Repository navigation
Expand file tree
/
Copy pathdcsnoop.py
More file actions
executable file
·118 lines (102 loc) · 2.91 KB
/
Copy pathdcsnoop.py
File metadata and controls
executable file
·118 lines (102 loc) · 2.91 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
#!/usr/bin/python
# @lint-avoid-python-3-compatibility-imports
#
# dcsnoop Trace directory entry cache (dcache) lookups.
# For Linux, uses BCC, eBPF. Embedded C.
#
# USAGE: dcsnoop [-h] [-a]
#
# By default, this traces every failed dcache lookup, and shows the process
# performing the lookup and the filename requested. A -a option can be used
# to show all lookups, not just failed ones.
#
# This uses kernel dynamic tracing of the d_lookup() function, and will need
# to be modified to match kernel changes.
#
# Also see dcstat(8), for per-second summaries.
#
# Copyright 2016 Netflix, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 09-Feb-2016 Brendan Gregg Created this.
from __future__ import print_function
from bcc import BPF
import argparse
import re
# arguments
examples = """examples:
./dcsnoop # trace failed dcache lookups
./dcsnoop -a # trace all dcache lookups
"""
parser = argparse.ArgumentParser(
description="Trace directory entry cache (dcache) lookups",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-a", "--all", action="store_true",
help="trace all lookups (default is fails only)")
args = parser.parse_args()
# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <linux/fs.h>
#include <linux/sched.h>
#define MAX_FILE_LEN 64
struct entry_t {
char name[MAX_FILE_LEN];
};
BPF_HASH(entrybypid, u32, struct entry_t);
/* from fs/namei.c: */
struct nameidata {
struct path path;
struct qstr last;
// [...]
};
int trace_fast(struct pt_regs *ctx, struct nameidata *nd, struct path *path)
{
bpf_trace_printk("R %s\\n", nd->last.name);
return 1;
}
int kprobe__d_lookup(struct pt_regs *ctx, const struct dentry *parent,
const struct qstr *name)
{
u32 pid = bpf_get_current_pid_tgid();
struct entry_t entry = {};
const char *fname = name->name;
if (fname) {
bpf_probe_read(&entry.name, sizeof(entry.name), (void *)fname);
}
entrybypid.update(&pid, &entry);
return 0;
}
int kretprobe__d_lookup(struct pt_regs *ctx)
{
u32 pid = bpf_get_current_pid_tgid();
struct entry_t *ep;
ep = entrybypid.lookup(&pid);
if (ep == 0) {
return 0; // missed entry
}
if (ctx->ax == 0) {
bpf_trace_printk("M %s\\n", ep->name);
}
entrybypid.delete(&pid);
return 0;
}
"""
# initialize BPF
b = BPF(text=bpf_text)
if args.all:
b.attach_kprobe(event="lookup_fast", fn_name="trace_fast")
# header
print("%-11s %-6s %-16s %1s %s" % ("TIME(s)", "PID", "COMM", "T", "FILE"))
start_ts = 0
# format output
while 1:
(task, pid, cpu, flags, ts, msg) = b.trace_fields()
try:
(type, file) = msg.split(" ", 1)
except ValueError:
continue
if start_ts == 0:
start_ts = ts
print("%-11.6f %-6s %-16s %1s %s" % (ts - start_ts, pid, task, type, file))