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