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1da177e4 | 1 | /* |
1da177e4 LT |
2 | * flexible mmap layout support |
3 | * | |
4 | * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina. | |
5 | * All Rights Reserved. | |
6 | * | |
7 | * This program is free software; you can redistribute it and/or modify | |
8 | * it under the terms of the GNU General Public License as published by | |
9 | * the Free Software Foundation; either version 2 of the License, or | |
10 | * (at your option) any later version. | |
11 | * | |
12 | * This program is distributed in the hope that it will be useful, | |
13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | * GNU General Public License for more details. | |
16 | * | |
17 | * You should have received a copy of the GNU General Public License | |
18 | * along with this program; if not, write to the Free Software | |
19 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
20 | * | |
21 | * | |
22 | * Started by Ingo Molnar <mingo@elte.hu> | |
23 | */ | |
24 | ||
25 | #include <linux/personality.h> | |
26 | #include <linux/mm.h> | |
9f14c42d | 27 | #include <linux/random.h> |
3f07c014 | 28 | #include <linux/sched/signal.h> |
01042607 | 29 | #include <linux/sched/mm.h> |
7f92bc56 | 30 | #include <linux/elf-randomize.h> |
7a0eedee AK |
31 | #include <linux/security.h> |
32 | #include <linux/mman.h> | |
1da177e4 LT |
33 | |
34 | /* | |
35 | * Top of mmap area (just below the process stack). | |
36 | * | |
002b0ec7 AB |
37 | * Leave at least a ~128 MB hole on 32bit applications. |
38 | * | |
39 | * On 64bit applications we randomise the stack by 1GB so we need to | |
40 | * space our mmap start address by a further 1GB, otherwise there is a | |
41 | * chance the mmap area will end up closer to the stack than our ulimit | |
42 | * requires. | |
1da177e4 | 43 | */ |
002b0ec7 AB |
44 | #define MIN_GAP32 (128*1024*1024) |
45 | #define MIN_GAP64 ((128 + 1024)*1024*1024UL) | |
46 | #define MIN_GAP ((is_32bit_task()) ? MIN_GAP32 : MIN_GAP64) | |
1da177e4 LT |
47 | #define MAX_GAP (TASK_SIZE/6*5) |
48 | ||
13a2cb36 AB |
49 | static inline int mmap_is_legacy(void) |
50 | { | |
51 | if (current->personality & ADDR_COMPAT_LAYOUT) | |
52 | return 1; | |
53 | ||
4bf936b9 | 54 | if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) |
13a2cb36 AB |
55 | return 1; |
56 | ||
57 | return sysctl_legacy_va_layout; | |
58 | } | |
59 | ||
2b68f6ca | 60 | unsigned long arch_mmap_rnd(void) |
9f14c42d | 61 | { |
9fea59bd | 62 | unsigned long shift, rnd; |
ed632274 | 63 | |
9fea59bd ME |
64 | shift = mmap_rnd_bits; |
65 | #ifdef CONFIG_COMPAT | |
ed632274 | 66 | if (is_32bit_task()) |
9fea59bd ME |
67 | shift = mmap_rnd_compat_bits; |
68 | #endif | |
b409946b | 69 | rnd = get_random_long() % (1ul << shift); |
9f14c42d | 70 | |
fa8cbaaf | 71 | return rnd << PAGE_SHIFT; |
9f14c42d AB |
72 | } |
73 | ||
ed632274 | 74 | static inline unsigned long mmap_base(unsigned long rnd) |
1da177e4 | 75 | { |
4bf936b9 | 76 | unsigned long gap = rlimit(RLIMIT_STACK); |
1da177e4 LT |
77 | |
78 | if (gap < MIN_GAP) | |
79 | gap = MIN_GAP; | |
80 | else if (gap > MAX_GAP) | |
81 | gap = MAX_GAP; | |
82 | ||
f4ea6dcb | 83 | return PAGE_ALIGN(DEFAULT_MAP_WINDOW - gap - rnd); |
1da177e4 LT |
84 | } |
85 | ||
7a0eedee AK |
86 | #ifdef CONFIG_PPC_RADIX_MMU |
87 | /* | |
88 | * Same function as generic code used only for radix, because we don't need to overload | |
89 | * the generic one. But we will have to duplicate, because hash select | |
90 | * HAVE_ARCH_UNMAPPED_AREA | |
91 | */ | |
92 | static unsigned long | |
93 | radix__arch_get_unmapped_area(struct file *filp, unsigned long addr, | |
94 | unsigned long len, unsigned long pgoff, | |
95 | unsigned long flags) | |
96 | { | |
97 | struct mm_struct *mm = current->mm; | |
98 | struct vm_area_struct *vma; | |
99 | struct vm_unmapped_area_info info; | |
100 | ||
321f7d29 AK |
101 | if (unlikely(addr > mm->context.addr_limit && |
102 | mm->context.addr_limit != TASK_SIZE)) | |
f4ea6dcb AK |
103 | mm->context.addr_limit = TASK_SIZE; |
104 | ||
be77e999 | 105 | if (len > mm->task_size - mmap_min_addr) |
7a0eedee AK |
106 | return -ENOMEM; |
107 | ||
108 | if (flags & MAP_FIXED) | |
109 | return addr; | |
110 | ||
111 | if (addr) { | |
112 | addr = PAGE_ALIGN(addr); | |
113 | vma = find_vma(mm, addr); | |
be77e999 | 114 | if (mm->task_size - len >= addr && addr >= mmap_min_addr && |
1be7107f | 115 | (!vma || addr + len <= vm_start_gap(vma))) |
7a0eedee AK |
116 | return addr; |
117 | } | |
118 | ||
119 | info.flags = 0; | |
120 | info.length = len; | |
121 | info.low_limit = mm->mmap_base; | |
7a0eedee | 122 | info.align_mask = 0; |
f4ea6dcb AK |
123 | |
124 | if (unlikely(addr > DEFAULT_MAP_WINDOW)) | |
125 | info.high_limit = mm->context.addr_limit; | |
126 | else | |
127 | info.high_limit = DEFAULT_MAP_WINDOW; | |
128 | ||
7a0eedee AK |
129 | return vm_unmapped_area(&info); |
130 | } | |
131 | ||
132 | static unsigned long | |
133 | radix__arch_get_unmapped_area_topdown(struct file *filp, | |
134 | const unsigned long addr0, | |
135 | const unsigned long len, | |
136 | const unsigned long pgoff, | |
137 | const unsigned long flags) | |
138 | { | |
139 | struct vm_area_struct *vma; | |
140 | struct mm_struct *mm = current->mm; | |
141 | unsigned long addr = addr0; | |
142 | struct vm_unmapped_area_info info; | |
143 | ||
321f7d29 AK |
144 | if (unlikely(addr > mm->context.addr_limit && |
145 | mm->context.addr_limit != TASK_SIZE)) | |
f4ea6dcb AK |
146 | mm->context.addr_limit = TASK_SIZE; |
147 | ||
7a0eedee | 148 | /* requested length too big for entire address space */ |
be77e999 | 149 | if (len > mm->task_size - mmap_min_addr) |
7a0eedee AK |
150 | return -ENOMEM; |
151 | ||
152 | if (flags & MAP_FIXED) | |
153 | return addr; | |
154 | ||
155 | /* requesting a specific address */ | |
156 | if (addr) { | |
157 | addr = PAGE_ALIGN(addr); | |
158 | vma = find_vma(mm, addr); | |
be77e999 | 159 | if (mm->task_size - len >= addr && addr >= mmap_min_addr && |
1be7107f | 160 | (!vma || addr + len <= vm_start_gap(vma))) |
7a0eedee AK |
161 | return addr; |
162 | } | |
163 | ||
164 | info.flags = VM_UNMAPPED_AREA_TOPDOWN; | |
165 | info.length = len; | |
166 | info.low_limit = max(PAGE_SIZE, mmap_min_addr); | |
167 | info.high_limit = mm->mmap_base; | |
168 | info.align_mask = 0; | |
f4ea6dcb AK |
169 | |
170 | if (addr > DEFAULT_MAP_WINDOW) | |
171 | info.high_limit += mm->context.addr_limit - DEFAULT_MAP_WINDOW; | |
172 | ||
7a0eedee | 173 | addr = vm_unmapped_area(&info); |
f4ea6dcb AK |
174 | if (!(addr & ~PAGE_MASK)) |
175 | return addr; | |
176 | VM_BUG_ON(addr != -ENOMEM); | |
7a0eedee AK |
177 | |
178 | /* | |
179 | * A failed mmap() very likely causes application failure, | |
180 | * so fall back to the bottom-up function here. This scenario | |
181 | * can happen with large stack limits and large mmap() | |
182 | * allocations. | |
183 | */ | |
f4ea6dcb | 184 | return radix__arch_get_unmapped_area(filp, addr0, len, pgoff, flags); |
7a0eedee AK |
185 | } |
186 | ||
187 | static void radix__arch_pick_mmap_layout(struct mm_struct *mm, | |
188 | unsigned long random_factor) | |
189 | { | |
190 | if (mmap_is_legacy()) { | |
191 | mm->mmap_base = TASK_UNMAPPED_BASE; | |
192 | mm->get_unmapped_area = radix__arch_get_unmapped_area; | |
193 | } else { | |
194 | mm->mmap_base = mmap_base(random_factor); | |
195 | mm->get_unmapped_area = radix__arch_get_unmapped_area_topdown; | |
196 | } | |
197 | } | |
198 | #else | |
199 | /* dummy */ | |
200 | extern void radix__arch_pick_mmap_layout(struct mm_struct *mm, | |
201 | unsigned long random_factor); | |
202 | #endif | |
1da177e4 LT |
203 | /* |
204 | * This function, called very early during the creation of a new | |
205 | * process VM image, sets up which VM layout function to use: | |
206 | */ | |
207 | void arch_pick_mmap_layout(struct mm_struct *mm) | |
208 | { | |
ed632274 KC |
209 | unsigned long random_factor = 0UL; |
210 | ||
211 | if (current->flags & PF_RANDOMIZE) | |
2b68f6ca | 212 | random_factor = arch_mmap_rnd(); |
ed632274 | 213 | |
7a0eedee AK |
214 | if (radix_enabled()) |
215 | return radix__arch_pick_mmap_layout(mm, random_factor); | |
1da177e4 LT |
216 | /* |
217 | * Fall back to the standard layout if the personality | |
218 | * bit is set, or if the expected stack growth is unlimited: | |
219 | */ | |
220 | if (mmap_is_legacy()) { | |
221 | mm->mmap_base = TASK_UNMAPPED_BASE; | |
222 | mm->get_unmapped_area = arch_get_unmapped_area; | |
1da177e4 | 223 | } else { |
ed632274 | 224 | mm->mmap_base = mmap_base(random_factor); |
1da177e4 | 225 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; |
1da177e4 LT |
226 | } |
227 | } |