uprobes/perf: Avoid perf_trace_buf_prepare/submit if ->perf_events is empty
[linux-3.10.git] / kernel / trace / trace_event_perf.c
1 /*
2  * trace event based perf event profiling/tracing
3  *
4  * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>
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
12 static char __percpu *perf_trace_buf[PERF_NR_CONTEXTS];
13
14 /*
15  * Force it to be aligned to unsigned long to avoid misaligned accesses
16  * suprises
17  */
18 typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
19         perf_trace_t;
20
21 /* Count the events in use (per event id, not per instance) */
22 static int      total_ref_count;
23
24 static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
25                                  struct perf_event *p_event)
26 {
27         /* The ftrace function trace is allowed only for root. */
28         if (ftrace_event_is_function(tp_event) &&
29             perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
30                 return -EPERM;
31
32         /* No tracing, just counting, so no obvious leak */
33         if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW))
34                 return 0;
35
36         /* Some events are ok to be traced by non-root users... */
37         if (p_event->attach_state == PERF_ATTACH_TASK) {
38                 if (tp_event->flags & TRACE_EVENT_FL_CAP_ANY)
39                         return 0;
40         }
41
42         /*
43          * ...otherwise raw tracepoint data can be a severe data leak,
44          * only allow root to have these.
45          */
46         if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
47                 return -EPERM;
48
49         return 0;
50 }
51
52 static int perf_trace_event_reg(struct ftrace_event_call *tp_event,
53                                 struct perf_event *p_event)
54 {
55         struct hlist_head __percpu *list;
56         int ret = -ENOMEM;
57         int cpu;
58
59         p_event->tp_event = tp_event;
60         if (tp_event->perf_refcount++ > 0)
61                 return 0;
62
63         list = alloc_percpu(struct hlist_head);
64         if (!list)
65                 goto fail;
66
67         for_each_possible_cpu(cpu)
68                 INIT_HLIST_HEAD(per_cpu_ptr(list, cpu));
69
70         tp_event->perf_events = list;
71
72         if (!total_ref_count) {
73                 char __percpu *buf;
74                 int i;
75
76                 for (i = 0; i < PERF_NR_CONTEXTS; i++) {
77                         buf = (char __percpu *)alloc_percpu(perf_trace_t);
78                         if (!buf)
79                                 goto fail;
80
81                         perf_trace_buf[i] = buf;
82                 }
83         }
84
85         ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER, NULL);
86         if (ret)
87                 goto fail;
88
89         total_ref_count++;
90         return 0;
91
92 fail:
93         if (!total_ref_count) {
94                 int i;
95
96                 for (i = 0; i < PERF_NR_CONTEXTS; i++) {
97                         free_percpu(perf_trace_buf[i]);
98                         perf_trace_buf[i] = NULL;
99                 }
100         }
101
102         if (!--tp_event->perf_refcount) {
103                 free_percpu(tp_event->perf_events);
104                 tp_event->perf_events = NULL;
105         }
106
107         return ret;
108 }
109
110 static void perf_trace_event_unreg(struct perf_event *p_event)
111 {
112         struct ftrace_event_call *tp_event = p_event->tp_event;
113         int i;
114
115         if (--tp_event->perf_refcount > 0)
116                 goto out;
117
118         tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER, NULL);
119
120         /*
121          * Ensure our callback won't be called anymore. The buffers
122          * will be freed after that.
123          */
124         tracepoint_synchronize_unregister();
125
126         free_percpu(tp_event->perf_events);
127         tp_event->perf_events = NULL;
128
129         if (!--total_ref_count) {
130                 for (i = 0; i < PERF_NR_CONTEXTS; i++) {
131                         free_percpu(perf_trace_buf[i]);
132                         perf_trace_buf[i] = NULL;
133                 }
134         }
135 out:
136         module_put(tp_event->mod);
137 }
138
139 static int perf_trace_event_open(struct perf_event *p_event)
140 {
141         struct ftrace_event_call *tp_event = p_event->tp_event;
142         return tp_event->class->reg(tp_event, TRACE_REG_PERF_OPEN, p_event);
143 }
144
145 static void perf_trace_event_close(struct perf_event *p_event)
146 {
147         struct ftrace_event_call *tp_event = p_event->tp_event;
148         tp_event->class->reg(tp_event, TRACE_REG_PERF_CLOSE, p_event);
149 }
150
151 static int perf_trace_event_init(struct ftrace_event_call *tp_event,
152                                  struct perf_event *p_event)
153 {
154         int ret;
155
156         ret = perf_trace_event_perm(tp_event, p_event);
157         if (ret)
158                 return ret;
159
160         ret = perf_trace_event_reg(tp_event, p_event);
161         if (ret)
162                 return ret;
163
164         ret = perf_trace_event_open(p_event);
165         if (ret) {
166                 perf_trace_event_unreg(p_event);
167                 return ret;
168         }
169
170         return 0;
171 }
172
173 int perf_trace_init(struct perf_event *p_event)
174 {
175         struct ftrace_event_call *tp_event;
176         int event_id = p_event->attr.config;
177         int ret = -EINVAL;
178
179         mutex_lock(&event_mutex);
180         list_for_each_entry(tp_event, &ftrace_events, list) {
181                 if (tp_event->event.type == event_id &&
182                     tp_event->class && tp_event->class->reg &&
183                     try_module_get(tp_event->mod)) {
184                         ret = perf_trace_event_init(tp_event, p_event);
185                         if (ret)
186                                 module_put(tp_event->mod);
187                         break;
188                 }
189         }
190         mutex_unlock(&event_mutex);
191
192         return ret;
193 }
194
195 void perf_trace_destroy(struct perf_event *p_event)
196 {
197         mutex_lock(&event_mutex);
198         perf_trace_event_close(p_event);
199         perf_trace_event_unreg(p_event);
200         mutex_unlock(&event_mutex);
201 }
202
203 int perf_trace_add(struct perf_event *p_event, int flags)
204 {
205         struct ftrace_event_call *tp_event = p_event->tp_event;
206         struct hlist_head __percpu *pcpu_list;
207         struct hlist_head *list;
208
209         pcpu_list = tp_event->perf_events;
210         if (WARN_ON_ONCE(!pcpu_list))
211                 return -EINVAL;
212
213         if (!(flags & PERF_EF_START))
214                 p_event->hw.state = PERF_HES_STOPPED;
215
216         list = this_cpu_ptr(pcpu_list);
217         hlist_add_head_rcu(&p_event->hlist_entry, list);
218
219         return tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event);
220 }
221
222 void perf_trace_del(struct perf_event *p_event, int flags)
223 {
224         struct ftrace_event_call *tp_event = p_event->tp_event;
225         hlist_del_rcu(&p_event->hlist_entry);
226         tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event);
227 }
228
229 __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
230                                        struct pt_regs *regs, int *rctxp)
231 {
232         struct trace_entry *entry;
233         unsigned long flags;
234         char *raw_data;
235         int pc;
236
237         BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
238
239         pc = preempt_count();
240
241         *rctxp = perf_swevent_get_recursion_context();
242         if (*rctxp < 0)
243                 return NULL;
244
245         raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]);
246
247         /* zero the dead bytes from align to not leak stack to user */
248         memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
249
250         entry = (struct trace_entry *)raw_data;
251         local_save_flags(flags);
252         tracing_generic_entry_update(entry, flags, pc);
253         entry->type = type;
254
255         return raw_data;
256 }
257 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);
258
259 #ifdef CONFIG_FUNCTION_TRACER
260 static void
261 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
262                           struct ftrace_ops *ops, struct pt_regs *pt_regs)
263 {
264         struct ftrace_entry *entry;
265         struct hlist_head *head;
266         struct pt_regs regs;
267         int rctx;
268
269 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \
270                     sizeof(u64)) - sizeof(u32))
271
272         BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE);
273
274         perf_fetch_caller_regs(&regs);
275
276         entry = perf_trace_buf_prepare(ENTRY_SIZE, TRACE_FN, NULL, &rctx);
277         if (!entry)
278                 return;
279
280         entry->ip = ip;
281         entry->parent_ip = parent_ip;
282
283         head = this_cpu_ptr(event_function.perf_events);
284         perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0,
285                               1, &regs, head, NULL);
286
287 #undef ENTRY_SIZE
288 }
289
290 static int perf_ftrace_function_register(struct perf_event *event)
291 {
292         struct ftrace_ops *ops = &event->ftrace_ops;
293
294         ops->flags |= FTRACE_OPS_FL_CONTROL;
295         ops->func = perf_ftrace_function_call;
296         return register_ftrace_function(ops);
297 }
298
299 static int perf_ftrace_function_unregister(struct perf_event *event)
300 {
301         struct ftrace_ops *ops = &event->ftrace_ops;
302         int ret = unregister_ftrace_function(ops);
303         ftrace_free_filter(ops);
304         return ret;
305 }
306
307 static void perf_ftrace_function_enable(struct perf_event *event)
308 {
309         ftrace_function_local_enable(&event->ftrace_ops);
310 }
311
312 static void perf_ftrace_function_disable(struct perf_event *event)
313 {
314         ftrace_function_local_disable(&event->ftrace_ops);
315 }
316
317 int perf_ftrace_event_register(struct ftrace_event_call *call,
318                                enum trace_reg type, void *data)
319 {
320         switch (type) {
321         case TRACE_REG_REGISTER:
322         case TRACE_REG_UNREGISTER:
323                 break;
324         case TRACE_REG_PERF_REGISTER:
325         case TRACE_REG_PERF_UNREGISTER:
326                 return 0;
327         case TRACE_REG_PERF_OPEN:
328                 return perf_ftrace_function_register(data);
329         case TRACE_REG_PERF_CLOSE:
330                 return perf_ftrace_function_unregister(data);
331         case TRACE_REG_PERF_ADD:
332                 perf_ftrace_function_enable(data);
333                 return 0;
334         case TRACE_REG_PERF_DEL:
335                 perf_ftrace_function_disable(data);
336                 return 0;
337         }
338
339         return -EINVAL;
340 }
341 #endif /* CONFIG_FUNCTION_TRACER */