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 /* The ftrace function trace is allowed only for root. */ 34 if (ftrace_event_is_function(tp_event) && 35 perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN)) 36 return -EPERM; 37 38 /* No tracing, just counting, so no obvious leak */ 39 if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW)) 40 return 0; 41 42 /* Some events are ok to be traced by non-root users... */ 43 if (p_event->attach_state == PERF_ATTACH_TASK) { 44 if (tp_event->flags & TRACE_EVENT_FL_CAP_ANY) 45 return 0; 46 } 47 48 /* 49 * ...otherwise raw tracepoint data can be a severe data leak, 50 * only allow root to have these. 51 */ 52 if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN)) 53 return -EPERM; 54 55 return 0; 56 } 57 58 static int perf_trace_event_reg(struct ftrace_event_call *tp_event, 59 struct perf_event *p_event) 60 { 61 struct hlist_head __percpu *list; 62 int ret = -ENOMEM; 63 int cpu; 64 65 p_event->tp_event = tp_event; 66 if (tp_event->perf_refcount++ > 0) 67 return 0; 68 69 list = alloc_percpu(struct hlist_head); 70 if (!list) 71 goto fail; 72 73 for_each_possible_cpu(cpu) 74 INIT_HLIST_HEAD(per_cpu_ptr(list, cpu)); 75 76 tp_event->perf_events = list; 77 78 if (!total_ref_count) { 79 char __percpu *buf; 80 int i; 81 82 for (i = 0; i < PERF_NR_CONTEXTS; i++) { 83 buf = (char __percpu *)alloc_percpu(perf_trace_t); 84 if (!buf) 85 goto fail; 86 87 perf_trace_buf[i] = buf; 88 } 89 } 90 91 ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER, NULL); 92 if (ret) 93 goto fail; 94 95 total_ref_count++; 96 return 0; 97 98 fail: 99 if (!total_ref_count) { 100 int i; 101 102 for (i = 0; i < PERF_NR_CONTEXTS; i++) { 103 free_percpu(perf_trace_buf[i]); 104 perf_trace_buf[i] = NULL; 105 } 106 } 107 108 if (!--tp_event->perf_refcount) { 109 free_percpu(tp_event->perf_events); 110 tp_event->perf_events = NULL; 111 } 112 113 return ret; 114 } 115 116 static void perf_trace_event_unreg(struct perf_event *p_event) 117 { 118 struct ftrace_event_call *tp_event = p_event->tp_event; 119 int i; 120 121 if (--tp_event->perf_refcount > 0) 122 goto out; 123 124 tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER, NULL); 125 126 /* 127 * Ensure our callback won't be called anymore. The buffers 128 * will be freed after that. 129 */ 130 tracepoint_synchronize_unregister(); 131 132 free_percpu(tp_event->perf_events); 133 tp_event->perf_events = NULL; 134 135 if (!--total_ref_count) { 136 for (i = 0; i < PERF_NR_CONTEXTS; i++) { 137 free_percpu(perf_trace_buf[i]); 138 perf_trace_buf[i] = NULL; 139 } 140 } 141 out: 142 module_put(tp_event->mod); 143 } 144 145 static int perf_trace_event_open(struct perf_event *p_event) 146 { 147 struct ftrace_event_call *tp_event = p_event->tp_event; 148 return tp_event->class->reg(tp_event, TRACE_REG_PERF_OPEN, p_event); 149 } 150 151 static void perf_trace_event_close(struct perf_event *p_event) 152 { 153 struct ftrace_event_call *tp_event = p_event->tp_event; 154 tp_event->class->reg(tp_event, TRACE_REG_PERF_CLOSE, p_event); 155 } 156 157 static int perf_trace_event_init(struct ftrace_event_call *tp_event, 158 struct perf_event *p_event) 159 { 160 int ret; 161 162 ret = perf_trace_event_perm(tp_event, p_event); 163 if (ret) 164 return ret; 165 166 ret = perf_trace_event_reg(tp_event, p_event); 167 if (ret) 168 return ret; 169 170 ret = perf_trace_event_open(p_event); 171 if (ret) { 172 perf_trace_event_unreg(p_event); 173 return ret; 174 } 175 176 return 0; 177 } 178 179 int perf_trace_init(struct perf_event *p_event) 180 { 181 struct ftrace_event_call *tp_event; 182 u64 event_id = p_event->attr.config; 183 int ret = -EINVAL; 184 185 mutex_lock(&event_mutex); 186 list_for_each_entry(tp_event, &ftrace_events, list) { 187 if (tp_event->event.type == event_id && 188 tp_event->class && tp_event->class->reg && 189 try_module_get(tp_event->mod)) { 190 ret = perf_trace_event_init(tp_event, p_event); 191 if (ret) 192 module_put(tp_event->mod); 193 break; 194 } 195 } 196 mutex_unlock(&event_mutex); 197 198 return ret; 199 } 200 201 void perf_trace_destroy(struct perf_event *p_event) 202 { 203 mutex_lock(&event_mutex); 204 perf_trace_event_close(p_event); 205 perf_trace_event_unreg(p_event); 206 mutex_unlock(&event_mutex); 207 } 208 209 int perf_trace_add(struct perf_event *p_event, int flags) 210 { 211 struct ftrace_event_call *tp_event = p_event->tp_event; 212 struct hlist_head __percpu *pcpu_list; 213 struct hlist_head *list; 214 215 pcpu_list = tp_event->perf_events; 216 if (WARN_ON_ONCE(!pcpu_list)) 217 return -EINVAL; 218 219 if (!(flags & PERF_EF_START)) 220 p_event->hw.state = PERF_HES_STOPPED; 221 222 list = this_cpu_ptr(pcpu_list); 223 hlist_add_head_rcu(&p_event->hlist_entry, list); 224 225 return tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event); 226 } 227 228 void perf_trace_del(struct perf_event *p_event, int flags) 229 { 230 struct ftrace_event_call *tp_event = p_event->tp_event; 231 hlist_del_rcu(&p_event->hlist_entry); 232 tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event); 233 } 234 235 __kprobes void *perf_trace_buf_prepare(int size, unsigned short type, 236 struct pt_regs *regs, int *rctxp) 237 { 238 struct trace_entry *entry; 239 unsigned long flags; 240 char *raw_data; 241 int pc; 242 243 BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long)); 244 245 if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, 246 "perf buffer not large enough")) 247 return NULL; 248 249 pc = preempt_count(); 250 251 *rctxp = perf_swevent_get_recursion_context(); 252 if (*rctxp < 0) 253 return NULL; 254 255 raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]); 256 257 /* zero the dead bytes from align to not leak stack to user */ 258 memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64)); 259 260 entry = (struct trace_entry *)raw_data; 261 local_save_flags(flags); 262 tracing_generic_entry_update(entry, flags, pc); 263 entry->type = type; 264 265 return raw_data; 266 } 267 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare); 268 269 #ifdef CONFIG_FUNCTION_TRACER 270 static void 271 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip, 272 struct ftrace_ops *ops, struct pt_regs *pt_regs) 273 { 274 struct ftrace_entry *entry; 275 struct hlist_head *head; 276 struct pt_regs regs; 277 int rctx; 278 279 head = this_cpu_ptr(event_function.perf_events); 280 if (hlist_empty(head)) 281 return; 282 283 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \ 284 sizeof(u64)) - sizeof(u32)) 285 286 BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE); 287 288 perf_fetch_caller_regs(®s); 289 290 entry = perf_trace_buf_prepare(ENTRY_SIZE, TRACE_FN, NULL, &rctx); 291 if (!entry) 292 return; 293 294 entry->ip = ip; 295 entry->parent_ip = parent_ip; 296 perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0, 297 1, ®s, head, NULL); 298 299 #undef ENTRY_SIZE 300 } 301 302 static int perf_ftrace_function_register(struct perf_event *event) 303 { 304 struct ftrace_ops *ops = &event->ftrace_ops; 305 306 ops->flags |= FTRACE_OPS_FL_CONTROL; 307 ops->func = perf_ftrace_function_call; 308 return register_ftrace_function(ops); 309 } 310 311 static int perf_ftrace_function_unregister(struct perf_event *event) 312 { 313 struct ftrace_ops *ops = &event->ftrace_ops; 314 int ret = unregister_ftrace_function(ops); 315 ftrace_free_filter(ops); 316 return ret; 317 } 318 319 static void perf_ftrace_function_enable(struct perf_event *event) 320 { 321 ftrace_function_local_enable(&event->ftrace_ops); 322 } 323 324 static void perf_ftrace_function_disable(struct perf_event *event) 325 { 326 ftrace_function_local_disable(&event->ftrace_ops); 327 } 328 329 int perf_ftrace_event_register(struct ftrace_event_call *call, 330 enum trace_reg type, void *data) 331 { 332 switch (type) { 333 case TRACE_REG_REGISTER: 334 case TRACE_REG_UNREGISTER: 335 break; 336 case TRACE_REG_PERF_REGISTER: 337 case TRACE_REG_PERF_UNREGISTER: 338 return 0; 339 case TRACE_REG_PERF_OPEN: 340 return perf_ftrace_function_register(data); 341 case TRACE_REG_PERF_CLOSE: 342 return perf_ftrace_function_unregister(data); 343 case TRACE_REG_PERF_ADD: 344 perf_ftrace_function_enable(data); 345 return 0; 346 case TRACE_REG_PERF_DEL: 347 perf_ftrace_function_disable(data); 348 return 0; 349 } 350 351 return -EINVAL; 352 } 353 #endif /* CONFIG_FUNCTION_TRACER */ 354