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usdt.py
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189 lines (166 loc) · 7.86 KB
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# Copyright 2016 Sasha Goldshtein
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import ctypes as ct
import os, sys
from .libbcc import lib, _USDT_CB, _USDT_PROBE_CB, \
bcc_usdt_location, bcc_usdt_argument, \
BCC_USDT_ARGUMENT_FLAGS
class USDTException(Exception):
pass
class USDTProbeArgument(object):
def __init__(self, argument):
self.signed = argument.size < 0
self.size = abs(argument.size)
self.valid = argument.valid
if self.valid & BCC_USDT_ARGUMENT_FLAGS.CONSTANT != 0:
self.constant = argument.constant
if self.valid & BCC_USDT_ARGUMENT_FLAGS.DEREF_OFFSET != 0:
self.deref_offset = argument.deref_offset
if self.valid & BCC_USDT_ARGUMENT_FLAGS.DEREF_IDENT != 0:
self.deref_ident = argument.deref_ident
if self.valid & BCC_USDT_ARGUMENT_FLAGS.BASE_REGISTER_NAME != 0:
self.base_register_name = argument.base_register_name
if self.valid & BCC_USDT_ARGUMENT_FLAGS.INDEX_REGISTER_NAME != 0:
self.index_register_name = argument.index_register_name
if self.valid & BCC_USDT_ARGUMENT_FLAGS.SCALE != 0:
self.scale = argument.scale
def _size_prefix(self):
return "%d %s bytes" % \
(self.size, "signed " if self.signed else "unsigned")
def _format(self):
# This mimics the logic in cc/usdt_args.cc that gives meaning to the
# various argument settings. A change there will require a change here.
if self.valid & BCC_USDT_ARGUMENT_FLAGS.CONSTANT != 0:
return "%d" % self.constant
if self.valid & BCC_USDT_ARGUMENT_FLAGS.DEREF_OFFSET == 0:
return "%s" % self.base_register_name
if self.valid & BCC_USDT_ARGUMENT_FLAGS.DEREF_OFFSET != 0 and \
self.valid & BCC_USDT_ARGUMENT_FLAGS.DEREF_IDENT == 0:
if self.valid & BCC_USDT_ARGUMENT_FLAGS.INDEX_REGISTER_NAME != 0:
index_offset = " + %s" % self.index_register_name
if self.valid & BCC_USDT_ARGUMENT_FLAGS.SCALE != 0:
index_offset += " * %d" % self.scale
else:
index_offset = ""
sign = '+' if self.deref_offset >= 0 else '-'
return "*(%s %s %d%s)" % (self.base_register_name,
sign, abs(self.deref_offset), index_offset)
if self.valid & BCC_USDT_ARGUMENT_FLAGS.DEREF_OFFSET != 0 and \
self.valid & BCC_USDT_ARGUMENT_FLAGS.DEREF_IDENT != 0 and \
self.valid & BCC_USDT_ARGUMENT_FLAGS.BASE_REGISTER_NAME != 0 and \
self.base_register_name == "ip":
sign = '+' if self.deref_offset >= 0 else '-'
return "*(&%s %s %d)" % (self.deref_ident,
sign, abs(self.deref_offset))
# If we got here, this is an unrecognized case. Doesn't mean it's
# necessarily bad, so just provide the raw data. It just means that
# other tools won't be able to work with this argument.
return "unrecognized argument format, flags %d" % self.valid
def __str__(self):
return "%s @ %s" % (self._size_prefix(), self._format())
class USDTProbeLocation(object):
def __init__(self, probe, index, location):
self.probe = probe
self.index = index
self.num_arguments = probe.num_arguments
self.address = location.address
def __str__(self):
return "0x%x" % self.address
def get_argument(self, index):
arg = bcc_usdt_argument()
res = lib.bcc_usdt_get_argument(self.probe.context, self.probe.name,
self.index, index, ct.pointer(arg))
if res != 0:
raise USDTException(
"error retrieving probe argument %d location %d" %
(index, self.index))
return USDTProbeArgument(arg)
class USDTProbe(object):
def __init__(self, context, probe):
self.context = context
self.provider = probe.provider
self.name = probe.name
self.bin_path = probe.bin_path
self.semaphore = probe.semaphore
self.num_locations = probe.num_locations
self.num_arguments = probe.num_arguments
def __str__(self):
return "%s %s:%s [sema 0x%x]" % \
(self.bin_path, self.provider, self.name, self.semaphore)
def short_name(self):
return "%s:%s" % (self.provider, self.name)
def get_location(self, index):
loc = bcc_usdt_location()
res = lib.bcc_usdt_get_location(self.context, self.name,
index, ct.pointer(loc))
if res != 0:
raise USDTException("error retrieving probe location %d" % index)
return USDTProbeLocation(self, index, loc)
class USDT(object):
def __init__(self, pid=None, path=None):
if pid and pid != -1:
self.pid = pid
self.context = lib.bcc_usdt_new_frompid(pid)
if self.context == None:
raise USDTException("USDT failed to instrument PID %d" % pid)
elif path:
self.path = path
self.context = lib.bcc_usdt_new_frompath(path.encode('ascii'))
if self.context == None:
raise USDTException("USDT failed to instrument path %s" % path)
else:
raise USDTException(
"either a pid or a binary path must be specified")
def enable_probe(self, probe, fn_name):
if lib.bcc_usdt_enable_probe(self.context, probe.encode('ascii'),
fn_name.encode('ascii')) != 0:
raise USDTException(
("failed to enable probe '%s'; a possible cause " +
"can be that the probe requires a pid to enable") %
probe
)
def enable_probe_or_bail(self, probe, fn_name):
if lib.bcc_usdt_enable_probe(self.context, probe.encode('ascii'),
fn_name.encode('ascii')) != 0:
print(
"""Error attaching USDT probes: the specified pid might not contain the
given language's runtime, or the runtime was not built with the required
USDT probes. Look for a configure flag similar to --with-dtrace or
--enable-dtrace. To check which probes are present in the process, use the
tplist tool.""")
sys.exit(1)
def get_context(self):
return self.context
def get_probe_arg_ctype(self, probe_name, arg_index):
return lib.bcc_usdt_get_probe_argctype(
self.context, probe_name, arg_index)
def enumerate_probes(self):
probes = []
def _add_probe(probe):
probes.append(USDTProbe(self.context, probe.contents))
lib.bcc_usdt_foreach(self.context, _USDT_CB(_add_probe))
return probes
# This is called by the BPF module's __init__ when it realizes that there
# is a USDT context and probes need to be attached.
def attach_uprobes(self, bpf):
probes = self.enumerate_active_probes()
for (binpath, fn_name, addr, pid) in probes:
bpf.attach_uprobe(name=binpath.decode(), fn_name=fn_name.decode(),
addr=addr, pid=pid)
def enumerate_active_probes(self):
probes = []
def _add_probe(binpath, fn_name, addr, pid):
probes.append((binpath, fn_name, addr, pid))
lib.bcc_usdt_foreach_uprobe(self.context, _USDT_PROBE_CB(_add_probe))
return probes