242 lines
5.4 KiB
C
242 lines
5.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* This file contains core hardware tag-based KASAN code.
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*
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* Copyright (c) 2020 Google, Inc.
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* Author: Andrey Konovalov <andreyknvl@google.com>
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*/
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#define pr_fmt(fmt) "kasan: " fmt
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#include <linux/init.h>
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#include <linux/kasan.h>
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#include <linux/kernel.h>
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#include <linux/memory.h>
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#include <linux/mm.h>
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#include <linux/static_key.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include "kasan.h"
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enum kasan_arg {
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KASAN_ARG_DEFAULT,
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KASAN_ARG_OFF,
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KASAN_ARG_ON,
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};
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enum kasan_arg_mode {
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KASAN_ARG_MODE_DEFAULT,
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KASAN_ARG_MODE_SYNC,
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KASAN_ARG_MODE_ASYNC,
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KASAN_ARG_MODE_ASYMM,
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};
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enum kasan_arg_stacktrace {
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KASAN_ARG_STACKTRACE_DEFAULT,
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KASAN_ARG_STACKTRACE_OFF,
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KASAN_ARG_STACKTRACE_ON,
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};
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static enum kasan_arg kasan_arg __ro_after_init;
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static enum kasan_arg_mode kasan_arg_mode __ro_after_init;
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static enum kasan_arg_stacktrace kasan_arg_stacktrace __ro_after_init;
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/* Whether KASAN is enabled at all. */
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DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
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EXPORT_SYMBOL(kasan_flag_enabled);
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/* Whether the selected mode is synchronous/asynchronous/asymmetric.*/
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enum kasan_mode kasan_mode __ro_after_init;
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EXPORT_SYMBOL_GPL(kasan_mode);
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/* Whether to collect alloc/free stack traces. */
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DEFINE_STATIC_KEY_FALSE(kasan_flag_stacktrace);
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/* kasan=off/on */
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static int __init early_kasan_flag(char *arg)
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{
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if (!arg)
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return -EINVAL;
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if (!strcmp(arg, "off"))
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kasan_arg = KASAN_ARG_OFF;
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else if (!strcmp(arg, "on"))
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kasan_arg = KASAN_ARG_ON;
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else
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return -EINVAL;
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return 0;
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}
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early_param("kasan", early_kasan_flag);
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/* kasan.mode=sync/async/asymm */
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static int __init early_kasan_mode(char *arg)
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{
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if (!arg)
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return -EINVAL;
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if (!strcmp(arg, "sync"))
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kasan_arg_mode = KASAN_ARG_MODE_SYNC;
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else if (!strcmp(arg, "async"))
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kasan_arg_mode = KASAN_ARG_MODE_ASYNC;
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else if (!strcmp(arg, "asymm"))
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kasan_arg_mode = KASAN_ARG_MODE_ASYMM;
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else
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return -EINVAL;
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return 0;
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}
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early_param("kasan.mode", early_kasan_mode);
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/* kasan.stacktrace=off/on */
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static int __init early_kasan_flag_stacktrace(char *arg)
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{
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if (!arg)
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return -EINVAL;
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if (!strcmp(arg, "off"))
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kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_OFF;
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else if (!strcmp(arg, "on"))
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kasan_arg_stacktrace = KASAN_ARG_STACKTRACE_ON;
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else
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return -EINVAL;
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return 0;
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}
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early_param("kasan.stacktrace", early_kasan_flag_stacktrace);
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static inline const char *kasan_mode_info(void)
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{
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if (kasan_mode == KASAN_MODE_ASYNC)
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return "async";
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else if (kasan_mode == KASAN_MODE_ASYMM)
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return "asymm";
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else
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return "sync";
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}
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/* kasan_init_hw_tags_cpu() is called for each CPU. */
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void kasan_init_hw_tags_cpu(void)
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{
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/*
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* There's no need to check that the hardware is MTE-capable here,
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* as this function is only called for MTE-capable hardware.
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*/
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/* If KASAN is disabled via command line, don't initialize it. */
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if (kasan_arg == KASAN_ARG_OFF)
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return;
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/*
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* Enable async or asymm modes only when explicitly requested
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* through the command line.
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*/
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if (kasan_arg_mode == KASAN_ARG_MODE_ASYNC)
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hw_enable_tagging_async();
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else if (kasan_arg_mode == KASAN_ARG_MODE_ASYMM)
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hw_enable_tagging_asymm();
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else
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hw_enable_tagging_sync();
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}
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/* kasan_init_hw_tags() is called once on boot CPU. */
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void __init kasan_init_hw_tags(void)
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{
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/* If hardware doesn't support MTE, don't initialize KASAN. */
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if (!system_supports_mte())
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return;
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/* If KASAN is disabled via command line, don't initialize it. */
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if (kasan_arg == KASAN_ARG_OFF)
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return;
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/* Enable KASAN. */
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static_branch_enable(&kasan_flag_enabled);
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switch (kasan_arg_mode) {
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case KASAN_ARG_MODE_DEFAULT:
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/*
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* Default to sync mode.
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*/
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fallthrough;
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case KASAN_ARG_MODE_SYNC:
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/* Sync mode enabled. */
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kasan_mode = KASAN_MODE_SYNC;
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break;
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case KASAN_ARG_MODE_ASYNC:
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/* Async mode enabled. */
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kasan_mode = KASAN_MODE_ASYNC;
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break;
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case KASAN_ARG_MODE_ASYMM:
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/* Asymm mode enabled. */
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kasan_mode = KASAN_MODE_ASYMM;
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break;
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}
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switch (kasan_arg_stacktrace) {
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case KASAN_ARG_STACKTRACE_DEFAULT:
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/* Default to enabling stack trace collection. */
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static_branch_enable(&kasan_flag_stacktrace);
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break;
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case KASAN_ARG_STACKTRACE_OFF:
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/* Do nothing, kasan_flag_stacktrace keeps its default value. */
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break;
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case KASAN_ARG_STACKTRACE_ON:
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static_branch_enable(&kasan_flag_stacktrace);
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break;
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}
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pr_info("KernelAddressSanitizer initialized (hw-tags, mode=%s, stacktrace=%s)\n",
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kasan_mode_info(),
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kasan_stack_collection_enabled() ? "on" : "off");
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}
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void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags)
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{
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/*
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* This condition should match the one in post_alloc_hook() in
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* page_alloc.c.
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*/
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bool init = !want_init_on_free() && want_init_on_alloc(flags);
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if (flags & __GFP_SKIP_KASAN_POISON)
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SetPageSkipKASanPoison(page);
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if (flags & __GFP_ZEROTAGS) {
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int i;
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for (i = 0; i != 1 << order; ++i)
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tag_clear_highpage(page + i);
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} else {
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kasan_unpoison_pages(page, order, init);
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}
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}
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void kasan_free_pages(struct page *page, unsigned int order)
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{
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/*
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* This condition should match the one in free_pages_prepare() in
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* page_alloc.c.
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*/
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bool init = want_init_on_free();
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kasan_poison_pages(page, order, init);
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}
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#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
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void kasan_enable_tagging_sync(void)
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{
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hw_enable_tagging_sync();
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}
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EXPORT_SYMBOL_GPL(kasan_enable_tagging_sync);
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void kasan_force_async_fault(void)
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{
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hw_force_async_tag_fault();
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}
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EXPORT_SYMBOL_GPL(kasan_force_async_fault);
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#endif
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