1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Based on arch/arm/mm/mmap.c
4 *
5 * Copyright (C) 2012 ARM Ltd.
6 */
7
8 #include <linux/elf.h>
9 #include <linux/fs.h>
10 #include <linux/memblock.h>
11 #include <linux/mm.h>
12 #include <linux/mman.h>
13 #include <linux/export.h>
14 #include <linux/shm.h>
15 #include <linux/sched/signal.h>
16 #include <linux/sched/mm.h>
17 #include <linux/io.h>
18 #include <linux/personality.h>
19 #include <linux/random.h>
20
21 #include <asm/cputype.h>
22
23 /*
24 * You really shouldn't be using read() or write() on /dev/mem. This might go
25 * away in the future.
26 */
27 int valid_phys_addr_range(phys_addr_t addr, size_t size)
28 {
29 /*
30 * Check whether addr is covered by a memory region without the
31 * MEMBLOCK_NOMAP attribute, and whether that region covers the
32 * entire range. In theory, this could lead to false negatives
33 * if the range is covered by distinct but adjacent memory regions
34 * that only differ in other attributes. However, few of such
35 * attributes have been defined, and it is debatable whether it
36 * follows that /dev/mem read() calls should be able traverse
37 * such boundaries.
38 */
39 return memblock_is_region_memory(addr, size) &&
40 memblock_is_map_memory(addr);
41 }
42
43 /*
44 * Do not allow /dev/mem mappings beyond the supported physical range.
45 */
46 int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
47 {
48 return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK);
49 }
50
51 #ifdef CONFIG_STRICT_DEVMEM
52
53 #include <linux/ioport.h>
54
55 /*
56 * devmem_is_allowed() checks to see if /dev/mem access to a certain address
57 * is valid. The argument is a physical page number. We mimic x86 here by
58 * disallowing access to system RAM as well as device-exclusive MMIO regions.
59 * This effectively disable read()/write() on /dev/mem.
60 */
61 int devmem_is_allowed(unsigned long pfn)
62 {
63 if (iomem_is_exclusive(pfn << PAGE_SHIFT))
64 return 0;
65 if (!page_is_ram(pfn))
66 return 1;
67 return 0;
68 }
69
70 #endif