bcc 之 opensnoop 工具的使用
2022-3-16
这篇文档主要演示了 opensnoop(Linux eBPF/bcc) 工具的使用.
示例 #
opensnoop 在系统范围内跟踪 open() 系统调用，并打印各种详细信息.
示例输出:
# ./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
在跟踪时，snmpd 进程打开了各种 /proc 文件(读取指标). 另外, 一个 “run” 进程读取各种库和配置文件(看起来像 正在启动: 一个新进程).
如果在应用程序启动期间使用, opensnoop 可用于发现配置和日志文件.
过滤 PID #
-p 选项可用于在内核中过滤 PID. 这里我将它与 -T 一起使用来打印时间戳:
$ ./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
这表明 supervise 进程每秒打开2次 status.new 文件.
包含/过滤 UID #
-U 选项在输出中包含 UID:
# ./opensnoop -U
UID PID COMM FD ERR PATH
0 27063 vminfo 5 0 /var/run/utmp
103 628 dbus-daemon -1 2 /usr/local/share/dbus-1/system-services
103 628 dbus-daemon 18 0 /usr/share/dbus-1/system-services
103 628 dbus-daemon -1 2 /lib/dbus-1/system-services
-u 选项过滤 UID:
# ./opensnoop -Uu 1000
UID PID COMM FD ERR PATH
1000 30240 ls 3 0 /etc/ld.so.cache
1000 30240 ls 3 0 /lib/x86_64-linux-gnu/libselinux.so.1
1000 30240 ls 3 0 /lib/x86_64-linux-gnu/libc.so.6
1000 30240 ls 3 0 /lib/x86_64-linux-gnu/libpcre.so.3
1000 30240 ls 3 0 /lib/x86_64-linux-gnu/libdl.so.2
1000 30240 ls 3 0 /lib/x86_64-linux-gnu/libpthread.so.0
过滤失败的 opens #
-x 选项仅打印失败的 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
18385 run -1 6 /dev/tty
18386 run -1 6 /dev/tty
这里捕获了一个 df 命令无法打开 coreutils.mo 文件, 并尝试从其他目录打开.
列 ERR 表示系统错误码, 2 代表 ENOENT: no such file or directory.
可以使用 -d 选项设置最长跟踪持续时间. 例如, 要跟踪 2秒:
# ./opensnoop -d 2
PID COMM FD ERR PATH
2191 indicator-multi 11 0 /sys/block
2191 indicator-multi 11 0 /sys/block
2191 indicator-multi 11 0 /sys/block
2191 indicator-multi 11 0 /sys/block
2191 indicator-multi 11 0 /sys/block
过滤进程名称 #
-n 选项可用于过滤进程名称(部分匹配):
# ./opensnoop -n ed
PID COMM FD ERR PATH
2679 sed 3 0 /etc/ld.so.cache
2679 sed 3 0 /lib/x86_64-linux-gnu/libselinux.so.1
2679 sed 3 0 /lib/x86_64-linux-gnu/libc.so.6
2679 sed 3 0 /lib/x86_64-linux-gnu/libpcre.so.3
2679 sed 3 0 /lib/x86_64-linux-gnu/libdl.so.2
2679 sed 3 0 /lib/x86_64-linux-gnu/libpthread.so.0
2679 sed 3 0 /proc/filesystems
2679 sed 3 0 /usr/lib/locale/locale-archive
2679 sed -1 2
2679 sed 3 0 /usr/lib/x86_64-linux-gnu/gconv/gconv-modules.cache
2679 sed 3 0 /dev/null
2680 sed 3 0 /etc/ld.so.cache
2680 sed 3 0 /lib/x86_64-linux-gnu/libselinux.so.1
2680 sed 3 0 /lib/x86_64-linux-gnu/libc.so.6
2680 sed 3 0 /lib/x86_64-linux-gnu/libpcre.so.3
2680 sed 3 0 /lib/x86_64-linux-gnu/libdl.so.2
2680 sed 3 0 /lib/x86_64-linux-gnu/libpthread.so.0
2680 sed 3 0 /proc/filesystems
2680 sed 3 0 /usr/lib/locale/locale-archive
2680 sed -1 2
^C
这里捕获了 “sed” 命令，是因为命令中使用了命令名称部分匹配 “-n ed”
过滤标志 #
-e 选项能打印出额外的列; 例如，以下输出包含传递给 open(2) 的标志(以八进制表示):
# ./opensnoop -e
PID COMM FD ERR FLAGS PATH
28512 sshd 10 0 00101101 /proc/self/oom_score_adj
28512 sshd 3 0 02100000 /etc/ld.so.cache
28512 sshd 3 0 02100000 /lib/x86_64-linux-gnu/libwrap.so.0
28512 sshd 3 0 02100000 /lib/x86_64-linux-gnu/libaudit.so.1
28512 sshd 3 0 02100000 /lib/x86_64-linux-gnu/libpam.so.0
28512 sshd 3 0 02100000 /lib/x86_64-linux-gnu/libselinux.so.1
28512 sshd 3 0 02100000 /lib/x86_64-linux-gnu/libsystemd.so.0
28512 sshd 3 0 02100000 /usr/lib/x86_64-linux-gnu/libcrypto.so.1.0.2
28512 sshd 3 0 02100000 /lib/x86_64-linux-gnu/libutil.so.1
-f 选项能基于 open(2) 调用的标志进行过滤, 比如:
# ./opensnoop -e -f O_WRONLY -f O_RDWR
PID COMM FD ERR FLAGS PATH
28084 clear_console 3 0 00100002 /dev/tty
28084 clear_console -1 13 00100002 /dev/tty0
28084 clear_console -1 13 00100001 /dev/tty0
28084 clear_console -1 13 00100002 /dev/console
28084 clear_console -1 13 00100001 /dev/console
28051 sshd 8 0 02100002 /var/run/utmp
28051 sshd 7 0 00100001 /var/log/wtmp
基于 cgroup 集进行过滤 #
–cgroupmap 选项基于 cgroup 集进行过滤, 它用于使用外部创建的映射.
# ./opensnoop --cgroupmap /sys/fs/bpf/test01
更多信息, 查看 docs/special_filtering.md
USAGE 说明 #
# ./opensnoop -h
usage: opensnoop.py [-h] [-T] [-U] [-x] [-p PID] [-t TID]
[--cgroupmap CGROUPMAP] [--mntnsmap MNTNSMAP] [-u UID]
[-d DURATION] [-n NAME] [-e] [-f FLAG_FILTER]
跟踪 open() 系统调用
optional arguments:
-h, --help show this help message and exit
-T, --timestamp include timestamp on output
-U, --print-uid include UID on output
-x, --failed only show failed opens
-p PID, --pid PID trace this PID only
-t TID, --tid TID trace this TID only
--cgroupmap CGROUPMAP
trace cgroups in this BPF map only
--mntnsmap MNTNSMAP trace mount namespaces in this BPF map on
-u UID, --uid UID trace this UID only
-d DURATION, --duration DURATION
total duration of trace in seconds
-n NAME, --name NAME only print process names containing this name
-e, --extended_fields
show extended fields
-f FLAG_FILTER, --flag_filter FLAG_FILTER
filter on flags argument (e.g., O_WRONLY)
examples:
./opensnoop # trace all open() syscalls
./opensnoop -T # include timestamps
./opensnoop -U # include UID
./opensnoop -x # only show failed opens
./opensnoop -p 181 # only trace PID 181
./opensnoop -t 123 # only trace TID 123
./opensnoop -u 1000 # only trace UID 1000
./opensnoop -d 10 # trace for 10 seconds only
./opensnoop -n main # only print process names containing "main"
./opensnoop -e # show extended fields
./opensnoop -f O_WRONLY -f O_RDWR # only print calls for writing
./opensnoop --cgroupmap mappath # only trace cgroups in this BPF map
./opensnoop --mntnsmap mappath # only trace mount namespaces in the map