bcc/tools/execsnoop.py at v0.3.0 · dqminh/bcc

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#!/usr/bin/python

# @lint-avoid-python-3-compatibility-imports

# execsnoop Trace new processes via exec() syscalls.

# For Linux, uses BCC, eBPF. Embedded C.

# USAGE: execsnoop [-h] [-t] [-x] [-n NAME]

# This currently will print up to a maximum of 19 arguments, plus the process

# name, so 20 fields in total (MAXARG).

# This won't catch all new processes: an application may fork() but not exec().

# Licensed under the Apache License, Version 2.0 (the "License")

# 07-Feb-2016 Brendan Gregg Created this.

from __future__ import print_function

from bcc import BPF

import argparse

import ctypes as ct

import re

import time

from collections import defaultdict

# arguments

examples = """examples:

./execsnoop # trace all exec() syscalls

./execsnoop -x # include failed exec()s

./execsnoop -t # include timestamps

./execsnoop -n main # only print command lines containing "main"

"""

parser = argparse.ArgumentParser(

description="Trace exec() syscalls",

formatter_class=argparse.RawDescriptionHelpFormatter,

epilog=examples)

parser.add_argument("-t", "--timestamp", action="store_true",

help="include timestamp on output")

parser.add_argument("-x", "--fails", action="store_true",

help="include failed exec()s")

parser.add_argument("-n", "--name",

help="only print commands matching this name (regex), any arg")

args = parser.parse_args()

# define BPF program

bpf_text = """

#include <uapi/linux/ptrace.h>

#include <linux/sched.h>

#include <linux/fs.h>

#define MAXARG 20

#define ARGSIZE 128

enum event_type {

EVENT_ARG,

EVENT_RET,

};

struct data_t {

u32 pid; // PID as in the userspace term (i.e. task->tgid in kernel)

char comm[TASK_COMM_LEN];

enum event_type type;

char argv[ARGSIZE];

int retval;

};

BPF_PERF_OUTPUT(events);

static int __submit_arg(struct pt_regs *ctx, void *ptr, struct data_t *data)

{

bpf_probe_read(data->argv, sizeof(data->argv), ptr);

events.perf_submit(ctx, data, sizeof(struct data_t));

return 1;

}

static int submit_arg(struct pt_regs *ctx, void *ptr, struct data_t *data)

{

const char *argp = NULL;

bpf_probe_read(&argp, sizeof(argp), ptr);

if (argp) {

return __submit_arg(ctx, (void *)(argp), data);

}

return 0;

}

int kprobe__sys_execve(struct pt_regs *ctx, struct filename *filename,

const char __user *const __user *__argv,

const char __user *const __user *__envp)

{

// create data here and pass to submit_arg to save stack space (#555)

struct data_t data = {};

data.pid = bpf_get_current_pid_tgid() >> 32;

bpf_get_current_comm(&data.comm, sizeof(data.comm));

data.type = EVENT_ARG;

__submit_arg(ctx, (void *)filename, &data);

int i = 1; // skip first arg, as we submitted filename

// unrolled loop to walk argv[] (MAXARG)

if (submit_arg(ctx, (void *)&__argv[i], &data) == 0) goto out; i++;

if (submit_arg(ctx, (void *)&__argv[i], &data) == 0) goto out; i++; // X

if (submit_arg(ctx, (void *)&__argv[i], &data) == 0) goto out; i++;

if (submit_arg(ctx, (void *)&__argv[i], &data) == 0) goto out; i++; // XX

// handle truncated argument list

char ellipsis[] = "...";

__submit_arg(ctx, (void *)ellipsis, &data);

out:

return 0;

}

int kretprobe__sys_execve(struct pt_regs *ctx)

{

struct data_t data = {};

data.pid = bpf_get_current_pid_tgid() >> 32;

bpf_get_current_comm(&data.comm, sizeof(data.comm));

data.type = EVENT_RET;

data.retval = PT_REGS_RC(ctx);

events.perf_submit(ctx, &data, sizeof(data));

return 0;

}

"""

# initialize BPF

b = BPF(text=bpf_text)

# header

if args.timestamp:

print("%-8s" % ("TIME(s)"), end="")

print("%-16s %-6s %-6s %3s %s" % ("PCOMM", "PID", "PPID", "RET", "ARGS"))

TASK_COMM_LEN = 16 # linux/sched.h

ARGSIZE = 128 # should match #define in C above

class Data(ct.Structure):

_fields_ = [

("pid", ct.c_uint),

("comm", ct.c_char * TASK_COMM_LEN),

("type", ct.c_int),

("argv", ct.c_char * ARGSIZE),

("retval", ct.c_int),

]

class EventType(object):

EVENT_ARG = 0

EVENT_RET = 1

start_ts = time.time()

argv = defaultdict(list)

# TODO: This is best-effort PPID matching. Short-lived processes may exit

# before we get a chance to read the PPID. This should be replaced with

# fetching PPID via C when available (#364).

def get_ppid(pid):

try:

with open("/proc/%d/status" % pid) as status:

for line in status:

if line.startswith("PPid:"):

return int(line.split()[1])

except IOError:

pass

return 0

# process event

def print_event(cpu, data, size):

event = ct.cast(data, ct.POINTER(Data)).contents

skip = False

if event.type == EventType.EVENT_ARG:

argv[event.pid].append(event.argv)

elif event.type == EventType.EVENT_RET:

if args.fails and event.retval == 0:

skip = True

if args.name and not re.search(args.name, event.comm):

skip = True

if not skip:

if args.timestamp:

print("%-8.3f" % (time.time() - start_ts), end="")

ppid = get_ppid(event.pid)

print("%-16s %-6s %-6s %3s %s" % (event.comm.decode(), event.pid,

ppid if ppid > 0 else "?", event.retval,

b' '.join(argv[event.pid]).decode()))

del(argv[event.pid])

# loop with callback to print_event

b["events"].open_perf_buffer(print_event)

while 1:

b.kprobe_poll()

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