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# Copyright (C) 2010, Google Inc. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
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# * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"""GDB support for WebKit types.
Add this to your gdb by amending your ~/.gdbinit as follows:
python
import sys
sys.path.insert(0, "/path/to/tools/gdb/")
import webkit
"""
from __future__ import print_function
import gdb
import re
import struct
def guess_string_length(ptr):
"""Guess length of string pointed by ptr.
Returns a tuple of (length, an error message).
"""
# Try to guess at the length.
for i in range(0, 2048):
try:
if int((ptr + i).dereference()) == 0:
return i, ''
except RuntimeError:
# We indexed into inaccessible memory; give up.
return i, ' (gdb hit inaccessible memory)'
return 256, ' (gdb found no trailing NUL)'
def ustring_to_string(ptr, length=None):
"""Convert a pointer to UTF-16 data into a Python string encoded with utf-8.
ptr and length are both gdb.Value objects.
If length is unspecified, will guess at the length."""
error_message = ''
if length is None:
length, error_message = guess_string_length(ptr)
else:
length = int(length)
char_vals = [int((ptr + i).dereference()) for i in range(length)]
string = struct.pack('H' * length, *char_vals).decode('utf-16', 'replace').encode('utf-8')
return string + error_message
def lstring_to_string(ptr, length=None):
"""Convert a pointer to LChar* data into a Python (non-Unicode) string.
ptr and length are both gdb.Value objects.
If length is unspecified, will guess at the length."""
error_message = ''
if length is None:
length, error_message = guess_string_length(ptr)
else:
length = int(length)
string = ''.join([chr((ptr + i).dereference()) for i in range(length)])
return string + error_message
class StringPrinter(object):
"Shared code between different string-printing classes"
def __init__(self, val):
self.val = val
def display_hint(self):
return 'string'
class UCharStringPrinter(StringPrinter):
"Print a UChar*; we must guess at the length"
def to_string(self):
return ustring_to_string(self.val)
class LCharStringPrinter(StringPrinter):
"Print a LChar*; we must guess at the length"
def to_string(self):
return lstring_to_string(self.val)
class WTFAtomicStringPrinter(StringPrinter):
"Print a WTF::AtomicString"
def to_string(self):
return self.val['m_string']
class WTFCStringPrinter(StringPrinter):
"Print a WTF::CString"
def to_string(self):
# The CString holds a buffer, which is a refptr to a WTF::CStringBuffer.
buf_ptr = self.val['m_buffer']['m_ptr']
if not buf_ptr:
return 0
data = (buf_ptr + 1).cast(gdb.lookup_type('char').pointer())
length = self.val['m_buffer']['m_ptr']['m_length']
return ''.join([chr((data + i).dereference()) for i in range(length)])
class WTFStringImplPrinter(StringPrinter):
"Print a WTF::StringImpl"
def get_length(self):
return self.val['m_length']
def to_string(self):
chars_start = self.val.address + 1
if self.is_8bit():
return lstring_to_string(chars_start.cast(gdb.lookup_type('char').pointer()),
self.get_length())
return ustring_to_string(chars_start.cast(gdb.lookup_type('UChar').pointer()),
self.get_length())
def is_8bit(self):
return self.val['m_is8Bit']
class WTFStringPrinter(StringPrinter):
"Print a WTF::String"
def stringimpl_ptr(self):
return self.val['m_impl']['m_ptr']
def get_length(self):
if not self.stringimpl_ptr():
return 0
return WTFStringImplPrinter(self.stringimpl_ptr().dereference()).get_length()
def to_string(self):
if not self.stringimpl_ptr():
return '(null)'
return self.stringimpl_ptr().dereference()
class blinkKURLPrinter(StringPrinter):
"Print a blink::KURL"
def to_string(self):
return WTFStringPrinter(self.val['m_string']).to_string()
class blinkLayoutUnitPrinter:
"Print a blink::LayoutUnit"
def __init__(self, val):
self.val = val
def to_string(self):
return "%.14gpx" % (self.val['m_value'] / 64.0)
class blinkLayoutSizePrinter:
"Print a blink::LayoutSize"
def __init__(self, val):
self.val = val
def to_string(self):
return 'LayoutSize(%s, %s)' % (blinkLayoutUnitPrinter(self.val['m_width']).to_string(), blinkLayoutUnitPrinter(self.val['m_height']).to_string())
class blinkLayoutPointPrinter:
"Print a blink::LayoutPoint"
def __init__(self, val):
self.val = val
def to_string(self):
return 'LayoutPoint(%s, %s)' % (blinkLayoutUnitPrinter(self.val['m_x']).to_string(), blinkLayoutUnitPrinter(self.val['m_y']).to_string())
class blinkQualifiedNamePrinter(StringPrinter):
"Print a blink::QualifiedName"
def __init__(self, val):
super(blinkQualifiedNamePrinter, self).__init__(val)
self.prefix_length = 0
self.length = 0
if self.val['m_impl']:
self.prefix_printer = WTFStringPrinter(
self.val['m_impl']['m_ptr']['m_prefix']['m_string'])
self.local_name_printer = WTFStringPrinter(
self.val['m_impl']['m_ptr']['m_localName']['m_string'])
self.prefix_length = self.prefix_printer.get_length()
if self.prefix_length > 0:
self.length = (self.prefix_length + 1 +
self.local_name_printer.get_length())
else:
self.length = self.local_name_printer.get_length()
def get_length(self):
return self.length
def to_string(self):
if self.get_length() == 0:
return "(null)"
else:
if self.prefix_length > 0:
return (self.prefix_printer.to_string() + ":" +
self.local_name_printer.to_string())
else:
return self.local_name_printer.to_string()
class BlinkPixelsAndPercentPrinter:
"Print a blink::PixelsAndPercent value"
def __init__(self, val):
self.val = val
def to_string(self):
return "(%gpx, %g%%)" % (self.val['pixels'], self.val['percent'])
class BlinkLengthPrinter:
"""Print a blink::Length."""
def __init__(self, val):
self.val = val
def to_string(self):
ltype = self.val['m_type']
if self.val['m_isFloat']:
val = self.val['m_floatValue']
else:
val = int(self.val['m_intValue'])
quirk = ''
if self.val['m_quirk']:
quirk = ', quirk=true'
if ltype == 0:
return 'Length(Auto)'
if ltype == 1:
return 'Length(%g%%, Percent%s)' % (val, quirk)
if ltype == 2:
return 'Length(%g, Fixed%s)' % (val, quirk)
if ltype == 3:
return 'Length(Intrinsic)'
if ltype == 4:
return 'Length(MinIntrinsic)'
if ltype == 5:
return 'Length(MinContent)'
if ltype == 6:
return 'Length(MaxContent)'
if ltype == 7:
return 'Length(FillAvailable)'
if ltype == 8:
return 'Length(FitContent)'
if ltype == 9:
# Would like to print pixelsAndPercent() but can't call member
# functions - https://sourceware.org/bugzilla/show_bug.cgi?id=13326
return 'Length(Calculated)'
if ltype == 10:
return 'Length(ExtendToZoom)'
if ltype == 11:
return 'Length(DeviceWidth)'
if ltype == 12:
return 'Length(DeviceHeight)'
if ltype == 13:
return 'Length(MaxSizeNone)'
return 'Length(unknown type %i)' % ltype
class WTFVectorPrinter:
"""Pretty Printer for a WTF::Vector.
The output of this pretty printer is similar to the output of std::vector's
pretty printer, which is bundled in gcc.
Example gdb session should look like:
(gdb) p v
$3 = WTF::Vector of length 7, capacity 16 = {7, 17, 27, 37, 47, 57, 67}
(gdb) set print elements 3
(gdb) p v
$6 = WTF::Vector of length 7, capacity 16 = {7, 17, 27...}
(gdb) set print array
(gdb) p v
$7 = WTF::Vector of length 7, capacity 16 = {
7,
17,
27
...
}
(gdb) set print elements 200
(gdb) p v
$8 = WTF::Vector of length 7, capacity 16 = {
7,
17,
27,
37,
47,
57,
67
}
"""
class Iterator:
def __init__(self, start, finish):
self.item = start
self.finish = finish
self.count = 0
def __iter__(self):
return self
def next(self):
if self.item == self.finish:
raise StopIteration
count = self.count
self.count += 1
element = self.item.dereference()
self.item += 1
return ('[%d]' % count, element)
def __init__(self, val):
self.val = val
def children(self):
start = self.val['m_buffer']
return self.Iterator(start, start + self.val['m_size'])
def to_string(self):
return ('%s of length %d, capacity %d'
% ('WTF::Vector', self.val['m_size'], self.val['m_capacity']))
def display_hint(self):
return 'array'
# Copied from //tools/gdb/gdb_chrome.py
def typed_ptr(ptr):
"""Prints a pointer along with its exact type.
By default, gdb would print just the address, which takes more
steps to interpret.
"""
# Returning this as a cast expression surrounded by parentheses
# makes it easier to cut+paste inside of gdb.
return '((%s)%s)' % (ptr.dynamic_type, ptr)
class WTFRefOrOwnPtrPrinter:
def __init__(self, val):
self.val = val
def to_string(self):
type_without_param = re.sub(r'<.*>', '', self.val.type.name)
return '%s%s' % (type_without_param, typed_ptr(self.val['m_ptr']))
class BlinkDataRefPrinter:
def __init__(self, val):
self.val = val
def to_string(self):
return 'DataRef(%s)' % (
WTFRefOrOwnPtrPrinter(self.val['m_data']).to_string())
def add_pretty_printers():
pretty_printers = (
(re.compile("^WTF::Vector<.*>$"), WTFVectorPrinter),
(re.compile("^WTF::AtomicString$"), WTFAtomicStringPrinter),
(re.compile("^WTF::CString$"), WTFCStringPrinter),
(re.compile("^WTF::String$"), WTFStringPrinter),
(re.compile("^WTF::StringImpl$"), WTFStringImplPrinter),
(re.compile("^blink::KURL$"), blinkKURLPrinter),
(re.compile("^blink::LayoutUnit$"), blinkLayoutUnitPrinter),
(re.compile("^blink::LayoutPoint$"), blinkLayoutPointPrinter),
(re.compile("^blink::LayoutSize$"), blinkLayoutSizePrinter),
(re.compile("^blink::QualifiedName$"), blinkQualifiedNamePrinter),
(re.compile("^blink::PixelsAndPercent$"), BlinkPixelsAndPercentPrinter),
(re.compile("^blink::Length$"), BlinkLengthPrinter),
(re.compile("^WTF::(Ref|Own)Ptr<.*>$"), WTFRefOrOwnPtrPrinter),
(re.compile("^blink::DataRef<.*>$"), BlinkDataRefPrinter),
)
def lookup_function(val):
"""Function used to load pretty printers; will be passed to GDB."""
type = val.type
if type.code == gdb.TYPE_CODE_REF:
type = type.target()
type = type.unqualified().strip_typedefs()
tag = type.tag
if tag:
for function, pretty_printer in pretty_printers:
if function.search(tag):
return pretty_printer(val)
if type.code == gdb.TYPE_CODE_PTR:
name = str(type.target().unqualified())
if name == 'UChar':
return UCharStringPrinter(val)
if name == 'LChar':
return LCharStringPrinter(val)
return None
gdb.pretty_printers.append(lookup_function)
add_pretty_printers()
class PrintPathToRootCommand(gdb.Command):
"""Command for printing WebKit Node trees.
Usage: printpathtoroot variable_name"""
def __init__(self):
super(PrintPathToRootCommand, self).__init__("printpathtoroot",
gdb.COMMAND_SUPPORT,
gdb.COMPLETE_NONE)
def invoke(self, arg, from_tty):
element_type = gdb.lookup_type('blink::Element')
node_type = gdb.lookup_type('blink::Node')
frame = gdb.selected_frame()
try:
val = gdb.Frame.read_var(frame, arg)
except:
print("No such variable, or invalid type")
return
target_type = str(val.type.target().strip_typedefs())
if target_type == str(node_type):
stack = []
while val:
stack.append([val,
val.cast(element_type.pointer()).dereference()['m_tagName']])
val = val.dereference()['m_parent']
padding = ''
while len(stack) > 0:
pair = stack.pop()
print(padding, pair[1], pair[0])
padding = padding + ' '
else:
print('Sorry: I don\'t know how to deal with %s yet.' % target_type)
PrintPathToRootCommand()