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;
58 	int pc;
59 
60 	if (unlikely(!ftrace_function_enabled))
61 		return;
62 
63 	pc = preempt_count();
64 	preempt_disable_notrace();
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 	preempt_enable_notrace();
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 	.flags = FTRACE_OPS_FL_GLOBAL,
153 };
154 
155 static struct ftrace_ops trace_stack_ops __read_mostly =
156 {
157 	.func = function_stack_trace_call,
158 	.flags = FTRACE_OPS_FL_GLOBAL,
159 };
160 
161 /* Our two options */
162 enum {
163 	TRACE_FUNC_OPT_STACK = 0x1,
164 };
165 
166 static struct tracer_opt func_opts[] = {
167 #ifdef CONFIG_STACKTRACE
168 	{ TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
169 #endif
170 	{ } /* Always set a last empty entry */
171 };
172 
173 static struct tracer_flags func_flags = {
174 	.val = 0, /* By default: all flags disabled */
175 	.opts = func_opts
176 };
177 
178 static void tracing_start_function_trace(void)
179 {
180 	ftrace_function_enabled = 0;
181 
182 	if (trace_flags & TRACE_ITER_PREEMPTONLY)
183 		trace_ops.func = function_trace_call_preempt_only;
184 	else
185 		trace_ops.func = function_trace_call;
186 
187 	if (func_flags.val & TRACE_FUNC_OPT_STACK)
188 		register_ftrace_function(&trace_stack_ops);
189 	else
190 		register_ftrace_function(&trace_ops);
191 
192 	ftrace_function_enabled = 1;
193 }
194 
195 static void tracing_stop_function_trace(void)
196 {
197 	ftrace_function_enabled = 0;
198 
199 	if (func_flags.val & TRACE_FUNC_OPT_STACK)
200 		unregister_ftrace_function(&trace_stack_ops);
201 	else
202 		unregister_ftrace_function(&trace_ops);
203 }
204 
205 static int func_set_flag(u32 old_flags, u32 bit, int set)
206 {
207 	if (bit == TRACE_FUNC_OPT_STACK) {
208 		/* do nothing if already set */
209 		if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
210 			return 0;
211 
212 		if (set) {
213 			unregister_ftrace_function(&trace_ops);
214 			register_ftrace_function(&trace_stack_ops);
215 		} else {
216 			unregister_ftrace_function(&trace_stack_ops);
217 			register_ftrace_function(&trace_ops);
218 		}
219 
220 		return 0;
221 	}
222 
223 	return -EINVAL;
224 }
225 
226 static struct tracer function_trace __read_mostly =
227 {
228 	.name		= "function",
229 	.init		= function_trace_init,
230 	.reset		= function_trace_reset,
231 	.start		= function_trace_start,
232 	.wait_pipe	= poll_wait_pipe,
233 	.flags		= &func_flags,
234 	.set_flag	= func_set_flag,
235 #ifdef CONFIG_FTRACE_SELFTEST
236 	.selftest	= trace_selftest_startup_function,
237 #endif
238 };
239 
240 #ifdef CONFIG_DYNAMIC_FTRACE
241 static void
242 ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
243 {
244 	long *count = (long *)data;
245 
246 	if (tracing_is_on())
247 		return;
248 
249 	if (!*count)
250 		return;
251 
252 	if (*count != -1)
253 		(*count)--;
254 
255 	tracing_on();
256 }
257 
258 static void
259 ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
260 {
261 	long *count = (long *)data;
262 
263 	if (!tracing_is_on())
264 		return;
265 
266 	if (!*count)
267 		return;
268 
269 	if (*count != -1)
270 		(*count)--;
271 
272 	tracing_off();
273 }
274 
275 static int
276 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
277 			 struct ftrace_probe_ops *ops, void *data);
278 
279 static struct ftrace_probe_ops traceon_probe_ops = {
280 	.func			= ftrace_traceon,
281 	.print			= ftrace_trace_onoff_print,
282 };
283 
284 static struct ftrace_probe_ops traceoff_probe_ops = {
285 	.func			= ftrace_traceoff,
286 	.print			= ftrace_trace_onoff_print,
287 };
288 
289 static int
290 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
291 			 struct ftrace_probe_ops *ops, void *data)
292 {
293 	long count = (long)data;
294 
295 	seq_printf(m, "%ps:", (void *)ip);
296 
297 	if (ops == &traceon_probe_ops)
298 		seq_printf(m, "traceon");
299 	else
300 		seq_printf(m, "traceoff");
301 
302 	if (count == -1)
303 		seq_printf(m, ":unlimited\n");
304 	else
305 		seq_printf(m, ":count=%ld\n", count);
306 
307 	return 0;
308 }
309 
310 static int
311 ftrace_trace_onoff_unreg(char *glob, char *cmd, char *param)
312 {
313 	struct ftrace_probe_ops *ops;
314 
315 	/* we register both traceon and traceoff to this callback */
316 	if (strcmp(cmd, "traceon") == 0)
317 		ops = &traceon_probe_ops;
318 	else
319 		ops = &traceoff_probe_ops;
320 
321 	unregister_ftrace_function_probe_func(glob, ops);
322 
323 	return 0;
324 }
325 
326 static int
327 ftrace_trace_onoff_callback(char *glob, char *cmd, char *param, int enable)
328 {
329 	struct ftrace_probe_ops *ops;
330 	void *count = (void *)-1;
331 	char *number;
332 	int ret;
333 
334 	/* hash funcs only work with set_ftrace_filter */
335 	if (!enable)
336 		return -EINVAL;
337 
338 	if (glob[0] == '!')
339 		return ftrace_trace_onoff_unreg(glob+1, cmd, param);
340 
341 	/* we register both traceon and traceoff to this callback */
342 	if (strcmp(cmd, "traceon") == 0)
343 		ops = &traceon_probe_ops;
344 	else
345 		ops = &traceoff_probe_ops;
346 
347 	if (!param)
348 		goto out_reg;
349 
350 	number = strsep(&param, ":");
351 
352 	if (!strlen(number))
353 		goto out_reg;
354 
355 	/*
356 	 * We use the callback data field (which is a pointer)
357 	 * as our counter.
358 	 */
359 	ret = strict_strtoul(number, 0, (unsigned long *)&count);
360 	if (ret)
361 		return ret;
362 
363  out_reg:
364 	ret = register_ftrace_function_probe(glob, ops, count);
365 
366 	return ret < 0 ? ret : 0;
367 }
368 
369 static struct ftrace_func_command ftrace_traceon_cmd = {
370 	.name			= "traceon",
371 	.func			= ftrace_trace_onoff_callback,
372 };
373 
374 static struct ftrace_func_command ftrace_traceoff_cmd = {
375 	.name			= "traceoff",
376 	.func			= ftrace_trace_onoff_callback,
377 };
378 
379 static int __init init_func_cmd_traceon(void)
380 {
381 	int ret;
382 
383 	ret = register_ftrace_command(&ftrace_traceoff_cmd);
384 	if (ret)
385 		return ret;
386 
387 	ret = register_ftrace_command(&ftrace_traceon_cmd);
388 	if (ret)
389 		unregister_ftrace_command(&ftrace_traceoff_cmd);
390 	return ret;
391 }
392 #else
393 static inline int init_func_cmd_traceon(void)
394 {
395 	return 0;
396 }
397 #endif /* CONFIG_DYNAMIC_FTRACE */
398 
399 static __init int init_function_trace(void)
400 {
401 	init_func_cmd_traceon();
402 	return register_tracer(&function_trace);
403 }
404 device_initcall(init_function_trace);
405 
406