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,
34 enum kasan_arg_stacktrace {
35 KASAN_ARG_STACKTRACE_DEFAULT,
36 KASAN_ARG_STACKTRACE_OFF,
37 KASAN_ARG_STACKTRACE_ON,
40 static enum kasan_arg kasan_arg __ro_after_init;
41 static enum kasan_arg_mode kasan_arg_mode __ro_after_init;
42 static enum kasan_arg_stacktrace kasan_arg_stacktrace __ro_after_init;
44 /* Whether KASAN is enabled at all. */
45 DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
46 EXPORT_SYMBOL(kasan_flag_enabled);
48 /* Whether the asynchronous mode is enabled. */
49 bool kasan_flag_async __ro_after_init;
50 EXPORT_SYMBOL_GPL(kasan_flag_async);
52 /* Whether to collect alloc/free stack traces. */
53 DEFINE_STATIC_KEY_FALSE(kasan_flag_stacktrace);
56 static int __init early_kasan_flag(char *arg)
61 if (!strcmp(arg, "off"))
62 kasan_arg = KASAN_ARG_OFF;
63 else if (!strcmp(arg, "on"))
64 kasan_arg = KASAN_ARG_ON;
70 early_param("kasan", early_kasan_flag);
72 /* kasan.mode=sync/async */
73 static int __init early_kasan_mode(char *arg)
78 if (!strcmp(arg, "sync"))
79 kasan_arg_mode = KASAN_ARG_MODE_SYNC;
80 else if (!strcmp(arg, "async"))
81 kasan_arg_mode = KASAN_ARG_MODE_ASYNC;
87 early_param("kasan.mode", early_kasan_mode);
89 /* kasan.stacktrace=off/on */
90 static int __init early_kasan_flag_stacktrace(char *arg)
95 if (!strcmp(arg, "off"))
96 kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_OFF;
97 else if (!strcmp(arg, "on"))
98 kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_ON;
104 early_param("kasan.stacktrace", early_kasan_flag_stacktrace);
106 /* kasan_init_hw_tags_cpu() is called for each CPU. */
107 void kasan_init_hw_tags_cpu(void)
110 * There's no need to check that the hardware is MTE-capable here,
111 * as this function is only called for MTE-capable hardware.
114 /* If KASAN is disabled via command line, don't initialize it. */
115 if (kasan_arg == KASAN_ARG_OFF)
119 * Enable async mode only when explicitly requested through
122 if (kasan_arg_mode == KASAN_ARG_MODE_ASYNC)
123 hw_enable_tagging_async();
125 hw_enable_tagging_sync();
128 /* kasan_init_hw_tags() is called once on boot CPU. */
129 void __init kasan_init_hw_tags(void)
131 /* If hardware doesn't support MTE, don't initialize KASAN. */
132 if (!system_supports_mte())
135 /* If KASAN is disabled via command line, don't initialize it. */
136 if (kasan_arg == KASAN_ARG_OFF)
140 static_branch_enable(&kasan_flag_enabled);
142 switch (kasan_arg_mode) {
143 case KASAN_ARG_MODE_DEFAULT:
145 * Default to sync mode.
146 * Do nothing, kasan_flag_async keeps its default value.
149 case KASAN_ARG_MODE_SYNC:
150 /* Do nothing, kasan_flag_async keeps its default value. */
152 case KASAN_ARG_MODE_ASYNC:
153 /* Async mode enabled. */
154 kasan_flag_async = true;
158 switch (kasan_arg_stacktrace) {
159 case KASAN_ARG_STACKTRACE_DEFAULT:
160 /* Default to enabling stack trace collection. */
161 static_branch_enable(&kasan_flag_stacktrace);
163 case KASAN_ARG_STACKTRACE_OFF:
164 /* Do nothing, kasan_flag_stacktrace keeps its default value. */
166 case KASAN_ARG_STACKTRACE_ON:
167 static_branch_enable(&kasan_flag_stacktrace);
171 pr_info("KernelAddressSanitizer initialized\n");
174 void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags)
177 * This condition should match the one in post_alloc_hook() in
180 bool init = !want_init_on_free() && want_init_on_alloc(flags);
182 if (flags & __GFP_SKIP_KASAN_POISON)
183 SetPageSkipKASanPoison(page);
185 if (flags & __GFP_ZEROTAGS) {
188 for (i = 0; i != 1 << order; ++i)
189 tag_clear_highpage(page + i);
191 kasan_unpoison_pages(page, order, init);
195 void kasan_free_pages(struct page *page, unsigned int order)
198 * This condition should match the one in free_pages_prepare() in
201 bool init = want_init_on_free();
203 kasan_poison_pages(page, order, init);
206 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
208 void kasan_enable_tagging_sync(void)
210 hw_enable_tagging_sync();
212 EXPORT_SYMBOL_GPL(kasan_enable_tagging_sync);
214 void kasan_force_async_fault(void)
216 hw_force_async_tag_fault();
218 EXPORT_SYMBOL_GPL(kasan_force_async_fault);