1 // SPDX-License-Identifier: GPL-2.0
3 * This file contains core hardware tag-based KASAN code.
5 * Copyright (c) 2020 Google, Inc.
6 * Author: Andrey Konovalov <andreyknvl@google.com>
9 #define pr_fmt(fmt) "kasan: " fmt
11 #include <linux/init.h>
12 #include <linux/kasan.h>
13 #include <linux/kernel.h>
14 #include <linux/memory.h>
16 #include <linux/static_key.h>
17 #include <linux/string.h>
18 #include <linux/types.h>
29 KASAN_ARG_MODE_DEFAULT,
35 enum kasan_arg_stacktrace {
36 KASAN_ARG_STACKTRACE_DEFAULT,
37 KASAN_ARG_STACKTRACE_OFF,
38 KASAN_ARG_STACKTRACE_ON,
41 static enum kasan_arg kasan_arg __ro_after_init;
42 static enum kasan_arg_mode kasan_arg_mode __ro_after_init;
43 static enum kasan_arg_stacktrace kasan_arg_stacktrace __ro_after_init;
45 /* Whether KASAN is enabled at all. */
46 DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
47 EXPORT_SYMBOL(kasan_flag_enabled);
49 /* Whether the selected mode is synchronous/asynchronous/asymmetric.*/
50 enum kasan_mode kasan_mode __ro_after_init;
51 EXPORT_SYMBOL_GPL(kasan_mode);
53 /* Whether to collect alloc/free stack traces. */
54 DEFINE_STATIC_KEY_FALSE(kasan_flag_stacktrace);
57 static int __init early_kasan_flag(char *arg)
62 if (!strcmp(arg, "off"))
63 kasan_arg = KASAN_ARG_OFF;
64 else if (!strcmp(arg, "on"))
65 kasan_arg = KASAN_ARG_ON;
71 early_param("kasan", early_kasan_flag);
73 /* kasan.mode=sync/async/asymm */
74 static int __init early_kasan_mode(char *arg)
79 if (!strcmp(arg, "sync"))
80 kasan_arg_mode = KASAN_ARG_MODE_SYNC;
81 else if (!strcmp(arg, "async"))
82 kasan_arg_mode = KASAN_ARG_MODE_ASYNC;
83 else if (!strcmp(arg, "asymm"))
84 kasan_arg_mode = KASAN_ARG_MODE_ASYMM;
90 early_param("kasan.mode", early_kasan_mode);
92 /* kasan.stacktrace=off/on */
93 static int __init early_kasan_flag_stacktrace(char *arg)
98 if (!strcmp(arg, "off"))
99 kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_OFF;
100 else if (!strcmp(arg, "on"))
101 kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_ON;
107 early_param("kasan.stacktrace", early_kasan_flag_stacktrace);
109 /* kasan_init_hw_tags_cpu() is called for each CPU. */
110 void kasan_init_hw_tags_cpu(void)
113 * There's no need to check that the hardware is MTE-capable here,
114 * as this function is only called for MTE-capable hardware.
117 /* If KASAN is disabled via command line, don't initialize it. */
118 if (kasan_arg == KASAN_ARG_OFF)
122 * Enable async or asymm modes only when explicitly requested
123 * through the command line.
125 if (kasan_arg_mode == KASAN_ARG_MODE_ASYNC)
126 hw_enable_tagging_async();
127 else if (kasan_arg_mode == KASAN_ARG_MODE_ASYMM)
128 hw_enable_tagging_asymm();
130 hw_enable_tagging_sync();
133 /* kasan_init_hw_tags() is called once on boot CPU. */
134 void __init kasan_init_hw_tags(void)
136 /* If hardware doesn't support MTE, don't initialize KASAN. */
137 if (!system_supports_mte())
140 /* If KASAN is disabled via command line, don't initialize it. */
141 if (kasan_arg == KASAN_ARG_OFF)
145 static_branch_enable(&kasan_flag_enabled);
147 switch (kasan_arg_mode) {
148 case KASAN_ARG_MODE_DEFAULT:
150 * Default to sync mode.
153 case KASAN_ARG_MODE_SYNC:
154 /* Sync mode enabled. */
155 kasan_mode = KASAN_MODE_SYNC;
157 case KASAN_ARG_MODE_ASYNC:
158 /* Async mode enabled. */
159 kasan_mode = KASAN_MODE_ASYNC;
161 case KASAN_ARG_MODE_ASYMM:
162 /* Asymm mode enabled. */
163 kasan_mode = KASAN_MODE_ASYMM;
167 switch (kasan_arg_stacktrace) {
168 case KASAN_ARG_STACKTRACE_DEFAULT:
169 /* Default to enabling stack trace collection. */
170 static_branch_enable(&kasan_flag_stacktrace);
172 case KASAN_ARG_STACKTRACE_OFF:
173 /* Do nothing, kasan_flag_stacktrace keeps its default value. */
175 case KASAN_ARG_STACKTRACE_ON:
176 static_branch_enable(&kasan_flag_stacktrace);
180 pr_info("KernelAddressSanitizer initialized\n");
183 void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags)
186 * This condition should match the one in post_alloc_hook() in
189 bool init = !want_init_on_free() && want_init_on_alloc(flags);
191 if (flags & __GFP_SKIP_KASAN_POISON)
192 SetPageSkipKASanPoison(page);
194 if (flags & __GFP_ZEROTAGS) {
197 for (i = 0; i != 1 << order; ++i)
198 tag_clear_highpage(page + i);
200 kasan_unpoison_pages(page, order, init);
204 void kasan_free_pages(struct page *page, unsigned int order)
207 * This condition should match the one in free_pages_prepare() in
210 bool init = want_init_on_free();
212 kasan_poison_pages(page, order, init);
215 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
217 void kasan_enable_tagging_sync(void)
219 hw_enable_tagging_sync();
221 EXPORT_SYMBOL_GPL(kasan_enable_tagging_sync);
223 void kasan_force_async_fault(void)
225 hw_force_async_tag_fault();
227 EXPORT_SYMBOL_GPL(kasan_force_async_fault);