NAME¶

killsnoop - Trace signals issued by the kill() syscall. Uses Linux eBPF/bcc.

SYNOPSIS¶

killsnoop [-h] [-x] [-p PID] [-T PID] [-s SIGNAL]

DESCRIPTION¶

killsnoop traces the kill() syscall, to show signals sent via this method. This may be useful to troubleshoot failing applications, where an unknown mechanism is sending signals.

This works by tracing the kernel sys_kill() function using dynamic tracing, and will need updating to match any changes to this function.

This makes use of a Linux 4.4 feature (bpf_perf_event_output()); for kernels older than 4.4, see the version under tools/old, which uses an older mechanism.

Since this uses BPF, only the root user can use this tool.

REQUIREMENTS¶

CONFIG_BPF and bcc.

OPTIONS¶

-h

Print usage message.

-x

Only print failed kill() syscalls.

-p PID

Trace this process ID only which is the sender of signal (filtered in-kernel).

-T PID

Trace this target process ID only which is the receiver of signal (filtered in-kernel).

-s SIGNAL

Trace this signal only (filtered in-kernel).

EXAMPLES¶

Trace all kill() syscalls:

# killsnoop

Trace only kill() syscalls that failed:

# killsnoop -x

Trace PID 181 only:

# killsnoop -p 181

Trace target PID 189 only:

# killsnoop -T 189

Trace signal 9 only:

# killsnoop -s 9

FIELDS¶

TIME

Time of the kill call.

PID

Source process ID

COMM

Source process name

SIG

Signal number. See signal(7).

TPID

Target process ID

RES

Result. 0 == success, a negative value (of the error code) for failure.

OVERHEAD¶

This traces the kernel kill function and prints output for each event. As the rate of this is generally expected to be low (< 100/s), the overhead is also expected to be negligible. If you have an application that is calling a very high rate of kill()s for some reason, then test and understand overhead before use.

SOURCE¶

This is from bcc.

https://github.com/iovisor/bcc

Also look in the bcc distribution for a companion _examples.txt file containing example usage, output, and commentary for this tool.

OS¶

Linux

STABILITY¶

Unstable - in development.

AUTHOR¶

Brendan Gregg

SEE ALSO¶

opensnoop(8), funccount(8)