mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-12 13:55:32 +00:00
![Andrey Konovalov](/assets/img/avatar_default.png)
Clean up comments in include/linux/stackdepot.h and lib/stackdepot.c: 1. Rework the initialization comment in stackdepot.h. 2. Rework the header comment in stackdepot.c. 3. Various clean-ups for other comments. Also adjust whitespaces for find_stack and depot_alloc_stack call sites. No functional changes. Link: https://lkml.kernel.org/r/5836231b7954355e2311fc9b5870f697ea8e1f7d.1676063693.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
616 lines
18 KiB
C
616 lines
18 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* Stack depot - a stack trace storage that avoids duplication.
|
|
*
|
|
* Stack depot is intended to be used by subsystems that need to store and
|
|
* later retrieve many potentially duplicated stack traces without wasting
|
|
* memory.
|
|
*
|
|
* For example, KASAN needs to save allocation and free stack traces for each
|
|
* object. Storing two stack traces per object requires a lot of memory (e.g.
|
|
* SLUB_DEBUG needs 256 bytes per object for that). Since allocation and free
|
|
* stack traces often repeat, using stack depot allows to save about 100x space.
|
|
*
|
|
* 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.
|
|
*
|
|
* Stack traces are never removed from stack depot.
|
|
*
|
|
* Author: Alexander Potapenko <glider@google.com>
|
|
* Copyright (C) 2016 Google, Inc.
|
|
*
|
|
* Based on the code by Dmitry Chernenkov.
|
|
*/
|
|
|
|
#define pr_fmt(fmt) "stackdepot: " fmt
|
|
|
|
#include <linux/gfp.h>
|
|
#include <linux/jhash.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/mutex.h>
|
|
#include <linux/percpu.h>
|
|
#include <linux/printk.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/stacktrace.h>
|
|
#include <linux/stackdepot.h>
|
|
#include <linux/string.h>
|
|
#include <linux/types.h>
|
|
#include <linux/memblock.h>
|
|
#include <linux/kasan-enabled.h>
|
|
|
|
#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 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 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 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;
|
|
|
|
/* 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
|
|
|
|
/* 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;
|
|
|
|
/* 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)
|
|
{
|
|
int ret;
|
|
|
|
ret = kstrtobool(str, &stack_depot_disabled);
|
|
if (!ret && stack_depot_disabled) {
|
|
pr_info("disabled\n");
|
|
stack_table = NULL;
|
|
}
|
|
return 0;
|
|
}
|
|
early_param("stack_depot_disable", disable_stack_depot);
|
|
|
|
void __init stack_depot_request_early_init(void)
|
|
{
|
|
/* Too late to request early init now. */
|
|
WARN_ON(__stack_depot_early_init_passed);
|
|
|
|
__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 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 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_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_TABLE_SCALE,
|
|
HASH_EARLY | HASH_ZERO,
|
|
NULL,
|
|
&stack_hash_mask,
|
|
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 -ENOMEM;
|
|
}
|
|
|
|
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)
|
|
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);
|
|
|
|
/* Uses preallocated memory to initialize a new stack depot pool. */
|
|
static void depot_init_pool(void **prealloc)
|
|
{
|
|
/*
|
|
* 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_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 {
|
|
/*
|
|
* 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;
|
|
}
|
|
/*
|
|
* 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_pool_required, 0);
|
|
}
|
|
}
|
|
|
|
/* 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 << DEPOT_STACK_ALIGN);
|
|
|
|
/* 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;
|
|
}
|
|
|
|
/*
|
|
* Move on to the next pool.
|
|
* WRITE_ONCE pairs with potential concurrent read in
|
|
* stack_depot_fetch().
|
|
*/
|
|
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);
|
|
}
|
|
|
|
/* 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.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));
|
|
pool_offset += required_size;
|
|
|
|
return stack;
|
|
}
|
|
|
|
/* Calculates the hash for a stack. */
|
|
static inline u32 hash_stack(unsigned long *entries, unsigned int size)
|
|
{
|
|
return jhash2((u32 *)entries,
|
|
array_size(size, sizeof(*entries)) / sizeof(u32),
|
|
STACK_HASH_SEED);
|
|
}
|
|
|
|
/*
|
|
* 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,
|
|
unsigned int n)
|
|
{
|
|
for ( ; n-- ; u1++, u2++) {
|
|
if (*u1 != *u2)
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/* 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)
|
|
{
|
|
struct stack_record *found;
|
|
|
|
for (found = bucket; found; found = found->next) {
|
|
if (found->hash == hash &&
|
|
found->size == size &&
|
|
!stackdepot_memcmp(entries, found->entries, size))
|
|
return found;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
/**
|
|
* __stack_depot_save - Save a stack trace to stack depot
|
|
*
|
|
* @entries: Pointer to the stack trace
|
|
* @nr_entries: Number of frames in the stack
|
|
* @alloc_flags: Allocation GFP flags
|
|
* @can_alloc: Allocate stack pools (increased chance of failure if false)
|
|
*
|
|
* Saves a stack trace from @entries array of size @nr_entries. If @can_alloc is
|
|
* %true, stack depot can replenish the stack pools in case no space is left
|
|
* (allocates using GFP flags of @alloc_flags). If @can_alloc is %false, avoids
|
|
* any allocations and fails if no space is left to store the stack trace.
|
|
*
|
|
* If the provided stack trace comes from the interrupt context, only the part
|
|
* up to the interrupt entry is saved.
|
|
*
|
|
* 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 for contexts where neither %GFP_ATOMIC nor
|
|
* %GFP_NOWAIT can be used (NMI, raw_spin_lock).
|
|
*
|
|
* Return: 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, bool can_alloc)
|
|
{
|
|
struct stack_record *found = NULL, **bucket;
|
|
union handle_parts retval = { .handle = 0 };
|
|
struct page *page = NULL;
|
|
void *prealloc = NULL;
|
|
unsigned long flags;
|
|
u32 hash;
|
|
|
|
/*
|
|
* If this stack trace is from an interrupt, including anything before
|
|
* interrupt entry usually leads to unbounded stack depot growth.
|
|
*
|
|
* 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);
|
|
|
|
if (unlikely(nr_entries == 0) || stack_depot_disabled)
|
|
goto fast_exit;
|
|
|
|
hash = hash_stack(entries, nr_entries);
|
|
bucket = &stack_table[hash & stack_hash_mask];
|
|
|
|
/*
|
|
* Fast path: look the stack trace up without locking.
|
|
* The smp_load_acquire() here pairs with smp_store_release() to
|
|
* |bucket| below.
|
|
*/
|
|
found = find_stack(smp_load_acquire(bucket), entries, nr_entries, hash);
|
|
if (found)
|
|
goto exit;
|
|
|
|
/*
|
|
* 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_pool_inited| in depot_alloc_stack() and depot_init_pool().
|
|
*/
|
|
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
|
|
* contexts and I/O.
|
|
*/
|
|
alloc_flags &= ~GFP_ZONEMASK;
|
|
alloc_flags &= (GFP_ATOMIC | GFP_KERNEL);
|
|
alloc_flags |= __GFP_NOWARN;
|
|
page = alloc_pages(alloc_flags, DEPOT_POOL_ORDER);
|
|
if (page)
|
|
prealloc = page_address(page);
|
|
}
|
|
|
|
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);
|
|
|
|
if (new) {
|
|
new->next = *bucket;
|
|
/*
|
|
* This smp_store_release() pairs with
|
|
* smp_load_acquire() from |bucket| above.
|
|
*/
|
|
smp_store_release(bucket, new);
|
|
found = new;
|
|
}
|
|
} else if (prealloc) {
|
|
/*
|
|
* Stack depot already contains this stack trace, but let's
|
|
* keep the preallocated memory for the future.
|
|
*/
|
|
depot_init_pool(&prealloc);
|
|
}
|
|
|
|
raw_spin_unlock_irqrestore(&pool_lock, flags);
|
|
exit:
|
|
if (prealloc) {
|
|
/* 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:
|
|
return retval.handle;
|
|
}
|
|
EXPORT_SYMBOL_GPL(__stack_depot_save);
|
|
|
|
/**
|
|
* stack_depot_save - Save a stack trace to stack depot
|
|
*
|
|
* @entries: Pointer to the stack trace
|
|
* @nr_entries: Number of frames in the stack
|
|
* @alloc_flags: Allocation GFP flags
|
|
*
|
|
* Context: Contexts where allocations via alloc_pages() are allowed.
|
|
* See __stack_depot_save() for more details.
|
|
*
|
|
* Return: Handle of the stack trace 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, alloc_flags, true);
|
|
}
|
|
EXPORT_SYMBOL_GPL(stack_depot_save);
|
|
|
|
/**
|
|
* stack_depot_fetch - Fetch a stack trace from stack depot
|
|
*
|
|
* @handle: Stack depot handle returned from stack_depot_save()
|
|
* @entries: Pointer to store the address of the stack trace
|
|
*
|
|
* Return: Number of frames for the fetched stack
|
|
*/
|
|
unsigned int stack_depot_fetch(depot_stack_handle_t handle,
|
|
unsigned long **entries)
|
|
{
|
|
union handle_parts parts = { .handle = handle };
|
|
/*
|
|
* 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.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;
|
|
}
|
|
pool = stack_pools[parts.pool_index];
|
|
if (!pool)
|
|
return 0;
|
|
stack = pool + offset;
|
|
|
|
*entries = stack->entries;
|
|
return stack->size;
|
|
}
|
|
EXPORT_SYMBOL_GPL(stack_depot_fetch);
|
|
|
|
/**
|
|
* stack_depot_print - Print a stack trace from stack depot
|
|
*
|
|
* @stack: Stack depot handle returned from stack_depot_save()
|
|
*/
|
|
void stack_depot_print(depot_stack_handle_t stack)
|
|
{
|
|
unsigned long *entries;
|
|
unsigned int nr_entries;
|
|
|
|
nr_entries = stack_depot_fetch(stack, &entries);
|
|
if (nr_entries > 0)
|
|
stack_trace_print(entries, nr_entries, 0);
|
|
}
|
|
EXPORT_SYMBOL_GPL(stack_depot_print);
|
|
|
|
/**
|
|
* stack_depot_snprint - Print a stack trace from stack depot into a buffer
|
|
*
|
|
* @handle: Stack depot handle 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)
|
|
{
|
|
unsigned long *entries;
|
|
unsigned int nr_entries;
|
|
|
|
nr_entries = stack_depot_fetch(handle, &entries);
|
|
return nr_entries ? stack_trace_snprint(buf, size, entries, nr_entries,
|
|
spaces) : 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(stack_depot_snprint);
|
|
|
|
/**
|
|
* stack_depot_set_extra_bits - Set extra bits in a stack depot handle
|
|
*
|
|
* @handle: Stack depot handle returned from stack_depot_save()
|
|
* @extra_bits: Value to set the extra bits
|
|
*
|
|
* Return: Stack depot handle with extra bits set
|
|
*
|
|
* Stack depot handles have a few unused bits, which can be used for storing
|
|
* user-specific information. These bits are transparent to the stack depot.
|
|
*/
|
|
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);
|
|
|
|
/**
|
|
* stack_depot_get_extra_bits - Retrieve extra bits from a stack depot handle
|
|
*
|
|
* @handle: Stack depot handle with extra bits saved
|
|
*
|
|
* Return: Extra bits retrieved from the stack depot handle
|
|
*/
|
|
unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle)
|
|
{
|
|
union handle_parts parts = { .handle = handle };
|
|
|
|
return parts.extra;
|
|
}
|
|
EXPORT_SYMBOL(stack_depot_get_extra_bits);
|