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   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/vmalloc.h>
  25 #include <linux/errno.h>
  26
  27 #include "event_buffer.h"
  28 #include "cpu_buffer.h"
  29 #include "buffer_sync.h"
  30 #include "oprof.h"
  31
  32 #define OP_BUFFER_FLAGS 0
  33
  34 /*
  35  * Read and write access is using spin locking. Thus, writing to the
  36  * buffer by NMI handler (x86) could occur also during critical
  37  * sections when reading the buffer. To avoid this, there are 2
  38  * buffers for independent read and write access. Read access is in
  39  * process context only, write access only in the NMI handler. If the
  40  * read buffer runs empty, both buffers are swapped atomically. There
  41  * is potentially a small window during swapping where the buffers are
  42  * disabled and samples could be lost.
  43  *
  44  * Using 2 buffers is a little bit overhead, but the solution is clear
  45  * and does not require changes in the ring buffer implementation. It
  46  * can be changed to a single buffer solution when the ring buffer
  47  * access is implemented as non-locking atomic code.
  48  */
  49 static struct ring_buffer *op_ring_buffer_read;
  50 static struct ring_buffer *op_ring_buffer_write;
  51 DEFINE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer);
  52
  53 static void wq_sync_buffer(struct work_struct *work);
  54
  55 #define DEFAULT_TIMER_EXPIRE (HZ / 10)
  56 static int work_enabled;
  57
  58 unsigned long oprofile_get_cpu_buffer_size(void)
  59 {
  60         return oprofile_cpu_buffer_size;
  61 }
  62
  63 void oprofile_cpu_buffer_inc_smpl_lost(void)
  64 {
  65         struct oprofile_cpu_buffer *cpu_buf
  66                 = &__get_cpu_var(cpu_buffer);
  67
  68         cpu_buf->sample_lost_overflow++;
  69 }
  70
  71 void free_cpu_buffers(void)
  72 {
  73         if (op_ring_buffer_read)
  74                 ring_buffer_free(op_ring_buffer_read);
  75         op_ring_buffer_read = NULL;
  76         if (op_ring_buffer_write)
  77                 ring_buffer_free(op_ring_buffer_write);
  78         op_ring_buffer_write = NULL;
  79 }
  80
  81 int alloc_cpu_buffers(void)
  82 {
  83         int i;
  84
  85         unsigned long buffer_size = oprofile_cpu_buffer_size;
  86
  87         op_ring_buffer_read = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
  88         if (!op_ring_buffer_read)
  89                 goto fail;
  90         op_ring_buffer_write = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
  91         if (!op_ring_buffer_write)
  92                 goto fail;
  93
  94         for_each_possible_cpu(i) {
  95                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
  96
  97                 b->last_task = NULL;
  98                 b->last_is_kernel = -1;
  99                 b->tracing = 0;
 100                 b->buffer_size = buffer_size;
 101                 b->sample_received = 0;
 102                 b->sample_lost_overflow = 0;
 103                 b->backtrace_aborted = 0;
 104                 b->sample_invalid_eip = 0;
 105                 b->cpu = i;
 106                 INIT_DELAYED_WORK(&b->work, wq_sync_buffer);
 107         }
 108         return 0;
 109
 110 fail:
 111         free_cpu_buffers();
 112         return -ENOMEM;
 113 }
 114
 115 void start_cpu_work(void)
 116 {
 117         int i;
 118
 119         work_enabled = 1;
 120
 121         for_each_online_cpu(i) {
 122                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
 123
 124                 /*
 125                  * Spread the work by 1 jiffy per cpu so they dont all
 126                  * fire at once.
 127                  */
 128                 schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i);
 129         }
 130 }
 131
 132 void end_cpu_work(void)
 133 {
 134         int i;
 135
 136         work_enabled = 0;
 137
 138         for_each_online_cpu(i) {
 139                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
 140
 141                 cancel_delayed_work(&b->work);
 142         }
 143
 144         flush_scheduled_work();
 145 }
 146
 147 /*
 148  * This function prepares the cpu buffer to write a sample.
 149  *
 150  * Struct op_entry is used during operations on the ring buffer while
 151  * struct op_sample contains the data that is stored in the ring
 152  * buffer. Struct entry can be uninitialized. The function reserves a
 153  * data array that is specified by size. Use
 154  * op_cpu_buffer_write_commit() after preparing the sample. In case of
 155  * errors a null pointer is returned, otherwise the pointer to the
 156  * sample.
 157  *
 158  */
 159 struct op_sample
 160 *op_cpu_buffer_write_reserve(struct op_entry *entry, unsigned long size)
 161 {
 162         entry->event = ring_buffer_lock_reserve
 163                 (op_ring_buffer_write, sizeof(struct op_sample) +
 164                  size * sizeof(entry->sample->data[0]));
 165         if (entry->event)
 166                 entry->sample = ring_buffer_event_data(entry->event);
 167         else
 168                 entry->sample = NULL;
 169
 170         if (!entry->sample)
 171                 return NULL;
 172
 173         entry->size = size;
 174         entry->data = entry->sample->data;
 175
 176         return entry->sample;
 177 }
 178
 179 int op_cpu_buffer_write_commit(struct op_entry *entry)
 180 {
 181         return ring_buffer_unlock_commit(op_ring_buffer_write, entry->event);
 182 }
 183
 184 struct op_sample *op_cpu_buffer_read_entry(struct op_entry *entry, int cpu)
 185 {
 186         struct ring_buffer_event *e;
 187         e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
 188         if (e)
 189                 goto event;
 190         if (ring_buffer_swap_cpu(op_ring_buffer_read,
 191                                  op_ring_buffer_write,
 192                                  cpu))
 193                 return NULL;
 194         e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
 195         if (e)
 196                 goto event;
 197         return NULL;
 198
 199 event:
 200         entry->event = e;
 201         entry->sample = ring_buffer_event_data(e);
 202         entry->size = (ring_buffer_event_length(e) - sizeof(struct op_sample))
 203                 / sizeof(entry->sample->data[0]);
 204         entry->data = entry->sample->data;
 205         return entry->sample;
 206 }
 207
 208 unsigned long op_cpu_buffer_entries(int cpu)
 209 {
 210         return ring_buffer_entries_cpu(op_ring_buffer_read, cpu)
 211                 + ring_buffer_entries_cpu(op_ring_buffer_write, cpu);
 212 }
 213
 214 static int
 215 op_add_code(struct oprofile_cpu_buffer *cpu_buf, unsigned long backtrace,
 216             int is_kernel, struct task_struct *task)
 217 {
 218         struct op_entry entry;
 219         struct op_sample *sample;
 220         unsigned long flags;
 221         int size;
 222
 223         flags = 0;
 224
 225         if (backtrace)
 226                 flags |= TRACE_BEGIN;
 227
 228         /* notice a switch from user->kernel or vice versa */
 229         is_kernel = !!is_kernel;
 230         if (cpu_buf->last_is_kernel != is_kernel) {
 231                 cpu_buf->last_is_kernel = is_kernel;
 232                 flags |= KERNEL_CTX_SWITCH;
 233                 if (is_kernel)
 234                         flags |= IS_KERNEL;
 235         }
 236
 237         /* notice a task switch */
 238         if (cpu_buf->last_task != task) {
 239                 cpu_buf->last_task = task;
 240                 flags |= USER_CTX_SWITCH;
 241         }
 242
 243         if (!flags)
 244                 /* nothing to do */
 245                 return 0;
 246
 247         if (flags & USER_CTX_SWITCH)
 248                 size = 1;
 249         else
 250                 size = 0;
 251
 252         sample = op_cpu_buffer_write_reserve(&entry, size);
 253         if (!sample)
 254                 return -ENOMEM;
 255
 256         sample->eip = ESCAPE_CODE;
 257         sample->event = flags;
 258
 259         if (size)
 260                 op_cpu_buffer_add_data(&entry, (unsigned long)task);
 261
 262         op_cpu_buffer_write_commit(&entry);
 263
 264         return 0;
 265 }
 266
 267 static inline int
 268 op_add_sample(struct oprofile_cpu_buffer *cpu_buf,
 269               unsigned long pc, unsigned long event)
 270 {
 271         struct op_entry entry;
 272         struct op_sample *sample;
 273
 274         sample = op_cpu_buffer_write_reserve(&entry, 0);
 275         if (!sample)
 276                 return -ENOMEM;
 277
 278         sample->eip = pc;
 279         sample->event = event;
 280
 281         return op_cpu_buffer_write_commit(&entry);
 282 }
 283
 284 /*
 285  * This must be safe from any context.
 286  *
 287  * is_kernel is needed because on some architectures you cannot
 288  * tell if you are in kernel or user space simply by looking at
 289  * pc. We tag this in the buffer by generating kernel enter/exit
 290  * events whenever is_kernel changes
 291  */
 292 static int
 293 log_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc,
 294            unsigned long backtrace, int is_kernel, unsigned long event)
 295 {
 296         cpu_buf->sample_received++;
 297
 298         if (pc == ESCAPE_CODE) {
 299                 cpu_buf->sample_invalid_eip++;
 300                 return 0;
 301         }
 302
 303         if (op_add_code(cpu_buf, backtrace, is_kernel, current))
 304                 goto fail;
 305
 306         if (op_add_sample(cpu_buf, pc, event))
 307                 goto fail;
 308
 309         return 1;
 310
 311 fail:
 312         cpu_buf->sample_lost_overflow++;
 313         return 0;
 314 }
 315
 316 static inline void oprofile_begin_trace(struct oprofile_cpu_buffer *cpu_buf)
 317 {
 318         cpu_buf->tracing = 1;
 319 }
 320
 321 static inline void oprofile_end_trace(struct oprofile_cpu_buffer *cpu_buf)
 322 {
 323         cpu_buf->tracing = 0;
 324 }
 325
 326 static inline void
 327 __oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
 328                           unsigned long event, int is_kernel)
 329 {
 330         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
 331         unsigned long backtrace = oprofile_backtrace_depth;
 332
 333         /*
 334          * if log_sample() fail we can't backtrace since we lost the
 335          * source of this event
 336          */
 337         if (!log_sample(cpu_buf, pc, backtrace, is_kernel, event))
 338                 /* failed */
 339                 return;
 340
 341         if (!backtrace)
 342                 return;
 343
 344         oprofile_begin_trace(cpu_buf);
 345         oprofile_ops.backtrace(regs, backtrace);
 346         oprofile_end_trace(cpu_buf);
 347 }
 348
 349 void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
 350                              unsigned long event, int is_kernel)
 351 {
 352         __oprofile_add_ext_sample(pc, regs, event, is_kernel);
 353 }
 354
 355 void oprofile_add_sample(struct pt_regs * const regs, unsigned long event)
 356 {
 357         int is_kernel = !user_mode(regs);
 358         unsigned long pc = profile_pc(regs);
 359
 360         __oprofile_add_ext_sample(pc, regs, event, is_kernel);
 361 }
 362
 363 /*
 364  * Add samples with data to the ring buffer.
 365  *
 366  * Use oprofile_add_data(&entry, val) to add data and
 367  * oprofile_write_commit(&entry) to commit the sample.
 368  */
 369 void
 370 oprofile_write_reserve(struct op_entry *entry, struct pt_regs * const regs,
 371                        unsigned long pc, int code, int size)
 372 {
 373         struct op_sample *sample;
 374         int is_kernel = !user_mode(regs);
 375         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
 376
 377         cpu_buf->sample_received++;
 378
 379         /* no backtraces for samples with data */
 380         if (op_add_code(cpu_buf, 0, is_kernel, current))
 381                 goto fail;
 382
 383         sample = op_cpu_buffer_write_reserve(entry, size + 2);
 384         if (!sample)
 385                 goto fail;
 386         sample->eip = ESCAPE_CODE;
 387         sample->event = 0;              /* no flags */
 388
 389         op_cpu_buffer_add_data(entry, code);
 390         op_cpu_buffer_add_data(entry, pc);
 391
 392         return;
 393
 394 fail:
 395         entry->event = NULL;
 396         cpu_buf->sample_lost_overflow++;
 397 }
 398
 399 int oprofile_add_data(struct op_entry *entry, unsigned long val)
 400 {
 401         if (!entry->event)
 402                 return 0;
 403         return op_cpu_buffer_add_data(entry, val);
 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 = &__get_cpu_var(cpu_buffer);
 416         log_sample(cpu_buf, pc, 0, is_kernel, event);
 417 }
 418
 419 void oprofile_add_trace(unsigned long pc)
 420 {
 421         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(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()) {
 455                 printk(KERN_DEBUG "WQ on CPU%d, prefer CPU%d\n",
 456                        smp_processor_id(), b->cpu);
 457
 458                 if (!cpu_online(b->cpu)) {
 459                         cancel_delayed_work(&b->work);
 460                         return;
 461                 }
 462         }
 463         sync_buffer(b->cpu);
 464
 465         /* don't re-add the work if we're shutting down */
 466         if (work_enabled)
 467                 schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE);
 468 }