1 /*
2  * ring buffer based function tracer
3  *
4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
5  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
6  *
7  * Based on code from the latency_tracer, that is:
8  *
9  *  Copyright (C) 2004-2006 Ingo Molnar
10  *  Copyright (C) 2004 William Lee Irwin III
11  */
12 #include <linux/ring_buffer.h>
13 #include <linux/debugfs.h>
14 #include <linux/uaccess.h>
15 #include <linux/ftrace.h>
16 #include <linux/fs.h>
17 
18 #include "trace.h"
19 
20 /* function tracing enabled */
21 static int			ftrace_function_enabled;
22 
23 static struct trace_array	*func_trace;
24 
25 static void tracing_start_function_trace(void);
26 static void tracing_stop_function_trace(void);
27 
28 static int function_trace_init(struct trace_array *tr)
29 {
30 	func_trace = tr;
31 	tr->cpu = get_cpu();
32 	put_cpu();
33 
34 	tracing_start_cmdline_record();
35 	tracing_start_function_trace();
36 	return 0;
37 }
38 
39 static void function_trace_reset(struct trace_array *tr)
40 {
41 	tracing_stop_function_trace();
42 	tracing_stop_cmdline_record();
43 }
44 
45 static void function_trace_start(struct trace_array *tr)
46 {
47 	tracing_reset_online_cpus(tr);
48 }
49 
50 static void
51 function_trace_call_preempt_only(unsigned long ip, unsigned long parent_ip)
52 {
53 	struct trace_array *tr = func_trace;
54 	struct trace_array_cpu *data;
55 	unsigned long flags;
56 	long disabled;
57 	int cpu, resched;
58 	int pc;
59 
60 	if (unlikely(!ftrace_function_enabled))
61 		return;
62 
63 	pc = preempt_count();
64 	resched = ftrace_preempt_disable();
65 	local_save_flags(flags);
66 	cpu = raw_smp_processor_id();
67 	data = tr->data[cpu];
68 	disabled = atomic_inc_return(&data->disabled);
69 
70 	if (likely(disabled == 1))
71 		trace_function(tr, ip, parent_ip, flags, pc);
72 
73 	atomic_dec(&data->disabled);
74 	ftrace_preempt_enable(resched);
75 }
76 
77 static void
78 function_trace_call(unsigned long ip, unsigned long parent_ip)
79 {
80 	struct trace_array *tr = func_trace;
81 	struct trace_array_cpu *data;
82 	unsigned long flags;
83 	long disabled;
84 	int cpu;
85 	int pc;
86 
87 	if (unlikely(!ftrace_function_enabled))
88 		return;
89 
90 	/*
91 	 * Need to use raw, since this must be called before the
92 	 * recursive protection is performed.
93 	 */
94 	local_irq_save(flags);
95 	cpu = raw_smp_processor_id();
96 	data = tr->data[cpu];
97 	disabled = atomic_inc_return(&data->disabled);
98 
99 	if (likely(disabled == 1)) {
100 		pc = preempt_count();
101 		trace_function(tr, ip, parent_ip, flags, pc);
102 	}
103 
104 	atomic_dec(&data->disabled);
105 	local_irq_restore(flags);
106 }
107 
108 static void
109 function_stack_trace_call(unsigned long ip, unsigned long parent_ip)
110 {
111 	struct trace_array *tr = func_trace;
112 	struct trace_array_cpu *data;
113 	unsigned long flags;
114 	long disabled;
115 	int cpu;
116 	int pc;
117 
118 	if (unlikely(!ftrace_function_enabled))
119 		return;
120 
121 	/*
122 	 * Need to use raw, since this must be called before the
123 	 * recursive protection is performed.
124 	 */
125 	local_irq_save(flags);
126 	cpu = raw_smp_processor_id();
127 	data = tr->data[cpu];
128 	disabled = atomic_inc_return(&data->disabled);
129 
130 	if (likely(disabled == 1)) {
131 		pc = preempt_count();
132 		trace_function(tr, ip, parent_ip, flags, pc);
133 		/*
134 		 * skip over 5 funcs:
135 		 *    __ftrace_trace_stack,
136 		 *    __trace_stack,
137 		 *    function_stack_trace_call
138 		 *    ftrace_list_func
139 		 *    ftrace_call
140 		 */
141 		__trace_stack(tr, flags, 5, pc);
142 	}
143 
144 	atomic_dec(&data->disabled);
145 	local_irq_restore(flags);
146 }
147 
148 
149 static struct ftrace_ops trace_ops __read_mostly =
150 {
151 	.func = function_trace_call,
152 };
153 
154 static struct ftrace_ops trace_stack_ops __read_mostly =
155 {
156 	.func = function_stack_trace_call,
157 };
158 
159 /* Our two options */
160 enum {
161 	TRACE_FUNC_OPT_STACK = 0x1,
162 };
163 
164 static struct tracer_opt func_opts[] = {
165 #ifdef CONFIG_STACKTRACE
166 	{ TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
167 #endif
168 	{ } /* Always set a last empty entry */
169 };
170 
171 static struct tracer_flags func_flags = {
172 	.val = 0, /* By default: all flags disabled */
173 	.opts = func_opts
174 };
175 
176 static void tracing_start_function_trace(void)
177 {
178 	ftrace_function_enabled = 0;
179 
180 	if (trace_flags & TRACE_ITER_PREEMPTONLY)
181 		trace_ops.func = function_trace_call_preempt_only;
182 	else
183 		trace_ops.func = function_trace_call;
184 
185 	if (func_flags.val & TRACE_FUNC_OPT_STACK)
186 		register_ftrace_function(&trace_stack_ops);
187 	else
188 		register_ftrace_function(&trace_ops);
189 
190 	ftrace_function_enabled = 1;
191 }
192 
193 static void tracing_stop_function_trace(void)
194 {
195 	ftrace_function_enabled = 0;
196 
197 	if (func_flags.val & TRACE_FUNC_OPT_STACK)
198 		unregister_ftrace_function(&trace_stack_ops);
199 	else
200 		unregister_ftrace_function(&trace_ops);
201 }
202 
203 static int func_set_flag(u32 old_flags, u32 bit, int set)
204 {
205 	if (bit == TRACE_FUNC_OPT_STACK) {
206 		/* do nothing if already set */
207 		if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
208 			return 0;
209 
210 		if (set) {
211 			unregister_ftrace_function(&trace_ops);
212 			register_ftrace_function(&trace_stack_ops);
213 		} else {
214 			unregister_ftrace_function(&trace_stack_ops);
215 			register_ftrace_function(&trace_ops);
216 		}
217 
218 		return 0;
219 	}
220 
221 	return -EINVAL;
222 }
223 
224 static struct tracer function_trace __read_mostly =
225 {
226 	.name		= "function",
227 	.init		= function_trace_init,
228 	.reset		= function_trace_reset,
229 	.start		= function_trace_start,
230 	.wait_pipe	= poll_wait_pipe,
231 	.flags		= &func_flags,
232 	.set_flag	= func_set_flag,
233 #ifdef CONFIG_FTRACE_SELFTEST
234 	.selftest	= trace_selftest_startup_function,
235 #endif
236 };
237 
238 #ifdef CONFIG_DYNAMIC_FTRACE
239 static void
240 ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
241 {
242 	long *count = (long *)data;
243 
244 	if (tracing_is_on())
245 		return;
246 
247 	if (!*count)
248 		return;
249 
250 	if (*count != -1)
251 		(*count)--;
252 
253 	tracing_on();
254 }
255 
256 static void
257 ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
258 {
259 	long *count = (long *)data;
260 
261 	if (!tracing_is_on())
262 		return;
263 
264 	if (!*count)
265 		return;
266 
267 	if (*count != -1)
268 		(*count)--;
269 
270 	tracing_off();
271 }
272 
273 static int
274 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
275 			 struct ftrace_probe_ops *ops, void *data);
276 
277 static struct ftrace_probe_ops traceon_probe_ops = {
278 	.func			= ftrace_traceon,
279 	.print			= ftrace_trace_onoff_print,
280 };
281 
282 static struct ftrace_probe_ops traceoff_probe_ops = {
283 	.func			= ftrace_traceoff,
284 	.print			= ftrace_trace_onoff_print,
285 };
286 
287 static int
288 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
289 			 struct ftrace_probe_ops *ops, void *data)
290 {
291 	long count = (long)data;
292 
293 	seq_printf(m, "%ps:", (void *)ip);
294 
295 	if (ops == &traceon_probe_ops)
296 		seq_printf(m, "traceon");
297 	else
298 		seq_printf(m, "traceoff");
299 
300 	if (count == -1)
301 		seq_printf(m, ":unlimited\n");
302 	else
303 		seq_printf(m, ":count=%ld\n", count);
304 
305 	return 0;
306 }
307 
308 static int
309 ftrace_trace_onoff_unreg(char *glob, char *cmd, char *param)
310 {
311 	struct ftrace_probe_ops *ops;
312 
313 	/* we register both traceon and traceoff to this callback */
314 	if (strcmp(cmd, "traceon") == 0)
315 		ops = &traceon_probe_ops;
316 	else
317 		ops = &traceoff_probe_ops;
318 
319 	unregister_ftrace_function_probe_func(glob, ops);
320 
321 	return 0;
322 }
323 
324 static int
325 ftrace_trace_onoff_callback(char *glob, char *cmd, char *param, int enable)
326 {
327 	struct ftrace_probe_ops *ops;
328 	void *count = (void *)-1;
329 	char *number;
330 	int ret;
331 
332 	/* hash funcs only work with set_ftrace_filter */
333 	if (!enable)
334 		return -EINVAL;
335 
336 	if (glob[0] == '!')
337 		return ftrace_trace_onoff_unreg(glob+1, cmd, param);
338 
339 	/* we register both traceon and traceoff to this callback */
340 	if (strcmp(cmd, "traceon") == 0)
341 		ops = &traceon_probe_ops;
342 	else
343 		ops = &traceoff_probe_ops;
344 
345 	if (!param)
346 		goto out_reg;
347 
348 	number = strsep(&param, ":");
349 
350 	if (!strlen(number))
351 		goto out_reg;
352 
353 	/*
354 	 * We use the callback data field (which is a pointer)
355 	 * as our counter.
356 	 */
357 	ret = strict_strtoul(number, 0, (unsigned long *)&count);
358 	if (ret)
359 		return ret;
360 
361  out_reg:
362 	ret = register_ftrace_function_probe(glob, ops, count);
363 
364 	return ret < 0 ? ret : 0;
365 }
366 
367 static struct ftrace_func_command ftrace_traceon_cmd = {
368 	.name			= "traceon",
369 	.func			= ftrace_trace_onoff_callback,
370 };
371 
372 static struct ftrace_func_command ftrace_traceoff_cmd = {
373 	.name			= "traceoff",
374 	.func			= ftrace_trace_onoff_callback,
375 };
376 
377 static int __init init_func_cmd_traceon(void)
378 {
379 	int ret;
380 
381 	ret = register_ftrace_command(&ftrace_traceoff_cmd);
382 	if (ret)
383 		return ret;
384 
385 	ret = register_ftrace_command(&ftrace_traceon_cmd);
386 	if (ret)
387 		unregister_ftrace_command(&ftrace_traceoff_cmd);
388 	return ret;
389 }
390 #else
391 static inline int init_func_cmd_traceon(void)
392 {
393 	return 0;
394 }
395 #endif /* CONFIG_DYNAMIC_FTRACE */
396 
397 static __init int init_function_trace(void)
398 {
399 	init_func_cmd_traceon();
400 	return register_tracer(&function_trace);
401 }
402 device_initcall(init_function_trace);
403 
404