NAME

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

SYNOPSIS

killsnoop [-h] [-x] [-p PID]

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 (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 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