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1 /*
2  *  linux/arch/s390/mm/mmap.c
3  *
4  *  flexible mmap layout support
5  *
6  * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
7  * All Rights Reserved.
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License as published by
11  * the Free Software Foundation; either version 2 of the License, or
12  * (at your option) any later version.
13  *
14  * This program is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17  * GNU General Public License for more details.
18  *
19  * You should have received a copy of the GNU General Public License
20  * along with this program; if not, write to the Free Software
21  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
22  *
23  *
24  * Started by Ingo Molnar <mingo@elte.hu>
25  */
26 
27 #include <linux/personality.h>
28 #include <linux/mm.h>
29 #include <linux/mman.h>
30 #include <linux/module.h>
31 #include <linux/random.h>
32 #include <linux/compat.h>
33 #include <asm/pgalloc.h>
34 
stack_maxrandom_size(void)35 static unsigned long stack_maxrandom_size(void)
36 {
37 	if (!(current->flags & PF_RANDOMIZE))
38 		return 0;
39 	if (current->personality & ADDR_NO_RANDOMIZE)
40 		return 0;
41 	return STACK_RND_MASK << PAGE_SHIFT;
42 }
43 
44 /*
45  * Top of mmap area (just below the process stack).
46  *
47  * Leave at least a ~32 MB hole.
48  */
49 #define MIN_GAP (32*1024*1024)
50 #define MAX_GAP (STACK_TOP/6*5)
51 
mmap_is_legacy(void)52 static inline int mmap_is_legacy(void)
53 {
54 	if (current->personality & ADDR_COMPAT_LAYOUT)
55 		return 1;
56 	if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
57 		return 1;
58 	return sysctl_legacy_va_layout;
59 }
60 
mmap_rnd(void)61 static unsigned long mmap_rnd(void)
62 {
63 	if (!(current->flags & PF_RANDOMIZE))
64 		return 0;
65 	/* 8MB randomization for mmap_base */
66 	return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
67 }
68 
mmap_base(void)69 static inline unsigned long mmap_base(void)
70 {
71 	unsigned long gap = rlimit(RLIMIT_STACK);
72 
73 	if (gap < MIN_GAP)
74 		gap = MIN_GAP;
75 	else if (gap > MAX_GAP)
76 		gap = MAX_GAP;
77 	gap &= PAGE_MASK;
78 	return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;
79 }
80 
81 #ifndef CONFIG_64BIT
82 
83 /*
84  * This function, called very early during the creation of a new
85  * process VM image, sets up which VM layout function to use:
86  */
arch_pick_mmap_layout(struct mm_struct * mm)87 void arch_pick_mmap_layout(struct mm_struct *mm)
88 {
89 	/*
90 	 * Fall back to the standard layout if the personality
91 	 * bit is set, or if the expected stack growth is unlimited:
92 	 */
93 	if (mmap_is_legacy()) {
94 		mm->mmap_base = TASK_UNMAPPED_BASE;
95 		mm->get_unmapped_area = arch_get_unmapped_area;
96 		mm->unmap_area = arch_unmap_area;
97 	} else {
98 		mm->mmap_base = mmap_base();
99 		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
100 		mm->unmap_area = arch_unmap_area_topdown;
101 	}
102 }
103 
104 #else
105 
s390_mmap_check(unsigned long addr,unsigned long len)106 int s390_mmap_check(unsigned long addr, unsigned long len)
107 {
108 	int rc;
109 
110 	if (!is_compat_task() &&
111 	    len >= TASK_SIZE && TASK_SIZE < (1UL << 53)) {
112 		rc = crst_table_upgrade(current->mm, 1UL << 53);
113 		if (rc)
114 			return rc;
115 		update_mm(current->mm, current);
116 	}
117 	return 0;
118 }
119 
120 static unsigned long
s390_get_unmapped_area(struct file * filp,unsigned long addr,unsigned long len,unsigned long pgoff,unsigned long flags)121 s390_get_unmapped_area(struct file *filp, unsigned long addr,
122 		unsigned long len, unsigned long pgoff, unsigned long flags)
123 {
124 	struct mm_struct *mm = current->mm;
125 	unsigned long area;
126 	int rc;
127 
128 	area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
129 	if (!(area & ~PAGE_MASK))
130 		return area;
131 	if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
132 		/* Upgrade the page table to 4 levels and retry. */
133 		rc = crst_table_upgrade(mm, 1UL << 53);
134 		if (rc)
135 			return (unsigned long) rc;
136 		update_mm(mm, current);
137 		area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
138 	}
139 	return area;
140 }
141 
142 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)143 s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
144 			  const unsigned long len, const unsigned long pgoff,
145 			  const unsigned long flags)
146 {
147 	struct mm_struct *mm = current->mm;
148 	unsigned long area;
149 	int rc;
150 
151 	area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
152 	if (!(area & ~PAGE_MASK))
153 		return area;
154 	if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
155 		/* Upgrade the page table to 4 levels and retry. */
156 		rc = crst_table_upgrade(mm, 1UL << 53);
157 		if (rc)
158 			return (unsigned long) rc;
159 		update_mm(mm, current);
160 		area = arch_get_unmapped_area_topdown(filp, addr, len,
161 						      pgoff, flags);
162 	}
163 	return area;
164 }
165 /*
166  * This function, called very early during the creation of a new
167  * process VM image, sets up which VM layout function to use:
168  */
arch_pick_mmap_layout(struct mm_struct * mm)169 void arch_pick_mmap_layout(struct mm_struct *mm)
170 {
171 	/*
172 	 * Fall back to the standard layout if the personality
173 	 * bit is set, or if the expected stack growth is unlimited:
174 	 */
175 	if (mmap_is_legacy()) {
176 		mm->mmap_base = TASK_UNMAPPED_BASE;
177 		mm->get_unmapped_area = s390_get_unmapped_area;
178 		mm->unmap_area = arch_unmap_area;
179 	} else {
180 		mm->mmap_base = mmap_base();
181 		mm->get_unmapped_area = s390_get_unmapped_area_topdown;
182 		mm->unmap_area = arch_unmap_area_topdown;
183 	}
184 }
185 
186 #endif
187