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->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 /* 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 = tr->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 = tr->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 void
218 ftrace_traceon(unsigned long ip, unsigned long parent_ip, void **data)
219 {
220 	long *count = (long *)data;
221 
222 	if (tracing_is_on())
223 		return;
224 
225 	if (!*count)
226 		return;
227 
228 	if (*count != -1)
229 		(*count)--;
230 
231 	tracing_on();
232 }
233 
234 static void
235 ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data)
236 {
237 	long *count = (long *)data;
238 
239 	if (!tracing_is_on())
240 		return;
241 
242 	if (!*count)
243 		return;
244 
245 	if (*count != -1)
246 		(*count)--;
247 
248 	tracing_off();
249 }
250 
251 static int
252 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
253 			 struct ftrace_probe_ops *ops, void *data);
254 
255 static struct ftrace_probe_ops traceon_probe_ops = {
256 	.func			= ftrace_traceon,
257 	.print			= ftrace_trace_onoff_print,
258 };
259 
260 static struct ftrace_probe_ops traceoff_probe_ops = {
261 	.func			= ftrace_traceoff,
262 	.print			= ftrace_trace_onoff_print,
263 };
264 
265 static int
266 ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,
267 			 struct ftrace_probe_ops *ops, void *data)
268 {
269 	long count = (long)data;
270 
271 	seq_printf(m, "%ps:", (void *)ip);
272 
273 	if (ops == &traceon_probe_ops)
274 		seq_printf(m, "traceon");
275 	else
276 		seq_printf(m, "traceoff");
277 
278 	if (count == -1)
279 		seq_printf(m, ":unlimited\n");
280 	else
281 		seq_printf(m, ":count=%ld\n", count);
282 
283 	return 0;
284 }
285 
286 static int
287 ftrace_trace_onoff_unreg(char *glob, char *cmd, char *param)
288 {
289 	struct ftrace_probe_ops *ops;
290 
291 	/* we register both traceon and traceoff to this callback */
292 	if (strcmp(cmd, "traceon") == 0)
293 		ops = &traceon_probe_ops;
294 	else
295 		ops = &traceoff_probe_ops;
296 
297 	unregister_ftrace_function_probe_func(glob, ops);
298 
299 	return 0;
300 }
301 
302 static int
303 ftrace_trace_onoff_callback(struct ftrace_hash *hash,
304 			    char *glob, char *cmd, char *param, int enable)
305 {
306 	struct ftrace_probe_ops *ops;
307 	void *count = (void *)-1;
308 	char *number;
309 	int ret;
310 
311 	/* hash funcs only work with set_ftrace_filter */
312 	if (!enable)
313 		return -EINVAL;
314 
315 	if (glob[0] == '!')
316 		return ftrace_trace_onoff_unreg(glob+1, cmd, param);
317 
318 	/* we register both traceon and traceoff to this callback */
319 	if (strcmp(cmd, "traceon") == 0)
320 		ops = &traceon_probe_ops;
321 	else
322 		ops = &traceoff_probe_ops;
323 
324 	if (!param)
325 		goto out_reg;
326 
327 	number = strsep(&param, ":");
328 
329 	if (!strlen(number))
330 		goto out_reg;
331 
332 	/*
333 	 * We use the callback data field (which is a pointer)
334 	 * as our counter.
335 	 */
336 	ret = kstrtoul(number, 0, (unsigned long *)&count);
337 	if (ret)
338 		return ret;
339 
340  out_reg:
341 	ret = register_ftrace_function_probe(glob, ops, count);
342 
343 	return ret < 0 ? ret : 0;
344 }
345 
346 static struct ftrace_func_command ftrace_traceon_cmd = {
347 	.name			= "traceon",
348 	.func			= ftrace_trace_onoff_callback,
349 };
350 
351 static struct ftrace_func_command ftrace_traceoff_cmd = {
352 	.name			= "traceoff",
353 	.func			= ftrace_trace_onoff_callback,
354 };
355 
356 static int __init init_func_cmd_traceon(void)
357 {
358 	int ret;
359 
360 	ret = register_ftrace_command(&ftrace_traceoff_cmd);
361 	if (ret)
362 		return ret;
363 
364 	ret = register_ftrace_command(&ftrace_traceon_cmd);
365 	if (ret)
366 		unregister_ftrace_command(&ftrace_traceoff_cmd);
367 	return ret;
368 }
369 #else
370 static inline int init_func_cmd_traceon(void)
371 {
372 	return 0;
373 }
374 #endif /* CONFIG_DYNAMIC_FTRACE */
375 
376 static __init int init_function_trace(void)
377 {
378 	init_func_cmd_traceon();
379 	return register_tracer(&function_trace);
380 }
381 core_initcall(init_function_trace);
382