blob: 86010fc7d3b17accc427c12f00606a0d1f4bbc70 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002 * 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>
Alexey Dobriyane8edc6e2007-05-21 01:22:52 +040027#include <linux/sched.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070028
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}