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# Copyright 2014 the V8 project authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
# Print tagged object.
define job
call (void) _v8_internal_Print_Object((void*)($arg0))
end
document job
Print a v8 JavaScript object
Usage: job tagged_ptr
end
# Print content of V8 handles.
python
import gdb
class PrintV8HandleCommand(gdb.Command):
"""Print content of a V8 object, accessed through a handle."""
def __init__(self, command_name):
self.command_name = command_name
super(PrintV8HandleCommand, self).__init__(command_name, gdb.COMMAND_DATA)
@staticmethod
def print_direct(value, from_tty):
CMD = "call (void) _v8_internal_Print_Object((v8::internal::Address*)({}))"
gdb.execute(CMD.format(value.format_string()), from_tty)
return True
@staticmethod
def print_indirect(value, from_tty):
CMD = "call (void) _v8_internal_Print_Object(*(v8::internal::Address**)({}))"
gdb.execute(CMD.format(value.format_string()), from_tty)
return True
def invoke(self, arg, from_tty):
argv = gdb.string_to_argv(arg)
if len(argv) != 1:
raise gdb.GdbError("{} takes exactly one argument.".format(
self.command_name))
value = gdb.parse_and_eval(argv[0])
if not self.print_handle(value, from_tty):
raise gdb.GdbError("{} cannot print a value of type {}".format(
self.command_name, value.type))
class PrintV8LocalCommand(PrintV8HandleCommand):
"""Print content of v8::(Maybe)?Local."""
def __init__(self):
super(PrintV8LocalCommand, self).__init__("print-v8-local")
def print_handle(self, value, from_tty):
if gdb.types.get_basic_type(value.type).code != gdb.TYPE_CODE_STRUCT:
return False
# After https://crrev.com/c/4335544, v8::MaybeLocal contains a local_.
if gdb.types.has_field(value.type, "local_"):
value = value["local_"]
# After https://crrev.com/c/4335544, v8::Local contains a location_.
if gdb.types.has_field(value.type, "location_"):
return self.print_indirect(value["location_"], from_tty)
# Before https://crrev.com/c/4335544, v8::Local contained a val_.
if gdb.types.has_field(value.type, "val_"):
return self.print_indirect(value["val_"], from_tty)
# With v8_enable_direct_local=true, v8::Local contains a ptr_.
if gdb.types.has_field(value.type, "ptr_"):
return self.print_direct(value["ptr_"], from_tty)
# We don't know how to print this...
return False
class PrintV8InternalHandleCommand(PrintV8HandleCommand):
"""Print content of v8::internal::(Maybe)?(Direct|Indirect)?Handle."""
def __init__(self):
super(PrintV8InternalHandleCommand, self).__init__("print-v8-internal-handle")
def print_handle(self, value, from_tty):
if gdb.types.get_basic_type(value.type).code != gdb.TYPE_CODE_STRUCT:
return False
# Indirect handles contain a location_.
if gdb.types.has_field(value.type, "location_"):
return self.print_indirect(value["location_"], from_tty)
# Direct handles contain a obj_.
if gdb.types.has_field(value.type, "obj_"):
return self.print_direct(value["obj_"], from_tty)
# We don't know how to print this...
return False
PrintV8LocalCommand()
PrintV8InternalHandleCommand()
end
alias jlh = print-v8-local
alias jl = print-v8-local
alias jh = print-v8-internal-handle
# Print Code objects containing given PC.
define jco
if $argc == 0
call (void) _v8_internal_Print_Code((void*)($pc))
else
call (void) _v8_internal_Print_Code((void*)($arg0))
end
end
document jco
Print a v8 Code object from an internal code address
Usage: jco pc
end
# Print Code objects assembly code surrounding given PC.
define jca
if $argc == 0
call (void) _v8_internal_Print_OnlyCode((void*)($pc), 30)
else
if $argc == 0
call (void) _v8_internal_Print_OnlyCode((void*)($arg0), 30)
else
call (void) _v8_internal_Print_OnlyCode((void*)($arg0), (size_t)($arg1))
end
end
end
document jca
Print a v8 Code object assembly code from an internal code address
Usage: jca pc
end
# Print TransitionTree.
define jtt
call (void) _v8_internal_Print_TransitionTree((void*)($arg0))
end
document jtt
Print the complete transition tree of the given v8 Map.
Usage: jtt tagged_ptr
end
# Print JavaScript stack trace.
define jst
call (void) _v8_internal_Print_StackTrace()
end
document jst
Print the current JavaScript stack trace
Usage: jst
end
# Print TurboFan graph node.
define pn
call _v8_internal_Node_Print((void*)($arg0))
end
document pn
Print a v8 TurboFan graph node
Usage: pn node_address
end
# Skip the JavaScript stack.
define jss
set $js_entry_sp=v8::internal::Isolate::Current()->thread_local_top()->js_entry_sp_
set $rbp=*(void**)$js_entry_sp
set $rsp=$js_entry_sp + 2*sizeof(void*)
set $pc=*(void**)($js_entry_sp+sizeof(void*))
end
document jss
Skip the jitted stack on x64 to where we entered JS last.
Usage: jss
end
# Execute a simulator command.
python
import gdb
class SimCommand(gdb.Command):
"""Sim the current program."""
def __init__ (self):
super (SimCommand, self).__init__ ("sim", gdb.COMMAND_SUPPORT)
def invoke (self, arg, from_tty):
arg_bytes = arg.encode("utf-8") + b'\0'
arg_c_string = gdb.Value(arg_bytes, gdb.lookup_type('char').array(len(arg_bytes) - 1))
cmd_func = gdb.selected_frame().read_var("_v8_internal_Simulator_ExecDebugCommand")
cmd_func(arg_c_string)
SimCommand()
end
# Print stack trace with assertion scopes.
define bta
python
import re
frame_re = re.compile("^#(\d+)\s*(?:0x[a-f\d]+ in )?(.+) \(.+ at (.+)")
assert_re = re.compile("^\s*(\S+) = .+<v8::internal::Per\w+AssertScope<v8::internal::(\S*), (false|true)>")
btl = gdb.execute("backtrace full", to_string = True).splitlines()
for l in btl:
match = frame_re.match(l)
if match:
print("[%-2s] %-60s %-40s" % (match.group(1), match.group(2), match.group(3)))
match = assert_re.match(l)
if match:
if match.group(3) == "false":
prefix = "Disallow"
color = "\033[91m"
else:
prefix = "Allow"
color = "\033[92m"
print("%s -> %s %s (%s)\033[0m" % (color, prefix, match.group(2), match.group(1)))
end
end
document bta
Print stack trace with assertion scopes
Usage: bta
end
# Search for a pointer inside all valid pages.
define space_find
set $space = $arg0
set $current_page = $space->first_page()
while ($current_page != 0)
printf "# Searching in %p - %p\n", $current_page->area_start(), $current_page->area_end()-1
find $current_page->area_start(), $current_page->area_end()-1, $arg1
set $current_page = $current_page->next_page()
end
end
define heap_find
set $heap = v8::internal::Isolate::Current()->heap()
printf "# Searching for %p in old_space ===============================\n", $arg0
space_find $heap->old_space() ($arg0)
printf "# Searching for %p in map_space ===============================\n", $arg0
space_find $heap->map_space() $arg0
printf "# Searching for %p in code_space ===============================\n", $arg0
space_find $heap->code_space() $arg0
end
document heap_find
Find the location of a given address in V8 pages.
Usage: heap_find address
end
# The 'disassembly-flavor' command is only available on i386 and x84_64.
python
try:
gdb.execute("set disassembly-flavor intel")
except gdb.error:
pass
end
# Configuring ASLR may not be possible on some platforms, such running via the
# `rr` debuggger.
python
try:
gdb.execute("set disable-randomization off")
except gdb.error:
pass
end
# Install a handler whenever the debugger stops due to a signal. It walks up the
# stack looking for V8_Dcheck / V8_Fatal / OS::DebugBreak frame and moves the
# frame to the one above it so it's immediately at the line of code that
# triggered the stop condition.
python
def v8_stop_handler(event):
frame = gdb.selected_frame()
select_frame = None
message = None
count = 0
# Limit stack scanning since the frames we look for are near the top anyway,
# and otherwise stack overflows can be very slow.
while frame is not None and count < 10:
count += 1
# If we are in a frame created by gdb (e.g. for `(gdb) call foo()`), gdb
# emits a dummy frame between its stack and the program's stack. Abort the
# walk if we see this frame.
if frame.type() == gdb.DUMMY_FRAME: break
if frame.name() == 'V8_Dcheck':
frame_message = gdb.lookup_symbol('message', frame.block())[0]
if frame_message:
message = frame_message.value(frame).string()
select_frame = frame.older()
break
if frame.name() is not None and frame.name().startswith('V8_Fatal'):
select_frame = frame.older()
if frame.name() == 'v8::base::OS::DebugBreak':
select_frame = frame.older()
frame = frame.older()
if select_frame is not None:
select_frame.select()
gdb.execute('frame')
if message:
print('DCHECK error: {}'.format(message))
gdb.events.stop.connect(v8_stop_handler)
end
# Code imported from chromium/src/tools/gdb/gdbinit
python
import os
import subprocess
import sys
compile_dirs = set()
def get_current_debug_file_directories():
dir = gdb.execute("show debug-file-directory", to_string=True)
dir = dir[
len('The directory where separate debug symbols are searched for is "'
):-len('".') - 1]
return set(dir.split(":"))
def add_debug_file_directory(dir):
# gdb has no function to add debug-file-directory, simulates that by using
# `show debug-file-directory` and `set debug-file-directory <directories>`.
current_dirs = get_current_debug_file_directories()
current_dirs.add(dir)
gdb.execute(
"set debug-file-directory %s" % ":".join(current_dirs), to_string=True)
def newobj_handler(event):
global compile_dirs
compile_dir = os.path.dirname(event.new_objfile.filename)
if not compile_dir:
return
if compile_dir in compile_dirs:
return
compile_dirs.add(compile_dir)
# Add source path
gdb.execute("dir %s" % compile_dir)
# Need to tell the location of .dwo files.
# https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html
# https://crbug.com/603286#c35
add_debug_file_directory(compile_dir)
# Event hook for newly loaded objfiles.
# https://sourceware.org/gdb/onlinedocs/gdb/Events-In-Python.html
gdb.events.new_objfile.connect(newobj_handler)
gdb.execute("set environment V8_GDBINIT_SOURCED=1")
end
### CppGC helpers.
# Print compressed pointer.
define cpcp
call _cppgc_internal_Decompress_Compressed_Pointer((unsigned)($arg0))
end
document cpcp
Prints compressed pointer (raw value) after decompression.
Usage: cpcp compressed_pointer
end
# Print member.
define cpm
call _cppgc_internal_Print_Member((cppgc::internal::MemberBase*)(&$arg0))
end
document cpm
Prints member, compressed or not.
Usage: cpm member
end
# Pretty printer for cppgc::Member.
python
import re
class CppGCMemberPrinter(object):
"""Print cppgc Member types."""
def __init__(self, val, category, pointee_type):
self.val = val
self.category = category
self.pointee_type = pointee_type
def to_string(self):
pointer = gdb.parse_and_eval(
"_cppgc_internal_Uncompress_Member((void*){})".format(
self.val.address))
return "{}Member<{}> pointing to {}".format(
'' if self.category is None else self.category, self.pointee_type,
pointer)
def display_hint(self):
return "{}Member<{}>".format('' if self.category is None else self.category,
self.pointee_type)
def cppgc_pretty_printers(val):
typename = val.type.name or val.type.tag or str(val.type)
regex = re.compile("^(cppgc|blink)::(Weak|Untraced)?Member<(.*)>$")
match = regex.match(typename)
if match is not None:
return CppGCMemberPrinter(
val, category=match.group(2), pointee_type=match.group(3))
# The member type might have been obscured by typedefs and template
# arguments. Fallback to using the underlying type.
real_type = val.type.strip_typedefs()
if (real_type.name is not None and
real_type.name.startswith('cppgc::internal::BasicMember')):
inner_type = real_type.template_argument(0)
return CppGCMemberPrinter(
val, category='Basic', pointee_type=inner_type.name)
return None
gdb.pretty_printers.append(cppgc_pretty_printers)
end