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 Nadia Yvette Chambers
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->trace_buffer.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->trace_buffer);
48 }
49 
50 /* Our option */
51 enum {
52 	TRACE_FUNC_OPT_STACK	= 0x1,
53 };
54 
55 static struct tracer_flags func_flags;
56 
57 static void
58 function_trace_call(unsigned long ip, unsigned long parent_ip,
59 		    struct ftrace_ops *op, struct pt_regs *pt_regs)
60 {
61 	struct trace_array *tr = func_trace;
62 	struct trace_array_cpu *data;
63 	unsigned long flags;
64 	int bit;
65 	int cpu;
66 	int pc;
67 
68 	if (unlikely(!ftrace_function_enabled))
69 		return;
70 
71 	pc = preempt_count();
72 	preempt_disable_notrace();
73 
74 	bit = trace_test_and_set_recursion(TRACE_FTRACE_START, TRACE_FTRACE_MAX);
75 	if (bit < 0)
76 		goto out;
77 
78 	cpu = smp_processor_id();
79 	data = per_cpu_ptr(tr->trace_buffer.data, cpu);
80 	if (!atomic_read(&data->disabled)) {
81 		local_save_flags(flags);
82 		trace_function(tr, ip, parent_ip, flags, pc);
83 	}
84 	trace_clear_recursion(bit);
85 
86  out:
87 	preempt_enable_notrace();
88 }
89 
90 static void
91 function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
92 			  struct ftrace_ops *op, struct pt_regs *pt_regs)
93 {
94 	struct trace_array *tr = func_trace;
95 	struct trace_array_cpu *data;
96 	unsigned long flags;
97 	long disabled;
98 	int cpu;
99 	int pc;
100 
101 	if (unlikely(!ftrace_function_enabled))
102 		return;
103 
104 	/*
105 	 * Need to use raw, since this must be called before the
106 	 * recursive protection is performed.
107 	 */
108 	local_irq_save(flags);
109 	cpu = raw_smp_processor_id();
110 	data = per_cpu_ptr(tr->trace_buffer.data, cpu);
111 	disabled = atomic_inc_return(&data->disabled);
112 
113 	if (likely(disabled == 1)) {
114 		pc = preempt_count();
115 		trace_function(tr, ip, parent_ip, flags, pc);
116 		/*
117 		 * skip over 5 funcs:
118 		 *    __ftrace_trace_stack,
119 		 *    __trace_stack,
120 		 *    function_stack_trace_call
121 		 *    ftrace_list_func
122 		 *    ftrace_call
123 		 */
124 		__trace_stack(tr, flags, 5, pc);
125 	}
126 
127 	atomic_dec(&data->disabled);
128 	local_irq_restore(flags);
129 }
130 
131 
132 static struct ftrace_ops trace_ops __read_mostly =
133 {
134 	.func = function_trace_call,
135 	.flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
136 };
137 
138 static struct ftrace_ops trace_stack_ops __read_mostly =
139 {
140 	.func = function_stack_trace_call,
141 	.flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
142 };
143 
144 static struct tracer_opt func_opts[] = {
145 #ifdef CONFIG_STACKTRACE
146 	{ TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
147 #endif
148 	{ } /* Always set a last empty entry */
149 };
150 
151 static struct tracer_flags func_flags = {
152 	.val = 0, /* By default: all flags disabled */
153 	.opts = func_opts
154 };
155 
156 static void tracing_start_function_trace(void)
157 {
158 	ftrace_function_enabled = 0;
159 
160 	if (func_flags.val & TRACE_FUNC_OPT_STACK)
161 		register_ftrace_function(&trace_stack_ops);
162 	else
163 		register_ftrace_function(&trace_ops);
164 
165 	ftrace_function_enabled = 1;
166 }
167 
168 static void tracing_stop_function_trace(void)
169 {
170 	ftrace_function_enabled = 0;
171 
172 	if (func_flags.val & TRACE_FUNC_OPT_STACK)
173 		unregister_ftrace_function(&trace_stack_ops);
174 	else
175 		unregister_ftrace_function(&trace_ops);
176 }
177 
178 static int func_set_flag(u32 old_flags, u32 bit, int set)
179 {
180 	switch (bit) {
181 	case TRACE_FUNC_OPT_STACK:
182 		/* do nothing if already set */
183 		if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
184 			break;
185 
186 		if (set) {
187 			unregister_ftrace_function(&trace_ops);
188 			register_ftrace_function(&trace_stack_ops);
189 		} else {
190 			unregister_ftrace_function(&trace_stack_ops);
191 			register_ftrace_function(&trace_ops);
192 		}
193 
194 		break;
195 	default:
196 		return -EINVAL;
197 	}
198 
199 	return 0;
200 }
201 
202 static struct tracer function_trace __tracer_data =
203 {
204 	.name		= "function",
205 	.init		= function_trace_init,
206 	.reset		= function_trace_reset,
207 	.start		= function_trace_start,
208 	.wait_pipe	= poll_wait_pipe,
209 	.flags		= &func_flags,
210 	.set_flag	= func_set_flag,
211 #ifdef CONFIG_FTRACE_SELFTEST
212 	.selftest	= trace_selftest_startup_function,
213 #endif
214 };
215 
216 #ifdef CONFIG_DYNAMIC_FTRACE
217 static int update_count(void **data)
218 {
219 	unsigned long *count = (long *)data;
220 
221 	if (!*count)
222 		return 0;
223 
224 	if (*count != -1)
225 		(*count)--;
226 
227 	return 1;
228 }
229 
230 static void
231 ftrace_traceon_count(unsigned long ip, unsigned long parent_ip, void **data)
232 {
233 	if (tracing_is_on())
234 		return;
235 
236 	if (update_count(data))
237 		tracing_on();
238 }
239 
240 static void
241 ftrace_traceoff_count(unsigned long ip, unsigned long parent_ip, void **data)
242 {
243 	if (!tracing_is_on())
244 		return;
245 
246 	if (update_count(data))
247 		tracing_off();
248 }
249 
250 static void
251 ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
252 {
253 	if (tracing_is_on())
254 		return;
255 
256 	tracing_on();
257 }
258 
259 static void
260 ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
261 {
262 	if (!tracing_is_on())
263 		return;
264 
265 	tracing_off();
266 }
267 
268 /*
269  * Skip 4:
270  *   ftrace_stacktrace()
271  *   function_trace_probe_call()
272  *   ftrace_ops_list_func()
273  *   ftrace_call()
274  */
275 #define STACK_SKIP 4
276 
277 static void
278 ftrace_stacktrace(unsigned long ip, unsigned long parent_ip, void **data)
279 {
280 	trace_dump_stack(STACK_SKIP);
281 }
282 
283 static void
284 ftrace_stacktrace_count(unsigned long ip, unsigned long parent_ip, void **data)
285 {
286 	if (!tracing_is_on())
287 		return;
288 
289 	if (update_count(data))
290 		trace_dump_stack(STACK_SKIP);
291 }
292 
293 static void
294 ftrace_dump_probe(unsigned long ip, unsigned long parent_ip, void **data)
295 {
296 	if (update_count(data))
297 		ftrace_dump(DUMP_ALL);
298 }
299 
300 /* Only dump the current CPU buffer. */
301 static void
302 ftrace_cpudump_probe(unsigned long ip, unsigned long parent_ip, void **data)
303 {
304 	if (update_count(data))
305 		ftrace_dump(DUMP_ORIG);
306 }
307 
308 static int
309 ftrace_probe_print(const char *name, struct seq_file *m,
310 		   unsigned long ip, void *data)
311 {
312 	long count = (long)data;
313 
314 	seq_printf(m, "%ps:%s", (void *)ip, name);
315 
316 	if (count == -1)
317 		seq_printf(m, ":unlimited\n");
318 	else
319 		seq_printf(m, ":count=%ld\n", count);
320 
321 	return 0;
322 }
323 
324 static int
325 ftrace_traceon_print(struct seq_file *m, unsigned long ip,
326 			 struct ftrace_probe_ops *ops, void *data)
327 {
328 	return ftrace_probe_print("traceon", m, ip, data);
329 }
330 
331 static int
332 ftrace_traceoff_print(struct seq_file *m, unsigned long ip,
333 			 struct ftrace_probe_ops *ops, void *data)
334 {
335 	return ftrace_probe_print("traceoff", m, ip, data);
336 }
337 
338 static int
339 ftrace_stacktrace_print(struct seq_file *m, unsigned long ip,
340 			struct ftrace_probe_ops *ops, void *data)
341 {
342 	return ftrace_probe_print("stacktrace", m, ip, data);
343 }
344 
345 static int
346 ftrace_dump_print(struct seq_file *m, unsigned long ip,
347 			struct ftrace_probe_ops *ops, void *data)
348 {
349 	return ftrace_probe_print("dump", m, ip, data);
350 }
351 
352 static int
353 ftrace_cpudump_print(struct seq_file *m, unsigned long ip,
354 			struct ftrace_probe_ops *ops, void *data)
355 {
356 	return ftrace_probe_print("cpudump", m, ip, data);
357 }
358 
359 static struct ftrace_probe_ops traceon_count_probe_ops = {
360 	.func			= ftrace_traceon_count,
361 	.print			= ftrace_traceon_print,
362 };
363 
364 static struct ftrace_probe_ops traceoff_count_probe_ops = {
365 	.func			= ftrace_traceoff_count,
366 	.print			= ftrace_traceoff_print,
367 };
368 
369 static struct ftrace_probe_ops stacktrace_count_probe_ops = {
370 	.func			= ftrace_stacktrace_count,
371 	.print			= ftrace_stacktrace_print,
372 };
373 
374 static struct ftrace_probe_ops dump_probe_ops = {
375 	.func			= ftrace_dump_probe,
376 	.print			= ftrace_dump_print,
377 };
378 
379 static struct ftrace_probe_ops cpudump_probe_ops = {
380 	.func			= ftrace_cpudump_probe,
381 	.print			= ftrace_cpudump_print,
382 };
383 
384 static struct ftrace_probe_ops traceon_probe_ops = {
385 	.func			= ftrace_traceon,
386 	.print			= ftrace_traceon_print,
387 };
388 
389 static struct ftrace_probe_ops traceoff_probe_ops = {
390 	.func			= ftrace_traceoff,
391 	.print			= ftrace_traceoff_print,
392 };
393 
394 static struct ftrace_probe_ops stacktrace_probe_ops = {
395 	.func			= ftrace_stacktrace,
396 	.print			= ftrace_stacktrace_print,
397 };
398 
399 static int
400 ftrace_trace_probe_callback(struct ftrace_probe_ops *ops,
401 			    struct ftrace_hash *hash, char *glob,
402 			    char *cmd, char *param, int enable)
403 {
404 	void *count = (void *)-1;
405 	char *number;
406 	int ret;
407 
408 	/* hash funcs only work with set_ftrace_filter */
409 	if (!enable)
410 		return -EINVAL;
411 
412 	if (glob[0] == '!') {
413 		unregister_ftrace_function_probe_func(glob+1, ops);
414 		return 0;
415 	}
416 
417 	if (!param)
418 		goto out_reg;
419 
420 	number = strsep(&param, ":");
421 
422 	if (!strlen(number))
423 		goto out_reg;
424 
425 	/*
426 	 * We use the callback data field (which is a pointer)
427 	 * as our counter.
428 	 */
429 	ret = kstrtoul(number, 0, (unsigned long *)&count);
430 	if (ret)
431 		return ret;
432 
433  out_reg:
434 	ret = register_ftrace_function_probe(glob, ops, count);
435 
436 	return ret < 0 ? ret : 0;
437 }
438 
439 static int
440 ftrace_trace_onoff_callback(struct ftrace_hash *hash,
441 			    char *glob, char *cmd, char *param, int enable)
442 {
443 	struct ftrace_probe_ops *ops;
444 
445 	/* we register both traceon and traceoff to this callback */
446 	if (strcmp(cmd, "traceon") == 0)
447 		ops = param ? &traceon_count_probe_ops : &traceon_probe_ops;
448 	else
449 		ops = param ? &traceoff_count_probe_ops : &traceoff_probe_ops;
450 
451 	return ftrace_trace_probe_callback(ops, hash, glob, cmd,
452 					   param, enable);
453 }
454 
455 static int
456 ftrace_stacktrace_callback(struct ftrace_hash *hash,
457 			   char *glob, char *cmd, char *param, int enable)
458 {
459 	struct ftrace_probe_ops *ops;
460 
461 	ops = param ? &stacktrace_count_probe_ops : &stacktrace_probe_ops;
462 
463 	return ftrace_trace_probe_callback(ops, hash, glob, cmd,
464 					   param, enable);
465 }
466 
467 static int
468 ftrace_dump_callback(struct ftrace_hash *hash,
469 			   char *glob, char *cmd, char *param, int enable)
470 {
471 	struct ftrace_probe_ops *ops;
472 
473 	ops = &dump_probe_ops;
474 
475 	/* Only dump once. */
476 	return ftrace_trace_probe_callback(ops, hash, glob, cmd,
477 					   "1", enable);
478 }
479 
480 static int
481 ftrace_cpudump_callback(struct ftrace_hash *hash,
482 			   char *glob, char *cmd, char *param, int enable)
483 {
484 	struct ftrace_probe_ops *ops;
485 
486 	ops = &cpudump_probe_ops;
487 
488 	/* Only dump once. */
489 	return ftrace_trace_probe_callback(ops, hash, glob, cmd,
490 					   "1", enable);
491 }
492 
493 static struct ftrace_func_command ftrace_traceon_cmd = {
494 	.name			= "traceon",
495 	.func			= ftrace_trace_onoff_callback,
496 };
497 
498 static struct ftrace_func_command ftrace_traceoff_cmd = {
499 	.name			= "traceoff",
500 	.func			= ftrace_trace_onoff_callback,
501 };
502 
503 static struct ftrace_func_command ftrace_stacktrace_cmd = {
504 	.name			= "stacktrace",
505 	.func			= ftrace_stacktrace_callback,
506 };
507 
508 static struct ftrace_func_command ftrace_dump_cmd = {
509 	.name			= "dump",
510 	.func			= ftrace_dump_callback,
511 };
512 
513 static struct ftrace_func_command ftrace_cpudump_cmd = {
514 	.name			= "cpudump",
515 	.func			= ftrace_cpudump_callback,
516 };
517 
518 static int __init init_func_cmd_traceon(void)
519 {
520 	int ret;
521 
522 	ret = register_ftrace_command(&ftrace_traceoff_cmd);
523 	if (ret)
524 		return ret;
525 
526 	ret = register_ftrace_command(&ftrace_traceon_cmd);
527 	if (ret)
528 		goto out_free_traceoff;
529 
530 	ret = register_ftrace_command(&ftrace_stacktrace_cmd);
531 	if (ret)
532 		goto out_free_traceon;
533 
534 	ret = register_ftrace_command(&ftrace_dump_cmd);
535 	if (ret)
536 		goto out_free_stacktrace;
537 
538 	ret = register_ftrace_command(&ftrace_cpudump_cmd);
539 	if (ret)
540 		goto out_free_dump;
541 
542 	return 0;
543 
544  out_free_dump:
545 	unregister_ftrace_command(&ftrace_dump_cmd);
546  out_free_stacktrace:
547 	unregister_ftrace_command(&ftrace_stacktrace_cmd);
548  out_free_traceon:
549 	unregister_ftrace_command(&ftrace_traceon_cmd);
550  out_free_traceoff:
551 	unregister_ftrace_command(&ftrace_traceoff_cmd);
552 
553 	return ret;
554 }
555 #else
556 static inline int init_func_cmd_traceon(void)
557 {
558 	return 0;
559 }
560 #endif /* CONFIG_DYNAMIC_FTRACE */
561 
562 static __init int init_function_trace(void)
563 {
564 	init_func_cmd_traceon();
565 	return register_tracer(&function_trace);
566 }
567 core_initcall(init_function_trace);
568