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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>
27
28/*
29 * Top of mmap area (just below the process stack).
30 *
31 * Leave an at least ~128 MB hole.
32 */
33#define MIN_GAP (128*1024*1024)
34#define MAX_GAP (TASK_SIZE/6*5)
35
36static inline unsigned long mmap_base(void)
37{
38 unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;
39
40 if (gap < MIN_GAP)
41 gap = MIN_GAP;
42 else if (gap > MAX_GAP)
43 gap = MAX_GAP;
44
45 return TASK_SIZE - (gap & PAGE_MASK);
46}
47
48static inline int mmap_is_legacy(void)
49{
50 /*
51 * Force standard allocation for 64 bit programs.
52 */
53 if (!test_thread_flag(TIF_32BIT))
54 return 1;
55
56 if (current->personality & ADDR_COMPAT_LAYOUT)
57 return 1;
58
59 if (current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY)
60 return 1;
61
62 return sysctl_legacy_va_layout;
63}
64
65/*
66 * This function, called very early during the creation of a new
67 * process VM image, sets up which VM layout function to use:
68 */
69void arch_pick_mmap_layout(struct mm_struct *mm)
70{
71 /*
72 * Fall back to the standard layout if the personality
73 * bit is set, or if the expected stack growth is unlimited:
74 */
75 if (mmap_is_legacy()) {
76 mm->mmap_base = TASK_UNMAPPED_BASE;
77 mm->get_unmapped_area = arch_get_unmapped_area;
78 mm->unmap_area = arch_unmap_area;
79 } else {
80 mm->mmap_base = mmap_base();
81 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
82 mm->unmap_area = arch_unmap_area_topdown;
83 }
84}