82 lines
2.7 KiB
C
82 lines
2.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* arch/arm/include/asm/kasan_def.h
|
|
*
|
|
* Copyright (c) 2018 Huawei Technologies Co., Ltd.
|
|
*
|
|
* Author: Abbott Liu <liuwenliang@huawei.com>
|
|
*/
|
|
|
|
#ifndef __ASM_KASAN_DEF_H
|
|
#define __ASM_KASAN_DEF_H
|
|
|
|
#ifdef CONFIG_KASAN
|
|
|
|
/*
|
|
* Define KASAN_SHADOW_OFFSET,KASAN_SHADOW_START and KASAN_SHADOW_END for
|
|
* the Arm kernel address sanitizer. We are "stealing" lowmem (the 4GB
|
|
* addressable by a 32bit architecture) out of the virtual address
|
|
* space to use as shadow memory for KASan as follows:
|
|
*
|
|
* +----+ 0xffffffff
|
|
* | | \
|
|
* | | |-> Static kernel image (vmlinux) BSS and page table
|
|
* | |/
|
|
* +----+ PAGE_OFFSET
|
|
* | | \
|
|
* | | |-> Loadable kernel modules virtual address space area
|
|
* | |/
|
|
* +----+ MODULES_VADDR = KASAN_SHADOW_END
|
|
* | | \
|
|
* | | |-> The shadow area of kernel virtual address.
|
|
* | |/
|
|
* +----+-> TASK_SIZE (start of kernel space) = KASAN_SHADOW_START the
|
|
* | |\ shadow address of MODULES_VADDR
|
|
* | | |
|
|
* | | |
|
|
* | | |-> The user space area in lowmem. The kernel address
|
|
* | | | sanitizer do not use this space, nor does it map it.
|
|
* | | |
|
|
* | | |
|
|
* | | |
|
|
* | | |
|
|
* | |/
|
|
* ------ 0
|
|
*
|
|
* 1) KASAN_SHADOW_START
|
|
* This value begins with the MODULE_VADDR's shadow address. It is the
|
|
* start of kernel virtual space. Since we have modules to load, we need
|
|
* to cover also that area with shadow memory so we can find memory
|
|
* bugs in modules.
|
|
*
|
|
* 2) KASAN_SHADOW_END
|
|
* This value is the 0x100000000's shadow address: the mapping that would
|
|
* be after the end of the kernel memory at 0xffffffff. It is the end of
|
|
* kernel address sanitizer shadow area. It is also the start of the
|
|
* module area.
|
|
*
|
|
* 3) KASAN_SHADOW_OFFSET:
|
|
* This value is used to map an address to the corresponding shadow
|
|
* address by the following formula:
|
|
*
|
|
* shadow_addr = (address >> 3) + KASAN_SHADOW_OFFSET;
|
|
*
|
|
* As you would expect, >> 3 is equal to dividing by 8, meaning each
|
|
* byte in the shadow memory covers 8 bytes of kernel memory, so one
|
|
* bit shadow memory per byte of kernel memory is used.
|
|
*
|
|
* The KASAN_SHADOW_OFFSET is provided in a Kconfig option depending
|
|
* on the VMSPLIT layout of the system: the kernel and userspace can
|
|
* split up lowmem in different ways according to needs, so we calculate
|
|
* the shadow offset depending on this.
|
|
*/
|
|
|
|
#define KASAN_SHADOW_SCALE_SHIFT 3
|
|
#define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
|
|
#define KASAN_SHADOW_END ((UL(1) << (32 - KASAN_SHADOW_SCALE_SHIFT)) \
|
|
+ KASAN_SHADOW_OFFSET)
|
|
#define KASAN_SHADOW_START ((KASAN_SHADOW_END >> 3) + KASAN_SHADOW_OFFSET)
|
|
|
|
#endif
|
|
#endif
|