29 lines · c
1// SPDX-License-Identifier: GPL-2.0-only2/*3 * A generic version of devmem_is_allowed.4 *5 * Based on arch/arm64/mm/mmap.c6 *7 * Copyright (C) 2020 Google, Inc.8 * Copyright (C) 2012 ARM Ltd.9 */10 11#include <linux/mm.h>12#include <linux/ioport.h>13#include <linux/io.h>14 15/*16 * devmem_is_allowed() checks to see if /dev/mem access to a certain address17 * is valid. The argument is a physical page number. We mimic x86 here by18 * disallowing access to system RAM as well as device-exclusive MMIO regions.19 * This effectively disable read()/write() on /dev/mem.20 */21int devmem_is_allowed(unsigned long pfn)22{23 if (iomem_is_exclusive(PFN_PHYS(pfn)))24 return 0;25 if (!page_is_ram(pfn))26 return 1;27 return 0;28}29