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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 */ |
16 | enum { |
17 | TRACE_NOP_OPT_ACCEPT = 0x1, |
18 | TRACE_NOP_OPT_REFUSE = 0x2 |
19 | }; |
20 | |
21 | /* Options for the tracer (see trace_options file) */ |
22 | static 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 | |
30 | static 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 | |
36 | static struct trace_array *ctx_trace; |
37 | |
38 | static void start_nop_trace(struct trace_array *tr) |
39 | { |
40 | /* Nothing to do! */ |
41 | } |
42 | |
43 | static void stop_nop_trace(struct trace_array *tr) |
44 | { |
45 | /* Nothing to do! */ |
46 | } |
47 | |
48 | static int nop_trace_init(struct trace_array *tr) |
49 | { |
50 | ctx_trace = tr; |
51 | start_nop_trace(tr); |
52 | return 0; |
53 | } |
54 | |
55 | static 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 | */ |
65 | static 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 | |
89 | struct 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 |
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