LXR linux/arch/s390/mm/mmap.c

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