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lib/stackdepot: move documentation comments to stackdepot.h

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Move all interface- and usage-related documentation comments to
include/linux/stackdepot.h.

It makes sense to have them in the header where they are available to
the interface users.

[akpm@linux-foundation.org: grammar fix, per Alexander]
Link: https://lkml.kernel.org/r/fbfee41495b306dd8881f9b1c1b80999c885e82f.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 22:16:06 +01:00 committed by Andrew Morton
parent b232b9995a
commit 0621d160f1
2 changed files with 87 additions and 87 deletions
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87
include/linux/stackdepot.h
View File

@ -2,6 +2,17 @@
/* /*
* Stack depot - a stack trace storage that avoids duplication. * 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.
*
* Stack traces are never removed from the stack depot.
*
* Author: Alexander Potapenko <glider@google.com> * Author: Alexander Potapenko <glider@google.com>
* Copyright (C) 2016 Google, Inc. * Copyright (C) 2016 Google, Inc.
* *
@ -57,24 +68,100 @@ static inline void stack_depot_request_early_init(void) { }
static inline int stack_depot_early_init(void) { return 0; } static inline int stack_depot_early_init(void) { return 0; }
#endif #endif
/**
* __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, depot_stack_handle_t __stack_depot_save(unsigned long *entries,
unsigned int nr_entries, unsigned int nr_entries,
gfp_t gfp_flags, bool can_alloc); gfp_t gfp_flags, bool can_alloc);
/**
* 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, depot_stack_handle_t stack_depot_save(unsigned long *entries,
unsigned int nr_entries, gfp_t gfp_flags); unsigned int nr_entries, gfp_t gfp_flags);
/**
* 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 int stack_depot_fetch(depot_stack_handle_t handle,
unsigned long **entries); unsigned long **entries);
/**
* 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); void stack_depot_print(depot_stack_handle_t stack);
/**
* 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 stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
int spaces); int spaces);
/**
* 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 __must_check stack_depot_set_extra_bits(
depot_stack_handle_t handle, unsigned int extra_bits); depot_stack_handle_t handle, unsigned int 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); unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle);
#endif #endif

87
lib/stackdepot.c
View File

@ -2,21 +2,10 @@
/* /*
* Stack depot - a stack trace storage that avoids duplication. * 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 * Internally, stack depot maintains a hash table of unique stacktraces. The
* stack traces themselves are stored contiguously one after another in a set * stack traces themselves are stored contiguously one after another in a set
* of separate page allocations. * 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.
* *
@ -360,29 +349,6 @@ static inline struct stack_record *find_stack(struct stack_record *bucket,
return NULL; 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, depot_stack_handle_t __stack_depot_save(unsigned long *entries,
unsigned int nr_entries, unsigned int nr_entries,
gfp_t alloc_flags, bool can_alloc) gfp_t alloc_flags, bool can_alloc)
@ -477,18 +443,6 @@ fast_exit:
} }
EXPORT_SYMBOL_GPL(__stack_depot_save); 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, depot_stack_handle_t stack_depot_save(unsigned long *entries,
unsigned int nr_entries, unsigned int nr_entries,
gfp_t alloc_flags) gfp_t alloc_flags)
@ -497,14 +451,6 @@ 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 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 int stack_depot_fetch(depot_stack_handle_t handle,
unsigned long **entries) unsigned long **entries)
{ {
@ -537,11 +483,6 @@ 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 a stack trace from stack depot
*
* @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)
{ {
unsigned long *entries; unsigned long *entries;
@ -553,16 +494,6 @@ 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 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 stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
int spaces) int spaces)
{ {
@ -575,17 +506,6 @@ int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
} }
EXPORT_SYMBOL_GPL(stack_depot_snprint); 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 __must_check stack_depot_set_extra_bits(
depot_stack_handle_t handle, unsigned int extra_bits) depot_stack_handle_t handle, unsigned int extra_bits)
{ {
@ -600,13 +520,6 @@ depot_stack_handle_t __must_check stack_depot_set_extra_bits(
} }
EXPORT_SYMBOL(stack_depot_set_extra_bits); 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) unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle)
{ {
union handle_parts parts = { .handle = handle }; union handle_parts parts = { .handle = handle };