1 // SPDX-License-Identifier: GPL-2.0
3 * This file contains common tag-based KASAN code.
5 * Copyright (c) 2018 Google, Inc.
6 * Copyright (c) 2020 Google, Inc.
9 #include <linux/atomic.h>
10 #include <linux/init.h>
11 #include <linux/kasan.h>
12 #include <linux/kernel.h>
13 #include <linux/memblock.h>
14 #include <linux/memory.h>
16 #include <linux/static_key.h>
17 #include <linux/string.h>
18 #include <linux/types.h>
23 #define KASAN_STACK_RING_SIZE_DEFAULT (32 << 10)
25 enum kasan_arg_stacktrace {
26 KASAN_ARG_STACKTRACE_DEFAULT,
27 KASAN_ARG_STACKTRACE_OFF,
28 KASAN_ARG_STACKTRACE_ON,
31 static enum kasan_arg_stacktrace kasan_arg_stacktrace __initdata;
33 /* Whether to collect alloc/free stack traces. */
34 DEFINE_STATIC_KEY_TRUE(kasan_flag_stacktrace);
36 /* Non-zero, as initial pointer values are 0. */
37 #define STACK_RING_BUSY_PTR ((void *)1)
39 struct kasan_stack_ring stack_ring = {
40 .lock = __RW_LOCK_UNLOCKED(stack_ring.lock)
43 /* kasan.stacktrace=off/on */
44 static int __init early_kasan_flag_stacktrace(char *arg)
49 if (!strcmp(arg, "off"))
50 kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_OFF;
51 else if (!strcmp(arg, "on"))
52 kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_ON;
58 early_param("kasan.stacktrace", early_kasan_flag_stacktrace);
60 /* kasan.stack_ring_size=<number of entries> */
61 static int __init early_kasan_flag_stack_ring_size(char *arg)
66 return kstrtoul(arg, 0, &stack_ring.size);
68 early_param("kasan.stack_ring_size", early_kasan_flag_stack_ring_size);
70 void __init kasan_init_tags(void)
72 switch (kasan_arg_stacktrace) {
73 case KASAN_ARG_STACKTRACE_DEFAULT:
74 /* Default is specified by kasan_flag_stacktrace definition. */
76 case KASAN_ARG_STACKTRACE_OFF:
77 static_branch_disable(&kasan_flag_stacktrace);
79 case KASAN_ARG_STACKTRACE_ON:
80 static_branch_enable(&kasan_flag_stacktrace);
84 if (kasan_stack_collection_enabled()) {
86 stack_ring.size = KASAN_STACK_RING_SIZE_DEFAULT;
87 stack_ring.entries = memblock_alloc(
88 sizeof(stack_ring.entries[0]) * stack_ring.size,
90 if (WARN_ON(!stack_ring.entries))
91 static_branch_disable(&kasan_flag_stacktrace);
95 static void save_stack_info(struct kmem_cache *cache, void *object,
96 gfp_t gfp_flags, bool is_free)
99 depot_stack_handle_t stack;
101 struct kasan_stack_ring_entry *entry;
104 stack = kasan_save_stack(gfp_flags, true);
107 * Prevent save_stack_info() from modifying stack ring
108 * when kasan_complete_mode_report_info() is walking it.
110 read_lock_irqsave(&stack_ring.lock, flags);
113 pos = atomic64_fetch_add(1, &stack_ring.pos);
114 entry = &stack_ring.entries[pos % stack_ring.size];
116 /* Detect stack ring entry slots that are being written to. */
117 old_ptr = READ_ONCE(entry->ptr);
118 if (old_ptr == STACK_RING_BUSY_PTR)
119 goto next; /* Busy slot. */
120 if (!try_cmpxchg(&entry->ptr, &old_ptr, STACK_RING_BUSY_PTR))
121 goto next; /* Busy slot. */
123 WRITE_ONCE(entry->size, cache->object_size);
124 WRITE_ONCE(entry->pid, current->pid);
125 WRITE_ONCE(entry->stack, stack);
126 WRITE_ONCE(entry->is_free, is_free);
129 * Paired with smp_load_acquire() in kasan_complete_mode_report_info().
131 smp_store_release(&entry->ptr, (s64)object);
133 read_unlock_irqrestore(&stack_ring.lock, flags);
136 void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
138 save_stack_info(cache, object, flags, false);
141 void kasan_save_free_info(struct kmem_cache *cache, void *object)
143 save_stack_info(cache, object, GFP_NOWAIT, true);