| 1 | |
| 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 | }
|