stackcount.py

#!/usr/bin/env python
#
# stackcount    Count events and their stack traces.
#               For Linux, uses BCC, eBPF.
#
# USAGE: stackcount.py [-h] [-p PID] [-i INTERVAL] [-D DURATION] [-T] [-r] [-s]
#                      [-P] [-K] [-U] [-v] [-d] [-f] [--debug]
#
# The pattern is a string with optional '*' wildcards, similar to file
# globbing. If you'd prefer to use regular expressions, use the -r option.
#
# Copyright 2016 Netflix, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 12-Jan-2016	Brendan Gregg	    Created this.
# 09-Jul-2016   Sasha Goldshtein    Generalized for uprobes and tracepoints.

from __future__ import print_function
from bcc import BPF, USDT
from time import sleep, strftime
import argparse
import re
import signal
import sys
import traceback

debug = False

class Probe(object):
    def __init__(self, pattern, kernel_stack, user_stack, use_regex=False,
                 pid=None, per_pid=False):
        """Init a new probe.

        Init the probe from the pattern provided by the user. The supported
        patterns mimic the 'trace' and 'argdist' tools, but are simpler because
        we don't have to distinguish between probes and retprobes.

            func            -- probe a kernel function
            lib:func        -- probe a user-space function in the library 'lib'
            p::func         -- same thing as 'func'
            p:lib:func      -- same thing as 'lib:func'
            t:cat:event     -- probe a kernel tracepoint
            u:lib:probe     -- probe a USDT tracepoint
        """
        self.kernel_stack = kernel_stack
        self.user_stack = user_stack
        parts = pattern.split(':')
        if len(parts) == 1:
            parts = ["p", "", parts[0]]
        elif len(parts) == 2:
            parts = ["p", parts[0], parts[1]]
        elif len(parts) == 3:
            if parts[0] == "t":
                parts = ["t", "", "%s:%s" % tuple(parts[1:])]
            if parts[0] not in ["p", "t", "u"]:
                raise Exception("Type must be 'p', 't', or 'u', but got %s" %
                                parts[0])
        else:
            raise Exception("Too many ':'-separated components in pattern %s" %
                            pattern)

        (self.type, self.library, self.pattern) = parts
        if not use_regex:
            self.pattern = self.pattern.replace('*', '.*')
            self.pattern = '^' + self.pattern + '$'

        if (self.type == "p" and self.library) or self.type == "u":
            libpath = BPF.find_library(self.library)
            if libpath is None:
                # This might be an executable (e.g. 'bash')
                libpath = BPF.find_exe(self.library)
            if libpath is None or len(libpath) == 0:
                raise Exception("unable to find library %s" % self.library)
            self.library = libpath

        self.pid = pid
        self.per_pid = per_pid
        self.matched = 0

    def is_kernel_probe(self):
        return self.type == "t" or (self.type == "p" and self.library == "")

    def attach(self):
        if self.type == "p":
            if self.library:
                self.bpf.attach_uprobe(name=self.library,
                                       sym_re=self.pattern,
                                       fn_name="trace_count",
                                       pid=self.pid or -1)
                self.matched = self.bpf.num_open_uprobes()
            else:
                self.bpf.attach_kprobe(event_re=self.pattern,
                                       fn_name="trace_count")
                self.matched = self.bpf.num_open_kprobes()
        elif self.type == "t":
            self.bpf.attach_tracepoint(tp_re=self.pattern,
                                       fn_name="trace_count")
            self.matched = self.bpf.num_open_tracepoints()
        elif self.type == "u":
            pass    # Nothing to do -- attach already happened in `load`

        if self.matched == 0:
            raise Exception("No functions matched by pattern %s" %
                            self.pattern)

    def load(self):
        ctx_name = "ctx"
        stack_trace = ""
        if self.user_stack:
                stack_trace += """
                    key.user_stack_id = stack_traces.get_stackid(
                      %s, BPF_F_REUSE_STACKID | BPF_F_USER_STACK
                    );""" % (ctx_name)
        else:
                stack_trace += "key.user_stack_id = -1;"
        if self.kernel_stack:
                stack_trace += """
                    key.kernel_stack_id = stack_traces.get_stackid(
                      %s, BPF_F_REUSE_STACKID
                    );""" % (ctx_name)
        else:
                stack_trace += "key.kernel_stack_id = -1;"

        trace_count_text = """
int trace_count(void *ctx) {
    FILTER
    struct key_t key = {};
    key.tgid = GET_TGID;
    STORE_COMM
    %s
    counts.increment(key);
    return 0;
}
        """
        trace_count_text = trace_count_text % (stack_trace)

        bpf_text = """#include <uapi/linux/ptrace.h>
#include <linux/sched.h>

struct key_t {
    // no pid (thread ID) so that we do not needlessly split this key
    u32 tgid;
    int kernel_stack_id;
    int user_stack_id;
    char name[TASK_COMM_LEN];
};

BPF_HASH(counts, struct key_t);
BPF_STACK_TRACE(stack_traces, 1024);
        """

        # We really mean the tgid from the kernel's perspective, which is in
        # the top 32 bits of bpf_get_current_pid_tgid().
        if self.is_kernel_probe() and self.pid:
            trace_count_text = trace_count_text.replace('FILTER',
                ('u32 pid; pid = bpf_get_current_pid_tgid() >> 32; ' +
                'if (pid != %d) { return 0; }') % (self.pid))
        else:
            trace_count_text = trace_count_text.replace('FILTER', '')

        # We need per-pid statistics when tracing a user-space process, because
        # the meaning of the symbols depends on the pid. We also need them if
        # per-pid statistics were requested with -P, or for user stacks.
        if self.per_pid or not self.is_kernel_probe() or self.user_stack:
            trace_count_text = trace_count_text.replace('GET_TGID',
                                        'bpf_get_current_pid_tgid() >> 32')
            trace_count_text = trace_count_text.replace('STORE_COMM',
                        'bpf_get_current_comm(&key.name, sizeof(key.name));')
        else:
            # kernel stacks only. skip splitting on PID so these aggregate
            # together, and don't store the process name.
            trace_count_text = trace_count_text.replace(
                                    'GET_TGID', '0xffffffff')
            trace_count_text = trace_count_text.replace('STORE_COMM', '')

        self.usdt = None
        if self.type == "u":
            self.usdt = USDT(path=self.library, pid=self.pid)
            for probe in self.usdt.enumerate_probes():
                if not self.pid and (probe.bin_path != self.library):
                    continue
                if re.match(self.pattern, probe.name):
                    # This hack is required because the bpf_usdt_readarg
                    # functions generated need different function names for
                    # each attached probe. If we just stick to trace_count,
                    # we'd get multiple bpf_usdt_readarg helpers with the same
                    # name when enabling more than one USDT probe.
                    new_func = "trace_count_%d" % self.matched
                    bpf_text += trace_count_text.replace(
                                            "trace_count", new_func)
                    self.usdt.enable_probe(probe.name, new_func)
                    self.matched += 1
            if debug:
                print(self.usdt.get_text())
        else:
            bpf_text += trace_count_text

        if debug:
            print(bpf_text)
        self.bpf = BPF(text=bpf_text,
                       usdt_contexts=[self.usdt] if self.usdt else [])

class Tool(object):
    def __init__(self):
        examples = """examples:
    ./stackcount submit_bio         # count kernel stack traces for submit_bio
    ./stackcount -d ip_output       # include a user/kernel stack delimiter
    ./stackcount -s ip_output       # show symbol offsets
    ./stackcount -sv ip_output      # show offsets and raw addresses (verbose)
    ./stackcount 'tcp_send*'        # count stacks for funcs matching tcp_send*
    ./stackcount -r '^tcp_send.*'   # same as above, using regular expressions
    ./stackcount -Ti 5 ip_output    # output every 5 seconds, with timestamps
    ./stackcount -p 185 ip_output   # count ip_output stacks for PID 185 only
    ./stackcount -p 185 c:malloc    # count stacks for malloc in PID 185
    ./stackcount t:sched:sched_fork # count stacks for sched_fork tracepoint
    ./stackcount -p 185 u:node:*    # count stacks for all USDT probes in node
    ./stackcount -K t:sched:sched_switch   # kernel stacks only
    ./stackcount -U t:sched:sched_switch   # user stacks only
        """
        parser = argparse.ArgumentParser(
            description="Count events and their stack traces",
            formatter_class=argparse.RawDescriptionHelpFormatter,
            epilog=examples)
        parser.add_argument("-p", "--pid", type=int,
            help="trace this PID only")
        parser.add_argument("-i", "--interval",
            help="summary interval, seconds")
        parser.add_argument("-D", "--duration",
            help="total duration of trace, seconds")
        parser.add_argument("-T", "--timestamp", action="store_true",
            help="include timestamp on output")
        parser.add_argument("-r", "--regexp", action="store_true",
            help="use regular expressions. Default is \"*\" wildcards only.")
        parser.add_argument("-s", "--offset", action="store_true",
            help="show address offsets")
        parser.add_argument("-P", "--perpid", action="store_true",
            help="display stacks separately for each process")
        parser.add_argument("-K", "--kernel-stacks-only",
            action="store_true", help="kernel stack only", default=False)
        parser.add_argument("-U", "--user-stacks-only",
            action="store_true", help="user stack only", default=False)
        parser.add_argument("-v", "--verbose", action="store_true",
            help="show raw addresses")
        parser.add_argument("-d", "--delimited", action="store_true",
            help="insert delimiter between kernel/user stacks")
        parser.add_argument("-f", "--folded", action="store_true",
            help="output folded format")
        parser.add_argument("--debug", action="store_true",
            help="print BPF program before starting (for debugging purposes)")
        parser.add_argument("pattern",
            help="search expression for events")
        self.args = parser.parse_args()
        global debug
        debug = self.args.debug

        if self.args.duration and not self.args.interval:
            self.args.interval = self.args.duration
        if not self.args.interval:
            self.args.interval = 99999999

        if self.args.kernel_stacks_only and self.args.user_stacks_only:
            print("ERROR: -K and -U are mutually exclusive. If you want " +
                "both stacks, that is the default.")
            exit()
        if not self.args.kernel_stacks_only and not self.args.user_stacks_only:
            self.kernel_stack = True
            self.user_stack = True
        else:
            self.kernel_stack = self.args.kernel_stacks_only
            self.user_stack = self.args.user_stacks_only

        self.probe = Probe(self.args.pattern,
                           self.kernel_stack, self.user_stack,
                           self.args.regexp, self.args.pid, self.args.perpid)
        self.need_delimiter = self.args.delimited and not (
                    self.args.kernel_stacks_only or self.args.user_stacks_only)

    def _print_kframe(self, addr):
        print("  ", end="")
        if self.args.verbose:
            print("%-16x " % addr, end="")
        if self.args.offset:
            print("%s" % self.probe.bpf.ksym(addr, show_offset=True))
        else:
            print("%s" % self.probe.bpf.ksym(addr))

    def _print_uframe(self, addr, pid):
        print("  ", end="")
        if self.args.verbose:
            print("%-16x " % addr, end="")
        if self.args.offset:
            print("%s" % self.probe.bpf.sym(addr, pid, show_offset=True))
        else:
            print("%s" % self.probe.bpf.sym(addr, pid))

    @staticmethod
    def _signal_ignore(signal, frame):
        print()

    def _print_comm(self, comm, pid):
        print("    %s [%d]" % (comm, pid))

    def run(self):
        self.probe.load()
        self.probe.attach()
        if not self.args.folded:
            print("Tracing %d functions for \"%s\"... Hit Ctrl-C to end." %
                  (self.probe.matched, self.args.pattern))
        b = self.probe.bpf
        exiting = 0 if self.args.interval else 1
        seconds = 0
        while True:
            try:
                sleep(int(self.args.interval))
                seconds += int(self.args.interval)
            except KeyboardInterrupt:
                exiting = 1
                # as cleanup can take many seconds, trap Ctrl-C:
                signal.signal(signal.SIGINT, Tool._signal_ignore)
            if self.args.duration and seconds >= int(self.args.duration):
                exiting = 1

            if not self.args.folded:
                print()
            if self.args.timestamp:
                print("%-8s\n" % strftime("%H:%M:%S"), end="")

            counts = self.probe.bpf["counts"]
            stack_traces = self.probe.bpf["stack_traces"]
            self.comm_cache = {}
            for k, v in sorted(counts.items(),
                               key=lambda counts: counts[1].value):
                user_stack = [] if k.user_stack_id < 0 else \
                    stack_traces.walk(k.user_stack_id)
                kernel_stack = [] if k.kernel_stack_id < 0 else \
                    stack_traces.walk(k.kernel_stack_id)

                if self.args.folded:
                    # print folded stack output
                    user_stack = list(user_stack)
                    kernel_stack = list(kernel_stack)
                    line = [k.name.decode()] + \
                        [b.sym(addr, k.tgid) for addr in
                        reversed(user_stack)] + \
                        (self.need_delimiter and ["-"] or []) + \
                        [b.ksym(addr) for addr in reversed(kernel_stack)]
                    print("%s %d" % (";".join(line), v.value))
                else:
                    # print multi-line stack output
                    for addr in kernel_stack:
                        self._print_kframe(addr)
                    if self.need_delimiter:
                        print("    --")
                    for addr in user_stack:
                        self._print_uframe(addr, k.tgid)
                    if not self.args.pid and k.tgid != 0xffffffff:
                        self._print_comm(k.name, k.tgid)
                    print("    %d\n" % v.value)
            counts.clear()

            if exiting:
                if not self.args.folded:
                    print("Detaching...")
                exit()

if __name__ == "__main__":
    try:
        Tool().run()
    except Exception:
        if debug:
            traceback.print_exc()
        elif sys.exc_info()[0] is not SystemExit:
            print(sys.exc_info()[1])