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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> | |
1151f838 | 21 | #include <linux/memblock.h> |
1d18c47c CM |
22 | #include <linux/mm.h> |
23 | #include <linux/mman.h> | |
24 | #include <linux/export.h> | |
25 | #include <linux/shm.h> | |
3f07c014 | 26 | #include <linux/sched/signal.h> |
01042607 | 27 | #include <linux/sched/mm.h> |
1d18c47c CM |
28 | #include <linux/io.h> |
29 | #include <linux/personality.h> | |
30 | #include <linux/random.h> | |
31 | ||
32 | #include <asm/cputype.h> | |
33 | ||
34 | /* | |
35 | * Leave enough space between the mmap area and the stack to honour ulimit in | |
36 | * the face of randomisation. | |
37 | */ | |
cf92251d | 38 | #define MIN_GAP (SZ_128M) |
1d18c47c CM |
39 | #define MAX_GAP (STACK_TOP/6*5) |
40 | ||
41 | static int mmap_is_legacy(void) | |
42 | { | |
43 | if (current->personality & ADDR_COMPAT_LAYOUT) | |
44 | return 1; | |
45 | ||
46 | if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) | |
47 | return 1; | |
48 | ||
49 | return sysctl_legacy_va_layout; | |
50 | } | |
51 | ||
2b68f6ca | 52 | unsigned long arch_mmap_rnd(void) |
1d18c47c | 53 | { |
dd04cff1 | 54 | unsigned long rnd; |
1d18c47c | 55 | |
8f0d3aa9 DC |
56 | #ifdef CONFIG_COMPAT |
57 | if (test_thread_flag(TIF_32BIT)) | |
5ef11c35 | 58 | rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1); |
8f0d3aa9 DC |
59 | else |
60 | #endif | |
5ef11c35 | 61 | rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1); |
d6c763af | 62 | return rnd << PAGE_SHIFT; |
1d18c47c CM |
63 | } |
64 | ||
dd04cff1 | 65 | static unsigned long mmap_base(unsigned long rnd) |
1d18c47c CM |
66 | { |
67 | unsigned long gap = rlimit(RLIMIT_STACK); | |
cf92251d RR |
68 | unsigned long pad = (STACK_RND_MASK << PAGE_SHIFT) + stack_guard_gap; |
69 | ||
70 | /* Values close to RLIM_INFINITY can overflow. */ | |
71 | if (gap + pad > gap) | |
72 | gap += pad; | |
1d18c47c CM |
73 | |
74 | if (gap < MIN_GAP) | |
75 | gap = MIN_GAP; | |
76 | else if (gap > MAX_GAP) | |
77 | gap = MAX_GAP; | |
78 | ||
dd04cff1 | 79 | return PAGE_ALIGN(STACK_TOP - gap - rnd); |
1d18c47c CM |
80 | } |
81 | ||
82 | /* | |
83 | * This function, called very early during the creation of a new process VM | |
84 | * image, sets up which VM layout function to use: | |
85 | */ | |
86 | void arch_pick_mmap_layout(struct mm_struct *mm) | |
87 | { | |
dd04cff1 KC |
88 | unsigned long random_factor = 0UL; |
89 | ||
90 | if (current->flags & PF_RANDOMIZE) | |
2b68f6ca | 91 | random_factor = arch_mmap_rnd(); |
dd04cff1 | 92 | |
1d18c47c CM |
93 | /* |
94 | * Fall back to the standard layout if the personality bit is set, or | |
95 | * if the expected stack growth is unlimited: | |
96 | */ | |
97 | if (mmap_is_legacy()) { | |
dd04cff1 | 98 | mm->mmap_base = TASK_UNMAPPED_BASE + random_factor; |
1d18c47c | 99 | mm->get_unmapped_area = arch_get_unmapped_area; |
1d18c47c | 100 | } else { |
dd04cff1 | 101 | mm->mmap_base = mmap_base(random_factor); |
1d18c47c | 102 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; |
1d18c47c CM |
103 | } |
104 | } | |
1d18c47c CM |
105 | |
106 | /* | |
107 | * You really shouldn't be using read() or write() on /dev/mem. This might go | |
108 | * away in the future. | |
109 | */ | |
097cbd8d | 110 | int valid_phys_addr_range(phys_addr_t addr, size_t size) |
1d18c47c | 111 | { |
1151f838 AB |
112 | /* |
113 | * Check whether addr is covered by a memory region without the | |
114 | * MEMBLOCK_NOMAP attribute, and whether that region covers the | |
115 | * entire range. In theory, this could lead to false negatives | |
116 | * if the range is covered by distinct but adjacent memory regions | |
117 | * that only differ in other attributes. However, few of such | |
118 | * attributes have been defined, and it is debatable whether it | |
119 | * follows that /dev/mem read() calls should be able traverse | |
120 | * such boundaries. | |
121 | */ | |
122 | return memblock_is_region_memory(addr, size) && | |
123 | memblock_is_map_memory(addr); | |
1d18c47c CM |
124 | } |
125 | ||
126 | /* | |
127 | * Do not allow /dev/mem mappings beyond the supported physical range. | |
128 | */ | |
129 | int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) | |
130 | { | |
131 | return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK); | |
132 | } | |
133 | ||
134 | #ifdef CONFIG_STRICT_DEVMEM | |
135 | ||
136 | #include <linux/ioport.h> | |
137 | ||
138 | /* | |
139 | * devmem_is_allowed() checks to see if /dev/mem access to a certain address | |
140 | * is valid. The argument is a physical page number. We mimic x86 here by | |
141 | * disallowing access to system RAM as well as device-exclusive MMIO regions. | |
142 | * This effectively disable read()/write() on /dev/mem. | |
143 | */ | |
144 | int devmem_is_allowed(unsigned long pfn) | |
145 | { | |
146 | if (iomem_is_exclusive(pfn << PAGE_SHIFT)) | |
147 | return 0; | |
148 | if (!page_is_ram(pfn)) | |
149 | return 1; | |
150 | return 0; | |
151 | } | |
152 | ||
153 | #endif |