Root/kernel/trace/trace_nop.c

1/*
2 * nop tracer
3 *
4 * Copyright (C) 2008 Steven Noonan <steven@uplinklabs.net>
5 *
6 */
7
8#include <linux/module.h>
9#include <linux/fs.h>
10#include <linux/debugfs.h>
11#include <linux/ftrace.h>
12
13#include "trace.h"
14
15/* Our two options */
16enum {
17    TRACE_NOP_OPT_ACCEPT = 0x1,
18    TRACE_NOP_OPT_REFUSE = 0x2
19};
20
21/* Options for the tracer (see trace_options file) */
22static struct tracer_opt nop_opts[] = {
23    /* Option that will be accepted by set_flag callback */
24    { TRACER_OPT(test_nop_accept, TRACE_NOP_OPT_ACCEPT) },
25    /* Option that will be refused by set_flag callback */
26    { TRACER_OPT(test_nop_refuse, TRACE_NOP_OPT_REFUSE) },
27    { } /* Always set a last empty entry */
28};
29
30static struct tracer_flags nop_flags = {
31    /* You can check your flags value here when you want. */
32    .val = 0, /* By default: all flags disabled */
33    .opts = nop_opts
34};
35
36static struct trace_array *ctx_trace;
37
38static void start_nop_trace(struct trace_array *tr)
39{
40    /* Nothing to do! */
41}
42
43static void stop_nop_trace(struct trace_array *tr)
44{
45    /* Nothing to do! */
46}
47
48static int nop_trace_init(struct trace_array *tr)
49{
50    ctx_trace = tr;
51    start_nop_trace(tr);
52    return 0;
53}
54
55static void nop_trace_reset(struct trace_array *tr)
56{
57    stop_nop_trace(tr);
58}
59
60/* It only serves as a signal handler and a callback to
61 * accept or refuse tthe setting of a flag.
62 * If you don't implement it, then the flag setting will be
63 * automatically accepted.
64 */
65static int nop_set_flag(u32 old_flags, u32 bit, int set)
66{
67    /*
68     * Note that you don't need to update nop_flags.val yourself.
69     * The tracing Api will do it automatically if you return 0
70     */
71    if (bit == TRACE_NOP_OPT_ACCEPT) {
72        printk(KERN_DEBUG "nop_test_accept flag set to %d: we accept."
73            " Now cat trace_options to see the result\n",
74            set);
75        return 0;
76    }
77
78    if (bit == TRACE_NOP_OPT_REFUSE) {
79        printk(KERN_DEBUG "nop_test_refuse flag set to %d: we refuse."
80            "Now cat trace_options to see the result\n",
81            set);
82        return -EINVAL;
83    }
84
85    return 0;
86}
87
88
89struct tracer nop_trace __read_mostly =
90{
91    .name = "nop",
92    .init = nop_trace_init,
93    .reset = nop_trace_reset,
94    .wait_pipe = poll_wait_pipe,
95#ifdef CONFIG_FTRACE_SELFTEST
96    .selftest = trace_selftest_startup_nop,
97#endif
98    .flags = &nop_flags,
99    .set_flag = nop_set_flag
100};
101
102

Archive Download this file



interactive