diff options
Diffstat (limited to 'include/linux/stackdepot.h')
| -rw-r--r-- | include/linux/stackdepot.h | 152 |
1 files changed, 122 insertions, 30 deletions
diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h index 9ca7798d7a31..e58306783d8e 100644 --- a/include/linux/stackdepot.h +++ b/include/linux/stackdepot.h @@ -1,11 +1,22 @@ /* SPDX-License-Identifier: GPL-2.0-or-later */ /* - * A generic stack depot implementation + * 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> * Copyright (C) 2016 Google, Inc. * - * Based on code by Dmitry Chernenkov. + * Based on the code by Dmitry Chernenkov. */ #ifndef _LINUX_STACKDEPOT_H @@ -14,62 +25,143 @@ #include <linux/gfp.h> typedef u32 depot_stack_handle_t; + /* * 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 -depot_stack_handle_t __stack_depot_save(unsigned long *entries, - unsigned int nr_entries, - unsigned int extra_bits, - gfp_t gfp_flags, bool can_alloc); - /* - * Every user of stack depot has to call stack_depot_init() during its own init - * 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 - * enabled as part of mm_init(), for subsystems where it's known at compile time - * that stack depot will be used. - * - * Another alternative is to call stack_depot_want_early_init(), when the - * decision to use stack depot is taken e.g. when evaluating kernel boot - * parameters, which precedes the enablement point in mm_init(). - * - * stack_depot_init() and stack_depot_want_early_init() can be called regardless - * of CONFIG_STACKDEPOT and are no-op when disabled. The actual save/fetch/print - * functions should only be called from code that makes sure CONFIG_STACKDEPOT - * is enabled. + * Using stack depot requires its initialization, which can be done in 3 ways: + * + * 1. Selecting CONFIG_STACKDEPOT_ALWAYS_INIT. This option is suitable in + * scenarios where it's known at compile time that stack depot will be used. + * Enabling this config makes the kernel initialize stack depot in mm_init(). + * + * 2. Calling stack_depot_request_early_init() during early boot, before + * stack_depot_early_init() in mm_init() completes. For example, this can + * 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 + * regardless of whether CONFIG_STACKDEPOT is enabled and are no-op when this + * config is disabled. The save/fetch/print stack depot functions can only be + * 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 int stack_depot_init(void); -void __init stack_depot_want_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); #else static inline int stack_depot_init(void) { return 0; } -static inline void stack_depot_want_early_init(void) { } +static inline void stack_depot_request_early_init(void) { } static inline int stack_depot_early_init(void) { return 0; } #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, + unsigned int nr_entries, + 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, 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 long **entries); -unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle); +/** + * 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); +/** + * 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); -void stack_depot_print(depot_stack_handle_t stack); +/** + * 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); + +/** + * 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); #endif |