Commit | Line | Data |
---|---|---|
cc503c1b | 1 | /* |
675a0813 | 2 | * Flexible mmap layout support |
cc503c1b JK |
3 | * |
4 | * Based on code by Ingo Molnar and Andi Kleen, copyrighted | |
5 | * as follows: | |
6 | * | |
8f47e163 | 7 | * Copyright 2003-2009 Red Hat Inc. |
cc503c1b JK |
8 | * All Rights Reserved. |
9 | * Copyright 2005 Andi Kleen, SUSE Labs. | |
10 | * Copyright 2007 Jiri Kosina, SUSE Labs. | |
11 | * | |
12 | * This program is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU General Public License as published by | |
14 | * the Free Software Foundation; either version 2 of the License, or | |
15 | * (at your option) any later version. | |
16 | * | |
17 | * This program is distributed in the hope that it will be useful, | |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | * GNU General Public License for more details. | |
21 | * | |
22 | * You should have received a copy of the GNU General Public License | |
23 | * along with this program; if not, write to the Free Software | |
24 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
8817210d | 25 | */ |
cc503c1b JK |
26 | |
27 | #include <linux/personality.h> | |
8817210d | 28 | #include <linux/mm.h> |
8817210d | 29 | #include <linux/random.h> |
cc503c1b JK |
30 | #include <linux/limits.h> |
31 | #include <linux/sched.h> | |
80938332 MH |
32 | #include <asm/elf.h> |
33 | ||
9387f774 BP |
34 | struct __read_mostly va_alignment va_align = { |
35 | .flags = -1, | |
36 | }; | |
37 | ||
80938332 MH |
38 | static unsigned int stack_maxrandom_size(void) |
39 | { | |
40 | unsigned int max = 0; | |
41 | if ((current->flags & PF_RANDOMIZE) && | |
42 | !(current->personality & ADDR_NO_RANDOMIZE)) { | |
43 | max = ((-1U) & STACK_RND_MASK) << PAGE_SHIFT; | |
44 | } | |
45 | ||
46 | return max; | |
47 | } | |
48 | ||
cc503c1b JK |
49 | /* |
50 | * Top of mmap area (just below the process stack). | |
51 | * | |
80938332 | 52 | * Leave an at least ~128 MB hole with possible stack randomization. |
cc503c1b | 53 | */ |
80938332 | 54 | #define MIN_GAP (128*1024*1024UL + stack_maxrandom_size()) |
cc503c1b | 55 | #define MAX_GAP (TASK_SIZE/6*5) |
8817210d | 56 | |
954683a2 | 57 | static int mmap_is_legacy(void) |
cc503c1b JK |
58 | { |
59 | if (current->personality & ADDR_COMPAT_LAYOUT) | |
60 | return 1; | |
61 | ||
2854e72b | 62 | if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) |
cc503c1b JK |
63 | return 1; |
64 | ||
65 | return sysctl_legacy_va_layout; | |
66 | } | |
67 | ||
675a0813 HH |
68 | static unsigned long mmap_rnd(void) |
69 | { | |
70 | unsigned long rnd = 0; | |
71 | ||
72 | /* | |
73 | * 8 bits of randomness in 32bit mmaps, 20 address space bits | |
74 | * 28 bits of randomness in 64bit mmaps, 40 address space bits | |
75 | */ | |
76 | if (current->flags & PF_RANDOMIZE) { | |
77 | if (mmap_is_ia32()) | |
9af0c7a6 | 78 | rnd = get_random_int() % (1<<8); |
675a0813 | 79 | else |
9af0c7a6 | 80 | rnd = get_random_int() % (1<<28); |
675a0813 HH |
81 | } |
82 | return rnd << PAGE_SHIFT; | |
83 | } | |
84 | ||
85 | static unsigned long mmap_base(void) | |
86 | { | |
2854e72b | 87 | unsigned long gap = rlimit(RLIMIT_STACK); |
675a0813 HH |
88 | |
89 | if (gap < MIN_GAP) | |
90 | gap = MIN_GAP; | |
91 | else if (gap > MAX_GAP) | |
92 | gap = MAX_GAP; | |
93 | ||
94 | return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd()); | |
95 | } | |
96 | ||
97 | /* | |
98 | * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64 | |
99 | * does, but not when emulating X86_32 | |
100 | */ | |
101 | static unsigned long mmap_legacy_base(void) | |
102 | { | |
103 | if (mmap_is_ia32()) | |
104 | return TASK_UNMAPPED_BASE; | |
105 | else | |
106 | return TASK_UNMAPPED_BASE + mmap_rnd(); | |
107 | } | |
108 | ||
cc503c1b JK |
109 | /* |
110 | * This function, called very early during the creation of a new | |
111 | * process VM image, sets up which VM layout function to use: | |
112 | */ | |
113 | void arch_pick_mmap_layout(struct mm_struct *mm) | |
114 | { | |
675a0813 HH |
115 | if (mmap_is_legacy()) { |
116 | mm->mmap_base = mmap_legacy_base(); | |
cc503c1b JK |
117 | mm->get_unmapped_area = arch_get_unmapped_area; |
118 | mm->unmap_area = arch_unmap_area; | |
119 | } else { | |
120 | mm->mmap_base = mmap_base(); | |
121 | mm->get_unmapped_area = arch_get_unmapped_area_topdown; | |
122 | mm->unmap_area = arch_unmap_area_topdown; | |
cc503c1b | 123 | } |
8817210d | 124 | } |