// SPDX-License-Identifier: GPL-2.0-only
/*
- * Generic stack depot for storing stack traces.
+ * Stack depot - a stack trace storage that avoids duplication.
*
- * Some debugging tools need to save stack traces of certain events which can
- * be later presented to the user. For example, KASAN needs to safe alloc and
- * free stacks for each object, but storing two stack traces per object
- * requires too much memory (e.g. SLUB_DEBUG needs 256 bytes per object for
- * that).
- *
- * Instead, stack depot maintains a hashtable of unique stacktraces. Since alloc
- * and free stacks repeat a lot, we save about 100x space.
- * Stacks are never removed from depot, so we store them contiguously one after
- * another in a contiguous memory allocation.
+ * Internally, stack depot maintains a hash table of unique stacktraces. The
+ * stack traces themselves are stored contiguously one after another in a set
+ * of separate page allocations.
*
* Author: Alexander Potapenko <glider@google.com>
* Copyright (C) 2016 Google, Inc.
*
- * Based on code by Dmitry Chernenkov.
+ * Based on the code by Dmitry Chernenkov.
*/
#define pr_fmt(fmt) "stackdepot: " fmt
#include <linux/memblock.h>
#include <linux/kasan-enabled.h>
-#define DEPOT_STACK_BITS (sizeof(depot_stack_handle_t) * 8)
-
-#define STACK_ALLOC_NULL_PROTECTION_BITS 1
-#define STACK_ALLOC_ORDER 2 /* 'Slab' size order for stack depot, 4 pages */
-#define STACK_ALLOC_SIZE (1LL << (PAGE_SHIFT + STACK_ALLOC_ORDER))
-#define STACK_ALLOC_ALIGN 4
-#define STACK_ALLOC_OFFSET_BITS (STACK_ALLOC_ORDER + PAGE_SHIFT - \
- STACK_ALLOC_ALIGN)
-#define STACK_ALLOC_INDEX_BITS (DEPOT_STACK_BITS - \
- STACK_ALLOC_NULL_PROTECTION_BITS - \
- STACK_ALLOC_OFFSET_BITS - STACK_DEPOT_EXTRA_BITS)
-#define STACK_ALLOC_SLABS_CAP 8192
-#define STACK_ALLOC_MAX_SLABS \
- (((1LL << (STACK_ALLOC_INDEX_BITS)) < STACK_ALLOC_SLABS_CAP) ? \
- (1LL << (STACK_ALLOC_INDEX_BITS)) : STACK_ALLOC_SLABS_CAP)
-
-/* The compact structure to store the reference to stacks. */
+#define DEPOT_HANDLE_BITS (sizeof(depot_stack_handle_t) * 8)
+
+#define DEPOT_VALID_BITS 1
+#define DEPOT_POOL_ORDER 2 /* Pool size order, 4 pages */
+#define DEPOT_POOL_SIZE (1LL << (PAGE_SHIFT + DEPOT_POOL_ORDER))
+#define DEPOT_STACK_ALIGN 4
+#define DEPOT_OFFSET_BITS (DEPOT_POOL_ORDER + PAGE_SHIFT - DEPOT_STACK_ALIGN)
+#define DEPOT_POOL_INDEX_BITS (DEPOT_HANDLE_BITS - DEPOT_VALID_BITS - \
+ DEPOT_OFFSET_BITS - STACK_DEPOT_EXTRA_BITS)
+#define DEPOT_POOLS_CAP 8192
+#define DEPOT_MAX_POOLS \
+ (((1LL << (DEPOT_POOL_INDEX_BITS)) < DEPOT_POOLS_CAP) ? \
+ (1LL << (DEPOT_POOL_INDEX_BITS)) : DEPOT_POOLS_CAP)
+
+/* Compact structure that stores a reference to a stack. */
union handle_parts {
depot_stack_handle_t handle;
struct {
- u32 slabindex : STACK_ALLOC_INDEX_BITS;
- u32 offset : STACK_ALLOC_OFFSET_BITS;
- u32 valid : STACK_ALLOC_NULL_PROTECTION_BITS;
- u32 extra : STACK_DEPOT_EXTRA_BITS;
+ u32 pool_index : DEPOT_POOL_INDEX_BITS;
+ u32 offset : DEPOT_OFFSET_BITS;
+ u32 valid : DEPOT_VALID_BITS;
+ u32 extra : STACK_DEPOT_EXTRA_BITS;
};
};
struct stack_record {
- struct stack_record *next; /* Link in the hashtable */
- u32 hash; /* Hash in the hastable */
- u32 size; /* Number of frames in the stack */
+ struct stack_record *next; /* Link in the hash table */
+ u32 hash; /* Hash in the hash table */
+ u32 size; /* Number of stored frames */
union handle_parts handle;
- unsigned long entries[]; /* Variable-sized array of entries. */
+ unsigned long entries[]; /* Variable-sized array of frames */
};
static bool stack_depot_disabled;
static bool __stack_depot_early_init_requested __initdata = IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT);
static bool __stack_depot_early_init_passed __initdata;
-static void *stack_slabs[STACK_ALLOC_MAX_SLABS];
-
-static int depot_index;
-static int next_slab_inited;
-static size_t depot_offset;
-static DEFINE_RAW_SPINLOCK(depot_lock);
-
-/* one hash table bucket entry per 16kB of memory */
-#define STACK_HASH_SCALE 14
-/* limited between 4k and 1M buckets */
-#define STACK_HASH_ORDER_MIN 12
-#define STACK_HASH_ORDER_MAX 20
+/* Use one hash table bucket per 16 KB of memory. */
+#define STACK_HASH_TABLE_SCALE 14
+/* Limit the number of buckets between 4K and 1M. */
+#define STACK_BUCKET_NUMBER_ORDER_MIN 12
+#define STACK_BUCKET_NUMBER_ORDER_MAX 20
+/* Initial seed for jhash2. */
#define STACK_HASH_SEED 0x9747b28c
-static unsigned int stack_hash_order;
+/* Hash table of pointers to stored stack traces. */
+static struct stack_record **stack_table;
+/* Fixed order of the number of table buckets. Used when KASAN is enabled. */
+static unsigned int stack_bucket_number_order;
+/* Hash mask for indexing the table. */
static unsigned int stack_hash_mask;
-static struct stack_record **stack_table;
+/* Array of memory regions that store stack traces. */
+static void *stack_pools[DEPOT_MAX_POOLS];
+/* Currently used pool in stack_pools. */
+static int pool_index;
+/* Offset to the unused space in the currently used pool. */
+static size_t pool_offset;
+/* Lock that protects the variables above. */
+static DEFINE_RAW_SPINLOCK(pool_lock);
+/*
+ * Stack depot tries to keep an extra pool allocated even before it runs out
+ * of space in the currently used pool.
+ * This flag marks that this next extra pool needs to be allocated and
+ * initialized. It has the value 0 when either the next pool is not yet
+ * initialized or the limit on the number of pools is reached.
+ */
+static int next_pool_required = 1;
static int __init disable_stack_depot(char *str)
{
__stack_depot_early_init_requested = true;
}
+/* Allocates a hash table via memblock. Can only be used during early boot. */
int __init stack_depot_early_init(void)
{
unsigned long entries = 0;
- /* This is supposed to be called only once, from mm_init() */
+ /* This function must be called only once, from mm_init(). */
if (WARN_ON(__stack_depot_early_init_passed))
return 0;
-
__stack_depot_early_init_passed = true;
- if (kasan_enabled() && !stack_hash_order)
- stack_hash_order = STACK_HASH_ORDER_MAX;
+ /*
+ * If KASAN is enabled, use the maximum order: KASAN is frequently used
+ * in fuzzing scenarios, which leads to a large number of different
+ * stack traces being stored in stack depot.
+ */
+ if (kasan_enabled() && !stack_bucket_number_order)
+ stack_bucket_number_order = STACK_BUCKET_NUMBER_ORDER_MAX;
if (!__stack_depot_early_init_requested || stack_depot_disabled)
return 0;
- if (stack_hash_order)
- entries = 1UL << stack_hash_order;
+ /*
+ * If stack_bucket_number_order is not set, leave entries as 0 to rely
+ * on the automatic calculations performed by alloc_large_system_hash.
+ */
+ if (stack_bucket_number_order)
+ entries = 1UL << stack_bucket_number_order;
+ pr_info("allocating hash table via alloc_large_system_hash\n");
stack_table = alloc_large_system_hash("stackdepot",
sizeof(struct stack_record *),
entries,
- STACK_HASH_SCALE,
+ STACK_HASH_TABLE_SCALE,
HASH_EARLY | HASH_ZERO,
NULL,
&stack_hash_mask,
- 1UL << STACK_HASH_ORDER_MIN,
- 1UL << STACK_HASH_ORDER_MAX);
-
+ 1UL << STACK_BUCKET_NUMBER_ORDER_MIN,
+ 1UL << STACK_BUCKET_NUMBER_ORDER_MAX);
if (!stack_table) {
pr_err("hash table allocation failed, disabling\n");
stack_depot_disabled = true;
return 0;
}
+/* Allocates a hash table via kvcalloc. Can be used after boot. */
int stack_depot_init(void)
{
static DEFINE_MUTEX(stack_depot_init_mutex);
+ unsigned long entries;
int ret = 0;
mutex_lock(&stack_depot_init_mutex);
- if (!stack_depot_disabled && !stack_table) {
- unsigned long entries;
- int scale = STACK_HASH_SCALE;
-
- if (stack_hash_order) {
- entries = 1UL << stack_hash_order;
- } else {
- entries = nr_free_buffer_pages();
- entries = roundup_pow_of_two(entries);
-
- if (scale > PAGE_SHIFT)
- entries >>= (scale - PAGE_SHIFT);
- else
- entries <<= (PAGE_SHIFT - scale);
- }
- if (entries < 1UL << STACK_HASH_ORDER_MIN)
- entries = 1UL << STACK_HASH_ORDER_MIN;
- if (entries > 1UL << STACK_HASH_ORDER_MAX)
- entries = 1UL << STACK_HASH_ORDER_MAX;
-
- pr_info("allocating hash table of %lu entries with kvcalloc\n",
- entries);
- stack_table = kvcalloc(entries, sizeof(struct stack_record *), GFP_KERNEL);
- if (!stack_table) {
- pr_err("hash table allocation failed, disabling\n");
- stack_depot_disabled = true;
- ret = -ENOMEM;
- }
- stack_hash_mask = entries - 1;
+ if (stack_depot_disabled || stack_table)
+ goto out_unlock;
+
+ /*
+ * Similarly to stack_depot_early_init, use stack_bucket_number_order
+ * if assigned, and rely on automatic scaling otherwise.
+ */
+ if (stack_bucket_number_order) {
+ entries = 1UL << stack_bucket_number_order;
+ } else {
+ int scale = STACK_HASH_TABLE_SCALE;
+
+ entries = nr_free_buffer_pages();
+ entries = roundup_pow_of_two(entries);
+
+ if (scale > PAGE_SHIFT)
+ entries >>= (scale - PAGE_SHIFT);
+ else
+ entries <<= (PAGE_SHIFT - scale);
}
+
+ if (entries < 1UL << STACK_BUCKET_NUMBER_ORDER_MIN)
+ entries = 1UL << STACK_BUCKET_NUMBER_ORDER_MIN;
+ if (entries > 1UL << STACK_BUCKET_NUMBER_ORDER_MAX)
+ entries = 1UL << STACK_BUCKET_NUMBER_ORDER_MAX;
+
+ pr_info("allocating hash table of %lu entries via kvcalloc\n", entries);
+ stack_table = kvcalloc(entries, sizeof(struct stack_record *), GFP_KERNEL);
+ if (!stack_table) {
+ pr_err("hash table allocation failed, disabling\n");
+ stack_depot_disabled = true;
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+ stack_hash_mask = entries - 1;
+
+out_unlock:
mutex_unlock(&stack_depot_init_mutex);
+
return ret;
}
EXPORT_SYMBOL_GPL(stack_depot_init);
-static bool init_stack_slab(void **prealloc)
+/* Uses preallocated memory to initialize a new stack depot pool. */
+static void depot_init_pool(void **prealloc)
{
- if (!*prealloc)
- return false;
/*
- * This smp_load_acquire() pairs with smp_store_release() to
- * |next_slab_inited| below and in depot_alloc_stack().
+ * If the next pool is already initialized or the maximum number of
+ * pools is reached, do not use the preallocated memory.
+ * smp_load_acquire() here pairs with smp_store_release() below and
+ * in depot_alloc_stack().
*/
- if (smp_load_acquire(&next_slab_inited))
- return true;
- if (stack_slabs[depot_index] == NULL) {
- stack_slabs[depot_index] = *prealloc;
+ if (!smp_load_acquire(&next_pool_required))
+ return;
+
+ /* Check if the current pool is not yet allocated. */
+ if (stack_pools[pool_index] == NULL) {
+ /* Use the preallocated memory for the current pool. */
+ stack_pools[pool_index] = *prealloc;
*prealloc = NULL;
} else {
- /* If this is the last depot slab, do not touch the next one. */
- if (depot_index + 1 < STACK_ALLOC_MAX_SLABS) {
- stack_slabs[depot_index + 1] = *prealloc;
+ /*
+ * Otherwise, use the preallocated memory for the next pool
+ * as long as we do not exceed the maximum number of pools.
+ */
+ if (pool_index + 1 < DEPOT_MAX_POOLS) {
+ stack_pools[pool_index + 1] = *prealloc;
*prealloc = NULL;
}
/*
- * This smp_store_release pairs with smp_load_acquire() from
- * |next_slab_inited| above and in stack_depot_save().
+ * At this point, either the next pool is initialized or the
+ * maximum number of pools is reached. In either case, take
+ * note that initializing another pool is not required.
+ * This smp_store_release pairs with smp_load_acquire() above
+ * and in stack_depot_save().
*/
- smp_store_release(&next_slab_inited, 1);
+ smp_store_release(&next_pool_required, 0);
}
- return true;
}
-/* Allocation of a new stack in raw storage */
+/* Allocates a new stack in a stack depot pool. */
static struct stack_record *
depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
{
struct stack_record *stack;
size_t required_size = struct_size(stack, entries, size);
- required_size = ALIGN(required_size, 1 << STACK_ALLOC_ALIGN);
+ required_size = ALIGN(required_size, 1 << DEPOT_STACK_ALIGN);
- if (unlikely(depot_offset + required_size > STACK_ALLOC_SIZE)) {
- if (unlikely(depot_index + 1 >= STACK_ALLOC_MAX_SLABS)) {
+ /* Check if there is not enough space in the current pool. */
+ if (unlikely(pool_offset + required_size > DEPOT_POOL_SIZE)) {
+ /* Bail out if we reached the pool limit. */
+ if (unlikely(pool_index + 1 >= DEPOT_MAX_POOLS)) {
WARN_ONCE(1, "Stack depot reached limit capacity");
return NULL;
}
- depot_index++;
- depot_offset = 0;
+
/*
- * smp_store_release() here pairs with smp_load_acquire() from
- * |next_slab_inited| in stack_depot_save() and
- * init_stack_slab().
+ * Move on to the next pool.
+ * WRITE_ONCE pairs with potential concurrent read in
+ * stack_depot_fetch().
*/
- if (depot_index + 1 < STACK_ALLOC_MAX_SLABS)
- smp_store_release(&next_slab_inited, 0);
+ WRITE_ONCE(pool_index, pool_index + 1);
+ pool_offset = 0;
+ /*
+ * If the maximum number of pools is not reached, take note
+ * that the next pool needs to initialized.
+ * smp_store_release() here pairs with smp_load_acquire() in
+ * stack_depot_save() and depot_init_pool().
+ */
+ if (pool_index + 1 < DEPOT_MAX_POOLS)
+ smp_store_release(&next_pool_required, 1);
}
- init_stack_slab(prealloc);
- if (stack_slabs[depot_index] == NULL)
- return NULL;
- stack = stack_slabs[depot_index] + depot_offset;
+ /* Assign the preallocated memory to a pool if required. */
+ if (*prealloc)
+ depot_init_pool(prealloc);
+ /* Check if we have a pool to save the stack trace. */
+ if (stack_pools[pool_index] == NULL)
+ return NULL;
+
+ /* Save the stack trace. */
+ stack = stack_pools[pool_index] + pool_offset;
stack->hash = hash;
stack->size = size;
- stack->handle.slabindex = depot_index;
- stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN;
+ stack->handle.pool_index = pool_index;
+ stack->handle.offset = pool_offset >> DEPOT_STACK_ALIGN;
stack->handle.valid = 1;
stack->handle.extra = 0;
memcpy(stack->entries, entries, flex_array_size(stack, entries, size));
- depot_offset += required_size;
+ pool_offset += required_size;
return stack;
}
-/* Calculate hash for a stack */
+/* Calculates the hash for a stack. */
static inline u32 hash_stack(unsigned long *entries, unsigned int size)
{
return jhash2((u32 *)entries,
STACK_HASH_SEED);
}
-/* Use our own, non-instrumented version of memcmp().
- *
- * We actually don't care about the order, just the equality.
+/*
+ * Non-instrumented version of memcmp().
+ * Does not check the lexicographical order, only the equality.
*/
static inline
int stackdepot_memcmp(const unsigned long *u1, const unsigned long *u2,
return 0;
}
-/* Find a stack that is equal to the one stored in entries in the hash */
+/* Finds a stack in a bucket of the hash table. */
static inline struct stack_record *find_stack(struct stack_record *bucket,
unsigned long *entries, int size,
u32 hash)
return NULL;
}
-/**
- * __stack_depot_save - Save a stack trace from an array
- *
- * @entries: Pointer to storage array
- * @nr_entries: Size of the storage array
- * @extra_bits: Flags to store in unused bits of depot_stack_handle_t
- * @alloc_flags: Allocation gfp flags
- * @can_alloc: Allocate stack slabs (increased chance of failure if false)
- *
- * Saves a stack trace from @entries array of size @nr_entries. If @can_alloc is
- * %true, is allowed to replenish the stack slab pool in case no space is left
- * (allocates using GFP flags of @alloc_flags). If @can_alloc is %false, avoids
- * any allocations and will fail if no space is left to store the stack trace.
- *
- * If the stack trace in @entries is from an interrupt, only the portion up to
- * interrupt entry is saved.
- *
- * Additional opaque flags can be passed in @extra_bits, stored in the unused
- * bits of the stack handle, and retrieved using stack_depot_get_extra_bits()
- * without calling stack_depot_fetch().
- *
- * Context: Any context, but setting @can_alloc to %false is required if
- * alloc_pages() cannot be used from the current context. Currently
- * this is the case from contexts where neither %GFP_ATOMIC nor
- * %GFP_NOWAIT can be used (NMI, raw_spin_lock).
- *
- * Return: The handle of the stack struct stored in depot, 0 on failure.
- */
depot_stack_handle_t __stack_depot_save(unsigned long *entries,
unsigned int nr_entries,
- unsigned int extra_bits,
gfp_t alloc_flags, bool can_alloc)
{
struct stack_record *found = NULL, **bucket;
/*
* If this stack trace is from an interrupt, including anything before
- * interrupt entry usually leads to unbounded stackdepot growth.
+ * interrupt entry usually leads to unbounded stack depot growth.
*
- * Because use of filter_irq_stacks() is a requirement to ensure
- * stackdepot can efficiently deduplicate interrupt stacks, always
- * filter_irq_stacks() to simplify all callers' use of stackdepot.
+ * Since use of filter_irq_stacks() is a requirement to ensure stack
+ * depot can efficiently deduplicate interrupt stacks, always
+ * filter_irq_stacks() to simplify all callers' use of stack depot.
*/
nr_entries = filter_irq_stacks(entries, nr_entries);
* The smp_load_acquire() here pairs with smp_store_release() to
* |bucket| below.
*/
- found = find_stack(smp_load_acquire(bucket), entries,
- nr_entries, hash);
+ found = find_stack(smp_load_acquire(bucket), entries, nr_entries, hash);
if (found)
goto exit;
/*
- * Check if the current or the next stack slab need to be initialized.
- * If so, allocate the memory - we won't be able to do that under the
- * lock.
+ * Check if another stack pool needs to be initialized. If so, allocate
+ * the memory now - we won't be able to do that under the lock.
*
* The smp_load_acquire() here pairs with smp_store_release() to
- * |next_slab_inited| in depot_alloc_stack() and init_stack_slab().
+ * |next_pool_inited| in depot_alloc_stack() and depot_init_pool().
*/
- if (unlikely(can_alloc && !smp_load_acquire(&next_slab_inited))) {
+ if (unlikely(can_alloc && smp_load_acquire(&next_pool_required))) {
/*
* Zero out zone modifiers, as we don't have specific zone
* requirements. Keep the flags related to allocation in atomic
alloc_flags &= ~GFP_ZONEMASK;
alloc_flags &= (GFP_ATOMIC | GFP_KERNEL);
alloc_flags |= __GFP_NOWARN;
- page = alloc_pages(alloc_flags, STACK_ALLOC_ORDER);
+ page = alloc_pages(alloc_flags, DEPOT_POOL_ORDER);
if (page)
prealloc = page_address(page);
}
- raw_spin_lock_irqsave(&depot_lock, flags);
+ raw_spin_lock_irqsave(&pool_lock, flags);
found = find_stack(*bucket, entries, nr_entries, hash);
if (!found) {
- struct stack_record *new = depot_alloc_stack(entries, nr_entries, hash, &prealloc);
+ struct stack_record *new =
+ depot_alloc_stack(entries, nr_entries, hash, &prealloc);
if (new) {
new->next = *bucket;
}
} else if (prealloc) {
/*
- * We didn't need to store this stack trace, but let's keep
- * the preallocated memory for the future.
+ * Stack depot already contains this stack trace, but let's
+ * keep the preallocated memory for the future.
*/
- WARN_ON(!init_stack_slab(&prealloc));
+ depot_init_pool(&prealloc);
}
- raw_spin_unlock_irqrestore(&depot_lock, flags);
+ raw_spin_unlock_irqrestore(&pool_lock, flags);
exit:
if (prealloc) {
- /* Nobody used this memory, ok to free it. */
- free_pages((unsigned long)prealloc, STACK_ALLOC_ORDER);
+ /* Stack depot didn't use this memory, free it. */
+ free_pages((unsigned long)prealloc, DEPOT_POOL_ORDER);
}
if (found)
retval.handle = found->handle.handle;
fast_exit:
- retval.extra = extra_bits;
-
return retval.handle;
}
EXPORT_SYMBOL_GPL(__stack_depot_save);
-/**
- * stack_depot_save - Save a stack trace from an array
- *
- * @entries: Pointer to storage array
- * @nr_entries: Size of the storage array
- * @alloc_flags: Allocation gfp flags
- *
- * Context: Contexts where allocations via alloc_pages() are allowed.
- * See __stack_depot_save() for more details.
- *
- * Return: The handle of the stack struct stored in depot, 0 on failure.
- */
depot_stack_handle_t stack_depot_save(unsigned long *entries,
unsigned int nr_entries,
gfp_t alloc_flags)
{
- return __stack_depot_save(entries, nr_entries, 0, alloc_flags, true);
+ return __stack_depot_save(entries, nr_entries, alloc_flags, true);
}
EXPORT_SYMBOL_GPL(stack_depot_save);
-/**
- * stack_depot_fetch - Fetch stack entries from a depot
- *
- * @handle: Stack depot handle which was returned from
- * stack_depot_save().
- * @entries: Pointer to store the entries address
- *
- * Return: The number of trace entries for this depot.
- */
unsigned int stack_depot_fetch(depot_stack_handle_t handle,
unsigned long **entries)
{
union handle_parts parts = { .handle = handle };
- void *slab;
- size_t offset = parts.offset << STACK_ALLOC_ALIGN;
+ /*
+ * READ_ONCE pairs with potential concurrent write in
+ * depot_alloc_stack.
+ */
+ int pool_index_cached = READ_ONCE(pool_index);
+ void *pool;
+ size_t offset = parts.offset << DEPOT_STACK_ALIGN;
struct stack_record *stack;
*entries = NULL;
if (!handle)
return 0;
- if (parts.slabindex > depot_index) {
- WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n",
- parts.slabindex, depot_index, handle);
+ if (parts.pool_index > pool_index_cached) {
+ WARN(1, "pool index %d out of bounds (%d) for stack id %08x\n",
+ parts.pool_index, pool_index_cached, handle);
return 0;
}
- slab = stack_slabs[parts.slabindex];
- if (!slab)
+ pool = stack_pools[parts.pool_index];
+ if (!pool)
return 0;
- stack = slab + offset;
+ stack = pool + offset;
*entries = stack->entries;
return stack->size;
}
EXPORT_SYMBOL_GPL(stack_depot_fetch);
-/**
- * stack_depot_print - print stack entries from a depot
- *
- * @stack: Stack depot handle which was returned from
- * stack_depot_save().
- *
- */
void stack_depot_print(depot_stack_handle_t stack)
{
unsigned long *entries;
}
EXPORT_SYMBOL_GPL(stack_depot_print);
-/**
- * stack_depot_snprint - print stack entries from a depot into a buffer
- *
- * @handle: Stack depot handle which was returned from
- * stack_depot_save().
- * @buf: Pointer to the print buffer
- *
- * @size: Size of the print buffer
- *
- * @spaces: Number of leading spaces to print
- *
- * Return: Number of bytes printed.
- */
int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
int spaces)
{
}
EXPORT_SYMBOL_GPL(stack_depot_snprint);
+depot_stack_handle_t __must_check stack_depot_set_extra_bits(
+ depot_stack_handle_t handle, unsigned int extra_bits)
+{
+ union handle_parts parts = { .handle = handle };
+
+ /* Don't set extra bits on empty handles. */
+ if (!handle)
+ return 0;
+
+ parts.extra = extra_bits;
+ return parts.handle;
+}
+EXPORT_SYMBOL(stack_depot_set_extra_bits);
+
unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle)
{
union handle_parts parts = { .handle = handle };
projects / linux-block.git / blobdiff