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 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 /* 51 * We don't allow user space callchains for function trace 52 * event, due to issues with page faults while tracing page 53 * fault handler and its overall trickiness nature. 54 */ 55 if (!p_event->attr.exclude_callchain_user) 56 return -EINVAL; 57 58 /* 59 * Same reason to disable user stack dump as for user space 60 * callchains above. 61 */ 62 if (p_event->attr.sample_type & PERF_SAMPLE_STACK_USER) 63 return -EINVAL; 64 } 65 66 /* No tracing, just counting, so no obvious leak */ 67 if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW)) 68 return 0; 69 70 /* Some events are ok to be traced by non-root users... */ 71 if (p_event->attach_state == PERF_ATTACH_TASK) { 72 if (tp_event->flags & TRACE_EVENT_FL_CAP_ANY) 73 return 0; 74 } 75 76 /* 77 * ...otherwise raw tracepoint data can be a severe data leak, 78 * only allow root to have these. 79 */ 80 if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN)) 81 return -EPERM; 82 83 return 0; 84 } 85 86 static int perf_trace_event_reg(struct ftrace_event_call *tp_event, 87 struct perf_event *p_event) 88 { 89 struct hlist_head __percpu *list; 90 int ret = -ENOMEM; 91 int cpu; 92 93 p_event->tp_event = tp_event; 94 if (tp_event->perf_refcount++ > 0) 95 return 0; 96 97 list = alloc_percpu(struct hlist_head); 98 if (!list) 99 goto fail; 100 101 for_each_possible_cpu(cpu) 102 INIT_HLIST_HEAD(per_cpu_ptr(list, cpu)); 103 104 tp_event->perf_events = list; 105 106 if (!total_ref_count) { 107 char __percpu *buf; 108 int i; 109 110 for (i = 0; i < PERF_NR_CONTEXTS; i++) { 111 buf = (char __percpu *)alloc_percpu(perf_trace_t); 112 if (!buf) 113 goto fail; 114 115 perf_trace_buf[i] = buf; 116 } 117 } 118 119 ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER, NULL); 120 if (ret) 121 goto fail; 122 123 total_ref_count++; 124 return 0; 125 126 fail: 127 if (!total_ref_count) { 128 int i; 129 130 for (i = 0; i < PERF_NR_CONTEXTS; i++) { 131 free_percpu(perf_trace_buf[i]); 132 perf_trace_buf[i] = NULL; 133 } 134 } 135 136 if (!--tp_event->perf_refcount) { 137 free_percpu(tp_event->perf_events); 138 tp_event->perf_events = NULL; 139 } 140 141 return ret; 142 } 143 144 static void perf_trace_event_unreg(struct perf_event *p_event) 145 { 146 struct ftrace_event_call *tp_event = p_event->tp_event; 147 int i; 148 149 if (--tp_event->perf_refcount > 0) 150 goto out; 151 152 tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER, NULL); 153 154 /* 155 * Ensure our callback won't be called anymore. The buffers 156 * will be freed after that. 157 */ 158 tracepoint_synchronize_unregister(); 159 160 free_percpu(tp_event->perf_events); 161 tp_event->perf_events = NULL; 162 163 if (!--total_ref_count) { 164 for (i = 0; i < PERF_NR_CONTEXTS; i++) { 165 free_percpu(perf_trace_buf[i]); 166 perf_trace_buf[i] = NULL; 167 } 168 } 169 out: 170 module_put(tp_event->mod); 171 } 172 173 static int perf_trace_event_open(struct perf_event *p_event) 174 { 175 struct ftrace_event_call *tp_event = p_event->tp_event; 176 return tp_event->class->reg(tp_event, TRACE_REG_PERF_OPEN, p_event); 177 } 178 179 static void perf_trace_event_close(struct perf_event *p_event) 180 { 181 struct ftrace_event_call *tp_event = p_event->tp_event; 182 tp_event->class->reg(tp_event, TRACE_REG_PERF_CLOSE, p_event); 183 } 184 185 static int perf_trace_event_init(struct ftrace_event_call *tp_event, 186 struct perf_event *p_event) 187 { 188 int ret; 189 190 ret = perf_trace_event_perm(tp_event, p_event); 191 if (ret) 192 return ret; 193 194 ret = perf_trace_event_reg(tp_event, p_event); 195 if (ret) 196 return ret; 197 198 ret = perf_trace_event_open(p_event); 199 if (ret) { 200 perf_trace_event_unreg(p_event); 201 return ret; 202 } 203 204 return 0; 205 } 206 207 int perf_trace_init(struct perf_event *p_event) 208 { 209 struct ftrace_event_call *tp_event; 210 u64 event_id = p_event->attr.config; 211 int ret = -EINVAL; 212 213 mutex_lock(&event_mutex); 214 list_for_each_entry(tp_event, &ftrace_events, list) { 215 if (tp_event->event.type == event_id && 216 tp_event->class && tp_event->class->reg && 217 try_module_get(tp_event->mod)) { 218 ret = perf_trace_event_init(tp_event, p_event); 219 if (ret) 220 module_put(tp_event->mod); 221 break; 222 } 223 } 224 mutex_unlock(&event_mutex); 225 226 return ret; 227 } 228 229 void perf_trace_destroy(struct perf_event *p_event) 230 { 231 mutex_lock(&event_mutex); 232 perf_trace_event_close(p_event); 233 perf_trace_event_unreg(p_event); 234 mutex_unlock(&event_mutex); 235 } 236 237 int perf_trace_add(struct perf_event *p_event, int flags) 238 { 239 struct ftrace_event_call *tp_event = p_event->tp_event; 240 struct hlist_head __percpu *pcpu_list; 241 struct hlist_head *list; 242 243 pcpu_list = tp_event->perf_events; 244 if (WARN_ON_ONCE(!pcpu_list)) 245 return -EINVAL; 246 247 if (!(flags & PERF_EF_START)) 248 p_event->hw.state = PERF_HES_STOPPED; 249 250 list = this_cpu_ptr(pcpu_list); 251 hlist_add_head_rcu(&p_event->hlist_entry, list); 252 253 return tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event); 254 } 255 256 void perf_trace_del(struct perf_event *p_event, int flags) 257 { 258 struct ftrace_event_call *tp_event = p_event->tp_event; 259 hlist_del_rcu(&p_event->hlist_entry); 260 tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event); 261 } 262 263 void *perf_trace_buf_prepare(int size, unsigned short type, 264 struct pt_regs *regs, int *rctxp) 265 { 266 struct trace_entry *entry; 267 unsigned long flags; 268 char *raw_data; 269 int pc; 270 271 BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long)); 272 273 if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, 274 "perf buffer not large enough")) 275 return NULL; 276 277 pc = preempt_count(); 278 279 *rctxp = perf_swevent_get_recursion_context(); 280 if (*rctxp < 0) 281 return NULL; 282 283 raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]); 284 285 /* zero the dead bytes from align to not leak stack to user */ 286 memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64)); 287 288 entry = (struct trace_entry *)raw_data; 289 local_save_flags(flags); 290 tracing_generic_entry_update(entry, flags, pc); 291 entry->type = type; 292 293 return raw_data; 294 } 295 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare); 296 NOKPROBE_SYMBOL(perf_trace_buf_prepare); 297 298 #ifdef CONFIG_FUNCTION_TRACER 299 static void 300 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, 301 struct ftrace_ops *ops, struct pt_regs *pt_regs) 302 { 303 struct ftrace_entry *entry; 304 struct hlist_head *head; 305 struct pt_regs regs; 306 int rctx; 307 308 head = this_cpu_ptr(event_function.perf_events); 309 if (hlist_empty(head)) 310 return; 311 312 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \ 313 sizeof(u64)) - sizeof(u32)) 314 315 BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE); 316 317 perf_fetch_caller_regs(®s); 318 319 entry = perf_trace_buf_prepare(ENTRY_SIZE, TRACE_FN, NULL, &rctx); 320 if (!entry) 321 return; 322 323 entry->ip = ip; 324 entry->parent_ip = parent_ip; 325 perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0, 326 1, ®s, head, NULL); 327 328 #undef ENTRY_SIZE 329 } 330 331 static int perf_ftrace_function_register(struct perf_event *event) 332 { 333 struct ftrace_ops *ops = &event->ftrace_ops; 334 335 ops->flags |= FTRACE_OPS_FL_CONTROL; 336 ops->func = perf_ftrace_function_call; 337 return register_ftrace_function(ops); 338 } 339 340 static int perf_ftrace_function_unregister(struct perf_event *event) 341 { 342 struct ftrace_ops *ops = &event->ftrace_ops; 343 int ret = unregister_ftrace_function(ops); 344 ftrace_free_filter(ops); 345 return ret; 346 } 347 348 static void perf_ftrace_function_enable(struct perf_event *event) 349 { 350 ftrace_function_local_enable(&event->ftrace_ops); 351 } 352 353 static void perf_ftrace_function_disable(struct perf_event *event) 354 { 355 ftrace_function_local_disable(&event->ftrace_ops); 356 } 357 358 int perf_ftrace_event_register(struct ftrace_event_call *call, 359 enum trace_reg type, void *data) 360 { 361 switch (type) { 362 case TRACE_REG_REGISTER: 363 case TRACE_REG_UNREGISTER: 364 break; 365 case TRACE_REG_PERF_REGISTER: 366 case TRACE_REG_PERF_UNREGISTER: 367 return 0; 368 case TRACE_REG_PERF_OPEN: 369 return perf_ftrace_function_register(data); 370 case TRACE_REG_PERF_CLOSE: 371 return perf_ftrace_function_unregister(data); 372 case TRACE_REG_PERF_ADD: 373 perf_ftrace_function_enable(data); 374 return 0; 375 case TRACE_REG_PERF_DEL: 376 perf_ftrace_function_disable(data); 377 return 0; 378 } 379 380 return -EINVAL; 381 } 382 #endif /* CONFIG_FUNCTION_TRACER */ 383