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 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 trace_event_call *tp_event, 25 struct perf_event *p_event) 26 { 27 if (tp_event->perf_perm) { 28 int ret = tp_event->perf_perm(tp_event, p_event); 29 if (ret) 30 return ret; 31 } 32 33 /* 34 * We checked and allowed to create parent, 35 * allow children without checking. 36 */ 37 if (p_event->parent) 38 return 0; 39 40 /* 41 * It's ok to check current process (owner) permissions in here, 42 * because code below is called only via perf_event_open syscall. 43 */ 44 45 /* The ftrace function trace is allowed only for root. */ 46 if (ftrace_event_is_function(tp_event)) { 47 if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN)) 48 return -EPERM; 49 50 if (!is_sampling_event(p_event)) 51 return 0; 52 53 /* 54 * We don't allow user space callchains for function trace 55 * event, due to issues with page faults while tracing page 56 * fault handler and its overall trickiness nature. 57 */ 58 if (!p_event->attr.exclude_callchain_user) 59 return -EINVAL; 60 61 /* 62 * Same reason to disable user stack dump as for user space 63 * callchains above. 64 */ 65 if (p_event->attr.sample_type & PERF_SAMPLE_STACK_USER) 66 return -EINVAL; 67 } 68 69 /* No tracing, just counting, so no obvious leak */ 70 if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW)) 71 return 0; 72 73 /* Some events are ok to be traced by non-root users... */ 74 if (p_event->attach_state == PERF_ATTACH_TASK) { 75 if (tp_event->flags & TRACE_EVENT_FL_CAP_ANY) 76 return 0; 77 } 78 79 /* 80 * ...otherwise raw tracepoint data can be a severe data leak, 81 * only allow root to have these. 82 */ 83 if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN)) 84 return -EPERM; 85 86 return 0; 87 } 88 89 static int perf_trace_event_reg(struct trace_event_call *tp_event, 90 struct perf_event *p_event) 91 { 92 struct hlist_head __percpu *list; 93 int ret = -ENOMEM; 94 int cpu; 95 96 p_event->tp_event = tp_event; 97 if (tp_event->perf_refcount++ > 0) 98 return 0; 99 100 list = alloc_percpu(struct hlist_head); 101 if (!list) 102 goto fail; 103 104 for_each_possible_cpu(cpu) 105 INIT_HLIST_HEAD(per_cpu_ptr(list, cpu)); 106 107 tp_event->perf_events = list; 108 109 if (!total_ref_count) { 110 char __percpu *buf; 111 int i; 112 113 for (i = 0; i < PERF_NR_CONTEXTS; i++) { 114 buf = (char __percpu *)alloc_percpu(perf_trace_t); 115 if (!buf) 116 goto fail; 117 118 perf_trace_buf[i] = buf; 119 } 120 } 121 122 ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER, NULL); 123 if (ret) 124 goto fail; 125 126 total_ref_count++; 127 return 0; 128 129 fail: 130 if (!total_ref_count) { 131 int i; 132 133 for (i = 0; i < PERF_NR_CONTEXTS; i++) { 134 free_percpu(perf_trace_buf[i]); 135 perf_trace_buf[i] = NULL; 136 } 137 } 138 139 if (!--tp_event->perf_refcount) { 140 free_percpu(tp_event->perf_events); 141 tp_event->perf_events = NULL; 142 } 143 144 return ret; 145 } 146 147 static void perf_trace_event_unreg(struct perf_event *p_event) 148 { 149 struct trace_event_call *tp_event = p_event->tp_event; 150 int i; 151 152 if (--tp_event->perf_refcount > 0) 153 goto out; 154 155 tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER, NULL); 156 157 /* 158 * Ensure our callback won't be called anymore. The buffers 159 * will be freed after that. 160 */ 161 tracepoint_synchronize_unregister(); 162 163 free_percpu(tp_event->perf_events); 164 tp_event->perf_events = NULL; 165 166 if (!--total_ref_count) { 167 for (i = 0; i < PERF_NR_CONTEXTS; i++) { 168 free_percpu(perf_trace_buf[i]); 169 perf_trace_buf[i] = NULL; 170 } 171 } 172 out: 173 module_put(tp_event->mod); 174 } 175 176 static int perf_trace_event_open(struct perf_event *p_event) 177 { 178 struct trace_event_call *tp_event = p_event->tp_event; 179 return tp_event->class->reg(tp_event, TRACE_REG_PERF_OPEN, p_event); 180 } 181 182 static void perf_trace_event_close(struct perf_event *p_event) 183 { 184 struct trace_event_call *tp_event = p_event->tp_event; 185 tp_event->class->reg(tp_event, TRACE_REG_PERF_CLOSE, p_event); 186 } 187 188 static int perf_trace_event_init(struct trace_event_call *tp_event, 189 struct perf_event *p_event) 190 { 191 int ret; 192 193 ret = perf_trace_event_perm(tp_event, p_event); 194 if (ret) 195 return ret; 196 197 ret = perf_trace_event_reg(tp_event, p_event); 198 if (ret) 199 return ret; 200 201 ret = perf_trace_event_open(p_event); 202 if (ret) { 203 perf_trace_event_unreg(p_event); 204 return ret; 205 } 206 207 return 0; 208 } 209 210 int perf_trace_init(struct perf_event *p_event) 211 { 212 struct trace_event_call *tp_event; 213 u64 event_id = p_event->attr.config; 214 int ret = -EINVAL; 215 216 mutex_lock(&event_mutex); 217 list_for_each_entry(tp_event, &ftrace_events, list) { 218 if (tp_event->event.type == event_id && 219 tp_event->class && tp_event->class->reg && 220 try_module_get(tp_event->mod)) { 221 ret = perf_trace_event_init(tp_event, p_event); 222 if (ret) 223 module_put(tp_event->mod); 224 break; 225 } 226 } 227 mutex_unlock(&event_mutex); 228 229 return ret; 230 } 231 232 void perf_trace_destroy(struct perf_event *p_event) 233 { 234 mutex_lock(&event_mutex); 235 perf_trace_event_close(p_event); 236 perf_trace_event_unreg(p_event); 237 mutex_unlock(&event_mutex); 238 } 239 240 int perf_trace_add(struct perf_event *p_event, int flags) 241 { 242 struct trace_event_call *tp_event = p_event->tp_event; 243 244 if (!(flags & PERF_EF_START)) 245 p_event->hw.state = PERF_HES_STOPPED; 246 247 /* 248 * If TRACE_REG_PERF_ADD returns false; no custom action was performed 249 * and we need to take the default action of enqueueing our event on 250 * the right per-cpu hlist. 251 */ 252 if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event)) { 253 struct hlist_head __percpu *pcpu_list; 254 struct hlist_head *list; 255 256 pcpu_list = tp_event->perf_events; 257 if (WARN_ON_ONCE(!pcpu_list)) 258 return -EINVAL; 259 260 list = this_cpu_ptr(pcpu_list); 261 hlist_add_head_rcu(&p_event->hlist_entry, list); 262 } 263 264 return 0; 265 } 266 267 void perf_trace_del(struct perf_event *p_event, int flags) 268 { 269 struct trace_event_call *tp_event = p_event->tp_event; 270 271 /* 272 * If TRACE_REG_PERF_DEL returns false; no custom action was performed 273 * and we need to take the default action of dequeueing our event from 274 * the right per-cpu hlist. 275 */ 276 if (!tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event)) 277 hlist_del_rcu(&p_event->hlist_entry); 278 } 279 280 void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp) 281 { 282 char *raw_data; 283 int rctx; 284 285 BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long)); 286 287 if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, 288 "perf buffer not large enough")) 289 return NULL; 290 291 *rctxp = rctx = perf_swevent_get_recursion_context(); 292 if (rctx < 0) 293 return NULL; 294 295 if (regs) 296 *regs = this_cpu_ptr(&__perf_regs[rctx]); 297 raw_data = this_cpu_ptr(perf_trace_buf[rctx]); 298 299 /* zero the dead bytes from align to not leak stack to user */ 300 memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64)); 301 return raw_data; 302 } 303 EXPORT_SYMBOL_GPL(perf_trace_buf_alloc); 304 NOKPROBE_SYMBOL(perf_trace_buf_alloc); 305 306 void perf_trace_buf_update(void *record, u16 type) 307 { 308 struct trace_entry *entry = record; 309 int pc = preempt_count(); 310 unsigned long flags; 311 312 local_save_flags(flags); 313 tracing_generic_entry_update(entry, flags, pc); 314 entry->type = type; 315 } 316 NOKPROBE_SYMBOL(perf_trace_buf_update); 317 318 #ifdef CONFIG_FUNCTION_TRACER 319 static void 320 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, 321 struct ftrace_ops *ops, struct pt_regs *pt_regs) 322 { 323 struct ftrace_entry *entry; 324 struct perf_event *event; 325 struct hlist_head head; 326 struct pt_regs regs; 327 int rctx; 328 329 if ((unsigned long)ops->private != smp_processor_id()) 330 return; 331 332 event = container_of(ops, struct perf_event, ftrace_ops); 333 334 /* 335 * @event->hlist entry is NULL (per INIT_HLIST_NODE), and all 336 * the perf code does is hlist_for_each_entry_rcu(), so we can 337 * get away with simply setting the @head.first pointer in order 338 * to create a singular list. 339 */ 340 head.first = &event->hlist_entry; 341 342 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \ 343 sizeof(u64)) - sizeof(u32)) 344 345 BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE); 346 347 memset(®s, 0, sizeof(regs)); 348 perf_fetch_caller_regs(®s); 349 350 entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx); 351 if (!entry) 352 return; 353 354 entry->ip = ip; 355 entry->parent_ip = parent_ip; 356 perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN, 357 1, ®s, &head, NULL); 358 359 #undef ENTRY_SIZE 360 } 361 362 static int perf_ftrace_function_register(struct perf_event *event) 363 { 364 struct ftrace_ops *ops = &event->ftrace_ops; 365 366 ops->flags = FTRACE_OPS_FL_RCU; 367 ops->func = perf_ftrace_function_call; 368 ops->private = (void *)(unsigned long)nr_cpu_ids; 369 370 return register_ftrace_function(ops); 371 } 372 373 static int perf_ftrace_function_unregister(struct perf_event *event) 374 { 375 struct ftrace_ops *ops = &event->ftrace_ops; 376 int ret = unregister_ftrace_function(ops); 377 ftrace_free_filter(ops); 378 return ret; 379 } 380 381 int perf_ftrace_event_register(struct trace_event_call *call, 382 enum trace_reg type, void *data) 383 { 384 struct perf_event *event = data; 385 386 switch (type) { 387 case TRACE_REG_REGISTER: 388 case TRACE_REG_UNREGISTER: 389 break; 390 case TRACE_REG_PERF_REGISTER: 391 case TRACE_REG_PERF_UNREGISTER: 392 return 0; 393 case TRACE_REG_PERF_OPEN: 394 return perf_ftrace_function_register(data); 395 case TRACE_REG_PERF_CLOSE: 396 return perf_ftrace_function_unregister(data); 397 case TRACE_REG_PERF_ADD: 398 event->ftrace_ops.private = (void *)(unsigned long)smp_processor_id(); 399 return 1; 400 case TRACE_REG_PERF_DEL: 401 event->ftrace_ops.private = (void *)(unsigned long)nr_cpu_ids; 402 return 1; 403 } 404 405 return -EINVAL; 406 } 407 #endif /* CONFIG_FUNCTION_TRACER */ 408