microsoft
/
WSL2-Linux-Kernel
зеркало из https://github.com/microsoft/WSL2-Linux-Kernel.git
1
0
Форкнуть 0
Код Задачи Пакеты Проекты Релизы Вики Активность

lib/stackdepot: various comments clean-ups 

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>
This commit is contained in:
Andrey Konovalov 2023-02-10 22:16:05 +01:00 коммит произвёл Andrew Morton
Родитель beb3c23c69
Коммит b232b9995a
2 изменённых файлов: 78 добавлений и 78 удалений
Показать статистику Скачать Patch файл Скачать Diff файл Показать все файлы Свернуть все файлы

36
include/linux/stackdepot.h
Просмотреть файл

@ -1,11 +1,11 @@
/* SPDX-License-Identifier: GPL-2.0-or-later */ /* SPDX-License-Identifier: GPL-2.0-or-later */
/* /*
* A generic stack depot implementation * Stack depot - a stack trace storage that avoids duplication.
* *
* Author: Alexander Potapenko <glider@google.com> * Author: Alexander Potapenko <glider@google.com>
* Copyright (C) 2016 Google, Inc. * Copyright (C) 2016 Google, Inc.
* *
* Based on code by Dmitry Chernenkov. * Based on the code by Dmitry Chernenkov.
*/ */
#ifndef _LINUX_STACKDEPOT_H #ifndef _LINUX_STACKDEPOT_H
@ -17,35 +17,37 @@ typedef u32 depot_stack_handle_t;
/* /*
* Number of bits in the handle that stack depot doesn't use. Users may store * Number of bits in the handle that stack depot doesn't use. Users may store
* information in them. * information in them via stack_depot_set/get_extra_bits.
*/ */
#define STACK_DEPOT_EXTRA_BITS 5 #define STACK_DEPOT_EXTRA_BITS 5
/* /*
* Every user of stack depot has to call stack_depot_init() during its own init * Using stack depot requires its initialization, which can be done in 3 ways:
* when it's decided that it will be calling stack_depot_save() later. This is
* recommended for e.g. modules initialized later in the boot process, when
* slab_is_available() is true.
* *
* The alternative is to select STACKDEPOT_ALWAYS_INIT to have stack depot * 1. Selecting CONFIG_STACKDEPOT_ALWAYS_INIT. This option is suitable in
* enabled as part of mm_init(), for subsystems where it's known at compile time * scenarios where it's known at compile time that stack depot will be used.
* that stack depot will be used. * Enabling this config makes the kernel initialize stack depot in mm_init().
* *
* Another alternative is to call stack_depot_request_early_init(), when the * 2. Calling stack_depot_request_early_init() during early boot, before
* decision to use stack depot is taken e.g. when evaluating kernel boot * stack_depot_early_init() in mm_init() completes. For example, this can
* parameters, which precedes the enablement point in mm_init(). * be done when evaluating kernel boot parameters.
*
* 3. Calling stack_depot_init(). Possible after boot is complete. This option
* is recommended for modules initialized later in the boot process, after
* mm_init() completes.
* *
* stack_depot_init() and stack_depot_request_early_init() can be called * stack_depot_init() and stack_depot_request_early_init() can be called
* regardless of CONFIG_STACKDEPOT and are no-op when disabled. The actual * regardless of whether CONFIG_STACKDEPOT is enabled and are no-op when this
* save/fetch/print functions should only be called from code that makes sure * config is disabled. The save/fetch/print stack depot functions can only be
* CONFIG_STACKDEPOT is enabled. * called from the code that makes sure CONFIG_STACKDEPOT is enabled _and_
* initializes stack depot via one of the ways listed above.
*/ */
#ifdef CONFIG_STACKDEPOT #ifdef CONFIG_STACKDEPOT
int stack_depot_init(void); int stack_depot_init(void);
void __init stack_depot_request_early_init(void); void __init stack_depot_request_early_init(void);
/* This is supposed to be called only from mm_init() */ /* Must be only called from mm_init(). */
int __init stack_depot_early_init(void); int __init stack_depot_early_init(void);
#else #else
static inline int stack_depot_init(void) { return 0; } static inline int stack_depot_init(void) { return 0; }

120
lib/stackdepot.c
Просмотреть файл

@ -1,22 +1,26 @@
// SPDX-License-Identifier: GPL-2.0-only // 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 * Stack depot is intended to be used by subsystems that need to store and
* be later presented to the user. For example, KASAN needs to safe alloc and * later retrieve many potentially duplicated stack traces without wasting
* free stacks for each object, but storing two stack traces per object * memory.
* 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 * For example, KASAN needs to save allocation and free stack traces for each
* and free stacks repeat a lot, we save about 100x space. * object. Storing two stack traces per object requires a lot of memory (e.g.
* Stacks are never removed from depot, so we store them contiguously one after * SLUB_DEBUG needs 256 bytes per object for that). Since allocation and free
* another in a contiguous memory allocation. * 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> * Author: Alexander Potapenko <glider@google.com>
* Copyright (C) 2016 Google, Inc. * Copyright (C) 2016 Google, Inc.
* *
* Based on code by Dmitry Chernenkov. * Based on the code by Dmitry Chernenkov.
*/ */
#define pr_fmt(fmt) "stackdepot: " fmt #define pr_fmt(fmt) "stackdepot: " fmt
@ -50,7 +54,7 @@
(((1LL << (DEPOT_POOL_INDEX_BITS)) < DEPOT_POOLS_CAP) ? \ (((1LL << (DEPOT_POOL_INDEX_BITS)) < DEPOT_POOLS_CAP) ? \
(1LL << (DEPOT_POOL_INDEX_BITS)) : DEPOT_POOLS_CAP) (1LL << (DEPOT_POOL_INDEX_BITS)) : DEPOT_POOLS_CAP)
/* The compact structure to store the reference to stacks. */ /* Compact structure that stores a reference to a stack. */
union handle_parts { union handle_parts {
depot_stack_handle_t handle; depot_stack_handle_t handle;
struct { struct {
@ -62,11 +66,11 @@ union handle_parts {
}; };
struct stack_record { struct stack_record {
struct stack_record *next; /* Link in the hashtable */ struct stack_record *next; /* Link in the hash table */
u32 hash; /* Hash in the hastable */ u32 hash; /* Hash in the hash table */
u32 size; /* Number of frames in the stack */ u32 size; /* Number of stored frames */
union handle_parts handle; 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_disabled;
@ -317,7 +321,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
return stack; return stack;
} }
/* Calculate hash for a stack */ /* Calculates the hash for a stack. */
static inline u32 hash_stack(unsigned long *entries, unsigned int size) static inline u32 hash_stack(unsigned long *entries, unsigned int size)
{ {
return jhash2((u32 *)entries, return jhash2((u32 *)entries,
@ -325,9 +329,9 @@ static inline u32 hash_stack(unsigned long *entries, unsigned int size)
STACK_HASH_SEED); STACK_HASH_SEED);
} }
/* Use our own, non-instrumented version of memcmp(). /*
* * Non-instrumented version of memcmp().
* We actually don't care about the order, just the equality. * Does not check the lexicographical order, only the equality.
*/ */
static inline static inline
int stackdepot_memcmp(const unsigned long *u1, const unsigned long *u2, int stackdepot_memcmp(const unsigned long *u1, const unsigned long *u2,
@ -340,7 +344,7 @@ int stackdepot_memcmp(const unsigned long *u1, const unsigned long *u2,
return 0; 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, static inline struct stack_record *find_stack(struct stack_record *bucket,
unsigned long *entries, int size, unsigned long *entries, int size,
u32 hash) u32 hash)
@ -357,27 +361,27 @@ static inline struct stack_record *find_stack(struct stack_record *bucket,
} }
/** /**
* __stack_depot_save - Save a stack trace from an array * __stack_depot_save - Save a stack trace to stack depot
* *
* @entries: Pointer to storage array * @entries: Pointer to the stack trace
* @nr_entries: Size of the storage array * @nr_entries: Number of frames in the stack
* @alloc_flags: Allocation gfp flags * @alloc_flags: Allocation GFP flags
* @can_alloc: Allocate stack pools (increased chance of failure if false) * @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 * Saves a stack trace from @entries array of size @nr_entries. If @can_alloc is
* %true, is allowed to replenish the stack pool in case no space is left * %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 * (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. * any allocations and fails 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 * If the provided stack trace comes from the interrupt context, only the part
* interrupt entry is saved. * up to the interrupt entry is saved.
* *
* Context: Any context, but setting @can_alloc to %false is required if * Context: Any context, but setting @can_alloc to %false is required if
* alloc_pages() cannot be used from the current context. Currently * alloc_pages() cannot be used from the current context. Currently
* this is the case from contexts where neither %GFP_ATOMIC nor * this is the case for contexts where neither %GFP_ATOMIC nor
* %GFP_NOWAIT can be used (NMI, raw_spin_lock). * %GFP_NOWAIT can be used (NMI, raw_spin_lock).
* *
* Return: The handle of the stack struct stored in depot, 0 on failure. * Return: Handle of the stack struct stored in depot, 0 on failure
*/ */
depot_stack_handle_t __stack_depot_save(unsigned long *entries, depot_stack_handle_t __stack_depot_save(unsigned long *entries,
unsigned int nr_entries, unsigned int nr_entries,
@ -392,11 +396,11 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
/* /*
* If this stack trace is from an interrupt, including anything before * 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 * Since use of filter_irq_stacks() is a requirement to ensure stack
* stackdepot can efficiently deduplicate interrupt stacks, always * depot can efficiently deduplicate interrupt stacks, always
* filter_irq_stacks() to simplify all callers' use of stackdepot. * filter_irq_stacks() to simplify all callers' use of stack depot.
*/ */
nr_entries = filter_irq_stacks(entries, nr_entries); nr_entries = filter_irq_stacks(entries, nr_entries);
@ -411,8 +415,7 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
* The smp_load_acquire() here pairs with smp_store_release() to * The smp_load_acquire() here pairs with smp_store_release() to
* |bucket| below. * |bucket| below.
*/ */
found = find_stack(smp_load_acquire(bucket), entries, found = find_stack(smp_load_acquire(bucket), entries, nr_entries, hash);
nr_entries, hash);
if (found) if (found)
goto exit; goto exit;
@ -441,7 +444,8 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
found = find_stack(*bucket, entries, nr_entries, hash); found = find_stack(*bucket, entries, nr_entries, hash);
if (!found) { 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) { if (new) {
new->next = *bucket; new->next = *bucket;
@ -454,8 +458,8 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
} }
} else if (prealloc) { } else if (prealloc) {
/* /*
* We didn't need to store this stack trace, but let's keep * Stack depot already contains this stack trace, but let's
* the preallocated memory for the future. * keep the preallocated memory for the future.
*/ */
depot_init_pool(&prealloc); depot_init_pool(&prealloc);
} }
@ -463,7 +467,7 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
raw_spin_unlock_irqrestore(&pool_lock, flags); raw_spin_unlock_irqrestore(&pool_lock, flags);
exit: exit:
if (prealloc) { if (prealloc) {
/* Nobody used this memory, ok to free it. */ /* Stack depot didn't use this memory, free it. */
free_pages((unsigned long)prealloc, DEPOT_POOL_ORDER); free_pages((unsigned long)prealloc, DEPOT_POOL_ORDER);
} }
if (found) if (found)
@ -474,16 +478,16 @@ fast_exit:
EXPORT_SYMBOL_GPL(__stack_depot_save); EXPORT_SYMBOL_GPL(__stack_depot_save);
/** /**
* stack_depot_save - Save a stack trace from an array * stack_depot_save - Save a stack trace to stack depot
* *
* @entries: Pointer to storage array * @entries: Pointer to the stack trace
* @nr_entries: Size of the storage array * @nr_entries: Number of frames in the stack
* @alloc_flags: Allocation gfp flags * @alloc_flags: Allocation GFP flags
* *
* Context: Contexts where allocations via alloc_pages() are allowed. * Context: Contexts where allocations via alloc_pages() are allowed.
* See __stack_depot_save() for more details. * See __stack_depot_save() for more details.
* *
* Return: The handle of the stack struct stored in depot, 0 on failure. * Return: Handle of the stack trace stored in depot, 0 on failure
*/ */
depot_stack_handle_t stack_depot_save(unsigned long *entries, depot_stack_handle_t stack_depot_save(unsigned long *entries,
unsigned int nr_entries, unsigned int nr_entries,
@ -494,13 +498,12 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries,
EXPORT_SYMBOL_GPL(stack_depot_save); EXPORT_SYMBOL_GPL(stack_depot_save);
/** /**
* stack_depot_fetch - Fetch stack entries from a depot * stack_depot_fetch - Fetch a stack trace from stack depot
* *
* @handle: Stack depot handle which was returned from * @handle: Stack depot handle returned from stack_depot_save()
* stack_depot_save(). * @entries: Pointer to store the address of the stack trace
* @entries: Pointer to store the entries address
* *
* Return: The number of trace entries for this depot. * Return: Number of frames for the fetched stack
*/ */
unsigned int stack_depot_fetch(depot_stack_handle_t handle, unsigned int stack_depot_fetch(depot_stack_handle_t handle,
unsigned long **entries) unsigned long **entries)
@ -535,11 +538,9 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle,
EXPORT_SYMBOL_GPL(stack_depot_fetch); EXPORT_SYMBOL_GPL(stack_depot_fetch);
/** /**
* stack_depot_print - print stack entries from a depot * stack_depot_print - Print a stack trace from stack depot
*
* @stack: Stack depot handle which was returned from
* stack_depot_save().
* *
* @stack: Stack depot handle returned from stack_depot_save()
*/ */
void stack_depot_print(depot_stack_handle_t stack) void stack_depot_print(depot_stack_handle_t stack)
{ {
@ -553,17 +554,14 @@ void stack_depot_print(depot_stack_handle_t stack)
EXPORT_SYMBOL_GPL(stack_depot_print); EXPORT_SYMBOL_GPL(stack_depot_print);
/** /**
* stack_depot_snprint - print stack entries from a depot into a buffer * stack_depot_snprint - Print a stack trace from stack depot into a buffer
* *
* @handle: Stack depot handle which was returned from * @handle: Stack depot handle returned from stack_depot_save()
* stack_depot_save().
* @buf: Pointer to the print buffer * @buf: Pointer to the print buffer
*
* @size: Size of the print buffer * @size: Size of the print buffer
*
* @spaces: Number of leading spaces to print * @spaces: Number of leading spaces to print
* *
* Return: Number of bytes printed. * Return: Number of bytes printed
*/ */
int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size, int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
int spaces) int spaces)