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llvm-project/lldb/examples/python/diagnose_unwind.py
Med Ismail Bennani e3930e77fc [lldb] Update custom commands to always be overrriden 
This is a follow-up patch to 6f7835f309b9.

As explained previously, when running from an IDE, it can happen that
the IDE imports some lldb scripts by itself. If the user also tries to
import these commands, lldb will show the following message:

```
error: cannot add command: user command exists and force replace not set
```

This message is confusing to the user, because it suggests that the
command import failed and that the execution should stop. However, in
this case, lldb will continue the execution with the command added
previously by the user.

To prevent that, this patch updates every first-party lldb-packaged
custom commands to override commands that were pre-imported in lldb.

Differential Revision: https://reviews.llvm.org/D140293

Signed-off-by: Med Ismail Bennani <medismail.bennani@gmail.com>
2023-01-12 19:20:51 -08:00

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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 is None:
module_uuid_str = ""
if sbaddr.GetModule().GetFileSpec():
module_filename = sbaddr.GetModule().GetFileSpec().GetFilename()
if module_filename is 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 is not 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 is not 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 is not 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 is not 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 is not None:
modules_seen += module_list
if address_list and address_list is not 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 is not None and module.GetFileSpec().GetFilename() is not 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
def __lldb_init_module(debugger, internal_dict):
debugger.HandleCommand(
'command script add -o -f %s.diagnose_unwind diagnose-unwind' %
__name__)
print('The "diagnose-unwind" command has been installed, type "help diagnose-unwind" for detailed help.')
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