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

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