linux/arch/tile/mm/mmap.c
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   1/*
   2 * Copyright 2010 Tilera Corporation. All Rights Reserved.
   3 *
   4 *   This program is free software; you can redistribute it and/or
   5 *   modify it under the terms of the GNU General Public License
   6 *   as published by the Free Software Foundation, version 2.
   7 *
   8 *   This program is distributed in the hope that it will be useful, but
   9 *   WITHOUT ANY WARRANTY; without even the implied warranty of
  10 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  11 *   NON INFRINGEMENT.  See the GNU General Public License for
  12 *   more details.
  13 *
  14 * Taken from the i386 architecture and simplified.
  15 */
  16
  17#include <linux/mm.h>
  18#include <linux/random.h>
  19#include <linux/limits.h>
  20#include <linux/sched.h>
  21#include <linux/mman.h>
  22#include <linux/compat.h>
  23
  24/*
  25 * Top of mmap area (just below the process stack).
  26 *
  27 * Leave an at least ~128 MB hole.
  28 */
  29#define MIN_GAP (128*1024*1024)
  30#define MAX_GAP (TASK_SIZE/6*5)
  31
  32static inline unsigned long mmap_base(struct mm_struct *mm)
  33{
  34        unsigned long gap = rlimit(RLIMIT_STACK);
  35        unsigned long random_factor = 0;
  36
  37        if (current->flags & PF_RANDOMIZE)
  38                random_factor = get_random_int() % (1024*1024);
  39
  40        if (gap < MIN_GAP)
  41                gap = MIN_GAP;
  42        else if (gap > MAX_GAP)
  43                gap = MAX_GAP;
  44
  45        return PAGE_ALIGN(TASK_SIZE - gap - random_factor);
  46}
  47
  48/*
  49 * This function, called very early during the creation of a new
  50 * process VM image, sets up which VM layout function to use:
  51 */
  52void arch_pick_mmap_layout(struct mm_struct *mm)
  53{
  54#if !defined(__tilegx__)
  55        int is_32bit = 1;
  56#elif defined(CONFIG_COMPAT)
  57        int is_32bit = is_compat_task();
  58#else
  59        int is_32bit = 0;
  60#endif
  61
  62        /*
  63         * Use standard layout if the expected stack growth is unlimited
  64         * or we are running native 64 bits.
  65         */
  66        if (!is_32bit || rlimit(RLIMIT_STACK) == RLIM_INFINITY) {
  67                mm->mmap_base = TASK_UNMAPPED_BASE;
  68                mm->get_unmapped_area = arch_get_unmapped_area;
  69        } else {
  70                mm->mmap_base = mmap_base(mm);
  71                mm->get_unmapped_area = arch_get_unmapped_area_topdown;
  72        }
  73}
  74