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