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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Stack depot - a stack trace storage that avoids duplication.4 *5 * Internally, stack depot maintains a hash table of unique stacktraces. The6 * stack traces themselves are stored contiguously one after another in a set7 * of separate page allocations.8 *9 * Author: Alexander Potapenko <glider@google.com>10 * Copyright (C) 2016 Google, Inc.11 *12 * Based on the code by Dmitry Chernenkov.13 */14 15#define pr_fmt(fmt) "stackdepot: " fmt16 17#include <linux/debugfs.h>18#include <linux/gfp.h>19#include <linux/jhash.h>20#include <linux/kernel.h>21#include <linux/kmsan.h>22#include <linux/list.h>23#include <linux/mm.h>24#include <linux/mutex.h>25#include <linux/poison.h>26#include <linux/printk.h>27#include <linux/rculist.h>28#include <linux/rcupdate.h>29#include <linux/refcount.h>30#include <linux/slab.h>31#include <linux/spinlock.h>32#include <linux/stacktrace.h>33#include <linux/stackdepot.h>34#include <linux/string.h>35#include <linux/types.h>36#include <linux/memblock.h>37#include <linux/kasan-enabled.h>38 39#define DEPOT_POOLS_CAP 819240/* The pool_index is offset by 1 so the first record does not have a 0 handle. */41#define DEPOT_MAX_POOLS \42 (((1LL << (DEPOT_POOL_INDEX_BITS)) - 1 < DEPOT_POOLS_CAP) ? \43 (1LL << (DEPOT_POOL_INDEX_BITS)) - 1 : DEPOT_POOLS_CAP)44 45static bool stack_depot_disabled;46static bool __stack_depot_early_init_requested __initdata = IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT);47static bool __stack_depot_early_init_passed __initdata;48 49/* Use one hash table bucket per 16 KB of memory. */50#define STACK_HASH_TABLE_SCALE 1451/* Limit the number of buckets between 4K and 1M. */52#define STACK_BUCKET_NUMBER_ORDER_MIN 1253#define STACK_BUCKET_NUMBER_ORDER_MAX 2054/* Initial seed for jhash2. */55#define STACK_HASH_SEED 0x9747b28c56 57/* Hash table of stored stack records. */58static struct list_head *stack_table;59/* Fixed order of the number of table buckets. Used when KASAN is enabled. */60static unsigned int stack_bucket_number_order;61/* Hash mask for indexing the table. */62static unsigned int stack_hash_mask;63 64/* Array of memory regions that store stack records. */65static void *stack_pools[DEPOT_MAX_POOLS];66/* Newly allocated pool that is not yet added to stack_pools. */67static void *new_pool;68/* Number of pools in stack_pools. */69static int pools_num;70/* Offset to the unused space in the currently used pool. */71static size_t pool_offset = DEPOT_POOL_SIZE;72/* Freelist of stack records within stack_pools. */73static LIST_HEAD(free_stacks);74/* The lock must be held when performing pool or freelist modifications. */75static DEFINE_RAW_SPINLOCK(pool_lock);76 77/* Statistics counters for debugfs. */78enum depot_counter_id {79 DEPOT_COUNTER_REFD_ALLOCS,80 DEPOT_COUNTER_REFD_FREES,81 DEPOT_COUNTER_REFD_INUSE,82 DEPOT_COUNTER_FREELIST_SIZE,83 DEPOT_COUNTER_PERSIST_COUNT,84 DEPOT_COUNTER_PERSIST_BYTES,85 DEPOT_COUNTER_COUNT,86};87static long counters[DEPOT_COUNTER_COUNT];88static const char *const counter_names[] = {89 [DEPOT_COUNTER_REFD_ALLOCS] = "refcounted_allocations",90 [DEPOT_COUNTER_REFD_FREES] = "refcounted_frees",91 [DEPOT_COUNTER_REFD_INUSE] = "refcounted_in_use",92 [DEPOT_COUNTER_FREELIST_SIZE] = "freelist_size",93 [DEPOT_COUNTER_PERSIST_COUNT] = "persistent_count",94 [DEPOT_COUNTER_PERSIST_BYTES] = "persistent_bytes",95};96static_assert(ARRAY_SIZE(counter_names) == DEPOT_COUNTER_COUNT);97 98static int __init disable_stack_depot(char *str)99{100 return kstrtobool(str, &stack_depot_disabled);101}102early_param("stack_depot_disable", disable_stack_depot);103 104void __init stack_depot_request_early_init(void)105{106 /* Too late to request early init now. */107 WARN_ON(__stack_depot_early_init_passed);108 109 __stack_depot_early_init_requested = true;110}111 112/* Initialize list_head's within the hash table. */113static void init_stack_table(unsigned long entries)114{115 unsigned long i;116 117 for (i = 0; i < entries; i++)118 INIT_LIST_HEAD(&stack_table[i]);119}120 121/* Allocates a hash table via memblock. Can only be used during early boot. */122int __init stack_depot_early_init(void)123{124 unsigned long entries = 0;125 126 /* This function must be called only once, from mm_init(). */127 if (WARN_ON(__stack_depot_early_init_passed))128 return 0;129 __stack_depot_early_init_passed = true;130 131 /*132 * Print disabled message even if early init has not been requested:133 * stack_depot_init() will not print one.134 */135 if (stack_depot_disabled) {136 pr_info("disabled\n");137 return 0;138 }139 140 /*141 * If KASAN is enabled, use the maximum order: KASAN is frequently used142 * in fuzzing scenarios, which leads to a large number of different143 * stack traces being stored in stack depot.144 */145 if (kasan_enabled() && !stack_bucket_number_order)146 stack_bucket_number_order = STACK_BUCKET_NUMBER_ORDER_MAX;147 148 /*149 * Check if early init has been requested after setting150 * stack_bucket_number_order: stack_depot_init() uses its value.151 */152 if (!__stack_depot_early_init_requested)153 return 0;154 155 /*156 * If stack_bucket_number_order is not set, leave entries as 0 to rely157 * on the automatic calculations performed by alloc_large_system_hash().158 */159 if (stack_bucket_number_order)160 entries = 1UL << stack_bucket_number_order;161 pr_info("allocating hash table via alloc_large_system_hash\n");162 stack_table = alloc_large_system_hash("stackdepot",163 sizeof(struct list_head),164 entries,165 STACK_HASH_TABLE_SCALE,166 HASH_EARLY,167 NULL,168 &stack_hash_mask,169 1UL << STACK_BUCKET_NUMBER_ORDER_MIN,170 1UL << STACK_BUCKET_NUMBER_ORDER_MAX);171 if (!stack_table) {172 pr_err("hash table allocation failed, disabling\n");173 stack_depot_disabled = true;174 return -ENOMEM;175 }176 if (!entries) {177 /*178 * Obtain the number of entries that was calculated by179 * alloc_large_system_hash().180 */181 entries = stack_hash_mask + 1;182 }183 init_stack_table(entries);184 185 return 0;186}187 188/* Allocates a hash table via kvcalloc. Can be used after boot. */189int stack_depot_init(void)190{191 static DEFINE_MUTEX(stack_depot_init_mutex);192 unsigned long entries;193 int ret = 0;194 195 mutex_lock(&stack_depot_init_mutex);196 197 if (stack_depot_disabled || stack_table)198 goto out_unlock;199 200 /*201 * Similarly to stack_depot_early_init, use stack_bucket_number_order202 * if assigned, and rely on automatic scaling otherwise.203 */204 if (stack_bucket_number_order) {205 entries = 1UL << stack_bucket_number_order;206 } else {207 int scale = STACK_HASH_TABLE_SCALE;208 209 entries = nr_free_buffer_pages();210 entries = roundup_pow_of_two(entries);211 212 if (scale > PAGE_SHIFT)213 entries >>= (scale - PAGE_SHIFT);214 else215 entries <<= (PAGE_SHIFT - scale);216 }217 218 if (entries < 1UL << STACK_BUCKET_NUMBER_ORDER_MIN)219 entries = 1UL << STACK_BUCKET_NUMBER_ORDER_MIN;220 if (entries > 1UL << STACK_BUCKET_NUMBER_ORDER_MAX)221 entries = 1UL << STACK_BUCKET_NUMBER_ORDER_MAX;222 223 pr_info("allocating hash table of %lu entries via kvcalloc\n", entries);224 stack_table = kvcalloc(entries, sizeof(struct list_head), GFP_KERNEL);225 if (!stack_table) {226 pr_err("hash table allocation failed, disabling\n");227 stack_depot_disabled = true;228 ret = -ENOMEM;229 goto out_unlock;230 }231 stack_hash_mask = entries - 1;232 init_stack_table(entries);233 234out_unlock:235 mutex_unlock(&stack_depot_init_mutex);236 237 return ret;238}239EXPORT_SYMBOL_GPL(stack_depot_init);240 241/*242 * Initializes new stack pool, and updates the list of pools.243 */244static bool depot_init_pool(void **prealloc)245{246 lockdep_assert_held(&pool_lock);247 248 if (unlikely(pools_num >= DEPOT_MAX_POOLS)) {249 /* Bail out if we reached the pool limit. */250 WARN_ON_ONCE(pools_num > DEPOT_MAX_POOLS); /* should never happen */251 WARN_ON_ONCE(!new_pool); /* to avoid unnecessary pre-allocation */252 WARN_ONCE(1, "Stack depot reached limit capacity");253 return false;254 }255 256 if (!new_pool && *prealloc) {257 /* We have preallocated memory, use it. */258 WRITE_ONCE(new_pool, *prealloc);259 *prealloc = NULL;260 }261 262 if (!new_pool)263 return false; /* new_pool and *prealloc are NULL */264 265 /* Save reference to the pool to be used by depot_fetch_stack(). */266 stack_pools[pools_num] = new_pool;267 268 /*269 * Stack depot tries to keep an extra pool allocated even before it runs270 * out of space in the currently used pool.271 *272 * To indicate that a new preallocation is needed new_pool is reset to273 * NULL; do not reset to NULL if we have reached the maximum number of274 * pools.275 */276 if (pools_num < DEPOT_MAX_POOLS)277 WRITE_ONCE(new_pool, NULL);278 else279 WRITE_ONCE(new_pool, STACK_DEPOT_POISON);280 281 /* Pairs with concurrent READ_ONCE() in depot_fetch_stack(). */282 WRITE_ONCE(pools_num, pools_num + 1);283 ASSERT_EXCLUSIVE_WRITER(pools_num);284 285 pool_offset = 0;286 287 return true;288}289 290/* Keeps the preallocated memory to be used for a new stack depot pool. */291static void depot_keep_new_pool(void **prealloc)292{293 lockdep_assert_held(&pool_lock);294 295 /*296 * If a new pool is already saved or the maximum number of297 * pools is reached, do not use the preallocated memory.298 */299 if (new_pool)300 return;301 302 WRITE_ONCE(new_pool, *prealloc);303 *prealloc = NULL;304}305 306/*307 * Try to initialize a new stack record from the current pool, a cached pool, or308 * the current pre-allocation.309 */310static struct stack_record *depot_pop_free_pool(void **prealloc, size_t size)311{312 struct stack_record *stack;313 void *current_pool;314 u32 pool_index;315 316 lockdep_assert_held(&pool_lock);317 318 if (pool_offset + size > DEPOT_POOL_SIZE) {319 if (!depot_init_pool(prealloc))320 return NULL;321 }322 323 if (WARN_ON_ONCE(pools_num < 1))324 return NULL;325 pool_index = pools_num - 1;326 current_pool = stack_pools[pool_index];327 if (WARN_ON_ONCE(!current_pool))328 return NULL;329 330 stack = current_pool + pool_offset;331 332 /* Pre-initialize handle once. */333 stack->handle.pool_index_plus_1 = pool_index + 1;334 stack->handle.offset = pool_offset >> DEPOT_STACK_ALIGN;335 stack->handle.extra = 0;336 INIT_LIST_HEAD(&stack->hash_list);337 338 pool_offset += size;339 340 return stack;341}342 343/* Try to find next free usable entry from the freelist. */344static struct stack_record *depot_pop_free(void)345{346 struct stack_record *stack;347 348 lockdep_assert_held(&pool_lock);349 350 if (list_empty(&free_stacks))351 return NULL;352 353 /*354 * We maintain the invariant that the elements in front are least355 * recently used, and are therefore more likely to be associated with an356 * RCU grace period in the past. Consequently it is sufficient to only357 * check the first entry.358 */359 stack = list_first_entry(&free_stacks, struct stack_record, free_list);360 if (!poll_state_synchronize_rcu(stack->rcu_state))361 return NULL;362 363 list_del(&stack->free_list);364 counters[DEPOT_COUNTER_FREELIST_SIZE]--;365 366 return stack;367}368 369static inline size_t depot_stack_record_size(struct stack_record *s, unsigned int nr_entries)370{371 const size_t used = flex_array_size(s, entries, nr_entries);372 const size_t unused = sizeof(s->entries) - used;373 374 WARN_ON_ONCE(sizeof(s->entries) < used);375 376 return ALIGN(sizeof(struct stack_record) - unused, 1 << DEPOT_STACK_ALIGN);377}378 379/* Allocates a new stack in a stack depot pool. */380static struct stack_record *381depot_alloc_stack(unsigned long *entries, unsigned int nr_entries, u32 hash, depot_flags_t flags, void **prealloc)382{383 struct stack_record *stack = NULL;384 size_t record_size;385 386 lockdep_assert_held(&pool_lock);387 388 /* This should already be checked by public API entry points. */389 if (WARN_ON_ONCE(!nr_entries))390 return NULL;391 392 /* Limit number of saved frames to CONFIG_STACKDEPOT_MAX_FRAMES. */393 if (nr_entries > CONFIG_STACKDEPOT_MAX_FRAMES)394 nr_entries = CONFIG_STACKDEPOT_MAX_FRAMES;395 396 if (flags & STACK_DEPOT_FLAG_GET) {397 /*398 * Evictable entries have to allocate the max. size so they may399 * safely be re-used by differently sized allocations.400 */401 record_size = depot_stack_record_size(stack, CONFIG_STACKDEPOT_MAX_FRAMES);402 stack = depot_pop_free();403 } else {404 record_size = depot_stack_record_size(stack, nr_entries);405 }406 407 if (!stack) {408 stack = depot_pop_free_pool(prealloc, record_size);409 if (!stack)410 return NULL;411 }412 413 /* Save the stack trace. */414 stack->hash = hash;415 stack->size = nr_entries;416 /* stack->handle is already filled in by depot_pop_free_pool(). */417 memcpy(stack->entries, entries, flex_array_size(stack, entries, nr_entries));418 419 if (flags & STACK_DEPOT_FLAG_GET) {420 refcount_set(&stack->count, 1);421 counters[DEPOT_COUNTER_REFD_ALLOCS]++;422 counters[DEPOT_COUNTER_REFD_INUSE]++;423 } else {424 /* Warn on attempts to switch to refcounting this entry. */425 refcount_set(&stack->count, REFCOUNT_SATURATED);426 counters[DEPOT_COUNTER_PERSIST_COUNT]++;427 counters[DEPOT_COUNTER_PERSIST_BYTES] += record_size;428 }429 430 /*431 * Let KMSAN know the stored stack record is initialized. This shall432 * prevent false positive reports if instrumented code accesses it.433 */434 kmsan_unpoison_memory(stack, record_size);435 436 return stack;437}438 439static struct stack_record *depot_fetch_stack(depot_stack_handle_t handle)440{441 const int pools_num_cached = READ_ONCE(pools_num);442 union handle_parts parts = { .handle = handle };443 void *pool;444 u32 pool_index = parts.pool_index_plus_1 - 1;445 size_t offset = parts.offset << DEPOT_STACK_ALIGN;446 struct stack_record *stack;447 448 lockdep_assert_not_held(&pool_lock);449 450 if (pool_index >= pools_num_cached) {451 WARN(1, "pool index %d out of bounds (%d) for stack id %08x\n",452 pool_index, pools_num_cached, handle);453 return NULL;454 }455 456 pool = stack_pools[pool_index];457 if (WARN_ON(!pool))458 return NULL;459 460 stack = pool + offset;461 if (WARN_ON(!refcount_read(&stack->count)))462 return NULL;463 464 return stack;465}466 467/* Links stack into the freelist. */468static void depot_free_stack(struct stack_record *stack)469{470 unsigned long flags;471 472 lockdep_assert_not_held(&pool_lock);473 474 raw_spin_lock_irqsave(&pool_lock, flags);475 printk_deferred_enter();476 477 /*478 * Remove the entry from the hash list. Concurrent list traversal may479 * still observe the entry, but since the refcount is zero, this entry480 * will no longer be considered as valid.481 */482 list_del_rcu(&stack->hash_list);483 484 /*485 * Due to being used from constrained contexts such as the allocators,486 * NMI, or even RCU itself, stack depot cannot rely on primitives that487 * would sleep (such as synchronize_rcu()) or recursively call into488 * stack depot again (such as call_rcu()).489 *490 * Instead, get an RCU cookie, so that we can ensure this entry isn't491 * moved onto another list until the next grace period, and concurrent492 * RCU list traversal remains safe.493 */494 stack->rcu_state = get_state_synchronize_rcu();495 496 /*497 * Add the entry to the freelist tail, so that older entries are498 * considered first - their RCU cookie is more likely to no longer be499 * associated with the current grace period.500 */501 list_add_tail(&stack->free_list, &free_stacks);502 503 counters[DEPOT_COUNTER_FREELIST_SIZE]++;504 counters[DEPOT_COUNTER_REFD_FREES]++;505 counters[DEPOT_COUNTER_REFD_INUSE]--;506 507 printk_deferred_exit();508 raw_spin_unlock_irqrestore(&pool_lock, flags);509}510 511/* Calculates the hash for a stack. */512static inline u32 hash_stack(unsigned long *entries, unsigned int size)513{514 return jhash2((u32 *)entries,515 array_size(size, sizeof(*entries)) / sizeof(u32),516 STACK_HASH_SEED);517}518 519/*520 * Non-instrumented version of memcmp().521 * Does not check the lexicographical order, only the equality.522 */523static inline524int stackdepot_memcmp(const unsigned long *u1, const unsigned long *u2,525 unsigned int n)526{527 for ( ; n-- ; u1++, u2++) {528 if (*u1 != *u2)529 return 1;530 }531 return 0;532}533 534/* Finds a stack in a bucket of the hash table. */535static inline struct stack_record *find_stack(struct list_head *bucket,536 unsigned long *entries, int size,537 u32 hash, depot_flags_t flags)538{539 struct stack_record *stack, *ret = NULL;540 541 /*542 * Stack depot may be used from instrumentation that instruments RCU or543 * tracing itself; use variant that does not call into RCU and cannot be544 * traced.545 *546 * Note: Such use cases must take care when using refcounting to evict547 * unused entries, because the stack record free-then-reuse code paths548 * do call into RCU.549 */550 rcu_read_lock_sched_notrace();551 552 list_for_each_entry_rcu(stack, bucket, hash_list) {553 if (stack->hash != hash || stack->size != size)554 continue;555 556 /*557 * This may race with depot_free_stack() accessing the freelist558 * management state unioned with @entries. The refcount is zero559 * in that case and the below refcount_inc_not_zero() will fail.560 */561 if (data_race(stackdepot_memcmp(entries, stack->entries, size)))562 continue;563 564 /*565 * Try to increment refcount. If this succeeds, the stack record566 * is valid and has not yet been freed.567 *568 * If STACK_DEPOT_FLAG_GET is not used, it is undefined behavior569 * to then call stack_depot_put() later, and we can assume that570 * a stack record is never placed back on the freelist.571 */572 if ((flags & STACK_DEPOT_FLAG_GET) && !refcount_inc_not_zero(&stack->count))573 continue;574 575 ret = stack;576 break;577 }578 579 rcu_read_unlock_sched_notrace();580 581 return ret;582}583 584depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,585 unsigned int nr_entries,586 gfp_t alloc_flags,587 depot_flags_t depot_flags)588{589 struct list_head *bucket;590 struct stack_record *found = NULL;591 depot_stack_handle_t handle = 0;592 struct page *page = NULL;593 void *prealloc = NULL;594 bool can_alloc = depot_flags & STACK_DEPOT_FLAG_CAN_ALLOC;595 unsigned long flags;596 u32 hash;597 598 if (WARN_ON(depot_flags & ~STACK_DEPOT_FLAGS_MASK))599 return 0;600 601 /*602 * If this stack trace is from an interrupt, including anything before603 * interrupt entry usually leads to unbounded stack depot growth.604 *605 * Since use of filter_irq_stacks() is a requirement to ensure stack606 * depot can efficiently deduplicate interrupt stacks, always607 * filter_irq_stacks() to simplify all callers' use of stack depot.608 */609 nr_entries = filter_irq_stacks(entries, nr_entries);610 611 if (unlikely(nr_entries == 0) || stack_depot_disabled)612 return 0;613 614 hash = hash_stack(entries, nr_entries);615 bucket = &stack_table[hash & stack_hash_mask];616 617 /* Fast path: look the stack trace up without locking. */618 found = find_stack(bucket, entries, nr_entries, hash, depot_flags);619 if (found)620 goto exit;621 622 /*623 * Allocate memory for a new pool if required now:624 * we won't be able to do that under the lock.625 */626 if (unlikely(can_alloc && !READ_ONCE(new_pool))) {627 page = alloc_pages(gfp_nested_mask(alloc_flags),628 DEPOT_POOL_ORDER);629 if (page)630 prealloc = page_address(page);631 }632 633 raw_spin_lock_irqsave(&pool_lock, flags);634 printk_deferred_enter();635 636 /* Try to find again, to avoid concurrently inserting duplicates. */637 found = find_stack(bucket, entries, nr_entries, hash, depot_flags);638 if (!found) {639 struct stack_record *new =640 depot_alloc_stack(entries, nr_entries, hash, depot_flags, &prealloc);641 642 if (new) {643 /*644 * This releases the stack record into the bucket and645 * makes it visible to readers in find_stack().646 */647 list_add_rcu(&new->hash_list, bucket);648 found = new;649 }650 }651 652 if (prealloc) {653 /*654 * Either stack depot already contains this stack trace, or655 * depot_alloc_stack() did not consume the preallocated memory.656 * Try to keep the preallocated memory for future.657 */658 depot_keep_new_pool(&prealloc);659 }660 661 printk_deferred_exit();662 raw_spin_unlock_irqrestore(&pool_lock, flags);663exit:664 if (prealloc) {665 /* Stack depot didn't use this memory, free it. */666 free_pages((unsigned long)prealloc, DEPOT_POOL_ORDER);667 }668 if (found)669 handle = found->handle.handle;670 return handle;671}672EXPORT_SYMBOL_GPL(stack_depot_save_flags);673 674depot_stack_handle_t stack_depot_save(unsigned long *entries,675 unsigned int nr_entries,676 gfp_t alloc_flags)677{678 return stack_depot_save_flags(entries, nr_entries, alloc_flags,679 STACK_DEPOT_FLAG_CAN_ALLOC);680}681EXPORT_SYMBOL_GPL(stack_depot_save);682 683struct stack_record *__stack_depot_get_stack_record(depot_stack_handle_t handle)684{685 if (!handle)686 return NULL;687 688 return depot_fetch_stack(handle);689}690 691unsigned int stack_depot_fetch(depot_stack_handle_t handle,692 unsigned long **entries)693{694 struct stack_record *stack;695 696 *entries = NULL;697 /*698 * Let KMSAN know *entries is initialized. This shall prevent false699 * positive reports if instrumented code accesses it.700 */701 kmsan_unpoison_memory(entries, sizeof(*entries));702 703 if (!handle || stack_depot_disabled)704 return 0;705 706 stack = depot_fetch_stack(handle);707 /*708 * Should never be NULL, otherwise this is a use-after-put (or just a709 * corrupt handle).710 */711 if (WARN(!stack, "corrupt handle or use after stack_depot_put()"))712 return 0;713 714 *entries = stack->entries;715 return stack->size;716}717EXPORT_SYMBOL_GPL(stack_depot_fetch);718 719void stack_depot_put(depot_stack_handle_t handle)720{721 struct stack_record *stack;722 723 if (!handle || stack_depot_disabled)724 return;725 726 stack = depot_fetch_stack(handle);727 /*728 * Should always be able to find the stack record, otherwise this is an729 * unbalanced put attempt (or corrupt handle).730 */731 if (WARN(!stack, "corrupt handle or unbalanced stack_depot_put()"))732 return;733 734 if (refcount_dec_and_test(&stack->count))735 depot_free_stack(stack);736}737EXPORT_SYMBOL_GPL(stack_depot_put);738 739void stack_depot_print(depot_stack_handle_t stack)740{741 unsigned long *entries;742 unsigned int nr_entries;743 744 nr_entries = stack_depot_fetch(stack, &entries);745 if (nr_entries > 0)746 stack_trace_print(entries, nr_entries, 0);747}748EXPORT_SYMBOL_GPL(stack_depot_print);749 750int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,751 int spaces)752{753 unsigned long *entries;754 unsigned int nr_entries;755 756 nr_entries = stack_depot_fetch(handle, &entries);757 return nr_entries ? stack_trace_snprint(buf, size, entries, nr_entries,758 spaces) : 0;759}760EXPORT_SYMBOL_GPL(stack_depot_snprint);761 762depot_stack_handle_t __must_check stack_depot_set_extra_bits(763 depot_stack_handle_t handle, unsigned int extra_bits)764{765 union handle_parts parts = { .handle = handle };766 767 /* Don't set extra bits on empty handles. */768 if (!handle)769 return 0;770 771 parts.extra = extra_bits;772 return parts.handle;773}774EXPORT_SYMBOL(stack_depot_set_extra_bits);775 776unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle)777{778 union handle_parts parts = { .handle = handle };779 780 return parts.extra;781}782EXPORT_SYMBOL(stack_depot_get_extra_bits);783 784static int stats_show(struct seq_file *seq, void *v)785{786 /*787 * data race ok: These are just statistics counters, and approximate788 * statistics are ok for debugging.789 */790 seq_printf(seq, "pools: %d\n", data_race(pools_num));791 for (int i = 0; i < DEPOT_COUNTER_COUNT; i++)792 seq_printf(seq, "%s: %ld\n", counter_names[i], data_race(counters[i]));793 794 return 0;795}796DEFINE_SHOW_ATTRIBUTE(stats);797 798static int depot_debugfs_init(void)799{800 struct dentry *dir;801 802 if (stack_depot_disabled)803 return 0;804 805 dir = debugfs_create_dir("stackdepot", NULL);806 debugfs_create_file("stats", 0444, dir, NULL, &stats_fops);807 return 0;808}809late_initcall(depot_debugfs_init);810