FM / tracing

/usr/share/doc/bpfcc-tools/examples/tracing/

/usr/share/doc/bpfcc-tools/examples/tracing

Name	Size	Mode	Actions
biolatpcts.py	3312	0755	edit dl rm
biolatpcts_example.txt	650	0644	edit dl rm
bitehist.py	1397	0755	edit dl rm
bitehist_example.txt	1208	0644	edit dl rm
CMakeLists.txt	276	0644	edit dl rm
dddos.py	3818	0755	edit dl rm
dddos_example.txt	2112	0644	edit dl rm
disksnoop.py	1947	0755	edit dl rm
disksnoop_example.txt	1587	0644	edit dl rm
hello_fields.py	679	0755	edit dl rm
hello_perf_output.py	1270	0755	edit dl rm
hello_perf_output_using_ns.py	1843	0755	edit dl rm
kvm_hypercall.py	1520	0755	edit dl rm
kvm_hypercall.txt	1782	0644	edit dl rm
mallocstacks.py	1942	0755	edit dl rm
mysqld_query.py	1701	0755	edit dl rm
mysqld_query_example.txt	499	0644	edit dl rm
nflatency.py	6214	0755	edit dl rm
nodejs_http_server.py	1376	0755	edit dl rm
nodejs_http_server_example.txt	276	0644	edit dl rm
stacksnoop.py	3252	0755	edit dl rm
stacksnoop_example.txt	2871	0644	edit dl rm
stack_buildid_example.py	3106	0755	edit dl rm
strlen_count.py	1331	0755	edit dl rm
strlen_hist.py	1856	0755	edit dl rm
strlen_hist_ifunc.py	3800	0755	edit dl rm
strlen_snoop.py	1384	0755	edit dl rm
sync_timing.py	1390	0755	edit dl rm
task_switch.c	499	0644	edit dl rm
task_switch.py	486	0755	edit dl rm
tcpv4connect.py	2413	0755	edit dl rm
tcpv4connect_example.txt	1063	0644	edit dl rm
trace_fields.py	589	0755	edit dl rm
trace_perf_output.py	1600	0755	edit dl rm
undump.py	3602	0755	edit dl rm
undump_example.txt	886	0644	edit dl rm
urandomread-explicit.py	1511	0755	edit dl rm
urandomread.py	1032	0755	edit dl rm
urandomread_example.txt	675	0644	edit dl rm
vfsreadlat.c	896	0644	edit dl rm
vfsreadlat.py	1336	0755	edit dl rm
vfsreadlat_example.txt	3619	0644	edit dl rm

Edit: /usr/share/doc/bpfcc-tools/examples/tracing/urandomread-explicit.py (1511B)

#!/usr/bin/python
#
# urandomread-explicit  Example of instrumenting a kernel tracepoint.
#                       For Linux, uses BCC, BPF. Embedded C.
#
# This is an older example of instrumenting a tracepoint, which defines
# the argument struct and makes an explicit call to attach_tracepoint().
# See urandomread for a newer version that uses TRACEPOINT_PROBE().
#
# REQUIRES: Linux 4.7+ (BPF_PROG_TYPE_TRACEPOINT support).
#
# Test by running this, then in another shell, run:
#     dd if=/dev/urandom of=/dev/null bs=1k count=5
#
# Copyright 2016 Netflix, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")

from __future__ import print_function
from bcc import BPF
from bcc.utils import printb

# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>

struct urandom_read_args {
    // from /sys/kernel/debug/tracing/events/random/urandom_read/format
    u64 __unused__;
    u32 got_bits;
    u32 pool_left;
    u32 input_left;
};

int printarg(struct urandom_read_args *args) {
    bpf_trace_printk("%d\\n", args->got_bits);
    return 0;
}
"""

# load BPF program
b = BPF(text=bpf_text)
b.attach_tracepoint(tp="random:urandom_read", fn_name="printarg")

# header
print("%-18s %-16s %-6s %s" % ("TIME(s)", "COMM", "PID", "GOTBITS"))

# format output
while 1:
    try:
        (task, pid, cpu, flags, ts, msg) = b.trace_fields()
    except ValueError:
        continue
    except KeyboardInterrupt:
        exit()
    printb(b"%-18.9f %-16s %-6d %s" % (ts, task, pid, msg))

cmd: