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Linux/arch/s390/mm/mmap.c

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  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 unsigned long mmap_base_legacy(void)
 68 {
 69         return TASK_UNMAPPED_BASE + mmap_rnd();
 70 }
 71 
 72 static inline unsigned long mmap_base(void)
 73 {
 74         unsigned long gap = rlimit(RLIMIT_STACK);
 75 
 76         if (gap < MIN_GAP)
 77                 gap = MIN_GAP;
 78         else if (gap > MAX_GAP)
 79                 gap = MAX_GAP;
 80         gap &= PAGE_MASK;
 81         return STACK_TOP - stack_maxrandom_size() - mmap_rnd() - gap;
 82 }
 83 
 84 #ifndef CONFIG_64BIT
 85 
 86 /*
 87  * This function, called very early during the creation of a new
 88  * process VM image, sets up which VM layout function to use:
 89  */
 90 void arch_pick_mmap_layout(struct mm_struct *mm)
 91 {
 92         /*
 93          * Fall back to the standard layout if the personality
 94          * bit is set, or if the expected stack growth is unlimited:
 95          */
 96         if (mmap_is_legacy()) {
 97                 mm->mmap_base = mmap_base_legacy();
 98                 mm->get_unmapped_area = arch_get_unmapped_area;
 99         } else {
100                 mm->mmap_base = mmap_base();
101                 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
102         }
103 }
104 
105 #else
106 
107 int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
108 {
109         if (is_compat_task() || (TASK_SIZE >= (1UL << 53)))
110                 return 0;
111         if (!(flags & MAP_FIXED))
112                 addr = 0;
113         if ((addr + len) >= TASK_SIZE)
114                 return crst_table_upgrade(current->mm, 1UL << 53);
115         return 0;
116 }
117 
118 static unsigned long
119 s390_get_unmapped_area(struct file *filp, unsigned long addr,
120                 unsigned long len, unsigned long pgoff, unsigned long flags)
121 {
122         struct mm_struct *mm = current->mm;
123         unsigned long area;
124         int rc;
125 
126         area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
127         if (!(area & ~PAGE_MASK))
128                 return area;
129         if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
130                 /* Upgrade the page table to 4 levels and retry. */
131                 rc = crst_table_upgrade(mm, 1UL << 53);
132                 if (rc)
133                         return (unsigned long) rc;
134                 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
135         }
136         return area;
137 }
138 
139 static unsigned long
140 s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
141                           const unsigned long len, const unsigned long pgoff,
142                           const unsigned long flags)
143 {
144         struct mm_struct *mm = current->mm;
145         unsigned long area;
146         int rc;
147 
148         area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
149         if (!(area & ~PAGE_MASK))
150                 return area;
151         if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
152                 /* Upgrade the page table to 4 levels and retry. */
153                 rc = crst_table_upgrade(mm, 1UL << 53);
154                 if (rc)
155                         return (unsigned long) rc;
156                 area = arch_get_unmapped_area_topdown(filp, addr, len,
157                                                       pgoff, flags);
158         }
159         return area;
160 }
161 /*
162  * This function, called very early during the creation of a new
163  * process VM image, sets up which VM layout function to use:
164  */
165 void arch_pick_mmap_layout(struct mm_struct *mm)
166 {
167         /*
168          * Fall back to the standard layout if the personality
169          * bit is set, or if the expected stack growth is unlimited:
170          */
171         if (mmap_is_legacy()) {
172                 mm->mmap_base = mmap_base_legacy();
173                 mm->get_unmapped_area = s390_get_unmapped_area;
174         } else {
175                 mm->mmap_base = mmap_base();
176                 mm->get_unmapped_area = s390_get_unmapped_area_topdown;
177         }
178 }
179 
180 #endif
181 

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