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 struct hlist_head __percpu *pcpu_list; 244 struct hlist_head *list; 245 246 pcpu_list = tp_event->perf_events; 247 if (WARN_ON_ONCE(!pcpu_list)) 248 return -EINVAL; 249 250 if (!(flags & PERF_EF_START)) 251 p_event->hw.state = PERF_HES_STOPPED; 252 253 list = this_cpu_ptr(pcpu_list); 254 hlist_add_head_rcu(&p_event->hlist_entry, list); 255 256 return tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event); 257 } 258 259 void perf_trace_del(struct perf_event *p_event, int flags) 260 { 261 struct trace_event_call *tp_event = p_event->tp_event; 262 hlist_del_rcu(&p_event->hlist_entry); 263 tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event); 264 } 265 266 void *perf_trace_buf_prepare(int size, unsigned short type, 267 struct pt_regs **regs, int *rctxp) 268 { 269 struct trace_entry *entry; 270 unsigned long flags; 271 char *raw_data; 272 int pc; 273 274 BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long)); 275 276 if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, 277 "perf buffer not large enough")) 278 return NULL; 279 280 pc = preempt_count(); 281 282 *rctxp = perf_swevent_get_recursion_context(); 283 if (*rctxp < 0) 284 return NULL; 285 286 if (regs) 287 *regs = this_cpu_ptr(&__perf_regs[*rctxp]); 288 raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]); 289 290 /* zero the dead bytes from align to not leak stack to user */ 291 memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64)); 292 293 entry = (struct trace_entry *)raw_data; 294 local_save_flags(flags); 295 tracing_generic_entry_update(entry, flags, pc); 296 entry->type = type; 297 298 return raw_data; 299 } 300 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare); 301 NOKPROBE_SYMBOL(perf_trace_buf_prepare); 302 303 #ifdef CONFIG_FUNCTION_TRACER 304 static void 305 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, 306 struct ftrace_ops *ops, struct pt_regs *pt_regs) 307 { 308 struct ftrace_entry *entry; 309 struct hlist_head *head; 310 struct pt_regs regs; 311 int rctx; 312 313 head = this_cpu_ptr(event_function.perf_events); 314 if (hlist_empty(head)) 315 return; 316 317 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \ 318 sizeof(u64)) - sizeof(u32)) 319 320 BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE); 321 322 perf_fetch_caller_regs(®s); 323 324 entry = perf_trace_buf_prepare(ENTRY_SIZE, TRACE_FN, NULL, &rctx); 325 if (!entry) 326 return; 327 328 entry->ip = ip; 329 entry->parent_ip = parent_ip; 330 perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0, 331 1, ®s, head, NULL); 332 333 #undef ENTRY_SIZE 334 } 335 336 static int perf_ftrace_function_register(struct perf_event *event) 337 { 338 struct ftrace_ops *ops = &event->ftrace_ops; 339 340 ops->flags |= FTRACE_OPS_FL_PER_CPU | FTRACE_OPS_FL_RCU; 341 ops->func = perf_ftrace_function_call; 342 return register_ftrace_function(ops); 343 } 344 345 static int perf_ftrace_function_unregister(struct perf_event *event) 346 { 347 struct ftrace_ops *ops = &event->ftrace_ops; 348 int ret = unregister_ftrace_function(ops); 349 ftrace_free_filter(ops); 350 return ret; 351 } 352 353 static void perf_ftrace_function_enable(struct perf_event *event) 354 { 355 ftrace_function_local_enable(&event->ftrace_ops); 356 } 357 358 static void perf_ftrace_function_disable(struct perf_event *event) 359 { 360 ftrace_function_local_disable(&event->ftrace_ops); 361 } 362 363 int perf_ftrace_event_register(struct trace_event_call *call, 364 enum trace_reg type, void *data) 365 { 366 switch (type) { 367 case TRACE_REG_REGISTER: 368 case TRACE_REG_UNREGISTER: 369 break; 370 case TRACE_REG_PERF_REGISTER: 371 case TRACE_REG_PERF_UNREGISTER: 372 return 0; 373 case TRACE_REG_PERF_OPEN: 374 return perf_ftrace_function_register(data); 375 case TRACE_REG_PERF_CLOSE: 376 return perf_ftrace_function_unregister(data); 377 case TRACE_REG_PERF_ADD: 378 perf_ftrace_function_enable(data); 379 return 0; 380 case TRACE_REG_PERF_DEL: 381 perf_ftrace_function_disable(data); 382 return 0; 383 } 384 385 return -EINVAL; 386 } 387 #endif /* CONFIG_FUNCTION_TRACER */ 388