1 /*
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>
27 #include <linux/mman.h>
28 #include <linux/module.h>
29 #include <linux/random.h>
30 #include <linux/compat.h>
31 #include <asm/pgalloc.h>
32
stack_maxrandom_size(void)33 static unsigned long stack_maxrandom_size(void)
34 {
35 if (!(current->flags & PF_RANDOMIZE))
36 return 0;
37 if (current->personality & ADDR_NO_RANDOMIZE)
38 return 0;
39 return STACK_RND_MASK << PAGE_SHIFT;
40 }
41
42 /*
43 * Top of mmap area (just below the process stack).
44 *
45 * Leave at least a ~32 MB hole.
46 */
47 #define MIN_GAP (32*1024*1024)
48 #define MAX_GAP (STACK_TOP/6*5)
49
mmap_is_legacy(void)50 static inline int mmap_is_legacy(void)
51 {
52 if (current->personality & ADDR_COMPAT_LAYOUT)
53 return 1;
54 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
55 return 1;
56 return sysctl_legacy_va_layout;
57 }
58
mmap_rnd(void)59 static unsigned long mmap_rnd(void)
60 {
61 if (!(current->flags & PF_RANDOMIZE))
62 return 0;
63 /* 8MB randomization for mmap_base */
64 return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
65 }
66
mmap_base(void)67 static inline unsigned long mmap_base(void)
68 {
69 unsigned long gap = rlimit(RLIMIT_STACK);
70
71 if (gap < MIN_GAP)
72 gap = MIN_GAP;
73 else if (gap > MAX_GAP)
74 gap = MAX_GAP;
75 gap &= PAGE_MASK;
76 return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;
77 }
78
79 #ifndef CONFIG_64BIT
80
81 /*
82 * This function, called very early during the creation of a new
83 * process VM image, sets up which VM layout function to use:
84 */
arch_pick_mmap_layout(struct mm_struct * mm)85 void arch_pick_mmap_layout(struct mm_struct *mm)
86 {
87 /*
88 * Fall back to the standard layout if the personality
89 * bit is set, or if the expected stack growth is unlimited:
90 */
91 if (mmap_is_legacy()) {
92 mm->mmap_base = TASK_UNMAPPED_BASE;
93 mm->get_unmapped_area = arch_get_unmapped_area;
94 mm->unmap_area = arch_unmap_area;
95 } else {
96 mm->mmap_base = mmap_base();
97 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
98 mm->unmap_area = arch_unmap_area_topdown;
99 }
100 }
101
102 #else
103
s390_mmap_check(unsigned long addr,unsigned long len,unsigned long flags)104 int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
105 {
106 int rc;
107
108 if (is_compat_task() || (TASK_SIZE >= (1UL << 53)))
109 return 0;
110 if (!(flags & MAP_FIXED))
111 addr = 0;
112 if ((addr + len) >= TASK_SIZE) {
113 rc = crst_table_upgrade(current->mm, 1UL << 53);
114 if (rc)
115 return rc;
116 update_mm(current->mm, current);
117 }
118 return 0;
119 }
120
121 static unsigned long
s390_get_unmapped_area(struct file * filp,unsigned long addr,unsigned long len,unsigned long pgoff,unsigned long flags)122 s390_get_unmapped_area(struct file *filp, unsigned long addr,
123 unsigned long len, unsigned long pgoff, unsigned long flags)
124 {
125 struct mm_struct *mm = current->mm;
126 unsigned long area;
127 int rc;
128
129 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
130 if (!(area & ~PAGE_MASK))
131 return area;
132 if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
133 /* Upgrade the page table to 4 levels and retry. */
134 rc = crst_table_upgrade(mm, 1UL << 53);
135 if (rc)
136 return (unsigned long) rc;
137 update_mm(mm, current);
138 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
139 }
140 return area;
141 }
142
143 static unsigned long
s390_get_unmapped_area_topdown(struct file * filp,const unsigned long addr,const unsigned long len,const unsigned long pgoff,const unsigned long flags)144 s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
145 const unsigned long len, const unsigned long pgoff,
146 const unsigned long flags)
147 {
148 struct mm_struct *mm = current->mm;
149 unsigned long area;
150 int rc;
151
152 area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
153 if (!(area & ~PAGE_MASK))
154 return area;
155 if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
156 /* Upgrade the page table to 4 levels and retry. */
157 rc = crst_table_upgrade(mm, 1UL << 53);
158 if (rc)
159 return (unsigned long) rc;
160 update_mm(mm, current);
161 area = arch_get_unmapped_area_topdown(filp, addr, len,
162 pgoff, flags);
163 }
164 return area;
165 }
166 /*
167 * This function, called very early during the creation of a new
168 * process VM image, sets up which VM layout function to use:
169 */
arch_pick_mmap_layout(struct mm_struct * mm)170 void arch_pick_mmap_layout(struct mm_struct *mm)
171 {
172 /*
173 * Fall back to the standard layout if the personality
174 * bit is set, or if the expected stack growth is unlimited:
175 */
176 if (mmap_is_legacy()) {
177 mm->mmap_base = TASK_UNMAPPED_BASE;
178 mm->get_unmapped_area = s390_get_unmapped_area;
179 mm->unmap_area = arch_unmap_area;
180 } else {
181 mm->mmap_base = mmap_base();
182 mm->get_unmapped_area = s390_get_unmapped_area_topdown;
183 mm->unmap_area = arch_unmap_area_topdown;
184 }
185 }
186
187 #endif
188