Commit | Line | Data |
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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> |
e8edc6e0 | 28 | #include <linux/sched.h> |
7f92bc56 | 29 | #include <linux/elf-randomize.h> |
7a0eedee AK |
30 | #include <linux/security.h> |
31 | #include <linux/mman.h> | |
1da177e4 LT |
32 | |
33 | /* | |
34 | * Top of mmap area (just below the process stack). | |
35 | * | |
002b0ec7 AB |
36 | * Leave at least a ~128 MB hole on 32bit applications. |
37 | * | |
38 | * On 64bit applications we randomise the stack by 1GB so we need to | |
39 | * space our mmap start address by a further 1GB, otherwise there is a | |
40 | * chance the mmap area will end up closer to the stack than our ulimit | |
41 | * requires. | |
1da177e4 | 42 | */ |
002b0ec7 AB |
43 | #define MIN_GAP32 (128*1024*1024) |
44 | #define MIN_GAP64 ((128 + 1024)*1024*1024UL) | |
45 | #define MIN_GAP ((is_32bit_task()) ? MIN_GAP32 : MIN_GAP64) | |
1da177e4 LT |
46 | #define MAX_GAP (TASK_SIZE/6*5) |
47 | ||
13a2cb36 AB |
48 | static inline int mmap_is_legacy(void) |
49 | { | |
50 | if (current->personality & ADDR_COMPAT_LAYOUT) | |
51 | return 1; | |
52 | ||
4bf936b9 | 53 | if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) |
13a2cb36 AB |
54 | return 1; |
55 | ||
56 | return sysctl_legacy_va_layout; | |
57 | } | |
58 | ||
2b68f6ca | 59 | unsigned long arch_mmap_rnd(void) |
9f14c42d | 60 | { |
ed632274 KC |
61 | unsigned long rnd; |
62 | ||
63 | /* 8MB for 32bit, 1GB for 64bit */ | |
64 | if (is_32bit_task()) | |
5ef11c35 | 65 | rnd = get_random_long() % (1<<(23-PAGE_SHIFT)); |
ed632274 | 66 | else |
5ef11c35 | 67 | rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT)); |
9f14c42d | 68 | |
fa8cbaaf | 69 | return rnd << PAGE_SHIFT; |
9f14c42d AB |
70 | } |
71 | ||
ed632274 | 72 | static inline unsigned long mmap_base(unsigned long rnd) |
1da177e4 | 73 | { |
4bf936b9 | 74 | unsigned long gap = rlimit(RLIMIT_STACK); |
1da177e4 LT |
75 | |
76 | if (gap < MIN_GAP) | |
77 | gap = MIN_GAP; | |
78 | else if (gap > MAX_GAP) | |
79 | gap = MAX_GAP; | |
80 | ||
ed632274 | 81 | return PAGE_ALIGN(TASK_SIZE - gap - rnd); |
1da177e4 LT |
82 | } |
83 | ||
7a0eedee AK |
84 | #ifdef CONFIG_PPC_RADIX_MMU |
85 | /* | |
86 | * Same function as generic code used only for radix, because we don't need to overload | |
87 | * the generic one. But we will have to duplicate, because hash select | |
88 | * HAVE_ARCH_UNMAPPED_AREA | |
89 | */ | |
90 | static unsigned long | |
91 | radix__arch_get_unmapped_area(struct file *filp, unsigned long addr, | |
92 | unsigned long len, unsigned long pgoff, | |
93 | unsigned long flags) | |
94 | { | |
95 | struct mm_struct *mm = current->mm; | |
96 | struct vm_area_struct *vma; | |
97 | struct vm_unmapped_area_info info; | |
98 | ||
99 | if (len > TASK_SIZE - mmap_min_addr) | |
100 | return -ENOMEM; | |
101 | ||
102 | if (flags & MAP_FIXED) | |
103 | return addr; | |
104 | ||
105 | if (addr) { | |
106 | addr = PAGE_ALIGN(addr); | |
107 | vma = find_vma(mm, addr); | |
108 | if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && | |
109 | (!vma || addr + len <= vma->vm_start)) | |
110 | return addr; | |
111 | } | |
112 | ||
113 | info.flags = 0; | |
114 | info.length = len; | |
115 | info.low_limit = mm->mmap_base; | |
116 | info.high_limit = TASK_SIZE; | |
117 | info.align_mask = 0; | |
118 | return vm_unmapped_area(&info); | |
119 | } | |
120 | ||
121 | static unsigned long | |
122 | radix__arch_get_unmapped_area_topdown(struct file *filp, | |
123 | const unsigned long addr0, | |
124 | const unsigned long len, | |
125 | const unsigned long pgoff, | |
126 | const unsigned long flags) | |
127 | { | |
128 | struct vm_area_struct *vma; | |
129 | struct mm_struct *mm = current->mm; | |
130 | unsigned long addr = addr0; | |
131 | struct vm_unmapped_area_info info; | |
132 | ||
133 | /* requested length too big for entire address space */ | |
134 | if (len > TASK_SIZE - mmap_min_addr) | |
135 | return -ENOMEM; | |
136 | ||
137 | if (flags & MAP_FIXED) | |
138 | return addr; | |
139 | ||
140 | /* requesting a specific address */ | |
141 | if (addr) { | |
142 | addr = PAGE_ALIGN(addr); | |
143 | vma = find_vma(mm, addr); | |
144 | if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && | |
145 | (!vma || addr + len <= vma->vm_start)) | |
146 | return addr; | |
147 | } | |
148 | ||
149 | info.flags = VM_UNMAPPED_AREA_TOPDOWN; | |
150 | info.length = len; | |
151 | info.low_limit = max(PAGE_SIZE, mmap_min_addr); | |
152 | info.high_limit = mm->mmap_base; | |
153 | info.align_mask = 0; | |
154 | addr = vm_unmapped_area(&info); | |
155 | ||
156 | /* | |
157 | * A failed mmap() very likely causes application failure, | |
158 | * so fall back to the bottom-up function here. This scenario | |
159 | * can happen with large stack limits and large mmap() | |
160 | * allocations. | |
161 | */ | |
162 | if (addr & ~PAGE_MASK) { | |
163 | VM_BUG_ON(addr != -ENOMEM); | |
164 | info.flags = 0; | |
165 | info.low_limit = TASK_UNMAPPED_BASE; | |
166 | info.high_limit = TASK_SIZE; | |
167 | addr = vm_unmapped_area(&info); | |
168 | } | |
169 | ||
170 | return addr; | |
171 | } | |
172 | ||
173 | static void radix__arch_pick_mmap_layout(struct mm_struct *mm, | |
174 | unsigned long random_factor) | |
175 | { | |
176 | if (mmap_is_legacy()) { | |
177 | mm->mmap_base = TASK_UNMAPPED_BASE; | |
178 | mm->get_unmapped_area = radix__arch_get_unmapped_area; | |
179 | } else { | |
180 | mm->mmap_base = mmap_base(random_factor); | |
181 | mm->get_unmapped_area = radix__arch_get_unmapped_area_topdown; | |
182 | } | |
183 | } | |
184 | #else | |
185 | /* dummy */ | |
186 | extern void radix__arch_pick_mmap_layout(struct mm_struct *mm, | |
187 | unsigned long random_factor); | |
188 | #endif | |
1da177e4 LT |
189 | /* |
190 | * This function, called very early during the creation of a new | |
191 | * process VM image, sets up which VM layout function to use: | |
192 | */ | |
193 | void arch_pick_mmap_layout(struct mm_struct *mm) | |
194 | { | |
ed632274 KC |
195 | unsigned long random_factor = 0UL; |
196 | ||
197 | if (current->flags & PF_RANDOMIZE) | |
2b68f6ca | 198 | random_factor = arch_mmap_rnd(); |
ed632274 | 199 | |
7a0eedee AK |
200 | if (radix_enabled()) |
201 | return radix__arch_pick_mmap_layout(mm, random_factor); | |
1da177e4 LT |
202 | /* |
203 | * Fall back to the standard layout if the personality | |
204 | * bit is set, or if the expected stack growth is unlimited: | |
205 | */ | |
206 | if (mmap_is_legacy()) { | |
207 | mm->mmap_base = TASK_UNMAPPED_BASE; | |
208 | mm->get_unmapped_area = arch_get_unmapped_area; | |
1da177e4 | 209 | } else { |
ed632274 | 210 | mm->mmap_base = mmap_base(random_factor); |
1da177e4 | 211 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; |
1da177e4 LT |
212 | } |
213 | } |