1 /*
2  * trace event based perf event profiling/tracing
3  *
4  * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra
5  * Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com>
6  */
7 
8 #include <linux/module.h>
9 #include <linux/kprobes.h>
10 #include "trace.h"
11 #include "trace_probe.h"
12 
13 static char __percpu *perf_trace_buf[PERF_NR_CONTEXTS];
14 
15 /*
16  * Force it to be aligned to unsigned long to avoid misaligned accesses
17  * suprises
18  */
19 typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
20 	perf_trace_t;
21 
22 /* Count the events in use (per event id, not per instance) */
23 static int	total_ref_count;
24 
25 static int perf_trace_event_perm(struct trace_event_call *tp_event,
26 				 struct perf_event *p_event)
27 {
28 	if (tp_event->perf_perm) {
29 		int ret = tp_event->perf_perm(tp_event, p_event);
30 		if (ret)
31 			return ret;
32 	}
33 
34 	/*
35 	 * We checked and allowed to create parent,
36 	 * allow children without checking.
37 	 */
38 	if (p_event->parent)
39 		return 0;
40 
41 	/*
42 	 * It's ok to check current process (owner) permissions in here,
43 	 * because code below is called only via perf_event_open syscall.
44 	 */
45 
46 	/* The ftrace function trace is allowed only for root. */
47 	if (ftrace_event_is_function(tp_event)) {
48 		if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
49 			return -EPERM;
50 
51 		if (!is_sampling_event(p_event))
52 			return 0;
53 
54 		/*
55 		 * We don't allow user space callchains for  function trace
56 		 * event, due to issues with page faults while tracing page
57 		 * fault handler and its overall trickiness nature.
58 		 */
59 		if (!p_event->attr.exclude_callchain_user)
60 			return -EINVAL;
61 
62 		/*
63 		 * Same reason to disable user stack dump as for user space
64 		 * callchains above.
65 		 */
66 		if (p_event->attr.sample_type & PERF_SAMPLE_STACK_USER)
67 			return -EINVAL;
68 	}
69 
70 	/* No tracing, just counting, so no obvious leak */
71 	if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW))
72 		return 0;
73 
74 	/* Some events are ok to be traced by non-root users... */
75 	if (p_event->attach_state == PERF_ATTACH_TASK) {
76 		if (tp_event->flags & TRACE_EVENT_FL_CAP_ANY)
77 			return 0;
78 	}
79 
80 	/*
81 	 * ...otherwise raw tracepoint data can be a severe data leak,
82 	 * only allow root to have these.
83 	 */
84 	if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
85 		return -EPERM;
86 
87 	return 0;
88 }
89 
90 static int perf_trace_event_reg(struct trace_event_call *tp_event,
91 				struct perf_event *p_event)
92 {
93 	struct hlist_head __percpu *list;
94 	int ret = -ENOMEM;
95 	int cpu;
96 
97 	p_event->tp_event = tp_event;
98 	if (tp_event->perf_refcount++ > 0)
99 		return 0;
100 
101 	list = alloc_percpu(struct hlist_head);
102 	if (!list)
103 		goto fail;
104 
105 	for_each_possible_cpu(cpu)
106 		INIT_HLIST_HEAD(per_cpu_ptr(list, cpu));
107 
108 	tp_event->perf_events = list;
109 
110 	if (!total_ref_count) {
111 		char __percpu *buf;
112 		int i;
113 
114 		for (i = 0; i < PERF_NR_CONTEXTS; i++) {
115 			buf = (char __percpu *)alloc_percpu(perf_trace_t);
116 			if (!buf)
117 				goto fail;
118 
119 			perf_trace_buf[i] = buf;
120 		}
121 	}
122 
123 	ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER, NULL);
124 	if (ret)
125 		goto fail;
126 
127 	total_ref_count++;
128 	return 0;
129 
130 fail:
131 	if (!total_ref_count) {
132 		int i;
133 
134 		for (i = 0; i < PERF_NR_CONTEXTS; i++) {
135 			free_percpu(perf_trace_buf[i]);
136 			perf_trace_buf[i] = NULL;
137 		}
138 	}
139 
140 	if (!--tp_event->perf_refcount) {
141 		free_percpu(tp_event->perf_events);
142 		tp_event->perf_events = NULL;
143 	}
144 
145 	return ret;
146 }
147 
148 static void perf_trace_event_unreg(struct perf_event *p_event)
149 {
150 	struct trace_event_call *tp_event = p_event->tp_event;
151 	int i;
152 
153 	if (--tp_event->perf_refcount > 0)
154 		goto out;
155 
156 	tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER, NULL);
157 
158 	/*
159 	 * Ensure our callback won't be called anymore. The buffers
160 	 * will be freed after that.
161 	 */
162 	tracepoint_synchronize_unregister();
163 
164 	free_percpu(tp_event->perf_events);
165 	tp_event->perf_events = NULL;
166 
167 	if (!--total_ref_count) {
168 		for (i = 0; i < PERF_NR_CONTEXTS; i++) {
169 			free_percpu(perf_trace_buf[i]);
170 			perf_trace_buf[i] = NULL;
171 		}
172 	}
173 out:
174 	module_put(tp_event->mod);
175 }
176 
177 static int perf_trace_event_open(struct perf_event *p_event)
178 {
179 	struct trace_event_call *tp_event = p_event->tp_event;
180 	return tp_event->class->reg(tp_event, TRACE_REG_PERF_OPEN, p_event);
181 }
182 
183 static void perf_trace_event_close(struct perf_event *p_event)
184 {
185 	struct trace_event_call *tp_event = p_event->tp_event;
186 	tp_event->class->reg(tp_event, TRACE_REG_PERF_CLOSE, p_event);
187 }
188 
189 static int perf_trace_event_init(struct trace_event_call *tp_event,
190 				 struct perf_event *p_event)
191 {
192 	int ret;
193 
194 	ret = perf_trace_event_perm(tp_event, p_event);
195 	if (ret)
196 		return ret;
197 
198 	ret = perf_trace_event_reg(tp_event, p_event);
199 	if (ret)
200 		return ret;
201 
202 	ret = perf_trace_event_open(p_event);
203 	if (ret) {
204 		perf_trace_event_unreg(p_event);
205 		return ret;
206 	}
207 
208 	return 0;
209 }
210 
211 int perf_trace_init(struct perf_event *p_event)
212 {
213 	struct trace_event_call *tp_event;
214 	u64 event_id = p_event->attr.config;
215 	int ret = -EINVAL;
216 
217 	mutex_lock(&event_mutex);
218 	list_for_each_entry(tp_event, &ftrace_events, list) {
219 		if (tp_event->event.type == event_id &&
220 		    tp_event->class && tp_event->class->reg &&
221 		    try_module_get(tp_event->mod)) {
222 			ret = perf_trace_event_init(tp_event, p_event);
223 			if (ret)
224 				module_put(tp_event->mod);
225 			break;
226 		}
227 	}
228 	mutex_unlock(&event_mutex);
229 
230 	return ret;
231 }
232 
233 void perf_trace_destroy(struct perf_event *p_event)
234 {
235 	mutex_lock(&event_mutex);
236 	perf_trace_event_close(p_event);
237 	perf_trace_event_unreg(p_event);
238 	mutex_unlock(&event_mutex);
239 }
240 
241 #ifdef CONFIG_KPROBE_EVENTS
242 int perf_kprobe_init(struct perf_event *p_event, bool is_retprobe)
243 {
244 	int ret;
245 	char *func = NULL;
246 	struct trace_event_call *tp_event;
247 
248 	if (p_event->attr.kprobe_func) {
249 		func = kzalloc(KSYM_NAME_LEN, GFP_KERNEL);
250 		if (!func)
251 			return -ENOMEM;
252 		ret = strncpy_from_user(
253 			func, u64_to_user_ptr(p_event->attr.kprobe_func),
254 			KSYM_NAME_LEN);
255 		if (ret == KSYM_NAME_LEN)
256 			ret = -E2BIG;
257 		if (ret < 0)
258 			goto out;
259 
260 		if (func[0] == '\0') {
261 			kfree(func);
262 			func = NULL;
263 		}
264 	}
265 
266 	tp_event = create_local_trace_kprobe(
267 		func, (void *)(unsigned long)(p_event->attr.kprobe_addr),
268 		p_event->attr.probe_offset, is_retprobe);
269 	if (IS_ERR(tp_event)) {
270 		ret = PTR_ERR(tp_event);
271 		goto out;
272 	}
273 
274 	ret = perf_trace_event_init(tp_event, p_event);
275 	if (ret)
276 		destroy_local_trace_kprobe(tp_event);
277 out:
278 	kfree(func);
279 	return ret;
280 }
281 
282 void perf_kprobe_destroy(struct perf_event *p_event)
283 {
284 	perf_trace_event_close(p_event);
285 	perf_trace_event_unreg(p_event);
286 
287 	destroy_local_trace_kprobe(p_event->tp_event);
288 }
289 #endif /* CONFIG_KPROBE_EVENTS */
290 
291 #ifdef CONFIG_UPROBE_EVENTS
292 int perf_uprobe_init(struct perf_event *p_event, bool is_retprobe)
293 {
294 	int ret;
295 	char *path = NULL;
296 	struct trace_event_call *tp_event;
297 
298 	if (!p_event->attr.uprobe_path)
299 		return -EINVAL;
300 	path = kzalloc(PATH_MAX, GFP_KERNEL);
301 	if (!path)
302 		return -ENOMEM;
303 	ret = strncpy_from_user(
304 		path, u64_to_user_ptr(p_event->attr.uprobe_path), PATH_MAX);
305 	if (ret == PATH_MAX)
306 		return -E2BIG;
307 	if (ret < 0)
308 		goto out;
309 	if (path[0] == '\0') {
310 		ret = -EINVAL;
311 		goto out;
312 	}
313 
314 	tp_event = create_local_trace_uprobe(
315 		path, p_event->attr.probe_offset, is_retprobe);
316 	if (IS_ERR(tp_event)) {
317 		ret = PTR_ERR(tp_event);
318 		goto out;
319 	}
320 
321 	/*
322 	 * local trace_uprobe need to hold event_mutex to call
323 	 * uprobe_buffer_enable() and uprobe_buffer_disable().
324 	 * event_mutex is not required for local trace_kprobes.
325 	 */
326 	mutex_lock(&event_mutex);
327 	ret = perf_trace_event_init(tp_event, p_event);
328 	if (ret)
329 		destroy_local_trace_uprobe(tp_event);
330 	mutex_unlock(&event_mutex);
331 out:
332 	kfree(path);
333 	return ret;
334 }
335 
336 void perf_uprobe_destroy(struct perf_event *p_event)
337 {
338 	mutex_lock(&event_mutex);
339 	perf_trace_event_close(p_event);
340 	perf_trace_event_unreg(p_event);
341 	mutex_unlock(&event_mutex);
342 	destroy_local_trace_uprobe(p_event->tp_event);
343 }
344 #endif /* CONFIG_UPROBE_EVENTS */
345 
346 int perf_trace_add(struct perf_event *p_event, int flags)
347 {
348 	struct trace_event_call *tp_event = p_event->tp_event;
349 
350 	if (!(flags & PERF_EF_START))
351 		p_event->hw.state = PERF_HES_STOPPED;
352 
353 	/*
354 	 * If TRACE_REG_PERF_ADD returns false; no custom action was performed
355 	 * and we need to take the default action of enqueueing our event on
356 	 * the right per-cpu hlist.
357 	 */
358 	if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event)) {
359 		struct hlist_head __percpu *pcpu_list;
360 		struct hlist_head *list;
361 
362 		pcpu_list = tp_event->perf_events;
363 		if (WARN_ON_ONCE(!pcpu_list))
364 			return -EINVAL;
365 
366 		list = this_cpu_ptr(pcpu_list);
367 		hlist_add_head_rcu(&p_event->hlist_entry, list);
368 	}
369 
370 	return 0;
371 }
372 
373 void perf_trace_del(struct perf_event *p_event, int flags)
374 {
375 	struct trace_event_call *tp_event = p_event->tp_event;
376 
377 	/*
378 	 * If TRACE_REG_PERF_DEL returns false; no custom action was performed
379 	 * and we need to take the default action of dequeueing our event from
380 	 * the right per-cpu hlist.
381 	 */
382 	if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event))
383 		hlist_del_rcu(&p_event->hlist_entry);
384 }
385 
386 void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp)
387 {
388 	char *raw_data;
389 	int rctx;
390 
391 	BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
392 
393 	if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
394 		      "perf buffer not large enough"))
395 		return NULL;
396 
397 	*rctxp = rctx = perf_swevent_get_recursion_context();
398 	if (rctx < 0)
399 		return NULL;
400 
401 	if (regs)
402 		*regs = this_cpu_ptr(&__perf_regs[rctx]);
403 	raw_data = this_cpu_ptr(perf_trace_buf[rctx]);
404 
405 	/* zero the dead bytes from align to not leak stack to user */
406 	memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
407 	return raw_data;
408 }
409 EXPORT_SYMBOL_GPL(perf_trace_buf_alloc);
410 NOKPROBE_SYMBOL(perf_trace_buf_alloc);
411 
412 void perf_trace_buf_update(void *record, u16 type)
413 {
414 	struct trace_entry *entry = record;
415 	int pc = preempt_count();
416 	unsigned long flags;
417 
418 	local_save_flags(flags);
419 	tracing_generic_entry_update(entry, flags, pc);
420 	entry->type = type;
421 }
422 NOKPROBE_SYMBOL(perf_trace_buf_update);
423 
424 #ifdef CONFIG_FUNCTION_TRACER
425 static void
426 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
427 			  struct ftrace_ops *ops, struct pt_regs *pt_regs)
428 {
429 	struct ftrace_entry *entry;
430 	struct perf_event *event;
431 	struct hlist_head head;
432 	struct pt_regs regs;
433 	int rctx;
434 
435 	if ((unsigned long)ops->private != smp_processor_id())
436 		return;
437 
438 	event = container_of(ops, struct perf_event, ftrace_ops);
439 
440 	/*
441 	 * @event->hlist entry is NULL (per INIT_HLIST_NODE), and all
442 	 * the perf code does is hlist_for_each_entry_rcu(), so we can
443 	 * get away with simply setting the @head.first pointer in order
444 	 * to create a singular list.
445 	 */
446 	head.first = &event->hlist_entry;
447 
448 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \
449 		    sizeof(u64)) - sizeof(u32))
450 
451 	BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE);
452 
453 	memset(&regs, 0, sizeof(regs));
454 	perf_fetch_caller_regs(&regs);
455 
456 	entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx);
457 	if (!entry)
458 		return;
459 
460 	entry->ip = ip;
461 	entry->parent_ip = parent_ip;
462 	perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN,
463 			      1, &regs, &head, NULL);
464 
465 #undef ENTRY_SIZE
466 }
467 
468 static int perf_ftrace_function_register(struct perf_event *event)
469 {
470 	struct ftrace_ops *ops = &event->ftrace_ops;
471 
472 	ops->flags   = FTRACE_OPS_FL_RCU;
473 	ops->func    = perf_ftrace_function_call;
474 	ops->private = (void *)(unsigned long)nr_cpu_ids;
475 
476 	return register_ftrace_function(ops);
477 }
478 
479 static int perf_ftrace_function_unregister(struct perf_event *event)
480 {
481 	struct ftrace_ops *ops = &event->ftrace_ops;
482 	int ret = unregister_ftrace_function(ops);
483 	ftrace_free_filter(ops);
484 	return ret;
485 }
486 
487 int perf_ftrace_event_register(struct trace_event_call *call,
488 			       enum trace_reg type, void *data)
489 {
490 	struct perf_event *event = data;
491 
492 	switch (type) {
493 	case TRACE_REG_REGISTER:
494 	case TRACE_REG_UNREGISTER:
495 		break;
496 	case TRACE_REG_PERF_REGISTER:
497 	case TRACE_REG_PERF_UNREGISTER:
498 		return 0;
499 	case TRACE_REG_PERF_OPEN:
500 		return perf_ftrace_function_register(data);
501 	case TRACE_REG_PERF_CLOSE:
502 		return perf_ftrace_function_unregister(data);
503 	case TRACE_REG_PERF_ADD:
504 		event->ftrace_ops.private = (void *)(unsigned long)smp_processor_id();
505 		return 1;
506 	case TRACE_REG_PERF_DEL:
507 		event->ftrace_ops.private = (void *)(unsigned long)nr_cpu_ids;
508 		return 1;
509 	}
510 
511 	return -EINVAL;
512 }
513 #endif /* CONFIG_FUNCTION_TRACER */
514