arch/x86/kernel/ds.c

   1 /*
   2  * Debug Store support
   3  *
   4  * This provides a low-level interface to the hardware's Debug Store
   5  * feature that is used for branch trace store (BTS) and
   6  * precise-event based sampling (PEBS).
   7  *
   8  * It manages:
   9  * - per-thread and per-cpu allocation of BTS and PEBS
  10  * - buffer memory allocation (optional)
  11  * - buffer overflow handling
  12  * - buffer access
  13  *
  14  * It assumes:
  15  * - get_task_struct on all parameter tasks
  16  * - current is allowed to trace parameter tasks
  17  *
  18  *
  19  * Copyright (C) 2007-2008 Intel Corporation.
  20  * Markus Metzger <markus.t.metzger@intel.com>, 2007-2008
  21  */
  22
  23
  24 #ifdef CONFIG_X86_DS
  25
  26 #include <asm/ds.h>
  27
  28 #include <linux/errno.h>
  29 #include <linux/string.h>
  30 #include <linux/slab.h>
  31 #include <linux/sched.h>
  32 #include <linux/mm.h>
  33
  34
  35 /*
  36  * The configuration for a particular DS hardware implementation.
  37  */
  38 struct ds_configuration {
  39         /* the size of the DS structure in bytes */
  40         unsigned char  sizeof_ds;
  41         /* the size of one pointer-typed field in the DS structure in bytes;
  42            this covers the first 8 fields related to buffer management. */
  43         unsigned char  sizeof_field;
  44         /* the size of a BTS/PEBS record in bytes */
  45         unsigned char  sizeof_rec[2];
  46 };
  47 static struct ds_configuration ds_cfg;
  48
  49
  50 /*
  51  * Debug Store (DS) save area configuration (see Intel64 and IA32
  52  * Architectures Software Developer's Manual, section 18.5)
  53  *
  54  * The DS configuration consists of the following fields; different
  55  * architetures vary in the size of those fields.
  56  * - double-word aligned base linear address of the BTS buffer
  57  * - write pointer into the BTS buffer
  58  * - end linear address of the BTS buffer (one byte beyond the end of
  59  *   the buffer)
  60  * - interrupt pointer into BTS buffer
  61  *   (interrupt occurs when write pointer passes interrupt pointer)
  62  * - double-word aligned base linear address of the PEBS buffer
  63  * - write pointer into the PEBS buffer
  64  * - end linear address of the PEBS buffer (one byte beyond the end of
  65  *   the buffer)
  66  * - interrupt pointer into PEBS buffer
  67  *   (interrupt occurs when write pointer passes interrupt pointer)
  68  * - value to which counter is reset following counter overflow
  69  *
  70  * Later architectures use 64bit pointers throughout, whereas earlier
  71  * architectures use 32bit pointers in 32bit mode.
  72  *
  73  *
  74  * We compute the base address for the first 8 fields based on:
  75  * - the field size stored in the DS configuration
  76  * - the relative field position
  77  * - an offset giving the start of the respective region
  78  *
  79  * This offset is further used to index various arrays holding
  80  * information for BTS and PEBS at the respective index.
  81  *
  82  * On later 32bit processors, we only access the lower 32bit of the
  83  * 64bit pointer fields. The upper halves will be zeroed out.
  84  */
  85
  86 enum ds_field {
  87         ds_buffer_base = 0,
  88         ds_index,
  89         ds_absolute_maximum,
  90         ds_interrupt_threshold,
  91 };
  92
  93 enum ds_qualifier {
  94         ds_bts  = 0,
  95         ds_pebs
  96 };
  97
  98 static inline unsigned long ds_get(const unsigned char *base,
  99                                    enum ds_qualifier qual, enum ds_field field)
 100 {
 101         base += (ds_cfg.sizeof_field * (field + (4 * qual)));
 102         return *(unsigned long *)base;
 103 }
 104
 105 static inline void ds_set(unsigned char *base, enum ds_qualifier qual,
 106                           enum ds_field field, unsigned long value)
 107 {
 108         base += (ds_cfg.sizeof_field * (field + (4 * qual)));
 109         (*(unsigned long *)base) = value;
 110 }
 111
 112
 113 /*
 114  * Locking is done only for allocating BTS or PEBS resources and for
 115  * guarding context and buffer memory allocation.
 116  *
 117  * Most functions require the current task to own the ds context part
 118  * they are going to access. All the locking is done when validating
 119  * access to the context.
 120  */
 121 static spinlock_t ds_lock = __SPIN_LOCK_UNLOCKED(ds_lock);
 122
 123 /*
 124  * Validate that the current task is allowed to access the BTS/PEBS
 125  * buffer of the parameter task.
 126  *
 127  * Returns 0, if access is granted; -Eerrno, otherwise.
 128  */
 129 static inline int ds_validate_access(struct ds_context *context,
 130                                      enum ds_qualifier qual)
 131 {
 132         if (!context)
 133                 return -EPERM;
 134
 135         if (context->owner[qual] == current)
 136                 return 0;
 137
 138         return -EPERM;
 139 }
 140
 141
 142 /*
 143  * We either support (system-wide) per-cpu or per-thread allocation.
 144  * We distinguish the two based on the task_struct pointer, where a
 145  * NULL pointer indicates per-cpu allocation for the current cpu.
 146  *
 147  * Allocations are use-counted. As soon as resources are allocated,
 148  * further allocations must be of the same type (per-cpu or
 149  * per-thread). We model this by counting allocations (i.e. the number
 150  * of tracers of a certain type) for one type negatively:
 151  *   =0  no tracers
 152  *   >0  number of per-thread tracers
 153  *   <0  number of per-cpu tracers
 154  *
 155  * The below functions to get and put tracers and to check the
 156  * allocation type require the ds_lock to be held by the caller.
 157  *
 158  * Tracers essentially gives the number of ds contexts for a certain
 159  * type of allocation.
 160  */
 161 static long tracers;
 162
 163 static inline void get_tracer(struct task_struct *task)
 164 {
 165         tracers += (task ? 1 : -1);
 166 }
 167
 168 static inline void put_tracer(struct task_struct *task)
 169 {
 170         tracers -= (task ? 1 : -1);
 171 }
 172
 173 static inline int check_tracer(struct task_struct *task)
 174 {
 175         return (task ? (tracers >= 0) : (tracers <= 0));
 176 }
 177
 178
 179 /*
 180  * The DS context is either attached to a thread or to a cpu:
 181  * - in the former case, the thread_struct contains a pointer to the
 182  *   attached context.
 183  * - in the latter case, we use a static array of per-cpu context
 184  *   pointers.
 185  *
 186  * Contexts are use-counted. They are allocated on first access and
 187  * deallocated when the last user puts the context.
 188  *
 189  * We distinguish between an allocating and a non-allocating get of a
 190  * context:
 191  * - the allocating get is used for requesting BTS/PEBS resources. It
 192  *   requires the caller to hold the global ds_lock.
 193  * - the non-allocating get is used for all other cases. A
 194  *   non-existing context indicates an error. It acquires and releases
 195  *   the ds_lock itself for obtaining the context.
 196  *
 197  * A context and its DS configuration are allocated and deallocated
 198  * together. A context always has a DS configuration of the
 199  * appropriate size.
 200  */
 201 static DEFINE_PER_CPU(struct ds_context *, system_context);
 202
 203 #define this_system_context per_cpu(system_context, smp_processor_id())
 204
 205 /*
 206  * Returns the pointer to the parameter task's context or to the
 207  * system-wide context, if task is NULL.
 208  *
 209  * Increases the use count of the returned context, if not NULL.
 210  */
 211 static inline struct ds_context *ds_get_context(struct task_struct *task)
 212 {
 213         struct ds_context *context;
 214
 215         spin_lock(&ds_lock);
 216
 217         context = (task ? task->thread.ds_ctx : this_system_context);
 218         if (context)
 219                 context->count++;
 220
 221         spin_unlock(&ds_lock);
 222
 223         return context;
 224 }
 225
 226 /*
 227  * Same as ds_get_context, but allocates the context and it's DS
 228  * structure, if necessary; returns NULL; if out of memory.
 229  *
 230  * pre: requires ds_lock to be held
 231  */
 232 static inline struct ds_context *ds_alloc_context(struct task_struct *task)
 233 {
 234         struct ds_context **p_context =
 235                 (task ? &task->thread.ds_ctx : &this_system_context);
 236         struct ds_context *context = *p_context;
 237
 238         if (!context) {
 239                 context = kzalloc(sizeof(*context), GFP_KERNEL);
 240
 241                 if (!context)
 242                         return NULL;
 243
 244                 context->ds = kzalloc(ds_cfg.sizeof_ds, GFP_KERNEL);
 245                 if (!context->ds) {
 246                         kfree(context);
 247                         return NULL;
 248                 }
 249
 250                 *p_context = context;
 251
 252                 context->this = p_context;
 253                 context->task = task;
 254
 255                 if (task)
 256                         set_tsk_thread_flag(task, TIF_DS_AREA_MSR);
 257
 258                 if (!task || (task == current))
 259                         wrmsr(MSR_IA32_DS_AREA, (unsigned long)context->ds, 0);
 260
 261                 get_tracer(task);
 262         }
 263
 264         context->count++;
 265
 266         return context;
 267 }
 268
 269 /*
 270  * Decreases the use count of the parameter context, if not NULL.
 271  * Deallocates the context, if the use count reaches zero.
 272  */
 273 static inline void ds_put_context(struct ds_context *context)
 274 {
 275         if (!context)
 276                 return;
 277
 278         spin_lock(&ds_lock);
 279
 280         if (--context->count)
 281                 goto out;
 282
 283         *(context->this) = NULL;
 284
 285         if (context->task)
 286                 clear_tsk_thread_flag(context->task, TIF_DS_AREA_MSR);
 287
 288         if (!context->task || (context->task == current))
 289                 wrmsrl(MSR_IA32_DS_AREA, 0);
 290
 291         put_tracer(context->task);
 292
 293         /* free any leftover buffers from tracers that did not
 294          * deallocate them properly. */
 295         kfree(context->buffer[ds_bts]);
 296         kfree(context->buffer[ds_pebs]);
 297         kfree(context->ds);
 298         kfree(context);
 299  out:
 300         spin_unlock(&ds_lock);
 301 }
 302
 303
 304 /*
 305  * Handle a buffer overflow
 306  *
 307  * task: the task whose buffers are overflowing;
 308  *       NULL for a buffer overflow on the current cpu
 309  * context: the ds context
 310  * qual: the buffer type
 311  */
 312 static void ds_overflow(struct task_struct *task, struct ds_context *context,
 313                         enum ds_qualifier qual)
 314 {
 315         if (!context)
 316                 return;
 317
 318         if (context->callback[qual])
 319                 (*context->callback[qual])(task);
 320
 321         /* todo: do some more overflow handling */
 322 }
 323
 324
 325 /*
 326  * Allocate a non-pageable buffer of the parameter size.
 327  * Checks the memory and the locked memory rlimit.
 328  *
 329  * Returns the buffer, if successful;
 330  *         NULL, if out of memory or rlimit exceeded.
 331  *
 332  * size: the requested buffer size in bytes
 333  * pages (out): if not NULL, contains the number of pages reserved
 334  */
 335 static inline void *ds_allocate_buffer(size_t size, unsigned int *pages)
 336 {
 337         unsigned long rlim, vm, pgsz;
 338         void *buffer;
 339
 340         pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
 341
 342         rlim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
 343         vm   = current->mm->total_vm  + pgsz;
 344         if (rlim < vm)
 345                 return NULL;
 346
 347         rlim = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
 348         vm   = current->mm->locked_vm  + pgsz;
 349         if (rlim < vm)
 350                 return NULL;
 351
 352         buffer = kzalloc(size, GFP_KERNEL);
 353         if (!buffer)
 354                 return NULL;
 355
 356         current->mm->total_vm  += pgsz;
 357         current->mm->locked_vm += pgsz;
 358
 359         if (pages)
 360                 *pages = pgsz;
 361
 362         return buffer;
 363 }
 364
 365 static int ds_request(struct task_struct *task, void *base, size_t size,
 366                       ds_ovfl_callback_t ovfl, enum ds_qualifier qual)
 367 {
 368         struct ds_context *context;
 369         unsigned long buffer, adj;
 370         const unsigned long alignment = (1 << 3);
 371         int error = 0;
 372
 373         if (!ds_cfg.sizeof_ds)
 374                 return -EOPNOTSUPP;
 375
 376         /* we require some space to do alignment adjustments below */
 377         if (size < (alignment + ds_cfg.sizeof_rec[qual]))
 378                 return -EINVAL;
 379
 380         /* buffer overflow notification is not yet implemented */
 381         if (ovfl)
 382                 return -EOPNOTSUPP;
 383
 384
 385         spin_lock(&ds_lock);
 386
 387         if (!check_tracer(task))
 388                 return -EPERM;
 389
 390         error = -ENOMEM;
 391         context = ds_alloc_context(task);
 392         if (!context)
 393                 goto out_unlock;
 394
 395         error = -EALREADY;
 396         if (context->owner[qual] == current)
 397                 goto out_unlock;
 398         error = -EPERM;
 399         if (context->owner[qual] != NULL)
 400                 goto out_unlock;
 401         context->owner[qual] = current;
 402
 403         spin_unlock(&ds_lock);
 404
 405
 406         error = -ENOMEM;
 407         if (!base) {
 408                 base = ds_allocate_buffer(size, &context->pages[qual]);
 409                 if (!base)
 410                         goto out_release;
 411
 412                 context->buffer[qual]   = base;
 413         }
 414         error = 0;
 415
 416         context->callback[qual] = ovfl;
 417
 418         /* adjust the buffer address and size to meet alignment
 419          * constraints:
 420          * - buffer is double-word aligned
 421          * - size is multiple of record size
 422          *
 423          * We checked the size at the very beginning; we have enough
 424          * space to do the adjustment.
 425          */
 426         buffer = (unsigned long)base;
 427
 428         adj = ALIGN(buffer, alignment) - buffer;
 429         buffer += adj;
 430         size   -= adj;
 431
 432         size /= ds_cfg.sizeof_rec[qual];
 433         size *= ds_cfg.sizeof_rec[qual];
 434
 435         ds_set(context->ds, qual, ds_buffer_base, buffer);
 436         ds_set(context->ds, qual, ds_index, buffer);
 437         ds_set(context->ds, qual, ds_absolute_maximum, buffer + size);
 438
 439         if (ovfl) {
 440                 /* todo: select a suitable interrupt threshold */
 441         } else
 442                 ds_set(context->ds, qual,
 443                        ds_interrupt_threshold, buffer + size + 1);
 444
 445         /* we keep the context until ds_release */
 446         return error;
 447
 448  out_release:
 449         context->owner[qual] = NULL;
 450         ds_put_context(context);
 451         return error;
 452
 453  out_unlock:
 454         spin_unlock(&ds_lock);
 455         ds_put_context(context);
 456         return error;
 457 }
 458
 459 int ds_request_bts(struct task_struct *task, void *base, size_t size,
 460                    ds_ovfl_callback_t ovfl)
 461 {
 462         return ds_request(task, base, size, ovfl, ds_bts);
 463 }
 464
 465 int ds_request_pebs(struct task_struct *task, void *base, size_t size,
 466                     ds_ovfl_callback_t ovfl)
 467 {
 468         return ds_request(task, base, size, ovfl, ds_pebs);
 469 }
 470
 471 static int ds_release(struct task_struct *task, enum ds_qualifier qual)
 472 {
 473         struct ds_context *context;
 474         int error;
 475
 476         context = ds_get_context(task);
 477         error = ds_validate_access(context, qual);
 478         if (error < 0)
 479                 goto out;
 480
 481         kfree(context->buffer[qual]);
 482         context->buffer[qual] = NULL;
 483
 484         current->mm->total_vm  -= context->pages[qual];
 485         current->mm->locked_vm -= context->pages[qual];
 486         context->pages[qual] = 0;
 487         context->owner[qual] = NULL;
 488
 489         /*
 490          * we put the context twice:
 491          *   once for the ds_get_context
 492          *   once for the corresponding ds_request
 493          */
 494         ds_put_context(context);
 495  out:
 496         ds_put_context(context);
 497         return error;
 498 }
 499
 500 int ds_release_bts(struct task_struct *task)
 501 {
 502         return ds_release(task, ds_bts);
 503 }
 504
 505 int ds_release_pebs(struct task_struct *task)
 506 {
 507         return ds_release(task, ds_pebs);
 508 }
 509
 510 static int ds_get_index(struct task_struct *task, size_t *pos,
 511                         enum ds_qualifier qual)
 512 {
 513         struct ds_context *context;
 514         unsigned long base, index;
 515         int error;
 516
 517         context = ds_get_context(task);
 518         error = ds_validate_access(context, qual);
 519         if (error < 0)
 520                 goto out;
 521
 522         base  = ds_get(context->ds, qual, ds_buffer_base);
 523         index = ds_get(context->ds, qual, ds_index);
 524
 525         error = ((index - base) / ds_cfg.sizeof_rec[qual]);
 526         if (pos)
 527                 *pos = error;
 528  out:
 529         ds_put_context(context);
 530         return error;
 531 }
 532
 533 int ds_get_bts_index(struct task_struct *task, size_t *pos)
 534 {
 535         return ds_get_index(task, pos, ds_bts);
 536 }
 537
 538 int ds_get_pebs_index(struct task_struct *task, size_t *pos)
 539 {
 540         return ds_get_index(task, pos, ds_pebs);
 541 }
 542
 543 static int ds_get_end(struct task_struct *task, size_t *pos,
 544                       enum ds_qualifier qual)
 545 {
 546         struct ds_context *context;
 547         unsigned long base, end;
 548         int error;
 549
 550         context = ds_get_context(task);
 551         error = ds_validate_access(context, qual);
 552         if (error < 0)
 553                 goto out;
 554
 555         base = ds_get(context->ds, qual, ds_buffer_base);
 556         end  = ds_get(context->ds, qual, ds_absolute_maximum);
 557
 558         error = ((end - base) / ds_cfg.sizeof_rec[qual]);
 559         if (pos)
 560                 *pos = error;
 561  out:
 562         ds_put_context(context);
 563         return error;
 564 }
 565
 566 int ds_get_bts_end(struct task_struct *task, size_t *pos)
 567 {
 568         return ds_get_end(task, pos, ds_bts);
 569 }
 570
 571 int ds_get_pebs_end(struct task_struct *task, size_t *pos)
 572 {
 573         return ds_get_end(task, pos, ds_pebs);
 574 }
 575
 576 static int ds_access(struct task_struct *task, size_t index,
 577                      const void **record, enum ds_qualifier qual)
 578 {
 579         struct ds_context *context;
 580         unsigned long base, idx;
 581         int error;
 582
 583         if (!record)
 584                 return -EINVAL;
 585
 586         context = ds_get_context(task);
 587         error = ds_validate_access(context, qual);
 588         if (error < 0)
 589                 goto out;
 590
 591         base = ds_get(context->ds, qual, ds_buffer_base);
 592         idx = base + (index * ds_cfg.sizeof_rec[qual]);
 593
 594         error = -EINVAL;
 595         if (idx > ds_get(context->ds, qual, ds_absolute_maximum))
 596                 goto out;
 597
 598         *record = (const void *)idx;
 599         error = ds_cfg.sizeof_rec[qual];
 600  out:
 601         ds_put_context(context);
 602         return error;
 603 }
 604
 605 int ds_access_bts(struct task_struct *task, size_t index, const void **record)
 606 {
 607         return ds_access(task, index, record, ds_bts);
 608 }
 609
 610 int ds_access_pebs(struct task_struct *task, size_t index, const void **record)
 611 {
 612         return ds_access(task, index, record, ds_pebs);
 613 }
 614
 615 static int ds_write(struct task_struct *task, const void *record, size_t size,
 616                     enum ds_qualifier qual, int force)
 617 {
 618         struct ds_context *context;
 619         int error;
 620
 621         if (!record)
 622                 return -EINVAL;
 623
 624         error = -EPERM;
 625         context = ds_get_context(task);
 626         if (!context)
 627                 goto out;
 628
 629         if (!force) {
 630                 error = ds_validate_access(context, qual);
 631                 if (error < 0)
 632                         goto out;
 633         }
 634
 635         error = 0;
 636         while (size) {
 637                 unsigned long base, index, end, write_end, int_th;
 638                 unsigned long write_size, adj_write_size;
 639
 640                 /*
 641                  * write as much as possible without producing an
 642                  * overflow interrupt.
 643                  *
 644                  * interrupt_threshold must either be
 645                  * - bigger than absolute_maximum or
 646                  * - point to a record between buffer_base and absolute_maximum
 647                  *
 648                  * index points to a valid record.
 649                  */
 650                 base   = ds_get(context->ds, qual, ds_buffer_base);
 651                 index  = ds_get(context->ds, qual, ds_index);
 652                 end    = ds_get(context->ds, qual, ds_absolute_maximum);
 653                 int_th = ds_get(context->ds, qual, ds_interrupt_threshold);
 654
 655                 write_end = min(end, int_th);
 656
 657                 /* if we are already beyond the interrupt threshold,
 658                  * we fill the entire buffer */
 659                 if (write_end <= index)
 660                         write_end = end;
 661
 662                 if (write_end <= index)
 663                         goto out;
 664
 665                 write_size = min((unsigned long) size, write_end - index);
 666                 memcpy((void *)index, record, write_size);
 667
 668                 record = (const char *)record + write_size;
 669                 size  -= write_size;
 670                 error += write_size;
 671
 672                 adj_write_size = write_size / ds_cfg.sizeof_rec[qual];
 673                 adj_write_size *= ds_cfg.sizeof_rec[qual];
 674
 675                 /* zero out trailing bytes */
 676                 memset((char *)index + write_size, 0,
 677                        adj_write_size - write_size);
 678                 index += adj_write_size;
 679
 680                 if (index >= end)
 681                         index = base;
 682                 ds_set(context->ds, qual, ds_index, index);
 683
 684                 if (index >= int_th)
 685                         ds_overflow(task, context, qual);
 686         }
 687
 688  out:
 689         ds_put_context(context);
 690         return error;
 691 }
 692
 693 int ds_write_bts(struct task_struct *task, const void *record, size_t size)
 694 {
 695         return ds_write(task, record, size, ds_bts, /* force = */ 0);
 696 }
 697
 698 int ds_write_pebs(struct task_struct *task, const void *record, size_t size)
 699 {
 700         return ds_write(task, record, size, ds_pebs, /* force = */ 0);
 701 }
 702
 703 int ds_unchecked_write_bts(struct task_struct *task,
 704                            const void *record, size_t size)
 705 {
 706         return ds_write(task, record, size, ds_bts, /* force = */ 1);
 707 }
 708
 709 int ds_unchecked_write_pebs(struct task_struct *task,
 710                             const void *record, size_t size)
 711 {
 712         return ds_write(task, record, size, ds_pebs, /* force = */ 1);
 713 }
 714
 715 static int ds_reset_or_clear(struct task_struct *task,
 716                              enum ds_qualifier qual, int clear)
 717 {
 718         struct ds_context *context;
 719         unsigned long base, end;
 720         int error;
 721
 722         context = ds_get_context(task);
 723         error = ds_validate_access(context, qual);
 724         if (error < 0)
 725                 goto out;
 726
 727         base = ds_get(context->ds, qual, ds_buffer_base);
 728         end  = ds_get(context->ds, qual, ds_absolute_maximum);
 729
 730         if (clear)
 731                 memset((void *)base, 0, end - base);
 732
 733         ds_set(context->ds, qual, ds_index, base);
 734
 735         error = 0;
 736  out:
 737         ds_put_context(context);
 738         return error;
 739 }
 740
 741 int ds_reset_bts(struct task_struct *task)
 742 {
 743         return ds_reset_or_clear(task, ds_bts, /* clear = */ 0);
 744 }
 745
 746 int ds_reset_pebs(struct task_struct *task)
 747 {
 748         return ds_reset_or_clear(task, ds_pebs, /* clear = */ 0);
 749 }
 750
 751 int ds_clear_bts(struct task_struct *task)
 752 {
 753         return ds_reset_or_clear(task, ds_bts, /* clear = */ 1);
 754 }
 755
 756 int ds_clear_pebs(struct task_struct *task)
 757 {
 758         return ds_reset_or_clear(task, ds_pebs, /* clear = */ 1);
 759 }
 760
 761 int ds_get_pebs_reset(struct task_struct *task, u64 *value)
 762 {
 763         struct ds_context *context;
 764         int error;
 765
 766         if (!value)
 767                 return -EINVAL;
 768
 769         context = ds_get_context(task);
 770         error = ds_validate_access(context, ds_pebs);
 771         if (error < 0)
 772                 goto out;
 773
 774         *value = *(u64 *)(context->ds + (ds_cfg.sizeof_field * 8));
 775
 776         error = 0;
 777  out:
 778         ds_put_context(context);
 779         return error;
 780 }
 781
 782 int ds_set_pebs_reset(struct task_struct *task, u64 value)
 783 {
 784         struct ds_context *context;
 785         int error;
 786
 787         context = ds_get_context(task);
 788         error = ds_validate_access(context, ds_pebs);
 789         if (error < 0)
 790                 goto out;
 791
 792         *(u64 *)(context->ds + (ds_cfg.sizeof_field * 8)) = value;
 793
 794         error = 0;
 795  out:
 796         ds_put_context(context);
 797         return error;
 798 }
 799
 800 static const struct ds_configuration ds_cfg_var = {
 801         .sizeof_ds    = sizeof(long) * 12,
 802         .sizeof_field = sizeof(long),
 803         .sizeof_rec[ds_bts]   = sizeof(long) * 3,
 804         .sizeof_rec[ds_pebs]  = sizeof(long) * 10
 805 };
 806 static const struct ds_configuration ds_cfg_64 = {
 807         .sizeof_ds    = 8 * 12,
 808         .sizeof_field = 8,
 809         .sizeof_rec[ds_bts]   = 8 * 3,
 810         .sizeof_rec[ds_pebs]  = 8 * 10
 811 };
 812
 813 static inline void
 814 ds_configure(const struct ds_configuration *cfg)
 815 {
 816         ds_cfg = *cfg;
 817 }
 818
 819 void __cpuinit ds_init_intel(struct cpuinfo_x86 *c)
 820 {
 821         switch (c->x86) {
 822         case 0x6:
 823                 switch (c->x86_model) {
 824                 case 0xD:
 825                 case 0xE: /* Pentium M */
 826                         ds_configure(&ds_cfg_var);
 827                         break;
 828                 case 0xF: /* Core2 */
 829                 case 0x1C: /* Atom */
 830                         ds_configure(&ds_cfg_64);
 831                         break;
 832                 default:
 833                         /* sorry, don't know about them */
 834                         break;
 835                 }
 836                 break;
 837         case 0xF:
 838                 switch (c->x86_model) {
 839                 case 0x0:
 840                 case 0x1:
 841                 case 0x2: /* Netburst */
 842                         ds_configure(&ds_cfg_var);
 843                         break;
 844                 default:
 845                         /* sorry, don't know about them */
 846                         break;
 847                 }
 848                 break;
 849         default:
 850                 /* sorry, don't know about them */
 851                 break;
 852         }
 853 }
 854
 855 void ds_free(struct ds_context *context)
 856 {
 857         /* This is called when the task owning the parameter context
 858          * is dying. There should not be any user of that context left
 859          * to disturb us, anymore. */
 860         unsigned long leftovers = context->count;
 861         while (leftovers--)
 862                 ds_put_context(context);
 863 }
 864 #endif /* CONFIG_X86_DS */