diff --git a/bitbake/lib/bb/siggen.py b/bitbake/lib/bb/siggen.py
new file mode 100644
index 0000000..2985272
--- /dev/null
+++ b/bitbake/lib/bb/siggen.py
@@ -0,0 +1,526 @@
+import hashlib
+import logging
+import os
+import re
+import tempfile
+import bb.data
+
+logger = logging.getLogger('BitBake.SigGen')
+
+try:
+    import cPickle as pickle
+except ImportError:
+    import pickle
+    logger.info('Importing cPickle failed.  Falling back to a very slow implementation.')
+
+def init(d):
+    siggens = [obj for obj in globals().itervalues()
+                      if type(obj) is type and issubclass(obj, SignatureGenerator)]
+
+    desired = d.getVar("BB_SIGNATURE_HANDLER", True) or "noop"
+    for sg in siggens:
+        if desired == sg.name:
+            return sg(d)
+            break
+    else:
+        logger.error("Invalid signature generator '%s', using default 'noop'\n"
+                     "Available generators: %s", desired,
+                     ', '.join(obj.name for obj in siggens))
+        return SignatureGenerator(d)
+
+class SignatureGenerator(object):
+    """
+    """
+    name = "noop"
+
+    def __init__(self, data):
+        self.taskhash = {}
+        self.runtaskdeps = {}
+        self.file_checksum_values = {}
+
+    def finalise(self, fn, d, varient):
+        return
+
+    def get_taskhash(self, fn, task, deps, dataCache):
+        return "0"
+
+    def set_taskdata(self, hashes, deps, checksum):
+        return
+
+    def stampfile(self, stampbase, file_name, taskname, extrainfo):
+        return ("%s.%s.%s" % (stampbase, taskname, extrainfo)).rstrip('.')
+
+    def stampcleanmask(self, stampbase, file_name, taskname, extrainfo):
+        return ("%s.%s.%s" % (stampbase, taskname, extrainfo)).rstrip('.')
+
+    def dump_sigtask(self, fn, task, stampbase, runtime):
+        return
+
+    def invalidate_task(self, task, d, fn):
+        bb.build.del_stamp(task, d, fn)
+
+    def dump_sigs(self, dataCache, options):
+        return
+
+    def get_taskdata(self):
+       return (self.runtaskdeps, self.taskhash, self.file_checksum_values)
+
+    def set_taskdata(self, data):
+        self.runtaskdeps, self.taskhash, self.file_checksum_values = data
+
+
+class SignatureGeneratorBasic(SignatureGenerator):
+    """
+    """
+    name = "basic"
+
+    def __init__(self, data):
+        self.basehash = {}
+        self.taskhash = {}
+        self.taskdeps = {}
+        self.runtaskdeps = {}
+        self.file_checksum_values = {}
+        self.gendeps = {}
+        self.lookupcache = {}
+        self.pkgnameextract = re.compile("(?P<fn>.*)\..*")
+        self.basewhitelist = set((data.getVar("BB_HASHBASE_WHITELIST", True) or "").split())
+        self.taskwhitelist = None
+        self.init_rundepcheck(data)
+
+    def init_rundepcheck(self, data):
+        self.taskwhitelist = data.getVar("BB_HASHTASK_WHITELIST", True) or None
+        if self.taskwhitelist:
+            self.twl = re.compile(self.taskwhitelist)
+        else:
+            self.twl = None
+
+    def _build_data(self, fn, d):
+
+        tasklist, gendeps, lookupcache = bb.data.generate_dependencies(d)
+
+        taskdeps = {}
+        basehash = {}
+
+        for task in tasklist:
+            data = lookupcache[task]
+
+            if data is None:
+                bb.error("Task %s from %s seems to be empty?!" % (task, fn))
+                data = ''
+
+            gendeps[task] -= self.basewhitelist
+            newdeps = gendeps[task]
+            seen = set()
+            while newdeps:
+                nextdeps = newdeps
+                seen |= nextdeps
+                newdeps = set()
+                for dep in nextdeps:
+                    if dep in self.basewhitelist:
+                        continue
+                    gendeps[dep] -= self.basewhitelist
+                    newdeps |= gendeps[dep]
+                newdeps -= seen
+
+            alldeps = sorted(seen)
+            for dep in alldeps:
+                data = data + dep
+                var = lookupcache[dep]
+                if var is not None:
+                    data = data + str(var)
+            self.basehash[fn + "." + task] = hashlib.md5(data).hexdigest()
+            taskdeps[task] = alldeps
+
+        self.taskdeps[fn] = taskdeps
+        self.gendeps[fn] = gendeps
+        self.lookupcache[fn] = lookupcache
+
+        return taskdeps
+
+    def finalise(self, fn, d, variant):
+
+        if variant:
+            fn = "virtual:" + variant + ":" + fn
+
+        try:
+            taskdeps = self._build_data(fn, d)
+        except:
+            bb.note("Error during finalise of %s" % fn)
+            raise
+
+        #Slow but can be useful for debugging mismatched basehashes
+        #for task in self.taskdeps[fn]:
+        #    self.dump_sigtask(fn, task, d.getVar("STAMP", True), False)
+
+        for task in taskdeps:
+            d.setVar("BB_BASEHASH_task-%s" % task, self.basehash[fn + "." + task])
+
+    def rundep_check(self, fn, recipename, task, dep, depname, dataCache):
+        # Return True if we should keep the dependency, False to drop it
+        # We only manipulate the dependencies for packages not in the whitelist
+        if self.twl and not self.twl.search(recipename):
+            # then process the actual dependencies
+            if self.twl.search(depname):
+                return False
+        return True
+
+    def read_taint(self, fn, task, stampbase):
+        taint = None
+        try:
+            with open(stampbase + '.' + task + '.taint', 'r') as taintf:
+                taint = taintf.read()
+        except IOError:
+            pass
+        return taint
+
+    def get_taskhash(self, fn, task, deps, dataCache):
+        k = fn + "." + task
+        data = dataCache.basetaskhash[k]
+        self.runtaskdeps[k] = []
+        self.file_checksum_values[k] = {}
+        recipename = dataCache.pkg_fn[fn]
+        for dep in sorted(deps, key=clean_basepath):
+            depname = dataCache.pkg_fn[self.pkgnameextract.search(dep).group('fn')]
+            if not self.rundep_check(fn, recipename, task, dep, depname, dataCache):
+                continue
+            if dep not in self.taskhash:
+                bb.fatal("%s is not in taskhash, caller isn't calling in dependency order?", dep)
+            data = data + self.taskhash[dep]
+            self.runtaskdeps[k].append(dep)
+
+        if task in dataCache.file_checksums[fn]:
+            checksums = bb.fetch2.get_file_checksums(dataCache.file_checksums[fn][task], recipename)
+            for (f,cs) in checksums:
+                self.file_checksum_values[k][f] = cs
+                if cs:
+                    data = data + cs
+
+        taskdep = dataCache.task_deps[fn]
+        if 'nostamp' in taskdep and task in taskdep['nostamp']:
+            # Nostamp tasks need an implicit taint so that they force any dependent tasks to run
+            import uuid
+            data = data + str(uuid.uuid4())
+
+        taint = self.read_taint(fn, task, dataCache.stamp[fn])
+        if taint:
+            data = data + taint
+            logger.warn("%s is tainted from a forced run" % k)
+
+        h = hashlib.md5(data).hexdigest()
+        self.taskhash[k] = h
+        #d.setVar("BB_TASKHASH_task-%s" % task, taskhash[task])
+        return h
+
+    def dump_sigtask(self, fn, task, stampbase, runtime):
+        k = fn + "." + task
+        if runtime == "customfile":
+            sigfile = stampbase
+        elif runtime and k in self.taskhash:
+            sigfile = stampbase + "." + task + ".sigdata" + "." + self.taskhash[k]
+        else:
+            sigfile = stampbase + "." + task + ".sigbasedata" + "." + self.basehash[k]
+
+        bb.utils.mkdirhier(os.path.dirname(sigfile))
+
+        data = {}
+        data['basewhitelist'] = self.basewhitelist
+        data['taskwhitelist'] = self.taskwhitelist
+        data['taskdeps'] = self.taskdeps[fn][task]
+        data['basehash'] = self.basehash[k]
+        data['gendeps'] = {}
+        data['varvals'] = {}
+        data['varvals'][task] = self.lookupcache[fn][task]
+        for dep in self.taskdeps[fn][task]:
+            if dep in self.basewhitelist:
+                continue
+            data['gendeps'][dep] = self.gendeps[fn][dep]
+            data['varvals'][dep] = self.lookupcache[fn][dep]
+
+        if runtime and k in self.taskhash:
+            data['runtaskdeps'] = self.runtaskdeps[k]
+            data['file_checksum_values'] = [(os.path.basename(f), cs) for f,cs in self.file_checksum_values[k].items()]
+            data['runtaskhashes'] = {}
+            for dep in data['runtaskdeps']:
+                data['runtaskhashes'][dep] = self.taskhash[dep]
+
+        taint = self.read_taint(fn, task, stampbase)
+        if taint:
+            data['taint'] = taint
+
+        fd, tmpfile = tempfile.mkstemp(dir=os.path.dirname(sigfile), prefix="sigtask.")
+        try:
+            with os.fdopen(fd, "wb") as stream:
+                p = pickle.dump(data, stream, -1)
+                stream.flush()
+            os.chmod(tmpfile, 0664)
+            os.rename(tmpfile, sigfile)
+        except (OSError, IOError) as err:
+            try:
+                os.unlink(tmpfile)
+            except OSError:
+                pass
+            raise err
+
+    def dump_sigs(self, dataCache, options):
+        for fn in self.taskdeps:
+            for task in self.taskdeps[fn]:
+                k = fn + "." + task
+                if k not in self.taskhash:
+                    continue
+                if dataCache.basetaskhash[k] != self.basehash[k]:
+                    bb.error("Bitbake's cached basehash does not match the one we just generated (%s)!" % k)
+                    bb.error("The mismatched hashes were %s and %s" % (dataCache.basetaskhash[k], self.basehash[k]))
+                self.dump_sigtask(fn, task, dataCache.stamp[fn], True)
+
+class SignatureGeneratorBasicHash(SignatureGeneratorBasic):
+    name = "basichash"
+
+    def stampfile(self, stampbase, fn, taskname, extrainfo, clean=False):
+        if taskname != "do_setscene" and taskname.endswith("_setscene"):
+            k = fn + "." + taskname[:-9]
+        else:
+            k = fn + "." + taskname
+        if clean:
+            h = "*"
+        elif k in self.taskhash:
+            h = self.taskhash[k]
+        else:
+            # If k is not in basehash, then error
+            h = self.basehash[k]
+        return ("%s.%s.%s.%s" % (stampbase, taskname, h, extrainfo)).rstrip('.')
+
+    def stampcleanmask(self, stampbase, fn, taskname, extrainfo):
+        return self.stampfile(stampbase, fn, taskname, extrainfo, clean=True)
+        
+    def invalidate_task(self, task, d, fn):
+        bb.note("Tainting hash to force rebuild of task %s, %s" % (fn, task))
+        bb.build.write_taint(task, d, fn)
+
+def dump_this_task(outfile, d):
+    import bb.parse
+    fn = d.getVar("BB_FILENAME", True)
+    task = "do_" + d.getVar("BB_CURRENTTASK", True)
+    bb.parse.siggen.dump_sigtask(fn, task, outfile, "customfile")
+
+def clean_basepath(a):
+    b = a.rsplit("/", 2)[1] + a.rsplit("/", 2)[2]
+    if a.startswith("virtual:"):
+        b = b + ":" + a.rsplit(":", 1)[0]
+    return b
+
+def clean_basepaths(a):
+    b = {}
+    for x in a:
+        b[clean_basepath(x)] = a[x]
+    return b
+
+def clean_basepaths_list(a):
+    b = []
+    for x in a:
+        b.append(clean_basepath(x))
+    return b
+
+def compare_sigfiles(a, b, recursecb = None):
+    output = []
+
+    p1 = pickle.Unpickler(open(a, "rb"))
+    a_data = p1.load()
+    p2 = pickle.Unpickler(open(b, "rb"))
+    b_data = p2.load()
+
+    def dict_diff(a, b, whitelist=set()):
+        sa = set(a.keys())
+        sb = set(b.keys())
+        common = sa & sb
+        changed = set()
+        for i in common:
+            if a[i] != b[i] and i not in whitelist:
+                changed.add(i)
+        added = sb - sa
+        removed = sa - sb
+        return changed, added, removed
+
+    def file_checksums_diff(a, b):
+        from collections import Counter
+        # Handle old siginfo format
+        if isinstance(a, dict):
+            a = [(os.path.basename(f), cs) for f, cs in a.items()]
+        if isinstance(b, dict):
+            b = [(os.path.basename(f), cs) for f, cs in b.items()]
+        # Compare lists, ensuring we can handle duplicate filenames if they exist
+        removedcount = Counter(a)
+        removedcount.subtract(b)
+        addedcount = Counter(b)
+        addedcount.subtract(a)
+        added = []
+        for x in b:
+            if addedcount[x] > 0:
+                addedcount[x] -= 1
+                added.append(x)
+        removed = []
+        changed = []
+        for x in a:
+            if removedcount[x] > 0:
+                removedcount[x] -= 1
+                for y in added:
+                    if y[0] == x[0]:
+                        changed.append((x[0], x[1], y[1]))
+                        added.remove(y)
+                        break
+                else:
+                    removed.append(x)
+        added = [x[0] for x in added]
+        removed = [x[0] for x in removed]
+        return changed, added, removed
+
+    if 'basewhitelist' in a_data and a_data['basewhitelist'] != b_data['basewhitelist']:
+        output.append("basewhitelist changed from '%s' to '%s'" % (a_data['basewhitelist'], b_data['basewhitelist']))
+        if a_data['basewhitelist'] and b_data['basewhitelist']:
+            output.append("changed items: %s" % a_data['basewhitelist'].symmetric_difference(b_data['basewhitelist']))
+
+    if 'taskwhitelist' in a_data and a_data['taskwhitelist'] != b_data['taskwhitelist']:
+        output.append("taskwhitelist changed from '%s' to '%s'" % (a_data['taskwhitelist'], b_data['taskwhitelist']))
+        if a_data['taskwhitelist'] and b_data['taskwhitelist']:
+            output.append("changed items: %s" % a_data['taskwhitelist'].symmetric_difference(b_data['taskwhitelist']))
+
+    if a_data['taskdeps'] != b_data['taskdeps']:
+        output.append("Task dependencies changed from:\n%s\nto:\n%s" % (sorted(a_data['taskdeps']), sorted(b_data['taskdeps'])))
+
+    if a_data['basehash'] != b_data['basehash']:
+        output.append("basehash changed from %s to %s" % (a_data['basehash'], b_data['basehash']))
+
+    changed, added, removed = dict_diff(a_data['gendeps'], b_data['gendeps'], a_data['basewhitelist'] & b_data['basewhitelist'])
+    if changed:
+        for dep in changed:
+            output.append("List of dependencies for variable %s changed from '%s' to '%s'" % (dep, a_data['gendeps'][dep], b_data['gendeps'][dep]))
+            if a_data['gendeps'][dep] and b_data['gendeps'][dep]:
+                output.append("changed items: %s" % a_data['gendeps'][dep].symmetric_difference(b_data['gendeps'][dep]))
+    if added:
+        for dep in added:
+            output.append("Dependency on variable %s was added" % (dep))
+    if removed:
+        for dep in removed:
+            output.append("Dependency on Variable %s was removed" % (dep))
+
+
+    changed, added, removed = dict_diff(a_data['varvals'], b_data['varvals'])
+    if changed:
+        for dep in changed:
+            output.append("Variable %s value changed from '%s' to '%s'" % (dep, a_data['varvals'][dep], b_data['varvals'][dep]))
+
+    changed, added, removed = file_checksums_diff(a_data['file_checksum_values'], b_data['file_checksum_values'])
+    if changed:
+        for f, old, new in changed:
+            output.append("Checksum for file %s changed from %s to %s" % (f, old, new))
+    if added:
+        for f in added:
+            output.append("Dependency on checksum of file %s was added" % (f))
+    if removed:
+        for f in removed:
+            output.append("Dependency on checksum of file %s was removed" % (f))
+
+
+    if len(a_data['runtaskdeps']) != len(b_data['runtaskdeps']):
+        changed = ["Number of task dependencies changed"]
+    else:
+        changed = []
+        for idx, task in enumerate(a_data['runtaskdeps']):
+            a = a_data['runtaskdeps'][idx]
+            b = b_data['runtaskdeps'][idx]
+            if a_data['runtaskhashes'][a] != b_data['runtaskhashes'][b]:
+                changed.append("%s with hash %s\n changed to\n%s with hash %s" % (a, a_data['runtaskhashes'][a], b, b_data['runtaskhashes'][b]))
+
+    if changed:
+        output.append("runtaskdeps changed from %s to %s" % (clean_basepaths_list(a_data['runtaskdeps']), clean_basepaths_list(b_data['runtaskdeps'])))
+        output.append("\n".join(changed))
+
+
+    if 'runtaskhashes' in a_data and 'runtaskhashes' in b_data:
+        a = a_data['runtaskhashes']
+        b = b_data['runtaskhashes']
+        changed, added, removed = dict_diff(a, b)
+        if added:
+            for dep in added:
+                bdep_found = False
+                if removed:
+                    for bdep in removed:
+                        if b[dep] == a[bdep]:
+                            #output.append("Dependency on task %s was replaced by %s with same hash" % (dep, bdep))
+                            bdep_found = True
+                if not bdep_found:
+                    output.append("Dependency on task %s was added with hash %s" % (clean_basepath(dep), b[dep]))
+        if removed:
+            for dep in removed:
+                adep_found = False
+                if added:
+                    for adep in added:
+                        if b[adep] == a[dep]:
+                            #output.append("Dependency on task %s was replaced by %s with same hash" % (adep, dep))
+                            adep_found = True
+                if not adep_found:
+                    output.append("Dependency on task %s was removed with hash %s" % (clean_basepath(dep), a[dep]))
+        if changed:
+            for dep in changed:
+                output.append("Hash for dependent task %s changed from %s to %s" % (clean_basepath(dep), a[dep], b[dep]))
+                if callable(recursecb):
+                    # If a dependent hash changed, might as well print the line above and then defer to the changes in 
+                    # that hash since in all likelyhood, they're the same changes this task also saw.
+                    recout = recursecb(dep, a[dep], b[dep])
+                    if recout:
+                        output = [output[-1]] + recout
+
+    a_taint = a_data.get('taint', None)
+    b_taint = b_data.get('taint', None)
+    if a_taint != b_taint:
+        output.append("Taint (by forced/invalidated task) changed from %s to %s" % (a_taint, b_taint))
+
+    return output
+
+
+def dump_sigfile(a):
+    output = []
+
+    p1 = pickle.Unpickler(open(a, "rb"))
+    a_data = p1.load()
+
+    output.append("basewhitelist: %s" % (a_data['basewhitelist']))
+
+    output.append("taskwhitelist: %s" % (a_data['taskwhitelist']))
+
+    output.append("Task dependencies: %s" % (sorted(a_data['taskdeps'])))
+
+    output.append("basehash: %s" % (a_data['basehash']))
+
+    for dep in a_data['gendeps']:
+        output.append("List of dependencies for variable %s is %s" % (dep, a_data['gendeps'][dep]))
+
+    for dep in a_data['varvals']:
+        output.append("Variable %s value is %s" % (dep, a_data['varvals'][dep]))
+
+    if 'runtaskdeps' in a_data:
+        output.append("Tasks this task depends on: %s" % (a_data['runtaskdeps']))
+
+    if 'file_checksum_values' in a_data:
+        output.append("This task depends on the checksums of files: %s" % (a_data['file_checksum_values']))
+
+    if 'runtaskhashes' in a_data:
+        for dep in a_data['runtaskhashes']:
+            output.append("Hash for dependent task %s is %s" % (dep, a_data['runtaskhashes'][dep]))
+
+    if 'taint' in a_data:
+        output.append("Tainted (by forced/invalidated task): %s" % a_data['taint'])
+
+    data = a_data['basehash']
+    for dep in a_data['runtaskdeps']:
+        data = data + a_data['runtaskhashes'][dep]
+
+    for c in a_data['file_checksum_values']:
+        data = data + c[1]
+
+    if 'taint' in a_data:
+        data = data + a_data['taint']
+
+    h = hashlib.md5(data).hexdigest()
+    output.append("Computed Hash is %s" % h)
+
+    return output