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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.
from __future__ import print_function
import ctypes as ct
import 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.decode()
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.decode()
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.decode(),
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.decode(),
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
self.bin_path = location.bin_path
def __str__(self):
return "%s 0x%x" % (self.bin_path.decode(), self.address)
def get_argument(self, index):
arg = bcc_usdt_argument()
res = lib.bcc_usdt_get_argument(self.probe.context, self.probe.provider,
self.probe.name,
self.index, index, ct.byref(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 [sema 0x%x]" % \
(self.provider.decode(), self.name.decode(), self.semaphore)
def short_name(self):
return "%s:%s" % (self.provider.decode(), self.name.decode())
def get_location(self, index):
loc = bcc_usdt_location()
res = lib.bcc_usdt_get_location(self.context, self.provider, self.name,
index, ct.byref(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
if path:
self.context = lib.bcc_usdt_new_frompid(pid, path.encode('ascii'))
else:
self.context = lib.bcc_usdt_new_frompid(pid, ct.c_char_p(0))
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 __del__(self):
lib.bcc_usdt_close(self.context)
def enable_probe(self, probe, fn_name):
probe_parts = probe.split(":", 1)
if len(probe_parts) == 1:
ret = lib.bcc_usdt_enable_probe(
self.context, probe.encode('ascii'), fn_name.encode('ascii'))
else:
(provider_name, probe_name) = probe_parts
ret = lib.bcc_usdt_enable_fully_specified_probe(
self.context, provider_name.encode('ascii'), probe_name.encode('ascii'),
fn_name.encode('ascii'))
if ret != 0:
raise USDTException(
"""Failed to enable USDT probe '%s':
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.
""" % probe)
def enable_probe_or_bail(self, probe, fn_name):
try:
self.enable_probe(probe, fn_name)
except USDTException as e:
print(e, file=sys.stderr)
sys.exit(1)
def get_context(self):
return self.context
def get_text(self):
ctx_array = (ct.c_void_p * 1)()
ctx_array[0] = ct.c_void_p(self.context)
return lib.bcc_usdt_genargs(ctx_array, 1).decode()
def get_probe_arg_ctype(self, probe_name, arg_index):
probe_parts = probe_name.split(":", 1)
if len(probe_parts) == 1:
return lib.bcc_usdt_get_probe_argctype(
self.context, probe_name.encode('ascii'), arg_index).decode()
else:
(provider_name, probe) = probe_parts
return lib.bcc_usdt_get_fully_specified_probe_argctype(
self.context, provider_name.encode('ascii'), probe.encode('ascii'), arg_index).decode()
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, attach_usdt_ignore_pid):
probes = self.enumerate_active_probes()
for (binpath, fn_name, addr, pid) in probes:
if attach_usdt_ignore_pid:
pid = -1
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