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 int cpu; 51 ctx_trace = tr; 52 53 for_each_online_cpu(cpu) 54 tracing_reset(tr, cpu); 55 56 start_nop_trace(tr); 57 return 0; 58 } 59 60 static void nop_trace_reset(struct trace_array *tr) 61 { 62 stop_nop_trace(tr); 63 } 64 65 /* It only serves as a signal handler and a callback to 66 * accept or refuse tthe setting of a flag. 67 * If you don't implement it, then the flag setting will be 68 * automatically accepted. 69 */ 70 static int nop_set_flag(u32 old_flags, u32 bit, int set) 71 { 72 /* 73 * Note that you don't need to update nop_flags.val yourself. 74 * The tracing Api will do it automatically if you return 0 75 */ 76 if (bit == TRACE_NOP_OPT_ACCEPT) { 77 printk(KERN_DEBUG "nop_test_accept flag set to %d: we accept." 78 " Now cat trace_options to see the result\n", 79 set); 80 return 0; 81 } 82 83 if (bit == TRACE_NOP_OPT_REFUSE) { 84 printk(KERN_DEBUG "nop_test_refuse flag set to %d: we refuse." 85 "Now cat trace_options to see the result\n", 86 set); 87 return -EINVAL; 88 } 89 90 return 0; 91 } 92 93 94 struct tracer nop_trace __read_mostly = 95 { 96 .name = "nop", 97 .init = nop_trace_init, 98 .reset = nop_trace_reset, 99 #ifdef CONFIG_FTRACE_SELFTEST 100 .selftest = trace_selftest_startup_nop, 101 #endif 102 .flags = &nop_flags, 103 .set_flag = nop_set_flag 104 }; 105 106