1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * A generic version of devmem_is_allowed.
4 *
5 * Based on arch/arm64/mm/mmap.c
6 *
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 address
17 * is valid. The argument is a physical page number. We mimic x86 here by
18 * disallowing access to system RAM as well as device-exclusive MMIO regions.
19 * This effectively disable read()/write() on /dev/mem.
20 */
21 int 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
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