Debugging WebKit with GDB 7.x

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WebSite: http://www.jjos.org/
作者: 姜江 linuxemacs@gmail.com
QQ: 457283

1. 下载安装最新版本的GDB

a) 获取源码

b) 编译GDB并支持python

2. 使用webkit-tool.py (见附件)

a) 启动gdb后，使用source命令

b) 在调试目标目录下将脚本更名为xxx-gdb.py，然后启动gdb

c) 在.gdbinit中导入脚本

3. 调试方法

a) webkit-dump-document

b) webkit-dump-node

c) webkit-read-breakpoint-from-file

d) webkit-backtrace

e) webkit-setup-collect-node

f) webkit-get-node-objects

4. 样列

###################################################################
# The author of this script is Jiang Jiang <linuxemacs@gmail.com>
# Copyright (C) 2010 by http://www.jjos.org
#                       http://blog.csdn.net/jznsmail
#
# Permission to use, copy, modify, and distribute this script for
# any purpose without fee this hereby granted, provided that this
# entire notice is included in all copies of any software which is
# or includes a copy or modification of this script and in all
# copies of the supporting documentation for such software.
#
# Version: 0.1
#
# Note:
# How to use this gdb script for WebKit debugging?
# 1. you must checkout the latest gdb source code from cvs as below
# cvs -d :pserver:anoncvs@sourceware.org:/cvs/src login
# {enter "anoncvs" as the password}
# cvs -d :pserver:anoncvs@sourceware.org:/cvs/src co gdb
# 2. build latest gdb with python support
# cd gdb-src
# ./configure --with-python
# 3. set up gdb environment
# there are three methods for setup
# a) rename this script to binary-gdb.py (binary replace with your
#    target for debugging)
# b) add this  to  ~/.gdbinit file as follows:
#    python
#    import sys
#    sys.path.insert(0, "/path/to/tools/gdb/")
#    import webkit-tool
# c) start gdb and read this file with source command as follows:
#    source /path/to/tools/gdb/webkit-tool.py
#
# Todo:
# 1. support dump object info to file
# 2. support graphviz for drawing diagram
# 3. support automatically record dump information with file
###################################################################
import gdb
import sys
import re

# WebCore::KURL
WEBCORE_KURL_MEMBER_VAR = [
    'm_string'
]

# WebCore::Frame
WEBCORE_FRAME_MEMBER_VAR = [
    'm_view',
    'm_doc'
]

# WebCore::Document
WEBCORE_DOCUMENT_MEMBER_VAR = [
    'm_frame',
    'm_url',
    'm_docLoader',
    'm_docID'
]

# WebCore::FrameView
WEBCORE_FRAMEVIEW_MEMBER_VAR = [
#    'm_size',
#    'm_margins',
    'm_frame',
#    'm_doFullRepaint',
#    'm_canHaveScrollbars',
#    'm_useSlowRepaints',
#    'm_isOverlapped',
#    'm_contentIsOpaque',
#    'm_slowRepaintObjectCount',
#    'm_layoutTimer',
#    'm_delayedLayout',
#    'm_layoutSchedulingEnabled',
#    'm_midLayout',
#    'm_layoutCount',
#    'm_nestedLayoutCount',
#    'm_postLayoutTasksTimer',
#    'm_firstLayoutCallbackPending',
#    'm_firstLayout',
#    'm_isTransparent',
#    'm_baseBackgroundColor',
#    'm_lastLayoutSize',
#    'm_lastZoomFactor',
#    'm_mediaType',
#    'm_enqueueEvents',
#    'm_overflowStatusDirty',
#    'm_horizontalOverflow',
#    'm_verticalOverflow',
#    'm_wasScrolledByUser',
#    'm_inProgrammaticScroll',
#    'm_deferringRepaints',
#    'm_repaintCount',
#    'm_repaintRects',
#    'm_deferredRepaintTimer',
#    'm_deferredRepaintDelay',
#    'm_lastPaintTime',
#    'm_shouldUpdateWhileOffscreen',
#    'm_deferSetNeedsLayouts',
#    'm_setNeedsLayoutWasDeferred',
#    'm_nodeToDraw',
#    'm_paintBehavior',
#    'm_isPainting',
#    'm_isVisuallyNonEmpty',
#    'm_firstVisuallyNonEmptyLayoutCallbackPending',
#    'm_maintainScrollPositionAnchor',
]

# WebCore::Node
WEBCORE_NODE_MEMBER_VAR = [
    "m_document",
    "m_inDocument",
    "m_document",
    "m_previous",
    "m_next",
    "m_renderer",
    "m_styleChange",
    "m_hasId",
    "m_hasClass",
    "m_attached",
    "m_childNeedsStyleRecalc",
    "m_inDocument",
    "m_isLink",
    "m_active",
    "m_hovered",
    "m_inActiveChain",
    "m_inDetach",
    "m_hasRareData",
    "m_parsingChildrenFinished",
]

DUMP_CLASS_TABLE = {
    "WebCore::Frame":WEBCORE_FRAME_MEMBER_VAR,
    "WebCore::Document":WEBCORE_DOCUMENT_MEMBER_VAR,
    "WebCore::FrameView":WEBCORE_FRAMEVIEW_MEMBER_VAR,
    "WebCore::KURL":WEBCORE_KURL_MEMBER_VAR,
    "WebCore::Node":WEBCORE_NODE_MEMBER_VAR,
}

#===========================================================
# Get the pointer of class member variable
# @param thisPtr - the this pointer of specified class
# @param varName - the name of variable
# @return if success then return the pointer of variable
#         else return None
#===========================================================
def getMemberPtr(thisPtr, varName=""):
    try:
        ptr = thisPtr[varName]
        if ptr.type.code == gdb.TYPE_CODE_STRUCT and \
           re.match(r'WTF::(Ref|Own)Ptr<.*>', str(ptr.type)):
            return ptr['m_ptr']
        return ptr
    except RuntimeError:
        if thisPtr.type.code == gdb.TYPE_CODE_STRUCT:
            return thisPtr.address
#        print "No such member variables: %s [%s]" % (varName, thisPtr.type)
        return None

#===========================================================
# Dump the variable of specified class
# @param varName - the variable name
# @param memberPtr - the pointer of variable
# @param prefixStr - the format string for output
# @param depth - the max depth for recursed dump
#===========================================================
def dumpMemberVariable(varName, memberPtr, prefixStr="\t", depth=10):

    if depth <= 0 or str(memberPtr) == "0x0":
        return

    className = hasClassSymbols(memberPtr)
    if None == className:
        return

    if className == "WebCore::String":
        print "%s%s: %s [%s]" %(prefixStr, varName, memberPtr['m_impl']['m_ptr']['m_data'], className)
        return
    elif className == "int" or \
         className == "bool":
        print "%s%s: %s [%s]" % (prefixStr, varName, memberPtr, className)
        return

    if None == getMemberPtr(memberPtr):
        print "%s%s (%s) [%s]" % (prefixStr, varName, memberPtr, str(memberPtr.type))
    else:
        print "%s%s (%s) [%s]" % (prefixStr, varName, getMemberPtr(memberPtr), str(memberPtr.type))
    depth -= 1
    symbols = DUMP_CLASS_TABLE[className]
    for item in symbols:
        ptr = getMemberPtr(memberPtr, item)
        if (None != ptr):
            dumpMemberVariable(item, ptr, prefixStr+"\t", depth)
    pass

#===========================================================
# Dump specified object
# @param className - the class name
# @param thisPtr - the this pointer of specified class
# @param prefixStr - the format string for output
#===========================================================
def dumpObject(className, thisPtr, prefixStr="\t", depth=5):
    symbols = DUMP_CLASS_TABLE[className]
    for item in symbols:
        memberPtr = getMemberPtr(thisPtr, item)
        if None != memberPtr:
            dumpMemberVariable(item, memberPtr, prefixStr, depth)
    pass

#===========================================================
# Utility function for check symbols table
# @param ptr - the pointer of object
# @return if success then return the name of symbol else
#         return None
#===========================================================
def hasClassSymbols(ptr):
    className = str(ptr.type)
    if ptr.type.code == gdb.TYPE_CODE_PTR: # pointer type
        className = str(ptr.type.target())
        if className.startswith("const "):
            className = className[6:]
    if True == DUMP_CLASS_TABLE.has_key(className):
        return className
    if className == "WebCore::String":
        return className
    if className == "int":
        return className
    if className == "bool":
        return className
#    print "@"+className
    return None

#===========================================================
# webkit-dump-document commands for WebKit debugging
# usage: webkit-dump-document pointer
#===========================================================
class WebKitDumpDocument(gdb.Command):
    """
    Dump document object
    """
    def __init__(self):
        super(WebKitDumpDocument, self).__init__("webkit-dump-document",
                                                 gdb.COMMAND_SUPPORT,
                                                 gdb.COMPLETE_NONE,
                                                 True);
    def invoke(self, arg, from_tty):
        try:
            callFrame = gdb.selected_frame()
            if arg == "": # use default value
                arg = 'this'
            ptr = callFrame.read_var(arg)
            print "%s (%s) [%s]" % ("WebCore::Document", ptr, callFrame.find_sal())
            # could not found any symbols for specified class
            className = hasClassSymbols(ptr)
            if None == className:
                return
            dumpObject(className, ptr, "\t")
        except ValueError:
            print "No such variables: %s" % arg
            return

#===========================================================
# webkit-dump-node commands for WebKit debugging
# usage: webkit-dump-node pointer
#===========================================================
class WebKitDumpNode(gdb.Command):
    """
    Dump Node object
    """
    def __init__(self):
        super(WebKitDumpNode, self).__init__("webkit-dump-node",
                                             gdb.COMMAND_SUPPORT,
                                             gdb.COMPLETE_NONE,
                                             True);
    def invoke(self, arg, from_tty):
        try:
            callFrame = gdb.selected_frame()
            if arg == "": # use default value
                arg = 'this'
            ptr = callFrame.read_var(arg)
            print "%s (%s) [%s]" % ("WebCore::Node", ptr, callFrame.find_sal())
            # could not found any symbols for specified class
            className = hasClassSymbols(ptr)
            if None == className:
                return
            dumpObject(className, ptr, "\t")
        except ValueError:
            print "No such variables: %s" % arg
            return

#===========================================================
# webkit-read-bt-file
# Read break point information from file
# usage: webkit-read-bt-file file
#===========================================================
class WebKitReadBreakpointFile(gdb.Command):
    """
    Read breakpoint from file
    """
    def __init__(self):
        super(WebKitReadBreakpointFile, self).__init__("webkit-read-breakpoint-from-file",
                                             gdb.COMMAND_SUPPORT,
                                             gdb.COMPLETE_NONE,
                                             True);
    def invoke(self, arg, from_tty):
        try:
            if arg == "":
                print "no input file"
                return
            btFile = open(arg, "r")
            while 1:
                line = btFile.readline()
                if not line: break
                self.parse(line)
            btFile.close()
            pass
        except:
            print "Can not open %s file" % arg
            return

    def parse(self, line):
        gdb.execute("break " + line.strip())

#===========================================================
# Dump backtrace info
#===========================================================
class WebKitBacktrace(gdb.Command):
    """
    Dump Node object
    """
    def __init__(self):
        super(WebKitBacktrace, self).__init__("webkit-backtrace",
                                             gdb.COMMAND_SUPPORT,
                                             gdb.COMPLETE_NONE,
                                             True);
    def invoke(self, arg, from_tty):
        callFrame = gdb.selected_frame()
        tmpCalls = [""]
        while (callFrame != None):
            if callFrame.is_valid():
                if callFrame.function() == None:
                    tmpCalls.append("0x%x" % (callFrame.pc()))
                else:
                    tmpCalls.append("%s [%s:%s]" % (callFrame.function(), callFrame.find_sal().symtab.filename, callFrame.find_sal().line))
            callFrame = callFrame.older()
        callLen = len(tmpCalls)
        calls = []
        i = callLen - 1
        while i >= 1:
            tabsN = callLen - i - 1
            fmt = ""
            while tabsN > 0:
                fmt += " "
                tabsN -= 1;
            calls.append(fmt + tmpCalls[i])
            i -= 1
        for item in calls:
            print item

NODE_LIVE_OBJECTS = {}

#===========================================================
# utility function to print stack
#===========================================================
def getBacktraceStr(frame):
    callFrame = frame
    tmpCalls = [""]
    while (callFrame != None):
        if callFrame.is_valid():
            if callFrame.function() == None:
                tmpCalls.append("0x%x" % (callFrame.pc()))
            else:
                tmpCalls.append("%s [%s:%s]" % (callFrame.function(), callFrame.find_sal().symtab.filename, callFrame.find_sal().line))
            callFrame = callFrame.older()
        else:
            continue
    callLen = len(tmpCalls)
    calls = []
    i = callLen - 1
    while i >= 1:
        tabsN = callLen - i - 1
        fmt = ""
        while tabsN > 0:
            fmt += " "
            tabsN -= 1;
        calls.append(fmt + tmpCalls[i])
        i -= 1
    return_str = ""
    for item in calls:
        return_str += item + "\n"
    return return_str

#===========================================================
# Utility function to get this pointer from frame
#===========================================================
def getThisPointer(frame):
    """
    Find the this pointer of the frame
    """
    for sym in frame.block():
        if not sym.is_argument:
            continue
        if sym.print_name == "this":
            return frame.read_var(sym)
    return None

#===========================================================
# Live Node object
#===========================================================
class WebKitNodeLiveObject:
    """
    Runtime Node object
    """
    def __init__(self, backtrace, addr):
        self.addr = addr
        self.backtrace = backtrace
    def __repr__(self):
        gdb.execute("print (WebCore::Node*)%s" % self.addr)
        return_val = ""
        node_obj = gdb.parse_and_eval("(WebCore::Node*) %s" % self.addr)
        return_val += "\tprevious: %s\n" % node_obj.dereference()['m_previous']
        return_val += "\tnext: %s\n" % node_obj.dereference()['m_next']
        return_val += "\trender: %s\n" % node_obj.dereference()['m_renderer']
        return_val += "\tdocument: %s\n" % node_obj.dereference()['m_document']
        return_val += "\tactive: %s\n" % node_obj.dereference()['m_active']
        return return_val

#===========================================================
# webkit-setup-collect-node command to prepare recording
# initialization
#===========================================================
class WebKitNodeCollectSetup(gdb.Command):
    def __init__(self):
        super(WebKitNodeCollectSetup, self).__init__("webkit-setup-collect-node",
                                                     gdb.COMMAND_SUPPORT,
                                                     gdb.COMPLETE_NONE,
                                                     True)
    def invoke(self, arg, from_tty):
        NODE_LIVE_OBJECTS = {}
        gdb.execute("break WebCore::Node::Node() if $_webkit_node_object_create_object()")
        gdb.execute("break WebCore::Node::~Node() if $_webkit_node_object_delete_object()")

#===========================================================
# webkit-get-node-objects commad to get all recording node
#===========================================================
class WebKitGetNodeObjects(gdb.Command):
    """
    Dump Node object
    """
    def __init__(self):
        super(WebKitGetNodeObjects, self).__init__("webkit-get-node-objects",
                                             gdb.COMMAND_SUPPORT,
                                             gdb.COMPLETE_NONE,
                                             True);
    def invoke(self, arg, from_tty):
        if arg != "":
            gdb.execute("set logging file %s" % arg)
            gdb.execute("set logging on")
        for obj in NODE_LIVE_OBJECTS.keys():
            print NODE_LIVE_OBJECTS[obj]
        if arg != "":
            gdb.execute("set logging off")

#===========================================================
# internal function to recording created node object
#===========================================================
class WebKitNodeObjectCreated(gdb.Function):
    def __init__(self):
        super(WebKitNodeObjectCreated, self).__init__("_webkit_node_object_create_object")
    def invoke(self):
        thisPtr = getThisPointer(gdb.selected_frame())
        if thisPtr and NODE_LIVE_OBJECTS.has_key(str(thisPtr)) == False:
            NODE_LIVE_OBJECTS[str(thisPtr)] = WebKitNodeLiveObject(gdb.selected_frame(), thisPtr)
        return False

#===========================================================
# internal function for recording removed node object
#===========================================================
class WebKitNodeObjectDeleted(gdb.Function):
    def __init__(self):
        super(WebKitNodeObjectDeleted, self).__init__("_webkit_node_object_delete_object")
    def invoke(self):
        thisPtr = getThisPointer(gdb.selected_frame())
        if thisPtr and NODE_LIVE_OBJECTS.has_key(str(thisPtr)) == True:
            print "DEL: %s" % (str(thisPtr))
            del NODE_LIVE_OBJECTS[str(thisPtr)]
        return False

def initialize():
    gdb.execute("set print object on")
    WebKitNodeCollectSetup()
    WebKitGetNodeObjects()
    WebKitNodeObjectCreated()
    WebKitNodeObjectDeleted()
    WebKitBacktrace()
    WebKitReadBreakpointFile()
    WebKitDumpDocument()
    WebKitDumpNode()

initialize()

Tags: Browser, Debugging, GDB, WebKit