kernel/profile.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/kernel/profile.c
   4  *  Simple profiling. Manages a direct-mapped profile hit count buffer,
   5  *  with configurable resolution, support for restricting the cpus on
   6  *  which profiling is done, and switching between cpu time and
   7  *  schedule() calls via kernel command line parameters passed at boot.
   8  *
   9  *  Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
  10  *      Red Hat, July 2004
  11  *  Consolidation of architecture support code for profiling,
  12  *      Nadia Yvette Chambers, Oracle, July 2004
  13  *  Amortized hit count accounting via per-cpu open-addressed hashtables
  14  *      to resolve timer interrupt livelocks, Nadia Yvette Chambers,
  15  *      Oracle, 2004
  16  */
  17
  18 #include <linux/export.h>
  19 #include <linux/profile.h>
  20 #include <linux/memblock.h>
  21 #include <linux/notifier.h>
  22 #include <linux/mm.h>
  23 #include <linux/cpumask.h>
  24 #include <linux/cpu.h>
  25 #include <linux/highmem.h>
  26 #include <linux/mutex.h>
  27 #include <linux/slab.h>
  28 #include <linux/vmalloc.h>
  29 #include <linux/sched/stat.h>
  30
  31 #include <asm/sections.h>
  32 #include <asm/irq_regs.h>
  33 #include <asm/ptrace.h>
  34
  35 struct profile_hit {
  36         u32 pc, hits;
  37 };
  38 #define PROFILE_GRPSHIFT        3
  39 #define PROFILE_GRPSZ           (1 << PROFILE_GRPSHIFT)
  40 #define NR_PROFILE_HIT          (PAGE_SIZE/sizeof(struct profile_hit))
  41 #define NR_PROFILE_GRP          (NR_PROFILE_HIT/PROFILE_GRPSZ)
  42
  43 static atomic_t *prof_buffer;
  44 static unsigned long prof_len;
  45 static unsigned short int prof_shift;
  46
  47 int prof_on __read_mostly;
  48 EXPORT_SYMBOL_GPL(prof_on);
  49
  50 static cpumask_var_t prof_cpu_mask;
  51 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
  52 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
  53 static DEFINE_PER_CPU(int, cpu_profile_flip);
  54 static DEFINE_MUTEX(profile_flip_mutex);
  55 #endif /* CONFIG_SMP */
  56
  57 int profile_setup(char *str)
  58 {
  59         static const char schedstr[] = "schedule";
  60         static const char sleepstr[] = "sleep";
  61         static const char kvmstr[] = "kvm";
  62         int par;
  63
  64         if (!strncmp(str, sleepstr, strlen(sleepstr))) {
  65 #ifdef CONFIG_SCHEDSTATS
  66                 force_schedstat_enabled();
  67                 prof_on = SLEEP_PROFILING;
  68                 if (str[strlen(sleepstr)] == ',')
  69                         str += strlen(sleepstr) + 1;
  70                 if (get_option(&str, &par))
  71                         prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
  72                 pr_info("kernel sleep profiling enabled (shift: %u)\n",
  73                         prof_shift);
  74 #else
  75                 pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
  76 #endif /* CONFIG_SCHEDSTATS */
  77         } else if (!strncmp(str, schedstr, strlen(schedstr))) {
  78                 prof_on = SCHED_PROFILING;
  79                 if (str[strlen(schedstr)] == ',')
  80                         str += strlen(schedstr) + 1;
  81                 if (get_option(&str, &par))
  82                         prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
  83                 pr_info("kernel schedule profiling enabled (shift: %u)\n",
  84                         prof_shift);
  85         } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
  86                 prof_on = KVM_PROFILING;
  87                 if (str[strlen(kvmstr)] == ',')
  88                         str += strlen(kvmstr) + 1;
  89                 if (get_option(&str, &par))
  90                         prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
  91                 pr_info("kernel KVM profiling enabled (shift: %u)\n",
  92                         prof_shift);
  93         } else if (get_option(&str, &par)) {
  94                 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
  95                 prof_on = CPU_PROFILING;
  96                 pr_info("kernel profiling enabled (shift: %u)\n",
  97                         prof_shift);
  98         }
  99         return 1;
 100 }
 101 __setup("profile=", profile_setup);
 102
 103
 104 int __ref profile_init(void)
 105 {
 106         int buffer_bytes;
 107         if (!prof_on)
 108                 return 0;
 109
 110         /* only text is profiled */
 111         prof_len = (_etext - _stext) >> prof_shift;
 112         buffer_bytes = prof_len*sizeof(atomic_t);
 113
 114         if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
 115                 return -ENOMEM;
 116
 117         cpumask_copy(prof_cpu_mask, cpu_possible_mask);
 118
 119         prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
 120         if (prof_buffer)
 121                 return 0;
 122
 123         prof_buffer = alloc_pages_exact(buffer_bytes,
 124                                         GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
 125         if (prof_buffer)
 126                 return 0;
 127
 128         prof_buffer = vzalloc(buffer_bytes);
 129         if (prof_buffer)
 130                 return 0;
 131
 132         free_cpumask_var(prof_cpu_mask);
 133         return -ENOMEM;
 134 }
 135
 136 /* Profile event notifications */
 137
 138 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 139 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 140 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
 141
 142 void profile_task_exit(struct task_struct *task)
 143 {
 144         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 145 }
 146
 147 int profile_handoff_task(struct task_struct *task)
 148 {
 149         int ret;
 150         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 151         return (ret == NOTIFY_OK) ? 1 : 0;
 152 }
 153
 154 void profile_munmap(unsigned long addr)
 155 {
 156         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 157 }
 158
 159 int task_handoff_register(struct notifier_block *n)
 160 {
 161         return atomic_notifier_chain_register(&task_free_notifier, n);
 162 }
 163 EXPORT_SYMBOL_GPL(task_handoff_register);
 164
 165 int task_handoff_unregister(struct notifier_block *n)
 166 {
 167         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 168 }
 169 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 170
 171 int profile_event_register(enum profile_type type, struct notifier_block *n)
 172 {
 173         int err = -EINVAL;
 174
 175         switch (type) {
 176         case PROFILE_TASK_EXIT:
 177                 err = blocking_notifier_chain_register(
 178                                 &task_exit_notifier, n);
 179                 break;
 180         case PROFILE_MUNMAP:
 181                 err = blocking_notifier_chain_register(
 182                                 &munmap_notifier, n);
 183                 break;
 184         }
 185
 186         return err;
 187 }
 188 EXPORT_SYMBOL_GPL(profile_event_register);
 189
 190 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 191 {
 192         int err = -EINVAL;
 193
 194         switch (type) {
 195         case PROFILE_TASK_EXIT:
 196                 err = blocking_notifier_chain_unregister(
 197                                 &task_exit_notifier, n);
 198                 break;
 199         case PROFILE_MUNMAP:
 200                 err = blocking_notifier_chain_unregister(
 201                                 &munmap_notifier, n);
 202                 break;
 203         }
 204
 205         return err;
 206 }
 207 EXPORT_SYMBOL_GPL(profile_event_unregister);
 208
 209 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
 210 /*
 211  * Each cpu has a pair of open-addressed hashtables for pending
 212  * profile hits. read_profile() IPI's all cpus to request them
 213  * to flip buffers and flushes their contents to prof_buffer itself.
 214  * Flip requests are serialized by the profile_flip_mutex. The sole
 215  * use of having a second hashtable is for avoiding cacheline
 216  * contention that would otherwise happen during flushes of pending
 217  * profile hits required for the accuracy of reported profile hits
 218  * and so resurrect the interrupt livelock issue.
 219  *
 220  * The open-addressed hashtables are indexed by profile buffer slot
 221  * and hold the number of pending hits to that profile buffer slot on
 222  * a cpu in an entry. When the hashtable overflows, all pending hits
 223  * are accounted to their corresponding profile buffer slots with
 224  * atomic_add() and the hashtable emptied. As numerous pending hits
 225  * may be accounted to a profile buffer slot in a hashtable entry,
 226  * this amortizes a number of atomic profile buffer increments likely
 227  * to be far larger than the number of entries in the hashtable,
 228  * particularly given that the number of distinct profile buffer
 229  * positions to which hits are accounted during short intervals (e.g.
 230  * several seconds) is usually very small. Exclusion from buffer
 231  * flipping is provided by interrupt disablement (note that for
 232  * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
 233  * process context).
 234  * The hash function is meant to be lightweight as opposed to strong,
 235  * and was vaguely inspired by ppc64 firmware-supported inverted
 236  * pagetable hash functions, but uses a full hashtable full of finite
 237  * collision chains, not just pairs of them.
 238  *
 239  * -- nyc
 240  */
 241 static void __profile_flip_buffers(void *unused)
 242 {
 243         int cpu = smp_processor_id();
 244
 245         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 246 }
 247
 248 static void profile_flip_buffers(void)
 249 {
 250         int i, j, cpu;
 251
 252         mutex_lock(&profile_flip_mutex);
 253         j = per_cpu(cpu_profile_flip, get_cpu());
 254         put_cpu();
 255         on_each_cpu(__profile_flip_buffers, NULL, 1);
 256         for_each_online_cpu(cpu) {
 257                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 258                 for (i = 0; i < NR_PROFILE_HIT; ++i) {
 259                         if (!hits[i].hits) {
 260                                 if (hits[i].pc)
 261                                         hits[i].pc = 0;
 262                                 continue;
 263                         }
 264                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 265                         hits[i].hits = hits[i].pc = 0;
 266                 }
 267         }
 268         mutex_unlock(&profile_flip_mutex);
 269 }
 270
 271 static void profile_discard_flip_buffers(void)
 272 {
 273         int i, cpu;
 274
 275         mutex_lock(&profile_flip_mutex);
 276         i = per_cpu(cpu_profile_flip, get_cpu());
 277         put_cpu();
 278         on_each_cpu(__profile_flip_buffers, NULL, 1);
 279         for_each_online_cpu(cpu) {
 280                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 281                 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 282         }
 283         mutex_unlock(&profile_flip_mutex);
 284 }
 285
 286 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 287 {
 288         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 289         int i, j, cpu;
 290         struct profile_hit *hits;
 291
 292         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 293         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 294         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 295         cpu = get_cpu();
 296         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 297         if (!hits) {
 298                 put_cpu();
 299                 return;
 300         }
 301         /*
 302          * We buffer the global profiler buffer into a per-CPU
 303          * queue and thus reduce the number of global (and possibly
 304          * NUMA-alien) accesses. The write-queue is self-coalescing:
 305          */
 306         local_irq_save(flags);
 307         do {
 308                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 309                         if (hits[i + j].pc == pc) {
 310                                 hits[i + j].hits += nr_hits;
 311                                 goto out;
 312                         } else if (!hits[i + j].hits) {
 313                                 hits[i + j].pc = pc;
 314                                 hits[i + j].hits = nr_hits;
 315                                 goto out;
 316                         }
 317                 }
 318                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 319         } while (i != primary);
 320
 321         /*
 322          * Add the current hit(s) and flush the write-queue out
 323          * to the global buffer:
 324          */
 325         atomic_add(nr_hits, &prof_buffer[pc]);
 326         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 327                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 328                 hits[i].pc = hits[i].hits = 0;
 329         }
 330 out:
 331         local_irq_restore(flags);
 332         put_cpu();
 333 }
 334
 335 static int profile_dead_cpu(unsigned int cpu)
 336 {
 337         struct page *page;
 338         int i;
 339
 340         if (cpumask_available(prof_cpu_mask))
 341                 cpumask_clear_cpu(cpu, prof_cpu_mask);
 342
 343         for (i = 0; i < 2; i++) {
 344                 if (per_cpu(cpu_profile_hits, cpu)[i]) {
 345                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]);
 346                         per_cpu(cpu_profile_hits, cpu)[i] = NULL;
 347                         __free_page(page);
 348                 }
 349         }
 350         return 0;
 351 }
 352
 353 static int profile_prepare_cpu(unsigned int cpu)
 354 {
 355         int i, node = cpu_to_mem(cpu);
 356         struct page *page;
 357
 358         per_cpu(cpu_profile_flip, cpu) = 0;
 359
 360         for (i = 0; i < 2; i++) {
 361                 if (per_cpu(cpu_profile_hits, cpu)[i])
 362                         continue;
 363
 364                 page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 365                 if (!page) {
 366                         profile_dead_cpu(cpu);
 367                         return -ENOMEM;
 368                 }
 369                 per_cpu(cpu_profile_hits, cpu)[i] = page_address(page);
 370
 371         }
 372         return 0;
 373 }
 374
 375 static int profile_online_cpu(unsigned int cpu)
 376 {
 377         if (cpumask_available(prof_cpu_mask))
 378                 cpumask_set_cpu(cpu, prof_cpu_mask);
 379
 380         return 0;
 381 }
 382
 383 #else /* !CONFIG_SMP */
 384 #define profile_flip_buffers()          do { } while (0)
 385 #define profile_discard_flip_buffers()  do { } while (0)
 386
 387 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 388 {
 389         unsigned long pc;
 390         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 391         atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
 392 }
 393 #endif /* !CONFIG_SMP */
 394
 395 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 396 {
 397         if (prof_on != type || !prof_buffer)
 398                 return;
 399         do_profile_hits(type, __pc, nr_hits);
 400 }
 401 EXPORT_SYMBOL_GPL(profile_hits);
 402
 403 void profile_tick(int type)
 404 {
 405         struct pt_regs *regs = get_irq_regs();
 406
 407         if (!user_mode(regs) && cpumask_available(prof_cpu_mask) &&
 408             cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
 409                 profile_hit(type, (void *)profile_pc(regs));
 410 }
 411
 412 #ifdef CONFIG_PROC_FS
 413 #include <linux/proc_fs.h>
 414 #include <linux/seq_file.h>
 415 #include <linux/uaccess.h>
 416
 417 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
 418 {
 419         seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
 420         return 0;
 421 }
 422
 423 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
 424 {
 425         return single_open(file, prof_cpu_mask_proc_show, NULL);
 426 }
 427
 428 static ssize_t prof_cpu_mask_proc_write(struct file *file,
 429         const char __user *buffer, size_t count, loff_t *pos)
 430 {
 431         cpumask_var_t new_value;
 432         int err;
 433
 434         if (!zalloc_cpumask_var(&new_value, GFP_KERNEL))
 435                 return -ENOMEM;
 436
 437         err = cpumask_parse_user(buffer, count, new_value);
 438         if (!err) {
 439                 cpumask_copy(prof_cpu_mask, new_value);
 440                 err = count;
 441         }
 442         free_cpumask_var(new_value);
 443         return err;
 444 }
 445
 446 static const struct proc_ops prof_cpu_mask_proc_ops = {
 447         .proc_open      = prof_cpu_mask_proc_open,
 448         .proc_read      = seq_read,
 449         .proc_lseek     = seq_lseek,
 450         .proc_release   = single_release,
 451         .proc_write     = prof_cpu_mask_proc_write,
 452 };
 453
 454 void create_prof_cpu_mask(void)
 455 {
 456         /* create /proc/irq/prof_cpu_mask */
 457         proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_ops);
 458 }
 459
 460 /*
 461  * This function accesses profiling information. The returned data is
 462  * binary: the sampling step and the actual contents of the profile
 463  * buffer. Use of the program readprofile is recommended in order to
 464  * get meaningful info out of these data.
 465  */
 466 static ssize_t
 467 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 468 {
 469         unsigned long p = *ppos;
 470         ssize_t read;
 471         char *pnt;
 472         unsigned long sample_step = 1UL << prof_shift;
 473
 474         profile_flip_buffers();
 475         if (p >= (prof_len+1)*sizeof(unsigned int))
 476                 return 0;
 477         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 478                 count = (prof_len+1)*sizeof(unsigned int) - p;
 479         read = 0;
 480
 481         while (p < sizeof(unsigned int) && count > 0) {
 482                 if (put_user(*((char *)(&sample_step)+p), buf))
 483                         return -EFAULT;
 484                 buf++; p++; count--; read++;
 485         }
 486         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 487         if (copy_to_user(buf, (void *)pnt, count))
 488                 return -EFAULT;
 489         read += count;
 490         *ppos += read;
 491         return read;
 492 }
 493
 494 /*
 495  * Writing to /proc/profile resets the counters
 496  *
 497  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 498  * interrupt frequency, on architectures that support this.
 499  */
 500 static ssize_t write_profile(struct file *file, const char __user *buf,
 501                              size_t count, loff_t *ppos)
 502 {
 503 #ifdef CONFIG_SMP
 504         extern int setup_profiling_timer(unsigned int multiplier);
 505
 506         if (count == sizeof(int)) {
 507                 unsigned int multiplier;
 508
 509                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 510                         return -EFAULT;
 511
 512                 if (setup_profiling_timer(multiplier))
 513                         return -EINVAL;
 514         }
 515 #endif
 516         profile_discard_flip_buffers();
 517         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 518         return count;
 519 }
 520
 521 static const struct proc_ops profile_proc_ops = {
 522         .proc_read      = read_profile,
 523         .proc_write     = write_profile,
 524         .proc_lseek     = default_llseek,
 525 };
 526
 527 int __ref create_proc_profile(void)
 528 {
 529         struct proc_dir_entry *entry;
 530 #ifdef CONFIG_SMP
 531         enum cpuhp_state online_state;
 532 #endif
 533
 534         int err = 0;
 535
 536         if (!prof_on)
 537                 return 0;
 538 #ifdef CONFIG_SMP
 539         err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE",
 540                                 profile_prepare_cpu, profile_dead_cpu);
 541         if (err)
 542                 return err;
 543
 544         err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE",
 545                                 profile_online_cpu, NULL);
 546         if (err < 0)
 547                 goto err_state_prep;
 548         online_state = err;
 549         err = 0;
 550 #endif
 551         entry = proc_create("profile", S_IWUSR | S_IRUGO,
 552                             NULL, &profile_proc_ops);
 553         if (!entry)
 554                 goto err_state_onl;
 555         proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
 556
 557         return err;
 558 err_state_onl:
 559 #ifdef CONFIG_SMP
 560         cpuhp_remove_state(online_state);
 561 err_state_prep:
 562         cpuhp_remove_state(CPUHP_PROFILE_PREPARE);
 563 #endif
 564         return err;
 565 }
 566 subsys_initcall(create_proc_profile);
 567 #endif /* CONFIG_PROC_FS */