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1d18c47c CM |
1 | /* |
2 | * Based on arch/arm/mm/mmap.c | |
3 | * | |
4 | * Copyright (C) 2012 ARM Ltd. | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License version 2 as | |
8 | * published by the Free Software Foundation. | |
9 | * | |
10 | * This program is distributed in the hope that it will be useful, | |
11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | * GNU General Public License for more details. | |
14 | * | |
15 | * You should have received a copy of the GNU General Public License | |
16 | * along with this program. If not, see <http://www.gnu.org/licenses/>. | |
17 | */ | |
18 | ||
19 | #include <linux/elf.h> | |
20 | #include <linux/fs.h> | |
21 | #include <linux/mm.h> | |
22 | #include <linux/mman.h> | |
23 | #include <linux/export.h> | |
24 | #include <linux/shm.h> | |
25 | #include <linux/sched.h> | |
26 | #include <linux/io.h> | |
27 | #include <linux/personality.h> | |
28 | #include <linux/random.h> | |
29 | ||
30 | #include <asm/cputype.h> | |
31 | ||
32 | /* | |
33 | * Leave enough space between the mmap area and the stack to honour ulimit in | |
34 | * the face of randomisation. | |
35 | */ | |
36 | #define MIN_GAP (SZ_128M + ((STACK_RND_MASK << PAGE_SHIFT) + 1)) | |
37 | #define MAX_GAP (STACK_TOP/6*5) | |
38 | ||
39 | static int mmap_is_legacy(void) | |
40 | { | |
41 | if (current->personality & ADDR_COMPAT_LAYOUT) | |
42 | return 1; | |
43 | ||
44 | if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) | |
45 | return 1; | |
46 | ||
47 | return sysctl_legacy_va_layout; | |
48 | } | |
49 | ||
2b68f6ca | 50 | unsigned long arch_mmap_rnd(void) |
1d18c47c | 51 | { |
dd04cff1 | 52 | unsigned long rnd; |
1d18c47c | 53 | |
8f0d3aa9 DC |
54 | #ifdef CONFIG_COMPAT |
55 | if (test_thread_flag(TIF_32BIT)) | |
56 | rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_compat_bits) - 1); | |
57 | else | |
58 | #endif | |
59 | rnd = (unsigned long)get_random_int() & ((1 << mmap_rnd_bits) - 1); | |
d6c763af | 60 | return rnd << PAGE_SHIFT; |
1d18c47c CM |
61 | } |
62 | ||
dd04cff1 | 63 | static unsigned long mmap_base(unsigned long rnd) |
1d18c47c CM |
64 | { |
65 | unsigned long gap = rlimit(RLIMIT_STACK); | |
66 | ||
67 | if (gap < MIN_GAP) | |
68 | gap = MIN_GAP; | |
69 | else if (gap > MAX_GAP) | |
70 | gap = MAX_GAP; | |
71 | ||
dd04cff1 | 72 | return PAGE_ALIGN(STACK_TOP - gap - rnd); |
1d18c47c CM |
73 | } |
74 | ||
75 | /* | |
76 | * This function, called very early during the creation of a new process VM | |
77 | * image, sets up which VM layout function to use: | |
78 | */ | |
79 | void arch_pick_mmap_layout(struct mm_struct *mm) | |
80 | { | |
dd04cff1 KC |
81 | unsigned long random_factor = 0UL; |
82 | ||
83 | if (current->flags & PF_RANDOMIZE) | |
2b68f6ca | 84 | random_factor = arch_mmap_rnd(); |
dd04cff1 | 85 | |
1d18c47c CM |
86 | /* |
87 | * Fall back to the standard layout if the personality bit is set, or | |
88 | * if the expected stack growth is unlimited: | |
89 | */ | |
90 | if (mmap_is_legacy()) { | |
dd04cff1 | 91 | mm->mmap_base = TASK_UNMAPPED_BASE + random_factor; |
1d18c47c | 92 | mm->get_unmapped_area = arch_get_unmapped_area; |
1d18c47c | 93 | } else { |
dd04cff1 | 94 | mm->mmap_base = mmap_base(random_factor); |
1d18c47c | 95 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; |
1d18c47c CM |
96 | } |
97 | } | |
98 | EXPORT_SYMBOL_GPL(arch_pick_mmap_layout); | |
99 | ||
100 | ||
101 | /* | |
102 | * You really shouldn't be using read() or write() on /dev/mem. This might go | |
103 | * away in the future. | |
104 | */ | |
097cbd8d | 105 | int valid_phys_addr_range(phys_addr_t addr, size_t size) |
1d18c47c CM |
106 | { |
107 | if (addr < PHYS_OFFSET) | |
108 | return 0; | |
109 | if (addr + size > __pa(high_memory - 1) + 1) | |
110 | return 0; | |
111 | ||
112 | return 1; | |
113 | } | |
114 | ||
115 | /* | |
116 | * Do not allow /dev/mem mappings beyond the supported physical range. | |
117 | */ | |
118 | int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) | |
119 | { | |
120 | return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK); | |
121 | } | |
122 | ||
123 | #ifdef CONFIG_STRICT_DEVMEM | |
124 | ||
125 | #include <linux/ioport.h> | |
126 | ||
127 | /* | |
128 | * devmem_is_allowed() checks to see if /dev/mem access to a certain address | |
129 | * is valid. The argument is a physical page number. We mimic x86 here by | |
130 | * disallowing access to system RAM as well as device-exclusive MMIO regions. | |
131 | * This effectively disable read()/write() on /dev/mem. | |
132 | */ | |
133 | int devmem_is_allowed(unsigned long pfn) | |
134 | { | |
135 | if (iomem_is_exclusive(pfn << PAGE_SHIFT)) | |
136 | return 0; | |
137 | if (!page_is_ram(pfn)) | |
138 | return 1; | |
139 | return 0; | |
140 | } | |
141 | ||
142 | #endif |