1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3  * A generic stack depot implementation
4  *
5  * Author: Alexander Potapenko <glider@google.com>
6  * Copyright (C) 2016 Google, Inc.
7  *
8  * Based on code by Dmitry Chernenkov.
9  */
10 
11 #ifndef _LINUX_STACKDEPOT_H
12 #define _LINUX_STACKDEPOT_H
13 
14 #include <linux/gfp.h>
15 
16 typedef u32 depot_stack_handle_t;
17 /*
18  * Number of bits in the handle that stack depot doesn't use. Users may store
19  * information in them.
20  */
21 #define STACK_DEPOT_EXTRA_BITS 5
22 
23 depot_stack_handle_t __stack_depot_save(unsigned long *entries,
24 					unsigned int nr_entries,
25 					unsigned int extra_bits,
26 					gfp_t gfp_flags, bool can_alloc);
27 
28 /*
29  * Every user of stack depot has to call stack_depot_init() during its own init
30  * when it's decided that it will be calling stack_depot_save() later. This is
31  * recommended for e.g. modules initialized later in the boot process, when
32  * slab_is_available() is true.
33  *
34  * The alternative is to select STACKDEPOT_ALWAYS_INIT to have stack depot
35  * enabled as part of mm_init(), for subsystems where it's known at compile time
36  * that stack depot will be used.
37  *
38  * Another alternative is to call stack_depot_want_early_init(), when the
39  * decision to use stack depot is taken e.g. when evaluating kernel boot
40  * parameters, which precedes the enablement point in mm_init().
41  *
42  * stack_depot_init() and stack_depot_want_early_init() can be called regardless
43  * of CONFIG_STACKDEPOT and are no-op when disabled. The actual save/fetch/print
44  * functions should only be called from code that makes sure CONFIG_STACKDEPOT
45  * is enabled.
46  */
47 #ifdef CONFIG_STACKDEPOT
48 int stack_depot_init(void);
49 
50 void __init stack_depot_want_early_init(void);
51 
52 /* This is supposed to be called only from mm_init() */
53 int __init stack_depot_early_init(void);
54 #else
stack_depot_init(void)55 static inline int stack_depot_init(void) { return 0; }
56 
stack_depot_want_early_init(void)57 static inline void stack_depot_want_early_init(void) { }
58 
stack_depot_early_init(void)59 static inline int stack_depot_early_init(void)	{ return 0; }
60 #endif
61 
62 depot_stack_handle_t stack_depot_save(unsigned long *entries,
63 				      unsigned int nr_entries, gfp_t gfp_flags);
64 
65 unsigned int stack_depot_fetch(depot_stack_handle_t handle,
66 			       unsigned long **entries);
67 
68 unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle);
69 
70 int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
71 		       int spaces);
72 
73 void stack_depot_print(depot_stack_handle_t stack);
74 
75 #endif
76