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# argdist Trace a function and display a distribution of its
# parameter values as a histogram or frequency count.
# USAGE: argdist [-h] [-p PID] [-z STRING_SIZE] [-i INTERVAL] [-n COUNT] [-v]
# [-c] [-T TOP] [-C specifier] [-H specifier] [-I header]
# [-t TID]
# Licensed under the Apache License, Version 2.0 (the "License")
# Copyright (C) 2016 Sasha Goldshtein.
from bcc import BPF, USDT, StrcmpRewrite
from time import sleep, strftime
import argparse
import re
import traceback
import os
import sys
class Probe(object):
next_probe_index = 0
streq_index = 0
aliases = {"$PID": "(bpf_get_current_pid_tgid() >> 32)"}
def _substitute_aliases(self, expr):
if expr is None:
return expr
for alias, subst in Probe.aliases.items():
expr = expr.replace(alias, subst)
return expr
def _parse_signature(self):
params = map(str.strip, self.signature.split(','))
self.param_types = {}
for param in params:
# If the type is a pointer, the * can be next to the
# param name. Other complex types like arrays are not
# supported right now.
index = param.rfind('*')
index = index if index != -1 else param.rfind(' ')
param_type = param[0:index + 1].strip()
param_name = param[index + 1:].strip()
self.param_types[param_name] = param_type
# Maintain list of user params. Then later decide to
# switch to bpf_probe_read_kernel or bpf_probe_read_user.
if "__user" in param_type.split():
def _generate_entry(self):
self.entry_probe_func = self.probe_func_name + "_entry"
text = """
int PROBENAME(struct pt_regs *ctx SIGNATURE)
u64 __pid_tgid = bpf_get_current_pid_tgid();
u32 __pid = __pid_tgid; // lower 32 bits
u32 __tgid = __pid_tgid >> 32; // upper 32 bits
return 0;
text = text.replace("PROBENAME", self.entry_probe_func)
text = text.replace("SIGNATURE",
"" if len(self.signature) == 0 else ", " + self.signature)
text = text.replace("PID_FILTER", self._generate_pid_filter())
text = text.replace("TID_FILTER", self._generate_tid_filter())
collect = ""
for pname in self.args_to_probe:
param_hash = self.hashname_prefix + pname
if pname == "__latency":
collect += """
u64 __time = bpf_ktime_get_ns();
%s.update(&__pid, &__time);
""" % param_hash
collect += "%s.update(&__pid, &%s);\n" % \
(param_hash, pname)
text = text.replace("COLLECT", collect)
return text
def _generate_entry_probe(self):
# Any $entry(name) expressions result in saving that argument
# when entering the function.
self.args_to_probe = set()
regex = r"\$entry\((\w+)\)"
for expr in self.exprs:
for arg in re.finditer(regex, expr):
for arg in re.finditer(regex, self.filter):
if any(map(lambda expr: "$latency" in expr, self.exprs)) or \
"$latency" in self.filter:
self.param_types["__latency"] = "u64" # nanoseconds
for pname in self.args_to_probe:
if pname not in self.param_types:
raise ValueError("$entry(%s): no such param" %
self.hashname_prefix = "%s_param_" % self.probe_hash_name
text = ""
for pname in self.args_to_probe:
# Each argument is stored in a separate hash that is
# keyed by pid.
text += "BPF_HASH(%s, u32, %s);\n" % \
(self.hashname_prefix + pname,
text += self._generate_entry()
return text
def _generate_retprobe_prefix(self):
# After we're done here, there are __%s_val variables for each
# argument we needed to probe using $entry(name), and they all
# have values (which isn't necessarily the case if we missed
# the method entry probe).
text = ""
self.param_val_names = {}
for pname in self.args_to_probe:
val_name = "__%s_val" % pname
text += "%s *%s = %s.lookup(&__pid);\n" % \
(self.param_types[pname], val_name,
self.hashname_prefix + pname)
text += "if (%s == 0) { return 0 ; }\n" % val_name
self.param_val_names[pname] = val_name
return text
def _replace_entry_exprs(self):
for pname, vname in self.param_val_names.items():
if pname == "__latency":
entry_expr = "$latency"
val_expr = "(bpf_ktime_get_ns() - *%s)" % vname
entry_expr = "$entry(%s)" % pname
val_expr = "(*%s)" % vname
for i in range(0, len(self.exprs)):
self.exprs[i] = self.exprs[i].replace(
entry_expr, val_expr)
self.filter = self.filter.replace(entry_expr,
def _attach_entry_probe(self):
if self.is_user:
fn_name=self.entry_probe_func, or -1)
def _bail(self, error):
raise ValueError("error parsing probe '%s': %s" %
(self.raw_spec, error))
def _validate_specifier(self):
# Everything after '#' is the probe label, ignore it
spec = self.raw_spec.split('#')[0]
parts = spec.strip().split(':')
if len(parts) < 3:
self._bail("at least the probe type, library, and " +
"function signature must be specified")
if len(parts) > 6:
self._bail("extraneous ':'-separated parts detected")
if parts[0] not in ["r", "p", "t", "u"]:
self._bail("probe type must be 'p', 'r', 't', or 'u'" +
" but got '%s'" % parts[0])
if re.match(r"\S+\(.*\)", parts[2]) is None:
self._bail(("function signature '%s' has an invalid " +
"format") % parts[2])
def _parse_expr_types(self, expr_types):
if len(expr_types) == 0:
self._bail("no expr types specified")
self.expr_types = expr_types.split(',')
def _parse_exprs(self, exprs):
if len(exprs) == 0:
self._bail("no exprs specified")
self.exprs = exprs.split(',')
def _make_valid_identifier(self, ident):
return re.sub(r'[^A-Za-z0-9_]', '_', ident)
def __init__(self, tool, type, specifier):
self.usdt_ctx = None
self.streq_functions = "" =
self.tid = tool.args.tid
self.cumulative = tool.args.cumulative or False
self.raw_spec = specifier
self.probe_user_list = set()
self.bin_cmp = False
spec_and_label = specifier.split('#')
self.label = spec_and_label[1] \
if len(spec_and_label) == 2 else None
parts = spec_and_label[0].strip().split(':')
self.type = type # hist or freq
self.probe_type = parts[0]
fparts = parts[2].split('(')
self.function = fparts[0].strip()
if self.probe_type == "t":
self.library = "" # kernel
self.tp_category = parts[1]
self.tp_event = self.function
elif self.probe_type == "u":
self.library = parts[1]
self.probe_func_name = self._make_valid_identifier(
"%s_probe%d" %
(self.function, Probe.next_probe_index))
self.library = parts[1]
self.is_user = len(self.library) > 0
self.signature = fparts[1].strip()[:-1]
# If the user didn't specify an expression to probe, we probe
# the retval in a ret probe, or simply the value "1" otherwise.
self.is_default_expr = len(parts) < 5
if not self.is_default_expr:
if len(self.exprs) != len(self.expr_types):
self._bail("mismatched # of exprs and types")
if self.type == "hist" and len(self.expr_types) > 1:
self._bail("histograms can only have 1 expr")
if not self.probe_type == "r" and self.type == "hist":
self._bail("histograms must have expr")
self.expr_types = \
["u64" if not self.probe_type == "r" else "int"]
self.exprs = \
["1" if not self.probe_type == "r" else "$retval"]
self.filter = "" if len(parts) != 6 else parts[5]
# Do we need to attach an entry probe so that we can collect an
# argument that is required for an exit (return) probe?
def check(expr):
keywords = ["$entry", "$latency"]
return any(map(lambda kw: kw in expr, keywords))
self.entry_probe_required = self.probe_type == "r" and \
(any(map(check, self.exprs)) or check(self.filter))
self.probe_func_name = self._make_valid_identifier(
"%s_probe%d" %
(self.function, Probe.next_probe_index))
self.probe_hash_name = self._make_valid_identifier(
"%s_hash%d" %
(self.function, Probe.next_probe_index))
Probe.next_probe_index += 1
def _enable_usdt_probe(self):
self.usdt_ctx = USDT(path=self.library,
self.function, self.probe_func_name)
def _substitute_exprs(self):
def repl(expr):
expr = self._substitute_aliases(expr)
rdict = StrcmpRewrite.rewrite_expr(expr,
self.bin_cmp, self.library,
self.probe_user_list, self.streq_functions,
expr = rdict["expr"]
self.streq_functions = rdict["streq_functions"]
Probe.streq_index = rdict["probeid"]
return expr.replace("$retval", "PT_REGS_RC(ctx)")
for i in range(0, len(self.exprs)):
self.exprs[i] = repl(self.exprs[i])
self.filter = repl(self.filter)
def _is_string(self, expr_type):
return expr_type == "char*" or expr_type == "char *"
def _generate_hash_field(self, i):
if self._is_string(self.expr_types[i]):
return "struct __string_t v%d;\n" % i
return "%s v%d;\n" % (self.expr_types[i], i)
def _generate_usdt_arg_assignment(self, i):
expr = self.exprs[i]
if self.probe_type == "u" and expr[0:3] == "arg":
arg_index = int(expr[3])
arg_ctype = self.usdt_ctx.get_probe_arg_ctype(
self.function, arg_index - 1)
return (" %s %s = 0;\n" +
" bpf_usdt_readarg(%s, ctx, &%s);\n") \
% (arg_ctype, expr, expr[3], expr)
return ""
def _generate_field_assignment(self, i):
text = self._generate_usdt_arg_assignment(i)
if self._is_string(self.expr_types[i]):
if self.is_user or \
self.exprs[i] in self.probe_user_list:
probe_readfunc = "bpf_probe_read_user"
probe_readfunc = "bpf_probe_read_kernel"
return (text + " %s(&__key.v%d.s," +
" sizeof(__key.v%d.s), (void *)%s);\n") % \
(probe_readfunc, i, i, self.exprs[i])
return text + " __key.v%d = %s;\n" % \
(i, self.exprs[i])
def _generate_hash_decl(self):
if self.type == "hist":
return "BPF_HISTOGRAM(%s, %s);" % \
(self.probe_hash_name, self.expr_types[0])
text = "struct %s_key_t {\n" % self.probe_hash_name
for i in range(0, len(self.expr_types)):
text += self._generate_hash_field(i)
text += "};\n"
text += "BPF_HASH(%s, struct %s_key_t, u64);\n" % \
(self.probe_hash_name, self.probe_hash_name)
return text
def _generate_key_assignment(self):
if self.type == "hist":
return self._generate_usdt_arg_assignment(0) + \
("%s __key = %s;\n" %
(self.expr_types[0], self.exprs[0]))
text = "struct %s_key_t __key = {};\n" % \
for i in range(0, len(self.exprs)):
text += self._generate_field_assignment(i)
return text
def _generate_hash_update(self):
if self.type == "hist":
return "%s.atomic_increment(bpf_log2l(__key));" % \
return "%s.atomic_increment(__key);" % \
def _generate_pid_filter(self):
# Kernel probes need to explicitly filter pid, because the
# attach interface doesn't support pid filtering
if is not None and not self.is_user:
return "if (__tgid != %d) { return 0; }" %
return ""
def _generate_tid_filter(self):
if self.tid is not None and not self.is_user:
return "if (__pid != %d) { return 0; }" % self.tid
return ""
def generate_text(self):
program = ""
probe_text = """
""" + (
(self.tp_category, self.tp_event)
if self.probe_type == "t"
else "int PROBENAME(struct pt_regs *ctx SIGNATURE)") + """
u64 __pid_tgid = bpf_get_current_pid_tgid();
u32 __pid = __pid_tgid; // lower 32 bits
u32 __tgid = __pid_tgid >> 32; // upper 32 bits
if (!(FILTER)) return 0;
return 0;
prefix = ""
signature = ""
# If any entry arguments are probed in a ret probe, we need
# to generate an entry probe to collect them
if self.entry_probe_required:
program += self._generate_entry_probe()
prefix += self._generate_retprobe_prefix()
# Replace $entry(paramname) with a reference to the
# value we collected when entering the function:
if self.probe_type == "p" and len(self.signature) > 0:
# Only entry uprobes/kprobes can have user-specified
# signatures. Other probes force it to ().
signature = ", " + self.signature
program += probe_text.replace("PROBENAME",
program = program.replace("SIGNATURE", signature)
program = program.replace("PID_FILTER",
program = program.replace("TID_FILTER",
decl = self._generate_hash_decl()
key_expr = self._generate_key_assignment()
collect = self._generate_hash_update()
program = program.replace("DATA_DECL", decl)
program = program.replace("KEY_EXPR", key_expr)
program = program.replace("FILTER",
"1" if len(self.filter) == 0 else self.filter)
program = program.replace("COLLECT", collect)
program = program.replace("PREFIX", prefix)
return self.streq_functions + program
def _attach_u(self):
libpath = BPF.find_library(self.library)
if libpath is None:
libpath = BPF.find_exe(self.library)
if libpath is None or len(libpath) == 0:
self._bail("unable to find library %s" % self.library)
if self.probe_type == "r":
fn_name=self.probe_func_name, or -1)
fn_name=self.probe_func_name, or -1)
def _attach_k(self):
if self.probe_type == "t":
pass # Nothing to do for tracepoints
elif self.probe_type == "r":
def attach(self, bpf):
self.bpf = bpf
if self.probe_type == "u":
if self.is_user:
if self.entry_probe_required:
def _v2s(self, v):
# Most fields can be converted with plain str(), but strings
# are wrapped in a __string_t which has an .s field
if "__string_t" in type(v).__name__:
return str(v.s)
return str(v)
def _display_expr(self, i):
# Replace ugly latency calculation with $latency
expr = self.exprs[i].replace(
"(bpf_ktime_get_ns() - *____latency_val)", "$latency")
# Replace alias values back with the alias name
for alias, subst in Probe.aliases.items():
expr = expr.replace(subst, alias)
# Replace retval expression with $retval
expr = expr.replace("PT_REGS_RC(ctx)", "$retval")
# Replace ugly (*__param_val) expressions with param name
return re.sub(r"\(\*__(\w+)_val\)", r"\1", expr)
def _display_key(self, key):
if self.is_default_expr:
if not self.probe_type == "r":
return "total calls"
return "retval = %s" % str(key.v0)
# The key object has v0, ..., vk fields containing
# the values of the expressions from self.exprs
def str_i(i):
key_i = self._v2s(getattr(key, "v%d" % i))
return "%s = %s" % \
(self._display_expr(i), key_i)
return ", ".join(map(str_i, range(0, len(self.exprs))))
def display(self, top):
data = self.bpf.get_table(self.probe_hash_name)
if self.type == "freq":
print(self.label or self.raw_spec)
print("\t%-10s %s" % ("COUNT", "EVENT"))
sdata = sorted(data.items(), key=lambda p: p[1].value)
if top is not None:
sdata = sdata[-top:]
for key, value in sdata:
# Print some nice values if the user didn't
# specify an expression to probe
if self.is_default_expr:
if not self.probe_type == "r":
key_str = "total calls"
key_str = "retval = %s" % \
key_str = self._display_key(key)
print("\t%-10s %s" %
(str(value.value), key_str))
elif self.type == "hist":
label = self.label or (self._display_expr(0)
if not self.is_default_expr else "retval")
if not self.cumulative:
def __str__(self):
return self.label or self.raw_spec
class Tool(object):
examples = """
Probe specifier syntax:
p,r,t,u -- probe at function entry, function exit, kernel
tracepoint, or USDT probe
in exit probes: can use $retval, $entry(param), $latency
library -- the library that contains the function
(leave empty for kernel functions)
category -- the category of the kernel tracepoint (e.g. net, sched)
function -- the function name to trace (or tracepoint name)
signature -- the function's parameters, as in the C header
type -- the type of the expression to collect (supports multiple)
expr -- the expression to collect (supports multiple)
filter -- the filter that is applied to collected values
label -- the label for this probe in the resulting output
argdist -H 'p::__kmalloc(u64 size):u64:size'
Print a histogram of allocation sizes passed to kmalloc
argdist -p 1005 -C 'p:c:malloc(size_t size):size_t:size:size==16'
Print a frequency count of how many times process 1005 called malloc
with an allocation size of 16 bytes
argdist -C 'r:c:gets():char*:(char*)$retval#snooped strings'
Snoop on all strings returned by gets()
argdist -H 'r::__kmalloc(size_t size):u64:$latency/$entry(size)#ns per byte'
Print a histogram of nanoseconds per byte from kmalloc allocations
argdist -C 'p::__kmalloc(size_t sz, gfp_t flags):size_t:sz:flags&GFP_ATOMIC'
Print frequency count of kmalloc allocation sizes that have GFP_ATOMIC
argdist -p 1005 -C 'p:c:write(int fd):int:fd' -T 5
Print frequency counts of how many times writes were issued to a
particular file descriptor number, in process 1005, but only show
the top 5 busiest fds
argdist -p 1005 -H 'r:c:read()'
Print a histogram of results (sizes) returned by read() in process 1005
argdist -C 'r::__vfs_read():u32:$PID:$latency > 100000'
Print frequency of reads by process where the latency was >0.1ms
argdist -H 'r::__vfs_read(void *file, void *buf, size_t count):size_t:
$entry(count):$latency > 1000000'
Print a histogram of read sizes that were longer than 1ms
argdist -H \\
'p:c:write(int fd, const void *buf, size_t count):size_t:count:fd==1'
Print a histogram of buffer sizes passed to write() across all
processes, where the file descriptor was 1 (STDOUT)
argdist -C 'p:c:fork()#fork calls'
Count fork() calls in libc across all processes
Can also use, which is easier and more flexible
argdist -H 't:block:block_rq_complete():u32:args->nr_sector'
Print histogram of number of sectors in completing block I/O requests
argdist -C 't:irq:irq_handler_entry():int:args->irq'
Aggregate interrupts by interrupt request (IRQ)
argdist -C 'u:pthread:pthread_start():u64:arg2' -p 1337
Print frequency of function addresses used as a pthread start function,
relying on the USDT pthread_start probe in process 1337
argdist -H 'p:c:sleep(u32 seconds):u32:seconds' \\
-H 'p:c:nanosleep(struct timespec *req):long:req->tv_nsec'
Print histograms of sleep() and nanosleep() parameter values
argdist -p 2780 -z 120 \\
-C 'p:c:write(int fd, char* buf, size_t len):char*:buf:fd==1'
Spy on writes to STDOUT performed by process 2780, up to a string size
of 120 characters
argdist -I 'kernel/sched/sched.h' \\
-C 'p::__account_cfs_rq_runtime(struct cfs_rq *cfs_rq):s64:cfs_rq->runtime_remaining'
Trace on the cfs scheduling runqueue remaining runtime. The struct cfs_rq is defined
in kernel/sched/sched.h which is in kernel source tree and not in kernel-devel
package. So this command needs to run at the kernel source tree root directory
so that the added header file can be found by the compiler.
def __init__(self):
parser = argparse.ArgumentParser(description="Trace a " +
"function and display a summary of its parameter values.",
parser.add_argument("-p", "--pid", type=int,
help="id of the process to trace (optional)")
parser.add_argument("-t", "--tid", type=int,
help="id of the thread to trace (optional)")
parser.add_argument("-z", "--string-size", default=80,
help="maximum string size to read from char* arguments")
parser.add_argument("-i", "--interval", default=1, type=int,
help="output interval, in seconds (default 1 second)")
parser.add_argument("-d", "--duration", type=int,
help="total duration of trace, in seconds")
parser.add_argument("-n", "--number", type=int, dest="count",
help="number of outputs")
parser.add_argument("-v", "--verbose", action="store_true",
help="print resulting BPF program code before executing")
parser.add_argument("-c", "--cumulative", action="store_true",
help="do not clear histograms and freq counts at " +
"each interval")
parser.add_argument("-T", "--top", type=int,
help="number of top results to show (not applicable to " +
parser.add_argument("-H", "--histogram", action="append",
dest="histspecifier", metavar="specifier",
help="probe specifier to capture histogram of " +
"(see examples below)")
parser.add_argument("-C", "--count", action="append",
dest="countspecifier", metavar="specifier",
help="probe specifier to capture count of " +
"(see examples below)")
parser.add_argument("-I", "--include", action="append",
help="additional header files to include in the BPF program "
"as either full path, "
"or relative to relative to current working directory, "
"or relative to default kernel header search path")
self.args = parser.parse_args()
self.usdt_ctx = None
def _create_probes(self):
self.probes = []
for specifier in (self.args.countspecifier or []):
self.probes.append(Probe(self, "freq", specifier))
for histspecifier in (self.args.histspecifier or []):
self.probes.append(Probe(self, "hist", histspecifier))
if len(self.probes) == 0:
print("at least one specifier is required")
def _generate_program(self):
bpf_source = """
struct __string_t { char s[%d]; };
#include <uapi/linux/ptrace.h>
""" % self.args.string_size
for include in (self.args.include or []):
if include.startswith((".", "/")):
include = os.path.abspath(include)
bpf_source += "#include \"%s\"\n" % include
bpf_source += "#include <%s>\n" % include
bpf_source += BPF.generate_auto_includes(
map(lambda p: p.raw_spec, self.probes))
for probe in self.probes:
bpf_source += probe.generate_text()
if self.args.verbose:
for text in [probe.usdt_ctx.get_text()
for probe in self.probes
if probe.usdt_ctx]:
usdt_contexts = [probe.usdt_ctx
for probe in self.probes if probe.usdt_ctx]
self.bpf = BPF(text=bpf_source, usdt_contexts=usdt_contexts)
def _attach(self):
for probe in self.probes:
if self.args.verbose:
print("open uprobes: %s" % list(self.bpf.uprobe_fds.keys()))
print("open kprobes: %s" % list(self.bpf.kprobe_fds.keys()))
def _main_loop(self):
count_so_far = 0
seconds = 0
while True:
seconds += self.args.interval
except KeyboardInterrupt:
print("[%s]" % strftime("%H:%M:%S"))
for probe in self.probes:
count_so_far += 1
if self.args.count is not None and \
count_so_far >= self.args.count:
if self.args.duration and \
seconds >= self.args.duration:
def run(self):
exc_info = sys.exc_info()
sys_exit = exc_info[0] is SystemExit
if self.args.verbose:
elif not sys_exit:
exit(0 if sys_exit else 1)
if __name__ == "__main__":