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Linux/kernel/trace/trace_event_perf.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * trace event based perf event profiling/tracing
  4  *
  5  * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra
  6  * Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com>
  7  */
  8 
  9 #include <linux/module.h>
 10 #include <linux/kprobes.h>
 11 #include <linux/security.h>
 12 #include "trace.h"
 13 #include "trace_probe.h"
 14 
 15 static char __percpu *perf_trace_buf[PERF_NR_CONTEXTS];
 16 
 17 /*
 18  * Force it to be aligned to unsigned long to avoid misaligned accesses
 19  * surprises
 20  */
 21 typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
 22         perf_trace_t;
 23 
 24 /* Count the events in use (per event id, not per instance) */
 25 static int      total_ref_count;
 26 
 27 static int perf_trace_event_perm(struct trace_event_call *tp_event,
 28                                  struct perf_event *p_event)
 29 {
 30         int ret;
 31 
 32         if (tp_event->perf_perm) {
 33                 ret = tp_event->perf_perm(tp_event, p_event);
 34                 if (ret)
 35                         return ret;
 36         }
 37 
 38         /*
 39          * We checked and allowed to create parent,
 40          * allow children without checking.
 41          */
 42         if (p_event->parent)
 43                 return 0;
 44 
 45         /*
 46          * It's ok to check current process (owner) permissions in here,
 47          * because code below is called only via perf_event_open syscall.
 48          */
 49 
 50         /* The ftrace function trace is allowed only for root. */
 51         if (ftrace_event_is_function(tp_event)) {
 52                 ret = perf_allow_tracepoint(&p_event->attr);
 53                 if (ret)
 54                         return ret;
 55 
 56                 if (!is_sampling_event(p_event))
 57                         return 0;
 58 
 59                 /*
 60                  * We don't allow user space callchains for  function trace
 61                  * event, due to issues with page faults while tracing page
 62                  * fault handler and its overall trickiness nature.
 63                  */
 64                 if (!p_event->attr.exclude_callchain_user)
 65                         return -EINVAL;
 66 
 67                 /*
 68                  * Same reason to disable user stack dump as for user space
 69                  * callchains above.
 70                  */
 71                 if (p_event->attr.sample_type & PERF_SAMPLE_STACK_USER)
 72                         return -EINVAL;
 73         }
 74 
 75         /* No tracing, just counting, so no obvious leak */
 76         if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW))
 77                 return 0;
 78 
 79         /* Some events are ok to be traced by non-root users... */
 80         if (p_event->attach_state == PERF_ATTACH_TASK) {
 81                 if (tp_event->flags & TRACE_EVENT_FL_CAP_ANY)
 82                         return 0;
 83         }
 84 
 85         /*
 86          * ...otherwise raw tracepoint data can be a severe data leak,
 87          * only allow root to have these.
 88          */
 89         ret = perf_allow_tracepoint(&p_event->attr);
 90         if (ret)
 91                 return ret;
 92 
 93         return 0;
 94 }
 95 
 96 static int perf_trace_event_reg(struct trace_event_call *tp_event,
 97                                 struct perf_event *p_event)
 98 {
 99         struct hlist_head __percpu *list;
100         int ret = -ENOMEM;
101         int cpu;
102 
103         p_event->tp_event = tp_event;
104         if (tp_event->perf_refcount++ > 0)
105                 return 0;
106 
107         list = alloc_percpu(struct hlist_head);
108         if (!list)
109                 goto fail;
110 
111         for_each_possible_cpu(cpu)
112                 INIT_HLIST_HEAD(per_cpu_ptr(list, cpu));
113 
114         tp_event->perf_events = list;
115 
116         if (!total_ref_count) {
117                 char __percpu *buf;
118                 int i;
119 
120                 for (i = 0; i < PERF_NR_CONTEXTS; i++) {
121                         buf = (char __percpu *)alloc_percpu(perf_trace_t);
122                         if (!buf)
123                                 goto fail;
124 
125                         perf_trace_buf[i] = buf;
126                 }
127         }
128 
129         ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER, NULL);
130         if (ret)
131                 goto fail;
132 
133         total_ref_count++;
134         return 0;
135 
136 fail:
137         if (!total_ref_count) {
138                 int i;
139 
140                 for (i = 0; i < PERF_NR_CONTEXTS; i++) {
141                         free_percpu(perf_trace_buf[i]);
142                         perf_trace_buf[i] = NULL;
143                 }
144         }
145 
146         if (!--tp_event->perf_refcount) {
147                 free_percpu(tp_event->perf_events);
148                 tp_event->perf_events = NULL;
149         }
150 
151         return ret;
152 }
153 
154 static void perf_trace_event_unreg(struct perf_event *p_event)
155 {
156         struct trace_event_call *tp_event = p_event->tp_event;
157         int i;
158 
159         if (--tp_event->perf_refcount > 0)
160                 goto out;
161 
162         tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER, NULL);
163 
164         /*
165          * Ensure our callback won't be called anymore. The buffers
166          * will be freed after that.
167          */
168         tracepoint_synchronize_unregister();
169 
170         free_percpu(tp_event->perf_events);
171         tp_event->perf_events = NULL;
172 
173         if (!--total_ref_count) {
174                 for (i = 0; i < PERF_NR_CONTEXTS; i++) {
175                         free_percpu(perf_trace_buf[i]);
176                         perf_trace_buf[i] = NULL;
177                 }
178         }
179 out:
180         module_put(tp_event->mod);
181 }
182 
183 static int perf_trace_event_open(struct perf_event *p_event)
184 {
185         struct trace_event_call *tp_event = p_event->tp_event;
186         return tp_event->class->reg(tp_event, TRACE_REG_PERF_OPEN, p_event);
187 }
188 
189 static void perf_trace_event_close(struct perf_event *p_event)
190 {
191         struct trace_event_call *tp_event = p_event->tp_event;
192         tp_event->class->reg(tp_event, TRACE_REG_PERF_CLOSE, p_event);
193 }
194 
195 static int perf_trace_event_init(struct trace_event_call *tp_event,
196                                  struct perf_event *p_event)
197 {
198         int ret;
199 
200         ret = perf_trace_event_perm(tp_event, p_event);
201         if (ret)
202                 return ret;
203 
204         ret = perf_trace_event_reg(tp_event, p_event);
205         if (ret)
206                 return ret;
207 
208         ret = perf_trace_event_open(p_event);
209         if (ret) {
210                 perf_trace_event_unreg(p_event);
211                 return ret;
212         }
213 
214         return 0;
215 }
216 
217 int perf_trace_init(struct perf_event *p_event)
218 {
219         struct trace_event_call *tp_event;
220         u64 event_id = p_event->attr.config;
221         int ret = -EINVAL;
222 
223         mutex_lock(&event_mutex);
224         list_for_each_entry(tp_event, &ftrace_events, list) {
225                 if (tp_event->event.type == event_id &&
226                     tp_event->class && tp_event->class->reg &&
227                     try_module_get(tp_event->mod)) {
228                         ret = perf_trace_event_init(tp_event, p_event);
229                         if (ret)
230                                 module_put(tp_event->mod);
231                         break;
232                 }
233         }
234         mutex_unlock(&event_mutex);
235 
236         return ret;
237 }
238 
239 void perf_trace_destroy(struct perf_event *p_event)
240 {
241         mutex_lock(&event_mutex);
242         perf_trace_event_close(p_event);
243         perf_trace_event_unreg(p_event);
244         mutex_unlock(&event_mutex);
245 }
246 
247 #ifdef CONFIG_KPROBE_EVENTS
248 int perf_kprobe_init(struct perf_event *p_event, bool is_retprobe)
249 {
250         int ret;
251         char *func = NULL;
252         struct trace_event_call *tp_event;
253 
254         if (p_event->attr.kprobe_func) {
255                 func = kzalloc(KSYM_NAME_LEN, GFP_KERNEL);
256                 if (!func)
257                         return -ENOMEM;
258                 ret = strncpy_from_user(
259                         func, u64_to_user_ptr(p_event->attr.kprobe_func),
260                         KSYM_NAME_LEN);
261                 if (ret == KSYM_NAME_LEN)
262                         ret = -E2BIG;
263                 if (ret < 0)
264                         goto out;
265 
266                 if (func[0] == '\0') {
267                         kfree(func);
268                         func = NULL;
269                 }
270         }
271 
272         tp_event = create_local_trace_kprobe(
273                 func, (void *)(unsigned long)(p_event->attr.kprobe_addr),
274                 p_event->attr.probe_offset, is_retprobe);
275         if (IS_ERR(tp_event)) {
276                 ret = PTR_ERR(tp_event);
277                 goto out;
278         }
279 
280         mutex_lock(&event_mutex);
281         ret = perf_trace_event_init(tp_event, p_event);
282         if (ret)
283                 destroy_local_trace_kprobe(tp_event);
284         mutex_unlock(&event_mutex);
285 out:
286         kfree(func);
287         return ret;
288 }
289 
290 void perf_kprobe_destroy(struct perf_event *p_event)
291 {
292         mutex_lock(&event_mutex);
293         perf_trace_event_close(p_event);
294         perf_trace_event_unreg(p_event);
295         mutex_unlock(&event_mutex);
296 
297         destroy_local_trace_kprobe(p_event->tp_event);
298 }
299 #endif /* CONFIG_KPROBE_EVENTS */
300 
301 #ifdef CONFIG_UPROBE_EVENTS
302 int perf_uprobe_init(struct perf_event *p_event,
303                      unsigned long ref_ctr_offset, bool is_retprobe)
304 {
305         int ret;
306         char *path = NULL;
307         struct trace_event_call *tp_event;
308 
309         if (!p_event->attr.uprobe_path)
310                 return -EINVAL;
311 
312         path = strndup_user(u64_to_user_ptr(p_event->attr.uprobe_path),
313                             PATH_MAX);
314         if (IS_ERR(path)) {
315                 ret = PTR_ERR(path);
316                 return (ret == -EINVAL) ? -E2BIG : ret;
317         }
318         if (path[0] == '\0') {
319                 ret = -EINVAL;
320                 goto out;
321         }
322 
323         tp_event = create_local_trace_uprobe(path, p_event->attr.probe_offset,
324                                              ref_ctr_offset, is_retprobe);
325         if (IS_ERR(tp_event)) {
326                 ret = PTR_ERR(tp_event);
327                 goto out;
328         }
329 
330         /*
331          * local trace_uprobe need to hold event_mutex to call
332          * uprobe_buffer_enable() and uprobe_buffer_disable().
333          * event_mutex is not required for local trace_kprobes.
334          */
335         mutex_lock(&event_mutex);
336         ret = perf_trace_event_init(tp_event, p_event);
337         if (ret)
338                 destroy_local_trace_uprobe(tp_event);
339         mutex_unlock(&event_mutex);
340 out:
341         kfree(path);
342         return ret;
343 }
344 
345 void perf_uprobe_destroy(struct perf_event *p_event)
346 {
347         mutex_lock(&event_mutex);
348         perf_trace_event_close(p_event);
349         perf_trace_event_unreg(p_event);
350         mutex_unlock(&event_mutex);
351         destroy_local_trace_uprobe(p_event->tp_event);
352 }
353 #endif /* CONFIG_UPROBE_EVENTS */
354 
355 int perf_trace_add(struct perf_event *p_event, int flags)
356 {
357         struct trace_event_call *tp_event = p_event->tp_event;
358 
359         if (!(flags & PERF_EF_START))
360                 p_event->hw.state = PERF_HES_STOPPED;
361 
362         /*
363          * If TRACE_REG_PERF_ADD returns false; no custom action was performed
364          * and we need to take the default action of enqueueing our event on
365          * the right per-cpu hlist.
366          */
367         if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event)) {
368                 struct hlist_head __percpu *pcpu_list;
369                 struct hlist_head *list;
370 
371                 pcpu_list = tp_event->perf_events;
372                 if (WARN_ON_ONCE(!pcpu_list))
373                         return -EINVAL;
374 
375                 list = this_cpu_ptr(pcpu_list);
376                 hlist_add_head_rcu(&p_event->hlist_entry, list);
377         }
378 
379         return 0;
380 }
381 
382 void perf_trace_del(struct perf_event *p_event, int flags)
383 {
384         struct trace_event_call *tp_event = p_event->tp_event;
385 
386         /*
387          * If TRACE_REG_PERF_DEL returns false; no custom action was performed
388          * and we need to take the default action of dequeueing our event from
389          * the right per-cpu hlist.
390          */
391         if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event))
392                 hlist_del_rcu(&p_event->hlist_entry);
393 }
394 
395 void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp)
396 {
397         char *raw_data;
398         int rctx;
399 
400         BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
401 
402         if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
403                       "perf buffer not large enough"))
404                 return NULL;
405 
406         *rctxp = rctx = perf_swevent_get_recursion_context();
407         if (rctx < 0)
408                 return NULL;
409 
410         if (regs)
411                 *regs = this_cpu_ptr(&__perf_regs[rctx]);
412         raw_data = this_cpu_ptr(perf_trace_buf[rctx]);
413 
414         /* zero the dead bytes from align to not leak stack to user */
415         memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
416         return raw_data;
417 }
418 EXPORT_SYMBOL_GPL(perf_trace_buf_alloc);
419 NOKPROBE_SYMBOL(perf_trace_buf_alloc);
420 
421 void perf_trace_buf_update(void *record, u16 type)
422 {
423         struct trace_entry *entry = record;
424 
425         tracing_generic_entry_update(entry, type, tracing_gen_ctx());
426 }
427 NOKPROBE_SYMBOL(perf_trace_buf_update);
428 
429 #ifdef CONFIG_FUNCTION_TRACER
430 static void
431 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
432                           struct ftrace_ops *ops,  struct ftrace_regs *fregs)
433 {
434         struct ftrace_entry *entry;
435         struct perf_event *event;
436         struct hlist_head head;
437         struct pt_regs regs;
438         int rctx;
439         int bit;
440 
441         if (!rcu_is_watching())
442                 return;
443 
444         bit = ftrace_test_recursion_trylock(ip, parent_ip);
445         if (bit < 0)
446                 return;
447 
448         if ((unsigned long)ops->private != smp_processor_id())
449                 goto out;
450 
451         event = container_of(ops, struct perf_event, ftrace_ops);
452 
453         /*
454          * @event->hlist entry is NULL (per INIT_HLIST_NODE), and all
455          * the perf code does is hlist_for_each_entry_rcu(), so we can
456          * get away with simply setting the @head.first pointer in order
457          * to create a singular list.
458          */
459         head.first = &event->hlist_entry;
460 
461 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \
462                     sizeof(u64)) - sizeof(u32))
463 
464         BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE);
465 
466         memset(&regs, 0, sizeof(regs));
467         perf_fetch_caller_regs(&regs);
468 
469         entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx);
470         if (!entry)
471                 goto out;
472 
473         entry->ip = ip;
474         entry->parent_ip = parent_ip;
475         perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN,
476                               1, &regs, &head, NULL);
477 
478 out:
479         ftrace_test_recursion_unlock(bit);
480 #undef ENTRY_SIZE
481 }
482 
483 static int perf_ftrace_function_register(struct perf_event *event)
484 {
485         struct ftrace_ops *ops = &event->ftrace_ops;
486 
487         ops->func    = perf_ftrace_function_call;
488         ops->private = (void *)(unsigned long)nr_cpu_ids;
489 
490         return register_ftrace_function(ops);
491 }
492 
493 static int perf_ftrace_function_unregister(struct perf_event *event)
494 {
495         struct ftrace_ops *ops = &event->ftrace_ops;
496         int ret = unregister_ftrace_function(ops);
497         ftrace_free_filter(ops);
498         return ret;
499 }
500 
501 int perf_ftrace_event_register(struct trace_event_call *call,
502                                enum trace_reg type, void *data)
503 {
504         struct perf_event *event = data;
505 
506         switch (type) {
507         case TRACE_REG_REGISTER:
508         case TRACE_REG_UNREGISTER:
509                 break;
510         case TRACE_REG_PERF_REGISTER:
511         case TRACE_REG_PERF_UNREGISTER:
512                 return 0;
513         case TRACE_REG_PERF_OPEN:
514                 return perf_ftrace_function_register(data);
515         case TRACE_REG_PERF_CLOSE:
516                 return perf_ftrace_function_unregister(data);
517         case TRACE_REG_PERF_ADD:
518                 event->ftrace_ops.private = (void *)(unsigned long)smp_processor_id();
519                 return 1;
520         case TRACE_REG_PERF_DEL:
521                 event->ftrace_ops.private = (void *)(unsigned long)nr_cpu_ids;
522                 return 1;
523         }
524 
525         return -EINVAL;
526 }
527 #endif /* CONFIG_FUNCTION_TRACER */
528 

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