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fb1b6d8b SN |
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 | ||
0619faf6 FW |
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 | ||
fb1b6d8b SN |
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 | ||
1c80025a | 48 | static int nop_trace_init(struct trace_array *tr) |
fb1b6d8b SN |
49 | { |
50 | ctx_trace = tr; | |
c76f0694 | 51 | start_nop_trace(tr); |
1c80025a | 52 | return 0; |
fb1b6d8b SN |
53 | } |
54 | ||
55 | static void nop_trace_reset(struct trace_array *tr) | |
56 | { | |
c76f0694 | 57 | stop_nop_trace(tr); |
fb1b6d8b SN |
58 | } |
59 | ||
0619faf6 FW |
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 | ||
43a15386 | 89 | struct tracer nop_trace __read_mostly = |
fb1b6d8b SN |
90 | { |
91 | .name = "nop", | |
92 | .init = nop_trace_init, | |
93 | .reset = nop_trace_reset, | |
7e6ea92d | 94 | .wait_pipe = poll_wait_pipe, |
fb1b6d8b SN |
95 | #ifdef CONFIG_FTRACE_SELFTEST |
96 | .selftest = trace_selftest_startup_nop, | |
97 | #endif | |
0619faf6 FW |
98 | .flags = &nop_flags, |
99 | .set_flag = nop_set_flag | |
fb1b6d8b SN |
100 | }; |
101 |