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         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         if (regs)
 284                 *regs = this_cpu_ptr(&__perf_regs[*rctxp]);
 285         raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]);
 286
 287         /* zero the dead bytes from align to not leak stack to user */
 288         memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
 289
 290         entry = (struct trace_entry *)raw_data;
 291         local_save_flags(flags);
 292         tracing_generic_entry_update(entry, flags, pc);
 293         entry->type = type;
 294
 295         return raw_data;
 296 }
 297 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);
 298 NOKPROBE_SYMBOL(perf_trace_buf_prepare);
 299
 300 #ifdef CONFIG_FUNCTION_TRACER
 301 static void
 302 perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
 303                           struct ftrace_ops *ops, struct pt_regs *pt_regs)
 304 {
 305         struct ftrace_entry *entry;
 306         struct hlist_head *head;
 307         struct pt_regs regs;
 308         int rctx;
 309
 310         head = this_cpu_ptr(event_function.perf_events);
 311         if (hlist_empty(head))
 312                 return;
 313
 314 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \
 315                     sizeof(u64)) - sizeof(u32))
 316
 317         BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE);
 318
 319         perf_fetch_caller_regs(&regs);
 320
 321         entry = perf_trace_buf_prepare(ENTRY_SIZE, TRACE_FN, NULL, &rctx);
 322         if (!entry)
 323                 return;
 324
 325         entry->ip = ip;
 326         entry->parent_ip = parent_ip;
 327         perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0,
 328                               1, &regs, head, NULL);
 329
 330 #undef ENTRY_SIZE
 331 }
 332
 333 static int perf_ftrace_function_register(struct perf_event *event)
 334 {
 335         struct ftrace_ops *ops = &event->ftrace_ops;
 336
 337         ops->flags |= FTRACE_OPS_FL_CONTROL;
 338         ops->func = perf_ftrace_function_call;
 339         return register_ftrace_function(ops);
 340 }
 341
 342 static int perf_ftrace_function_unregister(struct perf_event *event)
 343 {
 344         struct ftrace_ops *ops = &event->ftrace_ops;
 345         int ret = unregister_ftrace_function(ops);
 346         ftrace_free_filter(ops);
 347         return ret;
 348 }
 349
 350 static void perf_ftrace_function_enable(struct perf_event *event)
 351 {
 352         ftrace_function_local_enable(&event->ftrace_ops);
 353 }
 354
 355 static void perf_ftrace_function_disable(struct perf_event *event)
 356 {
 357         ftrace_function_local_disable(&event->ftrace_ops);
 358 }
 359
 360 int perf_ftrace_event_register(struct ftrace_event_call *call,
 361                                enum trace_reg type, void *data)
 362 {
 363         switch (type) {
 364         case TRACE_REG_REGISTER:
 365         case TRACE_REG_UNREGISTER:
 366                 break;
 367         case TRACE_REG_PERF_REGISTER:
 368         case TRACE_REG_PERF_UNREGISTER:
 369                 return 0;
 370         case TRACE_REG_PERF_OPEN:
 371                 return perf_ftrace_function_register(data);
 372         case TRACE_REG_PERF_CLOSE:
 373                 return perf_ftrace_function_unregister(data);
 374         case TRACE_REG_PERF_ADD:
 375                 perf_ftrace_function_enable(data);
 376                 return 0;
 377         case TRACE_REG_PERF_DEL:
 378                 perf_ftrace_function_disable(data);
 379                 return 0;
 380         }
 381
 382         return -EINVAL;
 383 }
 384 #endif /* CONFIG_FUNCTION_TRACER */