drivers/oprofile/cpu_buffer.c

   1 /**
   2  * @file cpu_buffer.c
   3  *
   4  * @remark Copyright 2002-2009 OProfile authors
   5  * @remark Read the file COPYING
   6  *
   7  * @author John Levon <levon@movementarian.org>
   8  * @author Barry Kasindorf <barry.kasindorf@amd.com>
   9  * @author Robert Richter <robert.richter@amd.com>
  10  *
  11  * Each CPU has a local buffer that stores PC value/event
  12  * pairs. We also log context switches when we notice them.
  13  * Eventually each CPU's buffer is processed into the global
  14  * event buffer by sync_buffer().
  15  *
  16  * We use a local buffer for two reasons: an NMI or similar
  17  * interrupt cannot synchronise, and high sampling rates
  18  * would lead to catastrophic global synchronisation if
  19  * a global buffer was used.
  20  */
  21
  22 #include <linux/sched.h>
  23 #include <linux/oprofile.h>
  24 #include <linux/errno.h>
  25
  26 #include "event_buffer.h"
  27 #include "cpu_buffer.h"
  28 #include "buffer_sync.h"
  29 #include "oprof.h"
  30
  31 #define OP_BUFFER_FLAGS 0
  32
  33 static struct ring_buffer *op_ring_buffer;
  34 DEFINE_PER_CPU(struct oprofile_cpu_buffer, op_cpu_buffer);
  35
  36 static void wq_sync_buffer(struct work_struct *work);
  37
  38 #define DEFAULT_TIMER_EXPIRE (HZ / 10)
  39 static int work_enabled;
  40
  41 unsigned long oprofile_get_cpu_buffer_size(void)
  42 {
  43         return oprofile_cpu_buffer_size;
  44 }
  45
  46 void oprofile_cpu_buffer_inc_smpl_lost(void)
  47 {
  48         struct oprofile_cpu_buffer *cpu_buf = this_cpu_ptr(&op_cpu_buffer);
  49
  50         cpu_buf->sample_lost_overflow++;
  51 }
  52
  53 void free_cpu_buffers(void)
  54 {
  55         if (op_ring_buffer)
  56                 ring_buffer_free(op_ring_buffer);
  57         op_ring_buffer = NULL;
  58 }
  59
  60 #define RB_EVENT_HDR_SIZE 4
  61
  62 int alloc_cpu_buffers(void)
  63 {
  64         int i;
  65
  66         unsigned long buffer_size = oprofile_cpu_buffer_size;
  67         unsigned long byte_size = buffer_size * (sizeof(struct op_sample) +
  68                                                  RB_EVENT_HDR_SIZE);
  69
  70         op_ring_buffer = ring_buffer_alloc(byte_size, OP_BUFFER_FLAGS);
  71         if (!op_ring_buffer)
  72                 goto fail;
  73
  74         for_each_possible_cpu(i) {
  75                 struct oprofile_cpu_buffer *b = &per_cpu(op_cpu_buffer, i);
  76
  77                 b->last_task = NULL;
  78                 b->last_is_kernel = -1;
  79                 b->tracing = 0;
  80                 b->buffer_size = buffer_size;
  81                 b->sample_received = 0;
  82                 b->sample_lost_overflow = 0;
  83                 b->backtrace_aborted = 0;
  84                 b->sample_invalid_eip = 0;
  85                 b->cpu = i;
  86                 INIT_DELAYED_WORK(&b->work, wq_sync_buffer);
  87         }
  88         return 0;
  89
  90 fail:
  91         free_cpu_buffers();
  92         return -ENOMEM;
  93 }
  94
  95 void start_cpu_work(void)
  96 {
  97         int i;
  98
  99         work_enabled = 1;
 100
 101         for_each_online_cpu(i) {
 102                 struct oprofile_cpu_buffer *b = &per_cpu(op_cpu_buffer, i);
 103
 104                 /*
 105                  * Spread the work by 1 jiffy per cpu so they dont all
 106                  * fire at once.
 107                  */
 108                 schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i);
 109         }
 110 }
 111
 112 void end_cpu_work(void)
 113 {
 114         work_enabled = 0;
 115 }
 116
 117 void flush_cpu_work(void)
 118 {
 119         int i;
 120
 121         for_each_online_cpu(i) {
 122                 struct oprofile_cpu_buffer *b = &per_cpu(op_cpu_buffer, i);
 123
 124                 /* these works are per-cpu, no need for flush_sync */
 125                 flush_delayed_work(&b->work);
 126         }
 127 }
 128
 129 /*
 130  * This function prepares the cpu buffer to write a sample.
 131  *
 132  * Struct op_entry is used during operations on the ring buffer while
 133  * struct op_sample contains the data that is stored in the ring
 134  * buffer. Struct entry can be uninitialized. The function reserves a
 135  * data array that is specified by size. Use
 136  * op_cpu_buffer_write_commit() after preparing the sample. In case of
 137  * errors a null pointer is returned, otherwise the pointer to the
 138  * sample.
 139  *
 140  */
 141 struct op_sample
 142 *op_cpu_buffer_write_reserve(struct op_entry *entry, unsigned long size)
 143 {
 144         entry->event = ring_buffer_lock_reserve
 145                 (op_ring_buffer, sizeof(struct op_sample) +
 146                  size * sizeof(entry->sample->data[0]));
 147         if (!entry->event)
 148                 return NULL;
 149         entry->sample = ring_buffer_event_data(entry->event);
 150         entry->size = size;
 151         entry->data = entry->sample->data;
 152
 153         return entry->sample;
 154 }
 155
 156 int op_cpu_buffer_write_commit(struct op_entry *entry)
 157 {
 158         return ring_buffer_unlock_commit(op_ring_buffer, entry->event);
 159 }
 160
 161 struct op_sample *op_cpu_buffer_read_entry(struct op_entry *entry, int cpu)
 162 {
 163         struct ring_buffer_event *e;
 164         e = ring_buffer_consume(op_ring_buffer, cpu, NULL, NULL);
 165         if (!e)
 166                 return NULL;
 167
 168         entry->event = e;
 169         entry->sample = ring_buffer_event_data(e);
 170         entry->size = (ring_buffer_event_length(e) - sizeof(struct op_sample))
 171                 / sizeof(entry->sample->data[0]);
 172         entry->data = entry->sample->data;
 173         return entry->sample;
 174 }
 175
 176 unsigned long op_cpu_buffer_entries(int cpu)
 177 {
 178         return ring_buffer_entries_cpu(op_ring_buffer, cpu);
 179 }
 180
 181 static int
 182 op_add_code(struct oprofile_cpu_buffer *cpu_buf, unsigned long backtrace,
 183             int is_kernel, struct task_struct *task)
 184 {
 185         struct op_entry entry;
 186         struct op_sample *sample;
 187         unsigned long flags;
 188         int size;
 189
 190         flags = 0;
 191
 192         if (backtrace)
 193                 flags |= TRACE_BEGIN;
 194
 195         /* notice a switch from user->kernel or vice versa */
 196         is_kernel = !!is_kernel;
 197         if (cpu_buf->last_is_kernel != is_kernel) {
 198                 cpu_buf->last_is_kernel = is_kernel;
 199                 flags |= KERNEL_CTX_SWITCH;
 200                 if (is_kernel)
 201                         flags |= IS_KERNEL;
 202         }
 203
 204         /* notice a task switch */
 205         if (cpu_buf->last_task != task) {
 206                 cpu_buf->last_task = task;
 207                 flags |= USER_CTX_SWITCH;
 208         }
 209
 210         if (!flags)
 211                 /* nothing to do */
 212                 return 0;
 213
 214         if (flags & USER_CTX_SWITCH)
 215                 size = 1;
 216         else
 217                 size = 0;
 218
 219         sample = op_cpu_buffer_write_reserve(&entry, size);
 220         if (!sample)
 221                 return -ENOMEM;
 222
 223         sample->eip = ESCAPE_CODE;
 224         sample->event = flags;
 225
 226         if (size)
 227                 op_cpu_buffer_add_data(&entry, (unsigned long)task);
 228
 229         op_cpu_buffer_write_commit(&entry);
 230
 231         return 0;
 232 }
 233
 234 static inline int
 235 op_add_sample(struct oprofile_cpu_buffer *cpu_buf,
 236               unsigned long pc, unsigned long event)
 237 {
 238         struct op_entry entry;
 239         struct op_sample *sample;
 240
 241         sample = op_cpu_buffer_write_reserve(&entry, 0);
 242         if (!sample)
 243                 return -ENOMEM;
 244
 245         sample->eip = pc;
 246         sample->event = event;
 247
 248         return op_cpu_buffer_write_commit(&entry);
 249 }
 250
 251 /*
 252  * This must be safe from any context.
 253  *
 254  * is_kernel is needed because on some architectures you cannot
 255  * tell if you are in kernel or user space simply by looking at
 256  * pc. We tag this in the buffer by generating kernel enter/exit
 257  * events whenever is_kernel changes
 258  */
 259 static int
 260 log_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc,
 261            unsigned long backtrace, int is_kernel, unsigned long event,
 262            struct task_struct *task)
 263 {
 264         struct task_struct *tsk = task ? task : current;
 265         cpu_buf->sample_received++;
 266
 267         if (pc == ESCAPE_CODE) {
 268                 cpu_buf->sample_invalid_eip++;
 269                 return 0;
 270         }
 271
 272         if (op_add_code(cpu_buf, backtrace, is_kernel, tsk))
 273                 goto fail;
 274
 275         if (op_add_sample(cpu_buf, pc, event))
 276                 goto fail;
 277
 278         return 1;
 279
 280 fail:
 281         cpu_buf->sample_lost_overflow++;
 282         return 0;
 283 }
 284
 285 static inline void oprofile_begin_trace(struct oprofile_cpu_buffer *cpu_buf)
 286 {
 287         cpu_buf->tracing = 1;
 288 }
 289
 290 static inline void oprofile_end_trace(struct oprofile_cpu_buffer *cpu_buf)
 291 {
 292         cpu_buf->tracing = 0;
 293 }
 294
 295 static inline void
 296 __oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
 297                           unsigned long event, int is_kernel,
 298                           struct task_struct *task)
 299 {
 300         struct oprofile_cpu_buffer *cpu_buf = this_cpu_ptr(&op_cpu_buffer);
 301         unsigned long backtrace = oprofile_backtrace_depth;
 302
 303         /*
 304          * if log_sample() fail we can't backtrace since we lost the
 305          * source of this event
 306          */
 307         if (!log_sample(cpu_buf, pc, backtrace, is_kernel, event, task))
 308                 /* failed */
 309                 return;
 310
 311         if (!backtrace)
 312                 return;
 313
 314         oprofile_begin_trace(cpu_buf);
 315         oprofile_ops.backtrace(regs, backtrace);
 316         oprofile_end_trace(cpu_buf);
 317 }
 318
 319 void oprofile_add_ext_hw_sample(unsigned long pc, struct pt_regs * const regs,
 320                                 unsigned long event, int is_kernel,
 321                                 struct task_struct *task)
 322 {
 323         __oprofile_add_ext_sample(pc, regs, event, is_kernel, task);
 324 }
 325
 326 void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
 327                              unsigned long event, int is_kernel)
 328 {
 329         __oprofile_add_ext_sample(pc, regs, event, is_kernel, NULL);
 330 }
 331
 332 void oprofile_add_sample(struct pt_regs * const regs, unsigned long event)
 333 {
 334         int is_kernel;
 335         unsigned long pc;
 336
 337         if (likely(regs)) {
 338                 is_kernel = !user_mode(regs);
 339                 pc = profile_pc(regs);
 340         } else {
 341                 is_kernel = 0;    /* This value will not be used */
 342                 pc = ESCAPE_CODE; /* as this causes an early return. */
 343         }
 344
 345         __oprofile_add_ext_sample(pc, regs, event, is_kernel, NULL);
 346 }
 347
 348 /*
 349  * Add samples with data to the ring buffer.
 350  *
 351  * Use oprofile_add_data(&entry, val) to add data and
 352  * oprofile_write_commit(&entry) to commit the sample.
 353  */
 354 void
 355 oprofile_write_reserve(struct op_entry *entry, struct pt_regs * const regs,
 356                        unsigned long pc, int code, int size)
 357 {
 358         struct op_sample *sample;
 359         int is_kernel = !user_mode(regs);
 360         struct oprofile_cpu_buffer *cpu_buf = this_cpu_ptr(&op_cpu_buffer);
 361
 362         cpu_buf->sample_received++;
 363
 364         /* no backtraces for samples with data */
 365         if (op_add_code(cpu_buf, 0, is_kernel, current))
 366                 goto fail;
 367
 368         sample = op_cpu_buffer_write_reserve(entry, size + 2);
 369         if (!sample)
 370                 goto fail;
 371         sample->eip = ESCAPE_CODE;
 372         sample->event = 0;              /* no flags */
 373
 374         op_cpu_buffer_add_data(entry, code);
 375         op_cpu_buffer_add_data(entry, pc);
 376
 377         return;
 378
 379 fail:
 380         entry->event = NULL;
 381         cpu_buf->sample_lost_overflow++;
 382 }
 383
 384 int oprofile_add_data(struct op_entry *entry, unsigned long val)
 385 {
 386         if (!entry->event)
 387                 return 0;
 388         return op_cpu_buffer_add_data(entry, val);
 389 }
 390
 391 int oprofile_add_data64(struct op_entry *entry, u64 val)
 392 {
 393         if (!entry->event)
 394                 return 0;
 395         if (op_cpu_buffer_get_size(entry) < 2)
 396                 /*
 397                  * the function returns 0 to indicate a too small
 398                  * buffer, even if there is some space left
 399                  */
 400                 return 0;
 401         if (!op_cpu_buffer_add_data(entry, (u32)val))
 402                 return 0;
 403         return op_cpu_buffer_add_data(entry, (u32)(val >> 32));
 404 }
 405
 406 int oprofile_write_commit(struct op_entry *entry)
 407 {
 408         if (!entry->event)
 409                 return -EINVAL;
 410         return op_cpu_buffer_write_commit(entry);
 411 }
 412
 413 void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event)
 414 {
 415         struct oprofile_cpu_buffer *cpu_buf = this_cpu_ptr(&op_cpu_buffer);
 416         log_sample(cpu_buf, pc, 0, is_kernel, event, NULL);
 417 }
 418
 419 void oprofile_add_trace(unsigned long pc)
 420 {
 421         struct oprofile_cpu_buffer *cpu_buf = this_cpu_ptr(&op_cpu_buffer);
 422
 423         if (!cpu_buf->tracing)
 424                 return;
 425
 426         /*
 427          * broken frame can give an eip with the same value as an
 428          * escape code, abort the trace if we get it
 429          */
 430         if (pc == ESCAPE_CODE)
 431                 goto fail;
 432
 433         if (op_add_sample(cpu_buf, pc, 0))
 434                 goto fail;
 435
 436         return;
 437 fail:
 438         cpu_buf->tracing = 0;
 439         cpu_buf->backtrace_aborted++;
 440         return;
 441 }
 442
 443 /*
 444  * This serves to avoid cpu buffer overflow, and makes sure
 445  * the task mortuary progresses
 446  *
 447  * By using schedule_delayed_work_on and then schedule_delayed_work
 448  * we guarantee this will stay on the correct cpu
 449  */
 450 static void wq_sync_buffer(struct work_struct *work)
 451 {
 452         struct oprofile_cpu_buffer *b =
 453                 container_of(work, struct oprofile_cpu_buffer, work.work);
 454         if (b->cpu != smp_processor_id() && !cpu_online(b->cpu)) {
 455                 cancel_delayed_work(&b->work);
 456                 return;
 457         }
 458         sync_buffer(b->cpu);
 459
 460         /* don't re-add the work if we're shutting down */
 461         if (work_enabled)
 462                 schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE);
 463 }