arch/powerpc/mm/mmap.c

   1 /*
   2  *  linux/arch/ppc64/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
  30 /*
  31  * Top of mmap area (just below the process stack).
  32  *
  33  * Leave an at least ~128 MB hole.
  34  */
  35 #define MIN_GAP (128*1024*1024)
  36 #define MAX_GAP (TASK_SIZE/6*5)
  37
  38 static inline unsigned long mmap_base(void)
  39 {
  40         unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;
  41
  42         if (gap < MIN_GAP)
  43                 gap = MIN_GAP;
  44         else if (gap > MAX_GAP)
  45                 gap = MAX_GAP;
  46
  47         return TASK_SIZE - (gap & PAGE_MASK);
  48 }
  49
  50 static inline int mmap_is_legacy(void)
  51 {
  52         /*
  53          * Force standard allocation for 64 bit programs.
  54          */
  55         if (!test_thread_flag(TIF_32BIT))
  56                 return 1;
  57
  58         if (current->personality & ADDR_COMPAT_LAYOUT)
  59                 return 1;
  60
  61         if (current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY)
  62                 return 1;
  63
  64         return sysctl_legacy_va_layout;
  65 }
  66
  67 /*
  68  * This function, called very early during the creation of a new
  69  * process VM image, sets up which VM layout function to use:
  70  */
  71 void arch_pick_mmap_layout(struct mm_struct *mm)
  72 {
  73         /*
  74          * Fall back to the standard layout if the personality
  75          * bit is set, or if the expected stack growth is unlimited:
  76          */
  77         if (mmap_is_legacy()) {
  78                 mm->mmap_base = TASK_UNMAPPED_BASE;
  79                 mm->get_unmapped_area = arch_get_unmapped_area;
  80                 mm->unmap_area = arch_unmap_area;
  81         } else {
  82                 mm->mmap_base = mmap_base();
  83                 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
  84                 mm->unmap_area = arch_unmap_area_topdown;
  85         }
  86 }