include/linux/ftrace_event.h

   1
   2 #ifndef _LINUX_FTRACE_EVENT_H
   3 #define _LINUX_FTRACE_EVENT_H
   4
   5 #include <linux/ring_buffer.h>
   6 #include <linux/trace_seq.h>
   7 #include <linux/percpu.h>
   8 #include <linux/hardirq.h>
   9 #include <linux/perf_event.h>
  10 #include <linux/tracepoint.h>
  11
  12 struct trace_array;
  13 struct trace_buffer;
  14 struct tracer;
  15 struct dentry;
  16
  17 struct trace_print_flags {
  18         unsigned long           mask;
  19         const char              *name;
  20 };
  21
  22 struct trace_print_flags_u64 {
  23         unsigned long long      mask;
  24         const char              *name;
  25 };
  26
  27 const char *ftrace_print_flags_seq(struct trace_seq *p, const char *delim,
  28                                    unsigned long flags,
  29                                    const struct trace_print_flags *flag_array);
  30
  31 const char *ftrace_print_symbols_seq(struct trace_seq *p, unsigned long val,
  32                                      const struct trace_print_flags *symbol_array);
  33
  34 #if BITS_PER_LONG == 32
  35 const char *ftrace_print_symbols_seq_u64(struct trace_seq *p,
  36                                          unsigned long long val,
  37                                          const struct trace_print_flags_u64
  38                                                                  *symbol_array);
  39 #endif
  40
  41 const char *ftrace_print_bitmask_seq(struct trace_seq *p, void *bitmask_ptr,
  42                                      unsigned int bitmask_size);
  43
  44 const char *ftrace_print_hex_seq(struct trace_seq *p,
  45                                  const unsigned char *buf, int len);
  46
  47 struct trace_iterator;
  48 struct trace_event;
  49
  50 int ftrace_raw_output_prep(struct trace_iterator *iter,
  51                            struct trace_event *event);
  52
  53 /*
  54  * The trace entry - the most basic unit of tracing. This is what
  55  * is printed in the end as a single line in the trace output, such as:
  56  *
  57  *     bash-15816 [01]   235.197585: idle_cpu <- irq_enter
  58  */
  59 struct trace_entry {
  60         unsigned short          type;
  61         unsigned char           flags;
  62         unsigned char           preempt_count;
  63         int                     pid;
  64 };
  65
  66 #define FTRACE_MAX_EVENT                                                \
  67         ((1 << (sizeof(((struct trace_entry *)0)->type) * 8)) - 1)
  68
  69 /*
  70  * Trace iterator - used by printout routines who present trace
  71  * results to users and which routines might sleep, etc:
  72  */
  73 struct trace_iterator {
  74         struct trace_array      *tr;
  75         struct tracer           *trace;
  76         struct trace_buffer     *trace_buffer;
  77         void                    *private;
  78         int                     cpu_file;
  79         struct mutex            mutex;
  80         struct ring_buffer_iter **buffer_iter;
  81         unsigned long           iter_flags;
  82
  83         /* trace_seq for __print_flags() and __print_symbolic() etc. */
  84         struct trace_seq        tmp_seq;
  85
  86         cpumask_var_t           started;
  87
  88         /* it's true when current open file is snapshot */
  89         bool                    snapshot;
  90
  91         /* The below is zeroed out in pipe_read */
  92         struct trace_seq        seq;
  93         struct trace_entry      *ent;
  94         unsigned long           lost_events;
  95         int                     leftover;
  96         int                     ent_size;
  97         int                     cpu;
  98         u64                     ts;
  99
 100         loff_t                  pos;
 101         long                    idx;
 102
 103         /* All new field here will be zeroed out in pipe_read */
 104 };
 105
 106 enum trace_iter_flags {
 107         TRACE_FILE_LAT_FMT      = 1,
 108         TRACE_FILE_ANNOTATE     = 2,
 109         TRACE_FILE_TIME_IN_NS   = 4,
 110 };
 111
 112
 113 typedef enum print_line_t (*trace_print_func)(struct trace_iterator *iter,
 114                                       int flags, struct trace_event *event);
 115
 116 struct trace_event_functions {
 117         trace_print_func        trace;
 118         trace_print_func        raw;
 119         trace_print_func        hex;
 120         trace_print_func        binary;
 121 };
 122
 123 struct trace_event {
 124         struct hlist_node               node;
 125         struct list_head                list;
 126         int                             type;
 127         struct trace_event_functions    *funcs;
 128 };
 129
 130 extern int register_ftrace_event(struct trace_event *event);
 131 extern int unregister_ftrace_event(struct trace_event *event);
 132
 133 /* Return values for print_line callback */
 134 enum print_line_t {
 135         TRACE_TYPE_PARTIAL_LINE = 0,    /* Retry after flushing the seq */
 136         TRACE_TYPE_HANDLED      = 1,
 137         TRACE_TYPE_UNHANDLED    = 2,    /* Relay to other output functions */
 138         TRACE_TYPE_NO_CONSUME   = 3     /* Handled but ask to not consume */
 139 };
 140
 141 void tracing_generic_entry_update(struct trace_entry *entry,
 142                                   unsigned long flags,
 143                                   int pc);
 144 struct ftrace_event_file;
 145
 146 struct ring_buffer_event *
 147 trace_event_buffer_lock_reserve(struct ring_buffer **current_buffer,
 148                                 struct ftrace_event_file *ftrace_file,
 149                                 int type, unsigned long len,
 150                                 unsigned long flags, int pc);
 151 struct ring_buffer_event *
 152 trace_current_buffer_lock_reserve(struct ring_buffer **current_buffer,
 153                                   int type, unsigned long len,
 154                                   unsigned long flags, int pc);
 155 void trace_current_buffer_unlock_commit(struct ring_buffer *buffer,
 156                                         struct ring_buffer_event *event,
 157                                         unsigned long flags, int pc);
 158 void trace_buffer_unlock_commit(struct ring_buffer *buffer,
 159                                 struct ring_buffer_event *event,
 160                                 unsigned long flags, int pc);
 161 void trace_buffer_unlock_commit_regs(struct ring_buffer *buffer,
 162                                      struct ring_buffer_event *event,
 163                                      unsigned long flags, int pc,
 164                                      struct pt_regs *regs);
 165 void trace_current_buffer_discard_commit(struct ring_buffer *buffer,
 166                                          struct ring_buffer_event *event);
 167
 168 void tracing_record_cmdline(struct task_struct *tsk);
 169
 170 int ftrace_output_call(struct trace_iterator *iter, char *name, char *fmt, ...);
 171
 172 struct event_filter;
 173
 174 enum trace_reg {
 175         TRACE_REG_REGISTER,
 176         TRACE_REG_UNREGISTER,
 177 #ifdef CONFIG_PERF_EVENTS
 178         TRACE_REG_PERF_REGISTER,
 179         TRACE_REG_PERF_UNREGISTER,
 180         TRACE_REG_PERF_OPEN,
 181         TRACE_REG_PERF_CLOSE,
 182         TRACE_REG_PERF_ADD,
 183         TRACE_REG_PERF_DEL,
 184 #endif
 185 };
 186
 187 struct ftrace_event_call;
 188
 189 struct ftrace_event_class {
 190         char                    *system;
 191         void                    *probe;
 192 #ifdef CONFIG_PERF_EVENTS
 193         void                    *perf_probe;
 194 #endif
 195         int                     (*reg)(struct ftrace_event_call *event,
 196                                        enum trace_reg type, void *data);
 197         int                     (*define_fields)(struct ftrace_event_call *);
 198         struct list_head        *(*get_fields)(struct ftrace_event_call *);
 199         struct list_head        fields;
 200         int                     (*raw_init)(struct ftrace_event_call *);
 201 };
 202
 203 extern int ftrace_event_reg(struct ftrace_event_call *event,
 204                             enum trace_reg type, void *data);
 205
 206 int ftrace_output_event(struct trace_iterator *iter, struct ftrace_event_call *event,
 207                         char *fmt, ...);
 208
 209 int ftrace_event_define_field(struct ftrace_event_call *call,
 210                               char *type, int len, char *item, int offset,
 211                               int field_size, int sign, int filter);
 212
 213 struct ftrace_event_buffer {
 214         struct ring_buffer              *buffer;
 215         struct ring_buffer_event        *event;
 216         struct ftrace_event_file        *ftrace_file;
 217         void                            *entry;
 218         unsigned long                   flags;
 219         int                             pc;
 220 };
 221
 222 void *ftrace_event_buffer_reserve(struct ftrace_event_buffer *fbuffer,
 223                                   struct ftrace_event_file *ftrace_file,
 224                                   unsigned long len);
 225
 226 void ftrace_event_buffer_commit(struct ftrace_event_buffer *fbuffer);
 227
 228 int ftrace_event_define_field(struct ftrace_event_call *call,
 229                               char *type, int len, char *item, int offset,
 230                               int field_size, int sign, int filter);
 231
 232 enum {
 233         TRACE_EVENT_FL_FILTERED_BIT,
 234         TRACE_EVENT_FL_CAP_ANY_BIT,
 235         TRACE_EVENT_FL_NO_SET_FILTER_BIT,
 236         TRACE_EVENT_FL_IGNORE_ENABLE_BIT,
 237         TRACE_EVENT_FL_WAS_ENABLED_BIT,
 238         TRACE_EVENT_FL_USE_CALL_FILTER_BIT,
 239         TRACE_EVENT_FL_TRACEPOINT_BIT,
 240 };
 241
 242 /*
 243  * Event flags:
 244  *  FILTERED      - The event has a filter attached
 245  *  CAP_ANY       - Any user can enable for perf
 246  *  NO_SET_FILTER - Set when filter has error and is to be ignored
 247  *  IGNORE_ENABLE - For ftrace internal events, do not enable with debugfs file
 248  *  WAS_ENABLED   - Set and stays set when an event was ever enabled
 249  *                    (used for module unloading, if a module event is enabled,
 250  *                     it is best to clear the buffers that used it).
 251  *  USE_CALL_FILTER - For ftrace internal events, don't use file filter
 252  *  TRACEPOINT    - Event is a tracepoint
 253  */
 254 enum {
 255         TRACE_EVENT_FL_FILTERED         = (1 << TRACE_EVENT_FL_FILTERED_BIT),
 256         TRACE_EVENT_FL_CAP_ANY          = (1 << TRACE_EVENT_FL_CAP_ANY_BIT),
 257         TRACE_EVENT_FL_NO_SET_FILTER    = (1 << TRACE_EVENT_FL_NO_SET_FILTER_BIT),
 258         TRACE_EVENT_FL_IGNORE_ENABLE    = (1 << TRACE_EVENT_FL_IGNORE_ENABLE_BIT),
 259         TRACE_EVENT_FL_WAS_ENABLED      = (1 << TRACE_EVENT_FL_WAS_ENABLED_BIT),
 260         TRACE_EVENT_FL_USE_CALL_FILTER  = (1 << TRACE_EVENT_FL_USE_CALL_FILTER_BIT),
 261         TRACE_EVENT_FL_TRACEPOINT       = (1 << TRACE_EVENT_FL_TRACEPOINT_BIT),
 262 };
 263
 264 struct ftrace_event_call {
 265         struct list_head        list;
 266         struct ftrace_event_class *class;
 267         union {
 268                 char                    *name;
 269                 /* Set TRACE_EVENT_FL_TRACEPOINT flag when using "tp" */
 270                 struct tracepoint       *tp;
 271         };
 272         struct trace_event      event;
 273         const char              *print_fmt;
 274         struct event_filter     *filter;
 275         struct list_head        *files;
 276         void                    *mod;
 277         void                    *data;
 278         /*
 279          *   bit 0:             filter_active
 280          *   bit 1:             allow trace by non root (cap any)
 281          *   bit 2:             failed to apply filter
 282          *   bit 3:             ftrace internal event (do not enable)
 283          *   bit 4:             Event was enabled by module
 284          *   bit 5:             use call filter rather than file filter
 285          *   bit 6:             Event is a tracepoint
 286          */
 287         int                     flags; /* static flags of different events */
 288
 289 #ifdef CONFIG_PERF_EVENTS
 290         int                             perf_refcount;
 291         struct hlist_head __percpu      *perf_events;
 292
 293         int     (*perf_perm)(struct ftrace_event_call *,
 294                              struct perf_event *);
 295 #endif
 296 };
 297
 298 static inline const char *
 299 ftrace_event_name(struct ftrace_event_call *call)
 300 {
 301         if (call->flags & TRACE_EVENT_FL_TRACEPOINT)
 302                 return call->tp ? call->tp->name : NULL;
 303         else
 304                 return call->name;
 305 }
 306
 307 struct trace_array;
 308 struct ftrace_subsystem_dir;
 309
 310 enum {
 311         FTRACE_EVENT_FL_ENABLED_BIT,
 312         FTRACE_EVENT_FL_RECORDED_CMD_BIT,
 313         FTRACE_EVENT_FL_FILTERED_BIT,
 314         FTRACE_EVENT_FL_NO_SET_FILTER_BIT,
 315         FTRACE_EVENT_FL_SOFT_MODE_BIT,
 316         FTRACE_EVENT_FL_SOFT_DISABLED_BIT,
 317         FTRACE_EVENT_FL_TRIGGER_MODE_BIT,
 318         FTRACE_EVENT_FL_TRIGGER_COND_BIT,
 319 };
 320
 321 /*
 322  * Ftrace event file flags:
 323  *  ENABLED       - The event is enabled
 324  *  RECORDED_CMD  - The comms should be recorded at sched_switch
 325  *  FILTERED      - The event has a filter attached
 326  *  NO_SET_FILTER - Set when filter has error and is to be ignored
 327  *  SOFT_MODE     - The event is enabled/disabled by SOFT_DISABLED
 328  *  SOFT_DISABLED - When set, do not trace the event (even though its
 329  *                   tracepoint may be enabled)
 330  *  TRIGGER_MODE  - When set, invoke the triggers associated with the event
 331  *  TRIGGER_COND  - When set, one or more triggers has an associated filter
 332  */
 333 enum {
 334         FTRACE_EVENT_FL_ENABLED         = (1 << FTRACE_EVENT_FL_ENABLED_BIT),
 335         FTRACE_EVENT_FL_RECORDED_CMD    = (1 << FTRACE_EVENT_FL_RECORDED_CMD_BIT),
 336         FTRACE_EVENT_FL_FILTERED        = (1 << FTRACE_EVENT_FL_FILTERED_BIT),
 337         FTRACE_EVENT_FL_NO_SET_FILTER   = (1 << FTRACE_EVENT_FL_NO_SET_FILTER_BIT),
 338         FTRACE_EVENT_FL_SOFT_MODE       = (1 << FTRACE_EVENT_FL_SOFT_MODE_BIT),
 339         FTRACE_EVENT_FL_SOFT_DISABLED   = (1 << FTRACE_EVENT_FL_SOFT_DISABLED_BIT),
 340         FTRACE_EVENT_FL_TRIGGER_MODE    = (1 << FTRACE_EVENT_FL_TRIGGER_MODE_BIT),
 341         FTRACE_EVENT_FL_TRIGGER_COND    = (1 << FTRACE_EVENT_FL_TRIGGER_COND_BIT),
 342 };
 343
 344 struct ftrace_event_file {
 345         struct list_head                list;
 346         struct ftrace_event_call        *event_call;
 347         struct event_filter             *filter;
 348         struct dentry                   *dir;
 349         struct trace_array              *tr;
 350         struct ftrace_subsystem_dir     *system;
 351         struct list_head                triggers;
 352
 353         /*
 354          * 32 bit flags:
 355          *   bit 0:             enabled
 356          *   bit 1:             enabled cmd record
 357          *   bit 2:             enable/disable with the soft disable bit
 358          *   bit 3:             soft disabled
 359          *   bit 4:             trigger enabled
 360          *
 361          * Note: The bits must be set atomically to prevent races
 362          * from other writers. Reads of flags do not need to be in
 363          * sync as they occur in critical sections. But the way flags
 364          * is currently used, these changes do not affect the code
 365          * except that when a change is made, it may have a slight
 366          * delay in propagating the changes to other CPUs due to
 367          * caching and such. Which is mostly OK ;-)
 368          */
 369         unsigned long           flags;
 370         atomic_t                sm_ref; /* soft-mode reference counter */
 371         atomic_t                tm_ref; /* trigger-mode reference counter */
 372 };
 373
 374 #define __TRACE_EVENT_FLAGS(name, value)                                \
 375         static int __init trace_init_flags_##name(void)                 \
 376         {                                                               \
 377                 event_##name.flags |= value;                            \
 378                 return 0;                                               \
 379         }                                                               \
 380         early_initcall(trace_init_flags_##name);
 381
 382 #define __TRACE_EVENT_PERF_PERM(name, expr...)                          \
 383         static int perf_perm_##name(struct ftrace_event_call *tp_event, \
 384                                     struct perf_event *p_event)         \
 385         {                                                               \
 386                 return ({ expr; });                                     \
 387         }                                                               \
 388         static int __init trace_init_perf_perm_##name(void)             \
 389         {                                                               \
 390                 event_##name.perf_perm = &perf_perm_##name;             \
 391                 return 0;                                               \
 392         }                                                               \
 393         early_initcall(trace_init_perf_perm_##name);
 394
 395 #define PERF_MAX_TRACE_SIZE     2048
 396
 397 #define MAX_FILTER_STR_VAL      256     /* Should handle KSYM_SYMBOL_LEN */
 398
 399 enum event_trigger_type {
 400         ETT_NONE                = (0),
 401         ETT_TRACE_ONOFF         = (1 << 0),
 402         ETT_SNAPSHOT            = (1 << 1),
 403         ETT_STACKTRACE          = (1 << 2),
 404         ETT_EVENT_ENABLE        = (1 << 3),
 405 };
 406
 407 extern void destroy_preds(struct ftrace_event_file *file);
 408 extern void destroy_call_preds(struct ftrace_event_call *call);
 409 extern int filter_match_preds(struct event_filter *filter, void *rec);
 410
 411 extern int filter_check_discard(struct ftrace_event_file *file, void *rec,
 412                                 struct ring_buffer *buffer,
 413                                 struct ring_buffer_event *event);
 414 extern int call_filter_check_discard(struct ftrace_event_call *call, void *rec,
 415                                      struct ring_buffer *buffer,
 416                                      struct ring_buffer_event *event);
 417 extern enum event_trigger_type event_triggers_call(struct ftrace_event_file *file,
 418                                                    void *rec);
 419 extern void event_triggers_post_call(struct ftrace_event_file *file,
 420                                      enum event_trigger_type tt);
 421
 422 /**
 423  * ftrace_trigger_soft_disabled - do triggers and test if soft disabled
 424  * @file: The file pointer of the event to test
 425  *
 426  * If any triggers without filters are attached to this event, they
 427  * will be called here. If the event is soft disabled and has no
 428  * triggers that require testing the fields, it will return true,
 429  * otherwise false.
 430  */
 431 static inline bool
 432 ftrace_trigger_soft_disabled(struct ftrace_event_file *file)
 433 {
 434         unsigned long eflags = file->flags;
 435
 436         if (!(eflags & FTRACE_EVENT_FL_TRIGGER_COND)) {
 437                 if (eflags & FTRACE_EVENT_FL_TRIGGER_MODE)
 438                         event_triggers_call(file, NULL);
 439                 if (eflags & FTRACE_EVENT_FL_SOFT_DISABLED)
 440                         return true;
 441         }
 442         return false;
 443 }
 444
 445 /*
 446  * Helper function for event_trigger_unlock_commit{_regs}().
 447  * If there are event triggers attached to this event that requires
 448  * filtering against its fields, then they wil be called as the
 449  * entry already holds the field information of the current event.
 450  *
 451  * It also checks if the event should be discarded or not.
 452  * It is to be discarded if the event is soft disabled and the
 453  * event was only recorded to process triggers, or if the event
 454  * filter is active and this event did not match the filters.
 455  *
 456  * Returns true if the event is discarded, false otherwise.
 457  */
 458 static inline bool
 459 __event_trigger_test_discard(struct ftrace_event_file *file,
 460                              struct ring_buffer *buffer,
 461                              struct ring_buffer_event *event,
 462                              void *entry,
 463                              enum event_trigger_type *tt)
 464 {
 465         unsigned long eflags = file->flags;
 466
 467         if (eflags & FTRACE_EVENT_FL_TRIGGER_COND)
 468                 *tt = event_triggers_call(file, entry);
 469
 470         if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &file->flags))
 471                 ring_buffer_discard_commit(buffer, event);
 472         else if (!filter_check_discard(file, entry, buffer, event))
 473                 return false;
 474
 475         return true;
 476 }
 477
 478 /**
 479  * event_trigger_unlock_commit - handle triggers and finish event commit
 480  * @file: The file pointer assoctiated to the event
 481  * @buffer: The ring buffer that the event is being written to
 482  * @event: The event meta data in the ring buffer
 483  * @entry: The event itself
 484  * @irq_flags: The state of the interrupts at the start of the event
 485  * @pc: The state of the preempt count at the start of the event.
 486  *
 487  * This is a helper function to handle triggers that require data
 488  * from the event itself. It also tests the event against filters and
 489  * if the event is soft disabled and should be discarded.
 490  */
 491 static inline void
 492 event_trigger_unlock_commit(struct ftrace_event_file *file,
 493                             struct ring_buffer *buffer,
 494                             struct ring_buffer_event *event,
 495                             void *entry, unsigned long irq_flags, int pc)
 496 {
 497         enum event_trigger_type tt = ETT_NONE;
 498
 499         if (!__event_trigger_test_discard(file, buffer, event, entry, &tt))
 500                 trace_buffer_unlock_commit(buffer, event, irq_flags, pc);
 501
 502         if (tt)
 503                 event_triggers_post_call(file, tt);
 504 }
 505
 506 /**
 507  * event_trigger_unlock_commit_regs - handle triggers and finish event commit
 508  * @file: The file pointer assoctiated to the event
 509  * @buffer: The ring buffer that the event is being written to
 510  * @event: The event meta data in the ring buffer
 511  * @entry: The event itself
 512  * @irq_flags: The state of the interrupts at the start of the event
 513  * @pc: The state of the preempt count at the start of the event.
 514  *
 515  * This is a helper function to handle triggers that require data
 516  * from the event itself. It also tests the event against filters and
 517  * if the event is soft disabled and should be discarded.
 518  *
 519  * Same as event_trigger_unlock_commit() but calls
 520  * trace_buffer_unlock_commit_regs() instead of trace_buffer_unlock_commit().
 521  */
 522 static inline void
 523 event_trigger_unlock_commit_regs(struct ftrace_event_file *file,
 524                                  struct ring_buffer *buffer,
 525                                  struct ring_buffer_event *event,
 526                                  void *entry, unsigned long irq_flags, int pc,
 527                                  struct pt_regs *regs)
 528 {
 529         enum event_trigger_type tt = ETT_NONE;
 530
 531         if (!__event_trigger_test_discard(file, buffer, event, entry, &tt))
 532                 trace_buffer_unlock_commit_regs(buffer, event,
 533                                                 irq_flags, pc, regs);
 534
 535         if (tt)
 536                 event_triggers_post_call(file, tt);
 537 }
 538
 539 enum {
 540         FILTER_OTHER = 0,
 541         FILTER_STATIC_STRING,
 542         FILTER_DYN_STRING,
 543         FILTER_PTR_STRING,
 544         FILTER_TRACE_FN,
 545 };
 546
 547 extern int trace_event_raw_init(struct ftrace_event_call *call);
 548 extern int trace_define_field(struct ftrace_event_call *call, const char *type,
 549                               const char *name, int offset, int size,
 550                               int is_signed, int filter_type);
 551 extern int trace_add_event_call(struct ftrace_event_call *call);
 552 extern int trace_remove_event_call(struct ftrace_event_call *call);
 553
 554 #define is_signed_type(type)    (((type)(-1)) < (type)1)
 555
 556 int trace_set_clr_event(const char *system, const char *event, int set);
 557
 558 /*
 559  * The double __builtin_constant_p is because gcc will give us an error
 560  * if we try to allocate the static variable to fmt if it is not a
 561  * constant. Even with the outer if statement optimizing out.
 562  */
 563 #define event_trace_printk(ip, fmt, args...)                            \
 564 do {                                                                    \
 565         __trace_printk_check_format(fmt, ##args);                       \
 566         tracing_record_cmdline(current);                                \
 567         if (__builtin_constant_p(fmt)) {                                \
 568                 static const char *trace_printk_fmt                     \
 569                   __attribute__((section("__trace_printk_fmt"))) =      \
 570                         __builtin_constant_p(fmt) ? fmt : NULL;         \
 571                                                                         \
 572                 __trace_bprintk(ip, trace_printk_fmt, ##args);          \
 573         } else                                                          \
 574                 __trace_printk(ip, fmt, ##args);                        \
 575 } while (0)
 576
 577 /**
 578  * tracepoint_string - register constant persistent string to trace system
 579  * @str - a constant persistent string that will be referenced in tracepoints
 580  *
 581  * If constant strings are being used in tracepoints, it is faster and
 582  * more efficient to just save the pointer to the string and reference
 583  * that with a printf "%s" instead of saving the string in the ring buffer
 584  * and wasting space and time.
 585  *
 586  * The problem with the above approach is that userspace tools that read
 587  * the binary output of the trace buffers do not have access to the string.
 588  * Instead they just show the address of the string which is not very
 589  * useful to users.
 590  *
 591  * With tracepoint_string(), the string will be registered to the tracing
 592  * system and exported to userspace via the debugfs/tracing/printk_formats
 593  * file that maps the string address to the string text. This way userspace
 594  * tools that read the binary buffers have a way to map the pointers to
 595  * the ASCII strings they represent.
 596  *
 597  * The @str used must be a constant string and persistent as it would not
 598  * make sense to show a string that no longer exists. But it is still fine
 599  * to be used with modules, because when modules are unloaded, if they
 600  * had tracepoints, the ring buffers are cleared too. As long as the string
 601  * does not change during the life of the module, it is fine to use
 602  * tracepoint_string() within a module.
 603  */
 604 #define tracepoint_string(str)                                          \
 605         ({                                                              \
 606                 static const char *___tp_str __tracepoint_string = str; \
 607                 ___tp_str;                                              \
 608         })
 609 #define __tracepoint_string     __attribute__((section("__tracepoint_str")))
 610
 611 #ifdef CONFIG_PERF_EVENTS
 612 struct perf_event;
 613
 614 DECLARE_PER_CPU(struct pt_regs, perf_trace_regs);
 615
 616 extern int  perf_trace_init(struct perf_event *event);
 617 extern void perf_trace_destroy(struct perf_event *event);
 618 extern int  perf_trace_add(struct perf_event *event, int flags);
 619 extern void perf_trace_del(struct perf_event *event, int flags);
 620 extern int  ftrace_profile_set_filter(struct perf_event *event, int event_id,
 621                                      char *filter_str);
 622 extern void ftrace_profile_free_filter(struct perf_event *event);
 623 extern void *perf_trace_buf_prepare(int size, unsigned short type,
 624                                     struct pt_regs *regs, int *rctxp);
 625
 626 static inline void
 627 perf_trace_buf_submit(void *raw_data, int size, int rctx, u64 addr,
 628                        u64 count, struct pt_regs *regs, void *head,
 629                        struct task_struct *task)
 630 {
 631         perf_tp_event(addr, count, raw_data, size, regs, head, rctx, task);
 632 }
 633 #endif
 634
 635 #endif /* _LINUX_FTRACE_EVENT_H */