Commit 9e23ef26 authored by Brenden Blanco's avatar Brenden Blanco

Merge pull request #229 from brendangregg/master

opensnoop
parents 2e081aa6 bedd1503
...@@ -66,6 +66,7 @@ Tools: ...@@ -66,6 +66,7 @@ Tools:
- tools/[biosnoop](tools/biosnoop): Trace block device I/O with PID and latency. [Examples](tools/biosnoop_example.txt). - tools/[biosnoop](tools/biosnoop): Trace block device I/O with PID and latency. [Examples](tools/biosnoop_example.txt).
- tools/[funccount](tools/funccount): Count kernel function calls. [Examples](tools/funccount_example.txt). - tools/[funccount](tools/funccount): Count kernel function calls. [Examples](tools/funccount_example.txt).
- tools/[opensnoop](tools/opensnoop): Trace open() syscalls. [Examples](tools/opensnoop_example.txt).
- tools/[pidpersec](tools/pidpersec): Count new processes (via fork). [Examples](tools/pidpersec_example.txt). - tools/[pidpersec](tools/pidpersec): Count new processes (via fork). [Examples](tools/pidpersec_example.txt).
- tools/[syncsnoop](tools/syncsnoop): Trace sync() syscall. [Examples](tools/syncsnoop_example.txt). - tools/[syncsnoop](tools/syncsnoop): Trace sync() syscall. [Examples](tools/syncsnoop_example.txt).
- tools/[vfscount](tools/vfscount) tools/[vfscount.c](tools/vfscount.c): Count VFS calls. [Examples](tools/vfscount_example.txt). - tools/[vfscount](tools/vfscount) tools/[vfscount.c](tools/vfscount.c): Count VFS calls. [Examples](tools/vfscount_example.txt).
......
.TH opensnoop 8 "2015-08-18" "USER COMMANDS"
.SH NAME
opensnoop \- Trace open() syscalls. Uses Linux eBPF/bcc.
.SH SYNOPSIS
.B opensnoop [\-h] [\-t] [\-x] [\-p PID]
.SH DESCRIPTION
opensnoop traces the open() syscall, showing which processes are attempting
to open which files. This can be useful for determining the location of config
and log files, or for troubleshooting applications that are failing, especially
on startup.
This works by tracing the kernel sys_open() function using dynamic tracing, and
will need updating to match any changes to this function.
Since this uses BPF, only the root user can use this tool.
.SH REQUIREMENTS
CONFIG_BPF and bcc.
.SH OPTIONS
.TP
\-h
Print usage message.
.TP
\-t
Include a timestamp column.
.TP
\-x
Only print failed opens.
.TP
\-p PID
Trace this process ID only (filtered in-kernel).
.SH EXAMPLES
.TP
Trace all open() syscalls:
#
.B opensnoop
.TP
Trace all open() syscalls, and include timestamps:
#
.B opensnoop \-t
.TP
Trace only open() syscalls that failed:
#
.B opensnoop \-x
.TP
Trace PID 181 only:
#
.B opensnoop \-p 181
.SH FIELDS
.TP
TIME(s)
Time of the call, in seconds.
.TP
PID
Process ID
.TP
COMM
Process name
.TP
FD
File descriptor (if success), or -1 (if failed)
.TP
ERR
Error number (see the system's errno.h)
.TP
PATH
Open path
.SH OVERHEAD
This traces the kernel open function and prints output for each event. As the
rate of this is generally expected to be low (< 1000/s), the overhead is also
expected to be negligible. If you have an application that is calling a high
rate of open()s, then test and understand overhead before use.
.SH SOURCE
This is from bcc.
.IP
https://github.com/iovisor/bcc
.PP
Also look in the bcc distribution for a companion _examples.txt file containing
example usage, output, and commentary for this tool.
.SH OS
Linux
.SH STABILITY
Unstable - in development.
.SH AUTHOR
Brendan Gregg
.SH SEE ALSO
funccount(1)
#!/usr/bin/python
#
# opensnoop Trace open() syscalls.
# For Linux, uses BCC, eBPF. Embedded C.
#
# USAGE: opensnoop [-h] [-t] [-x] [-p PID]
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 17-Sep-2015 Brendan Gregg Created this.
from __future__ import print_function
from bcc import BPF
import argparse
# arguments
examples = """examples:
./opensnoop # trace all open() syscalls
./opensnoop -t # include timestamps
./opensnoop -x # only show failed opens
./opensnoop -p 181 # only trace PID 181
"""
parser = argparse.ArgumentParser(
description="Trace open() syscalls",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-t", "--timestamp", action="store_true",
help="include timestamp on output")
parser.add_argument("-x", "--failed", action="store_true",
help="only show failed opens")
parser.add_argument("-p", "--pid",
help="trace this PID only")
args = parser.parse_args()
debug = 0
# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
BPF_HASH(args_filename, u32, const char *);
int kprobe__sys_open(struct pt_regs *ctx, const char __user *filename)
{
u32 pid = bpf_get_current_pid_tgid();
FILTER
args_filename.update(&pid, &filename);
return 0;
};
int kretprobe__sys_open(struct pt_regs *ctx)
{
const char **filenamep;
int ret = ctx->ax;
u32 pid = bpf_get_current_pid_tgid();
filenamep = args_filename.lookup(&pid);
if (filenamep == 0) {
// missed entry
return 0;
}
bpf_trace_printk("%s %d\\n", *filenamep, ret);
args_filename.delete(&pid);
return 0;
}
"""
if args.pid:
bpf_text = bpf_text.replace('FILTER',
'if (pid != %s) { return 0; }' % args.pid)
else:
bpf_text = bpf_text.replace('FILTER', '')
if debug:
print(bpf_text)
# initialize BPF
b = BPF(text=bpf_text)
# header
if args.timestamp:
print("%-14s" % ("TIME(s)"), end="")
print("%-6s %-16s %4s %3s %s" % ("PID", "COMM", "FD", "ERR", "PATH"))
start_ts = 0
# format output
while 1:
(task, pid, cpu, flags, ts, msg) = b.trace_fields()
(filenamp, ret_s) = msg.split(" ")
ret = int(ret_s)
if (args.failed and (ret >= 0)):
continue
# split return value into FD and errno columns
if ret >= 0:
fd_s = ret; err = 0
else:
fd_s = "-1"; err = - ret
# print columns
if args.timestamp:
if start_ts == 0:
start_ts = ts
print("%-14.9f" % (ts - start_ts), end="")
print("%-6d %-16s %4s %3s %s" % (pid, task, fd_s, err, filenamp))
Demonstrations of opensnoop, the Linux eBPF/bcc version.
opensnoop traces the open() syscall system-wide, and prints various details.
Example output:
# ./opensnoop
PID COMM FD ERR PATH
17326 <...> 7 0 /sys/kernel/debug/tracing/trace_pipe
1576 snmpd 9 0 /proc/net/dev
1576 snmpd 11 0 /proc/net/if_inet6
1576 snmpd 11 0 /proc/sys/net/ipv4/neigh/eth0/retrans_time_ms
1576 snmpd 11 0 /proc/sys/net/ipv6/neigh/eth0/retrans_time_ms
1576 snmpd 11 0 /proc/sys/net/ipv6/conf/eth0/forwarding
1576 snmpd 11 0 /proc/sys/net/ipv6/neigh/eth0/base_reachable_time_ms
1576 snmpd 11 0 /proc/sys/net/ipv4/neigh/lo/retrans_time_ms
1576 snmpd 11 0 /proc/sys/net/ipv6/neigh/lo/retrans_time_ms
1576 snmpd 11 0 /proc/sys/net/ipv6/conf/lo/forwarding
1576 snmpd 11 0 /proc/sys/net/ipv6/neigh/lo/base_reachable_time_ms
1576 snmpd 9 0 /proc/diskstats
1576 snmpd 9 0 /proc/stat
1576 snmpd 9 0 /proc/vmstat
1956 supervise 9 0 supervise/status.new
1956 supervise 9 0 supervise/status.new
17358 run 3 0 /etc/ld.so.cache
17358 run 3 0 /lib/x86_64-linux-gnu/libtinfo.so.5
17358 run 3 0 /lib/x86_64-linux-gnu/libdl.so.2
17358 run 3 0 /lib/x86_64-linux-gnu/libc.so.6
17358 run -1 6 /dev/tty
17358 run 3 0 /proc/meminfo
17358 run 3 0 /etc/nsswitch.conf
17358 run 3 0 /etc/ld.so.cache
17358 run 3 0 /lib/x86_64-linux-gnu/libnss_compat.so.2
17358 run 3 0 /lib/x86_64-linux-gnu/libnsl.so.1
17358 run 3 0 /etc/ld.so.cache
17358 run 3 0 /lib/x86_64-linux-gnu/libnss_nis.so.2
17358 run 3 0 /lib/x86_64-linux-gnu/libnss_files.so.2
17358 run 3 0 /etc/passwd
17358 run 3 0 ./run
^C
While tracing, the snmpd process opened various /proc files (reading metrics),
and a "run" process read various libraries and config files (looks like it
was starting up: a new process).
opensnoop can be useful for discovering configuration and log files, if used
during application startup.
The -p option can be used to filter on a PID, which is filtered in-kernel. Here
I've used it with -t to print timestamps:
./opensnoop -tp 1956
TIME(s) PID COMM FD ERR PATH
0.000000000 1956 supervise 9 0 supervise/status.new
0.000289999 1956 supervise 9 0 supervise/status.new
1.023068000 1956 supervise 9 0 supervise/status.new
1.023381997 1956 supervise 9 0 supervise/status.new
2.046030000 1956 supervise 9 0 supervise/status.new
2.046363000 1956 supervise 9 0 supervise/status.new
3.068203997 1956 supervise 9 0 supervise/status.new
3.068544999 1956 supervise 9 0 supervise/status.new
This shows the supervise process is opening the status.new file twice every
second.
The -x option only prints failed opens:
# ./opensnoop -x
PID COMM FD ERR PATH
18372 run -1 6 /dev/tty
18373 run -1 6 /dev/tty
18373 multilog -1 13 lock
18372 multilog -1 13 lock
18384 df -1 2 /usr/share/locale/en_US.UTF-8/LC_MESSAGES/coreutils.mo
18384 df -1 2 /usr/share/locale/en_US.utf8/LC_MESSAGES/coreutils.mo
18384 df -1 2 /usr/share/locale/en_US/LC_MESSAGES/coreutils.mo
18384 df -1 2 /usr/share/locale/en.UTF-8/LC_MESSAGES/coreutils.mo
18384 df -1 2 /usr/share/locale/en.utf8/LC_MESSAGES/coreutils.mo
18384 df -1 2 /usr/share/locale/en/LC_MESSAGES/coreutils.mo
18384 df -1 2 /usr/share/locale-langpack/en_US.UTF-8/LC_MESSAGES/coreutils.mo
18384 df -1 2 /usr/share/locale-langpack/en_US.utf8/LC_MESSAGES/coreutils.mo
18384 df -1 2 /usr/share/locale-langpack/en_US/LC_MESSAGES/coreutils.mo
18384 df -1 2 /usr/share/locale-langpack/en.UTF-8/LC_MESSAGES/coreutils.mo
18384 df -1 2 /usr/share/locale-langpack/en.utf8/LC_MESSAGES/coreutils.mo
18384 df -1 2 /usr/share/locale-langpack/en/LC_MESSAGES/coreutils.mo
18385 run -1 6 /dev/tty
18386 run -1 6 /dev/tty
This caught a df command failing to open a coreutils.mo file, and trying from
different directories.
The ERR column is the system error number. Error number 2 is ENOENT: no such
file or directory.
USAGE message:
# ./opensnoop -h
usage: opensnoop [-h] [-t] [-x] [-p PID]
Trace open() syscalls
optional arguments:
-h, --help show this help message and exit
-t, --timestamp include timestamp on output
-x, --failed only show failed opens
-p PID, --pid PID trace this PID only
examples:
./opensnoop # trace all open() syscalls
./opensnoop -t # include timestamps
./opensnoop -x # only show failed opens
./opensnoop -p 181 # only trace PID 181
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