LXR linux/arch/powerpc/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/sched.h>
  28
  29/*
  30 * Top of mmap area (just below the process stack).
  31 *
  32 * Leave an at least ~128 MB hole.
  33 */
  34#define MIN_GAP (128*1024*1024)
  35#define MAX_GAP (TASK_SIZE/6*5)
  36
  37static inline unsigned long mmap_base(void)
  38{
  39        unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;
  40
  41        if (gap < MIN_GAP)
  42                gap = MIN_GAP;
  43        else if (gap > MAX_GAP)
  44                gap = MAX_GAP;
  45
  46        return TASK_SIZE - (gap & PAGE_MASK);
  47}
  48
  49static inline int mmap_is_legacy(void)
  50{
  51        /*
  52         * Force standard allocation for 64 bit programs.
  53         */
  54        if (!test_thread_flag(TIF_32BIT))
  55                return 1;
  56
  57        if (current->personality & ADDR_COMPAT_LAYOUT)
  58                return 1;
  59
  60        if (current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY)
  61                return 1;
  62
  63        return sysctl_legacy_va_layout;
  64}
  65
  66/*
  67 * This function, called very early during the creation of a new
  68 * process VM image, sets up which VM layout function to use:
  69 */
  70void arch_pick_mmap_layout(struct mm_struct *mm)
  71{
  72        /*
  73         * Fall back to the standard layout if the personality
  74         * bit is set, or if the expected stack growth is unlimited:
  75         */
  76        if (mmap_is_legacy()) {
  77                mm->mmap_base = TASK_UNMAPPED_BASE;
  78                mm->get_unmapped_area = arch_get_unmapped_area;
  79                mm->unmap_area = arch_unmap_area;
  80        } else {
  81                mm->mmap_base = mmap_base();
  82                mm->get_unmapped_area = arch_get_unmapped_area_topdown;
  83                mm->unmap_area = arch_unmap_area_topdown;
  84        }
  85}
  86