blob: f96f4cec602ad6bd3f15e2502f6b35ae369bd05f [file] [log] [blame]
Chris Metcalf867e3592010-05-28 23:09:12 -04001/*
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 mm->unmap_area = arch_unmap_area;
70 } else {
71 mm->mmap_base = mmap_base(mm);
72 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
73 mm->unmap_area = arch_unmap_area_topdown;
74 }
75}