 0
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next_fp = 0
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if target.triple[0:6] == "x86_64" or target.triple[0:4] == "i386" or target.triple[0:3] == "arm":
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error = lldb.SBError()
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next_pc = process.ReadPointerFromMemory(cur_fp + process.GetAddressByteSize(), error)
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if not error.Success():
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next_pc = 0
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next_fp = process.ReadPointerFromMemory(cur_fp, error)
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if not error.Success():
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next_fp = 0
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# Clear the 0th bit for arm frames - this indicates it is a thumb frame
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if target.triple[0:3] == "arm" and (next_pc & 1) == 1:
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next_pc = next_pc & ~1
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cur_pc = next_pc
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cur_fp = next_fp
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backtrace_print_frame (target, frame_num, cur_pc, cur_fp)
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def unwind_diagnose(debugger, command, result, dict):
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# Use the Shell Lexer to properly parse up command options just like a
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# shell would
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command_args = shlex.split(command)
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parser = create_unwind_diagnose_options()
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try:
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(options, args) = parser.parse_args(command_args)
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except:
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return
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target = debugger.GetSelectedTarget()
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if target:
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process = target.GetProcess()
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if process:
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thread = process.GetSelectedThread()
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if thread:
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lldb_versions_match = re.search(r'lldb-(\d+)([.](\d+))?([.](\d+))?', debugger.GetVersionString())
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lldb_version = 0
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lldb_minor = 0
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if len(lldb_versions_match.groups()) >= 1:
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lldb_major = lldb_versions_match.groups(1)
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if len(lldb_versions_match.groups()) >= 5:
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lldb_minor = lldb_versions_match.groups(5)
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print 'Unwind diagnostics for thread %d' % thread.GetIndexID()
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print ""
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print "lldb's unwind algorithm:"
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print ""
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frame_num = 0
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for frame in thread.frames:
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if not frame.IsInlined():
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backtrace_print_frame (target, frame_num, frame.GetPC(), frame.GetFP())
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frame_num = frame_num + 1
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print ""
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print "============================================================================================="
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print ""
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print "Simple stack walk algorithm:"
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print ""
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simple_backtrace(debugger)
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print ""
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print "============================================================================================="
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print ""
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for frame in thread.frames:
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if not frame.IsInlined():
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print "--------------------------------------------------------------------------------------"
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print ""
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print "Disassembly of %s, frame %d" % (frame.GetFunctionName(), frame.GetFrameID())
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print ""
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if lldb_major > 300 or (lldb_major == 300 and lldb_minor >= 18):
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if target.triple[0:6] == "x86_64" or target.triple[0:4] == "i386":
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debugger.HandleCommand('disassemble -F att -a 0x%x' % frame.GetPC())
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else:
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debugger.HandleCommand('disassemble -a 0x%x' % frame.GetPC())
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else:
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debugger.HandleCommand('disassemble -n "%s"' % frame.GetFunctionName())
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print ""
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print "============================================================================================="
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print ""
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for frame in thread.frames:
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if not frame.IsInlined():
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print "--------------------------------------------------------------------------------------"
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print ""
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print "Unwind instructions for %s, frame %d" % (frame.GetFunctionName(), frame.GetFrameID())
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print ""
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debugger.HandleCommand('image show-unwind -n "%s"' % frame.GetFunctionName())
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def create_unwind_diagnose_options():
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usage = "usage: %prog"
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description='''Print diagnostic information about a thread backtrace which will help to debug unwind problems'''
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parser = optparse.OptionParser(description=description, prog='unwind_diagnose',usage=usage)
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return parser
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if __name__ == '__main__':
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print 'This is not meant to be run from the command line, import it into lldb with a command like "script import lldb.macosx"'
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elif getattr(lldb, 'debugger', None):
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lldb.debugger.HandleCommand('command script add -f lldb.macosx.unwind_diagnose.unwind_diagnose unwind-diagnose')
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print 'The "unwind-diagnose" command has been installed, type "help unwind-diagnose" for detailed help.'
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