// SPDX-License-Identifier: GPL-2.0-only /* * A generic version of devmem_is_allowed. * * Based on arch/arm64/mm/mmap.c * * Copyright (C) 2020 Google, Inc. * Copyright (C) 2012 ARM Ltd. */ #include <linux/mm.h> #include <linux/ioport.h> /* * devmem_is_allowed() checks to see if /dev/mem access to a certain address * is valid. The argument is a physical page number. We mimic x86 here by * disallowing access to system RAM as well as device-exclusive MMIO regions. * This effectively disable read()/write() on /dev/mem. */ int devmem_is_allowed(unsigned long pfn) { if (iomem_is_exclusive(PFN_PHYS(pfn))) return 0; if (!page_is_ram(pfn)) return 1; return 0; }