xref: /openbmc/linux/arch/s390/mm/mmap.c (revision e23feb16)
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 
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 
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 
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 
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  */
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 	} else {
95 		mm->mmap_base = mmap_base();
96 		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
97 	}
98 }
99 
100 #else
101 
102 int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
103 {
104 	int rc;
105 
106 	if (is_compat_task() || (TASK_SIZE >= (1UL << 53)))
107 		return 0;
108 	if (!(flags & MAP_FIXED))
109 		addr = 0;
110 	if ((addr + len) >= TASK_SIZE) {
111 		rc = crst_table_upgrade(current->mm, 1UL << 53);
112 		if (rc)
113 			return rc;
114 		update_mm(current->mm, current);
115 	}
116 	return 0;
117 }
118 
119 static unsigned long
120 s390_get_unmapped_area(struct file *filp, unsigned long addr,
121 		unsigned long len, unsigned long pgoff, unsigned long flags)
122 {
123 	struct mm_struct *mm = current->mm;
124 	unsigned long area;
125 	int rc;
126 
127 	area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
128 	if (!(area & ~PAGE_MASK))
129 		return area;
130 	if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
131 		/* Upgrade the page table to 4 levels and retry. */
132 		rc = crst_table_upgrade(mm, 1UL << 53);
133 		if (rc)
134 			return (unsigned long) rc;
135 		update_mm(mm, current);
136 		area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
137 	}
138 	return area;
139 }
140 
141 static unsigned long
142 s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
143 			  const unsigned long len, const unsigned long pgoff,
144 			  const unsigned long flags)
145 {
146 	struct mm_struct *mm = current->mm;
147 	unsigned long area;
148 	int rc;
149 
150 	area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
151 	if (!(area & ~PAGE_MASK))
152 		return area;
153 	if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
154 		/* Upgrade the page table to 4 levels and retry. */
155 		rc = crst_table_upgrade(mm, 1UL << 53);
156 		if (rc)
157 			return (unsigned long) rc;
158 		update_mm(mm, current);
159 		area = arch_get_unmapped_area_topdown(filp, addr, len,
160 						      pgoff, flags);
161 	}
162 	return area;
163 }
164 /*
165  * This function, called very early during the creation of a new
166  * process VM image, sets up which VM layout function to use:
167  */
168 void arch_pick_mmap_layout(struct mm_struct *mm)
169 {
170 	/*
171 	 * Fall back to the standard layout if the personality
172 	 * bit is set, or if the expected stack growth is unlimited:
173 	 */
174 	if (mmap_is_legacy()) {
175 		mm->mmap_base = TASK_UNMAPPED_BASE;
176 		mm->get_unmapped_area = s390_get_unmapped_area;
177 	} else {
178 		mm->mmap_base = mmap_base();
179 		mm->get_unmapped_area = s390_get_unmapped_area_topdown;
180 	}
181 }
182 
183 #endif
184