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 __read_mostly =
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 int
294 ftrace_probe_print(const char *name, struct seq_file *m,
295 		   unsigned long ip, void *data)
296 {
297 	long count = (long)data;
298 
299 	seq_printf(m, "%ps:%s", (void *)ip, name);
300 
301 	if (count == -1)
302 		seq_printf(m, ":unlimited\n");
303 	else
304 		seq_printf(m, ":count=%ld\n", count);
305 
306 	return 0;
307 }
308 
309 static int
310 ftrace_traceon_print(struct seq_file *m, unsigned long ip,
311 			 struct ftrace_probe_ops *ops, void *data)
312 {
313 	return ftrace_probe_print("traceon", m, ip, data);
314 }
315 
316 static int
317 ftrace_traceoff_print(struct seq_file *m, unsigned long ip,
318 			 struct ftrace_probe_ops *ops, void *data)
319 {
320 	return ftrace_probe_print("traceoff", m, ip, data);
321 }
322 
323 static int
324 ftrace_stacktrace_print(struct seq_file *m, unsigned long ip,
325 			struct ftrace_probe_ops *ops, void *data)
326 {
327 	return ftrace_probe_print("stacktrace", m, ip, data);
328 }
329 
330 static struct ftrace_probe_ops traceon_count_probe_ops = {
331 	.func			= ftrace_traceon_count,
332 	.print			= ftrace_traceon_print,
333 };
334 
335 static struct ftrace_probe_ops traceoff_count_probe_ops = {
336 	.func			= ftrace_traceoff_count,
337 	.print			= ftrace_traceoff_print,
338 };
339 
340 static struct ftrace_probe_ops stacktrace_count_probe_ops = {
341 	.func			= ftrace_stacktrace_count,
342 	.print			= ftrace_stacktrace_print,
343 };
344 
345 static struct ftrace_probe_ops traceon_probe_ops = {
346 	.func			= ftrace_traceon,
347 	.print			= ftrace_traceon_print,
348 };
349 
350 static struct ftrace_probe_ops traceoff_probe_ops = {
351 	.func			= ftrace_traceoff,
352 	.print			= ftrace_traceoff_print,
353 };
354 
355 static struct ftrace_probe_ops stacktrace_probe_ops = {
356 	.func			= ftrace_stacktrace,
357 	.print			= ftrace_stacktrace_print,
358 };
359 
360 static int
361 ftrace_trace_probe_callback(struct ftrace_probe_ops *ops,
362 			    struct ftrace_hash *hash, char *glob,
363 			    char *cmd, char *param, int enable)
364 {
365 	void *count = (void *)-1;
366 	char *number;
367 	int ret;
368 
369 	/* hash funcs only work with set_ftrace_filter */
370 	if (!enable)
371 		return -EINVAL;
372 
373 	if (glob[0] == '!') {
374 		unregister_ftrace_function_probe_func(glob+1, ops);
375 		return 0;
376 	}
377 
378 	if (!param)
379 		goto out_reg;
380 
381 	number = strsep(&param, ":");
382 
383 	if (!strlen(number))
384 		goto out_reg;
385 
386 	/*
387 	 * We use the callback data field (which is a pointer)
388 	 * as our counter.
389 	 */
390 	ret = kstrtoul(number, 0, (unsigned long *)&count);
391 	if (ret)
392 		return ret;
393 
394  out_reg:
395 	ret = register_ftrace_function_probe(glob, ops, count);
396 
397 	return ret < 0 ? ret : 0;
398 }
399 
400 static int
401 ftrace_trace_onoff_callback(struct ftrace_hash *hash,
402 			    char *glob, char *cmd, char *param, int enable)
403 {
404 	struct ftrace_probe_ops *ops;
405 
406 	/* we register both traceon and traceoff to this callback */
407 	if (strcmp(cmd, "traceon") == 0)
408 		ops = param ? &traceon_count_probe_ops : &traceon_probe_ops;
409 	else
410 		ops = param ? &traceoff_count_probe_ops : &traceoff_probe_ops;
411 
412 	return ftrace_trace_probe_callback(ops, hash, glob, cmd,
413 					   param, enable);
414 }
415 
416 static int
417 ftrace_stacktrace_callback(struct ftrace_hash *hash,
418 			   char *glob, char *cmd, char *param, int enable)
419 {
420 	struct ftrace_probe_ops *ops;
421 
422 	ops = param ? &stacktrace_count_probe_ops : &stacktrace_probe_ops;
423 
424 	return ftrace_trace_probe_callback(ops, hash, glob, cmd,
425 					   param, enable);
426 }
427 
428 static struct ftrace_func_command ftrace_traceon_cmd = {
429 	.name			= "traceon",
430 	.func			= ftrace_trace_onoff_callback,
431 };
432 
433 static struct ftrace_func_command ftrace_traceoff_cmd = {
434 	.name			= "traceoff",
435 	.func			= ftrace_trace_onoff_callback,
436 };
437 
438 static struct ftrace_func_command ftrace_stacktrace_cmd = {
439 	.name			= "stacktrace",
440 	.func			= ftrace_stacktrace_callback,
441 };
442 
443 static int __init init_func_cmd_traceon(void)
444 {
445 	int ret;
446 
447 	ret = register_ftrace_command(&ftrace_traceoff_cmd);
448 	if (ret)
449 		return ret;
450 
451 	ret = register_ftrace_command(&ftrace_traceon_cmd);
452 	if (ret)
453 		unregister_ftrace_command(&ftrace_traceoff_cmd);
454 
455 	ret = register_ftrace_command(&ftrace_stacktrace_cmd);
456 	if (ret) {
457 		unregister_ftrace_command(&ftrace_traceoff_cmd);
458 		unregister_ftrace_command(&ftrace_traceon_cmd);
459 	}
460 	return ret;
461 }
462 #else
463 static inline int init_func_cmd_traceon(void)
464 {
465 	return 0;
466 }
467 #endif /* CONFIG_DYNAMIC_FTRACE */
468 
469 static __init int init_function_trace(void)
470 {
471 	init_func_cmd_traceon();
472 	return register_tracer(&function_trace);
473 }
474 core_initcall(init_function_trace);
475