blob: e250f51c1248f4d811cf0c6d837c343f0f7f7f55 [file] [log] [blame]
#
# Copyright OpenEmbedded Contributors
#
# SPDX-License-Identifier: GPL-2.0-only
#
import bb.siggen
import bb.runqueue
import oe
def sstate_rundepfilter(siggen, fn, recipename, task, dep, depname, dataCaches):
# Return True if we should keep the dependency, False to drop it
def isNative(x):
return x.endswith("-native")
def isCross(x):
return "-cross-" in x
def isNativeSDK(x):
return x.startswith("nativesdk-")
def isKernel(mc, fn):
inherits = " ".join(dataCaches[mc].inherits[fn])
return inherits.find("/module-base.bbclass") != -1 or inherits.find("/linux-kernel-base.bbclass") != -1
def isPackageGroup(mc, fn):
inherits = " ".join(dataCaches[mc].inherits[fn])
return "/packagegroup.bbclass" in inherits
def isAllArch(mc, fn):
inherits = " ".join(dataCaches[mc].inherits[fn])
return "/allarch.bbclass" in inherits
def isImage(mc, fn):
return "/image.bbclass" in " ".join(dataCaches[mc].inherits[fn])
depmc, _, deptaskname, depmcfn = bb.runqueue.split_tid_mcfn(dep)
mc, _ = bb.runqueue.split_mc(fn)
# We can skip the rm_work task signature to avoid running the task
# when we remove some tasks from the dependencie chain
# i.e INHERIT:remove = "create-spdx" will trigger the do_rm_work
if task == "do_rm_work":
return False
# (Almost) always include our own inter-task dependencies (unless it comes
# from a mcdepends). The exception is the special
# do_kernel_configme->do_unpack_and_patch dependency from archiver.bbclass.
if recipename == depname and depmc == mc:
if task == "do_kernel_configme" and deptaskname == "do_unpack_and_patch":
return False
return True
# Exclude well defined recipe->dependency
if "%s->%s" % (recipename, depname) in siggen.saferecipedeps:
return False
# Check for special wildcard
if "*->%s" % depname in siggen.saferecipedeps and recipename != depname:
return False
# Don't change native/cross/nativesdk recipe dependencies any further
if isNative(recipename) or isCross(recipename) or isNativeSDK(recipename):
return True
# Only target packages beyond here
# allarch packagegroups are assumed to have well behaved names which don't change between architecures/tunes
if isPackageGroup(mc, fn) and isAllArch(mc, fn) and not isNative(depname):
return False
# Exclude well defined machine specific configurations which don't change ABI
if depname in siggen.abisaferecipes and not isImage(mc, fn):
return False
# Kernel modules are well namespaced. We don't want to depend on the kernel's checksum
# if we're just doing an RRECOMMENDS:xxx = "kernel-module-*", not least because the checksum
# is machine specific.
# Therefore if we're not a kernel or a module recipe (inheriting the kernel classes)
# and we reccomend a kernel-module, we exclude the dependency.
if dataCaches and isKernel(depmc, depmcfn) and not isKernel(mc, fn):
for pkg in dataCaches[mc].runrecs[fn]:
if " ".join(dataCaches[mc].runrecs[fn][pkg]).find("kernel-module-") != -1:
return False
# Default to keep dependencies
return True
def sstate_lockedsigs(d):
sigs = {}
types = (d.getVar("SIGGEN_LOCKEDSIGS_TYPES") or "").split()
for t in types:
siggen_lockedsigs_var = "SIGGEN_LOCKEDSIGS_%s" % t
lockedsigs = (d.getVar(siggen_lockedsigs_var) or "").split()
for ls in lockedsigs:
pn, task, h = ls.split(":", 2)
if pn not in sigs:
sigs[pn] = {}
sigs[pn][task] = [h, siggen_lockedsigs_var]
return sigs
class SignatureGeneratorOEBasicHashMixIn(object):
supports_multiconfig_datacaches = True
def init_rundepcheck(self, data):
self.abisaferecipes = (data.getVar("SIGGEN_EXCLUDERECIPES_ABISAFE") or "").split()
self.saferecipedeps = (data.getVar("SIGGEN_EXCLUDE_SAFE_RECIPE_DEPS") or "").split()
self.lockedsigs = sstate_lockedsigs(data)
self.lockedhashes = {}
self.lockedpnmap = {}
self.lockedhashfn = {}
self.machine = data.getVar("MACHINE")
self.mismatch_msgs = []
self.mismatch_number = 0
self.lockedsigs_msgs = ""
self.unlockedrecipes = (data.getVar("SIGGEN_UNLOCKED_RECIPES") or
"").split()
self.unlockedrecipes = { k: "" for k in self.unlockedrecipes }
self._internal = False
pass
def tasks_resolved(self, virtmap, virtpnmap, dataCache):
# Translate virtual/xxx entries to PN values
newabisafe = []
for a in self.abisaferecipes:
if a in virtpnmap:
newabisafe.append(virtpnmap[a])
else:
newabisafe.append(a)
self.abisaferecipes = newabisafe
newsafedeps = []
for a in self.saferecipedeps:
a1, a2 = a.split("->")
if a1 in virtpnmap:
a1 = virtpnmap[a1]
if a2 in virtpnmap:
a2 = virtpnmap[a2]
newsafedeps.append(a1 + "->" + a2)
self.saferecipedeps = newsafedeps
def rundep_check(self, fn, recipename, task, dep, depname, dataCaches = None):
return sstate_rundepfilter(self, fn, recipename, task, dep, depname, dataCaches)
def get_taskdata(self):
return (self.lockedpnmap, self.lockedhashfn, self.lockedhashes) + super().get_taskdata()
def set_taskdata(self, data):
self.lockedpnmap, self.lockedhashfn, self.lockedhashes = data[:3]
super().set_taskdata(data[3:])
def dump_sigs(self, dataCache, options):
if 'lockedsigs' in options:
sigfile = os.getcwd() + "/locked-sigs.inc"
bb.plain("Writing locked sigs to %s" % sigfile)
self.dump_lockedsigs(sigfile)
return super(bb.siggen.SignatureGeneratorBasicHash, self).dump_sigs(dataCache, options)
def get_taskhash(self, tid, deps, dataCaches):
if tid in self.lockedhashes:
if self.lockedhashes[tid]:
return self.lockedhashes[tid]
else:
return super().get_taskhash(tid, deps, dataCaches)
h = super().get_taskhash(tid, deps, dataCaches)
(mc, _, task, fn) = bb.runqueue.split_tid_mcfn(tid)
recipename = dataCaches[mc].pkg_fn[fn]
self.lockedpnmap[fn] = recipename
self.lockedhashfn[fn] = dataCaches[mc].hashfn[fn]
unlocked = False
if recipename in self.unlockedrecipes:
unlocked = True
else:
def recipename_from_dep(dep):
(depmc, _, _, depfn) = bb.runqueue.split_tid_mcfn(dep)
return dataCaches[depmc].pkg_fn[depfn]
# If any unlocked recipe is in the direct dependencies then the
# current recipe should be unlocked as well.
depnames = [ recipename_from_dep(x) for x in deps if mc == bb.runqueue.mc_from_tid(x)]
if any(x in y for y in depnames for x in self.unlockedrecipes):
self.unlockedrecipes[recipename] = ''
unlocked = True
if not unlocked and recipename in self.lockedsigs:
if task in self.lockedsigs[recipename]:
h_locked = self.lockedsigs[recipename][task][0]
var = self.lockedsigs[recipename][task][1]
self.lockedhashes[tid] = h_locked
self._internal = True
unihash = self.get_unihash(tid)
self._internal = False
#bb.warn("Using %s %s %s" % (recipename, task, h))
if h != h_locked and h_locked != unihash:
self.mismatch_number += 1
self.mismatch_msgs.append('The %s:%s sig is computed to be %s, but the sig is locked to %s in %s'
% (recipename, task, h, h_locked, var))
return h_locked
self.lockedhashes[tid] = False
#bb.warn("%s %s %s" % (recipename, task, h))
return h
def get_stampfile_hash(self, tid):
if tid in self.lockedhashes and self.lockedhashes[tid]:
return self.lockedhashes[tid]
return super().get_stampfile_hash(tid)
def get_unihash(self, tid):
if tid in self.lockedhashes and self.lockedhashes[tid] and not self._internal:
return self.lockedhashes[tid]
return super().get_unihash(tid)
def dump_sigtask(self, fn, task, stampbase, runtime):
tid = fn + ":" + task
if tid in self.lockedhashes and self.lockedhashes[tid]:
return
super(bb.siggen.SignatureGeneratorBasicHash, self).dump_sigtask(fn, task, stampbase, runtime)
def dump_lockedsigs(self, sigfile, taskfilter=None):
types = {}
for tid in self.runtaskdeps:
# Bitbake changed this to a tuple in newer versions
if isinstance(tid, tuple):
tid = tid[1]
if taskfilter:
if not tid in taskfilter:
continue
fn = bb.runqueue.fn_from_tid(tid)
t = self.lockedhashfn[fn].split(" ")[1].split(":")[5]
t = 't-' + t.replace('_', '-')
if t not in types:
types[t] = []
types[t].append(tid)
with open(sigfile, "w") as f:
l = sorted(types)
for t in l:
f.write('SIGGEN_LOCKEDSIGS_%s = "\\\n' % t)
types[t].sort()
sortedtid = sorted(types[t], key=lambda tid: self.lockedpnmap[bb.runqueue.fn_from_tid(tid)])
for tid in sortedtid:
(_, _, task, fn) = bb.runqueue.split_tid_mcfn(tid)
if tid not in self.taskhash:
continue
f.write(" " + self.lockedpnmap[fn] + ":" + task + ":" + self.get_unihash(tid) + " \\\n")
f.write(' "\n')
f.write('SIGGEN_LOCKEDSIGS_TYPES:%s = "%s"' % (self.machine, " ".join(l)))
def dump_siglist(self, sigfile, path_prefix_strip=None):
def strip_fn(fn):
nonlocal path_prefix_strip
if not path_prefix_strip:
return fn
fn_exp = fn.split(":")
if fn_exp[-1].startswith(path_prefix_strip):
fn_exp[-1] = fn_exp[-1][len(path_prefix_strip):]
return ":".join(fn_exp)
with open(sigfile, "w") as f:
tasks = []
for taskitem in self.taskhash:
(fn, task) = taskitem.rsplit(":", 1)
pn = self.lockedpnmap[fn]
tasks.append((pn, task, strip_fn(fn), self.taskhash[taskitem]))
for (pn, task, fn, taskhash) in sorted(tasks):
f.write('%s:%s %s %s\n' % (pn, task, fn, taskhash))
def checkhashes(self, sq_data, missed, found, d):
warn_msgs = []
error_msgs = []
sstate_missing_msgs = []
info_msgs = None
if self.lockedsigs:
if len(self.lockedsigs) > 10:
self.lockedsigs_msgs = "There are %s recipes with locked tasks (%s task(s) have non matching signature)" % (len(self.lockedsigs), self.mismatch_number)
else:
self.lockedsigs_msgs = "The following recipes have locked tasks:"
for pn in self.lockedsigs:
self.lockedsigs_msgs += " %s" % (pn)
for tid in sq_data['hash']:
if tid not in found:
for pn in self.lockedsigs:
taskname = bb.runqueue.taskname_from_tid(tid)
if sq_data['hash'][tid] in iter(self.lockedsigs[pn].values()):
if taskname == 'do_shared_workdir':
continue
sstate_missing_msgs.append("Locked sig is set for %s:%s (%s) yet not in sstate cache?"
% (pn, taskname, sq_data['hash'][tid]))
checklevel = d.getVar("SIGGEN_LOCKEDSIGS_TASKSIG_CHECK")
if checklevel == 'info':
info_msgs = self.lockedsigs_msgs
if checklevel == 'warn' or checklevel == 'info':
warn_msgs += self.mismatch_msgs
elif checklevel == 'error':
error_msgs += self.mismatch_msgs
checklevel = d.getVar("SIGGEN_LOCKEDSIGS_SSTATE_EXISTS_CHECK")
if checklevel == 'warn':
warn_msgs += sstate_missing_msgs
elif checklevel == 'error':
error_msgs += sstate_missing_msgs
if info_msgs:
bb.note(info_msgs)
if warn_msgs:
bb.warn("\n".join(warn_msgs))
if error_msgs:
bb.fatal("\n".join(error_msgs))
class SignatureGeneratorOEBasicHash(SignatureGeneratorOEBasicHashMixIn, bb.siggen.SignatureGeneratorBasicHash):
name = "OEBasicHash"
class SignatureGeneratorOEEquivHash(SignatureGeneratorOEBasicHashMixIn, bb.siggen.SignatureGeneratorUniHashMixIn, bb.siggen.SignatureGeneratorBasicHash):
name = "OEEquivHash"
def init_rundepcheck(self, data):
super().init_rundepcheck(data)
self.server = data.getVar('BB_HASHSERVE')
if not self.server:
bb.fatal("OEEquivHash requires BB_HASHSERVE to be set")
self.method = data.getVar('SSTATE_HASHEQUIV_METHOD')
if not self.method:
bb.fatal("OEEquivHash requires SSTATE_HASHEQUIV_METHOD to be set")
# Insert these classes into siggen's namespace so it can see and select them
bb.siggen.SignatureGeneratorOEBasicHash = SignatureGeneratorOEBasicHash
bb.siggen.SignatureGeneratorOEEquivHash = SignatureGeneratorOEEquivHash
def find_siginfo(pn, taskname, taskhashlist, d):
""" Find signature data files for comparison purposes """
import fnmatch
import glob
if not taskname:
# We have to derive pn and taskname
key = pn
if key.startswith("mc:"):
# mc:<mc>:<pn>:<task>
_, _, pn, taskname = key.split(':', 3)
else:
# <pn>:<task>
pn, taskname = key.split(':', 1)
hashfiles = {}
filedates = {}
def get_hashval(siginfo):
if siginfo.endswith('.siginfo'):
return siginfo.rpartition(':')[2].partition('_')[0]
else:
return siginfo.rpartition('.')[2]
# First search in stamps dir
localdata = d.createCopy()
localdata.setVar('MULTIMACH_TARGET_SYS', '*')
localdata.setVar('PN', pn)
localdata.setVar('PV', '*')
localdata.setVar('PR', '*')
localdata.setVar('EXTENDPE', '')
stamp = localdata.getVar('STAMP')
if pn.startswith("gcc-source"):
# gcc-source shared workdir is a special case :(
stamp = localdata.expand("${STAMPS_DIR}/work-shared/gcc-${PV}-${PR}")
filespec = '%s.%s.sigdata.*' % (stamp, taskname)
foundall = False
import glob
for fullpath in glob.glob(filespec):
match = False
if taskhashlist:
for taskhash in taskhashlist:
if fullpath.endswith('.%s' % taskhash):
hashfiles[taskhash] = fullpath
if len(hashfiles) == len(taskhashlist):
foundall = True
break
else:
try:
filedates[fullpath] = os.stat(fullpath).st_mtime
except OSError:
continue
hashval = get_hashval(fullpath)
hashfiles[hashval] = fullpath
if not taskhashlist or (len(filedates) < 2 and not foundall):
# That didn't work, look in sstate-cache
hashes = taskhashlist or ['?' * 64]
localdata = bb.data.createCopy(d)
for hashval in hashes:
localdata.setVar('PACKAGE_ARCH', '*')
localdata.setVar('TARGET_VENDOR', '*')
localdata.setVar('TARGET_OS', '*')
localdata.setVar('PN', pn)
localdata.setVar('PV', '*')
localdata.setVar('PR', '*')
localdata.setVar('BB_TASKHASH', hashval)
localdata.setVar('SSTATE_CURRTASK', taskname[3:])
swspec = localdata.getVar('SSTATE_SWSPEC')
if taskname in ['do_fetch', 'do_unpack', 'do_patch', 'do_populate_lic', 'do_preconfigure'] and swspec:
localdata.setVar('SSTATE_PKGSPEC', '${SSTATE_SWSPEC}')
elif pn.endswith('-native') or "-cross-" in pn or "-crosssdk-" in pn:
localdata.setVar('SSTATE_EXTRAPATH', "${NATIVELSBSTRING}/")
filespec = '%s.siginfo' % localdata.getVar('SSTATE_PKG')
matchedfiles = glob.glob(filespec)
for fullpath in matchedfiles:
actual_hashval = get_hashval(fullpath)
if actual_hashval in hashfiles:
continue
hashfiles[hashval] = fullpath
if not taskhashlist:
try:
filedates[fullpath] = os.stat(fullpath).st_mtime
except:
continue
if taskhashlist:
return hashfiles
else:
return filedates
bb.siggen.find_siginfo = find_siginfo
def sstate_get_manifest_filename(task, d):
"""
Return the sstate manifest file path for a particular task.
Also returns the datastore that can be used to query related variables.
"""
d2 = d.createCopy()
extrainf = d.getVarFlag("do_" + task, 'stamp-extra-info')
if extrainf:
d2.setVar("SSTATE_MANMACH", extrainf)
return (d2.expand("${SSTATE_MANFILEPREFIX}.%s" % task), d2)
def find_sstate_manifest(taskdata, taskdata2, taskname, d, multilibcache):
d2 = d
variant = ''
curr_variant = ''
if d.getVar("BBEXTENDCURR") == "multilib":
curr_variant = d.getVar("BBEXTENDVARIANT")
if "virtclass-multilib" not in d.getVar("OVERRIDES"):
curr_variant = "invalid"
if taskdata2.startswith("virtual:multilib"):
variant = taskdata2.split(":")[2]
if curr_variant != variant:
if variant not in multilibcache:
multilibcache[variant] = oe.utils.get_multilib_datastore(variant, d)
d2 = multilibcache[variant]
if taskdata.endswith("-native"):
pkgarchs = ["${BUILD_ARCH}", "${BUILD_ARCH}_${ORIGNATIVELSBSTRING}"]
elif taskdata.startswith("nativesdk-"):
pkgarchs = ["${SDK_ARCH}_${SDK_OS}", "allarch"]
elif "-cross-canadian" in taskdata:
pkgarchs = ["${SDK_ARCH}_${SDK_ARCH}-${SDKPKGSUFFIX}"]
elif "-cross-" in taskdata:
pkgarchs = ["${BUILD_ARCH}"]
elif "-crosssdk" in taskdata:
pkgarchs = ["${BUILD_ARCH}_${SDK_ARCH}_${SDK_OS}"]
else:
pkgarchs = ['${MACHINE_ARCH}']
pkgarchs = pkgarchs + list(reversed(d2.getVar("PACKAGE_EXTRA_ARCHS").split()))
pkgarchs.append('allarch')
pkgarchs.append('${SDK_ARCH}_${SDK_ARCH}-${SDKPKGSUFFIX}')
searched_manifests = []
for pkgarch in pkgarchs:
manifest = d2.expand("${SSTATE_MANIFESTS}/manifest-%s-%s.%s" % (pkgarch, taskdata, taskname))
if os.path.exists(manifest):
return manifest, d2
searched_manifests.append(manifest)
bb.fatal("The sstate manifest for task '%s:%s' (multilib variant '%s') could not be found.\nThe pkgarchs considered were: %s.\nBut none of these manifests exists:\n %s"
% (taskdata, taskname, variant, d2.expand(", ".join(pkgarchs)),"\n ".join(searched_manifests)))
return None, d2
def OEOuthashBasic(path, sigfile, task, d):
"""
Basic output hash function
Calculates the output hash of a task by hashing all output file metadata,
and file contents.
"""
import hashlib
import stat
import pwd
import grp
import re
import fnmatch
def update_hash(s):
s = s.encode('utf-8')
h.update(s)
if sigfile:
sigfile.write(s)
h = hashlib.sha256()
prev_dir = os.getcwd()
corebase = d.getVar("COREBASE")
tmpdir = d.getVar("TMPDIR")
include_owners = os.environ.get('PSEUDO_DISABLED') == '0'
if "package_write_" in task or task == "package_qa":
include_owners = False
include_timestamps = False
include_root = True
if task == "package":
include_timestamps = True
include_root = False
hash_version = d.getVar('HASHEQUIV_HASH_VERSION')
extra_sigdata = d.getVar("HASHEQUIV_EXTRA_SIGDATA")
filemaps = {}
for m in (d.getVar('SSTATE_HASHEQUIV_FILEMAP') or '').split():
entry = m.split(":")
if len(entry) != 3 or entry[0] != task:
continue
filemaps.setdefault(entry[1], [])
filemaps[entry[1]].append(entry[2])
try:
os.chdir(path)
basepath = os.path.normpath(path)
update_hash("OEOuthashBasic\n")
if hash_version:
update_hash(hash_version + "\n")
if extra_sigdata:
update_hash(extra_sigdata + "\n")
# It is only currently useful to get equivalent hashes for things that
# can be restored from sstate. Since the sstate object is named using
# SSTATE_PKGSPEC and the task name, those should be included in the
# output hash calculation.
update_hash("SSTATE_PKGSPEC=%s\n" % d.getVar('SSTATE_PKGSPEC'))
update_hash("task=%s\n" % task)
for root, dirs, files in os.walk('.', topdown=True):
# Sort directories to ensure consistent ordering when recursing
dirs.sort()
files.sort()
def process(path):
s = os.lstat(path)
if stat.S_ISDIR(s.st_mode):
update_hash('d')
elif stat.S_ISCHR(s.st_mode):
update_hash('c')
elif stat.S_ISBLK(s.st_mode):
update_hash('b')
elif stat.S_ISSOCK(s.st_mode):
update_hash('s')
elif stat.S_ISLNK(s.st_mode):
update_hash('l')
elif stat.S_ISFIFO(s.st_mode):
update_hash('p')
else:
update_hash('-')
def add_perm(mask, on, off='-'):
if mask & s.st_mode:
update_hash(on)
else:
update_hash(off)
add_perm(stat.S_IRUSR, 'r')
add_perm(stat.S_IWUSR, 'w')
if stat.S_ISUID & s.st_mode:
add_perm(stat.S_IXUSR, 's', 'S')
else:
add_perm(stat.S_IXUSR, 'x')
if include_owners:
# Group/other permissions are only relevant in pseudo context
add_perm(stat.S_IRGRP, 'r')
add_perm(stat.S_IWGRP, 'w')
if stat.S_ISGID & s.st_mode:
add_perm(stat.S_IXGRP, 's', 'S')
else:
add_perm(stat.S_IXGRP, 'x')
add_perm(stat.S_IROTH, 'r')
add_perm(stat.S_IWOTH, 'w')
if stat.S_ISVTX & s.st_mode:
update_hash('t')
else:
add_perm(stat.S_IXOTH, 'x')
try:
update_hash(" %10s" % pwd.getpwuid(s.st_uid).pw_name)
update_hash(" %10s" % grp.getgrgid(s.st_gid).gr_name)
except KeyError as e:
msg = ("KeyError: %s\nPath %s is owned by uid %d, gid %d, which doesn't match "
"any user/group on target. This may be due to host contamination." %
(e, os.path.abspath(path), s.st_uid, s.st_gid))
raise Exception(msg).with_traceback(e.__traceback__)
if include_timestamps:
update_hash(" %10d" % s.st_mtime)
update_hash(" ")
if stat.S_ISBLK(s.st_mode) or stat.S_ISCHR(s.st_mode):
update_hash("%9s" % ("%d.%d" % (os.major(s.st_rdev), os.minor(s.st_rdev))))
else:
update_hash(" " * 9)
filterfile = False
for entry in filemaps:
if fnmatch.fnmatch(path, entry):
filterfile = True
update_hash(" ")
if stat.S_ISREG(s.st_mode) and not filterfile:
update_hash("%10d" % s.st_size)
else:
update_hash(" " * 10)
update_hash(" ")
fh = hashlib.sha256()
if stat.S_ISREG(s.st_mode):
# Hash file contents
if filterfile:
# Need to ignore paths in crossscripts and postinst-useradd files.
with open(path, 'rb') as d:
chunk = d.read()
chunk = chunk.replace(bytes(basepath, encoding='utf8'), b'')
for entry in filemaps:
if not fnmatch.fnmatch(path, entry):
continue
for r in filemaps[entry]:
if r.startswith("regex-"):
chunk = re.sub(bytes(r[6:], encoding='utf8'), b'', chunk)
else:
chunk = chunk.replace(bytes(r, encoding='utf8'), b'')
fh.update(chunk)
else:
with open(path, 'rb') as d:
for chunk in iter(lambda: d.read(4096), b""):
fh.update(chunk)
update_hash(fh.hexdigest())
else:
update_hash(" " * len(fh.hexdigest()))
update_hash(" %s" % path)
if stat.S_ISLNK(s.st_mode):
update_hash(" -> %s" % os.readlink(path))
update_hash("\n")
# Process this directory and all its child files
if include_root or root != ".":
process(root)
for f in files:
if f == 'fixmepath':
continue
process(os.path.join(root, f))
for dir in dirs:
if os.path.islink(os.path.join(root, dir)):
process(os.path.join(root, dir))
finally:
os.chdir(prev_dir)
return h.hexdigest()