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

   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
  33static 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
  50static 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
  59static 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
  67static unsigned long mmap_base_legacy(void)
  68{
  69        return TASK_UNMAPPED_BASE + mmap_rnd();
  70}
  71
  72static 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 */
  90void 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
 107int 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
 118static unsigned long
 119s390_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
 139static unsigned long
 140s390_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 */
 165void 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