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1/*
2 * Flexible mmap layout support
3 *
4 * Based on code by Ingo Molnar and Andi Kleen, copyrighted
5 * as follows:
6 *
7 * Copyright 2003-2009 Red Hat Inc.
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
25 */
26
27#include <linux/personality.h>
28#include <linux/mm.h>
29#include <linux/random.h>
30#include <linux/limits.h>
31#include <linux/sched.h>
32#include <asm/elf.h>
33
34struct __read_mostly va_alignment va_align = {
35 .flags = -1,
36};
37
38static 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
49/*
50 * Top of mmap area (just below the process stack).
51 *
52 * Leave an at least ~128 MB hole with possible stack randomization.
53 */
54#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size())
55#define MAX_GAP (TASK_SIZE/6*5)
56
57static int mmap_is_legacy(void)
58{
59 if (current->personality & ADDR_COMPAT_LAYOUT)
60 return 1;
61
62 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
63 return 1;
64
65 return sysctl_legacy_va_layout;
66}
67
68static 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())
78 rnd = get_random_int() % (1<<8);
79 else
80 rnd = get_random_int() % (1<<28);
81 }
82 return rnd << PAGE_SHIFT;
83}
84
85static unsigned long mmap_base(void)
86{
87 unsigned long gap = rlimit(RLIMIT_STACK);
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 */
101static 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
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 */
113void arch_pick_mmap_layout(struct mm_struct *mm)
114{
115 mm->mmap_legacy_base = mmap_legacy_base();
116 mm->mmap_base = mmap_base();
117
118 if (mmap_is_legacy()) {
119 mm->mmap_base = mm->mmap_legacy_base;
120 mm->get_unmapped_area = arch_get_unmapped_area;
121 } else {
122 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
123 }
124}
1/*
2 * Flexible mmap layout support
3 *
4 * Based on code by Ingo Molnar and Andi Kleen, copyrighted
5 * as follows:
6 *
7 * Copyright 2003-2009 Red Hat Inc.
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
25 */
26
27#include <linux/personality.h>
28#include <linux/mm.h>
29#include <linux/random.h>
30#include <linux/limits.h>
31#include <linux/sched.h>
32#include <asm/elf.h>
33
34static unsigned int stack_maxrandom_size(void)
35{
36 unsigned int max = 0;
37 if ((current->flags & PF_RANDOMIZE) &&
38 !(current->personality & ADDR_NO_RANDOMIZE)) {
39 max = ((-1U) & STACK_RND_MASK) << PAGE_SHIFT;
40 }
41
42 return max;
43}
44
45
46/*
47 * Top of mmap area (just below the process stack).
48 *
49 * Leave an at least ~128 MB hole with possible stack randomization.
50 */
51#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size())
52#define MAX_GAP (TASK_SIZE/6*5)
53
54/*
55 * True on X86_32 or when emulating IA32 on X86_64
56 */
57static int mmap_is_ia32(void)
58{
59#ifdef CONFIG_X86_32
60 return 1;
61#endif
62#ifdef CONFIG_IA32_EMULATION
63 if (test_thread_flag(TIF_IA32))
64 return 1;
65#endif
66 return 0;
67}
68
69static int mmap_is_legacy(void)
70{
71 if (current->personality & ADDR_COMPAT_LAYOUT)
72 return 1;
73
74 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
75 return 1;
76
77 return sysctl_legacy_va_layout;
78}
79
80static unsigned long mmap_rnd(void)
81{
82 unsigned long rnd = 0;
83
84 /*
85 * 8 bits of randomness in 32bit mmaps, 20 address space bits
86 * 28 bits of randomness in 64bit mmaps, 40 address space bits
87 */
88 if (current->flags & PF_RANDOMIZE) {
89 if (mmap_is_ia32())
90 rnd = (long)get_random_int() % (1<<8);
91 else
92 rnd = (long)(get_random_int() % (1<<28));
93 }
94 return rnd << PAGE_SHIFT;
95}
96
97static unsigned long mmap_base(void)
98{
99 unsigned long gap = rlimit(RLIMIT_STACK);
100
101 if (gap < MIN_GAP)
102 gap = MIN_GAP;
103 else if (gap > MAX_GAP)
104 gap = MAX_GAP;
105
106 return PAGE_ALIGN(TASK_SIZE - gap - mmap_rnd());
107}
108
109/*
110 * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64
111 * does, but not when emulating X86_32
112 */
113static unsigned long mmap_legacy_base(void)
114{
115 if (mmap_is_ia32())
116 return TASK_UNMAPPED_BASE;
117 else
118 return TASK_UNMAPPED_BASE + mmap_rnd();
119}
120
121/*
122 * This function, called very early during the creation of a new
123 * process VM image, sets up which VM layout function to use:
124 */
125void arch_pick_mmap_layout(struct mm_struct *mm)
126{
127 if (mmap_is_legacy()) {
128 mm->mmap_base = mmap_legacy_base();
129 mm->get_unmapped_area = arch_get_unmapped_area;
130 mm->unmap_area = arch_unmap_area;
131 } else {
132 mm->mmap_base = mmap_base();
133 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
134 mm->unmap_area = arch_unmap_area_topdown;
135 }
136}