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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 | ||
50 | /* | |
51 | * Since get_random_int() returns the same value within a 1 jiffy window, we | |
52 | * will almost always get the same randomisation for the stack and mmap | |
53 | * region. This will mean the relative distance between stack and mmap will be | |
54 | * the same. | |
55 | * | |
56 | * To avoid this we can shift the randomness by 1 bit. | |
57 | */ | |
58 | static unsigned long mmap_rnd(void) | |
59 | { | |
60 | unsigned long rnd = 0; | |
61 | ||
62 | if (current->flags & PF_RANDOMIZE) | |
63 | rnd = (long)get_random_int() & (STACK_RND_MASK >> 1); | |
64 | ||
65 | return rnd << (PAGE_SHIFT + 1); | |
66 | } | |
67 | ||
68 | static unsigned long mmap_base(void) | |
69 | { | |
70 | unsigned long gap = rlimit(RLIMIT_STACK); | |
71 | ||
72 | if (gap < MIN_GAP) | |
73 | gap = MIN_GAP; | |
74 | else if (gap > MAX_GAP) | |
75 | gap = MAX_GAP; | |
76 | ||
77 | return PAGE_ALIGN(STACK_TOP - gap - mmap_rnd()); | |
78 | } | |
79 | ||
80 | /* | |
81 | * This function, called very early during the creation of a new process VM | |
82 | * image, sets up which VM layout function to use: | |
83 | */ | |
84 | void arch_pick_mmap_layout(struct mm_struct *mm) | |
85 | { | |
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()) { | |
91 | mm->mmap_base = TASK_UNMAPPED_BASE; | |
92 | mm->get_unmapped_area = arch_get_unmapped_area; | |
93 | mm->unmap_area = arch_unmap_area; | |
94 | } else { | |
95 | mm->mmap_base = mmap_base(); | |
96 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; | |
97 | mm->unmap_area = arch_unmap_area_topdown; | |
98 | } | |
99 | } | |
100 | EXPORT_SYMBOL_GPL(arch_pick_mmap_layout); | |
101 | ||
102 | ||
103 | /* | |
104 | * You really shouldn't be using read() or write() on /dev/mem. This might go | |
105 | * away in the future. | |
106 | */ | |
107 | int valid_phys_addr_range(unsigned long addr, size_t size) | |
108 | { | |
109 | if (addr < PHYS_OFFSET) | |
110 | return 0; | |
111 | if (addr + size > __pa(high_memory - 1) + 1) | |
112 | return 0; | |
113 | ||
114 | return 1; | |
115 | } | |
116 | ||
117 | /* | |
118 | * Do not allow /dev/mem mappings beyond the supported physical range. | |
119 | */ | |
120 | int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) | |
121 | { | |
122 | return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK); | |
123 | } | |
124 | ||
125 | #ifdef CONFIG_STRICT_DEVMEM | |
126 | ||
127 | #include <linux/ioport.h> | |
128 | ||
129 | /* | |
130 | * devmem_is_allowed() checks to see if /dev/mem access to a certain address | |
131 | * is valid. The argument is a physical page number. We mimic x86 here by | |
132 | * disallowing access to system RAM as well as device-exclusive MMIO regions. | |
133 | * This effectively disable read()/write() on /dev/mem. | |
134 | */ | |
135 | int devmem_is_allowed(unsigned long pfn) | |
136 | { | |
137 | if (iomem_is_exclusive(pfn << PAGE_SHIFT)) | |
138 | return 0; | |
139 | if (!page_is_ram(pfn)) | |
140 | return 1; | |
141 | return 0; | |
142 | } | |
143 | ||
144 | #endif |