1 // SPDX-License-Identifier: GPL-2.0 <<
2 /* 1 /*
3 * nop tracer 2 * nop tracer
4 * 3 *
5 * Copyright (C) 2008 Steven Noonan <steven@up 4 * Copyright (C) 2008 Steven Noonan <steven@uplinklabs.net>
6 * 5 *
7 */ 6 */
8 7
9 #include <linux/module.h> 8 #include <linux/module.h>
10 #include <linux/ftrace.h> 9 #include <linux/ftrace.h>
11 10
12 #include "trace.h" 11 #include "trace.h"
13 12
14 /* Our two options */ 13 /* Our two options */
15 enum { 14 enum {
16 TRACE_NOP_OPT_ACCEPT = 0x1, 15 TRACE_NOP_OPT_ACCEPT = 0x1,
17 TRACE_NOP_OPT_REFUSE = 0x2 16 TRACE_NOP_OPT_REFUSE = 0x2
18 }; 17 };
19 18
20 /* Options for the tracer (see trace_options f 19 /* Options for the tracer (see trace_options file) */
21 static struct tracer_opt nop_opts[] = { 20 static struct tracer_opt nop_opts[] = {
22 /* Option that will be accepted by set 21 /* Option that will be accepted by set_flag callback */
23 { TRACER_OPT(test_nop_accept, TRACE_NO 22 { TRACER_OPT(test_nop_accept, TRACE_NOP_OPT_ACCEPT) },
24 /* Option that will be refused by set_ 23 /* Option that will be refused by set_flag callback */
25 { TRACER_OPT(test_nop_refuse, TRACE_NO 24 { TRACER_OPT(test_nop_refuse, TRACE_NOP_OPT_REFUSE) },
26 { } /* Always set a last empty entry * 25 { } /* Always set a last empty entry */
27 }; 26 };
28 27
29 static struct tracer_flags nop_flags = { 28 static struct tracer_flags nop_flags = {
30 /* You can check your flags value here 29 /* You can check your flags value here when you want. */
31 .val = 0, /* By default: all flags dis 30 .val = 0, /* By default: all flags disabled */
32 .opts = nop_opts 31 .opts = nop_opts
33 }; 32 };
34 33
35 static struct trace_array *ctx_trace; 34 static struct trace_array *ctx_trace;
36 35
37 static void start_nop_trace(struct trace_array 36 static void start_nop_trace(struct trace_array *tr)
38 { 37 {
39 /* Nothing to do! */ 38 /* Nothing to do! */
40 } 39 }
41 40
42 static void stop_nop_trace(struct trace_array 41 static void stop_nop_trace(struct trace_array *tr)
43 { 42 {
44 /* Nothing to do! */ 43 /* Nothing to do! */
45 } 44 }
46 45
47 static int nop_trace_init(struct trace_array * 46 static int nop_trace_init(struct trace_array *tr)
48 { 47 {
49 ctx_trace = tr; 48 ctx_trace = tr;
50 start_nop_trace(tr); 49 start_nop_trace(tr);
51 return 0; 50 return 0;
52 } 51 }
53 52
54 static void nop_trace_reset(struct trace_array 53 static void nop_trace_reset(struct trace_array *tr)
55 { 54 {
56 stop_nop_trace(tr); 55 stop_nop_trace(tr);
57 } 56 }
58 57
59 /* It only serves as a signal handler and a ca 58 /* It only serves as a signal handler and a callback to
60 * accept or refuse the setting of a flag. 59 * accept or refuse the setting of a flag.
61 * If you don't implement it, then the flag se 60 * If you don't implement it, then the flag setting will be
62 * automatically accepted. 61 * automatically accepted.
63 */ 62 */
64 static int nop_set_flag(struct trace_array *tr 63 static int nop_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
65 { 64 {
66 /* 65 /*
67 * Note that you don't need to update 66 * Note that you don't need to update nop_flags.val yourself.
68 * The tracing Api will do it automati 67 * The tracing Api will do it automatically if you return 0
69 */ 68 */
70 if (bit == TRACE_NOP_OPT_ACCEPT) { 69 if (bit == TRACE_NOP_OPT_ACCEPT) {
71 printk(KERN_DEBUG "nop_test_ac 70 printk(KERN_DEBUG "nop_test_accept flag set to %d: we accept."
72 " Now cat trace_option 71 " Now cat trace_options to see the result\n",
73 set); 72 set);
74 return 0; 73 return 0;
75 } 74 }
76 75
77 if (bit == TRACE_NOP_OPT_REFUSE) { 76 if (bit == TRACE_NOP_OPT_REFUSE) {
78 printk(KERN_DEBUG "nop_test_re 77 printk(KERN_DEBUG "nop_test_refuse flag set to %d: we refuse."
79 " Now cat trace_option 78 " Now cat trace_options to see the result\n",
80 set); 79 set);
81 return -EINVAL; 80 return -EINVAL;
82 } 81 }
83 82
84 return 0; 83 return 0;
85 } 84 }
86 85
87 86
88 struct tracer nop_trace __read_mostly = 87 struct tracer nop_trace __read_mostly =
89 { 88 {
90 .name = "nop", 89 .name = "nop",
91 .init = nop_trace_init, 90 .init = nop_trace_init,
92 .reset = nop_trace_reset, 91 .reset = nop_trace_reset,
93 #ifdef CONFIG_FTRACE_SELFTEST 92 #ifdef CONFIG_FTRACE_SELFTEST
94 .selftest = trace_selftest_start 93 .selftest = trace_selftest_startup_nop,
95 #endif 94 #endif
96 .flags = &nop_flags, 95 .flags = &nop_flags,
97 .set_flag = nop_set_flag, 96 .set_flag = nop_set_flag,
98 .allow_instances = true, 97 .allow_instances = true,
99 }; 98 };
100 99
101 100
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